Seasonal changes in plasma gonadal steroid concentrations and gonadal morphology of male and female tench (Tinca tinca, L.)

In order to gain a better understanding of the reproductive cycles of male and female tench (Tinca tinca), gonadosomatic index, gonad histology and plasma concentrations of estradiol‐17β (E₂), testosterone, an drostenedione, 11‐ketotestosterone (11‐KT), 17,20β, 21‐trihydroxy‐4‐pregnen‐3‐one (17,20β,21‐P), 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) and 17,20α‐dihydroxy‐4‐pregnen‐3‐one (17,20α‐P) were measured at the four seasons of the year, plus a further sampling coincident with the peak of spawning in early July. As expected, in both males and females, the plasma concentrations of androgens (excluding 11‐KT in females – undetectable) and C₂₁ steroids were significantly more elevated in the spring and summer (when most gonadal development took place) than in the autumn and winter. The only unexpected finding was that 17,20β‐P and 17,20β,21‐P, the steroids that are normally associated with oocyte final maturation in females and spermiation in males, were found in substantial amounts in both pre‐vitellogenic, pre‐spermatogenic and post‐spawning fish. This suggests that these steroids may have other as yet unidentified roles in this species.     

Growth of the hard clam Meretrix lusoria in Taiwan

The growth of hard clam Meretrix lusoria in Taiwan was observed as it was grown at six different stocking rates (55, 109, 172, 244, 344 and 455 clams/m²), from November 1979 to September 1980. It was found that the stocking rate had more effect on the increase of the total weight of the clam than on the shell length. Under the environmental condition of the study site, the optimum stocking rate was 244 clams/m². When the net production of the clam was lower than 1103 g/m², the growth of the individual clam was not affected by the stocking rate. But when the net production was higher than 1589 g/m², the growth of the individual clam seemed to be retarded. The average pH of the sea water in the clam culture area was between 7.9 and 8.4. The average dissolved oxygen content was between 4.2 and 11.2 mg/l. And the average water salinity was between 30‰ and 35‰. All these three factors did not seem to have direct relationship with the growth of the clams. Sea water temperature, however, showed great effects on the growth of the clams. It is shown that the growth of the hard clam was slow at a water temperature of 15–18°C, increased at 20–22°C, and accelerated at 25–32°C.     

文蛤生长因子受体结合蛋白2(GRB2)基因克隆、时空表达及SNP位点筛查

为探索文蛤GRB2基因的结构和功能,本实验通过已构建的文蛤转录组文库,利用SMART RACE技术扩增得到了文蛤GRB2基因的cDNA全长序列,对其生物信息学、组织及发育阶段表达特征进行了分析,并利用直接测序方法在外显子中筛选SNP位点。结果显示,GRB2基因cDNA全长1791bp,开放阅读框669bp,编码223个氨基酸,蛋白由SH-SH2-SH3三个结构域组成;氨基酸序列比对发现,文蛤GRB2与泥蚶的同源性最高,达到65.6%,与脊椎动物的同源性都在60%以上,说明GRB2基因在进化过程中比较保守。qRT-PCR结果表明,GRB2在文蛤6个组织和10个发育时期中均有表达,但不同组织间的表达量并没有显著差异(P＞0.05);发育时期中的表达量呈现逐渐升高的趋势,在壳顶幼虫时期达到最高,之后表达量又有所降低。SNP位点的筛选结果表明,在GRB2基因的外显子区域共发现16个SNP位点。     

泥蚶Smad1/5基因cDNA全全长克隆及时空表达特征分析

为了研究Smad1/5基因在泥蚶生长、发育过程中的调控作用,本文利用SMART RACE方法克隆得到泥蚶Smad1/5基因（Tg-Smad1/5）的cDNA全长序列,该序列全长2 424 bp,开放阅读框有1 386 bp,编码462个氨基酸。Tg-Smad1/5蛋白与合浦珠母贝Smad5、太平洋牡蛎Smad5和大西洋舟螺Smad1的同源性分别达到了92.3%,91.2%和80.4%,与脊椎动物的同源性都在70%以上;该蛋白包含MH1和MH2区两个较为保守的结构域,此结构与高等动物Smad1和Smad5蛋白极为相似,表明该基因在物种进化过程中比较保守。利用qRT-PCR技术,研究了Smad1/5基因在泥蚶6个组织和9个发育时期中的表达情况,结果显示,Tg-Smad1/5基因在泥蚶成贝6个组织中均有表达,而在斧足中的表达量最高,极显著地高于其他组织;在各发育时期中,Tg-Smad1/5表达量随发育进程呈逐渐升高的趋势,在眼点幼虫期达到最高,极显著高于其他时期,而在变态至稚贝时,表达量又极显著地下降。研究结果表明,Tg-Smad1/5具有类似于高等动物的分子结构,并在泥蚶不同组织、不同发育时期表达有所差异,这为进一步研究该基因在贝类中的功能和作用机制奠定了重要基础。     

双须骨舌鱼性腺发育的组织学观察

通过组织学研究方法,分别对双须骨舌鱼Ⅱ~Ⅴ期的卵巢及Ⅱ~Ⅵ期精巢的形态结构、特征及生殖细胞变化进行描述。结果显示,Ⅱ时相卵母细胞的细胞核较大,约为细胞体积的一半;Ⅲ时相卵母细胞出现卵黄斑及卵黄颗粒;Ⅳ时相卵母细胞中卵黄迅速积累且细胞膜出现褶皱;Ⅴ时相卵母细胞膜表面的褶皱消失。雄性双须骨舌鱼精巢发育的Ⅱ期,只含有初级精母细胞。Ⅲ期精巢分布有初级和次级精母细胞,精小管形成且小管中充满精细胞;Ⅳ期精巢主要含有初级和次级精母细胞以及精原细胞,精小管中出现空腔;Ⅴ期精巢中包含次级精母细胞、精原细胞和精子细胞,精小管中的空腔增大;Ⅵ期精巢则显示出高度血管化和结缔组织增多等特点。本研究将为双须骨舌鱼人工繁殖提供参考。     

脊尾白虾的性腺发育及组织结构观察

为系统研究脊尾白虾的性腺发育及组织学特征,采用常规的石蜡切片及H.E染色方法对脊尾白虾的性腺发育及其组织结构进行观察。结果表明,脊尾白虾的雌性生殖系统由卵巢、输卵管及排卵孔组成。卵子发生经历了卵原细胞、卵黄合成前期卵母细胞、内源性卵黄合成期卵母细胞、外源性卵黄合成期卵母细胞,最后发育为成熟的卵母细胞。卵巢发育可分为增殖期、小生长期、大生长期、成熟期及产后恢复期。脊尾白虾雄性生殖系统由精巢、输精管及排精孔组成。精巢由生精小管构成,不同生精小管内精子发育可不同步。精子发生经历了精原细胞、初级精母细胞、次级精母细胞、精细胞,最后发育为精子。输精管可分为前、中、后输精管及末端壶腹,精荚在输精管中形成。     

The reproductive biology of the baby clam, Marcia opima, from two geographically separated areas of India

A study of the reproductive cycle of the baby clam, Marcia opima (Gmelin) was conducted at two sites along the southeast (Tuticorin Bay) and southwest (Ashtamudi estuary) coast of India from December 1998 to January 2000. Histological evidence showed that baby clam from both the sites showed two spawning seasons. First spawning season was recorded from May to July in the southeast coast. In the southwest coast, the first spawning season was observed through March to May. A second spawning season from September to December was recorded in both the coasts. In the southeast coast, minimum and maximum condition indices were obtained in January 2000 and April 1999 respectively and decreased from May to June and November to January, signifying the two spawning periods. Most of the animals were either in spent or indeterminate gonadal stage from May to August and November to January indicating the active spawning during that months in the southeast coast.     

Biochemical changes during larval development in the short neck clam, Paphia malabarica Chemnitz

Biochemical compositions were determined for eggs, D-shaped larvae, umbo larvae and pediveliger of the short neck clam Paphia malabarica Chemnitz. Spawned eggs were composed of 63.2% protein, 25.4% lipid and 11.4% carbohydrate. After 48 h of embryogenesis, 2.6% of the protein, 11.8% of the lipid and 3.2% of carbohydrate mass had been lost, providing 20.5%, 75.4% and 4.1% of the total energy expenditure of 0.2147 mJ embryo⁻¹. During 48 h of metamorphosis, lipid was utilized first, followed by a heavy consumption of protein; protein, lipid and carbohydrate lost 23.8%, 50.2% and 32.5% of their mass respectively. Protein and lipid supplied a comparable amount of energy for metamorphosis, 34.2% and 55.2%, respectively, whereas, carbohydrate contributed only 10.6% to the 2.733 mJ larva^−l metamorphic energy expenditure.     

Nitrogen and phosphorous budgets during a farming cycle of the Manila clam Ruditapes philippinarum: An in situ experiment

In the Sacca di Goro lagoon a farming cycle of the Manila clam (Ruditapes philippinarum) was simulated seeding young molluscs in an unexploited sandy spot. The experimental area (2100 m²) consisted of three sectors: a control (C), almost devoid of clams (∼ 1600 m^− 2, ∼ 30 ind m^− 2), a low (L) density area (400 m², ∼ 300 ind m^− 2) and a high (H) density zone (∼ 110 m^− 2, ∼ 800 ind m^− 2). Water chemistry, external freshwater nutrient loads, molluscs filtration rates, biomass, elemental composition and nutrient recycling were analysed.Clam filtration rates and light and dark fluxes of nutrients were measured with intact core incubations. Three replicate cores (i.d. 20 cm) were collected from C, L and H in April, one month after the seeding, June, August and October 2003. External loads were calculated multiplying dissolved and particulate nutrients concentration by freshwater flow from the main lagoon tributaries. Direct excretion, filtration activity of clams and particulate matter deposition resulted in significantly higher ammonium (NH₄⁺) and soluble reactive phosphorus (SRP) effluxes to the water column at L and H. For the entire farming cycle, particulate nitrogen (PN) uptake by clams from the water column was 1.7 (C), 9.1 (L) and 16.3 (H) mol m^− 2, whilst total dissolved nitrogen (TDN) fluxes were − 0.3 (C), 1.6 (L) and 6.9 (H) mol m^− 2. Particulate phosphorus (PP) uptake from the water column was 0.1 (C), 0.6 (L) and 1.0 (H) mol m^− 2, whilst total dissolved phosphorus (TDP) efflux was 0.2 (C), 0.5 (L) and 0.8 (H) mol m^− 2. At the end of the farming cycle, harvested N as mollusc flesh was negligible for C, 0.4 mol m^− 2 for L and 1.8 mol m^− 2 for H. Harvested P as mollusc flesh was negligible for C, 0.02 mol m^− 2 for L and 0.04 mol m^− 2 for H. Farmed areas seem to have a great potential for fast coupling between sedimentation (filter feeder mediated biodeposition) and benthic recycling. At the lagoon level, mollusc farming probably attenuates the export of particulate matter to the open sea. Our results show that a minor fraction of biodeposited N (∼ 6%) and P (∼ 3%) was exported as a commercial product at the end of the farming cycle, whilst a larger fraction was incorporated in the sediments or recycled as dissolved inorganic or organic forms.     

Growth and gonadal development in diploid and triploid turbot (Scophthalmus maximus)

This study determined the effect of triploidy on the survival, growth and gonadal development of turbot from 6 to 48 months of age. From 6 to 24 months of age (first sexual maturity), survival was similar in both ploidies (P > 0.05). From 24 to 48 months of age, after the first sexual maturity, survival was 91.9% in diploids and 100% in triploids, which did not exhibit the post-spawning-associated mortality. Growth was similar for both ploidies during the first year of life. After that, triploids grew significantly (P < 0.05) more that diploids, with more marked differences after each spawning season. From 24 to 48 months, the average weight difference between both ploidies was 11.4 ± 1.9%, ranging from 4.3 to 23.0%. At 47 months of age, the biomass of triploids was 10.3% greater in total weight and 14.3% greater in eviscerated weight. Gonads of triploid males were similar to that of diploids, whereas in triploid females, they were significantly smaller and rudimentary. A histological analysis carried out at 47 months of age showed complete sterility of triploids in both sexes. Sex ratio was 1 male (M):0.6 female (F), for diploids, significantly (P < 0.05) different from 1:1, and 1 M:3.3 F for triploids, significantly (P < 0.05) different from 1:1 and from the diploids. Since females grow more than males, culture of triploids benefited from the high female ratio, which helped to reduce size dispersion. In addition, their sterility allowed better performance by avoiding the reduction in growth that takes place during the spawning periods. Together, these observations indicate that triploidy induction can be an interesting option for turbot aquaculture, especially for the production of large-size fish of more than 2 years of age.     

缢蛏IGFBP基因结构及生长性状相关SNP筛选

类胰岛素生长因子结合蛋白(IGFBP)是IGF系统的一部分,主要参与IGF的运输、定位和生物活性调节。本研究采用RACE技术和长PCR技术,克隆了缢蛏IGFBP基因的cDNA和DNA全长序列,应用荧光定量PCR技术分析了缢蛏不同发育时期和不同组织中IGFBP mRNA的表达特征,并进一步筛选了IGFBP基因与生长性状相关的SNP位点。序列分析表明,缢蛏IGFBP cDNA序列全长631 bp,包括5'端非编码区60 bp,3'端非编码区136 bp和开放阅读框435 bp,编码144个氨基酸。该基因含有保守的IGFBP-N端,包含12个半胱氨酸残基,其中1～18个氨基酸为信号肽,属于分泌型蛋白。IGFBP DNA全长3 122 bp,其中包含1个内含子(2 687 bp)和2个外显子(200和235 bp)。荧光定量PCR结果显示,IGFBP mRNA在消化腺组织中表达量最高;在缢蛏的稚贝期,IGFBP mRNA呈现高表达,而在其他发育时期表达量低。在IGFBP基因中筛选到4个SNP位点,其中1个SNP位点与缢蛏的壳长和体质量呈显著相关。     

Seasonal and nutritional effects on the fatty acids of three species of shrimp, Penaeus setiferus,P. aztecus and P. duorarum

The fatty acids of three species of shrimp from the Gulf of Mexico, white (Penaeus setiferus), brown (P. aztecus), and pink (P. duorarum), were analyzed periodically for 1 year. The fatty acid patterns of varied species of shrimp collected at the same time of the year differed very little from each other. On the other hand, a slight but distinctive seasonal variation of the fatty acid composition, irrespective of Penaeus species, was observed. Saturated fatty acids increased during the warm seasons and decreased during the cold months, while the opposite behavior was exhibited by monoenoic and polyenoic fatty acids. When the variations in fatty acid levels were compared to the temperature of the water, there was a 2-month lag period between a change in water temperature and the corresponding variation in fatty acid composition. This slow alteration of the shrimp fatty acids suggests that the changes are effected through the food chain rather than by endogenous adjustment to an alteration in water temperature.Further studies were performed in which the fatty acid patterns of pond- and laboratory-reared shrimp were compared with those of their food. Evidence was obtained confirming the significant effect of diet on the fatty acids of shrimp lipids. Shrimp incorporated certain dietary fatty acids readily but showed little ability for the conversion of C₁₈ polyunsaturated fatty acids into C₂₀ and C₂₂ fatty acids of higher unsaturation. Thus, the C₂₀ and C₂₂ fatty acids which are essential for shrimp growth cannot be substituted in the diet by C₁₈ precursors.Considered in toto, these experiments suggest that diet exerts a strong influence on the composition of shrimp body lipids and that, contrarily, endogenous synthesis or modification occurs to a low degree.     

Hematological parameters and phagocytic activity in fat snook (Centropomus parallelus): Seasonal variation, sex and gonadal maturation

The objective of this work was to determine hematological parameters and the phagocytic capacity of peritoneal macrophages of the fat snook related to sex, stage of gonadal maturation and seasonal cycle. The hematological results did not show significant differences between males and females. With respect to stage of gonadal maturation, only erythrocytes numbers (RBC), in females, was found to be significantly elevated in stage III (maturing) and decreased in V (spent). An analysis of the results of the erythrocyte and leukocyte series, thrombocytes and phagocytic activity related to sex and seasonal cycle showed statistically significant differences: a) hematocrit (Ht) and hemoglobin concentration (Hb) were elevated in the spring and low in the winter in males; b) mean corpuscular volume (MCV) was high in the spring and summer and low in the fall in both sexes; c) thrombocytes numbers were elevated in the fall and low in the other seasons in females; d) phagocytic capacity (PC) and phagocytic index (PI) were higher in the summer and lower in the fall in females. The results showed that spring and summer correspond to seasons of the year for better hematological and phagocytic responses for survival of the fat snook in its natural habitat. The parameters studied could be utilized for evaluation of the health status fat snook in its own habitat or in captivity.     

Influence of dietary protein on essential fatty acids in the gonadal tissue of the sea urchins Psammechinus miliaris and Paracentrotus lividus (Echinodermata)

The elevated accumulation of certain essential long-chain polyunsaturated fatty acids (PUFA) during reproductive maturation can place a significant demand on lipid metabolism. As lipid metabolism is closely linked with protein metabolism, protein intake during maturation may significantly influence transport proteins and enzyme activity which is responsible for supplying the essential fatty acids for gamete development. The present study investigated the influence of increased protein intake on the accumulation of certain long-chain PUFA in two species of commercially valuable sea urchin, Paracentrotus lividus and Psammechinus miliaris during maturation. Sea urchins were fed three macroalgal diets over a 90-day period. These diets included the red alga Palmaria palmata, which had been grown in seawater enriched with two levels of ammonia-N, which produced a high protein content (41%) or low protein content (32%). The third diet (or reference diet) used the brown macroalga Laminaria saccharina with a 23% protein content. The fatty acid composition of the gonads was determined by GC. Feeding the high protein diet had no effect on the maturation and total lipid in the gonad compared with the low protein diet, however, it did significantly increase the levels of docosahexaenoic acid DHA 22:6n-3 in the mature gonad tissue in P. miliaris and P. lividus. In contrast, only P. miliaris exhibited higher levels of arachidonic acid ARA 20:4n-6 when fed the high protein diet. The present study suggests that elevated protein levels can promote the accumulation of DHA and ARA in gonadal tissue during maturation, although the extent of the influence is species-specific and highlights the importance of understanding the complexities and inter-connectivity between protein and lipid metabolism when producing commercially valuable species.     

Differences in the digestive biochemistry between the intertidal clam, Ruditapes decussatus, and the subtidal clam, Venerupis pullastra

The present study was aimed to evaluate differences in physicochemical characteristics (pH and temperature optima) of the main digestive enzymes (amylase, cellulase, laminarinase, and protease) in two commercially important bivalves, the intertidal clam, Ruditapes decussatus, and the subtidal clam, Venerupis pullastra, as well to assess individual variability of such activities. The assays were performed on extracts obtained from the digestive glands and crystalline styles of individuals collected in the wild and laboratory-conditioned during 1 week. In both species, maximum activity for amylase and cellulase was measured at pH 6 and that of laminarinase at pH 5.5, while pH profiles of protease activity showed important differences between them. Temperature profiles also showed interspecific variations, mainly in laminarinase. Carbohydrase activities were comparatively much higher in R. decussatus and proteolytic activities in V. pullastra. The observed differences both in physicochemical characteristics and relative importance of digestive enzymes are discussed in relation to the amount and type of food available in their respective habitats.     

罗非鱼海豚链球菌病的病理学观察

采用光学显微镜和透射电子显微镜技术分别对患海豚链球菌病的罗非鱼的病理学变化进行了研究。分离的病原菌革兰氏染色呈阳性,透射电镜负染观察菌体球形或卵圆形,直径0.6~1.0μm,多数呈链状排列。组织学病变主要表现为全身多组织、器官水肿,出血、变性、坏死以及炎症反应,特别是肝、脾、肾和脑分别表现为肝炎,脾炎,间质性肾炎和脑膜炎。超微结构观察发现病鱼肝、脾、肾、脑、心肌和骨骼肌等器官的细胞超微结构都有较为严重的破坏,细胞核畸形,染色质浓缩或边集,粗面内质网囊泡化及脱粒,线粒体肿胀,嵴断裂或溶解消失。研究表明,海豚链球菌能造成罗非鱼全身性组织器官病变,致使器官功能障碍,正常生理代谢调节紊乱,最后导致死亡。     

尼罗罗非鱼无乳链球菌病的病理学研究

为了解尼罗罗非鱼感染无乳链球菌后各组织的病理变化,运用革兰氏染色和电镜负染技术对一株从自然发病的尼罗罗非鱼上分离的无乳链球菌进行形态观察,采用组织切片和超薄切片电镜技术对患病尼罗罗非鱼的肝脏、脾脏、肾脏、脑、心肌、骨骼肌、肠、鳃等8种组织进行病理学研究,探讨该病的致病机理。结果显示,革兰氏染色呈阳性,负染后透射电镜观察多数细菌呈链状排列;组织病理学变化主要是各内脏器官的广泛充血、水肿、变性和炎性细胞浸润,严重的细胞坏死;超微病理显示,大量球菌侵染脾脏等内脏组织,破坏细胞结构和各种细胞器;细胞界限模糊,细胞核畸形,线粒体肿大,嵴断裂,溶解;粗面内质网肿大、核糖体脱落;细胞质空泡化严重;心肌和骨骼肌纤维断裂、紊乱、肌节长短不一;肠微绒毛排列不整齐、长短不一;眼中有纤维性沉积。研究表明,无乳链球菌能造成尼罗罗非鱼全身性组织器官损害和炎症反应,尤其是肝脏、脾脏、肾脏和脑等重要器官功能障碍和衰竭,最后导致鱼体死亡。     

Endocrine and gonadal changes during the annual reproductive cycle of the freshwater teleost,Stizostedion vitreum

The annual reproductive cycle of walleye (Stizostedion vitreum) was characterized by documenting changes in gonadal development and serum levels of estradiol-17β (E₂), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P), and 11-ketotestosterone (11-KT) in wild fish captured from upper midwestern lakes and rivers throughout the year. Fish from the populations used in this study spawn annually in early- to mid-April. Walleye showed group synchronous ovarian development with exogenous vitellogenesis beginning in autumn. Oocyte diameters increased rapidly from ∼ 200 μm in October to ∼ 1,000 μm in November, and reached a maximum of 1,500 μm just prior to spawning. Changes in gonadosomatic indices (GSIs) paralleled changes in oocyte diameters. Serum E₂ levels in females increased rapidly from low values in October (< 0.1 ng ml⁻¹) to peak levels of 3.7 ng ml⁻¹ in November, coinciding with the period of the most rapid ovarian growth. Subsequently, E₂ levels decreased from December through spawning. Serum T levels exhibited a bimodal pattern, increasing to 1.6 ng ml⁻¹ in November, and peaking again at 3.3 ng ml⁻¹ just prior to spawning. We detected 11-KT in the serum of some females at concentrations up to 5.6 ng ml⁻¹, but no seasonal pattern was apparent. In this study (unlike our results in a related study) 17,20-P was not detected. In males, differentiation of spermatogonia began in late August, and by January the testes were filled (> 95% of germ cells) with spermatozoa. Mature spermatozoa could be expressed from males from January through April. GSIs ranged from 0.2% (post-spawn) to 3.2% (pre-spawn). Serum T levels rose from undetectable levels in post-spawn males to 1.6 ng ml⁻¹ by November, remained elevated throughout the winter, and peaked at 2.8 ng ml⁻¹ I prior to spawning. Levels of 11-KT in males remained low (< 10 ng ml⁻¹, from post-spawning through January, then increased significantly by March and peaked just prior to spawning at 39.7 ng ml⁻¹. Our results indicate that vitellogenesis and spermatogenesis are complete or nearly so, in walleye by early winter, and suggest that it may be possible to induce spawning in this species several months prior to the normal spawning season by subjecting fish to relatively simple environmental and hormonal treatments.     

Seasonal variations in energy and biochemical components of an edible gastropod, Turbo sarmaticus (Turbinidae)

Protein, lipid, ash, moisture and energy contents were determined for four size classes of Turbo sarmaticus every second month for a year. Protein was the major component and was negatively correlated with carbohydrate and lipid and positively correlated with energy and gonadosomatic index values. Lipid values were positively correlated with temperature. Seasonal changes in energy and biochemical components of faeces were also monitored and faecal lipid and ash values were positively correlated with temperature.