Maturation and Spawning of the White Shrimp Penaeus schmitti Burkenroad, 1936, Under Large Scale Rearing Conditions

This paper describes the reproductive performance of Penueus schmitti kept under controlled conditions in a maturation facility of a commercial shrimp farm. A total of 369 females and 368 males of wild P. schmitti were used to form 9 broodstock groups. Unilateral ablation was performed on females only. Although females were not tagged, the total number of mated females ( N = 533) indicates that rematuration of the ovaries did occur. Only 9 mated females (1.69%) did not spawn and only 22 mated females (4.20%) of the remaining 524 cases did not produce viable spawns. These results indicate that a large number of viable spawns (94.18%) can be expected from P. schmitti . A minimum latency period of 6 days for the ovaries to attain full development was observed twice. The highest mating frequency occurred between the 46th and 60th days after unilateral ablation, but mating frequency remained above 2% until the 90th day. The average number of nauplii/female/spawn was 78,961 ( N = 524) and the average fertilization rate of the eggs was 73.12% ( N = 297). Usually when the pair of the spermatophores is dislodged from the thelycum of the mated female, a small sperm mass still remains between the third pair of walking legs. This condition did not show any negative effect on the fertilization rate of the eggs and nauplii production. Mating behavior displayed by P. schmitti is also described and includes three distinctive phases: a) chasing, b) mating and c) post-mating chase.     

Reproductive season and female maturity size of coconut crab <Emphasis Type="Italic">Birgus latro</Emphasis> on Hatoma Island,southern Japan

Information about reproductive season, size at sexual maturity and size-dependent reproductive potentials is important for efficient resource management. Such information is necessary to determine seasonal closures and minimum legal size limits. To conserve resources of coconut crab Birgus latro, which are in danger of extinction due to excessive exploitation, their reproductive season, female size at functional maturity and relationship between female size and reproductive potentials were investigated. The reproductive season started in early June and ended late August, and females with higher reproductive potentials showed a tendency to spawn early in the reproductive season. The prohibition of exploiting the resources during the reproductive season, especially early in the season, would be appropriate for sustainability of high reproductive outputs. Fifty percent of investigated females matured functionally at 24.5-mm thoracic length (TL). However, the size at which all females reached functional maturity was 32.3 mm TL, and there was a wide variation in the size of functional maturity among individuals. We must determine minimum legal size by taking the variation into account to allow all individuals to mate at least once before they are caught, which may prevent serious depression in reproductive rate and genetic diversity.     

拟目乌贼繁殖行为学的初步研究

拟目乌贼在繁殖期间的行为较为复杂,包括求偶、雄性争斗、交配、雄性陪护、产卵等行为。拟目乌贼在生殖策略上并非"一夫一妻"制,交配时,雄性用第1、2对腕固定雌性的头部,然后用茎化腕将精荚输送至雌性纳精囊内。雌性受精后不久便产卵,拟目乌贼雌性轮流在产卵区产卵。卵白色,半透明,卵群葡萄状,分枝,刚产出的卵短径约1.2cm,长径约2.4cm,拟目乌贼平均产卵量为354枚。     

Effects of breeder reuse on the reproductive potential of the signal crayfish (<Emphasis Type="Italic">Pacifastacus leniusculus</Emphasis> Dana. Astacidae) in culture

The aim of this work was to evaluate the reproductive potential of the signal crayfish (Pacifastacus leniusculus Dana) in the second cycle under culture conditions. The experiment was carried out using 5,653 animals placed in six earthen ponds in August. Three treatments were performed, each in two ponds: breeder reuse (males and females used in the former reproductive cycle), female reuse (new males from the wild and females used in the former reproductive cycle) and new breeders (males and females from the wild). In April, close to hatching, egg-bearing females were transferred to the hatchery. Mortality of the reused breeders (around 30% of females and 41.4% of males) was significantly higher than that of the new breeders (11.4% of females and around 19.5% of males). The proportion of berried females close to hatching was significantly higher for the new ones (77.4% of the initial number), and the percentage of new females with a large quantity of eggs (63.6%) was higher than that of the reused females (25.6 and 20.9%). Differences among the percentages of females without eggs in the new breeders (11.2%) and the rest of the treatments (30.7 and 39.6%) were significant. The reproductive capacity of reused females was not improved by providing new males. Considering the number of females initially stocked into ponds, mean yield per new female was greater than that of the reused females, mainly due to the higher mortality recorded in the reused broodstock. Although the yield that can be obtained using the same breeders in two reproductive cycles drops in the second one, the production was not negligible.     

Is there more in ‘gamete quality’ than quality of the gametes? A review of effects of female mate choice and genetic compatibility on offspring quality

Zygote quality is a major issue in production aquaculture, and has been considered, for example, in terms of lipid content, readiness of the female spawner, potency of the male spawner and other issues. In the mean time, evolutionary biologists have been considering issues of mate choice and genetic compatibility of the parents. This paper gives an overview of the main hypotheses of female mate choice, the reasons for multiple mating of females and their potential effects on offspring quality. I suggest how these ideas, if taken into account in commercial aquaculture, might increase the value added of several species in commercial aquaculture, which is impeded by poor offspring quality. Theoretical and empirical research shows that females in general choose partners actively among different males and that females often mate with multiple males. Both active mate choice and multiple mating improve the quality of the offspring, for example as enhanced survival and growth. Active female choice also occurs at the gamete level, and according to the ‘cryptic female choice hypothesis’, eggs are able to affect which sperm from which male will be fertilized. Several proximate mechanisms regarding how the eggs can affect the sperm have been demonstrated. Improved offspring quality of active female choice, cryptic female choice and multiple mating are all in accordance with the ‘genetic incompatibility hypothesis’. This hypothesis states that the quality of the offspring depends on the degree of intragenomic conflicts due to interactions between maternal and paternal haplotypes, for example as increased immunity against a wider range of pathogens when choosing a mate with different immune‐coding alleles than your own. According to the genetic incompatibility hypothesis, eggs from a particular female are expected to do well when fertilized by a particular male, whereas eggs from the same batch from the same female should do poorly when fertilized by other males. Such sire–dam interactions have been demonstrated empirically. I argue that if such a sire–dam interaction is a general phenomenon, this might have major implications for the commercial aquaculture industry, concerning choice of number of brooders, fertilization method, methods to preserve gametes, spawning protocols and breeding programmes.     

Size-related factors causing individual variation in seasonal reproductive success of fluvial male Dolly Varden (Salvelinus malma)

Abstract– Reproductive activities of individually identified fluvial Dolly Varden ( Salvelinus malma ) were observed during a breeding season in a small stream. Males and females both established dominance hierarchies based on body size. Females spawned from late October to late November, with no apparent peak, and larger females spawned earlier than small ones. Males competed for access to females by adopting two types of mating tactics: pairing and sneaking. The tactic used depended on the male's position in the dominance hierarchy of the breeding group. Seasonal reproductive activity and mating success of males were positively correlated with body size, with only the largest male monopolizing most of the mating opportunities, and the small males were rarely successful in mating. Smaller males, however, lost as much weight as large males during the breeding season. Females preferred the largest male in the breeding group as a mate, while males courted females of any size. It is suggested that the polygynous mating pattern is a consequence of size-related differences in competitive ability among males, and the degree of monopolization is affected by both the temporal distribution and the spawning tactics of the females.     

Reproductive performance and mature gonad morphology of triploid and diploid Black Tiger shrimp (Penaeus monodon) siblings

Sibling harvest age Black Tiger shrimp triploids and diploids of both sexes were reared to reproductive maturity, crossed with wild caught females and males, conditioned for spawning and a comprehensive reproductive performance trial was undertaken. Ovarian development, spawning frequency, fecundity, hatch rate, gonad morphology, male reproductive tracts and thelycum impregnation rates of the wild female × triploid male cross were assessed. After ablation, ovarian development and cycling between wild G₀ diploid and G₁ diploids was not significantly different, whereas G₁ triploids failed to show any signs of ovarian development and cycling, thus resulting in no G₁ triploid female spawnings. There were 10 G₀ diploid female × G₀ diploid male first‐spawnings and 9 G₀ diploid female × G₁ diploid male first‐spawnings, all of which produced viable nauplii. In comparison, there were 7 G₀ diploid female × G₁ triploid male first‐spawnings, none of which produced viable nauplii. The 26 wild G₀ diploid female spawnings had more eggs than the 1 G₁ diploid female spawning. Gonad morphology and male reproductive tract assessments showed impaired reproductive development in triploid gonadal tissues of both sexes (compared with sibling diploids and wild shrimp) to a point where complete maturation had not occurred. The thelycum of 16 wild G₀ diploid females crossed with G₁ triploid males had no visible spermatophore present, suggesting that G₁ triploid males are incapable of developing viable spermatophores and mating with females. This study demonstrates that the triploid females and males are incapable of producing viable gametes and are thus reproductively sterile.     

饲料磷脂对已交配和未交配雌性三疣梭子蟹卵巢发育、组织学和卵黄蛋白原表达的影响

为探讨饲料磷脂对已交配和未交配雌性三疣梭子蟹卵巢发育、组织学结构和卵黄蛋白原基因表达的影响,本研究采用2×2双因子随机区组设计(日粮类型:0%和4%大豆卵磷脂;三疣梭子蟹交配处理:已交配和未交配),共4个处理组,以大豆卵磷脂0%和4%两种人工配合饲料分别投喂交配和未交配两组三疣梭子蟹雌蟹,进行了为期12周的饲养实验。结果显示,无论三疣梭子蟹是否交配,饲料中添加4%大豆卵磷脂可显著增加三疣梭子蟹的卵巢指数,提高血清中卵黄蛋白原、孕酮和雌二醇的浓度,增大卵母细胞直径;同时上调肝胰腺卵黄蛋白原m RNA相对表达量,但无显著性差异,肝胰腺指数呈现出和卵巢指数相反的趋势;交配后的三疣梭子蟹卵巢指数、肝胰腺卵黄蛋白原m RNA表达量显著高于未交配组。组织学观察显示,交配使得三疣梭子蟹卵母细胞沉积更丰富的卵黄颗粒,促进卵母细胞成熟,交配处理对肝胰腺指数和血清中卵黄蛋白原及孕酮的水平无显著性影响。此外,饲料磷脂水平和交配处理的交互作用显著影响了三疣梭子蟹血清中类固醇激素孕酮和雌二醇的浓度。本实验结果显示,饲料中大豆磷脂和交配处理均能促进雌性三疣梭子蟹的卵巢发育,交配处理对卵母细胞成熟的促进作用更为明显。     

盐度升高对中华绒螯蟹几种非特异性免疫因子的影响

采用逐步增盐法, 结合生物酶学测定, 研究了从淡水升高盐度到 7、14、21、28和35对二秋龄雌、雄中华绒螯蟹血清总蛋白、氧合血蓝蛋白含量及碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)、酚氧化酶(PO)活力的影响。结果显示, 随着盐度的升高, 中华绒螯蟹的血清总蛋白、氧合血蓝蛋白含量逐渐降低; AKP活性先略升高, 而后逐渐降低; 与雄蟹的PO活力逐渐降低相比, 雌蟹的PO活力先降低, 当盐度高于21后维持稳定水平; SOD活性先略降低, 盐度高于21被激活。除SOD外, 雌蟹血清各测定指标均显著高于雄蟹(P<0.05)。研究结果表明, 盐度接近或超过28将显著影响中华绒螯蟹3种免疫酶的活性及总蛋白和氧合血蓝蛋白的含量, 进而影响其免疫防御能力。     

黑龙江银鲫的性别控制和无性生殖系的研究

用方正银鲫()×镜鲤()所产生的全雌性后代的一部份幼鱼,投以95％酒精作性诱导剂的配制饲料,使幼鱼性转化为生理雄鱼。转化率在84％以上。此法开始处理的时间是在孵化后16—17天,处理的持续时间为30—40天。3年来,从性转化的生理雄鱼与方正银鲫雌鱼获得了无性生殖系一代,然后再从此一代获得了无性生殖系二代,以此建立了方正银鲫纯系。根据后代形态学指标、染色体数和红血球体积等确定,后代与亲本完全相似,并由此确定方正银鲫的性别决定机制,雌性为XX型,雄性为XY型。     

脉红螺交配后性选择机制

交配后性选择是雌性混交动物中的一种普遍现象,其选择机制较为复杂,是性选择研究领域中的重点和难点问题.脉红螺是我国重要的大型经济贝类之一,繁殖形式为多雌多雄混交模式.为了研究该模式繁殖机制,本研究利用6个微卫星标记及行为学观察对脉红螺3个家系进行父权分析.结果表明,3个家系均存在多父性现象,证实脉红螺繁殖属于真正遗传意义上的雌性混交模式.3个家系中父权比例与父本的6个形态学参数及交配持续时间不存在关联性,但均表现出最先与母本交配的父本其后代比例最高,而最后交配的父本其后代比例最低,表明脉红螺交配后性选择存在最先雄性精子优先受精现象,这一现象符合“topping off”假说,即最先交配的雄性排放了大量精子占据了受精囊的主要空间,导致其子代的比例最高;而最后交配的雄性由于受精囊空间的限制,其精子占据空间最少.本研究为海洋无脊椎动物的交配后性选择机制研究提供重要参考资料.     

Biochemical composition of pond-reared and lake-stocked Chinese mitten crab Eriocheir sinensis (H. Milne-Edwards) broodstock

The morphological characteristics, tissue indices, proximate and fatty acid compositions of hepatopancreas, gonad and muscle of pond‐reared (PR) and lake‐stocked (LS) Eriocheir sinensis broodstock were compared. Lake‐stocked crabs are characterized by a blue carapace, white abdomen, golden legs and yellow setae while PR crabs have a brown carapace, grey abdomen, black legs and similar yellow setae. The carapace length and width of PR crabs were significantly less than those of LS crabs of the same wet weight (WW). The results showed that the hepatosomatic index (HSI) of PR males was significantly higher, but the gonadosomatic index (GSI) was significantly lower for PR females when compared with LS individuals of the same sex. Regardless of their origin, the muscular index (MI) of males was higher than that of females. The hepatopancreas of LS crabs had higher protein levels and lower lipid levels compared with PR crabs. The results of proximate analysis of male gonads from two different sources were similar, while the protein level in the ovary of LS females was higher than that of PR females. The tissues of males had higher water content but lower lipid and protein levels compared with females regardless of their source. The LS crabs had higher highly unsaturated fatty acid (HUFA) levels than PR crabs in their gonad and hepatopancreas. In conclusion, our results suggest that the nutritional quality of LS crabs is better than that of PR crabs, the nutritional quality of males is poorer than that of females. The reproductive performance and larval quality of crabs from these two rearing systems should be further verified.     

Effect of dietary soybean lecithin on reproductive performance of Chinese mitten crab Eriocheir sinensis (H. Milne-Edwards) Broodstock

The effect of increasing levels of dietary phospholipids (PL) on the ovarian development and reproductive performance of Chinese mitten crab Eriocheir sinensis were investigated using four semipurified formulated diets supplemented with 0%, 1.2%, 2.4%, and 3.6% PL. Four groups of 40 females, with an average individual body weight of 95–120 g, were fed the experimental diets for a period of 7 months. Male crabs were introduced into the female rearing system in March, and mating, spawning, and egg hatching occurred in the following month. After 10 weeks of feeding, females fed the diet with 2.4% PL had a significantly higher gonadosomatic index (GSI) than females fed the diet with 0% PL, whereas females fed the diet with 1.2% PL had a significantly higher hepatic moisture content and lower hepatic lipid content than the other groups (P < 0.05). After mating, the spawning rate was higher among females fed diets with 3.6% and 2.4% PL (95% and 92%, respectively) compared with females fed diets with 0% and 1.2% PL (both 81%). The results showed that egg production (total number of eggs/female) and fecundity increased with increasing dietary PL level, with females fed diets with 0% and 1.2% PL supplementation having significantly lower values than females fed the diet with 3.6% PL (P < 0.05). In conclusion, our results suggest that dietary PL supplementation has a positive effect on ovarian development and reproductive performance of E. sinensis broodstock. Further study should aim to investigate the optimal PL level in the broodstock diet of E. sinensis in respect to offspring quality.     

The effect of darkness on mating and pleopodal egg production time in a freshwater crayfish, <Emphasis Type="Italic">Astacus leptodactylus</Emphasis> Eschscholtz

In the present study, the effect of darkness on the timing of mating and pleopodal egg production in Astacus leptodactylus was investigated. Crayfish were exposed to three different light regimes: natural day light regime (control, mean 10.04-h light/13.96-h dark); 24-h dark (24 h D); 8-h light/16-h dark (8 L:16 D). Experiments were carried out between November 2006 and January 2007 with 36 males and 144 females. The results showed that darkness did not have an effect on the onset of mating and pleopodal egg production in the groups, but it did affect significantly the timing of individual matings; the higher percentage of ovigerous females in the darkness group at the first observation means that on average females under this condition mated and spawned earlier than in the other groups (P < 0.01). The percentage of ovigerous females exposed to constant darkness in the first observation in which crayfish started to mate and spawn was 62.50. These figures for those exposed to 16 D:8 L and control were 43.75 and 37.50%, respectively. Therefore, it can be concluded that the reproduction efficiency (i.e., rate of ovigerous females) of A. leptodactylus can be enhanced under controlled conditions by exposing broodstock to constant darkness in their mating and spawning season.     

Sperm maturation and capacitation in the open thelycum shrimp Litopenaeus (Crustacea: Decapoda: Penaeoidea)

Transmission electron microscopy was applied to sperm removed from males and females belonging to Litopenaeus vannamei, L. stylirostris and L. occidentalis. It was discovered that a region named filamentous meshwork (FM), located between the nucleus and the hemispherical cap, develops differently in these three closely related species. In L. vannamei, the FM is synthesized in the male reproductive system, but seems to complete its formation after mating. In L. stylirostris, the FM region was not present in spermatophores collected from males or in sperm from the thelycum. In L. occidentalis, the FM region is fully developed in male sperm. It is suggested that completion of the FM is required for acrosome maturation, and the process continues after mating in some species of Litopenaeus. In vitro induction of the acrosome reaction in sperm from males and females of L. occidentalis demonstrated for the first time that reactivity is significantly superior in sperm cells that have been attached to the open thelycum for some hours, as compared to sperm in males (prior to transfer). This finding suggests that matured sperm cells of L. occidentalis become capacitated to react against egg water after mating.     

Maturation and Reproduction of Pond-Reared Penaeus schmitti

Penueus schmitti broodstock was grown from postlarvae in a three-stage semi-intensive pond system. Mean weight after 10.5 mo was 51.2 g for females and 33.8 g for mnles. Reproductive response was evaluated in two studies. The first study was conducted with unilaterally ablated or unablated females and males with ejaculated or non-ejaculated spermntophores. The best response was achieved with ablated females and with non-ejaculated males (0.87 spawas/maturation tank per d and 22.254 nauplii/maturation tank per d). The second study compared the reproductive response of captive ablated females mated with pond-reared males or wild males. More nauplii were produced from wild males (78,583 nauplii/maturation tank per d) than from pond-reared males (57,777 nnuplii/tank per d). The reproductive culture cycle of P. schmitti has been closed for the first time in Cuba on a commercial scale with the collection and stocking of postlarvae of the F₁ generation.     

Reproductive roles predict sexual dimorphism in internal and external morphology of lake whitefish,Coregonus clupeaformis

Abstract – The different reproductive roles of the sexes can predict the direction and magnitude of sexual dimorphism of external and internal morphology. Males should have enlarged structures that enhance the acquisition of mating opportunities, whereas females are predicted to have enlarged organs that are associated with the production of eggs. We tested these predictions in male and female lake whitefish, a species in which both sexes have similar overall body size and shape. After controlling for body size, male lake whitefish had significantly longer jaws and pectoral and pelvic fins, larger hearts, and more muscle than females. Sexual dimorphism in relative muscle mass may be one of the most fundamental morphological differences between males and females. Females had relatively heavier livers than males. Because the liver is important for the breakdown of fats and vitellogenesis, selection should favour an enlarged liver in females for the processing of energy and the production of large numbers of eggs.     

Evaluation of various hCG treatment strategies applied to domesticated pikeperch (Sander lucioperca) broodstock on nest-spawning performance

The aim of the present study was to evaluate the effects of hCG injections on reproductive efficiency by hCG treatment in both male or female brooders of domesticated pikeperch (Sander lucioperca) in the first generation. The study consisted of four treatments based on hormone injection to male or female brooders including T1: both sexes were injected, T2: only females were injected, T3: only males were injected, and T4: without hormone injection. Each treatment which included 14 males and 12 females were introduced to a single rectangular concrete tank with one spawning nest for each mate (a total of 12 nests per tank). Fish were injected by a single dose of 200 IU/kg hCG before transferring to mating tanks. After mating, nests containing fertilized eggs were transferred to circular concrete tanks for incubation and hatching of embryos. According to the results, treatments T3 and T4 did not respond to hormonal stimulation and no fish were spawned. Treatments T1 and T2 showed a positive response to hormone injection. Latency time, fertilization rate, and hatching rate showed no significant difference between T1 and T2 (P?>?0.05), but the number of responded females was significantly higher in T2 (P?<?0.05). The results of the present study demonstrated that it is possible to perform the semi-artificial propagation of domesticated pikeperch via injecting with 200 IU/kg hCG just to females, without the need for hormonal stimulation for males.

     

Control of Reproduction of the Shrimp Penaeus kerathurus Held in Captivity

The control of the reproductive cycle of the shrimp Penueus kerathurus , held in captivity from early juvenile stages without eyestalk ablation, was attempted in two sets of experimental conditions during two successive years. In the first set of experiments, light regime, sex ratio and presence of sand substratum were assessed in relation to ovarian maturation and successful mating. Examination of thelyca obtained from cast exoskeletons showed that 40–82% successful mating had taken place. A sex ratio of 2:l female/male gave a higher percentage of fertilized females than a ratio of 1:l. The induction to full ovarian development was observed for every treatment except the tank without sand substrate, where no mated females were observed.
In the second set of experiments, the role of diet, in particular the role played by a polychaete Nereis diversicolor , was assessed as a nutritive stimulator to induce maturation and spawning. With the same purpose, a parallel experiment in smaller aquaria was also conducted to assess the relative importance of mussel, squid, ragworm and crab and four composite diets consisting of two or three of the said food organisms. Nereis worm seemed to have a determinant role on the induction of shrimp ovarian maturation and spawning. The possible role of its fatty acids on shrimp reproduction is discussed. The experimental results suggest the possibility for extended control of the reproductive cycle of P. kerathurus in a controlled environment provided that proper food is available.     

Is cod lekking or a promiscuous group spawner?

The mating system of cod ( Gadus morhua ) has been described as promiscuous with few options for exercising mate choice. We, on the other hand, argue that cod fulfil the prerequisites of a conventional lekking mating system. A review of papers on cod mating behaviour suggests that mature males aggregate and possibly defend small territories on the spawning grounds, where male–male interactions are common. Females visit males at the aggregations when ready to spawn and males show an extensive courtship display including dance, fin display, and acoustic calls. This may allow females to discriminate between males and both fin size and mass of drumming muscles, the cod's acoustic organ, are related to a male's fertilisation potential. This, together with the presence of sexual dimorphism in drumming muscles, suggests that sexual selection by females is at work. Different courtship display combined with different mate preferences may be important premating mechanisms reducing or preventing interbreeding between groups of cod.