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1.
Crab guarding behaviors are influenced by the biological and physical characteristics that each population experiences in a particular habitat. We studied post‐copulatory guarding behavior and the factors affecting it, such as the presence of burrows, female receptivity duration, operational sex ratio (OSR) and male size, in two different populations of Neohelice granulata: Mar Chiquita coastal lagoon (MCL) and San Antonio Oeste (SAO). Laboratory experiments showed that post‐copulatory guarding duration varied between the study areas. In MCL, it depended upon the presence of burrows and female receptivity duration, whereas it was independent of the OSR and male size. In SAO, it was dependent upon the OSR and female receptivity duration, whereas it was independent of the presence of burrows and male size. Thus, N. granulata males display different reproductive strategies related to their post‐copulatory guarding behavior pattern in different habitats. These strategies are related to the fact that this species constructs and defends a burrow that provides shelter and a place to mate, something that other varunids do not have.  相似文献   

2.
Mating behavior strategies of brachyuran crabs are flexible depending on the habitat and social context. We evaluate pre-copulatory guarding in Neohelice granulata and describe the unusual copulatory behavior. Laboratory experiments were conducted to test whether factors such as male size, presence of burrows, a male-biased operational sex ratio (OSR) and female mating history affect the copulation duration in two different study areas. Females initiated a searching behavior approximately 20–26 h before they became receptive by assessing large male burrows and displaying a courtship behavior (“flirting”) in its entrance. Once the female entered inside the male burrow, pre-copulatory guarding was observed until the female became receptive and successful copulation occurred immediately after. This species shows some very unusual copulatory behavior involving eyestalk grasping not seen in any other varunid crab. The copulation duration was independent of male size and the presence of burrows, although it was dependent on the study area, the OSR and the female mating history. Thus, copulation duration is a flexible character in this species which varies with habitat and biological factors such as mating history and sex ratio.  相似文献   

3.
Landing site and market surveys of sharks landed along the Arabian Gulf coast of the United Arab Emirates were undertaken between October 2010 and September 2012 to obtain biological data from this artisanal fishery. Data were collected on the size and sex of 12 482 individuals representing 30 species. Maximum sizes of Carcharhinus sorrah, C. amblyrhynchoides and Hemipristis elongata were extended by at least 300?mm total length (TL) compared with published global maxima. The size at 50% maturity was determined for males of five species and this indicated that the males of smaller shark species (<1 000 mm maximum TL) in the fishery were largely mature. For many species, including Loxodon macrorhinus and Mustelus mosis, overall sex ratios were male-biased, indicating that sexual segregation is likely in those species. Furthermore, sex ratios for several species, such as Rhizoprionodon acutus, showed differences across seasons. Overall, the landings contained a high proportion of juveniles, causing concerns about the sustainability of this fishery. Biological parameters of a number of species differed from those recorded earlier for the region, demonstrating a need for additional local data collection to support the development of management measures.  相似文献   

4.
We employed flow cytometry to assess plasma membrane viability of sperm cells in farmed giant kokopu Galaxias argenteus, an endemic amphidromous New Zealand fish. Specifically, the variables of fish size (TL mm) and weight (grams) were assessed against sperm viability. We found no significant difference (P?G. argenteus. This study shows that flow cytometry is an effective, accurate and rapid method for analysing sperm viability in G. argenteus.  相似文献   

5.
Multiple paternity was assessed in Octopus minor using microsatellite DNA markers. Octopus minor adults were captured in traps and kept in indoor cement ponds. The females spawned after several days. Ten broods (B1–B10), each containing 15 embryos and the maternal octopus, were maintained until the embryos reached the stage at which DNA could be extracted and used for genotyping. Multiple paternity was tested using five microsatellite DNA markers and the results proved the hypothesis that multiple paternity occurs in O. minor (observed in six out of the 10 broods). Analysis with GERUD software gave the minimum number of fathers and showed that four broods were sired by a single male, three were sired by two different males and three were sired by three different males. In brood B10, the number of fathers identified by the single‐locus method was one fewer than that by the GERUD method. Of the six multiple paternity broods, four (66.7%) showed significant skew from equal paternal contributions, which indicated that sperm competition and/or cryptic female choice may be important for post‐copulatory paternity bias in this species.  相似文献   

6.
The deep-water trawl fishery along the KwaZulu-Natal coast of South Africa targets several crustacean species, with the knife (or pink) prawn Haliporoides triarthrus contributing most of the catch. Logbook data of fishing effort and catch between 1988 and 2010 were used to assess the distribution and abundance of H. triarthrus on fishing grounds. Generalised linear models were used to quantify the effects of year, month and depth on catch rates. Standardised trends indicated a general decline in abundance between 1990 and 1998, followed by an increase between 2001 and 2008. Catch rates peaked in March, and they were highest between 200 and 499 m depth. Biological samples collected during commercial fishing were used to assess size and sex composition, growth rates and reproductive activity of H. triarthrus. Females became larger than males and mean carapace length (CL) varied by month. The youngest female cohort appeared in November (modal CL of 25 mm), and dissipated after two years (39 mm). Sex ratios were equal for all data combined, but fluctuated by month and CL. Few reproductively active females were recorded. Length-based methods and the standard von Bertalanffy growth function were used to estimate growth parameters (L∞ and K) of females (40.6 mm CL and 1.06 y–1) and males (35.2 mm and 1.27 y–1) respectively. Our findings were compared with information on H. triarthrus from Mozambican waters.  相似文献   

7.
The composition and apparent social structure of a harem school of sperm whales Physeter catodon (Linnaeus 1758) is described from a mass stranding at Muriwai Beach, New Zealand, 29 October 1974. This school contained a total of 54 female whales accompanied by 17 immature males and a solitary full‐grown bull.

Evidence is provided which supports the contention that sperm whales in this region of the Pacific reach the same lengths at sexual maturity and follow a similar breeding cycle to those found elsewhere in the southern hemisphere.  相似文献   

8.
Survival and reproductive rates in fish are often a function of body size. Consequently, spatial‐ and sex‐specific variation in somatic growth rates can have important consequences for population growth and resilience. We used otolith‐based approaches to estimate geographic‐ and sex‐specific growth rates of yellow‐eyed mullet (Aldrichetta forsteri) collected from 14 estuaries and harbours around New Zealand. Aldrichetta forsteri is an abundant and dominant component of New Zealand's estuarine fish fauna. We extracted otoliths from 511 fish, validated daily and annual increments, and prepared transverse thin sections of otoliths to determine age. “Size‐at‐age” relationships were estimated using both linear‐ and non‐linear (von Bertalanffy) growth models, and model performance was evaluated using Akaike's Information Criterion. Because growth rates of sampled fish were best approximated by linear functions, we used ANCOVA to test the null hypothesis that growth rates of A. forsteri were homogeneous between sexes and among geographic locations around New Zealand. Our analyses suggest heterogeneous growth rates between sexes and among locations. Interestingly, relative growth rates between sexes appeared to vary across separate latitudinal gradients for North Island and South Island. Within each island (but not across islands), female A. forsteri generally grew faster than males at the lowest latitudes; relative growth rates of females declined progressively below males with increasing latitude.  相似文献   

9.
The relationship between diet and feeding activity of intertidal crabs, and environmental cycles (tidal, daily and seasonal), habitat and level of the intertidal zone (high/low) was studied using Neohelice granulata (Brachyura, Varunidae) as a model. This is a semi‐terrestrial burrowing crab occupying different habitats in the Southwestern Atlantic coasts and estuaries from bare low intertidal mudflats to high intertidal salt marshes, and from fine, organic matter rich sediment to very coarse sediment with low content of organic matter. The study was carried out in two contrasting habitats of three sites with diverse sets of physical and biological conditions. Diet and feeding of adult N. granulata were indirectly studied through the proportion of food items and the presence/absence of food in crab stomachs, respectively. This species has a dual mode of feeding: predominantly herbivorous (live plants or plant litter in salt marshes) or deposit feeder (superficial sediment and detritus in mudflats), but the quantity and quality of ingested food varies among habitats and sites. A trend to omnivory (including algae and conspecifics) was detected in relation to low quality of resources. Feeding activity modulated by a complex interaction of factors varied according to spatial and/or temporal changes in some natural cycles. Males and non‐ovigerous females fed preferably after dark and during submersion periods, but also after emersion periods if mudflat sediment remained wet; salt marsh crab feeding is somewhat independent of light and tidal cycles. Ovigerous females almost never fed. Both diet and feeding activity of this crab seem to be flexible traits adapted to different combinations of physical and biological factors.  相似文献   

10.
为探讨星康吉鳗(Conger myriaster)精子的超微结构和形态,应用扫描电镜和透射电镜对星康吉鳗精子结构进行观察。结果表明,精子由头部、中段和鞭毛3部分组成,有其独特的结构,总长度为35.75± 1.15µm。精子头部为新月形,主要由细胞核构成,细胞核内有核泡,无顶体结构。精子头部的质膜内包含单一的线粒体。精子头部长为3.33±0.16 um,头宽为1.12±0.13 um。在精子头部的凸面上,有4条从中段到头端的条纹。精子中段伸出一支根,支根位于精子的中段末端。精子中段长度为0.55±0.05 um,支根长度为1.38±0.08 um、直径为90.48±6.06 nm。精子尾部鞭毛细长,鞭毛横切面呈圆形,无侧鳍,鞭毛的轴丝结构为“9+0”型;一些鞭毛的末端呈现卷曲状,发育机制尚不明确。精子鞭毛长为31.16±1.51µm,鞭毛直径为0.17±0.01µm。通过比较分析发现精子的这些形态学特征不仅表现在星康吉鳗精子,还表现在鳗鲡目其他属的精子;表明是鳗鲡目精子的共同特征。本研究揭示了星康吉鳗精子的形态结构,为突破星康吉鳗人工繁殖技术提供了理论参考。  相似文献   

11.
The fitness of parasitic organisms is strongly driven by their ability to infect potential hosts. Although transmission to a host organism is a key component to the parasitic lifestyle, surviving and reproducing within a host poses additional challenges. Cymothoa excisa is a parasitic isopod that infects Atlantic croaker, Micropogonias undulatus, along the Texas coast and has evolved mechanisms to successfully survive and reproduce within its host. Cymothoa excisa is known to exhibit sex‐change strategies but limited information exists on morphological changes, reproductive output and the timing at which sex change becomes optimal. This study collected Atlantic croaker during a 22‐month survey period and identified parasite prevalence and intensity in the host fish population. Infection rates were constant throughout the year at 19.88% and intensity increased through the season up to a maximum of four parasites. Following collection, isopod morphological parameters were quantified for each life stage (including female, transitional, male and juvenile), identifying shape and size transitions through ontogeny and sex change. Transitional C. excisa isopods only occurred when only one isopod was present in a fish, suggesting that isopods change sex from male to female if they are the first to recruit to an uninfected host. As isopods transition to females they have a large increase in size, legs, and pleotelson (which influence fecundity and anchoring ability), whereas the gonopod, eyes and uropod show a reduction (which are no longer needed for swimming and finding hosts). Data suggest that C. excisa sex change is related to the timing of infection and brood size increases with female size and host size. Therefore, it would be advantageous to be the first isopod to infect a host, as it could change into a female and increase reproductive potential. We discuss hypotheses that could explain the mating behavior of parasitic isopods.  相似文献   

12.
Pagurus hermit crabs have a well‐developed right cheliped (major cheliped) and in some species the major cheliped of males is longer than that of females. This paper describes sex‐related differences in major cheliped length and regeneration pattern of the major cheliped in the hermit crab Pagurus filholi. We also examined the function of the major cheliped in male–male competition. Major cheliped length of males was longer than that of females in P. filholi. Males regenerated larger chelipeds than females at the first molt after experimentally induced autotomy. Body size growth in males of the regeneration group was less than that in intact males of the control group while there was no significant difference in body size growth of females between regeneration and control groups. Major cheliped length was included in the best model to explain the outcome of male–male competition and thus sexual selection appears to be a causative factor in the sex‐related difference of the major cheliped length. Sex‐related differences in the regeneration pattern may reflect differences in evolutionary pressures on males for large major chelipeds and females for large body size.  相似文献   

13.
The composition and social structure of schools of sperm whales Physeter catodon Linn, in temperate latitudes east of New Zealand to longitude 150° W are examined and discussed. The study is based on sightings of about 1,572 animals supplemented by catch data from among this number.

Six major social categories were recognised: solitary males, male pairs, schools of bachelor males, mixed‐sex schools consisting almost entirely of immature animals, harems, and nursery schools. Male pairs probably represent the final stage in the break‐up of bachelor male schools into solitary animals, but the possibility that they could be temporary homosexual associations is considered. The schools of immature animals of both sexes are probably very temporary.

An inverse relationship in male schools between school size and mean body length is demonstrated. Mean testis weights of solitary males and bachelor school males are shown to be significantly different at P < 0.001. No relationship between seminiferous tubule diameter and body length was found for pubertal and mature males, as had been demonstrated by a previous worker.

Some data are presented which support the contention by Best (1969) that sexual maturity in the male sperm whale is attained at body length of about 45 ft (12.6 m), rather than at 36.6–41.0 ft (10.3–11.3 m) as suggested by earlier authors.  相似文献   

14.
Population biology of the amphipod Ischyrocerus commensalis Chevreux, 1900, a facultative commensal of the red king crab Paralithodes camtschaticus (Tilesius, 1815), is here described on samples collected during summers 2005–2009 in Dalnezelenetskaya Bay (Southern Barents Sea, Russia). The studied features included infestation indices, size composition, morphometric, and reproductive parameters of the summer generation. During the studied period, prevalence and mean number of I. commensalis per host were 34.4% and 54.4 ± 3.3 individuals, respectively. The majority of amphipods were found on the host mouth parts, limbs, and gills. The amphipod sex‐ratio was significantly biased towards females (F:M = 1.36:1). The size frequency distributions observed in July and August were similar but in July the proportion of the smallest amphipods (<2.1 mm body length) was two times higher than that in August. All the amphipods with body length >5.1 mm were males or females. Length–weight relationships in female and male amphipods differed significantly, suggesting that females were heavier than the same‐sized males. The females carrying eggs in their brood pouches were the most abundant groups (54.8% in July 2009 and 51.6% in August 2005–2008). The minimal body length of a female which had released juveniles was 7.0 mm in July and 6.2 mm in August. The size at 50% maturity of I. commensalis females was estimated to be 6.58 mm. The number of eggs laid is positively linearly correlated with the size of a female. The proportion of the females with eggs in the latest developmental stage in July was 10 times higher than in August. The differences of biological features in symbiotic amphipods between the July and August may be explained by more intensive reproduction effort in the earlier month.  相似文献   

15.
采用注射外源激素——鲑鱼促性腺激素释放激素类似物(sGnRHa)和人绒毛膜促性腺激素(HCG)的诱导方法,研究了外源激素对条斑星鲽雄鱼精子质量的影响。结果表明:外源sGnRHa和HCG诱导后条斑星鲽精子质量明显提升,主要表现为精液粘稠度大为降低、精液流动性和液化能力增强、精子激活率和快速激活率显著提高、快速活动时间和精子寿命延长。同时,血浆性类固醇激素——睾酮(T)和雌二醇(E2)表达水平明显升高,在96h达到峰值。比较两种激素的诱导效果,以sGnRHa对雄鱼精子质量的改善效果为好,但与HCG无显著差异。本研究表明,缓释激素诱导可有效提升和改进条斑星鲽雄鱼的精子质量,研究结果对条斑星鲽人工繁育具有重要的指导意义。  相似文献   

16.
为了掌握茎柔鱼体型生长变化及其与栖息环境因子的效应关系, 2017年2—4月和6—8月,在东太平洋赤道海域逐月随机采集了3 628尾茎柔鱼样本,进行体质量、胴长的月间变化分析和胴长与海表温、叶绿素a浓度的效应关系研究。结果显示,雌性个体胴长分布范围为163—468mm,体质量分布范围为123—3034g;雄性个体胴长分布范围为171—475mm,体质量分布范围为145—2 681 g。不同月份之间,雌性、雄性个体的胴长和体质量均存在显著性差异,雌雄性个体胴长、体质量均以2月份的最大, 6—8月份的较小。然而,每个月份雌性、雄性个体的胴长分布均为单峰值区间分布。体质量-胴长幂函数关系显示,2—4月份雌雄性个体多倾向于匀速生长、体征较差,6—8月份个体则以负异速生长为主、体征较为良好。雌性、雄性个体胴长与采样海域海表温、采样纬度呈显著的正效应关系,采样海域叶绿素a浓度对雌性胴长产生正效应影响。研究表明,东太平洋赤道海域茎柔鱼体型的月间差异性显著,体型变化与采样海域海表温、采样纬度关系密切,并且雌性体型与海域叶绿素a浓度呈正效应关系。  相似文献   

17.
Associations between scale‐worms and giant mussels are common constituents of hydrothermal vent and cold seep ecosystems, but very little is known about their nature and ecology. Here, we analyze the ecological characteristics of the associations between Branchipolynoe seepensis, an obligate symbiotic polychaete, and their host mytilid mussels Bathymodiolus puteoserpentis and B. azoricus inhabiting hydrothermal vent fields on the Mid‐Atlantic Ridge. Infested mussels generally harbored a single symbiont (<4% had two to six worms). Infestation rate varied from 7.2% to 76.5%, increasing with mussel size, and was significantly lower for B. puteoserpentis. Symbiont density at Lucky Strike ranged between 1071 and 1191 individuals m−2. Female symbiont size was always positively correlated with host size, while only males and juveniles from small mussels showed the same trend. This suggested a relatively long‐lasting host/symbiont association for females and short‐lasting association with successive reproductive migrations for adult males. The sex ratio of symbionts was always biased in favor of females. Males were smaller and more slender than females and had one mode in their size distributions, whereas females typically had three or more modes, suggestive of a longer life span in females. Between 59.1% and 72.2% of mussels had damaged soft tissues with substantially higher incidence of trauma in infested ones, suggesting that symbionts may cause trauma. The symbionts also induce tunnel‐like structures among the ctenidia, indicating fidelity to a particular location inside the host. Based on our data, together with the fact that infested mussels became relatively wider than non‐infested ones, this association is considered parasitic (likely kleptoparasitic). Our data, together with those from previous studies, allowed us to define the main life‐history traits of B. seepensis: (i) the relationship with their host is parasitic, (ii) the association begins at the smallest mytilid size classes, (iii) there is sexual dimorphism in body size, (iv) sex ratio deviates from 1:1 in favor of females, (v) fertilization occurs through temporal pairing and pseudocopulation, (vi) sperm are stored by females, (vii) eggs are large (likely lecithotrophic or with direct development), (viii) females have a longer life span than males, (ix) adult males may be semalparous, undertaking reproductive migrations followed by a short period of pairing and then death, and (x) females have a semi‐continuous iteroparous reproductive cycle.  相似文献   

18.
本研究利用高通量测序技术分析小鼠喂食鲣鱼(Katsuwonus pelamis)鱼油和鱼白酶解液后肠道微生物的多样性、群落组成以及结构的变化,探讨高蛋白、高脂肪饮食对人类健康的影响。研究结果显示:喂食鱼油组小鼠的肠道微生物丰富且多样。在门水平上,对照组和鱼油组的优势菌门为拟杆菌门(Bacteroidetes);鱼白组的优势菌门为厚壁菌门(Firmicutes)。在科水平上,对照组和鱼油组中的优势菌科为Muribaculaceae;鱼白组中的优势菌科为毛螺菌科(Lachnospiraceae)。在属水平上,对照组和鱼油组中的优势菌属为Muribaculum;鱼白组中的优势菌为Lachnoclostridium;对照组、鱼油组和鱼白组小鼠的肠道微生物群落中瘤胃球菌属(Ruminococcus)和拟杆菌属(Bacteroides)等丰度较高。在种水平上,对照组和鱼油组中的优势菌为Muribaculum intestinale;鱼白组中的优势菌为解糖梭菌(Clostridium saccharolyticum)。研究结果证明鲣鱼鱼油和鱼白可以调节菌群结构和组成,增加肠道有益菌,减少病原菌的丰度等。  相似文献   

19.
大菱鲆精子运动特征与精液pH的相关性研究   总被引：1，自引：0，他引：1  
为探究大菱鲆(Scophthalmus maximus)精液质量与pH的关系及甘油对大菱鲆精子激活的影响,本研究通过计算机辅助精子分析系统分析检测了威海和烟台4家大菱鲆育苗场(A、B、C、D)的精子质量。研究发现,不同育苗场的大菱鲆精子活力存在显著的差异,A2A1DCB,精子预测寿命分别为11.7、7.1、6.8、4.6、3.3 min,所取精子的质量的存在显著差异。研究结果发现,大菱鲆精子运动特性与精子活化率相关性显著,其中精子活化率与平均曲线运动速度、平均直线运动速度、平均路径速度、精子头侧摆幅度、精子平均鞭打频率呈显著正相关(P0.05),与运动直线性、运动摆动性、运动前向性等参数无显著相关性;大菱鲆精子运动特性受pH影响显著,精液pH与平均曲线运动速度、平均直线运动速度、平均路径速度、精子头侧摆幅度、精子平均鞭打频率呈显著正相关(P0.05),而与运动直线性、运动摆动性、运动前向性等参数无显著相关性。同时还发现,精子活化率高、寿命长的大菱鲆精液pH偏弱碱性(pH=8.0),即大菱鲆精子适宜在弱碱性环境中活动。除此之外,向激活海水中加入梯度甘油(0.1、1、10、100、500、1 000 mmol/L),发现可以显著提高大菱鲆精子寿命,其中甘油浓度为100 mmol/L时,精子寿命延长至15.17 min±0.29 min,推测甘油在精子激活后可能被精子吸收并氧化分解提供能量。  相似文献   

20.
The food of the snapper, Chrysophrys auratus (Forster), in the Hauraki Gulf was investigated by an occurrence method. The diet was extremely varied and depended on the size of the fish and the food available to it. Variation in feeding occurred during the day, but there was no difference in diet at different times of the year or between male and female snapper.

No evidence was found for the existence of two races of snapper in the Hauraki Gulf. Changes of colouration and behaviour among snapper schooling in the summer appeared merely to be associated with spawning activity.  相似文献   

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