Croaker Larvae Research Articles

Dietary Allicin Improved the Survival and Growth of Large Yellow Croaker (Larimichthys crocea) Larvae via Promoting Intestinal Development, Alleviating Inflammation and Enhancing Appetite.

A 30-day feeding experiment was conducted to investigate effects of dietary allicin on survival, growth, antioxidant capacity, innate immunity and expression of inflammatory and appetite related genes in large yellow croaker larvae. Four iso-nitrogenous (53% crude protein) and iso-lipidic (19% crude lipid) diets were formulated via supplementing graded levels of allicin (0.0 (the control), 0.005, 0.01, and 0.02% dry diet, respectively). Results showed that, among dietary treatments, larvae fed the diet with 0.005% allicin had the highest survival rate (SR) (P < 0.05), while larvae fed the diet with 0.01% allicin had the highest specific growth rate (SGR) (P < 0.05). Activities of α-amylase in both pancreatic (PS) and intestine segments (IS) of larvae fed the diet with 0.01% allicin were significantly lower than that in the control (P < 0.05). On the other hand, the supplementation of 0.01% allicin in diets significantly increased activities of alkaline phosphatase (AKP) and leucine aminopeptidase (LAP) in the intestinal brush border membrane (BBM) of larvae than the control (P < 0.05), indicating the promoting roles of allicin on fish larval intestinal development. Moreover, compared to the control, both the nitric oxide (NO) content and the activity of nitric oxide synthase (NOS) were significantly up-regulated in larvae fed the diet with 0.005% allicin, and catalase (CAT) were significantly upregulated in larvae fed the diet with 0.02% allicin (P < 0.05). Transcriptional levels of pro-inflammatory genes including cyclooxygenase-2 (cox-2), interleukin-1β (il-1β) and interleukin-6 (il-6) significantly decreased with increasing allicin, compared to the control. The expression of appetite genes including npy, ghrelin and leptin significantly increased with the prolonged fasting period, and dietary allicin supplementation significantly increased the transcriptional level of neuropeptide Y (npy) at 0.01%, while increased the transcriptional level of leptin in larvae at 0.02% dosages (P < 0.05). These results showed that the supplementation of 0.005% – 0.01% allicin in diets could improve the survival and growth of large yellow croaker larvae probably by promoting intestinal development, alleviating inflammation and enhancing appetite.

Impacts of microdiet manufacturing technologies on the growth performance of large yellow croaker (Pseudosciaena crocea) larvae

Crumbled feed (CF) is the most commonly used microdiet in the weaning phrase of large yellow croaker (Pseudosciaena crocea) in China. However, CF can be inefficient for local hatcheries due to its low water stability. In this study, we evaluated a more water-stable microdiet (micro-extrusion marumerization diet or MM) in comparison to the CF, and ascertained their effects on the growth of larval croaker. Our results showed that the MM (ca. 98% dry weight retained) was much more water-stable than the CF (only 76% dry weight retained) after 5 min vigorous aeration. This was especially true for the preservation of lipid content, 40% of which was lost from the CF. The remaining intact structure and nearly unchanged nutritional composition of the MM enabled greater fish growth performance after a 24-day feeding trail, with 37% more dry weight gained than CF-fed larvae. Additionally, fish body compositions of each treatment directly reflected the nutritional profiles of each diet after aeration, and CF-fed fish had a significantly lower lipid content than those fed the MM (8.97 vs. 15.2%). Our results suggest that MM is a more suitable microdiet for the weaning phrase of croaker in hatcheries with vigorous aeration.

Effects of dietary Astragalus polysaccharides (APS) on survival, growth performance, activities of digestive enzyme, antioxidant responses and intestinal development of large yellow croaker (Larimichthys crocea) larvae

A 30-day feeding trial was conducted to investigate the effects of dietary Astragalus polysaccharides (APS) on survival, growth performance, activities of digestive enzyme, antioxidant responses and intestinal development of large yellow croaker (Larimichthys crocea) larvae. Five isonitrogenous (53% crude protein) and isolipidic (18% crude lipid) diets were formulated with graded levels of APS (0.00%, 0.05%, 0.10%, 0.15% and 0.20%). Results showed that larvae fed diets with 0.10% and 0.15% APS had significantly higher specific growth rate and body crude protein content. Meanwhile, larvae fed diets with 0.10% and 0.20% APS had significantly higher trypsin activity in intestinal segments (IS) at 45 days after hatch (DAH). Supplementation with 0.10% APS significantly improved the activity of alkaline phosphatase both in brush border membrane and IS of larvae at 45 DAH. Similarly, larvae fed the diet with 0.10% APS had significantly higher activity of leucine aminopeptidase in IS at 45 DAH than the control group. Also, larvae fed the diet with 0.10% APS showed significantly higher activity of superoxide dismutase in IS than the control group. Total antioxidant capacity in pancreatic segments (PS) were significantly higher in larvae fed diets with 0.15% and 0.20% than the control group. Malondialdehyde contents in PS were significantly lower in larvae fed the diet with 0.10% APS than the control group. Furthermore, supplementation of 0.10% APS significantly increased the length of intestinal microvillus and the height of enterocyte. The selected markers for intestinal epithelial proliferation and differentiation were higher expressed in larvae fed diets with APS than the control group, such as tight junction protein-2, proliferating cell nuclear antigen and sucrase-isomaltase. In conclusion, appropriate supplementation of APS (0.05% - 0.10%) could promote growth performance of large yellow croaker larvae through increasing the activities of digestive enzyme and antioxidant enzyme, improving intestinal morphology and promoting the intestinal development.

Specific visualization of live type A spermatogonia of Pacific bluefin tuna using fluorescent dye-conjugated antibodies†.

During our previous work toward establishing surrogate broodstock that can produce donor-derived gametes by germ cell transplantation, we found that only type A spermatogonia (ASGs) have the potency to colonize recipient gonads. Therefore, the ability to visualize ASGs specifically would allow the sequential analysis of donor cell behavior in the recipient gonads. Here we produced monoclonal antibodies that could recognize the cell surface antigens of ASGs in Pacific bluefin tuna (Thunnus orientalis), with the aim of visualizing live ASGs. We generated monoclonal antibodies by inoculating Pacific bluefin tuna testicular cells containing ASGs into mice and then screened them using cell-based enzyme-linked immunosorbent assay (ELISA), immunocytochemistry, flow cytometry (FCM), and immunohistochemistry, which resulted in the selection of two antibodies (Nos. 152 and 180) from a pool of 1152 antibodies. We directly labeled these antibodies with fluorescent dye, which allowed ASG-like cells to be visualized in a one-step procedure using immunocytochemistry. Molecular marker analyses against the FCM-sorted fluorescent cells confirmed that ASGs were highly enriched in the antibody-positive fraction. To evaluate the migratory capability of the ASGs, we transplanted visualized cells into the peritoneal cavity of nibe croaker (Nibea mitsukurii) larvae. This resulted in incorporated fluorescent cells labeled with antibody No. 152 being detected in the recipient gonads, suggesting that the visualized ASGs possessed migratory and incorporation capabilities. Thus, the donor germ cell visualization method that was developed in this study will facilitate and simplify Pacific bluefin tuna germ cell transplantation.

Vertical distribution of larval Atlantic menhaden (Brevoortia tyrannus) and Atlantic croaker (Micropogonias undulatus): Implications for vertical migratory behaviour and transport

AbstractUnderstanding the interactions among biological and physical processes is essential to determining how the environment affects transport and survival of fishes. We examined vertical distribution in larval Atlantic menhaden (Brevoortia tyrannus) and Atlantic croaker (Micropogonias undulatus) using 126 depth stratified tows in Delaware Bay, USA, during two cruises, in December 2007 and February 2008. Menhaden larvae were 16.8–24.6 and 20.5–26.2 mm standard length in December and February. Corresponding lengths for croaker were 9.3–17.9 and 8.6–19.6 mm. Using empirical observations, and statistically derived models, we explored larval concentration for both species as a function of location, depth, diel period, tidal period, size, and pairwise interactions. Menhaden concentration was best modeled as a function of station, cruise, and interactions between depth and size as well as between station and cruise. No significant differences in larval menhaden concentration were present among tidal and diel periods. Croaker concentration was best modeled as a function of size and interactions between station and diel period, depth and size, cruise and size. Despite tidal period not emerging as a significant model parameter, we observed larger croaker larvae during nighttime flood tides. Our statistical models are consistent with processes of up‐estuary transport for both species, suggesting larvae are increasingly affected by behavioral responses as larvae grow, exhibiting stronger patterns in vertical distribution. The results refine our understanding of the potential importance of size‐related differences in vertical distribution for larval transport in these species. Future research should examine the interactions among size‐specific vertical migratory capabilities, vertical distribution, transport, and retention.

Uso de la zona de rompiente de playas arenosas por larvas de corvina (Cynoscion spp.), Provincia del Guayas, Ecuador

The surf zone of sandy beaches exhibits high faunal diversity and can be a nursery habitat for fish and crustacean. Croakers ( Cynoscion spp.) are commercially and ecologically important euryhaline fishes whose larvae are found in the surf zone of sandy beaches; however, little is known about their biology. In this project, the use of surf zones was determined by studying the presence, density and growth of croaker larvae in an Ecuadorian surf zone adjacent to the largest estuarine system of western South America, and the relationship of these three factors with environmental variables explored. Fish larvae were collected during three days in the rainy season, using a hyperbenthic sledge and their otoliths analyzed. Croakers accounted for 58.6% of all larvae collected (mean density = 8.97 ± 10.17 ind 100 m -2 ). Size frequency distribution analysis (2.3 to 7.9 mm standard length, SL) resulted in a multimodal distribution, suggesting there were several cohorts of larvae that entered the surf zone and some inhabited the surf zone for several days. Recent larval growth rate (last three days) was 0.42 ± 0.12% SL day -1 and was positively related to water temperature, oxygen and croaker density, suggesting the number of croakers in the surf zone increased as growth conditions improved. Our study suggests that croaker larvae are the primary users of Ecuadorian surf zones adjacent to estuarine systems during the wet season, where they enter by pulses, attracted by better conditions for growth.

Effects of dietary phospholipid on lipase activity, antioxidant capacity and lipid metabolism-related gene expression in large yellow croaker larvae (Larimichthys crocea).

It was previously shown that lipid content of the whole larvae body fed the phospholipid (PL)-devoid diet was significantly lower than that of larvae fed PL-supplemented diets (P<0.05) (Feng et al., unpublished results). The mechanisms involved remain unclear and were explored from the perspective of fatty acids delivery, uptake, synthesis and oxidation in the present study. Besides, this study was also designed to investigate the effect of dietary PL on antioxidant capacity in large yellow croaker larvae (Larimichthys crocea). Triplicate groups of larvae (initial body weight: 3.86±0.24mg) were fed three isonitrogenous and isolipidic diets with increasing levels of PL (2.53%, 6.32% and 12.7%) eight times daily for 30days. Results showed that the specific activities of superoxide dismutase and catalase were significantly higher in 12.7% PL group compared to those in 2.53% PL group (P<0.05), while an opposite trend was observed for MDA content (P<0.05). The specific activity of lipase and the mRNA abundance of fatty acids delivery and uptake-related genes, including lipoprotein lipase, hepatic lipase and fatty acids translocase (cluster of differentiation) were significantly higher in 12.7% PL group than those in 2.52% group (P<0.05). Compared to 2.53% PL group, the transcript levels of fatty acid synthase and stearoyl-CoA desaturase I were significantly lower in 6.32% PL group (P<0.05), while peroxisome proliferators-activated receptor α, carnitine palmitoyl transferase-I and acyl CoA oxidase mRNA expression levels were significantly higher in 12.7% PL group (P<0.05). These results indicated that dietary PL could enhance antioxidant capacity of larvae. Dietary PL might regulate lipid metabolism in large yellow croaker larvae by modulating fatty acids delivery, uptake, synthesis and oxidation at transcriptional level and improved fatty acids delivery and uptake might be responsible for higher body lipid content in 6.32% and 12.7% groups.

Molecular cloning and genetic ontogeny of some key lipolytic enzymes in large yellow croaker larvae (Larimichthys croceaR.)

This study was conducted to investigate the genetic ontogeny of some key lipolytic enzymes in large yellow croaker Larimichthys crocea larvae. Partial cDNA sequences of bile activated lipase (BAL) and pancreatic enzyme secretory phospholipase A2 group IB (sPLA2 IB) were cloned and characterized. Real-time quantitative PCR (RT q-PCR) was conducted from 1 day after hatching (DAH) to 40 DAH in larvae fed the following sequence: rotifers, Artemia nauplii, copepods and then frozen copepods. In this study, 1181 bp and 205 bp partial cDNA sequences were cloned for BAL and sPLA2 IB respectively. The mRNA of all lipolytic enzymes were already present before mouth opening. The mRNA expression of BAL and sPLA2 IB during larval development showed a similar pattern: both of them increased gradually from 1 DAH to 25 DAH, followed by a slight decrease up to 40 DAH. The mRNA expression of lipoprotein lipase (LPL) also increased first and then decreased, peaked at 20 DAH. However, the mRNA expression of hepatic lipase (HL) increased constantly up to 40 DAH. These results suggest that the transcript levels of these enzymes were mainly regulated by age in early stage and by the exogenous diet in late stage of large yellow croaker larvae. Energy available for fish larvae, originating from lipid oxidation, may have been reduced as indicated by decreasing expression of LPL due to lower lipid levels in frozen copepods compared to fresh copepods. Besides, lipid hydrolysis for utilization in the liver of large yellow croaker larvae from chylomicron-remnant, very low density lipoprotein (VLDL)-remnant and high density lipoprotein increased along larval development of large yellow croaker which was reflected by the increasing concentration of HL mRNA.

Morphological and histological changes in digestive tract development during starvation in the miiuy croaker.

A histological method was used to describe the ontogenetic development of the digestive tract of laboratory-reared miiuy croaker (Miichthys miiuy) and to evaluate the effects of short-term food deprivation on the morphology and histology of the digestive tract. Larvae and juveniles were maintained at 24 °C in a thermostatically controlled system. Three starvation experiments were conducted during different developmental stages: 1-7 days after hatching (dah; prior to benthic swimming); 26-35 dah (during settling); and 42-53 dah (after benthic swimming). According to the structural changes in the ontogenetic development of the digestive tract, three stages were observed. The first stage was from hatching to 3 dah; the digestive tract was undifferentiated in newly hatched larvae and then showed remarkable morphological changes and differentiation. During this period, larvae depended on endogenous nutrition. The second stage (4-20 dah) was a critical period in which larvae transitioned from endogenous feeding to exogenous feeding and the digestive tract fully differentiated into the buccopharynx, oesophagus, stomach, anterior intestine and posterior intestine. Goblet cells and vacuoles appeared in the digestive tract, and pharyngeal teeth and taste buds developed. During the third stage (20-36 dah), the gastric glands developed and the stomach differentiated into the fundic, cardiac and pyloric regions. At 25 dah, pyloric caeca developed and mucosal folds and spiral valves were clearly distinguishable. After 30 dah, the digestive tract did not undergo any noticeable differentiation, indicating the complete development of the digestive system. The wet weight and SGR (specific growth rate) of miiuy croaker larvae and juveniles greatly decreased when they were deprived of food, and compensatory growth was observed in re-feeding juveniles. The livers of starved larvae and juveniles were atrophied and dark coloured, the intestines were transparent and thin, and the stomach cubages were reduced. The histological effects of starvation were mainly evident in the degeneration of cells in digestive organs, as seen in the shrinkage and separation of cells and the loss of intercellular substances in the liver, pancreas, intestine and stomach. These changes became more severe with increased duration of starvation. In addition, the histological structure of the digestive tracts of starved larvae and juveniles partly recovered after re-feeding, and the effects of starvation on miiuy croaker were age dependent.

Effects of dietary size-fractionated fish hydrolysates on growth, activities of digestive enzymes and aminotransferases and expression of some protein metabolism related genes in large yellow croaker (Larimichthys crocea) larvae

The present study was conducted to investigate the effects of size-fractionated fish hydrolysates on growth, activities of digestive enzymes and aminotransferases and expression of some protein metabolism related genes in large yellow croaker (Larimichthys crocea) larvae. Fish (initial body weight 3.15 ± 0.15 mg) were fed for 30 days with four diets: the control diet was produced using fish meal (FM) as the main protein source and other three diets were formulated with permeate after ultra-filtration of fish hydrolysate (PUFH), retentate after ultra-filtration of fish hydrolysate (RUFH) or non-ultrafiltered fish hydrolysate (NUFH) replacing approximately 40% FM. The results showed that specific growth rate and survival rate were significantly lower in fish fed diets with NUFH and RUFH than that of fish fed the control diet (P < 0.05) and there were no significant differences between PUFH-40 group and the control group (P > 0.05). Specific activities of digestive enzymes and the ratio “pancreatic enzyme in intestinal segment/pancreatic enzyme in pancreatic segment” were not significantly different between fish fed diets with PUFH and fish meal and they were both higher than that of fish fed diets with NUFH and RUFH (P < 0.05). Specific activities of both alanine and aspartate aminotransferases were significantly higher in fish fed the diet with PUFH than that of fish fed other diets (P < 0.05). Transcription of peptide transporter 1 (PepT1), cholecystokinin (CCK) and trypsin was significantly down-regulated in fish fed diets with NUFH and RUFH (P < 0.05). No significant differences were observed in the target of rapamycin (TOR) gene expression of fish among dietary treatments (P > 0.05). These results suggest that when replacing 40% FM, PUFH seems optimal for large yellow croaker larvae compared to NUFH and RUFH and size-fractionated fish hydrolysates could significantly affect digestion and absorption of protein in large yellow croaker larvae by altering the mRNA expression levels of CCK, PepT1 and trypsin.

Transgenic modification of the n-3 HUFA biosynthetic pathway in nibe croaker larvae: improved DPA (docosapentaenoic acid; 22:5n-3) production

Marine fish are generally unable to produce sufficient quantities of n-3 highly unsaturated fatty acid (n-3 HUFA) such as eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). Consequently, the seed production of marine fish requires careful nutritional enrichment of live feeds such as rotifers and brine shrimp Artemia to meet n-3 HUFA requirements for normal growth. Another strategy for improving n-3 HUFA availability is modifying the biosynthetic pathway of marine fish using transgenic technology. In this study, we conducted a feeding trial with non-transgenic and transgenic nibe croaker Nibea mitsukurii carrying the elongation of very long-chain fatty acids protein 2 (Elovl2) gene isolated from masu salmon Oncorhynchus masou and three groups of Artemia (non-enriched and enriched with two products). For all Artemia groups, docosapentaenoic acid (DPA, 22:5n-3), which is a direct product of Elovl2, was significantly higher in the transgenic fish than that in non-transgenic fish, despite the absence of DPA in all diets. Thus, applying transgenic techniques to marine fish at the larval stage are a powerful strategy for modifying n-3 HUFA biosynthetic pathways.

Effects of dietary phospholipids on survival, growth, digestive enzymes and stress resistance of large yellow croaker, Larmichthys crocea larvae

A 30-day feeding experiment was conducted in tanks to determine the effects of dietary phospholipids (PL) on survival, growth, digestive enzyme activity and stress resistance of Larmichthys crocea larvae (15days after hatching, initial average weight: 3.36±0.10mg, initial average body length: 6.15±0.71mm). Five practical microdiets were formulated with graded levels of PL (26.0gkg−1, 38.5gkg−1, 57.2gkg−1, 69.5gkg−1 and 85.1gkg−1 dry diet). Live prey (Artemia sinicia nauplii and copepods) were used as the control diet. Each diet was randomly assigned to triplicate groups of larvae (2500 larvae per tank). Results showed that the survival rate significantly increased as dietary PL increased from 26.0 to 57.2gkg−1 (P<0.05), and then decreased with further increase of dietary PL. The specific growth rate (SGR) of larvae fed the diet with 69.5gkg−1PL was significantly higher than that of larvae fed the diets with 26.0 and 38.5gkg−1PL. Selected digestive enzyme activities (trypsin, alkaline phosphatase and aminopeptidase) increased with increasing dietary PL. Stress resistance of larvae against declining water temperature and salinity alteration increased with dietary PL increasing from 26.0 to 69.5gkg−1 (P>0.05), significantly higher than that in the treatment of live prey (P<0.05). These results showed that relatively higher dietary PL (57.2–85.1gkg−1) could be beneficial for survival and growth performance of large yellow croaker larvae. Higher dietary PL (69.5–85.1gkg−1) could generally promote development of digestive tract and stress tolerance of this fish larvae.

Effects of dietary amino acid patterns on growth and protein metabolism of large yellow croaker (Larimichthys crocea) larvae

This study was conducted to evaluate the effects of dietary amino acids (AA) patterns on growth, survival, activities of digestive enzymes and aminotransferases and target of rapamycin (TOR) gene expression of large yellow croaker (Larimichthys crocea) larvae. The control diet was produced using intact protein as the only protein source. Four isonitrogenous and isolipidic semi-purified diets were formulated with crystalline-AA replacing approximately 40% fish meal protein-bound nitrogen. The AA patterns of these diets were adjusted according to the overall AA pattern of large yellow croaker egg protein (LEP), large yellow croaker larvae whole-body protein (LLP), large yellow croaker muscle protein (LMP) and white fishmeal protein (WFP), respectively. The test diets and live copepod were fed to triplicate groups of larvae (initial body weight 3.15±0.15mg) five times (6:00, 8:30, 12:30, 14:30, and 17:00) daily for 30days. The results showed that specific growth rate (SGR) of fish fed the WFP diet was significantly higher than LEP or LLP diet (P<0.05). At the end of the growth trial, there was no significant difference in survival rate among larvae fed LEP, LLP, WFP and the control diet (P>0.05), whereas the highest value was recorded in larvae fed the LLP diet, followed by WFP, the control, LEP and LMP diet, respectively. Whole-body crude protein content was significantly higher in larvae fed the WFP diet compared to the LEP or LLP diet (P<0.05). Larvae fed the live copepod had significantly higher whole-body crude protein and lipid contents than that in larvae fed artificial microdiets (P<0.05). Whole-body moisture content was not significantly affected by dietary treatments (P>0.05). The specific activities of digestive enzymes and the ratio “pancreatic enzyme in intestinal segment/pancreatic enzyme in pancreatic segment” were significantly higher in fish fed the WFP diet than fish fed LLP and LEP diet (P<0.05). Specific activities of alanine and aspartate aminotransferases were significantly higher in fish fed the WFP diet compared to the other treatments (P<0.05). No significant differences were observed in larvae body TOR gene expression among dietary treatments (P>0.05). Results of this study indicated that white fishmeal protein amino acid pattern was a more suitable amino acid pattern in diets of large yellow croaker larvae compared to the amino acid pattern of LEP, LLP, and LMP.

EVALUATION OF MICRODIETS AND FROZEN COPEPODS ON DIGESTIVE ENZYME ACTIVITIES, INTESTINAL AND LIVER MICROSTRUCTURES OF LARGE YELLOW CROAKER (PSEUDOSCIAENA CROCEA R.) LARVAE

A feeding trial was conducted to evaluate effects of three newly developed microdiets(MDs: Diet 1–Diet 3),a mixed diet(Diet 4: Diet 3 combined with frozen copepods) and frozen copepods(Diet 5,control) on digestive enzymatic activities,intestine and liver microstructures of large yellow croaker(Pseudosciaena crocea R.) larvae,which had an initial mean body weight of(13.80 ± 0.40) mg from 25 to 60 days after hatching(DAH).The results showed that trypsin activities exhibited no significant difference between fish fed with the MDs at 35 and 60 DAH,although those at 25 DAH showed lower trypsin activities,and there was no significant difference between fish fed with mixed diet and frozen copepods.No significant differences were observed between fish fed with the experimental diets except frozen copepods,the latter led to higher amylase activity at 35 DAH than at 25 and 60 DAH.As fish grew older,aminopeptidase N and alkaline phosphatase activities increased in fish fed with the experimental diets except for Diet 4 and Diet 5.No lipid droplets were observed in anterior–mediate intestinal mucosa in 35-day-old fish that were fed with the experimental diets with the exception of the Diet 4.Fish fed with the MDs presented deeper intestinal mucosa folds and supranuclear vacuoles in the rectum,while rectal folds from fish fed with the frozen copepods were nearly flat and lacked supranuclear vacuoles.Fish fed with the MDs displayed numerous lipid vacuoles in hepatocytes with nuclear migration.Liver from fish fed with the mixed diet had numerous lipid vacuoles in hepatocytes with nuclear migration at 35 DAH but such vacuoles decreased at 60 DAH.Liver from fish fed with the frozen copepods resulted in some intercellular spaces,collapsed cytoplasm and pycnotic nuclei of hepatocytes that were similar to starvation condition.These results indicated that suitable MDs could improve the development of digestive system of large yellow croaker larvae.Diet 1 can be used as basal formula for further research on nutrition and MD for large yellow croaker larvae because it was superior to Diets 2 and 3.

Dietary lysine requirement of large yellow croaker (Pseudosciaena crocea, Richardson 1846) larvae

A 30-day feeding experiment was conducted to estimate the lysine requirement of large yellow croaker larvae (2.75 ± 0.11 mg). Six isonitrogenous (509.5–519.7 g kg−1 crude protein) and isoenergetic (22.3–22.5 kJ g−1 energy) microdiets containing graded levels of lysine·HCl ranging from 24.8 to 41.0 g kg−1 diet in placement of glycine and glutamic acid were formulated. Mixture of crystalline amino acids (MAA) was supplemented to simulate the amino acid (AA) profiles of whole body of this larva, except for lysine. The MAA and supplemented lysine for each diet were coated with tripalmitin. Triplicate groups of 3000 fish were fed to apparent satiation by hand eight times per day. The results showed that specific growth rate (SGR), survival, body composition and the specific activity of digestive enzymes were significantly affected by dietary lysine levels (P<0.05). The optimal dietary lysine requirements estimated by second-order polynomial model based on SGR and survival were 33.7 (65.5 g kg−1 dietary protein) and 33.4 (64.9 g kg−1 dietary protein) g kg−1 dry diet respectively. The estimated requirements for the other essential AAs were calculated by A/E ratios of whole body AA profile of this larva based on lysine requirement.

Effects of dietary protein levels on the growth, survival, amylase and trypsin activities in large yellow croaker, Pseudosciaena Crocea R., larvae

A feeding trial was conducted to investigate the effects of dietary graded protein levels on the growth, survival, amylase and trypsin activities of large yellow croaker (Pseudosciaena crocea R.) larvae from 12 to 42 days after hatching (DAH). Five approximately isoenergetic microbound diets (16.65 MJ/kg diet) were formulated to contain different protein (47.1%, 52.0%, 57.1%, 62.2% and 67.5%) levels. Frozen copepods, containing 54.5% crude protein (CP), 6.0% crude lipid, 27.2% ash and 6.7% glycogen, were used as a control. Each diet was randomly fed to triplicate groups of larvae with an initial mean body weight of 1.76 ± 0.09 mg (mean ± SD) in 180 L white plastic tanks, and each tank was stocked initially with 3500 larvae. Both the survival and the specific growth rate (SGR) of large yellow croaker larvae significantly increased with increasing dietary protein level up to 57.1%, and decreased thereafter. Frozen copepods resulted in intermediate survival and low SGR compared with the other diets. Whole-body moisture and protein of larvae were not significantly affected by the dietary protein level. In contrast, whole-body lipid of larvae fed diet with 47.1% CP was significantly higher (P<0.05) than those from fish fed the diets containing more than 57.1% CP. Additionally, fish fed the frozen copepods had the lowest whole-body protein and lipid. The amylase-specific activity increased with increasing dietary carbohydrate level during the period of this experiment. However, trypsin activity was not significantly affected by the dietary protein content before 42 DAH, indicating a later onset of trypsin than amylase in the regulation of enzymatic synthesis induced by a dietary substrate.

The optimal feeding frequency of large yellow croaker (Pseudosciaena crocea, Richardson) larvae

A 30-day feeding experiment was conducted to determine the effects of feeding frequency on the growth, survival and specific activity of digestive enzymes in large yellow croaker larvae (13days after hatch) with an initial weight of 4.08±0.1mg. Feeding frequency of 2, 4, 8 and 12 times daily as four treatments were evaluated against a control without feeding in triplicate tanks. The fish were fed to satiation each time. The results showed that treatment of 8 meals per day (meals d−1) had significantly higher survival (P<0.05) compared with other treatments. Specific growth rate (SGR) in 8 meals d−1 treatment was significantly higher than those in 2 meals d−1 or 4 meals d−1 treatments (P<0.05), but was not significantly different from that in 12 meals d−1 treatment (P>0.05). No significant differences in coefficient variations (CV%, P>0.05) of fish larvae body length were observed among the treatments, but there was a significant negative dependency between CV and feeding frequency (CV=−0.1476×feeding frequency+17.55, R2=0.9352). Both crude protein and crude lipid in fish larvae significantly increased with increasing feeding frequency. There were no significant differences in fatty acid composition of fish larvae. The specific activity of trypsin, both in pancreatic and intestinal segments, first significantly increased (from 2 meals d−1 to 8 meals d−1) and then kept at a constant level (from 8 meals d−1 to 12 meals d−1). There were no significant differences in specific activities of amylase among dietary treatments. Results of this study suggest that the optimal feeding frequency was 8 meals d−1 in the culture of large yellow croaker larvae.

Colonization, proliferation, and survival of intraperitoneally transplanted yellowtail Seriola quinqueradiata spermatogonia in nibe croaker Nibea mitsukurii recipient

Recently, we developed an intraspecies spermatogonial transplantation technique in a pelagic egg spawning marine teleost, nibe croaker Nibea mitsukurii. Nibe croaker is an ideal candidate recipient for spermatogonial transplantation since it has a short generation time and small body size. In the present study, yellowtail Seriola quinqueradiata spermatogonia were transplanted into nibe croaker larvae, and the behavior of transplanted spermatogonia in recipient gonads was observed. Three weeks post-transplantation, yellowtail spermatogonia were incorporated into the gonads of 72 out of 88 recipients. An antiproliferating cell nuclear antigen was detected in incorporated yellowtail spermatogonia, suggesting that the xenogenic germ cells were proliferating in recipient gonads. Yellowtail vasa-positive spermatogonia survived for 11 months after transplantation in the gonads of recipient fish. Thus, we showed that the microenvironment in nibe croaker gonads can support the colonization, proliferation, and survival of germ cells derived from a different taxonomic family.

Spatial variation in otolith chemistry of Atlantic croaker larvae in the Mid-Atlantic Bight

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 382:185-195 (2009) - DOI: https://doi.org/10.3354/meps07993 Spatial variation in otolith chemistry of Atlantic croaker larvae in the Mid-Atlantic Bight Jason J. Schaffler1,*, Christian S. Reiss2, Cynthia M. Jones1 1Center for Quantitative Fisheries Ecology, Old Dominion University, 800 W. 46th St., Norfolk, Virginia 23529, USA 2NOAA Antarrtic Research Division, SWFSC, 8604 La Jolla Shores Dr., La Jolla, California 92037, USA *Email: jschaffl@odu.edu ABSTRACT: Larval Atlantic croaker Micropogonias undulatus (1 to 7 mm in standard length) were collected on the east coast of the United States from North Carolina to Delaware during 2000. We defined 3 water-mass boundaries for potential groups of spawning Atlantic croaker using temperature and salinity measured at each sampling station. We tested the hypothesis that distinct otolith chemistries existed among 3 groups of larval Atlantic croaker collected from these water masses using solution-based inductively coupled plasma-mass spectrometry. Multivariate analysis of variance indicated that otolith chemistry differed significantly among water masses. Using a quadratic discriminant function, we were able to correctly classify fish from the Mid-Atlantic Bight (MAB) 73% of the time, South Atlantic Bight (SAB) 53% of the time, and Chesapeake Bay plume 36% of the time. The correct reclassification rates observed were significantly better than random. Results from this study indicate that it is possible to obtain measurable elemental concentrations from otoliths much smaller than previously analyzed (weight 0.015 to 1.976 µg). Moreover, contrary to previous studies, our results indicate that it is possible to distinguish natal signatures among larvae on different spawning grounds in the MAB and SAB. Further, this new information could benefit investigations of dispersal from offshore spawning grounds to estuaries or other nursery habitats. KEY WORDS: Larvae · Otolith chemistry · Microchemistry · Connectivity · Spatial variability · Solution · Laser · ICP-MS Full text in pdf format PreviousNextCite this article as: Schaffler JJ, Reiss CS, Jones CM (2009) Spatial variation in otolith chemistry of Atlantic croaker larvae in the Mid-Atlantic Bight. Mar Ecol Prog Ser 382:185-195. https://doi.org/10.3354/meps07993Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 382. Online publication date: April 30, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Patterns of larval Atlantic croaker ingress into Chesapeake Bay, USA

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 378:187-197 (2009) - DOI: https://doi.org/10.3354/meps07861 Patterns of larval Atlantic croaker ingress into Chesapeake Bay, USA Jason J. Schaffler1,*, Christian S. Reiss2, Cynthia M. Jones1 1Center for Quantitative Fisheries Ecology, Old Dominion University, 800 W. 46th St., Norfolk, Virginia 23529, USA 2NOAA, Antarctic Research Division, SWFSC, 8604 La Jolla Shores Dr., La Jolla, California 92037, USA *Email: jschaffl@odu.edu ABSTRACT: We compared ingress patterns of Atlantic croaker Micropogonias undulatus larvae into Chesapeake Bay, USA, with published ingress patterns through barrier island inlets, the accepted model for larval fish ingress. This model asserts that larvae ingress on night flood tides at the flood-dominated side of the inlet and at all depths. At the Chesapeake Bay mouth and in the adjacent coastal waters, we compared the distribution of abundance, size, age, and growth rates of croaker prior to ingress. In contrast to the barrier island inlet model, croaker larvae were more abundant at depth than closer to the surface regardless of location. However, the response to light was variable, where croaker larvae farther offshore showed no response to light, but croaker larvae in the bay mouth were more abundant at night. Croaker larvae followed an expected pattern of increasing age and length from offshore stations to the bay mouth station. Further, among nearshore coastal stations there was evidence of larger and older croaker larvae at the northern portion of the bay mouth than at middle or southern stations. Patterns in growth were similar at all locations, indicating the likelihood of a single source location or similar environments among transport pathways for croaker larvae. Ingress can occur across the entire mouth of Chesapeake Bay; however, net tidal inflow may result in age and size structuring, which allows more rapid movement into the northern flood-dominated portions of the bay mouth. KEY WORDS: Larval ingress · Atlantic croaker · Chesapeake Bay · Depth · Daily age Full text in pdf format PreviousNextCite this article as: Schaffler JJ, Reiss CS, Jones CM (2009) Patterns of larval Atlantic croaker ingress into Chesapeake Bay, USA. Mar Ecol Prog Ser 378:187-197. https://doi.org/10.3354/meps07861 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 378. Online publication date: March 12, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.