Search

Abstract: Ultrastructural characteristics of late spermatids and spermatozoa during spermiogenesis in longtooth grouper Epinephelus bruneus from Jeju, Korea were investigated using transmission and scanning electron microscopy. The spermiogenesis type of E. bruneus belongs to type I because of nuclear rotation occurrence. The spherical head of late spermatids and spermatozoa ultrastructurally consist of apple-shaped nucleus, nuclear notch (Y or branch-shaped) and nuclear fossa. The midpiece contains the proximal centriole (9+0 microtubule structure), two centrioles connection structure (three osmophilic filaments), the distal centriole (9+0 microtubule structure), an osmophilic basal foot, two necklaces (six or seven osmophilic particles) and osmophilic alar sheets. It contains six to nine spherical mitochondria showing two rows arrangement type. Also a flagellum (9+2 microtubule structure) presents six swelling shaped segments type lateral fins with regular interval. Consequently, ultrastructural features of E. bruneus spermatids and spermatozoa contribute to provide useful systematic characters for taxonomic purpose. It may contribute to study that whether ultrastructural features of cellular organelles (cytoplasmic canal, necklace and lateral fins) correlate to physiological function or not on the duration of motility and survival in fish spermatozoa. [Copyright &y& Elsevier]

Abstract: The characteristics and distributions of cholecystokinin (CCK)-producing cells and mucus-secreting goblet cells were investigated in the digestive tract of the blacktip grouper (Epinephelus fasciatus). CCK-producing cells were scattered throughout the digestive tract. The highest frequency of CCK-producing cells was observed in the anterior intestine portion and pyloric ceca, with a very small number of cells distributed as far as the rectum. Mucus-secreting goblet cells were found to differ remarkably in their regional distributions and relative frequencies. High frequencies of mucus-secreting goblet cells were found in the digestive tract, mainly in the anterior intestine portion and pyloric ceca, but not the esophagus; the frequency decreased slightly toward the rectum. Our result suggests that food digested by gastric acid in the stomach moves on the anterior (including the pyloric ceca) and mid intestine portion, thereby ensuring effective stimulation of the CCK-producing cells. In addition, the distribution pattern of the CCK-producing cells closely resembled that of mucus-secreting goblet cells. In E. fasciatus, CCK-producing cells and mucus-secreting goblet cells seem to be well adapted to promoting optimal control of the digestive process. [Copyright &y& Elsevier]

Extrusion technology is known to enhance feed quality by controlling feed processing conditions. Although extrusion technology has been extensively used to improve livestock feed quality, research on its effects on quality in fish is lacking. Furthermore, studies on feed processing, the physical properties of feed produced using extruders, and the effects of extrusion on formulated feed quality remain scarce. Therefore, in this study, we investigated the effects of extrusion pressure and raw material particle size on the growth performance and digestive physiology of rockfish (Sebastes schlegeli). Experimental diets were prepared under different extrusion pressures by manipulating the screw speed [low pressure (LP), 1080 rpm/min; high pressure (HP), 620 rpm/min] and mean raw material particle sizes [small size (SS), 199.1 μm3; large size (LS), 1026.8 μm3] in a two-level factorial design. Four experimental diets (SS/LP, SS/HP, LS/LP, and LS/HP) were randomly assigned to 12 tanks (3 replicates), which were each stocked with 30 fish (initial mean body weight, 82.7 ± 0.2 g). After a 16-week feeding trial, observations showed that SS and LP enhanced fish weight gain and plasma growth-related hormone activity. In addition, SS and LP increased intestinal digestive activity in fish, positively affecting growth. These results indicate that manipulating physical pellet qualities by adjusting the feed ingredient extrusion pressure and raw material particle size can improve the growth performance and digestive physiology of rockfish, which should be considered in feed manufacturing. • Extrusion pressure and particle size improved rockfish growth rate and growth hormone activity. • Higher water absorption ability of feed was associated with better fish growth. • SS and LP enhanced fish weight gain and plasma growth-related hormone activity. • SS and LP increased the digestive activity of the intestines. [ABSTRACT FROM AUTHOR]

The effects of Bacillus sp. supplementation of different types of cells, such as spores and vegetative cells, on fish growth performance, intestinal microbial diversity alteration and immunity in juvenile olive flounder (Paralichthys olivaceus) were investigated. The fish were divided into three groups and provided with either a basal diet (control), Bacillus sp. vegetative cell (VCS) or spore (SS) supplemented diet for 8 weeks. At the end of the experiment, significant differences (P <.05) were found in terms of weight gain, specific growth rate, feed conversion ratio and protein efficiency ratio between the VCS and control groups. Respiratory burst, superoxide dismutase activity, and lysozyme activity, which are innate immune indicators, were observed with positive alterations (P <.05) in SS compared to controls. Intestinal microbial diversity analysis showed that the SS group had an increased richness estimate (Chao 1, ACE, and Jackknife) compared with the control group. Diversity estimates (Shannon and reverse Simpson) revealed that the VCS group was increased compared with the control group. Analyzing the similarity between groups through beta-diversity, Venn diagram, and heatmap analysis, the control and VCS groups were similar, and the SS group was different. IL-1β and TNF-α expression levels in the liver and spleen were increased in the SS group compared with the control group. In growth-related gene expression analysis, only growth hormone increased in the VCS group compared with the control group. In an in vivo challenge experiment with Streptococcus iniae (1 × 108 CFU/mL), the survival rates of the VCS and SS groups were 14.29% and 28.57%, respectively, when the control mortality reached 100%. Therefore, we concluded that supplementation of Bacillus sp. with different physiological processes affects the growth performance and immune activity of flounder. In particular, VCS can induce growth performance and growth-related gene expression, and SS can alter nonspecific immune and immune-related gene expressions. • The effect of dietary supplementation is affected by the Bacillus physiological process. • Dietary Bacillus vegetative cell supplementation improves growth performance. • Bacillus spore supplementation affects the intestinal microbial composition. • Nonspecific immunity is altered by Bacillus spore supplementation. • Pro-inflammatory cytokines are upregulated by dietary spore supplementation. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is known as a highly toxic heavy metal, and its toxicity varies depending on its form due to different toxicokinetics between inorganic and organic Hg. Limited information on comparison of Hg toxicity concerning its chemical form by oral exposure is currently available in cultured fishes. Therefore, we conducted a comparative study to have a better understanding of distinct toxic effects between mercuric chloride (HgCl 2) and methylmercury chloride (CH 3 HgCl) in Korean rockfish. The 12-weeks dietary exposure of HgCl 2 and CH 3 HgCl with its graded levels (0.4–6.4 ppm) (2 × 5 factorial design) in the young-of-the-year rockfish (initial weight: 82 ± 0.3 g) resulted in neither interactive nor main effects on whole-organism responses, including growth, feed utilization, and survival. However, the distinct pattern of Hg accumulation between the two forms in dorsal muscle, brain, liver and kidney tissues was observed, showing that the rockfish fed the CH 3 HgCl-contained diets exhibited the dose-dependent accumulation throughout the sampling points (1, 2, 4, 8, and 12 weeks post feeding), whereas those fed the HgCl 2 -contained diets did not show such response. The CH 3 HgCl exposure induced higher oxidative stress and immunotoxicity, reflected by the elevated plasma superoxide dismutase and lysozyme activities, respectively. In addition, the CH 3 HgCl-induced alteration in plasma measurements, including the plasma aspartate transaminase activity and total protein level was found. Taken together, the dietary exposure of methylmercury chloride had more pronounced toxic effects than mercuric chloride in the young-of-year rockfish, needed to be taken into consideration for regulation of maximum allowed levels for Hg by its chemical form. • Dietary-borne methylmercury chloride had higher toxicity than mercuric chloride. • Distinct toxicokinetics between the organic and inorganic mercury was found. • Immunotoxicity resulting from the methylmercury chloride exposure was detected. • Impaired liver function by the methylmercury chloride exposure was observed. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the effect of dietary differences on intestinal microbial population alteration and its relationship to immune-related gene expression in juvenile olive flounder (Paralichthys olivaceus). Initially, flounder were divided into three groups and supplemented with fishmeal diet (FM), fishmeal replaced by plant protein (termed low-fishmeal (LFM)), and Bacillus sp. SJ-10 probiotic-inoculated LFM (Pro) for 4 weeks. At the start (Initial group) and after completing the feeding trial, intestines were subjected to microbiota analysis and immune-related gene expression. The results of the intestinal microbiota analysis demonstrated that the FM and LFM groups' microbial richness (Chao1, ACE, and Jackknife) and diversity (Shannon and Simpson) did not differ significantly (P >.05) compared to the Initial group. However, the Pro group exhibited increased (P <.05) richness compared to all other groups, but its diversity was lower than that of the Initial group. A similar alteration phenomenon was also found in community composition between these two groups. At the phylum level, the most abundant phylum was Proteobacteria for all groups, but the second most abundant phylum in the Initial and Pro groups was Bacteroidetes, whereas in the FM and LFM groups, it was Firmicutes. An additional analysis of genus-level community composition and prediction of functional composition analysis showed differences among the groups. In the intestine, the transcription of interleukin (IL)-10 and IL-1β was increased more in the LFM and Pro groups compared to the FM group. IL-6 was increased only in the Pro group, and tumor necrosis factor-α (TNF-α) gene expression did not differ significantly among the groups. Therefore, we concluded that dietary changes affect intestinal microbiota composition and immune-related gene expression; in particular, diets containing probiotics can lead to greater change during the same feeding period. • Dietary changes affect intestinal microbiota composition and immune-related gene expression of olive flounder. • Probiotic have a greater impact on intestinal microbial diversity and composition than changes in fishmeal content. • Feed composition changes and probiotic supplements can manipulate the intestinal microbiota of olive flounder. [ABSTRACT FROM AUTHOR]