Distribución del tamaño y variación mensual del desarrollo ovárico del cangrejo azul hembra, Portunus pelagicus en el golfo de Beibu, frente al sur de China

The present study was conducted to investigate the size distribution and seasonality variation of ovarian development for females of the blue swimmer crab, Portunus pelagicus, from Beibu Gulf, China. The results show that, based on pubertal moult, gonadosomatic index (GSI), morphology and histological configurations, the ovarian development cycle of P. pelagicus can be divided into five stages; Stage I, dominated by oogonia with some previtellogenic oocytes and endogenous vitellogeic oocytes; Stage II, dominated by endogenous vitellogenic oocytes with some previtellogeic oocytes and oogonia; Stage III, dominated by exogenous vitellogeic oocytes; Stage IV, of nearly mature oocytes; and Stage V, of mature oocytes with fully ripened ovary. GSI increased significantly during the ovarian development (P < 0.05), while the hepatosomatic index (HSI) appeared to decrease. Thus, a significant negative correlation was found between GSI and HSI (P < 0.01). The smallest carapace width of a mature female and that at which 50% of females reach maturity were 79.2 mm and 108.2 mm, respectively. The carapace width and body weight of the dominant size class ranged between 86 and 115 mm and 40 and 120 g, respectively. Furthermore, the highest GSI of female P. pelagicus was found in March, while the peak of ovigerous females was found in April.Este estudio se realizó para investigar la distribución del tamaño y la estacionalidad de desarrollo ovárico del cangrejo azul hembra, Portunus pelagicus en el golfo de Beibu, China. Los resultados muestran que, sobre la base de la muda de la pubertad, el GSI (índice gonadosomático), la morfología y las configuraciones histológicos y el ciclo del desarrollo ovárico de P. pelagicus puede dividirse en cinco etapas. Etapa I: La fase de oogonia (OG) dominaba con algunos ovocitos previtelogeicos (PR) y ovocitos vitelogeicos endógenos (EN); Etapa II: fase de EN dominaba con algunos PR y OG; Etapa III: la fase de ovocitos vitelogeicos exógenos (EX) era dominante; Etapa IV: fase de ovocitos casi maduros (NO); Etapa V: fase de ovocitos maduros (MO) y maduración completa del ovario. El índice gonadosomático (GSI) aumentó significativamente durante el desarrollo del ovario (P < 0.05), mientras que el índice hepatosomático (HSI) parecía disminuir. Por lo tanto, se encontró una correlación negativa significativa entre GSI y HSI (P < 0.01). La menor anchura del caparazón (CW) de una hembra madura y CW del 50% de las hembras maduras eran 79.2 mm y 108.2 mm, respectivamente. La CW y el peso corporal de la clase de tamaño dominante oscilaban entre 86-115 mm y 40-120 g respectivamente. Por otra parte, el GSI de la hembra más grande de P. pelagicus se encontró en marzo, mientras que el pico de las hembras ovígeras se produjo en abril en la población del golfo de Beibu

Salinity can change the lipid composition of adult Chinese mitten crab after long-term salinity adaptation

The Chinese mitten crab (Eriocheir sinensis) is an euryhaline crustacean, whose adults migrate downstream to estuaries for reproduction. Lipids are believed to be involved in salinity adaptation during migration. This study investigated the effects of different salinities (0, 6, 12, and 18‰) on the total lipids, neutral lipids, and polar lipids contents, and fatty acid profiles in the gonads, hepatopancreas, and muscles of adult E. sinensis after 40 days of salinity adaptation. The results showed that the males and females from 12‰ treatment had the highest contents of total lipids and neutral lipids in their hepatopancreas and total lipids in the muscles. Notably, salinity had a greater effect on the fatty acid profiles in the hepatopancreas compared to that in the gonads and muscles. The male hepatopancreas treated with 18‰ salinity had the highest percentage of total n-6 polyunsaturated fatty acid (∑n-6PUFA) in both neutral lipids and polar lipids, while the percentage of total n-3 polyunsaturated fatty acid (∑n-3PUFA) in neutral lipids and polar lipids decreased significantly with increasing salinity in males. In females, the 0‰ treatment had the highest percentages of total saturated fatty acids in neutral lipids and polar lipids in the hepatopancreas, while the highest ∑n-3PUFA and ∑n-6PUFA in neutral lipids and polar lipids were detected in the 12‰ treatment group. In conclusion, brackish water could promote the accumulations of total lipids and neutral lipids in the hepatopancreas and change the fatty acid profiles of adult E. sinensis, particularly in the hepatopancreas after long-term salinity adaptation

Size distribution and monthly variation of ovarian development for the female blue swimmer crab, <em>Portunus pelagicus</em> in Beibu Gulf, off south China

The present study was conducted to investigate the size distribution and seasonality variation of ovarian development for females of the blue swimmer crab, Portunus pelagicus, from Beibu Gulf, China. The results show that, based on pubertal moult, gonadosomatic index (GSI), morphology and histological configurations, the ovarian development cycle of P. pelagicus can be divided into five stages; Stage I, dominated by oogonia with some previtellogenic oocytes and endogenous vitellogeic oocytes; Stage II, dominated by endogenous vitellogenic oocytes with some previtellogeic oocytes and oogonia; Stage III, dominated by exogenous vitellogeic oocytes; Stage IV, of nearly mature oocytes; and Stage V, of mature oocytes with fully ripened ovary. GSI increased significantly during the ovarian development (P < 0.05), while the hepatosomatic index (HSI) appeared to decrease. Thus, a significant negative correlation was found between GSI and HSI (P < 0.01). The smallest carapace width of a mature female and that at which 50% of females reach maturity were 79.2 mm and 108.2 mm, respectively. The carapace width and body weight of the dominant size class ranged between 86 and 115 mm and 40 and 120 g, respectively. Furthermore, the highest GSI of female P. pelagicus was found in March, while the peak of ovigerous females was found in April

Lipid nutrition of early life history of two commercially important tropical crustaceans, the blue swimmer crab (Portunus pelagicus) and the ornate rock lobster (Panulirus ornatus), with emphasis on highly unsaturated fatty acids

The blue swimming crab, Portunus pelagicus and ornate rock lobster, Panulirus ornatus are two commercially important crustacean species of high market value with wild populations distributed throughout the tropical and sub-tropical Indo-Pacific region. As the wild populations of P. pelagicus and P. ornatus have been over-exploited, there is an increasing interest in the development of their aquaculture to meet the rising market demand. However, one of the major challenges for closed-life cycle production of P. pelagicus and P. ornatus is the development of a commercially viable hatchery technology. Comprehensive and quantitative understanding of larval nutrition is very important for the development of a reliable hatchery technology of P. pelagicus and P. ornatus. However, basic knowledge of the nutritional requirements and physiology is very limited for the early life stage of both species.\ud \ud It is well known that lipids play a crucial role on the survival, growth and development of crustacean larvae. To further knowledge in this area a series of experiments were initially conducted to understand the ontogenetic changes of key lipid composition, including lipid classes and fatty acids, during the embryonic and larval development. This was extended to measure changes of lipid composition during the starvation of newly hatched larvae of P. pelagicus and P. ornatus. From this foundation, four experiments were designed to assess dietary optimum 20:4n6 (ARA) levels and the 22:6n3/20:5n3 (DHA/EPA) ratios for P. pelagicus and P. ornatus larvae based on enriched Artemia, which is one of the commonly used hatchery feeds for marine crustacean larvae. Experiments included enriched Artemia containing different levels of dietary fatty acids which were fed to newly hatched larvae of P. pelagicus and P. ornatus. In these experiments the survival, development, growth and fatty acid composition of larvae were closely monitored to identify the dietary optimum HUFA composition.\ud \ud \ud Chapter 2 and 3 were conducted to investigate the changes of lipid class and fatty acid composition during the embryonic development of P. pelagicus and P. ornatus. For both species, there are significant increases of egg volume and moisture content while the total lipid content decreased dramatically. However, different trends were found between the lipid class profiles of P. pelagicus and P. ornatus, including the percentage of phospholipids (PL), free fatty acids (FFA) and cholesterol (CHO) (%total lipid). The principal fatty acids were 16:0, 16:1n7, 18:1n9, 18:1n7, 20:4n6 (ARA), 20:5n3 (EPA) and 22:6n3 (DHA) in the eggs of both species. Despite of embryonic stages, significantly higher DHA levels and DHA/EPA ratios were found in the eggs of P. ornatus compared to P. pelagicus. However the eggs of P. pelagicus contained higher ARA level than that of P. ornatus. During embryonic development, ARA, EPA and DHA were relatively conserved for P. pelagicus while 18:1n9, 18:2n6, ARA and EPA were relatively conserved for P. ornatus. These differences indicate that the two crustacean species have different lipid dynamics during their embryonic development.\ud \ud Chapter 4 and 5 were designed to investigate the ontogenetic changes of growth and lipid composition during larval development of both species. Although individual biomass and body size increased significantly, the specific growth rate (SGR%/day) of body weight generally decreased significantly during the larval development of both species. The lipid class profile of early-mid Stages phyllosoma were dominated by PL (>85% total lipids) for P. ornatus while the significant lower PL levels were detected in the late stage P. pelagicus larvae compared the newly hatched P. pelagicus larvae and all early-mid Stages P. ornatus larvae. Generally, the fatty acid composition of larvae reflects that of their larvae diet. However, ARA and DHA were preferentially accumulated by later larval stage of P. pelagicus while early-mid Stage (II-V) phyllosoma preferentially sequestered and accumulated a higher proportion of ARA, EPA and DHA compared to the levels that present in their diet. These data indicate that larval P. pelagicus and P. ornatus have an ability to preferentially sequester, store or modify their dietary lipid composition to support normal growth and development.\ud \ud Chapter 6 and 7 were designed to examine the effects of starvation on survival, biomass and lipid composition and to explain the preferential conservation of important fatty acids for newly hatched larvae of P. pelagicus and P. ornatus. The results showed that during starvation, significant decreasing trends were detected on individual body dry weight, total lipids (%dry weight) or per larva (μg/larva) for the newly hatched larvae of P. pelagicus and P. ornatus. During the starvation, more than 50% of PL was utilized for the larvae of both species, indicating the oxidation of membrane structural lipids. The higher reductions were found on EPA and DHA than other fatty acids during the starvation of P. pelagicus larvae while both DHA and ARA were highly conserved for newly hatched P. ornatus phyllosoma. These results suggested that the HUFA requirement of larval P. pelagicus is lower and different to early Stage P. ornatus phyllosoma.\ud \ud Chapter 8 and 9 were designed to investigate the basis for the relative conservation of ARA during the starvation of newly hatched larvae of both species. Investigations included revealing the dietary optimum ARA contents for the survival, development and growth of P. pelagicus and P. ornatus larvae as supplied through the feeding enriched Artemia as larval food. For larval P. pelagicus, dietary ARA level significantly affected not only survival, development and vii growth of the larvae, but also the occurrence of moulting death syndrome (MDS) as well as the ratio of chela length/carapace length (CHL/CL) of zoea IV. For the early Stage P. ornatus larvae, dietary ARA levels did not significantly affect survival, but significant differences were detected on development time and growth among the different treatments. The results suggest that optimal ARA level is approximately 6.27 mg/g DW (2.97% of total fatty acids) in the enriched Artemia for P. pelagicus larvae, and around 3.69 mg/g DW (1.90% total fatty acids) for early Stage P. ornatus phyllosoma.\ud \ud Although previous studies have shown dietary DHA/EPA ratios are very important for crustaceans, no available information could be found for its importance in the larvae of P. pelagicus and P. ornatus. Therefore, two experiments were conducted to investigate the dietary optimum DHA/EPA ratios for P. pelagicus and P. ornatus larvae. There were five treatments with newly hatched larvae fed enriched Artemia contained different DHA/EPA ratios. Although no significant difference was found on the survival of early stage larvae for both species, the highest survival was found on the treatment fed enriched Artemia contained medium DHA/EPA ratio until megalopal stage of P. pelagicus. The dietary DHA/EPA ratios also significantly affected the development time and growth for both species. The dietary optimum DHA/EPA ratios were estimated at ca. 0.53 and > 1.64 for P. pelagicus larvae and early Stage phyllosoma of P. ornatus, respectively, which clearly indicated the early Stage phyllosoma of the ornate rock lobster had higher DHA/EPA ratio requirement than P. pelagicus larvae. These findings indicated that the optimization of the fatty acid composition of hatchery food will be an effective means to improve seed quality and quantity for both species.\ud \ud The current project utilized an integrated methodology approach to study fatty acid nutrition of P. pelagicus and P. ornatus larvae. The embryonic and larval development experiments related to ontogenetic changes of key lipid composition were targeted to obtain fundamental information, followed by growth trails to identify the specific fatty acids requirement or ratios. Fatty acid analysis was used to gain a deep understanding of underlying mechanisms. The findings have significantly enhanced our understanding of fatty acid nutrition for P. pelagicus and P. ornatus larvae, which will facilitate the further improvement of hatchery technology and formulated diets for the larval culture of both species

Physiological Responses and Ovarian Development of Female Chinese Mitten Crab Eriocheir sinensis Subjected to Different Salinity Conditions

Salinity plays a key role affecting ovarian development, osmoregulation and metabolism of female Chinese mitten crab, Eriocheir sinensis during reproductive migration. In this study, female E. sinensis after their puberty molt were subjected to four salinities of 0, 6, 12, and 18‰ for 40 days to investigate the salinity effects on their ovarian development as well as a range of important physiological parameters. Elevated salinity accelerated the ovarian development with ovigerous crabs found at salinity treatments of 12 and 18‰ despite no copulation had occurred. Meanwhile the survival rate of female crabs showed a decreasing trend with increasing salinity. Higher salinity also led to increased hemolymph Na+, K+, Ca2+, Cl−, and Mg2+ concentrations. The 6‰ treatment had the highest contents of hemolymph total and major free amino acids while the Na+/K+ -ATPase activity in the posterior gills was the lowest among treatments. Total n-3 polyunsaturated fatty acids (∑n-3PUFA) and n-3/n-6 PUFA ratio in the anterior gills showed a decreasing trend with salinity while 18‰ had the highest ∑PUFA and ∑n-6PUFA. The ∑n-3PUFA content and n-3/n-6 PUFA ratio of the posterior gills showed a fluctuating pattern and the highest value was detected at 0‰, while an increasing trend was found for the ∑n-6PUFA with increasing salinity. The hemolymph glucose showed a decreasing trend with increasing salinity and the highest total cholesterol in hemolymph was detected at 12‰. The 18‰ treatment had the highest levels of hemolymph γ-glutamyltransferase, alkaline phosphatase and acid phosphatase, as well as glucose, urea and acid phosphatase in hepatopancreas while the highest hemolymph superoxide dismutase and malondialdehyde were detected at 0‰. Overall, the results showed that salinity increase from freshwater to brackish conditions led to lower metabolism, accelerated ovarian development, and the appearance of ovigerous crabs without copulation in female E. sinensis post puberty molt

Patterns of larval growth, lipid composition and fatty acid deposition during early to mid stages of development in Panulirus ornatus phyllosoma

The tropical spiny lobster, Panulirus ornatus, is a commercially important Palinurid marine lobster species of high market value with wild populations distributed throughout the tropical and sub-tropical Indo-Pacific region. As wild populations of P. ornatus has been over-exploited, so there is interest in the development of this lobster aquaculture to meet current and rising market demand for supply. However, a major challenge for closed-life cycle production of Palinurid lobsters is the development of a commercially viable hatchery technology. There is minimum knowledge of larval nutrition, and in particular, the lipid requirements. The current study focused on investigations into the growth pattern and ontogenetic changes of lipid composition for early–mid stage P. ornatus (stages I–VI) under controlled laboratory conditions. Body wet weight (WW), dry weight (DW) and total body length (TBL) increased exponentially with the number of stages. There were large increases in WW, DW and TBL between stages I and VI, with increases of 4092%, 3864% and 504%, respectively. The greatest increase in DW and WW was noted between stages III to IV while the greatest specific growth rate (SGR) was noted during stages I to II. The lipid class profile of phyllosoma was dominated by phospholipids (PL) for all early stages (I–V) despite the high triacylglyceride (TG) content of Artemia; which was the primary food source. The newly hatched phyllosoma contained higher percentages of total saturated fatty acids (SFA), 20:5n3 (EPA), 22:6n3 (DHA) and total highly unsaturated fatty acids (HUFA) compared to that found in all other stages. From stages II to V, the total lipid, lipid class and fatty acid profile of phyllosoma resembled those of their diet with the exception of 20:4n6 (ARA). The increase in ARA concentration during phyllosoma development (stages II–V) suggested that mid-stage phyllosoma (IV and V) had a higher requirement compared to that noted in early-stage (II and III) phyllosoma. It was noted that early-stage (II and III) phyllosoma preferentially sequestered and accumulated a higher proportion of EPA and DHA compared to that present in their diets. These data indicate that early–mid stage P. ornatus phyllosoma have an ability to preferentially sequester, store or modify their dietary lipid composition to support normal growth and development. These results provide important morphometric date useful in the evaluation of larval feed and culture conditions as well as, providing baseline larval lipid nutrition data required for the development of artificial diets for P. ornatus phyllosoma

Effects of starvation on survival, biomass, and lipid composition of newly hatched larvae of the blue swimmer crab, Portunus pelagicus (Linnaeus, 1758)

Lipids are crucial nutrients for survival and development of crustacean larvae. This study investigated the effects of starvation on survival, body weight, and lipid composition of newly hatched larvae of Portunus pelagicus. The results showed that during starvation, average survival time of newly hatched zoea I larvae was 3.87 days. A significant decreasing trend was detected for individual dry weight (DW) during starvation and was described as DW = 0.2x^2 - 1.462x + 15.023, R^2 = 0.9985, where x is the starvation duration in days. DW and total lipids decreased by 17.42 and 38.46 % after 3 days of starvation, respectively. For newly hatched larvae, total lipids were dominated by phospholipids (PL) (75.55-93.57 %) and 50.39 % of PL were utilized during the 3-day starvation period. This indicates that membrane structural lipids of newly hatched P. pelagicus larvae were oxidized as an energy source during continuous starvation. There were concurrent increases in free fatty acids and cholesterol that probably resulted from the decomposition of sterol esters to free fatty acids and cholesterol. Newly hatched P. pelagicus larvae contained substantially higher levels of 20:5n3 (18.90 %) and 22:6n3 (18.24 %) than other Portunid crabs. During starvation, the highest fatty acid reduction rates were found for 20:4n6, 20:5n3, and 22:6n3 (P < 0.05), and the preferential depletion of these fatty acids may suggest that the HUFA requirements of early P. pelagicus larvae are lower than those of the other Portunids

Hemocytes transcriptome profile of the Chinese mitten crab (Eriocheir sinensis)

The Chinese mitten crab (Eriocheir sinensis) possesses an open circulatory system, in which hemolymph moves through interconnected sinuses or spaces surrounding organs called hemocoels. The hemocytes are classified into hyalinocytes, semigranulocytes, and granulocytes; and limited transcriptomics research is available. In this study, the transcriptome of the crab E. sinensis hemocytes was characterized. A total of 14,380,229 clean reads representing a total of 4.31 Gb nucleotides dataset were produced. A total of 67,047 contigs were obtained and 12.49% (8375) and 9.74% (6533) of the contigs were matched to data publicly available from the GenBank nr nucleotide and Uniprot databases, respectively. Among these contigs, 4344 contigs belong to three categories of Gene Ontology, 126 contigs to 21 subcategories of KEGG, and 4962 contigs to 25 categories of the COG database. A total of 508,379 and 345 transcripts of the E. sinensis showed >40% sequence similarity with transcripts expressed in the vertebrate blood cells from tilapia (Oreochromis niloticus), Chinese softshell turtle (Trionyx sinensis) and chicken (Gallus gallus) respectively. A total of 53,077 single nucleotide polymorphisms were identified and 9912 SSRs for microsatellite mining were found. The most frequent repeat motifs detected were dinucleotide repeats, accounting for 37.52% of the total repeats. Our data provides an important gene resource for the exploitation of molecular marker-assisted breeding, immune mechanisms and conservation of germplasm in the crab E. sinensis. Keywords: Eriocheir sinensis, Hemocytes, Transcriptom

Selective breeding could improve the juvenile quality of Chinese mitten crab Eriocheir sinensis

Chinese mitten crab Eriocheir sinensis is an important aquaculture species in China, and a selective breeding program has been operated for the economic traits of growth and different maturity time of this species since 2011. This study was aimed to evaluate the juvenile quality of two selected E. sinensis lines (i.e. early-maturing strain: EM, late-maturing strain: LM), pond-reared juveniles without selection (PR) and wild-caught juveniles (WC). The results showed that: (1) Significant growth difference were only observed in females that the SGR of EM juveniles and the survivor of WC juveniles were both significantly higher than the PR, and the intermolt period of WC was significantly lower than the PR. Although EM juveniles had relatively shorter intermolt period and higher WGR than the LM, they both exhibited better growth performance than the PR, in terms of higher WGR and SGR. (2) Hepatopancreatic AKP activities of PR juveniles were significantly lower than other three populations for both genders, and hepatopancreatic MDA content was significantly higher in the WC juveniles. Moreover, hemolymphatic levels of ACP and T-AOC of both EM and LM juveniles were significantly higher than other two populations. (3) The injection of Aeromonas hydrophilia resulted in the highest and lowest cumulative mortalities to the WC and PR juveniles respectively, mortalities of EM and LM juveniles were similar and located between WC and PR juveniles. In conclusion, juvenile quality of EM and LM strains obtained certain promotion after three generations of selection for growth and different maturity time