Flagellar setae of the second antennae in decapod shrimps: sexual dimorphism and possible role in detection of contact sex pheromones

Summary

The antenna 2 (antennal) flagella of decapod shrimps are chemotactile, and their setae are proposed as sensilla involved in recognition of females by males via a contact sex pheromone on the surface of the female. Male recognition of females receptive to mating occurs in many caridean species upon contact of male antennal flagella with the surface of a newly molted parturial female. The hypothesis of sexual dimorphism in the number and kind of setae on the antennal flagella of four caridean and one penaeid shrimp species was tested with setal counts and observations on setal morphology. Unique male antennal setae (“male-specific sensilla”) were not identified in any of the species investigated. However, the abundance of antennal setae was significantly greater in males than in breeding females in the palaemonid carideans Palemonetes pugio and Macrobrachium ohione. In the hippolytid caridean Thor manningi and alpheid caridean Alpheus normanni, no sexual dimorphism in setal abundance was demonstrated. In the penaeoid Rimapenaeus similis, males had a higher abundance of antennal setae than the larger breeding females but so did juvenile females, similar in size to males. The sexual dimorphism in antennal sensilla in the palaemonid species and its absence in A. normanni might be related to their different mating systems, but no such association is suggested for T. manningi and R. similis. Setal morphology suggestive of chemoreceptive function (a terminal pore) was observed in all species.     

高亚硝酸盐环境下不同生长速率凡纳滨对虾肠道微生物多样性研究北大核心

【目的】高亚硝酸盐环境中饲养的凡纳滨对虾(Litopenaeus vannamei),在养殖结束时其生长速率和体重往往差异较大。本研究旨在探讨在高亚硝酸盐环境下饲养的对虾生长速率与肠道菌群结构和功能的相关性。【方法】本研究通过收集高亚硝酸盐条件下快速生长对虾(rapidly growing,RG)、正常生长对虾(normally growing,NG)和缓慢生长对虾(slowly growing,SG)的肠道和海水样品,通过16S rRNA基因测序、线性判别分析[line discriminant analysis(LDA)effect size,LEfSe]等进行分析。【结果】发现SG的细菌群落多样性与RG和NG不同。主坐标分析(principal coordinate analysis,PCoA)分析表明,NG的群落组成与RG比SG更相似。通过LEfSe差异分析发现,RG中火色杆菌科(Flammeovirgaceae)、黄杆菌科(Flavobacteraceae)和浮酶菌科(Planctomycetaceae)的丰度较高,而SG中脱硫弧菌科(Desulfovibrionaceae)、希瓦氏菌科(Shewanellaceae)和弧菌科(Vibrionaceae)的丰度显著增加。【结论】本研究发现,在高亚硝酸盐环境下,肠道微生物群落的氮代谢能力是造成对虾不同生长速度的原因。该研究将为虾的工业化养殖提供指导。     

Infection of adult migratory river shrimps,Macrobrachium ohione,by the branchial bopyrid isopod Probopyrus pandalicola

Abstract. Macrobrachium ohione is a migratory (amphidromous) river shrimp (Decapoda, Caridea) that may be parasitized by the branchial parasite Probopyrus pandalicola (Isopoda, Bopyridae). The parasite disrupts gonadal maturation and spawning in female shrimps, resulting in the total loss of reproduction. Shrimps are usually infected by bopyrid parasites during the late zoeal or early postlarval stages; in this study, we investigated the apparent parasite infection of adult shrimps. We analyzed the relationships between parasite body size (total length) and host shrimp body size (carapace length) to test the hypothesis that parasite infection of adult shrimps occurs during the shrimps' reproductive migrations. The results presented here indicate that infection of adult shrimps is common in M. ohione in the Atchafalaya and Mississippi Rivers, Louisiana, USA. In the two upriver sites sampled, Butte La Rose (BLR) and River Bend (RB), parasite size was not associated with host body size. In these locations, many parasitized adult M. ohione were infected with immature P. pandalicola (40.3% in BLR and 51.2% in RB), indicating that the shrimps were adults at the time of infection. A possible explanation is that when female shrimps enter the estuary to hatch larvae, they molt and spawn another brood. The smaller male shrimps that accompany the females downstream are also assumed to molt and continue growth. The intermediate host of the parasite is an estuarine copepod, and thus the parasite cryptoniscus larva that infects the host shrimp is primarily estuarine as well. Newly molted shrimps have soft cuticles, which may facilitate their infection by parasite cryptonisci. Our conclusion is that most infections of adult shrimps occur during their migration into estuarine waters, the primary habitat of infective parasite larvae, and that host vulnerability is probably increased following host ecdysis.     

Effects of competition and season on survival and maturation of young bank vole females

In territorial microtines intra-specific density dependent processes can limit the maturation of individuals during the summer of their birth. This may have demographic consequences by affecting the number and the age distribution of breeding individuals in the population. Little is known about this process on a community level, though populations of many northern microtine species fluctuate in synchrony and are known to interfere socially with each other. We experimentally studied the influence of the field vole Microtus agrestis on maturation, breeding, space use and survival of weanling bank voles, Clethrionomys glareolus. Two additive competition experiments on bank vole populations were conducted in large outdoor enclosures, half of them additionally housing a field vole population. In a mid-summer experiment low population density and absence of older breeding females minimised intra-specific competition. Survival was not affected by the presence of field voles. Season had a significant effect on both the probability of maturation and breeding of the weanlings. Competition with field voles significantly delayed breeding, and coupled with seasonal effects decreased the probability of breeding. In a late-summer experiment breeding and survival of bank vole weanlings were studied for three weeks as part of a high density breeding bank vole population. Weanlings did not mature at all nor were their space use and survival affected by the presence of field voles. Our results show that competition with other species can also have an impact on breeding of immatures. In an extreme seasonal environment, even a short delay of breeding may decrease survival chances of offspring. Seasonal and competition effects together may thus limit the contribution of year born females to reproductive output of the population. Other studies have shown that adult breeding bank voles suffer lower survival in the presence of field voles, but this study showed no survival effects on the weanlings. Thus it might be beneficial for weanlings to stay immature especially in the end of the breeding season and postpone reproduction to the next breeding season if densities of competing species are high.     

Reproductive strategy of the snapping shrimp Alpheus armillatus H. Milne-Edwards, 1837 in the South Atlantic: fecundity,egg features,and reproductive output

Summary

The family Alpheidae, composed by shrimps of relatively small size, popularly known as snapping shrimps, is the one of the most diverse decapod groups. These shrimps are found worldwide and occur in tropical and subtropical waters, from the intertidal zone to great depths. We investigated reproductive aspects of Alpheus armillatus, in order to gather information on egg production, aiming to enhance knowledge of its reproductive strategies in a population in an intertidal area of the South Atlantic. Ovigerous females were collected under rocks, in May and July 2006 (dry season) and in November 2006 and March 2007 (rainy season). Egg production and reproductive output were analyzed and compared seasonally and during the period of embryonic development. Females measured on average 11.28 mm CL, with a mean of 763 eggs and 0.10 mm3 egg volume. The egg volume of this population was smaller than previous estimates for other species of snapping shrimps, but the mean egg number was higher. The volume of eggs doubled during the incubation period, but despite this increase, no significant loss of eggs was observed. Alpheus armillatus invests on average about 12% of body weight in reproduction. The proportional investment in egg production is significantly higher in the rainy season when compared with the dry season (17.9% vs 4.8%), correlated with higher temperatures and increased food availability at this time. Our results corroborated the hypothesis of a pattern of egg production influenced by environmental conditions and intraspecific variability among the family Alpheidae, as a function of the biogeographic region.     

Application of the Model System of Hormonal Stimulation of the Sturgeon Oocyte Maturation and Ovulation in vitro for Solving Some Fundamental and Applied Problems

The author summarizes the results of many-year application of the model of in vitro sturgeon oocyte maturation for different purposes, such as comparison of gonadotropic activities of different preparations, selection of females for breeding, and studying the effects of different factors in order to improve the breeding technology. Special attention is paid to factors that can affect the results of experiments on hormonal stimulation of in vitro oocyte maturation and ovulation and their interpretation. Two other phenomena are discussed: the inhibitory effect of gonadotropic pituitary hormones on the progesterone-induced in vitro oocyte maturation and the nonhormonal induction of oocyte maturation, further studies of which can elucidate the mechanisms underlying the hormonal regulation of oogenesis in sturgeons.     

Parental investment asymmetries of a globally endangered scavenger: unravelling the role of gender,weather conditions and stage of the nesting cycle

ABSTRACT

Capsule: In Egyptian Vultures Neophron percnopterus, both sexes invested similar parental effort throughout the breeding period. However, there was variation in the degree of intensity of parental care during some stages of the breeding period, suggesting that sex-role specialization exists for some activities.

Aims: To quantify parental care behaviour of Egyptian Vultures for the first time and to examine the role of sex, weather conditions, and stage of nesting cycle on breeding ecology.

Methods: We monitored 15 nests of Egyptian Vultures to analyse parental care investment. We collected data on nine different behavioural parameters/activities per sex, which were recorded throughout the entire breeding period. Variation in parental investment was analysed using generalized linear mixed models.

Results: Females invested more effort in incubation/brooding (61.45% for females and 31.54% for males) and egg turning (0.45?events/h for females and 0.37?events/h for males) while males contributed more to nest material delivery to the nest (0.67?deliveries/h for males and 0.14?deliveries/h for females). Conversely, both sexes invested the same effort in nestling attendance (21.89% for females and 21.21% for males) and food provisioning (0.28?items/h for females and 0.25?items/h for males). Furthermore, parental investment was not affected by weather, especially during critical moments such as incubation/brooding, however, changeover rate was positively related to temperature.

Conclusion: Our results suggest that, in the Egyptian Vulture, one sex is not entirely responsible for a particular task and the compensatory effort of the other mate is required. Finally, our findings indicate that major events such as incubation onset and hatching caused important shifts in the patterns of parental investment.     

Sex-ratio,seasonality and long-term variation in maturation and spawning of the brown shrimp <Emphasis Type="Italic">Crangon crangon</Emphasis> (L.) in the German Bight (North Sea)

Aspects of the reproductive and maturation biology of the brown shrimp Crangon crangon (L.) were studied in various subareas of the German Bight (North Sea). The size-specific sex ratio of C. crangon was examined based on length frequency distribution data. The sex ratio for the smallest size groups at which sex was determined was typically around 0.5, indicating an even ratio between males and females. The proportion of females decreased in the 30–45 mm size range. In length classes larger than 50 mm, the proportion of females constantly increases to 100% at around 60 mm total length. We concluded that sex reversal from male to female may not occur in C. crangon. Size at sexual maturity was determined from the proportion of ovigerous females. Size at maturity (L ₅₀) was estimated as 55.4 and 62.0 mm total length for spring and winter data, respectively. The seasonal spawning cycle was studied over the period 1958–2005. Between mid February and late June and for size classes larger than 65 mm ovigerous shrimps exceeded 80% and reached up to 100% of the females in the population. This period can be seen as the core spawning season. From early August to early December the proportion of ovigerous shrimps in the female population is very low. Interannual differences in the seasonal process are obvious with a dramatic decline in C. crangon reproductive success in the late 1980s. Various options are discussed for the reasons of the decline and recovery of the reproductive performance.     

Control of Gonadal Maturation and Regression by Experimental Variation of Environmental Factors in the Mormyrid Fish, Mormyrus rume proboscirostris

We used spawning, external appearance of the females and in part histology of gonads of the African mormyrid fish Mormyrus rume proboscirostris to evaluate the reaction of the fish to experimental variation of environmental factors. Conductivity changes are sufficient to induce gonadal maturation (decrease of conductivity) and regression (increase of conductivity), respectively. Increase of water level and simulation of rain at constant conductivity values did not induce gonadal maturation and spawning. Neither males nor females of M. rume proboscirostris showed postbreeding refractoriness. Social stress apparently prevented complete gonadal maturation and successful spawning. The females laid on average 364 eggs per fractional spawning; the spawning intervals were 21 days. Hatching rate amounted to about 40% in all experiments taken together.     

Gonad development and sperm motility of the diving beetle Cybister brevis Aubé, 1838 (Coleoptera: Dytiscidae) in response to seasonal changes in Japan

Gonad maturation in wild Cybister brevis Aubé, 1838 from Japan was investigated to determine the physiological mating season. Breeding experiments showed that hatching occurred from May to September, and the peak was observed in July. The gonadosomatic index (GSI) in collected females (ovary development) showed the highest value in May. The GSIs were low in other seasons. On the other hand, the GSIs in collected males (testes and accessory glands) remained at constant values during the experimental period. Interestingly, high sperm motility was exhibited in May and September, whereas it was low in December and March. This indicates the maturation difference between females and males. Females mature only at the beginning of the breeding season (May), but males do so from May to September. This result suggests that males have a wide-ranging maturation period and earlier sexual maturation than females, ensuring a successful fertilization.     

The population ecology of Rattus exulans on Tiritiri Matangi Island,and a model of comparative population dynamics in New Zealand

Abstract

On Tiritiri, a small predator-free island in northern New Zealand, kiore (Rattus exulans) were live and snap trapped in grassland and forest. In both habitats, kiore abundance peaked in late summer/autumn. The increase followed a 3 month breeding season during which females produced two to three litters, each averaging 7 young. During the population decline in autumn and winter, animals lost weight. Few bred in the breeding season of their birth and none lived to breed in a second breeding season, so the population consisted of distinct age cohorts. These patterns may relate to a highly seasonal food supply.

Kiore elsewhere in New Zealand show seasonal breeding, but the length of breeding, sexual maturation, and litter size vary. Other studies of kiore in the Pacific show less marked seasonal fluctuations, longer breeding seasons, and smaller litters. We propose a model to explain the variation in rodent demography in New Zealand. The model is based on the seasonal availability of food, along with the modifying influences of predation and dispersal.     

A male fitness advantage to wing reduction in the oriental chinch bug,Cavelerius saccharivorus okajima (heteroptera: Lygaeidae)

A male fitness advantage to wing reduction was investigated for the oriental chinch bug, Cavelerius saccharivorus, which is wing dimorphic. Field surveys for the frequency of matings between wing morphs showed that the mating probability was much higher in brachypterous males than in macropterous males in the early breeding season. Brachypterous males copulated with not only brachypterous females but also macropterous females in this season. This led to a considerable rate (30%) of insemination of macropterous females just before emigration even in the early breeding season. A rearing experiment for the pre-reproductive period of females revealed that females mated with brachypterous males copulated and oviposited earlier than females mated with macropterous males. These results indicate that there is a fitness advantage to wing reduction in the males of C. saccharivorus in terms of the earlier sexual maturation.     

Practical applications of in vitro propagation: Present situation and future prospects

Abstract

This article surveys the techniques and approaches used in the in vitro propagation of economically important plants. The current state of the art for each major class of plants, namely ornamentals, vegetable and agronomic crops, temperate fruits and forest trees is described. The advantages of vegetative propagation in general and the specific advantages which micropropagation offers in the domestication, breeding and conservation of plants are listed. Specific problems associated with in vitro propagation such as juvenility vs maturation, vitrification, rooting and morphological or physiological variations are discussed.     

Uptake of organic mercury and selenium from food by nordic shrimp Pandalus borealis

Abstract

In an attempt to improve our understanding of the transfer process of organic mercury (mainly methyl mercury) from the prey to the consumer, the uptake of mercury in edible muscle of shrimps, Pandalus borealis, from contaminated mussels used as food supplies was studied. Shrimps bioaccumulated rapidly mercury in their abdominal muscle when submitted to a highly contaminated diet (6 μg Hg g^?1) but biomagnification was not observed and Hg concentration in shrimps never exceeded 1.8 μg g^?1. The assimilation efficiency during the uptake period was estimated to about 42% When shrimps received moderately contaminated diet (2.5–2.9 μg Hg g^?1), a two-stage bioaccumulation process was observed in which mercury concentration began to increase in shrimp muscle after 15 days of contaminated diet and at the end of the experiment it seemed to level off. This process can be represented by a two-compartment conceptual model in which mercury rs first eliminated and/or accumulated in the compartment 1 (digestive organs) and then transferred to the compartment 2 (abdominal muscle) following a mechanism and under conditions not yet clearly understood. The use of selenium biologically incorporated into the diet had no apparent effect on the uptake of mercury     

A review of maturation diets for mud crab genus Scylla broodstock: Present research,problems and future perspective

Study of broodstock maturation diets is important in order to increase the quality of berried females, which indirectly improve the larval quantity in the hatchery production of cultured species. This paper reviewed the studies on the maturation diets for mud crab broodstock, genus Scylla and compared independently to identify their effect on reproductive performance and larval quality. The broodstock is usually caught from the wild and held in the spawning or maturation tank for further use of hatchery seed production. Mud crab broodstock was fed either natural diet, artificial diet or mixed diet. Trash fishes were commonly used as a natural feed for mud crab broodstock; meanwhile artificial diets are from formulated fish meal and various kinds of feed. The results indicated that mud crab broodstock has a high dietary requirement for lipids, fatty acids and protein which are to be used during the maturation and breeding processes. However, the natural diet produce better larval quality compared to the artificial diet. The mixed diet is the better diet which resulted in better reproductive performances such as growth, survival, fecundity and maturation processes. This review also discusses the problems in the previous studies for the potential future research to develop very high quality and cost-effective formulated diet for the enhancement of broodstock and seed production technology. Information from this review can be useful in developing a better quality of crustacean broodstock’s diet for commercial hatchery production.     

The timing of gonadal development and moult in three raptors with different breeding seasons: effects of gender, age and body condition

Differences between species in breeding seasons are thought to be mediated through differences in their reproductive physiology. Little is known about how the timing and duration of gonadal maturation varies between raptor species, how the timing of moult relates to the gonadal cycle, whether the timing and degree of sexual maturation varies between juveniles and adults or whether body condition has a significant effect. To address these questions, data on gonadal size and moult for adults and juveniles of both sexes of three raptor species were extracted from the Predatory Bird Monitoring Scheme (based on birds found dead by members of the public). The three species, Sparrowhawk Accipiter nisus, Kestrel Falco tinnunculus and Barn Owl Tyto alba, have different ecologies – diurnal bird predator, diurnal mammal predator and nocturnal mammal predator, respectively. All are single‐brooded but have different breeding seasons. The duration of gonadal maturation was markedly different between the species. Barn Owls showed the earliest maturation and the latest gonad regression, and Sparrowhawks the latest maturation and earliest gonad regression. Kestrels were intermediate. In males of all species, the testes remained fully mature throughout their respective breeding seasons. In females, the ovaries remained partially mature throughout the breeding season. Moult started slightly earlier in Sparrowhawks than in Kestrels and coincided with gonadal regression in the two species. Although females of the two species started to moult earlier than males, moult duration was similar between the sexes. Barn Owls showed no distinct annual pattern of moult. In juveniles of all three species, the gonads were smaller than in adults throughout spring and started to mature later. Gonad size in birds that had starved tended to be smaller than in birds dying from other causes, but did not influence the difference in gonad mass between adults and juveniles and between seasons. Body condition had no effect on moult. Whilst ecology has led to the evolution of different breeding seasons, differences between species, and between adults and juveniles, are mediated through adaptive differences in their reproductive physiology.     

The importance of traditional farmland areas for steppe birds: a case study of migrant female Great Bustards Otis tarda in Spain

A detailed knowledge of the habitat requirements of steppe birds living in farmland habitats is necessary to identify agricultural practices compatible with their conservation. The globally threatened Great Bustard Otis tarda is a partial migrant in central Iberia, but factors affecting its winter habitat use have not been identified. We assessed habitat differences between breeding and wintering areas and winter habitat selection of radiotagged migrant female Great Bustards in central Spain. Of 68 tagged females, 35% moved to wintering areas located 64.3 ± 24.0 km south of their breeding areas, and 80% wintered in a single area of c. 236 km². A census of the population in this area identified it as one of the most important wintering areas of this species in the world, holding c. 1500 individuals. There were significant differences between breeding and wintering habitats of individually marked migrant females. Compared with breeding areas, wintering areas of migrant females were located further from roads and urban nuclei, had lower human population densities and area of urban developments, and a higher diversity of land‐use types, with less cover of cereals and more vineyards and olive groves. Within this area, radiotracked migrant females preferred sites with more vineyards and a lower land‐use diversity. Our results highlight the importance of traditional Mediterranean dry farmland mosaics, and suggest that different conservation strategies are needed for migrant and resident populations in winter to secure the conservation of suitable wintering habitat for Great Bustards in the Iberian Peninsula.     

Notes on the reproductive biology of brachiopods from southern New Zealand

Abstract

The gonads of Notosaria nigricans, Terebratella inconspicua, T. ronguinea, Liothyrella neozelanica. and Neothyris ienticuiaris from southern New Zealand are described and their breeding state is determined. Attempts to induce spawning were not successful even with individuals that appdatred ripe. Sinlce normal fertilisation did not take place even with stripped gametes, it is concluded that either the brachiopods examined were not fully ripe or some indeterminate factor was inhibiting normal development of the zygotes.     

Bobcat Spatial Distribution and Habitat Use Relative to Population Reduction

Abstract Understanding interactions among bobcats (Lynx rufus) may lend insight into less understood life history traits of the bobcat and improve management of the species. Moreover, data from manipulative experiments pertaining to bobcat ecology are largely absent from the scientific literature. Therefore, we investigated bobcat spatial organization and habitat use after an experimental population reduction on an 11,735-ha study site in southwestern Georgia, USA. In response to an approximate 50% population reduction, male bobcats shifted their space use (26.4 ± 1.7% more shift relative to baseline) more (F_1,3 = 138.08, P=0.001) than males where no bobcat removal occurred (28.1 ± 5.5% less shift relative to baseline). Dispersion of radio locations for all female bobcats increased following the population reduction; however, females that were exposed to the removal of a potentially interacting male remained more (F_1,14 = 6.78, P = 0.021) static (increase in dispersion = 7.8 ± 7.3%) than females that were not exposed to removed males (increase in dispersion 41.2 ± 11.1%). Male bobcats likely shifted their central tendency to increase breeding opportunities, whereas the difference in dispersion of female radio locations may be the result of decreased intraspecific competition. Alternatively, reduced dispersion of females following harvest of neighboring males may increase the likelihood that remaining males will interact with females for breeding purposes. Neither habitat use nor habitat selection differed as a function of removal, suggesting that density-dependent habitat selection was not occurring on our study site. Although it is generally accepted that male bobcats use space to increase breeding opportunities, our study suggests that male bobcats may also influence space use of females, but in counterintuitive ways. Because bobcat movements are altered by harvest of neighbors, we suggest that inferring habitat quality for bobcats based on their space use patterns should be avoided unless researchers incorporate knowledge of both short- and long-term population perturbations.     

Analyses of zebrafish and Xenopus oocyte maturation reveal conserved and diverged features of translational regulation of maternal cyclin B1 mRNA

Background  

Vertebrate development relies on the regulated translation of stored maternal mRNAs, but how these regulatory mechanisms may have evolved to control translational efficiency of individual mRNAs is poorly understood. We compared the translational regulation and polyadenylation of the cyclin B1 mRNA during zebrafish and Xenopus oocyte maturation. Polyadenylation and translational activation of cyclin B1 mRNA is well characterized during Xenopus oocyte maturation. Specifically, Xenopus cyclin B1 mRNA is polyadenylated and translationally activated during oocyte maturation by proteins that recognize the conserved AAUAAA hexanucleotide and U-rich Cytoplasmic Polyadenylation Elements (CPEs) within cyclin B1 mRNA's 3'UnTranslated Region (3'UTR).