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Simple Summary: The diets of ornamental aquaculture and aquarium fish usually differ significantly from the diets and types of diets present in natural habitats. These differences can significantly affect the health and welfare of the reared animals. One popular group of aquarium fish is the Anabantoidei fish, which can breathe atmospheric air using an additional respiratory organ—the labyrinth. These fish are commonly bred for both ornamental and consumption purposes. The structure of the digestive system of labyrinth fish such as African bush fish (Ctenopoma acutirostre) and paradise fish (Macropodus opercularis) is currently not known. In the present experiment, the fishes were studied and characterized based on their morphological and histological body structures. The results obtained suggest that although both species are generally regarded as omnivorous, their digestive tract structures have some differences, including the structure of the mouth, mouth cavity and esophagus, which indicate that the African bush fish is much better adapted to carnivorous feeding than the paradise fish. The results obtained will enable better feeding strategies to be developed for these Anabantoidei, thus improving their health in both commercial and domestic breeding. Anabantidae is a large and diverse group of fish cultured both under aquaculture conditions and as a hobby. These fish share a common structural feature in the form of an additional respiratory organ. Despite the enormous availability of these fish worldwide, little is known about their feeding preferences in husbandry and their influence on homeostasis under both industrial and domestic conditions. This study describes, for the first time, the structure of the digestive tracts of two Anabantoidei fishes: African bush fish (Ctenopoma acutirostre) and paradise fish (Macropodus opercularis). The overall structure of the digestive tract and its histological structure were analyzed and compared in both fish species. Physiological predispositions indicated a predominance of omnivorous fish traits in M. opercularis in contrast to C. acutirostre, which has several morphological traits indicating greater adaptation to carnivory, particularly ichthyophagy. The results obtained will allow further research to be conducted in the future to optimize the nutrition and feeding of these fish and to develop appropriate dietary recommendations. [ABSTRACT FROM AUTHOR]

The Itezhi-tezhi Dam on the Kafue River in Zambia is a major capture fishery. However, the upstream reaches of the Kafue River receive effluents from copper mines. It was unclear whether fish health in the dam is adversely affected due to the mining effluents. We investigated the health status of fish in Itezhi-tezh Dam using a histology-based fish health assessment protocol with Oreochromis andersonii as a bioindicator. Fish were sampled in the Itezhi-tezh Dam and at a reference site further upstream on the Kafue River before it enters the mining region. Metal bioaccumulation, biometric indices and histological alterations in the gills, gonads, hearts, kidneys and livers were assessed. The findings revealed significantly higher copper and selenium sediment concentrations (p = 0.02843 and p = 0.02107 respectively), bioaccumulation of copper and selenium, and increased histological alterations in the gills, kidneys and livers of fish in the Itezhi-tezhi Dam. • Higher levels of metal pollution downstream of the mining region. • Metal bioaccumulation in fish muscle, particularly copper and selenium. • Histological alterations in Oreochromis andersonii downstream of the mining region. [ABSTRACT FROM AUTHOR]

New sustainable feed ingredients are a necessity for the salmon aquaculture industry. In this study, we examined the effect of pre-extrusion processing of two microalgae, Nannochloropsis oceanica and Tetraselmis sp., on the growth, fatty acid content in the flesh and health of Atlantic salmon. The fish were fed one of the following five diets for nine weeks: (1) CO: a fish meal-based control (basal) diet, (2) NU: a Nannochloropsis diet, (3) NE: a pre-extruded Nannochloropsis diet, (4) TU: a Tetraselmis diet, and (5) TE: a pre-extruded Tetraselmis diet. The algae-incorporated diets contained 30% of the respective microalgae. Our results showed that the best growth performance was achieved by the CO diet, followed by the NE diets. Feeding of unprocessed Nannochloropsis and Tetraselmis resulted in a significant reduction in enterocyte vacuolization compared to the CO feeding. A significant effect of processing was noted in the fillet fatty acid content, the intestine and liver structure and the expression of selected genes in the liver. The expression of antioxidant genes in both the liver and intestine, and the accumulation of different fatty acids in the fillet and liver of the extruded algae-fed groups, warrants further investigation. In conclusion, based on the short-term study, 30% inclusion of the microalgae Nannochloropsis oceanica and Tetraselmis sp. can be considered in Atlantic salmon feeds. [ABSTRACT FROM AUTHOR]

The teleostean immune system is variable between and within taxa in terms of morphology. Accordingly, in the current study, the histology of some immune organs (thymus, kidney and spleen) of Lake Van fish (Alburnus tarichi) was investigated. For this purpose, the tissues from eight mature fish were fixed and embedded in paraffin wax, and then the sections were stained with haematoxylin and eosin, Mallory's triple, periodic acid‐Schiff and Alcian blue (pH of 2.5) for histologic examinations. In the thymus, no clear discrimination of the cortex and medulla was observed. Lymphoid cells within a reticulo‐epithelial network were the predominant cell type in the thymus. The other components in the thymus were macrophages and myoid, mast‐like, plasma‐like, cystic cells, Hassall's corpuscles, and single or multiple epithelial cystic structures. In the kidney, the head kidney, a major haematopoietic site, consisted of lymphoid and non‐lymphoid zones within a reticular network. Cells exhibiting mitotic figures were also detected in the haematopoietic tissue of the head kidney. Haematopoietic tissue was also found in the trunk kidney dispersed amongst the excretory components. The spleen was composed of red and white pulp. The red pulp comprised abundant erythrocytes, whilst the white pulp contained leucocytes with a reticular network. Ellipsoids were also determined in the white pulp. Melanomacrophage centres were found in all of the examined lymphoid tissues of the fish. These findings, which were reported, herein, for the first time will provide reference knowledge for future studies of this anadromous fish. [ABSTRACT FROM AUTHOR]

The collection and presentation of accurate reproductive data from wild fish has historically been somewhat problematic, especially for serially spawning species. Therefore, the aim of the current study was to develop a novel method of assessing female spawning status that is robust to variation in oocyte dynamics between specimens. Atlantic cod (Barents Sea stock) were used to develop the new 'ultrametric' method, that is based on the progressive depletion of the vitellogenic oocyte pool relative to the rather constant previtellogenic oocyte (PVO) pool. Fish were subsequently partitioned into one of four categories that accurately reflected changes in their oocyte size frequency distribution characteristics and gonadosomatic index throughout spawning. The ultrametric method overcomes difficulties associated with presence of bimodal oocyte distributions, oocyte tails, lack of clear hiatus region, and presence of free ova, and can be implemented at a single sampling point. Much of the workflow is fully automated, and the technique may circumvent the need for histological analysis depending on the desired outcome. The ultrametric method differs from the traditional autodiametric method in that PVOs can be separated by ultrasonication and then enumerated, and ovarian homogeneity is not a mandatory requirement per se. The method is designed for determinate spawners but might be extended to include indeterminate spawners. [ABSTRACT FROM AUTHOR]

Abstract Roundup formulations are herbicides whose active principle is glyphosate. However, these formulations are potentially more toxic to non-target organisms than pure glyphosate. This study aimed to evaluate and compare the toxic potential of the Roundup formulations through histological alterations in fish. Thus, males and females of the neotropical fish species Jenynsia multidentata (Jenyns, 1842) were exposed for 24 or 96 h to the Roundup Original® (RO), Roundup Transorb® (RT) or Roundup WG® (RWG) formulations, at a fixed concentration of 0.5 mg/L of glyphosate. This concentration is close to the maximum glyphosate limits found in the environment and is non-lethal to J. multidentata. The three formulations caused histological damage to the liver, gills and brain of J. multidentata , which increased over the exposure time. Differences in the histological alterations between females and males were observed in the liver and brain. Females were more tolerant to RO and RT than RWG. Males did not exhibit these differences in sensitiveness with formulations. The RWG caused more damage in the liver and gills and RT in the brain. Overall, there were differences in the toxicity of RO, RT and RWG and the toxic effect was presented through histological damage, reinforcing the usefulness of histological biomarkers for Roundup® toxicity. The comparison of the toxic potential of glyphosate-based herbicides is important because it could give support to the governmental organizations to set protective rules for the water ecosystems and human health, as well as to reduce the use of highly toxic formulations in agriculture. Graphical abstract HOMO and LUMO of Schiff base ligand HL. Image 1 Highlights • Effects of Roundup exposure were evaluated in the fish Jenynsia multidentata. • Roundup causes histological damages in liver, gills and brain of J. multidentata. • Toxicity vary between formulations of glyphosate, gender and exposure time. [ABSTRACT FROM AUTHOR]

Hermaphroditic gonads were collected from three skipjack tuna Katsuwonus pelamis in the western and central Pacific Ocean. Both ovarian and testicular tissues were found in the same gonad lobe for each of the three fish. Histological sections of the hermaphroditic gonad from one K. pelamis showed postovulatory follicles, which is evidence of spawning. [ABSTRACT FROM AUTHOR]

We describe the anatomy and histology of the accessory electric organs of several knifefish taxa. Accessory electric organs are observed among Rhamphichthyoidea in the opercular, mental and humeral regions. Within this group, some species of Brachyhypopomus possess an accessory electric organ in the opercular region. Rhamphichthyinae and Steatogenys possess accessory electric organs in the mental region of the body that differs in many aspects, such as general electrocyte shape and its number of caudal ridges. Steatogenys, Hypopygus and Rhamphichthys possess an accessory electric organ in the humeral region that differs in position, electrocyte configuration and shape. Electrocytes of both humeral and mental accessory electric organs in Steatogenys share a number of common features (e.g., electrocyte shape and innervation pattern), which distinguishes them from the electric organs of related groups. Rhamphichthys has an accessory electric organ in the humeral (specifically subpectoral) region, which has not previously been reported in the literature and differs in arrangement and electrocyte shape from those previously described electric organs of other taxa. Homology of these accessory electric organs is discussed in the context of hypothesized relationships among rhamphichthyoid taxa, indicating that accessory electric organs originated multiple times with apparently no subsequent losses. [ABSTRACT FROM AUTHOR]

Zebrafish has become a popular model organism in several lines of biological research sharing physiological, morphological and histological similarities with mammals. In fact, many human cytochrome P450 (CYP) enzymes have direct orthologs in zebrafish, suggesting that zebrafish xenobiotic metabolic profiles may be similar to those in mammals. The focus of the review is to analyse the studies that have evaluated the metabolite production in zebrafish over the years, either of the drugs themselves or xenobiotics in general (environmental pollutants, natural products, etc. ), bringing a vision of how these works were performed and comparing, where possible, with human metabolism. Early studies that observed metabolic production by zebrafish focused on environmental toxicology, and in recent years the main focus has been on toxicity screening of pharmaceuticals and drug candidates. Nevertheless, there is still a lack of standardization of the model and the knowledge of the extent of similarity with human metabolism. Zebrafish screenings are performed at different life stages, typically being carried out in adult fish through in vivo assays, followed by early larval stages and embryos. Studies comparing metabolism at the different zebrafish life stages are also common. As with any non-human model, the zebrafish presents similarities and differences in relation to the profile of generated metabolites compared to that observed in humans. Although more studies are still needed to assess the degree to which zebrafish metabolism can be compared to human metabolism, the facts presented indicate that the zebrafish is an excellent potential model for assessing xenobiotic metabolism. [ABSTRACT FROM AUTHOR]

In a parasitological survey of freshwater fishes near Meerut, Uttar Pradesh, India, myxozoan infections in Pabdah catfish Ompok pabda Ham. (Siluriformes: Siluridae) were found. Round plasmodia and scattered spores of Myxobolus ompok n. sp. were found in the kidney of the host. Plasmodia measuring 150-200 μm were located in the renal interstitium. Spores of Myxobolus ompok n. sp. were elongated pyriform, 13.6-14.4 (14.8 ± 0.42) μm long, 5.6-6.4 (6.5 ± 0.33) μm wide, and 5.2-6.4 (5.9 ± 0.43) μm thick with two equal polar capsules measuring 8.0-8.5 (8.2 ± 0.2) μm in length and 1.5-2.4 (1.8 ± 0.33) in width having six filamental turns. Both the morphology and DNA analysis of the 18S rRNA gene revealed that Myxobolus ompok n. sp. is distinct from previously described species of Myxobolus and shares no significant similarity with any other Myxobolus deposited in the GenBank database. Phylogenetic analysis inferred that this species showed the closest similarity to Myxobolus miyarii (KT001495). This is the first record of any Myxobolus sp. from O. pabda in India. [ABSTRACT FROM AUTHOR]

Fish samples of Indian hill trout Barilius bendelisis, were collected from the Gaula river (29° 17' 25'' N Latitude, 79° 32' 143'' E) and reared in captive condition at Directorate of Coldwater Fisheries Research, Bhimtal (29°21´ N, 79034´ E, altitude 1370 m MSL).Gonadosomatic index was found maximum in May for females (13.24 ± 0.92) and males (1.13 ± 0.07) respectively indicating a single spawning period of this species under captivity. Absolute fecundity (total number of eggs) varied from 320 to 4000. The average absolute fecundity was 1661 ± 304.6 at a total length 10.07 ± 0.30 cm and body weight of 11.92 ± 1.23 g. Histological study of the ovary revealed the presence of oocytes at different stages of maturity with a maximum number of the mature oocytes during April to May. Results of the present investigation suggest that B. bendelisis belongs to a category of low fecund fish and spawns during April and May under captive condition [ABSTRACT FROM AUTHOR]

The melanization of shrimp spermatophores caused by a hemocytic infiltration was demonstrated in this study. A 30-day trial was carried out using wild Farfantepenaeus brasiliensis . On days 0, 15 and 30, the spermatophores were manually extruded and used for sperm quality and histological analyses. Survival decreased after the extrusion events, whereas spermatophore melanization percentage increased. An inflammatory process characterized by the presence of hemocytes around and embedded in the connective tissue was identified as the trigger to the spermatophore melanization. The hemocytic infiltration was not observed in the sperm mass, but sperm quality was negatively affected. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the impact of plant-based diets supplemented with various levels of enzyme-treated soybean meal (ESBM) and squid products on the growth, proximate composition, serum biochemistry, and liver and intestinal histological alterations in pompano ( Trachinotus carolinus ). A 15% poultry by-product meal (PBM) based practical diet was used as a reference and basal diet was produced by replacing PBM with ESBM. Basal diet was then modified to contain varying levels of squid products. Squid hydrolysate (SH) and squid meal (SM) were added to basal diets, to produce diets containing 1, 2 and 4% of the squid products. A total of eight experimental diets were each fed to quadruplicate groups of 20 pompanos (mean initial wt = 7.68 ± 0.1 g) in a recirculating rearing system for 56 d. Results from the growth trial indicate that fish fed with basal diet exhibited significantly lower growth performance and feed utilization as compared to fish fed with PBM. The addition of 4% SH improved the response of basal diet and did not show any significant difference in terms of growth performance as compared to PBM. Whole body proximate and amino acids composition of fish were not significantly different among fish reared on any of the diets. Data on mineral composition of fish showed that the content of phosphorus and calcium were significantly higher in fish fed with basal diet compared to other treatments. Total protein and cholesterol level of fish fed PBM were significantly lower compared to basal diet. Total albumin, alanine transaminase, aspartate transaminase, and bile acids were similar among the dietary treatments. Fish fed with basal diet showed disordered vacuolization in the liver and decreased the lamina propria thickness in the intestine. The inclusion of 4% SH partly prevented the alteration of liver and distal intestine of Florida pompano and findings were similar to fish fed with PBM. Based on these results, combination of ESBM and 4% SH has the potential to serve as an alternative protein source and attractant to improve the efficacy of plant-based diet for pompano. [ABSTRACT FROM AUTHOR]

The aims of this study were to determine the most suitable site and the histological responses to passive integrated transponder (PIT) tags inserted into three sites in far eastern catfish, Silurus asotus . During the experimental period, the tag retention rate and readability rate were greater for dorsal tags than for abdominal cavity or tail tags ( P < 0.05). The standard length, body weight, growth rate (GRW), condition factor (CF), and specific growth rate (SGR) were not significantly different among the experimental groups (all P > 0.05). GRW and SGR were lower in the winter than in the other season ( P < 0.05). In fish with abdominal tags, the tag was located in abdominal fat (in 60% of fish), around the kidney (15%), outside the air bladder (15%), or inside the air bladder (10%). Fibroblasts and a fibrous capsule were found in the tag site, but not in the epidermis. Melanopores and mucous cells were only found in the epidermis, and the area of mucous cells was larger than that of other cells in the epidermis. Based on the high rates of tag retention, readability, and survival, our results suggest that the dorsal muscle is the most favorable tag site for selective breeding systems of far eastern catfish. [ABSTRACT FROM AUTHOR]

Antiretroviral drugs (ARVs) are hazardous therapeutic pharmaceuticals present in South African surface water. Efavirenz is an ARV commonly used in human immunodeficiency virus (HIV) treatment in South Africa. Although little is known about the toxic effects of efavirenz on fish health, threats of toxicity to the aquatic environment have been reported. Oreochromis mossambicus were exposed under controlled conditions to environmentally-relevant efavirenz concentrations (10.3 ng/l) as measured in rivers that flow into the Nandoni Dam in the Vhembe District, South Africa. Acute (96 h) exposures were conducted using efavirenz concentrations of 10.3 ng/l and 20.6 ng/l. The overall health of exposed fish was determined using a histology-based fish health assessment index. Necropsies and haematology were conducted and somatic indices calculated after which the liver, kidney, heart, gills and gonads were microscopically quantitatively assessed. Results indicated that fish exposed to 20.6 ng/l efavirenz had significantly (p < 0.02) higher liver indices than the control fish, indicating increased liver damage including steatosis and frank necrosis. Fish exposed to 20.6 ng/l efavirenz presented with significantly (p < 0.02) higher total fish indices, representative of declined overall health compared to control fish. It was concluded that the exposure of O. mossambicus to efavirenz resulted in liver damage and overall decline in fish health. These novel findings may indicate a health risk for O. mossambicus and other biota exposed to efavirenz in aquatic ecosystems. Thus, ARV’s in water sources of South Africa pose a definite threat to wildlife and ultimately human health. [ABSTRACT FROM AUTHOR]

The thyroid is an endocrine gland, with an important role in fish growth, development and adaptation of larvae. The aim of this study was to describe the development of the thyroid gland and to determine the initial functional activity of thyroid gland and hormones in Acipenser gueldenstaedtii and A. stellatus larvae using immunohistochemistry. For this aim, fertilized eggs of two species were reared in a hatchery and larval samples were collected daily for 20 days post hatching (dph). For immunostaining, rabbit polyclonal primary antibodies for thyroglobulin and mouse monoclonal antibodies for thyroid transcription factor-1 ( TTF-1) were used. In histological analyses, it was observed that the first development of the thyroid gland in stellate sturgeon larvae occurs on the 3-4 dph and on the 4-5 dph in Russian sturgeon larvae in the ventral pharyngeal region of the fish. In the immunostaining analyses of 12-day-old stellate larvae and 19-day-old Russian sturgeon larvae, the thyroid follicles showed dispersion in great numbers around the aorta, and also it was observed that they were stained positively with antithyroglobulin staining, but the same sections gave negative results with TTF-1 staining. Also melanomacrophage centres, which are generally found in the haemopoietic tissues in some cases, were first observed around the thyroid follicles of sturgeon larvae. The results of this study revealed a similarity in the early thyroid gland development between two sturgeon species but using immunostaining methods, it was described that A. stellatus shows a faster functional development and earlier hormone production than A. gueldenstaedtii. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize histological changes during opercular osteogenesis in farmed gilthead sea bream Sparus aurata larvae from 7 to 69 days post hatching (dph) and compare normal osteogenesis with that of deformed opercles. Mild opercular deformities were first detected in 19 dph larvae by folding of the opercle's distal edge into the gill chamber. Here, the variation in the phenotype and the irregular bone structure at the curled part of the opercles is described and compared with the histology of normal opercles. Results indicated that deformed opercles still undergo bone growth with the addition of new matrix by osteoblasts at the opercular surface, especially at its edges. No significant difference was found in bone thickness between deformed and normal opercles. In addition to differences in bone architecture, differences in collagen fibre thickness between normal and deformed opercles were also found. [ABSTRACT FROM AUTHOR]

Methods are needed for monosex production of sablefish ( Anoplopoma fimbria ) to capitalize on superior growth of females relative to males. This study aimed to characterize the system of sex determination and establish methods for both direct and indirect feminization of sablefish. Juvenile sablefish ~ 40 mm fork length were fed diets containing 17β-estradiol (E2), 17α-methyltestosterone (MT), or ethanol vehicle alone (control) for 2 months and then divided into subgroups either shifted to the control diet (E2- and MT-short (S) duration treatments) or maintained on steroid-treated diets for an additional 2 months (E2- and MT-long (L) duration treatments). Fish were subsampled for gonadal histology at the midpoint and end of the dietary treatments and all remaining fish were individually tagged to monitor subsequent growth and gonadal development for 36 months (post-treatment time points of 0, 4, 16, 24, and 36 months). Control fish exhibited balanced (1:1) sex ratios. E2 treatment regardless of duration induced ovarian differentiation in 100% of the genotypic males (i.e., direct feminization), while only the MT-L treatment induced testicular differentiation in 100% of the genotypic females (i.e., generating “neomales”). A high proportion (89%) of MT-S genotypic females possessed intersex gonads, indicating short-term MT exposure was insufficient to induce complete sex reversal. Significant differences in sex-specific growth were apparent by 16 months post-treatment and associated with gonadal phenotype; sablefish with ovaries outgrew those with testes, regardless of genotypic sex. Fish from the E2-S and -L and MT-L treatment groups maintained their respective feminized and masculinized states after steroid withdrawal, although MT-S treated genotypic females tended to show further masculinization post-treatment. Upon reaching sexual maturity, control males and neomales were crossed with wild-caught female broodstock. Resultant embryos from control crosses were 54.6 ± 8.9% (mean ± SD) genotypic female, while those from neomale-female crosses were 100 ± 0.0% genotypic female. Following sex differentiation, gonadal histology demonstrated that offspring from control crosses had a balanced phenotypic sex ratio, whereas all neomale offspring developed normal ovaries. This study establishes that sablefish utilize an XX/XY system of sex determination and methods for both direct and indirect monosex female production. [ABSTRACT FROM AUTHOR]

In addition to the increase in temperature occurring in the world's oceans, new evidences suggest a tendency for an increase in upwelling-favorable winds, bringing to surface cold and high p CO 2 corrosive waters. Changing temperature and p CO 2 conditions may have significant implications for the shellfish farming socio-ecological system. In order, to setup the basis for understand the impact of both environmental variables, in this study, we investigated the combined effects of changing temperature and p CO 2 on the physiological rates and histopathology of scallops Argopecten purpuratus farmed in Tongoy Bay, an area permanently influenced by coastal upwelling. Juvenile scallops were reared at two p CO 2 levels (400 and 1000 μatm) and two temperatures (14 and 18 °C). After 18 d of experimental exposure, growth, metabolic and clearance rates increased significantly at high temperature but independent of p CO 2 level, indicating a positive effect of warming on the physiological processes associated with energy acquisition. However, ingestion rates of scallops showed a synergistic interactive effect when exposed to both stressors. Increased p CO 2 also impacts the health of A. purpuratus through atrophy in the digestive gland. These results suggest that, the presence of trade-offs in energy allocation during upwelling-induced stress (low temperature and high p CO 2 ) can impact growth, metabolism, ingestion rates and health status of scallops cultured in Tongoy Bay. But, less severe response to high p CO 2 levels, suggest that natural variability in upwelling areas may promote acclimation and adaptation potential in this farmed scallops. [ABSTRACT FROM AUTHOR]

A pilot investigation was conducted in 2014 in the Sanyati Basin of Lake Kariba to ascertain whether long-term DDT spraying in the Kariba catchment had a negative effect on fish health. The aim was to assess the health of tigerfish,Hydrocynus vittatus,by means of histological analysis and to analyse water, sediment and tissue samples for bioaccumulated levels of chlorinated pesticides, including DDT. Eighteen tigerfish were collected by seine netting along the north-eastern shoreline of the Sanyati Basin in April 2014 and samples of their gill, liver, kidney, muscle and brain tissue were processed for histology and assessed using light microscopy. No detectable levels of DDT and/or its metabolites were found in the water or sediment samples and only a low concentration ofp,p′-DDE in fish tissues. No major histological alterations were observed in the fish tissues. Consequently, there seems to be no risk of DDT exposure following the consumption of tigerfish from the Sanyati Basin of Lake Kariba. These results were unexpected, given the historical use of DDT within the current study area. It is recommended that these findings be compared with those from other regions of Lake Kariba. [ABSTRACT FROM PUBLISHER]

This study evaluated the reproductive characteristics of pike-characids, Boulengerella cuvieri, during the hydrological cycle in the Xingu River, eastern Amazon. The sex ratio was 1:1 and the gonado-somatic index and relative frequency of maturation stages indicate a short breeding season of single phase spawning that coincides with a filling and flood period. Mean standard length at first sexual maturity for female B. cuvieri was estimated to be 22·9 cm. [ABSTRACT FROM AUTHOR]

The comparative morphology of the scales of roundscale spearfish Tetrapturus georgii and white marlin Kajikia albida was investigated. In addition, variation in scale morphology across different body regions within each species was analysed. Although considerable morphological variation was observed among scales from different body regions in both species, scales of K. albida generally have pointed anterior ends, fewer posterior points and are more heavily imbricated than those of T. georgii, which are frequently rounded anteriorly, often have many posterior points and are separated farther within the skin. In all sampled body regions and individuals, scales of T. georgii are significantly broader and have a lower length-to-width aspect ratio than those of K. albida. Superficial to the scales are denticular plates, which are ossified formations occurring on the surface layer of the epidermis; these were observed and described for T. georgii, K. albida and blue marlin Makaira nigricans. Detailed scale descriptions allow for a more accurate characterization of the variation within and differences between these two species and could potentially be a valuable tool for investigating istiophorid systematics. [ABSTRACT FROM AUTHOR]

Presence of bisexual individuals and a sex-specific bimodal size distribution are suggestive of protogyny in the dash-and-dot goatfish Parupeneus barberinus, but the most parsimonious interpretation of histological analysis is juvenile hermaphroditism. This is the first report of hermaphroditism in the Mullidae. [ABSTRACT FROM AUTHOR]

Samples of the shovelnose guitarfish Pseudobatos productus were collected on board a vessel and at landings of artisanal commercial fisheries in the Gulf of California from May 2004 to June 2007. Samples of 650 females, 2047 embryos and 484 uterine eggs were examined. The reproductive cycle is annual, ovulation and parturition occur in July, the uterine eggs are in diapause for 9 months (July-March) before an accelerated growth of embryos of 3 months. Histological analyses of the uterine wall of pregnant females suggested that no secretions were used for embryo nourishment. The standard percentage of water content was 48·6% in fertilized eggs and 80·75% in full-term embryos. Dry mass loss during embryonic development was 16·3% and the chemical balance of development was 0·84. This indicates that P. productus is a strictly lecithotrophic, viviparous species, that makes no maternal contribution of nutrients during embryonic development. [ABSTRACT FROM AUTHOR]

The objectives of this study were to characterize relationships between water and paddlefish Polyodon spathula dentary Sr:Ca, δ 18O and stable hydrogen isotope ratio ( δ D) to determine the accuracy with which individual P. spathula could be assigned to their collection locations using dentary-edge Sr:Ca, δ D and δ 18O. A laboratory experiment was also conducted to determine whether dentary Sr:Ca in age 0 year P. spathula would reflect shifts in water Sr:Ca to which fish were exposed. Significant linear relationships between water and dentary Sr:Ca, δ D and δ 18O were observed, although the relationship between water and dentary δ 18O was weaker than those for Sr:Ca and δ D. Classification success for individual fish to collection locations that differed in water Sr:Ca, δ D and δ 18O ranged from 86 to 100% based on dentary-edge Sr:Ca, δ D and δ 18O. Dentary Sr:Ca increased significantly in laboratory-reared age 0 year P. spathula following 4 weeks of exposure to elevated water Sr:Ca; dentary Sr:Ca of fish held in water with elevated Sr:Ca was also significantly higher than that of control fish reared in ambient laboratory water. Results indicated that P. spathula dentaries reflect water signatures for commonly-applied natural chemical markers and strongly suggest that dentary microchemistry and stable-isotopic compositions will be applicable for reconstructing P. spathula environmental history in locations where sufficient spatial differences in water chemistry occur. [ABSTRACT FROM AUTHOR]

This study inferred that the majority of shovelnose sturgeon Scaphirhynchus platorynchus captured in the upper Mississippi River probably originated from locations outside the upper Mississippi River (Missouri River, middle Mississippi River); whereas, lake sturgeon Acipenser fulvescens exhibit infrequent movement outside of the upper Mississippi River, but may move throughout these interconnected large rivers at various life stages. By using pectoral fin-ray microchemistry (a non-lethal alternative to using otoliths), it is suggest that interjurisdictional cooperation will probably be needed to ensure sustainability of the S. platorynchus commercial fishery and the success of A. fulvescens reintroduction in the upper Mississippi River. Additionally, fin-ray microchemistry can provide invaluable data to make informed management decisions regarding large river fishes, that cross jurisdictional boundaries or that move outside of closure zones, without causing further mortality to compromised fish populations ( e.g. threatened and endangered species). [ABSTRACT FROM AUTHOR]

The effect of rearing temperature on gonad differentiation and growth was evaluated in sea bass ( Dicentrarchus labrax ). One control group (CG, n = 60) and two experimental groups (EG1, n = 30; EG2, n = 30) were selected. CG was reared at 15.0 °C during 10 days post-hatch (dph) and at 19.0 °C throughout the remaining larval and post-larval development. EG1 was exposed to 14.5 °C from 1 to 50 dph, followed by an increase to 20 °C until sampling (176 dph). EG2 was exposed to 14.5 °C from 1 to 37 dph, followed by an increase to 20 °C until sampling (226 dph); 30 fish from CG were randomly sampled at 176 dph (CG1, control for EG1) and 30 fish were sampled at 226 dph (CG2, control for EG2). Weight, total and fork length measurement, and gonad collection were performed. All biometric indices were higher in EG1 and EG2 than in CG1 and CG2, respectively. Histologic analysis reported 100% of undifferentiated gonads in CG1 and; EG1 reported 80% of undifferentiated gonads and 20% of gonads at early differentiation toward the male line. CG2 reported 34% of undifferentiated gonads, 10% of gonads at early differentiation toward the female line, 23% of gonads at early differentiation toward the male line, and 33% of gonads with intratesticular oocytes. EG2 reported 47% of gonads differentiated in testis, 33% gonads differentiated in ovary, and 20% of gonads with intratesticular oocytes. These results suggest that water temperature plays an important role in the process of gonad differentiation and growth of sea bass. [ABSTRACT FROM AUTHOR]

In this study, gonadogenesis, the effect of temperature (15, 20 and 25 °C) on sex differentiation, and annual changes in the gonads of mature lake minnow Eupallasella percnurus (Pallas, 1814) were determined. The lake minnow was found to be a primary gonochoristic fish species, where gonads are formed directly in the ovaries or testes. The morphological differentiation of gonads was initiated 35 days post hatch (DPH) when two types of gonadal anlages were visible: a pear-shaped gonad attached by a single mesentery string and a spindle-shaped gonad attached on both sides to the peritoneum. Gonadogenesis occurred faster in females than in males, with the first previtellogenic oocytes and ovarian lamellae being already observed in 45 DPH fish. In males, cytological differentiation occurred approximately 85 DPH, when the fish reached an average body weight of more than 400 mg. No significant effect of rearing temperature on sex ratio in lake minnow juveniles was observed. The proportion of males and females was similar (close to 1:1) in all of the thermal-treated groups, although there were effects of temperature on the final sizes of fish. Histological examination of wild, mature lake minnow ovaries during the annual cycle (from May to February the following year) showed asynchronous oocyte maturation. The testes were characteristic of multi-batch spawning fish. Quantitative dominance of spermatids and mature spermatozoa in May was observed, while the presence of primary and secondary spermatocytes in all other periods was confirmed. These changes were also reflected in the seasonal variation in the gonado-somatic index in both sexes, with the highest mean values of 11.2% (females) and 4.0% (males) in May, which were found to be significantly different to all other periods. The data presented in this study provide an important contribution to our understanding of the biology and reproductive strategy of the endangered lake minnow. [ABSTRACT FROM AUTHOR]

The aim of this study was to check the suitability of using fatty acids of vegetable origin as biomarkers of aquafeed consumption in fish that aggregate around off-shore fish farms, analysing their different accumulation patterns and their persistence in different tissues in juveniles of Liza aurata (Risso, A. 1810. Ichthyologie de Nice ou histoire naturelle des poissons du de'partement des Alpes-Maritimes. Schoell, Paris. 344 pp.). Their natural diet was replaced by a commercial feed, followed by a return to the natural diet (wash-out period). The fatty acid profiles of flesh, liver, and brain were modified after 2 months of commercial feed consumption, while 2 months of the wash-out period were not sufficient to return to original values, the brain being particularly resilient in this respect. Histological examination of the liver showed no alterations of the lipid droplet distribution or fat content. The combined use of flesh and brain for fatty acid analysis can be recommended for tracking aquaculture waste intake in the form of lost pellets by wild fish. [ABSTRACT FROM AUTHOR]

Characidium is a Neotropical fish genus. Its distribution ranges from eastern Panama to northern Argentina, and it is an important component of the Neotropical ichthyofauna present in the major rivers of South America. We here provide an approximation to the dispersal and historical distributions of Characidium. The biogeographic history of five species of the genus was analyzed through nuclear RAG-2 and mitochondrial 16S genes and a time-calibrated phylogenetic analysis using three outgroup species. A biogeographical reconstruction was performed to estimate ancestral geographic ranges and infer the historical events that impacted the geographic distributions of Characidium species. Our results showed Characidium as a monophyletic group. The molecular clock suggests that the most recent common ancestor of Characidium originated during the Eocene, about 50.2 Mya. In addition, different dispersion and vicariance events could be inferred, which possibly gave rise to the present geographical distribution of the genus. Our results point to the rise of the Andean mountains and sea fluctuations as being important events in the formations and delimitation of different rivers, which influenced the distribution of South American ichthyofauna. [ABSTRACT FROM AUTHOR]

The structural characterization of the olfactory epithelium in Pygocentrus nattereri Kner, 1858 was studied with the help of light as well as scanning and transmission electron microscope. The oval shaped olfactory rosette consisted of 26-28 primary lamellae radiated from midline raphe. The olfactory epithelium of each lamella was well distributed by sensory and non-sensory epithelium. The sensory epithelium contained morphologically distinct ciliated and microvillous receptor cells, supporting cells and basal cells. The non-sensory epithelium was made up of labyrinth cells, mucous cells and stratified epithelial cells. According to TEM investigation elongated rod emerging out from dendrite end of the receptor cells in the free space. The dendrite process of microvillous receptor cells contained microvilli. The supporting cells had lobular nucleus with clearly seen electron dense nucleolus. The apex of the ciliated non-sensory cells was broad and provided with plenty of kinocilia. Basal cells provided with oval nucleus and contained small number of secretory granules. The mucous cells were restricted to the non-sensory areas and the nuclei situated basally and filled with about two-third of the vesicles. The functional significance of various cells lining the olfactory epithelium was discussed with mode of life and living of fish concerned. [ABSTRACT FROM AUTHOR]

The heart structure of the spotted scat, Scatophagus argus, was observed from the Paknam Pranburi Estuary, Thailand, using histological and histochemical techniques. The results revealed that the heart structure consisted of 4 chambers comprising the sinus venosus, the atrium, the ventricle, and the bulbus arteriosus which were basically structured into 3 layers (the epicardium, the myocardium, and the endocardium). The feature of the sinus venosus was structured similarly to the atrium. It had 2 layers which were a thin layer of the epicardium and the endocardium. However, the myocardium in the atrium had much more cardiac muscular tissue than was found in the sinus venosus. The ventricle in this species was thicker than that of the atrium and it was composed of the thickest layer of the cardiomyocytes. The localization of the bulbus arteriosus with the ventral aorta was the final observation of the heart organ and had a thicker layer of the myocardium than the other layers. [ABSTRACT FROM AUTHOR]

A multi-technique approach was used to study the changes occurring in European eel Anguilla anguilla ovaries during hormonally-induced vitellogenesis. Aside from classic techniques used to monitor the vitellogenic process, such as ovary histology, fat content analysis, sodium dodecyl sulphate-polyacrylamide gel electrophoresis ( SDS-PAGE) and vitellogenin enzyme linked immunosorbent assay ( ELISA), a new technique, Fourier-transform infrared ( FT-IR) microspectroscopy, was used to analyse A. anguilla ovaries. The results from the different techniques provided different ways of approaching the same process. Although it is considered a time consuming approach, of all the employed techniques, histology provided the most direct evidences about vitellogenesis. SDS-PAGE and ELISA were also useful for studying vitellogenesis, whereas fat analysis cannot be used for this purpose. The FT-IR analysis provided a representative IR spectrum for each ovarian stage (previtellogenic stage, early vitellogenic stage, mid-vitellogenic stage and late vitellogenic stage), demonstrating that it is a valid method able to illustrate the distribution of the oocytes within the ovary slices. The chemical maps obtained confirmed changes in lipid concentrations and revealed their distribution within the oocytes at different maturational stages. When the results and the accuracy of the FT-IR analysis were compared with those of the traditional techniques commonly used to establish the vitellogenic stage, it became evident that FT-IR is a useful and reliable tool, with many advantages, including the fact that it requires little biological material, the costs involved are low, analysis times are short and last but not least, the fact that it offers the possibility of simultaneously analysing various biocomponents of the same oocyte. [ABSTRACT FROM AUTHOR]

Ultrastructural and histological changes in the embryonic and larval surface during ontogenesis of the endangered golden mahseer Tor putitora is studied here for the first time. Embryonic development was completed 91-92 h after fertilization at an ambient temperature of 23° ± 1° C (mean ± s.d.). The gastrula stage was characterized by presence of the Kupffer's vesicle, notochord, ectoderm and endoderm cells. Primordial germ cells were clearly identifiable from c. 55 h post-fertilization at the organogenesis stage. Mean total length of newly hatched larvae was 7·0 ± 0·5 mm. Scanning electron microscopy of newly hatched larvae demonstrated vitelline arteries, microridged epithelial cells and mucous gland openings over much of the body surface. Eye, oral cavity, pharyngeal arches, heart, intestinal loop, prosencephalon, cephalic vesicle and nasal epithelium were clearly distinguished in 3 day old hatched individuals. In 6 day old individuals, caudal-fin rays and internal organs were evident. The dorsal fin became prominent at this stage and larvae began swimming at the surface. The reserved yolk material was totally absorbed 8-11 days after hatching and larvae began feeding exogenously. Tor putitora exhibited a longer early developmental period than other cyprinids reared at similar temperatures. [ABSTRACT FROM AUTHOR]

Understanding the influence of different temperature conditions on the spermatogenesis is important for improvement of the fish aquaculture. This study evaluated the influence of low temperature on structural and quantitative dynamics of the spermatogenesis in Oreochromis niloticus . Adult males were cultivated with room temperature water (20.28–22.46 °C) and testes were collected for histological, ultrastructural and morphometric analyses. This species has unrestricted lobular testis with cystic spermatogenesis and type I spermiogenesis that results in a single anacrosomal aquasperm. Seminiferous lobules and spermatogenic cells had a radial arrangement toward the spermatic duct. Superior and central portions of testes had a greater lobular area than the inferior portion in all samplings. Spermatogonia (9.3%) were distributed in the inferior portion of testes, spermatocytes (25.3%) and spermatids (34.4%) in the central portion, while spermatozoids (39.4%) and secretory cells (4.6%) in the superior portion. Throughout the study, correlation between water temperature and lobular area characteristics was significant only in the inferior portion of testes ( r 2 = 0.95), although the lobular area in the other testicular portions increased when the water temperature increased by 2 °C. Correlation between the water temperature and spermatogenic cells was significant for undifferentiated spermatogonia ( r 2 = 0.54) and number of spermatids ( r 2 = 0.67). It is concluded that low cultivation temperatures may positively influence the generation of primary spermatogonia in the inferior periphery of O. niloticus testes. In addition, males maintain reservoirs of germ cells at low temperatures and the radial zonation of spermatogenesis has an important role in the renewal and production of germ cells. [ABSTRACT FROM AUTHOR]

A detailed anatomy and histological structure of the brain and spinal cord, referring to the central nervous system and special sensory organ, in the short mackerel, Rastrelliger brachysoma, were observed in this study. All specimens revealed that the brain nomenclature in R. brachysoma anatomically consisted of the telencephalon, mesencephalon, diencephalon, metencephalon, and myelencephalon, continued by the spinal cord. Different structures and cell components were observed due to histology and histochemistry studies. The telencephalon of R. brachysoma was less developed, mainly consisting of olfactory lobes and cerebral hemispheres. The largest part, the optic lobe, in the mesencephalon, was observed to have 6 histologically distinct layers; the stratum marginale, stratum opticum, stratum fibroetgricialem, stratum album central, stratum griseum central, and stratum periventriculae, respectively. The diencephalon was situated beneath mesencephalon. The epithalamus, thalamus and hypothalamus were easily observable in this region. The cerebellum in the metencephalon was composed of the corpus and the valvula cerebelli. The last region of the brain was the myelencephalon, which held the medulla oblongata and vagal lobes, before joining the spinal cord. The eye structure, composed of the inner, middle, and external layers, was investigated. [ABSTRACT FROM AUTHOR]

Two essential metal contaminations were studied in a total of sixty silver pomfret Pampus argenteus samples. The purpose of the current study was to evaluate the levels of Zn and Cu in the muscle tissues of the commercial species P. argenteus in the fishing harbour of Karachi, the most important in Pakistan, and to correlate the concentration of metals with respect to fish size. Moreover, this study sought to establish the potential risk to humans from consumption of fish samples contaminated with these heavy metals. Zn concentrations in the silver pomfret were higher than Cu. The ranges of Zn and Cu concentrations were found to be from 2 to 12 and 1 to 6 mg/kg dry wt., respectively. The differences in both Zn and Cu concentrations between seasons were statistically significant. These results can be used to provide baseline information for risk assessment associated with their consumption, as the Estimated Daily Intake (EDI) for the fish tissues and Zn and Cu levels were below the daily dietary allowance recommended by international standards. Therefore, it may be concluded that these metals should not pose any health threat to the consumers resulting from the consumption of the fish. The relationship between Zn and Cu levels and fish size (both length and weight) of the fish were minimal, indicating that metal concentration in fish tissues was independent of lengths and weights. [ABSTRACT FROM AUTHOR]

Several tools can be used to evaluate the health status of fish. Histology is one of them because it assesses pathological changes induced by environment, pathogens and/or nutritional factors. The histological condition of macroscopically healthy turbot juveniles in the beginning of the growing phase in an intensive fish farm was evaluated. The gill, skin, liver, kidney and intestine were histologically processed by standard techniques and their histological status determined semi-quantitatively. The skin, the gills and the liver of examined turbot were in a good overall condition or presented slight alterations frequently observed in farmed fish. The kidney and the intestine of some fish presented pronounced histological alterations caused mainly by the occurrence of nephrocalcinosis in the kidney, and necrotic areas in intestinal lamina propria of the mucosa. The possible causes of these findings are discussed. Statement of relevance “This is a very first histology based survey conducted in an intensive farm to evaluate the health status of turbot juveniles. The results showed that i) the histological analysis is a useful tool for assessing the fish health and, ii) most of the fish were in good health condition” [ABSTRACT FROM AUTHOR]

Fungicides are a pesticide that particularly kills or destroy fungi responsible for several diseases associated to humans and other living organisms. Assessment of toxic effects and mechanisms of fungicide action is important because humans and domesticated animals get exposed to these pesticides through a wide variety of applications. Several fungicides are being used at the large scale for the crop protection from the fungal invasion. Propiconazole (PCZ), a trazole-containing fungicide, is widely used in China and various Asian countries for food crop protection which made it easily to exposed to the aquatic system. Long term usage of PCZ may contaminate the water bodies, but its toxicity to aquatic organisms is not well studied. In this study, freshwater fish, Channa punctata Bloch was exposed to different sub-lethal concentrations of the fungicide, PCZ (0.5 and 5 ppm) for a period of 96 h. Various biochemical assays and histological alterations were measured to determine the organ toxicity caused by PCZ exposure particularly in liver, kidney and gills of the fishes. Compared to the control group, fish exposed to PCZ (96 h) showed marked dose dependent toxicity. The levels of lipid peroxidation (LPO) and protein carbonyls (PC), oxidative stress biomarker of liver, kidney and gills in the experimental group were significantly higher ( P < 0.05 and P < 0.001) compared to the control group. Levels of reduced glutathione (GSH) and non-protein thiols (NP-SH) decreased significantly ( P <0.05–0.001) in all analyzed intoxicated organs of the PCZ exposed fishes. Activity of glutathione-S-transferase (GST), glutathione peroxidase (GPx) and catalase (CAT) in fungicide treated groups was significantly lowered ( P < 0.05–0.001). In addition, histopathological examination in the organs showed significant changes like atrophy of primary and secondary gill lamellae, infiltrations, inflammation, hepatocyte degeneration, vacuolization and necrotic kidney. Thus, PCZ exposure altered the oxidative stress homeostasis and brought about histopathological changes which may serve as potential biomarkers of the PCZ toxicity in the laboratory set-up for potential risk assessment. [ABSTRACT FROM AUTHOR]

The sexual maturation process and reproductive biology of female Arabesque greenling Pleurogrammus azonus in the Sea of Japan, off the west coast of Hokkaido, was examined using histological observations of ovaries. Maturation of P. azonus was classified into seven phases based on the presence of nine oocyte stages, post ovulatory follicles, and residual unspawned ova. Although vitellogenesis of P. azonus begins annually in August, hydrated oocytes were present in September and likely occurred several times during the spawning season until November. However, few oocytes at the intermediate stages of development were found during the premature and spawning phases. Based on these observations, the maturation pattern of female P. azonus can be classified as 'group-synchronous, spawning several batches in a single spawning season,' as in other hexagrammid fish. The probability of maturation of female P. azonus depended on body size rather than age. The estimated length at 50 % maturity was approximately 240 mm in standard length (SL). The mean SL of age-1 females just before the spawning season varied yearly around the 50 % maturity length. Overall, these findings suggest that the growth of female P. azonus before the spawning season at age 1 year can markedly affect spawning biomass. [ABSTRACT FROM AUTHOR]

Sturgeon is one of the endangered families of fish in the Caspian Sea region, where there is up to 80% of their global caching. Unfortunately, in recent years, increase of pollutants has been resulted in their total population reduction. Due to their benthic nature, sturgeons are at great risk of exposing to contaminants such as cadmium. Despite their endangered status in the Caspian Sea, there are only a few studies on characterizing the relative sensitivity of sturgeons to cadmium. Adverse effects associated with pollution on angiogenesis are mediated by hypoxia inducing factor-1 (HIF-1) and vascular endothelial growth factor (VEGF). In this investigation, gene expression of two distinct HIFs-1, HIF-1α and HIF-2α, and VEGF was investigated at the mRNA transcript levels after exposure of Persian sturgeon ( Acipenser persicus ) to cadmium. VEGF, HIF-1α and HIF-2α expressions in treated Persian sturgeon were greater than controls. Significant increases ( P < 0.05) were also observed in cortisol and glucose levels compared to the control group especially in the fish exposed to higher cadmium concentration (800 μg/L). Plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactic acid dehydrogenase (LDH) levels were increased in the cadmium-exposed fish, although the observed increases were not significant between the control and 200 μg/L cadmium treatment at some sampling time points. Gill tissues also showed histopathological changes in the cadmium treatments. Overall, results indicated that cadmium resulted in some alterations in biochemical parameters, mRNA transcript level expression of two important angiogenesis related genes as well as histological alterations in Persian sturgeon. [ABSTRACT FROM AUTHOR]

The first record of an ocular anomaly in Atlantic midshipman Porichthys plectrodon (Batrachoidiformes: Batrachoididae) is reported from a specimen captured in the Mississippi Canyon. The anomalous specimen was bilaterally anophthalmic and the nape and dorsum were darkly pigmented but alizarin staining and histology revealed a complete eye embedded within the cranium beneath a markedly thickened dermal component of the cornea, along with seemingly minor elaboration of the choroid rete between the cornea and lens. Aetiology is indeterminate and beyond the scope of the study materials but barotrauma, infectious disease and previous wounding are doubtful. [ABSTRACT FROM AUTHOR]

The extensive use of malathion, an organophosphate pesticide, raises the possibility of its undesirable toxicity to non-target organisms. Agricultural run-off and vector control sprays are the major sources of exposure to this pesticide for aquatic organisms. Some earlier studies have reported the presence of malathion at concentrations ranging from 18.12 μg/L to 105.2 μg/L in various water samples. In this study, we have tested the hypothesis that these sub-lethal yet environmentally significant concentrations of malathion has serious toxicological implications on the fingerlings of Labeo rohita. Exposure to increasing concentration of malathion (10, 50 and 100 μg/L) was reflected in the serum concentration of the pesticide and also in the inhibition of acetylcholinesterase activity in fish brains. Increased abnormalities in liver function test coupled with a rise in the oxidative stress response were observed in gills, liver and kidney. However, the increase in antioxidant enzyme activities like superoxide dismutase and glutathione-S-transferase by malathion exposure suggested a hormetic response. Tissue injury due to malathion was evident from the morphological and nuclear anomalies in the H-E stained sections of gill, liver and kidney. Cell cycle analysis of these organs further fortified the histopathological findings. This study elucidates the sub-lethal toxicity of environmentally relevant malathion concentrations on Labeo rohita which indicates the potential health hazard posed to human beings consuming this fish. This calls for careful application of malathion in areas adjoining to inland fisheries. [ABSTRACT FROM AUTHOR]

The jumbo squid Dosidicus gigas has been considered to be semelparous by several authors. However, to date no studies to support this assumption have been conducted. The present work tests the hypothesis that female jumbo squid do not die after a single reproductive event and provides evidence of the presence of postovulatory follicles (Pof) in females of different sizes. They indicates previous spawning in females in which they are present. Histological analysis was performed on reproductive structures of 73 female jumbo squid from the northwest of Mexico using hematoxylin-eosin staining. Using image analysis five ovarian stages were identified: (I) previtellogenesis, (II) vitellogenesis, (III) postvitellogenesis, (IV) spawning (in which 3.73% show atresia and the presence of Pof) and (V) Postspawning, in which a higher proportion (4.86%) show atresia and Pof. It is already known that the jumbo squid has asynchronic ovarian development with partial spawning during the reproductive period. However, the consistent presence of postovulatory follicles and the presence of oocytes of different sizes and development support the hypothesis that the jumbo squid is a multiple spawner with more than one reproductive event during its life cycle. [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the health status of farmed seabass ( Dicentrarchus labrax L.) using as a tool the histological semi-quantitative system proposed by Bernet et al. (1999). Gills, liver, kidney and intestine were fixed and processed for histological analysis using standard techniques. Organ index values were determined and used to classify the severity of histological response using classes based in the scoring scheme proposed by Zimmerli et al. (2007). The gills were the most histologically affected organ with 56.7% of the fish presenting severe histopathological alterations consisting mainly of hyperaemia, hypertrophy, hyperplasia and necrosis. The kidney was the organ which in most of the fish (58.6%) presented a normal tissue structure. Nevertheless hyperaemia, vacuolar degeneration of renal tubules, necrosis of the haematopoietic interstitial tissue and nephrocalcinosis were observed in some specimens. 71.4% of the fish showed normal or slightly modified liver but hyperaemia, high vacuolization and hypertrophy of hepatocytes were observed in some cases. In general the histology of the intestine was normal or presented slight enteritis. Statement of relevance The aim of the present study was to assess the health status of farmed seabass ( D. labrax L.) using as a tool a histological semi-quantitative system. This tool is being extensively used in wild fish to assess aquatic pollution but rarely applied in farmed fish. [ABSTRACT FROM AUTHOR]

Determining the earliest age at which farmed fish can be successfully vaccinated is a very important question for fish farmers. Nasal vaccines are novel mucosal vaccines that prevent aquatic infectious diseases of finfish. The present study investigates the ontogeny of the olfactory organ of rainbow trout by histology and aims to establish the earliest age for vaccination against infectious hematopoietic necrosis (IHN) and enteric red mouth (ERM) disease using the nasal route. Rainbow trout ( Oncorhynchus mykiss ) were vaccinated intranasally (I.N) at three different ages: 1050° days (DD) (group A); 450 DD (group B); and 360 DD (group C), or 70, 30 and 24 days post-hatch (dph), respectively. The mean weights of groups A, B and C were 4.69 g, 2.9 g and 2.37 g, respectively. Fish received either a live attenuated IHN virus vaccine, ERM formalin killed bacterin or saline (mock vaccinated). Fish were challenged to the corresponding live pathogen 28 days post-vaccination. IHN vaccine delivery at 360 DD resulted in 40% mortality likely due to residual virulence of the vaccine. No mortality was observed in the ERM nasal delivery groups. Following challenge, very high protection rates against IHN virus were recorded in all three age groups with survivals of 95%, 100% and 97.5% in groups A, B and C, respectively. Survival against ERM was 82.5%, 87.5% and 77.5% in groups A, B and C, respectively. Survival rates did not differ among ages for either vaccine. Our results indicate the feasibility and effectiveness of nasal vaccination as early as 360 DD and vaccination-related mortalities when a live attenuated viral vaccine was used in the youngest fish. [ABSTRACT FROM AUTHOR]

Le nerf terminal a été décrit récemment en détail chez les holocéphales. Cependant, cette étude portait uniquement sur deux espèces (Hydrolagus colliei et Chimaera monstrosa) de Chimeridae, la famille la plus dérivée parmi les holocéphales actuels. Nous complétons ici le précédent travail en décrivant, pour la première fois, le nerf terminal chez la chimère éléphant (Callorhinchus milii) dans son dernier stade ontogénétique, à partir de coupes sériées d'un spécimen. Le trajet du nerf terminal de C. milii ressemble à celui des autres holocéphales. Nous proposons que la position plutôt ventrale et médiane soit la condition de base pour les holocéphales actuels et peut-être pour les gnathostomes. [ABSTRACT FROM AUTHOR]

To understand how humans adapt to the space environment, many experiments can be conducted on astronauts as they work aboard the Space Shuttle or the International Space Station (ISS). We also need animal experiments that can apply to human models and help prevent or solve the health issues we face in space travel. The Japanese medaka (Oryzias latipes) is a suitable model fish for studying space adaptation as evidenced by adults of the species having mated successfully in space during 15 days of flight during the second International Microgravity Laboratory mission in 1994. The eggs laid by the fish developed normally and hatched as juveniles in space. In 2012, another space experiment (“Medaka Osteoclast”) was conducted. Six-week-old male and female Japanese medaka (Cab strain osteoblast transgenic fish) were maintained in the Aquatic Habitat system for two months in the ISS. Fish of the same strain and age were used as the ground controls. Six fish were fixed with paraformaldehyde or kept in RNA stabilization reagent (n = 4) and dissected for tissue sampling after being returned to the ground, so that several principal investigators working on the project could share samples. Histology indicated no significant changes except in the ovary. However, the RNA-seq analysis of 5345 genes from six tissues revealed highly tissue-specific space responsiveness after a two-month stay in the ISS. Similar responsiveness was observed among the brain and eye, ovary and testis, and the liver and intestine. Among these six tissues, the intestine showed the highest space response with 10 genes categorized as oxidation–reduction processes (gene ontogeny term GO:0055114), and the expression levels of choriogenin precursor genes were suppressed in the ovary. Eleven genes including klf9, klf13, odc1, hsp70 and hif3a were upregulated in more than four of the tissues examined, thus suggesting common immunoregulatory and stress responses during space adaptation. [ABSTRACT FROM AUTHOR]

The examination of the total length (L) vs. body mass (W) relationship in the blackmouth catshark from the southern Adriatic Sea showed the occurrence of two development phases or growth stanzas in females. The passage from the first stanza (Lrange: 22.8–37.4 cm) to the following one (Lrange: 39.7–51.4 cm) was marked by an inflection in the power equation correlating body mass to total length, occurring at about 38.6 cm of length (change point). After the change point, growth became positively allometric. This catshark is a lecitotrophic oviparous continuous spawner, and follicles in different stages of development are simultaneously present in the ovary. The histological analysis of the ovary showed that the smallest vitellogenic follicles were about 2 mm in diameter; the diameter of the largest observed oocyte was 18 mm. The change point occurred slightly before the onset of vitellogenesis (smallest vitellogenic femaleL = 41.0 cm) and appeared to be related to the activation of the reproductive axis. [ABSTRACT FROM AUTHOR]