Reproductive strategy of Labeo senegalensis Valenciennes 1842 (Teleostei: Cyprinidae) in the Ouémé basin,Benin

Aspects of the reproductive biology and population structure of Labeo senegalensis were investigated in the Ouémé River between April 2005 and March 2006. Reproductive strategy was investigated using gonadosomatic index, ovarian structure and fecundity. Average size-at-first-maturity (L ₅₀) was estimated at 29 cm TL for females and 25.7 cm TL for males. The average sex ratio (1:0.96) was not significantly different from unity. Oocyte diameter frequency distribution suggests synchronous development with a single total spawning. Absolute fecundity ranged between 12 948 and 74 832 eggs. Labeo senegalensisis a highly fecund fish that presents a seasonal cycle of reproduction from May to October during the rainy season.     

不同大豆品种上红绿两种色型豌豆蚜的种群参数

【目的】探讨不同大豆品种对红绿两种色型豌豆蚜Acyrthosiphon pisum种群参数的影响,为大豆品种的抗蚜性评价及豌豆蚜的预测预报与综合防治提供试验依据。【方法】在光周期10L∶14D、温度23±1℃,相对湿度60%±10%,光照强度212μmol/m~2·s的人工气候箱中,观察和分析4个大豆品种(汾豆牧绿2号、南夏豆25、南黑豆20和南豆5号)叶片上红绿两种色型豌豆蚜的成虫寿命、繁殖和种群生命表参数。【结果】在大豆品种汾豆牧绿2号上,红绿两种色型豌豆蚜成虫寿命均最短,繁殖力均最弱,且红色型豌豆蚜成虫寿命比绿色型长1.07 d,内禀增长率是绿色型豌豆蚜的29.93倍;在南夏豆25上,红色型豌豆蚜成虫寿命比绿色型长2.46 d,内禀增长率是绿色型豌豆蚜的5.86倍;在南黑豆20上,红色型豌豆蚜成虫寿命比绿色型长2.47 d,内禀增长率是绿色型豌豆蚜的1.54倍;在南豆5号上,红色型豌豆蚜成虫寿命比绿色型短0.02 d,内禀增长率是绿色型豌豆蚜的1.41倍。【结论】不同大豆品种对红色和绿色型豌豆蚜种群参数的影响不同,且两种色型豌豆蚜对不同大豆品种适应性反应也不相同。     

The influence of environmental instability on the reproductive strategy of the critically endangered Acıgöl killifish (Aphanius transgrediens)

To investigate the variability in the reproductive tactics of Acıgöl killifish (Aphanius transgrediens), one of the most seriously threatened freshwater teleost species, this study compared its reproductive ecology in two contrasting habitats that differ substantially in terms of stability of environmental parameters, particularly salinity regime (stable vs. unstable). Fish were sampled monthly from October 2013 to September 2014 with the aim of testing whether the reproductive life-history response of fish to stable and unstable conditions differed. The reproductive effort (gonad weight) of both sexes did not differ significantly between the two habitats, but females in the unstable habitat had significantly lower fecundity and larger eggs. The relationship between fecundity and fish size was stronger in the stable habitat, whereas the relationship was quite variable and uncertain in the unstable habitat. Fish born in the unstable habitat reached their first maturity at a smaller size than those in the stable habitat. The gonado-somatic index and the duration of hydrated eggs showed that reproduction continued from February to May in both habitats; nonetheless, a second spawning event occurred during July and August in the unstable habitat, which included the reproductive contributions of YOY individuals and older generations. This study’s results suggest that A. transgrediens employs varying reproductive strategies against environmental instability in its restricted unique range. This may have further implications for the ways in which habitat-specific conservation methods are used.     

From gametogenesis to spawning: How climate-driven warming affects teleost reproductive biology

Ambient temperature modulates reproductive processes, especially in poikilotherms such as teleosts. Consequently, global warming is expected to impact the reproductive function of fish, which has implications for wild population dynamics, fisheries and aquaculture. In this extensive review spanning tropical and cold-water environments, we examine the impact of higher-than-optimal temperatures on teleost reproductive development and physiology across reproductive stages, species, generations and sexes. In doing so, we demonstrate that warmer-than-optimal temperatures can affect every stage of reproductive development from puberty through to the act of spawning, and these responses are mediated by age at spawning and are associated with changes in physiology at multiple levels of the brain–pituitary–gonad axis. Response to temperature is often species-specific and changes with environmental history/transgenerational conditioning, and the amplitude, timing and duration of thermal exposure within a generation. Thermally driven changes to physiology, gamete development and maturation typically culminate in poor sperm and oocyte quality, and/or advancement/delay/inhibition of ovulation/spermiation and spawning. Although the field of teleost reproduction and temperature is advanced in many respects, we identify areas where research is lacking, especially for males and egg quality from “omics” perspectives. Climate-driven warming will continue to disturb teleost reproductive performance and therefore guide future research, especially in the emerging areas of transgenerational acclimation and epigenetic studies, which will help to understand and project climate change impacts on wild populations and could also have implications for aquaculture.     

Temperature and host plant effects on development and fecundity of Brevicoryne brassicae (L.) (Homoptera: Aphididae)

The development, survival and reproduction of the cabbage aphid, Brevicoryne brassicae (L.) were evaluated at three constant temperatures (20, 25 and 30°C) on cabbage, cauliflower, red cabbage, turnip and radish. The development periods of immature stages ranged from 10.7 d at 20°C to 7.60 d at 30°C for red cabbage. Total percentages of survivorship of immature stages varied from 39.40 and 82.50 within the temperature range of 25–30°C on radish. The average progeny per female was 31.15, 28.95 and 23.77 at 20, 25 and 30°C on cabbage.     

Physical size,condition, and demography of chamois (Rupicapra rupicapra L.) in the Avoca River region,Canterbury, New Zealand

Abstract

The physical and demographic characteristics of chamois in the Avoca region are evaluated from 306 animals shot and autopsied between 1975 and 1978. These data are compared with published and unpublished information for chamois populations in Westland and Canterbury. Avoca chamois were large-framed, but weighed less than Westland chamois. The weight difference suggests better habitat condition and food resources for Westland animals, but the large skeletal size of Avoca chamois is unexplained.

High rates of juvenile mortality were caused by acute bacterial-pneumonia infections (Pasteurella). These deaths and other losses by natural causes were offset by the good breeding success of adult females so that stable population numbers were maintained.     

Gonadal maturation,fecundity, spawning,and timing of reproduction in the mud snail,Cerithidea cingulata,a pest in milkfish ponds in the Philippines

Summary

Gonadal maturation, spawning, fecundity and timing of reproduction of the snail Cerithidea cingulata in a brackish water pond in Molo, Iloilo, Philippines, are described. Snails 4–41 mm in shell length were sampled monthly from May 1997 to May 1998; 25% were <25 mm, 67% were 20–30 mm, and 8% were >30 mm. The sexes are separate and could first be distinguished at 15 mm. Males are aphallic, have narrower shells than females of the same length, and have bright yellow-orange testes overlying the digestive gland deep inside the shell. Females have more robust shells, an ovipositor at the right side of the foot, and yellow-green ovaries overlying the digestive gland. The sex ratio was one male to two females in the pond population studied. Gonadal maturation was monitored by means of gonadosomatic index (GSI, gonad weight as a percent of visceral weight); maturation stages were based on the gonad appearance (immature, developing, mature) and histology (immature, developing, mature, redeveloping). GSI increased with snail size, and reached 16% in a 33-mm female. The smallest mature males and females were 18–19 mm, and most snails >20 mm were mature, spawning, or redeveloping. Histological sections showed all stages of gametogenesis in mature male snails. The oocyte size-frequency distributions in mature females showed mostly mature oocytes and secondary oocytes, but also oogonia and primary oocytes. GSI and the frequency of snails at different maturation stages varied over the year. Both GSI and the frequency of mature snails were highest during the summer months, April to August. Nevertheless, mature snails occurred throughout the whole year, as did mating and egg-laying. Fecundity (= number of oocytes >70 pμ) increased with size in mature females 2041 mm; an average 25-mm female produced about 1,500 oocytes and larger females produced a maximum of about 2,500 oocytes. Eggs strings laid on the pond bottom were 45–75 mm long; an average 64-mm string contained 2,000 eggs 210+20 pm in diameter. The density of eggs strings was highest (80–120/m²) during March-September. Eggs hatched after 6–7 d into planktonic veligers, which in turn settle on the pond bottom 11–12 d later as juveniles. Juveniles 2–6-mm long were most abundant in the pond during August-October.     

Life‐History Patterns of Cuban Poeciliid Fishes (Teleostei: Cyprinodontiformes)

The following work provides basic information about the life history of 10 Cuban species of the family Poeciliidae. Adult fish stocks were captured in their natural habitat, and litters obtained from them were raised and maintained in captivity for 19 weeks. For each species, we present the mean value of newborn length (TL_o), age at sexual maturity (AM), total length at sexual maturity (TLM), as well as the patterns of postnatal growth in aquarium conditions, which were described using size–age curves and nonlinear regression equations (Richards model). There are differences in growth dynamics among species. In general, growth rates differ for both sexes in all poeciliids studied, males maturing earlier than females, who reach higher values of total length at the 19th week (TL_f). Sexual size dimorphism could be explained by the specific roles of each sex (fecundity in females and early maturity in males) while differences in growth among species could be related to their distribution patterns in the wild. The data summarized in this contribution can be useful for the conservation of these fish species. Zoo Biol 32:251–256, 2013. © 2012 Wiley Periodicals, Inc.     

Repeated Mating and Female Fecundity in the Simultaneously Hermaphroditic Land Snail Arianta arbustorum

Summary

To evaluate the influence of repeated mating on female fecundity in the simultaneously hermaphroditic, self-incompatible land snail Arianta arbus-torum, the number and size of clutches, egg size and hatching success of individuals from 3 populations were determined under conditions of isolation and grouping during one breeding season in a field cage experiment. Only adult snails which had mated and oviposited in the preceding year were used.

Sperm storage enabled isolated individuals to continue with the production of fertilized eggs. Snails kept singly or in groups differed neither in number of clutches laid nor in egg size. But isolated snails laid smaller clutches than did grouped snails. As a result isolated snails produced fewer eggs per breeding season. Hatching success varied greatly between populations and rearing conditions. In general, isolated snails had fewer hatchlings than grouped snails, indicating that individuals prevented from remating suffered a reduced fitness.