An ontogenetically stable sexual character in a montane agamid,Salea horsfieldii Gray, 1845 (Reptilia: Agamidae) from Nilgiris,India

Many agamid lizards are known to show sexual dimorphism in body shape, colour and ornamentation or a combination of these traits. Adult males of Salea horsfieldii have a discontinuous dorsal crest at the nuchal region, which is a sexually dimorphic character. However, there is no information about the age or size at which this dimorphic ornamentation develops and if the species exhibits sexual shape dimorphism (SShD). The authors studied the morphology of S. horsfieldii and found that its ornamentation is an ontogenetically stable character present in all males, including juveniles. Seven morphological characters were measured to determine if they exhibited SShD at adult and juvenile stages. Analysis of covariance was used to identify differences in morphology between sexes. The results show that only adults exhibited SShD, but not juveniles. Adult males had larger head and foot lengths in comparison to females of the same size. Larger head length in adult males is a sexual fitness trait, which increases bite-force during intra-sexual combats. Although the presence of sexually dimorphic ornamentation right from the juvenile stage is rare in agamids, S. horsfieldii is an exception . The role of sexually dimorphic ornamentation at juvenile stages remains unknown and requires further investigation.     

Spawning behaviour and sexual dimorphism in the North American cyprinid fish Notropis leedsi,the bannerfin shiner

The spawning behaviour and sexual dimorphism of the little known North American cyprinid fish, Notropis leedsi, is described based on observations made in laboratory aquaria. Notropis leedsi is a crevice spawning species, a trait characteristic of members of the subgenus Cyprinella. Males establish breeding territories through ‘mock battles’ and defend them by chasing away intruding males or, at times, through threat displays or ‘mock battles’. Although wild-caught males are significantly larger than females, sexual dimorphism is more pronounced in the colour pattern and fin size, especially the dorsal and anal fins.

The modes of spawning behaviour in the genus Notropis are reviewed. The relationship between the promiscuous mating system (polybrachygamy), the crevice spawning mode, and sexual dimorphism in N. leedsi are discussed in relation to current notions regarding sexual selection.     

An imperfect imago? Post-mating loss of iridescent scales in Cheimas butterflies may change female from attractive to cryptic (Lepidoptera: Nymphalidae: Satyrinae)

Adults of both sexes of Cheimas opalinus (Staudinger), a Satyrinae butterfly occurring in the cloud forests of the Venezuelan Cordillera de Mérida, have simple wing colour patterns, dark brown dorsa marked by one conspicuous element, large greenish-blue patches in the discal area of the hind wing. It was observed that in young, freshly emerged females these patches are frequently absent. They fade away and eventually disappear during mating and nuptial flights when brushed out by lateral movements of the male’s hind wing put between folded female hind wings. The falling off of the scales is made easy because they do not adhere to the wing as firmly as brown background scales due to their particular folded extremities. We speculate that this process is related to the fitness of the females. Prior to mating, blue-green patches are advantageous because they attract the attention of the opposite sex and enhance the chances of successful mating. After mating they lose their sexual role. Females without the blue-green patches become cryptic. Thus, they are less apparent not only for the males, which helps them avoid sexual harassment, but also for potential bird predators. Additionally, the loss of blue reflecting scales may speed up the warming up of the abdomen and egg maturation. In the males, positive role of the patches (signalling), and negative (bird attraction), is balanced during their entire life span, and they fade gradually due to regular usage of wings scaling in flight. Our hypothesis is supported by morphological, optical, experimental and statistical analysis in which we used 509 individuals of both sexes. A similar ratio of young (with undamaged wing) females with or without blue patch was recorded, whereas in the males no individuals without any trace of blue patch were reported, and a correlation of age (wing damage) and gradual fading off of the patch was demonstrated. Such an adaptation involving an active change of the appearance of adults, i.e. colour patterns related to sexual selection, has not been reported previously in Lepidoptera.     

Geographic variation in body size and sexual size dimorphism in the giant spiny frog Paa spinosa (David, 1875) (Anura: Ranoidae)

We describe the spatial pattern of variation in body size and sexual size dimorphism in the giant spiny frog, Paa spinosa (David, 1875). The study also aims to identify potential factors responsible for geographic morphological variation in the frog. The results indicate that primary production, which positively correlates with precipitation and summer temperature in China, had an important effect on body size of P. spinosa, whereas Bergmann's rule was more efficient to explain the influence of average minimum temperature in January. The species was sexually dimorphic for body size and body shape: the body size, jaw length and forelimb length of males were significantly larger than those of females. Furthermore, the degree of sexual size dimorphism varied geographically, but the relationship between the geographic variation of sexual size dimorphism and the climate was complex. Specifically, absolute sexual size dimorphism was positively correlated with the increased ambient temperature and decreased precipitation.     

Sexual dimorphism in chelicerae,forelegs and palpal traits in two burrowing wolf spiders (Araneae: Lycosidae) with sex-role reversal

Allocosa alticeps and Allocosa brasiliensis are two sex-role-reversed spiders. Females locate males and initiate courtship. Copulation occurs inside male burrows and after copulation the males deliver their burrows to the females. We explored the occurrence of differences in morphological traits related to sex roles in both Allocosa species and compared the results with two non-burrowing wolf spiders with typical sex roles. We measured the length of the foreleg's tibia-patella and the chelicerae. Scanning electron micrographs of palpal tarsus distal sections were taken. Males showed higher values than females in all the traits considered. Adult and penultimate males lacked true claws compared with juveniles and females, but showed modified spines. The palpal organ was more proximal to the tibia compared with the non-burrowing lycosids considered in this study. Spines and palpal organ location could be associated with more effective digging. We discuss how natural and sexual selection could interact on morphology in this scenario.     

Characterisation of burrow architecture under natural conditions in the sand-dwelling wolf spider Allocosa brasiliensis

Allocosa brasiliensis (Petrunkevitch, 1910) is a wolf spider that constructs silk-lined burrows along the coastal sand dunes of Argentina, Brazil and Uruguay. This species shows a reversal in typical sex roles and sexual size dimorphism expected for spiders. Females are the smaller and mobile sex, which initiates courtship at the male burrow entrance. Mating occurs in the male burrow, and when it ends, the male leaves and the female stays inside. Females prefer to mate with those males showing longest burrows, so burrow dimensions would be under strong sexual selection pressures. Previous studies in the laboratory indicated that male burrows are longer than those of virgin females, which were described as simple silk capsules. Preliminary observations suggested that juvenile burrows presented differences from those of adults; however, detailed observations of A. brasilienisis burrow characteristics at the field were lacking. The aim of this study was to characterise the burrows of adults and juveniles of A. brasiliensis under natural conditions. We recorded the dimensions of burrows inhabited by males, females and juveniles (n = 30 for each category) and created beeswax moulds that reflected burrow shape. Juveniles inhabited tubular burrows with two branches and two openings; on the contrary, adults were found in tubular burrows with a single entry. Males and females inhabited burrows of similar length and width, but those of juveniles were shorter and narrower. We discuss the results and their possible functional explanations according to the selective pressures expected for each developmental stage and sex.     

Relative growth and sexual dimorphism of the South Atlantic hermit crab Loxopagurus loxochelis (Anomura,Diogenidae) from Ubatuba,Brazil

Some morphometric relationships and biometric aspects were studied in the hermit crab Loxopagurus loxochelis (Moreira, 1901) with the purpose of describing its relative growth and finding the size where sexual maturity is reached. Specimens were collected monthly from September 1995 to August 1997 in the Ubatuba region using double-rig trawl nets. A total of 1084 specimens (625 males and 459 females) was analysed. In this species, sexual dimorphism is particularly evident in chela dimensions. Differences between males and females were found in the left propodus length versus cephalothoracic shield length (CSL) and wet weight (WW) versus CSL relationships. Males showed a high positive allometry in chela growth, while females were close to isometry/negative allometry. The size at which a clear differentiation occurred in the growth of the propodus length and in the increase in weight of males and females was between 4.5 and 6.0mm CSL, suggesting that size at which sexual maturity is reached.     

Intersex in the gonochoristic crustacean Tanais dulongii (Audouin, 1826) (Peracarida: Tanaidacea: Tanaididae): a comparison of external reproductive characteristics

Tanais dulongii (Audouin, 1826) is a small benthic crustacean with separate sexes and a marked sexual dimorphism characterized by a cephalothorax narrowed anteriorly, larger chelae (claws) and a pair of tiny genital cones in males, and ovisacs that form chambers for carrying embryos in females. Recent studies have described the existence of intersexual individuals with a cephalothorax similar to males, large chelae and ovisacs, but, due to their small size, it has not been possible to confirm the presence of genital cones under normal light microscopy. The present study analyses and compares external reproductive structures under scanning electron microscopy, of male and female T. dulongii, to corroborate the presence of both ovisacs and genital cones in potentially intersex individuals. The possible causes, such as hermaphroditism, environmental sex determination, parasitism, genetic aberration or endocrine-disrupting pollutants, are discussed.     

The occurrence of facultative paedomorphosis in a lacustrine population of the Pyrenean newt (Calotriton asper): morphology and age structure

Facultative paedomorphosis is a common polyphenism in newts where two alternative phenotypes can coexist: metamorphs and paedomorphs (mature with larval traits, i.e. retaining gills). This phenomenon has been reported in some lacustrine populations of the Pyrenean newt (Calotriton asper). The morphology and life-history traits were studied in a lacustrine population of this species with the occurrence of facultative paedomorphosis. The results showed that 24.3% of adults retained gills at different levels of reabsorption and had a smoother skin compared with the other populations, which were fully metamorphic. The body size and shape showed significant sexual differences, with males being larger than females. The presence of paedomorphic traits also affected the body size and shape, revealing a complex pattern of growth in which metamorphic adults were larger than paedomorphs. The age structure was different between sexes, with a median age of 10.5 and 7 years and longevity of 19 and 14 years in males and females, respectively. Considering each sex separately, the age structure was not significantly different between metamorphic and paedomorphic newts. In addition, metamorphosed and branchiate juveniles were found with a maximum age of 13 and 20 years, respectively. Remarkably, long-lived larvae with an exceptional individual of 18 years were found, which has not previously been reported in any other newt species. The mechanisms that can explain the evolution of paedomorphosis are complex and comprise the interaction of multiple factors related to the cost of reproduction and growth.     

Mainland versus island differences in behaviour of Podarcis lizards confronted with dangerous prey: the scorpion Buthus occitanus

Rapid divergence in behaviour of populations invading novel habitats is often considered adaptive as it may allow a species to exploit novel resources. Here we explore the behavioural response of two closely related species of Podarcis lizards living in different habitats, the Spanish mainland and a dry volcanic island, towards a potentially dangerous prey. Our results show that whereas insular lizards attacked scorpions and consequently considered them to be potential prey, mainland lizards tended to flee or ignored them. Sexual differences in the response to scorpions were pronounced in the insular habitat. Males tended to attack scorpions while females tended to ignore them. Inter‐specific and inter‐sexual differences in the responses of lizards may be mediated by body size differences between populations and sexes. The rapid changes in behaviour allowing insular lizards to recognize scorpions as potential prey may have allowed these animals to capitalize on an abundant food resource in a depauperate environment.     

Natural history of Phyllomedusa megacephala (Miranda-Ribeiro, 1926) (Anura: Hylidae) in southeastern Brazil,with descriptions of its breeding biology and male territorial behaviour

The breeding biology and male territorial behaviour of the large-headed leaf-frog (Phyllomedusa megacephala) were studied in three temporary altitudinal streams located in the Cerrado biome of southeastern Brazil, during three consecutive years (2007–2009). Phyllomedusa megacephala showed significant sexual dimorphism, with females being bigger and heavier than males. Acoustic and physical interactions between males defending or not defending territories including amplectant and non-amplectant males, patrolling behaviour by males without established territories, and triple amplexus were observed. Neither males nor females were observed using visual cues when searching for mates. We found that males that were present at breeding sites in previous years bred more successfully and maintained territory better.     

Population structure and breeding season of the hermit crab Diogenes brevirostris Stimpson, 1858 (Decapoda,Anomura, Diogenidae) from southern Mozambique

In this study the population dynamics of the diogenid hermit crab Diogenes brevirostris is evaluated focusing on size structure, sex ratio and breeding season. Crabs were randomly taken on a monthly basis from January to December 2003 at Costa do Sol, Maputo Bay, southern Mozambique. A total of 622 crabs was obtained of which 290 were males (46.6%), 170 were non‐ovigerous females (27.3%) and 162 were ovigerous females (26.1%). The overall size frequency distribution was unimodal for males, non‐ovigerous females and ovigerous females. The overall sex ratio (1:1.15) differed from the expected 1:1 ratio. Sexual dimorphism was evidenced by the larger size attained by males in relation to both ovigerous and non‐ovigerous females. Breeding took place year‐round with three peaks of spawning (March, August and December). Despite the high reproductive activity, young recruits were scarce in the population. The present results suggest that the study area is suitable for reproduction and growth whereas recruitment may take place in different areas from that occupied by the adults.     

First-instar morphology and sexual dimorphism in the gall-inducing scale insect Apiomorpha Rubsaamen (Hemiptera: Coccoidea: Eriococcidae)

Sexual dimorphism among crawlers of the scale insect family Eriococcidae is reported for the first time. The general morphology of crawlers of the gall-inducing genus Apiomorpha (Eriococcidae) is presented and sexual dimorphism described. Sexual dimorphism appears to be associated with differential dispersal and settling-site preference of the sexes during the crawler stage. First-instar males of the A. pharetrata and A. munita species-groups settle only on the galls induced by their mothers or, in the case of A. munita, also galls of nearby females, whereas female crawlers disperse. Female crawlers of all species of Apiomorpha, and male crawlers of most species, are well suited for air-borne dispersal. It is suggested that sexual dimorphism among crawlers of Apiomorpha, and some other scale insects, is the result of loss or reduction of those morphological features associated with dispersal. In addition, male crawlers of some species of Apiomorpha have sensory structures which may assist in the detection of sex-specific settling sites.     

Population biology of Sphaeroma serratum Fabricius (Isopoda,Flabellifera) at the Port of Mar del Plata,Argentina

Variations in size distribution, sex ratio, fecundity and morph frequencies in a population of Sphaeroma serratum were studied year-round. Changes in size distribution are most marked during the breeding season. Growth is arrested during the winter months. Young are produced throughout the summer; these overwinter, reproduce and then die. Differences in size of mature males suggest an effect of the timing of birth on life-span. Females are able to produce two broods. Offspring number is positively correlated with female size. Brood pouch mortality is estimated at 39%. Marked changes in sex ratio within the breeding season are thought to be artifacts due to sexual differences in behaviour. Comparison of reproductive traits of this, and other, populations shows a latitudinal pattern related to the duration of the warm season. Analysis of morph frequencies revealed similarities with European populations so far studied.     

Population structure and breeding biology of the hairy crab Pilumnus vespertilio (Fabricius, 1793) (Crustacea: Brachyura: Pilumnidae) in southern Mozambique

The population structure and reproduction of Pilumnus vespertilio were studied for the first time in Mozambique. Random samples of crabs were taken monthly from January to December 2002 from a pebble area of Inhaca Island, southern Mozambique. A clear sexual dimorphism was observed in the present population with males reaching greater sizes than females. Sex ratio was female‐biased, and the monthly size–frequency distributions were often bimodal. The annual reproductive cycle of Pilumnus vespertilio was continuous with peaks of breeding in summer. Results suggest that embryonic development may be synchronized within the population as a result of the very high reproductive activity observed in summer. Juveniles are recruited mostly in winter in the study area.     

A remarkable new species of scuttle fly (Diptera: Phoridae) whose larvae infest chickpea root nodules in India

Metopina ciceri sp. nov. is described on the basis of males with reduced wings, fully winged females, blind females with reduced wings, pupae and larvae. The larvae infest the root nodules of the chickpea, Cicer arietinum L. The blind-morph females are considered to be congeneric with the type species of the genus Typhlophorina Silvestri and this genus is synonymized with Metopina. The males, if procured in isolation, would have been assigned to a separate genus. The evolution of sexual dimorphism and dimorphic females in M. ciceri is discussed in relation to a speculative scenario involving juvenile hormone and heterochrony. It is also speculated that dispersal is undertaken by the sighted fully-winged female morph only. These speculations and the question of whether the infestation of C. arietinum by M. ciceri affects yield remains to be investigated.     

Reproductive patterns of Trachycephalus venulosus (Laurenti, 1768) and Scinax fuscovarius (Lutz, 1925) from the Cerrado,Central Brazil

Animal mating systems are moulded by ecological factors, mainly the temporal patterns of reproduction. We report the reproductive period, use of microhabitats, clutch and egg sizes, reproductive efforts, occurrence of sexual size dimorphism, and the relation between body size and fecundity in the gravid females of Trachycephalus venulosus and Scinax fuscovarius at Serra da Bodoquena, Central Brazil. The reproduction of both species was correlated with the rainy season. Females of T. venulosus produced more eggs and their eggs were larger than those of S. fuscovarius. The females of both species were larger and heavier than males. The reproductive effort was measured as the ratio of gonad mass in relation to body mass. Females of both species presented similar reproductive efforts, but males of S. fuscovarius invested more in gonads compared to males of T. venulosus. Trachycephalus venulosus presented significant correlation between snout–vent length versus number of mature eggs and body mass versus number of mature eggs and ovarian mass. Scinax fuscovarius showed significant correlation between body mass versus ovarian mass. Trachycephalus venulosus is an explosive breeder, whereas S. fuscovarius has prolonged reproduction. These species are able to adapt to several types of habitat, due to behavioural and physiological plasticity.