Search

The recent paper by Artüz & Fricke (2019) is focused on the analysis of marine teleost fishes of the Sea of Marmara, where they have tried to correct doubtful species occurrences and presented an annotated checklist. In a few cases, the authors have provided convincing data for the removal of some species from the regional inventory, such as Apogon imberbis (Linnaeus, 1758), Scomberesox saurus (Walbaum, 1792) and Polyprion americanus (Bloch & Schneider, 1801), and pointed out revision-seeking genera (i.e. Alosa spp., Pegusa spp., etc.), which should certainly be taken into consideration. However, the paper also raises several doubts resulting from mistranslations of some previous research, misinterpretation and incomplete examination of certain published biodiversity data related to the Sea of Marmara. Despite the authors presented a number of mistaken first record data (for example Sardinella aurita Valenciennes, 1837, for full account see Bilecenoglu et al. 2002), included some unsubstantiated/questionable species (such as Symphodus melops (Linnaeus, 1758), Gobius vittatus Vinciguerra, 1883, etc.), and unexpectedly neglected the occurrence of some common coastal and deepsea species from the area, such as Arnoglossus kessleri Schmidt, 1915, Gobius bucchichi Steindachner, 1870, Labrus merula Linnaeus, 1758, Parablennius zvonimiri (Kolombatović, 1892) and Argyropelecus hemigymnus Cocco, 1829, I herein concentrate solely on the erroneous/invalid records (totaling 42 fish species) with appropriate explanations.

The presence of nitric oxide synthase (NOS) and nerve fibres in the photophores of seven bioluminescent fish species (Hygophum benoiti, Myctophum punctatum, Electrona risso, Cyclothone braueri, Vinciguerria attenuata, Maurolicus muelleri and Porichthys notatus) with endogenous photocytes, were investigated. Antibodies directed against neuronal and inducible NOS (n and iNOS respectively) and NADPH-diaphorase activity were used to reveal the locations of NOS, while antibodies directed against acetylated tubulin were used to visualize nerve fibres. The nNOS antibody labelled structures in all investigated photophores except in the organs from P. notatus. The photocytes of P. notatus showed NADPH-diaph- orase activity. In the myctophid species, NOS-like immunoreactivity was found in small intracellular structures of the photocytes and in nerve fibres reaching the photocytes. nNOS-positive fibres were also found among lens ⁄ filter cells in V. attenuata, and in M. muelleri the cytoplasm of lens ⁄ filter cells contained NOS- like material. In C. braueri, a cell type located at a collecting chamber for lumi- nous products in the photophore contained NOS-like material. All photophores received an innervation reaching the photocytes, as well as other components including lens ⁄ filter areas. The results of this study comply with an involvement of nitric oxide in the control of bioluminescence in several fish species

The structure of the photophores (luminous organs) of two species of deep-sea fishes from the Strait of Messina, Argyropelecus hemigymnus and Maurolicus muelleri, was examined. Although significant structural differences were identified between species, especially in photophore organization and distribution, ultrastructural comparisons indicated a marked similarity between them. The photocytes exhibited numerous secretory granules, of different electron density, embedded in an extremely developed rough endoplasmic reticulum. Numerous mitochondria were observed among the secretory granules. The lens appeared to be composed of tightly contiguous polyhedral cells. The reflector was made up of cells rich in guanine crystals embedded in an amorphous matrix and appeared to be surrounded by a layer of connective tissue full of melanocytes. Ventrally, every photophore was delimited by a thick cellular layer called the ‘gelatinous layer’ with dioptric properties. The results confirm that even though A. hemigymnus and M. muelleri differ widely phylogenetically, they exhibit adaptive convergence, involving similar morphology and physiology in these luminous structures.

13 pages, 7 figures, 4 tables The present study analysed the trophic ecology of the early developmental stages of four species of mesopelagic fish, the myctophids Ceratoscopelus maderensis, Hygophum benoiti and Benthosema glaciale and the sternoptychid Argyropelecus hemigymnus. These species display different morphological traits and a segregated vertical distribution throughout the water column. The study was conducted off Mallorca Island (39° N, 3° E) in the western Mediterranean, during the summer stratification period. The results indicated that feeding patterns of myctophid larvae were strictly diurnal, while in A. hemigymnus larvae, day and night feeding occurred. In the transformation stage of C. maderensis, B. glaciale and A. hemigymnus, day and night feeding was evidenced. The feeding incidence during the larval stages was low, increasing in the transformation stages, and being particularly high for A. hemigymnus. Although an increasing tendency in size and number of ingested prey was observed, the trophic niche breadth did not indicate a trophic specialization in any of the species analysed. Gut content analysis determined that diet composition was very similar among the four species, with the different developmental stages of copepods being the dominant prey throughout the early larval development. Nevertheless, in transformation stages of C. maderensis and H. benoiti, other preys, like ostracods, become important contributors to the diet. Despite the important physical and biological structuring of the water column, no differences in feeding success were observed for larvae occurring in the layers of higher biological production This research was funded by project CTM2008-04489-C03

Special issue The wrapping up of the IDEADOS project: International Workshop on Environment, Ecosystems and Demersal Resources, and Fisheries.-- 12 pages, 12 figures, 2 tables, The diel vertical distribution of fish larvae off the Balearic Islands during late autumn and summer was analysed in relation to the environmental conditions. Four fixed sampling stations, located in the outer shelf and slope zones, were sampled during both the day and night by means of oblique hauls at different water depths. In autumn the first 60. m were characterised by vertical mixing and relatively higher fluorescence values, while summer was characterised by strong near-surface stratification and the presence of a Deep Fluorescence Maximum (DFM). The fish larval community was dominated by mesopelagic species, myctophiforms and stomiiforms, with some differences in species composition and their relative contribution between periods. A higher number of species was observed to reproduce in summer. The diel vertical distribution patterns differed among species and, within species, some differences were detected between the day and night. Although their relative depth preferences were similar between surveys, seasonal comparisons for the most abundant species showed that in autumn larvae presented both a shallower distribution during the day and a deeper distribution during the night than in the summer period. The larvae of all species, except for Argyropelecus hemigymnus, were absent from layers below 200. m. In these deeper layers, only A. hemigymnus larvae and juvenile stages of myctophiforms and stomiiforms were found. Another group of species, including Hygophum benoiti, Ceratoscopelus maderensis, Cyclothone braueri and Lampanyctus crocodilus, characterised the surface assemblage, mainly appearing in the first 50. m during the day, while at night their distribution was wider, extending to deeper layers. Benthosema glaciale, Symbolophorus veranyi and Myctophum punctatum were located at intermediate levels (mostly 50-100. m). Larval size stratification was evident for the most abundant species, with younger stages being found at shallower depths in the water column, while postflexion stages presented a wide distribution at night, undergoing vertical displacement to the near-surface layers during the day. The roles of the position of the thermocline, the availability of food and light intensity as factors modulating these differences are discussed. © 2013 Elsevier B.V., This research was funded by project CTM2008-04489-C03

Coelenterazine, a luciferine, and luciferase activity specific to coelenterazine were detected and assayed in various tissues of mid-water fishes, Argyropelecus hemigymnus, Chauliodus sloani, Myctophum punctatum, Vinciguerria attenuata and Cyclothone braueri. Coelenterazine was found mainly in digestive systems and photophores of these fishes, A large species to species variation was found: extremely high levels of coelenterazine and luciferase were found in the M. punctatum digestive system whereas only a very low level of coelenterazine was detected in C., braueri. Coelenterazine was detected in A. hemigymnus eggs supporting the hypothesis of a maternal transfer of luminous capabilities. Luciferase activity specific to coelenterazine was found in photophores as well as in various other tissues suggesting another (besides light emission) biological function for this enzymatic activity, Distribution of coelenterazine in all tissues of the individuals supports the hypothesis of the dietary acquisition of coelenterazine by these fishes.

We develop a model for mate location by olfaction and apply it to reproductive behavior in the deep-sea hetchetfish Argyropelecus hemigymnus. The model includes diffusion theory to model the geometry of the region of detectable pheromone around the female, kinetic theory to medel the motion of the males prior to detection of a pheromone field, and a Monte Carlo search routine to estimate the time to locate the female after detection. The model yields results that are consistent with our present understanding of the biology of A. hemigymnus. The success of olfactory communication systems is strongly dependent on diffusion velocity, which is a function of depth in the ocean. The receiving organism must have low detection thresholds and high dynamic sensitivity to changes in odor concentration to use olfaction effectively for long-range detection and location of advertising females. Olfaction appears to be critical to reproductive success and therefore viability for many dispersed and sparse populations livi...

Modifications in oxygen consumption and luminescence of isolated luminescent organs of the mesopelagic fish Argyropelecus hemigymnus following glucose and pyruvate administration were studied before and during light emission triggered by adrenaline. Isolated photophores (mean fresh weight 13.5 ± 0.9 mg) at rest, i.e., in the absence of light emission, in saline (20 °C) exhibit a respiration rate of 1.045 ± 0.082 (SE) nmol O2/min (n = 35). A significant decrease (p = 0.05) in oxygen consumption was observed after the addition of 5.5 mM glucose. Instead of the oxygen decrease usually observed as a result of control stimulations using adrenaline, photophores pretreated with glucose increased their oxygen uptake in response to adrenaline, and maximal light emission was reduced by 85% (p = 0.01). The addition of 5.5 mM pyruvate induced a significant transient increase (p = 0.05) in oxygen uptake of isolated photophores, though this treatment did not statistically modify the mean time course of oxygen consumption and light emission in response to adrenaline. The hypothesis of a hypometabolic state of the isolated photophores of A. hemigymnus during light emission is discussed.

SUMMARYNitric oxide synthase-like immunoreactivity (NOS-LI IR) was detected by immunohistochemistry in ventral light organs of the mesopelagic fish, Argyropelecus hemigymnus. Strong NOS-LI IR was present in nerve fibres and in other cells central for production or modulation of light:immunoreactive fibres surrounded the photophores, and were also present in the filter area. Filter cells, particularly in the outer layers, showed strong IR throughout the cytoplasm. Pharmacological studies suggested that nitric oxide(NO) modulates adrenaline-stimulated light emission, and that the modulation is correlated to the ability of the light organ to respond to adrenaline. Adrenaline is known to produce two different types of light response in isolated photophores from Argyropelecus: a slow, long-lasting, high intensity response, or a fast and weak response of short duration. Incubation of photophores in the NO donors sodium nitroprusside or S-nitroso-N-acetylpenicillamine prior to adrenaline stimulation reduced the intensity of the strong and long-lasting type of response, but had little or even a potentiating effect on the weakly responding photophores. Hydroxylamine, which is converted to NO if catalase activity is present in the tissue, reduced the duration and the intensity of the adrenaline response in all tested organs. The NOS-inhibitor l-thiocitrulline potentiated the adrenaline response in the weakly responding organs; the weaker the adrenaline effect, the stronger the potentiation caused by l-thiocitrulline. The strongly responding organs were instead inhibited by l-thiocitrulline. The results suggest that NO has an important role in the control of light emission from Argyropelecus hemigymnus photophores. The cGMP analogue dibutyryl cGMP, the guanylate cyclase inhibitor ODQ and the phosphodiesterase inhibitor pentoxiphylline had no effect, indicating that the NO effect does not involve cGMP.

The trophic interactions of species of fish of the continental slopes have not been investigated previously in detail. The present study examines the diets of the clupeoid, stomiatoid and salmonoid species occurring demersally and pelagically in the Rockall Trough to the west of Scotland and Ireland. Pelagic fish were collected between the surface and about 2 500-m depth between 1973 and 1978. Demersal fish were sampled at 250-m intervals of depths between 500- and 2 900-m depth during the years 1975 and 1981. Of the 28 species caught, 18 were strictly pelagic and dominated by the stomiatoids while five were strictly demersal. The remaining five species occurred in both the pelagic and demersal environment. The commonest clupeoid was Alepocephalus bairdii, which is a dominant species within the demersal fish associations at depths of 750 to 1 250m. This species, along with the deeper-living A. agassizi, and 3 other alepocephalid species feed primarily on benthopelagic prey but also exploit the epibenthos. The stomiatoid species, such as Cyclothone microdon, C. braueri, Maurolicus muelleri and Argyropelecus hemigymnus, dominate the associations of pelagic fish in the Trough. They feed on different proportions of ostracods, copepods and amphipods. Of the salmonoids, only Argentina silus and Bathylagus euryops occurred commonly and both feed on benthopelagic fauna, the latter at much greater depths than the former. The principal factor acting to prevent direct competition between species is the modal centres of bathymetric distribution of the species. Other contributing factors are briefly discussed.

Quantitative measurements have been made on the ultra-structure and capillary supply to the axial muscles of the mesopelagic hatchet fish Argyropelecus hemigymnus (Cocco, 1829). Fish were collected at Eastern North Atlantic Ocean Station 10244, 32°48′N; 31°15′W during November 1980, from a depth of 480 to 550 m. Mitochondria with densely packed cristae occupy 44.3% of slow-fibre volume. Each myofibril is in direct contact with a mitochondrion. Compared with other fishes studied, the capillary supply to A. hemigymnus slow fibres is poorly developed. The average number of capillaries per fibre is 0.9, such that each μm of capillary contact supplies 0.011 μm2 of fibre cross-sectional area. The capillary surface area (μm2) supplying 1 μm3 of slow-fibre mitochondria is 0.17 in anchovy (Engraulis encrasicolus), 0.14 in rat-fish (Chimaera monstrosa), 0.14 in tench (Tinca tinca), 0.16 in catfish (Clarias mossambica), and only 0.025 for A. hemigymnus. It is suggested that, relative to the former species, some modifications in factors determining tissue oxygenation (e.g. myoglobin concentrations, blood flow, perfusion distribution or haemoglobin) and/or mitochondrial respiration rate are required in order to match oxygen supply and demand to the slow muscle in A. hemigymnus.

Light irradiance was measured at 430, 470 and 500 nm aboard the mesoscaph “Forel” in the Strait of Messina from the surface to 550 m depth in May 1979. The underwater light regime is partly due to the downwelling residual sunlight and partly to bioluminescence. An intense bioluminescence is localized at about 450 m at midday and moves upwards in the evening to reach an area extending from 100 m depth to the surface late in the evening. Two types of luminescence were observed: one associated with luminescent organisms and another diffuse, probably due to bacteria. Three types of luminescent fish were recognized, namely Argyropelecus hemigymnus, myctophids and Cyclothone braueri, and their time and space distribution were studied. While myctophids were encountered from the surface (21:00 hrs) to 550 m depth (16:00 hrs), A. hemigymnus were only observed between 180 m (19:45 hrs) and 500 m (12:15 hrs), and C. braueri between 330 m (16:00 hrs) and 500 m (19:00 hrs). The results do not show a significant relation between the absolute ambient light intensity and the time or the depth where the fish were observed.

The relationship between the vertical distributions of euphausiids and fish and light intensity has been studied directly by using a photometer in conjunction with an acoustically controlled rectangular midwater trawl. Samples were taken at a position centered on 47°N; 17°W on 15 and 16 May 1978. Five species of euphausiid and six species of fish have been analysed, both groups contained migrant and non-migrant species. The population of each of these species occurred throughout a light regime spanning at least three orders of magnitude of intensity; none of them was restricted to, or followed, and isolume. There were no sexual or size differences in the distributions of the euphausiids, but the population of Argyropelecus hemigymnus was probably stratified during the day, with smaller individuals occurring shallower than large ones. The results are discussed in relation to previous observations and to the theories of photic regulation of distributions and migrations.