Size Assortative Mating and Reproductive Success of the Funnel-Web Spider, Agelena limbata (Araneae; Agelenidae)

Field observations and laboratory experiments were conducted to assess the relation between male size and reproductive success in the funnel-web spider, Agelena limbata Thorell (Agelenidae), in 2 years. In this species, the body size of males is similar to that of females. In the field, size assortative mating occurred in both years. In 1 year, partial correlation coefficient analysis indicates that male cephalothorax width is a beter predictor of the copulated female cephalothorax width than of the date of pairing. In laboratory experiments, females tended to reject courting males that were smaller in relative body size, and males that were larger in relative body size had greater copulation success. Consequently female rejection of smaller courting males has some contribution to size assortative mating. Since larger females deposited more numerous eggs in the field, larger males are expected to have a higher reproductive success.     

Sexual Dimorphisms in the Dermal Denticles of the Lesser-Spotted Catshark,Scyliorhinus canicula (Linnaeus, 1758)

The dermal layers of several elasmobranch species have been shown to be sexually dimorphic. Generally, when this occurs the females have thicker dermal layers compared to those of males. This sexual dimorphism has been suggested to occur as a response to male biting during mating. Although male biting as a copulatory behaviour in Scyliorhinus canicula has been widely speculated to occur, only relatively recently has this behaviour been observed. Male S. canicula use their mouths to bite the female’s pectoral and caudal fins as part of their pre-copulatory behaviour and to grasp females during copulation. Previous work has shown that female S. canicula have a thicker epidermis compared to that of males. The structure of the dermal denticles in females may also differ from that of males in order to protect against male biting or to provide a greater degree of friction in order to allow the male more purchase. This study reveals that the length, width and density of the dermal denticles of mature male and female S. canicula are sexually dimorphic across the integument in areas where males have been observed to bite and wrap themselves around females (pectoral fin, area posterior to the pectoral fin, caudal fin, and pelvic girdle). No significant differences in the dermal denticle dimensions were found in other body areas examined (head, dorsal skin and caudal peduncle). Sexually dimorphic dermal denticles in mature S. canicula could be a response to male biting/wrapping as part of the copulatory process.     

Population structure and reproductive biology of Atlantoscia floridana (van Name, 1940) (Crustacea, Isopoda, Oniscidea) in southern Brazil

Data were obtained on the population structure and reproduction of Atlantoscia floridana, one of the most common species of terrestrial isopods in the restinga (coastal dune) forests of the state of Rio Grande do Sul, southern Brazil. During a 19-month period, a total of 7833 individuals were sampled: 2792 males, 3400 females and 1691 mancas. There was a significant difference between the size of both males and females collected in 2000 and 2001: the mean size was smaller in the second year when individuals in the larger size classes were lacking. Population density varied with season. The minimum population was 131 ind per m² individuals, the maximum 1040 ind per m² and the mean 450  per m². While the overall sex ratio was clearly female biased, the operational sex ratio favored males, and showed no changes with season. Because both ovigerous and post-ovigerous females were present throughout the year, reproduction is considered continuous; however, reproduction peaked during autumn and spring. Ovigerous females were measured (CW = cephalothorax width) and the number of eggs was counted. Fecundity (F) varied from 5 to 23 eggs ( = 11.18 ± 4) per female, and was expressed by the regression F = –18.48 + 22.59 CW, with the female cephalothorax width varying from 1.04 to 1.68 mm. Marsupial mortality was only 0.9%. Egg production was 588 eggs per m² in spring and 660 eggs per m² in autumn. Recruitment occurred in all months, and eggs, embryos and marsupial mancas were also present year-round. A. floridana is the dominant species of terrestrial isopod in the study area. Its most remarkable characteristic is its high reproductive investment.     

Behavior of symbionts during oogenesis and early stages of development in the German cockroach, Blattella germanica (Blattodea)

In this paper, adaptations and microanatomic changes in the branchial chamber, as well as influence of parasitosis on the reproductive function of shrimp, are analyzed. Probopyrus cf. oviformis was observed in the branchial chamber of shrimps of both sexes, with an infestation rate of 29%. The infestation frequency in relation to sex and size was not uniform, and two trends were observed: a higher frequency in bigger males in contrast to females, with less infestation frequency in older individuals. This aspect was related to changes in the sex ratio of shrimps, infested and noninfested, with the following conclusions: (1) Sexual inversions were not observed in females of P. argentinus; (2) male infestation with P. cf. oviformis showed tertiary sexual rate bias. It occurred because the metabolic parasite-host relationship led to an increase in size. These infested males were incorporated into a normal population characterized by females being bigger than males. The morphological and functional changes observed were (1) branchial chamber reduction, slendering of the cephalothorax lateral wall, together with local injury (oxygen consumption was below the normal values; and (2) the ovaries of infested females of P. argentinus remained stationary in incipient maturity (secondary vitellogenesis was not observed).     

Female choice and the relatedness of mates in the guppy (<Emphasis Type="Italic">Poecilia reticulata</Emphasis>)

Several studies suggest that females may offset the costs of genetic incompatibility by exercising pre-copulatory or post-copulatory mate choice to bias paternity toward more compatible males. One source of genetic incompatibility is the degree of relatedness among mates; unrelated males are expected to be genetically more compatible with a female than her relatives. To address this idea, we investigated the potential for inbreeding depression and paternity biasing mechanisms (pre- and post-copulatory) of inbreeding avoidance in the guppy, Poecilia reticulata. Inbreeding resulted in a reduction in offspring number and quality. Females mated to siblings gave birth to significantly fewer offspring compared to females mated to non-siblings and inbred male offspring took longer to reach sexual maturity. There was no evidence of inbreeding avoidance in pre-copulatory behaviors of females or males. Sexual responsiveness of females to courting males and the number of sexual behaviors males directed at females did not decrease as a function of the relatedness of the two individuals. We also tested whether female guppies can use post-copulatory mechanisms to bias sperm usage toward unrelated males by comparing the number of offspring produced by females mated to two of their siblings (SS), two males unrelated to the female (NN), or to one unrelated male and a sibling male (NS). We found that NS females produced a number of offspring not significantly different than what would be expected if fertilization success were halfway between completely outbreeding (NN) and completely inbreeding (SS) females. This suggests that there is no significant improvement in the number of offspring produced by females mating to both related and unrelated males, relative to that which would be expected if sperm from both males were used equally. Our results suggest that female guppies do not discriminate against closely related males or their sperm.     

Male emergence timing and mating success in the funnel-web spider,Agelena limbata (Araneae: Agelenidae)

Field observations on the relationship between male mating success and emergence timing in the funnel-web spider,Agelena limbata, were conducted.Agelena limbata is an annual species and adult males appear slightly earlier than adult females in July. As males deposit a copulatory plug at the female epigynum after copulation, copulation with virgin females is important to males. The number of copulations in males with virgin females, which strongly correlates with the longevity of males and the number of females that males courted, did not correlate with the emergence timing of males. Early emerged males and females were significantly larger in size than later ones, but the correlation coefficient between the emerged date and the cephalothorax width was not strong. Males that emerged earlier did not have any advantage in copulating with larger and more fecund females. Furthermore, virgin females first copulated on average 7.9 days after their final molt and the mortality rate of adult males increased after the final molt. These factors may favor the smaller degree of protandry in male emergence timing inA. limbata.     

Morphometric characterization of thalassohaline Artemia franciscana populations from the Colombian Caribbean

Aim To establish possible interpopulation relationships among Colombian Artemia franciscana (Crustacea, Anostraca) populations. Location Colombian Caribbean coast (Manaure, Galerazamba, Salina Cero and Tayrona) and a similar thalassohaline reference population from San Francisco Bay (SFB‐USA). Methods Morphometric characters of male and female cultured individuals of A. franciscana were measured. The populations were grouped according to: (1) population type (populations grouped according to two broad regions of origin: North America and the Caribbean coast), and (2) specific geographical origin (populations selected according to five specific local origins: Manaure, Galerazamba, Salina Cero, Tayrona and SFB) and evaluated using forward stepwise discriminant analysis (SPSS, Ver. 10). Results Optimal discriminant variables for males grouped by the type of population were left setae and antenna length, and for females they were abdominal length and antenna length. However, for males grouped by their specific geographical origin, the optimal variables were furca length, left setae, antenna length, eye separation, abdominal width and abdominal length, and for the females, they were furca length, abdominal length, left setae and eye separation. Male and female Colombian Caribbean populations were separated from the North American populations. However, our results show that the classification based on male characters provides better group membership than females. Main conclusions Male morphometric characters separated the type of population groups more clearly than the female characters, because all Colombian populations were correctly positioned in the Caribbean coast region and the SFB population in the North American region, with no overlapping between the two types, as was the case for the female individuals. Likewise, male individuals correctly position the Salina Cero population to its neighbouring Galerazamba population and to the other Colombian populations. In contrast, female individuals from Salina Cero did not cluster with the other Colombian coast populations (Galerazamba, Tayrona and Manaure) or with the SFB population.     

Male Biases for Male Characteristics in Females in Priapella olmecae and Xiphophorus helleri (Family Poeciliidae)

Preexisting receiver biases can affect the evolution of sexually selected traits once traits favored by such biases arise. Female guayacón olmeca, Priapella olmecae , and green swordtail, Xiphophorus helleri , possess a bias favoring sworded conspecific males, despite phylogenetic evidence that the sexually selected sword expressed by male swordtails arose in Xiphophorus after the divergence of the two genera. In this study, we investigated the state of the bias favoring a sword in male Priapella and Xiphophorus to determine whether males also possess a bias that could operate in an intersexual selection context. Male P. olmecae preferred conspecific females with swords to those without swords. Thus, males and females in this unsworded species appear to share a preexisting bias favoring individuals of the opposite sex with swords. Male X. helleri , however, did not express a bias favoring sworded females; instead, in this species in which the sword is restricted to males, males discriminated against conspecific females with swords. Previous work suggests that female mate choice and male–male competition likely contribute to the maintenance of the sword in X. helleri . The sword may also play a role in sex recognition in swordtails. The absence of a sword preference in male green swordtails could reflect the current function of the sword.     

东北林蛙的两性异形和抱对个体的形态相关性

2012年4月,在吉林省长白山地区,对正在抱对的30对东北林蛙(Rana dybowskii)成体的体长、头长、头宽、前肢长和后肢长进行测量,使用统计学的方法分析抱对个体形态特征的两性异形及配偶间形态特征的相关性.结果表明,两性的所有局部形态特征均与其体长呈显著正相关,其中,前肢长和后肢长随体长的增长速率在两性间无显著差异,而头长和头宽随体长的增长速率存在显著差异.雌性成体显著大于雄性成体;特定体长下雄性的前肢显著大于雌性,其他局部特征没有显著的两性差异;雌性个体与抱对的雄性个体的后肢长呈显著正相关,其余形态特征两性间无相关性.因此,在东北林蛙的配偶选择中,雌性对雄性形态特征的选择与两性异形的形成无显著的相关性.     

Effect of host age on life cycle and morphological characteristics of Glyptapanteles liparidis (Hymenoptera: Braconidae), a parasitoid of Acronicta rumicis (Lepidoptera: Noctuidae)

The life cycle of Glyptapanteles liparidis was 23.75 ± 1.26, 21.95 ± 2.44 and 20.83 ± 0.78 days when fed on the first, second and third instar larvae of Acronicta rumicis, respectively. Although insufficient numbers hindered statistical analysis, the life cycle of G. liparidis appeared to be shortest, 19 days, when fed on fourth instar larvae. The life cycle of G. liparidis tends to shorten as the larvae of A. rumicis fed upon are more advanced. The body length, forewing length and head capsule width of female G. liparidis fed on first instar larvae of A. rumicis were greater than those of males, while the antennae of males were longer than those of females. When fed on second instar larvae, there was no difference in body length and head capsule width between males and females, but the male antennae were longer than the female, and the female forewings were longer than the male. When fed on third instar larvae, there was no significant difference in head capsule width between the sexes, but female body length and forewing length were greater than the male, and the male antennae were longer than the female. On the whole, females were bigger than males in terms of body length and forewing length, while antennae of the males were longer than those of the females. There was no difference in head capsule width between males and females. Body length, antenna length, forewing length and head capsule width of male and female G. liparidis were relatively larger when fed on first instar larvae of A. rumicis than when fed on second and third instar larvae.     

Sexual dimorphism of the European Pond Turtle,Emys orbicularis (Linnaeus, 1758), in Anzali Lagoon,Iran (Reptilia: Emydidae)

The morphometric characteristics of the European Pond Turtle, Emys orbicularis, were studied at Anzali lagoon on the southern coast of the Caspian Sea. Males were on average (N=249) with 272.0?g significantly lighter than females with 447.0?g, and average carapace length was significantly smaller (123.0?mm in males, 139.0 in females). Females exceeded males also in all other studied characters (carapace width, plastron length, plastron width, and scute height). The sex ratio of male to female was 1 to 1.03, and the comparison of total tail length and cloaca-tail tip length revealed a difference between the position of the cloaca in both sexes, a character useful for sex determination in this species.     

Sexual dimorphism of guava weevil Conotrachelus psidii Marshall (Coleoptera: Curculionidae)

We investigate structural and behavioral differences between male and female adults of guava weevil, Conotrachelus psidii Marshall, 1922 to help in sex determination. Weevils collected from a commercial guava orchard were individually caged and maintained under laboratory conditions. Every day ten individuals were grouped and their behavior was observed. During mating the males and females were identified. Fifty weevils of each sex were killed and they were observed with stereoscopic microscope. The antenna insertion on the rostrum and hair on the thorax and abdomen surfaces were examined. Length and width of body, pronotum, last abdominal sternite and rostrum were also taken. Behaviorally, the male weevils produce audible sound by stridulation of abdomen while females do not. In the females, the body and pronotum width and body a rostrum length were higher than in the males, but the last abdominal sternite was smaller. Three other structural differences were visible with the naked eye: 1) the anterior region of pronotum have scarce hair or have not in the females and hair is dense in the males; 2) the last tergite of females is hidden by the penultimate tergite whereas in the males is visible; 3) the first abdominal sternite of females is more prominent, very convex and without or with little bristle. In the males it is slightly concave and with abundant hair. The male-female differences found in this work allow, without hurt or change insect behavior, an efficient sex determination of guava weevil.     

Cryptic preference for MHC-dissimilar females in male red junglefowl,Gallus gallus

An increasing number of studies test the idea that females increase offspring fitness by biasing fertilization in favour of genetically compatible partners; however, few have investigated or controlled for corresponding preferences in males. Here, we experimentally test whether male red junglefowl, Gallus gallus, prefer genetically compatible females, measured by similarity at the major histocompatibility complex (MHC), a key gene complex in vertebrate immune function. Theory predicts that because some degree of MHC heterozygosity favours viability, individuals should prefer partners that carry MHC alleles different from their own. While male fowl showed no preference when simultaneously presented with an MHC-similar and an MHC-dissimilar female, they showed a ‘cryptic’ preference, by allocating more sperm to the most MHC-dissimilar of two sequentially presented females. These results provide the first experimental evidence that males might respond to the MHC similarity of a female through differential ejaculate expenditure. By revealing that cryptic male behaviours may bias fertilization success in favour of genetically compatible partners, this study demonstrates the need to experimentally disentangle male and female effects when studying preferences for genetically compatible partners.     

Males adjust their signalling behaviour according to experience of male signals and male–female signal duets

Sexual signals are conspicuous sources of information about neighbouring competitors, and species in which males and females signal during pair formation provide various sources of public information to which individuals can adjust their behaviour. We performed two experiments with a duetting vibrational insect, Enchenopa binotata treehoppers (Hemiptera: Membracidae), to ask whether males adjust their signalling behaviour according to (1a) their own experience of competitors' signals, (1b) how females adjust their mate preferences on the basis of their experience of male signals (described in prior work), and/or (2) their own experience of female response signals to competitors' signals. We presented males with synthetic male signals of different frequencies and combinations thereof for 2 weeks. We recorded males a day after their last signal exposure, finding that (1a) male signal rate increased in response to experience of attractive competitors, but that (1b) male signal frequency did not shift in a manner consistent with how females adjust their mate preferences in those experience treatments. Second, we presented males with different male–female duets for 2 weeks, finding that (2) male signal length increased from experience of female duets with attractive competitors. Males thus make two types of adjustment according to two sources of public information: one provided by experience of male signals and another by experience of female responses to male signals. Signalling plasticity can generate feedback loops between the adjustments that males and females make, and we discuss the potential consequences of such feedback loops for the evolution of communication systems.     

Pampas deer (Ozotoceros bezoarticus) male–female agonistic behavior toward high and low social ranked females

The pampas deer is an endangered species from the southern cone of South America. Although it is breed in confined groups, there is very scarce information on how their social relationships and aggressiveness are regulated in these groups. As we hypothesized that pampas deer males display different behaviors toward high or low social ranked females, we compared the number and pattern of agonistic behaviors used by pampas deer males to displace high- and low-ranked females. We performed focal observations recording all female–female agonistic interactions resulting in the displacement of an animal in six breeding groups (total?=?6 males and 31 females), and calculated the success index for each hind. Then, we recorded all male–female agonistic interactions while animals received food, and compared the total number and the type of interactions used by males to displace high- and low-ranked individuals. Males displaced more frequently high-ranked than low-ranked females (P?=?0.006), mainly by their presence (P?=?0.0004); males tended to displace low-ranked females more frequently by kicking (P?=?0.051). We designed a complementary study to determine if the male–female physical distances may explain that difference. We recorded male–female distances every 5 min for 30 min during 10 days while animals ate ration, and calculated an association index (AI) between each female with the male. Low-ranked females tended to have greater AI accumulated at 5 and 10-min scans (P?=?0.071 and 0.077, respectively) than high-ranked females. The changes in the AI may indicate that high-ranked females were displaced during the period with more interactions. We concluded that (1) pampas deer males displayed more agonistic interactions toward high-ranked than low-ranked females; (2) this difference was mainly due to a greater number of displacements of females by mere presence; (3) high-ranked females moved far from males than low-ranked females, reflecting different relationships between them.     

Sexual behavior in brown capuchins (Cebus apella)

We observed sexual behavior patterns in two captive groups of Cebus apella.We obtained data on intersexual solicitations and intersexual competition. The length of proceptivity cycles by females averaged 18.8 ± 1.2 days; this corresponds with published reports of physiological measures of ovulatory cycles. Females initiated sexual interactions with males significantly more than males initiated interactions with females, and female solicitations increased in frequency over the duration of displayed periods of proceptivity. In contrast, male solicitations of females were infrequent and did not change significantly throughout female proceptive phases. Each female solicited the same male throughout a given proceptive phase. We observed no evidence of male-male or female-female competition. Males seem to respond to female sexual behavior directed toward them, rather than initiating sexual interactions themselves. Even so, male sexual interactions with females followed only a small proportion of solicitations.     

Differential susceptibility of male and female Oncomelania hupensis quadrasi infected with Schistosoma japonicum

Laboratory-reared male and female Oncomelania hupensis quadrasi were exposed to infection with Schistosoma japonicum. In three of four trials, infection rates in female snails (30.5–68.0%) were higher than in males (8.6–28.6%). Higher cercarial production in females may be accounted for by male-female size difference, and presumably by the availability of more nutrients in females as a result of ovarian tissue breakdown. Male and female snails were individually exposed to 20 miracidia, fixed 3–72 h post-exposure and serially sectioned to check for encapsulated and nonencapsulated primary sporocysts (ps). In 23 female (65.2%) and 12 male (39.3%) snails, ps were all unencapsulated. Six male snails (17.6%) showed 100% ps encapsulation. Among the 12 females and 16 males with both negative and positive host-tissue response, encapsulated ps in females varied from 7.1 to 50.0% and 20.0 to 71.4% in males. Distribution of encapsulated and non-encapsulated ps in both sexes suggests that males are more resistant to infection by their encapsulation reaction. Whether resistance in O. h. quadrasi to S. japonicum is genetically determined warrants further study.     

Male eyespan size is associated with meiotic drive in wild stalk-eyed flies (Teleopsis dalmanni)

This study provides the first direct evidence from wild populations of stalk-eyed flies to support the hypothesis that male eyespan is a signal of meiotic drive. Several stalk-eyed fly species are known to exhibit X-linked meiotic drive. A recent quantitative trait locus analysis in Teleopsis dalmanni found a potential link between variation in male eyespan, a sexually selected ornamental trait, and the presence of meiotic drive. This was based on laboratory populations subject to artificial selection for male eyespan. In this study, we examined the association between microsatellite markers and levels of sex ratio bias (meiotic drive) in 12 wild T. dalmanni populations. We collected two data sets: (a) brood sex ratios of wild-caught males mated to standard laboratory females and (b) variation in a range of phenotypic traits associated with reproductive success of wild-caught males and females. In each case, we typed individuals for eight X-linked microsatellite markers, including several that previously were shown to be associated with male eyespan and meiotic drive. We found that one microsatellite marker was very strongly associated with meiotic drive, whereas a second showed a weaker association. We also found that, using both independent data sets, meiotic drive was strongly associated with male eyespan, with smaller eyespan males being associated with more female-biased broods. These results suggest that mate preference for exaggerated male eyespan allows females to avoid mating with males carrying the meiotic drive gene and is thus a potential mechanism for the maintenance and evolution of female mate preference.     

Multiple mating and repeated copulations: effects on male reproductive success in red flour beetles

In many insects, both sexes mate multiple times and females use stored sperm for fertilizations. While males frequently engage in two distinct behaviours, multiple mating (with different females) and repeated copulations (with the same female), the reproductive consequences of these behaviours for males have been quantified for only a few species. In this study, males of the red flour beetle, Tribolium castaneum, were found to be capable of mating with as many as seven different virgin females within 15 min. Across sequential copulations with virgin females, there was no decline in either male insemination success or average female progeny production over 48 h. However, when males copulated with previously mated females, there was a significant decline in male paternity success across sequential copulations, possibly due to male sperm depletion. In separate experiments, T. castaneum males were found to engage in two to six repeated copulations with the same, individually marked female. These repeated copulations did not increase male insemination success, short-term female fecundity, or male paternity success. Repeated copulations may possibly play a role in sperm defence. This study indicates that males may frequently engage in multiple matings, but these additional matings may lead to diminishing male reproductive returns.     

Production,maturity, reproductive cycle and fecundity of small-spotted catshark,Scyliorhinus canicula (Chondrichthyes: Scyliorhinidae) from the northern coast of Tunisia (Central Mediterranean)

Small-spotted catshark Scyliorhinus canicula (Linnaeus, 1758) is confronted since 2000 to a drastic decline of captures in Tunisian northern areas where it formerly was quantitatively and qualitatively very abundant. A study conducted in the area showed that males and females sexually matured between 400–478 mm and 364–471 mm total length (TL), respectively. The largest male and female were 521 mm and 531 mm TL, respectively and weighed 449 and 445.5 g, respectively. There was a not significant relationship total mass vs. TL between males and females. Conversely, the relationship of liver mass vs. TL significantly differed between sexes. Both HSI and GSI values did not present significant differences between males and females. There was a not significant relationship total mass vs. TL between males and females. Both male and female HSI reached high values in adults, significantly higher than those of sub-adults. Both male and female GSI values increased with TL of specimens; additionally, they showed significant differences between juveniles and sub-adults and also between sub-adults and adults. The OSI values were significantly different between juvenile and sub-adult females, and also between sub-adult and adult females. Monthly mean values of adult male and female HSI did not significantly vary throughout the year. Significant monthly changes were recorded in mean values of adult male however no significant changes were observed in monthly mean of GSI and OSI for adult females. Vitellogenic activity and production of egg cases permanently occurred throughout the year. The diameter of largest yolky oocytes ranged from 20.1 to 23.0 (mean = 21.43 ± 1.07) and weighed from 0.64 to 0.90 g (mean = 0.78 ± 0.09). Some measurements were taken on egg cases: length with horns ranged 42.5-55.7 mm with mean = 48.9 ± 2.9, width ranged 13.6–19.7 mm with mean = 16.50 ± 0.9, while the total mass of complete egg case ranged between 1.8 and 4.6 g, with mean = 2.4 ± 0.4. An annual fecundity estimation based on production of egg cases and oocytes during one year counted in adult females, enabled us to consider it between 40 and 240.