Relative growth and morphological sexual maturity of the deep-water velvet shrimp Metapenaeopsis sibogae (Crustacea,Decapoda, Penaeidae)

Metapenaeopsis sibogae inhabits the South Pacific and Southeast Asia and is an emerging fisheries resource. However, studies on the population biology of M. sibogae are scant, and their morphometric relationships have not been examined. Thus, we studied the relative growth of M. sibogae, hypothesizing that its morphological sexual maturity can be estimated based on abrupt shifts in allometry. The relationships of body length (BL) and body weight (BW) with carapace length (CL) were determined by the least squares method. Data for each sex were repeatedly partitioned into two size-delimited subsets (early and late phases), considering a CL value as a hypothesized transition point. Analysis of the sum of squared residuals indicated that two separate linear BL/CL models fit the data better than a single linear model showing clear transition points in both males (13.2 mm CL) and females (15.0 mm CL). The changes in allometry in the BL/CL relationships between early- and late-phased males and females were indicated by a 20.5 and 21.5% decrease in the slope, respectively. These transition points could be associated with sexual maturity. The growth rate of BW vs. CL slowed significantly after morphological sexual maturity was reached in both sexes, demonstrating the existence of dimorphic growth.     

Sexual and ontogenetic morphometric variation in Xiphopenaeus kroyeri (Crustacea,Decapoda, Penaeidae): a new approach with linear and angular morphometric data

The present study evaluates the ontogenetic/sexual morphometric variation in Xiphopenaeus kroyeri. Sampling was from July 2001 to June 2003 at Ubatuba, São Paulo, Brazil. Animals were sexed and measured (cephalothorax length-CC, partial of the rostral spine-CPR, rostral spine-CR and rostral spine angulation-AR). Data analysis included linear morphometric analysis: equation ln y = ln a + ln b (sex/ontogeny fitting), k-means method (ontogenetic classification), analysis of covariance (morphological maturity), removal of the allometric effect, verification of parametricity and collinearity, principal component (PCA) and linear discriminant analysis (visualization of tendencies), permutational multivariate analysis of variance (hypothesis test). In addition, circular analysis was undertaken: circular normal distribution and concentration parameter, circular analysis of variance (hypothesis test), PCA (observe tendencies) and linear-circular regression (ontogenetic trajectory, RA-dependent variable, CL-independent variable). Morphological changes in the cephalothorax, in the adult stage, may be related to the increase in size of the gonads during sexual maturation and to the development of gills during the transition from arthrobranch (juvenile) to dendrobranch (adult). The rostral spine, in the adult stage, tends to become more elongated and more sharply angled. This feature may be related to predation pressure on larger specimens (adults), knowing that throughout its ontogeny the rostral spine of this species assumes phenotypic traits that make swallowing more difficult for predators.     

Reproductive cycle of seabob shrimp Xiphopenaeus kroyeri (Crustacea,Penaeidea) from the northeast coast of Brazil

The reproductive cycle of Xiphopenaeus kroyeri north-eastern Brazil was described to contribute to the sustainable management of this stock in the region. Specimens were collected monthly from August 2011 to July 2012 using a local vessel of the artisanal fleet. A total of 1201 individuals were analyzed (673 females and 528 males) with a mean carapace length (CL) of 1.88 ± 0.16 cm and total length (TL) of 9.00 ± 1.22 cm. The lowest CL and TL of mature females were 1.33 and 6.5 cm, respectively, and all females above 2.44 cm (CL) and 11.5 cm (TL) were mature. Ovarian maturation was classified into four stages: I (immature), II (maturing), III (mature) and IV (spawned). Individuals of all maturational stages were present throughout the year. Considering the macro and microscopic analysis, it was suggested that this species in north-eastern Brazil has a continuous reproductive cycle, with two seasonal peaks, November/December and February (austral spring and summer). A positive correlation between the percentage of mature females and temperature was observed, and a higher percentage was reported in the warmer months of the year. This suggests that the reproductive peaks can be triggered by water temperature variation throughout the year.     

Morphological study for understanding the sexual pattern in ghost shrimp Callichirus major (Crustacea: Axiidea)

Callichirus major is a species of ghost shrimp that has burrowing habits, building underground galleries in the intertidal region of beaches. This study aimed to analyse some morphological parameters to verify its type of sexual pattern. A sample of 79 individuals, collected at the beach of Corujão, Espírito Santo, Brazil, was used. Data on the external morphology, presence of gonopores, carapace length (CL) and cheliped lengths (Lch) were obtained. In addition, the gonads were processed for histological analysis. The animals were divided into three categories: A, individuals with male characteristics; B, those presenting exclusively female characteristics; C, animals with characteristics of intersex, which presented supernumerary gonopores. Positive allometries were found for Lch versus CL only for category A, characterizing the group's marked heterochely. Histologically, it was possible to observe the presence of oocytes in category A and one case of male tissue in an intersex individual (category C). However, no genital ducts of both sexes were found in that individual. Callichirus major presents controversial sexual characters, which makes it difficult to understand the reproductive parameters and sexual pattern. However, maybe that species can develop a sexual system of hermaphroditism.     

Population structure,sex ratio and growth of the seabob shrimp Xiphopenaeus kroyeri (Decapoda,Penaeidae) from coastal waters of southern Brazil

This study evaluated the growth and population structure of Xiphopenaeus kroyeri in Babitonga Bay, southern Brazil. Monthly trawls were conducted from July 2010 through June 2011, using a shrimp boat outfitted with double-rig nets, at depths from 5 to 17 m. Differences from the expected 0.5 sex ratio were determined by applying a Binomial test. A von Bertalanffy growth model was used to estimate the individual growth, and longevity was calculated using its inverted formula. A total of 4,007 individuals were measured, including 1,106 juveniles (sexually immature) and 2,901 adults. Females predominated in the larger size classes. Males and females showed asymptotic lengths of 27.7 mm and 31.4 mm, growth constants of 0.0086 and 0.0070 per day, and longevities of 538 and 661 days, respectively. The predominance of females in larger size classes is the general rule in species of Penaeidae. The paradigm of latitudinal-effect does not appear to apply to seabob shrimp on the southern Brazilian coast, perhaps because of the small proportion of larger individuals, the occurrence of cryptic species, or the intense fishing pressure in this region. The longevity values are within the general range for species of Penaeidae. The higher estimates for longevity in populations at lower latitudes may have occurred because of the growth constants observed at these locations, resulting in overestimation of this parameter.     

Early Developmental Stages of the Green Tiger Prawn, Penaeus semisulcatus de Haan (Crustacea, Decapoda, Penaeidae)

Gravid females of Penaeus semisulcatus were spawned in the laboratory by natural means. The embryos were documented and the larvae were reared from hatching to postlarval stage at 28.2–30.0 °C and 33.5–34.5 g kg⁻¹ salinity for about 10 days (223 h 55 min). Six naupliar stages, three protozoea stages, three mysis stages and the first postlarval stage were described and illustrated. The larvae were fed only with microalgae Tetraselmis tetrathele and Chaetoceros gracilis from first protozoea until the second mysis, with about 90% survival rate; from the third mysis until the first postlarva they were fed with similar microalgae coupled with rotifer Brachionus plicatilis and Artemia nauplii. The embryonic and larval stages of P. semisulcatus are generally similar to those of other closely related species in the family Penaeidae, such as Melicertus canaliculatus, Fenneropenaeus merguiensis, and Marsupenaeus japonicus, except for the size and structure of diagnostic characters, setation of appendages and duration of metamorphoses. The change in the feeding habit during ontogeny was related to morphological transformation of the feeding apparatus of larvae and postlarvae. This paper is the first comprehensive and complete account of the early developmental stages of P. semisulcatus.     

Haplotype-specific single-locus multiplex PCR assay for molecular identification of sea-bob shrimp,Xiphopenaeus kroyeri (Heller, 1862), cryptic species from the Southwest Atlantic using a DNA pooling strategy for simultaneous identification of multiple samples

This work describes a single-locus multiplex PCR assay based on partial COI mitochondrial gene polymorphisms for identification of two Atlantic cryptic species of the sea-bob shrimp, Xiphopenaeus kroyeri (Heller, 1862) that were recently identified using molecular approaches. Reliable identification of cryptic species of Xiphopenaeus spp. has fundamental implications for management and conservation of the sea-bob shrimp fishery stocks. The assay was developed based on sequence polymorphisms of 130 specimens of both species, comprising samples from Venezuela to the southern coast of Brazil, validated by the amplification of 368 adult shrimp samples from nine different locations and confirmed by direct sequencing. The methodology has been optimized to enable the identification of equi-molar mixtures of DNA from up to 10 individuals by PCR reaction, allowing the fast and cheap identification of many specimens for large scale studies on fisheries biology and population genetics. The DNA pooling strategy enabled the identification of a new locality of occurrence of Xiphopenaeus sp. II in the Brazilian coast, Caravelas, indicating that the species distribution may be continuous on the coast, and not disjoint as observed so far.     

The phylogeny of diving beetles (Coleoptera: Dytiscidae) and the evolution of sexual conflict

A model of evolution based on conflicts of interest between the sexes over mating decisions is examined in relation to diving beetles (Dytiscidae). The model predicts the following evolutionary sequence: (1) cost to females of mating increases, (2) females evolve behavioural resistance to male mating attempts, (3) males evolve devices to overcome female resistance, and (4) females evolve morphological counter-adaptations to the male devices. This model is tested using species of Dytiscidae, in which (1) some species have a very long mating duration while others mate quickly, (2) females of some species resist male mating attempts by swift and erratic swimming when seized by a male, (3) males of some species possess a grasping device in the form of sucker-shaped setae on the legs used to adhere to the pronota or elytra of females prior to mating, and (4) females of some species have a modified dorsal cuticle with irregular sculpturing which appears to interfere with the male adhesive setae. The predicted order of evolution of some of these features was tested in a cladistic analysis of 52 taxa in Dytiscidae and Hygrobiidae using characters from adult and larval morphology and a portion of the gene wingless . The combined analysis resulted in nine most parsimonious cladograms. The consensus cladogram of these indicates that male sucker setae arose a single time in a clade of Dytiscinae. Nested within this clade are five groups with an independently derived, modified dorsal cuticle in females. This pattern of characters in Dytiscinae is consistent with the prediction implied by the model of sexual selection. The utility of wingless as a marker for phylogenetic analysis of diving beetles is discussed, and the resulting phylogeny is compared with previous analyses and current classification.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 359–388.     

Juvenile morphology of the xanthid crab Leptodius exaratus (H. Milne-Edwards, 1834) (Decapoda: Brachyura), with notes on the appearance of sexual dimorphism

Summary

The morphometrical and meristic features of the carapace, cephalic appendages (antenna, antennule), mouthparts (maxillule, maxilla, first-third maxillipeds), sternum, pereiopods, abdomen, and pleopods of juveniles and the onset of morphological sexual dimorphism were described for the xanthid crab Leptodius exaratus (H. Milne Edwards, 1834), based on laboratory-reared and wild adult specimens collected from Tateyama Bay, Japan. First instar juveniles shared some of the features of adults (e.g. gross appearance of the carapace and cheliped propodus proportions), but differed from adults on almost all other morphological parameter examined. Morphological development was still not complete at the ninth instar; extrapolation from the rate of morphological changes between instars 1–9 suggests that L. exaratus requires about 13 ecdyses to transform into adults, including development of reproductive structures. Differences in the number and morphology of pleopods and abdomen width allowed early distinction of the sexes. Thus, males formed gonopods in the first abdominal somite and lost the paired vestigial pleopods in somites 3–5 from the fourth instar; females retained the pleopods in somites 2–5, but these became biramous and had increased setation. The abdomen grew wider in females than in males from the fifth instar. Several morphological features of juveniles have phylogenetic and taxonomic implications: carapace motifs clearly place L. exaratus in the superfamily Xanthoidea, whereas the patterns of setation in the scaphognathite and first maxilliped epipod allow separation of this (xanthid) species from crabs of other Xanthoidean families.     

Characterization of the sexual pattern of Parastacus varicosus (Crustacea: Decapoda: Parastacidae)

Abstract. Freshwater crayfishes of the genus Parastacus are intersex, i.e., show characteristics of both sexes in the same individual; also, intersexuality has been documented in hermaphroditic species. The aim of this study was to analyze the gonads of Parastacus varicosus , characterizing its sexual pattern. The animals were collected at Cova do Touro, Gravataí, Rio Grande do Sul, Brazil. Three sexual forms were identified: intersex females, intersex males, and transitional specimens showing an ovotestes gonad that could only be identified by means of histological analysis. All specimens had two pairs of gonopores and gonoducts. The oviduct had a wider diameter in females, whereas in males the vasa deferentia were more developed. Gonads were composed of two parallel structures located in the cephalothorax. Female gonads were classified into three stages. The presence of transitional specimens may indicate that sex change occurs, with protandric hermaphroditism, as observed in other species of Parastacus . Because previous studies had demonstrated that P. varicosus is a gonochoristic species in a population from Uruguay, the present study addressed the possibility that the sexual pattern depends on differences in environmental factors among populations. To improve understanding of evolution of hermaphroditism in these crustaceans, their reproductive dynamics should be studied, including identification of the factors stimulating male and female functions.     

Relative growth,morphological sexual maturity,and size of Macrobrachium amazonicum (Heller 1862) (Crustacea,Decapoda, Palaemonidae) in a population with an entirely freshwater life cycle

The objective of this study was to estimate the size of morphological sexual maturity based on the study of relative growth, to determine the maximum size of individuals, and to determine if there are different morphotypes of males in a population of Macrobrachium amazonicum with an entirely freshwater life cycle. Collections were made monthly, with the use of a net, from September 2006 through August 2007. In each individual, the following structures were measured: carapace length (CL, in mm), width of the second pleuron (PlL, mm), length of the carpus (CaL, mm), and length of the propodus (PrL, mm). Relative growth was analyzed by observing the change in growth patterns of certain parts of the body in relation to the independent variable CL. The maximum sizes found were 8.5 and 11.4?mm CL for males and females, respectively. The morphometric variables: length of the carpus (CL?×?CaL) for males, and width of the second pleuron (CL?×?PlL) for females gave the best estimates for the size at maturation, which was 4.26?mm CL for males and 5.39?mm CL for females. The growth pattern in the different stages and the beginning of differential growth seemed to be closely related to reproductive aspects. No indices were found that separated the males into four different morphotypes, as proposed in the literature for coastal or artificially farmed populations. Only the male morphotype termed translucent claw was found in this population. The different morphological patterns in different regions are probably explained by ecological differences in the environments inhabited by these groups, principally in the availability of nutrients and the salinity in which the larvae develop.     

First report of exocrine epithelial glands in oestroid flies: the tachinid sexual patches (Diptera: Oestroidea: Tachinidae)

Sexual patches are abdominal areas identifiable by modified setation, present in the males of several groups of Tachinidae (Diptera). We comparatively studied more than 40 species belonging to 24 genera representative of subfamilies known to bear these organs, using light microscopy and scanning (SEM) and transmission (TEM) electron microscopy. We provide a detailed characterization of the fine structure of the setae and microtrichia composing these sexual patches and of the underlying epithelium. Study of abdominal sections showed that, close to the patch area, the epidermis forms a thick layer composed of numerous secretory units of strictly associated cells, ending at the level of cuticular pores at the base of the setae. We hypothesize a secretory function of these structures. The segmental pattern of the sexual patches across the Tachinidae is defined and predictable. We note that almost all the segmental patterns share the presence of sexual patches on abdominal tergite 4, underscoring the diversity of male sexual specializations that occur on the fourth abdominal segment of muscomorph flies.     

Intraspecific variation and intersexual correlation in secondary sexual characters of three diving beetles (Coleoptera: Dytiscidae)

Male diving beetles of the subfamily Dytiscinae possess tarsi with adhesive discs that they strike on the female dorsum during mating interactions. Females of many species are dimorphic, being either smooth or structured dorsally. Darwin suggested the female structures were an aid for the male but in this study we investigate these characteristics in the light of sexual conflicts. The intraspecific variation in the numbers and size distribution of male tarsal discs, and in body measurements were recorded for three dytiscine species, all with dimorphic females. The number of protarsal discs in the two Dytiscus species varied much more than previously reported. In addition, only a small part of the variation could be explained by body size. In Graphoderus we found highly significant differences in male secondary sexual characters among populations. A multivariate analysis significantly correlated male secondary sexual characters with the proportion of granulate females in the populations. These observations are consistent with the theory of arms races and female counter adaptations. Covariation between male and female characters is predicted from a framework of sexual conflict over mating rate. At the same time our study gives a new perspective on the function of dytiscine female dorsal irregularities debated ever since Darwin.     

The secondary copulatory organ in female ground weta (Hemiandrus pallitarsis,Orthoptera: Anostostomatidae): a sexually selected device in females?

Secondary sexual devices in female insects, primarily abdominal modifications, appear to function as a means of thwarting coercive mating attempts by males or are, in rare cases, sexually selected adaptations. Female ground weta, Hemiandrus pallitarsis (Orthoptera: Anostostomatidae), have an elaborate elbowed device on the underside of the mid-abdomen. Experimental removal of this accessory organ shows that it does not increase the probability of mating as predicted by the thwart-copulation hypothesis. Instead, removal prevents copulation, thus demonstrating that it is a secondary copulatory device. The male attaches to the organ both at the beginning of copulation and at the end, when he positions himself to adhere a spermatophylax food gift onto the mid-ventral region of his mate. The female accessory organ does not function to manipulate eggs or larvae (females provide care to their single clutch of offspring) and is unlikely to be a copulatory structure that prevents hybridization. The great extent of the modification of the ventral abdominal segments of H. pallitarsis females compared to other Hemiandrus species is consistent with a history of sexual selection on the accessory organ. Taken together, these results and the finding that the length of the accessory organ of H. pallitarsis correlates with female fecundity, suggest that this structure evolved under sexual selection to acquire nuptial gifts from males.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 463–469.     

Role of the petasma and appendices masculinae during copulation and insemination in the penaeoid shrimp,Sicyonia dorsalis (Crustacea: Decapoda: Dendrobranchiata)

Summary

The role of presumed male gonopods in the insemination of females was investigated in the penaeoid shrimp Sicyonia dorsalis. Males with partially ablated petasmata or with ablated appendices masculinae did not copulate with females, while control males with exopods removed from the third pleopods copulated frequently and successfully inseminated females. However, males with petasmata altered by blockages at the tip or at the base did copulate with females but were unable to inseminate them. The hypothesis that the petasma of Sicyonia is a sperm injection device is rejected. Evidence against this hypothesis includes the structure of the gonopods, the position of the male at right angles below the female during copulation, the brevity of copulation, the frequency of copulation during normal matings, and the ability of males to inseminate only the spermatheca on one side per successful copulation. It is hypothesized that the male uses the petasma, supported by the endopods of the second pleopods, to hook onto the female thelycum, adjusting position so that one erect genital papilla directly injects sperm mass into the aperture of one of the paired spermathecae. It is suggested that female selection on male petasma structure and use has resulted in the complex form of the petasma, rather than a purely mechanical selection for an efficient sperm injection device.     

Grooming as a secondary behavior in the shrimp Macrobrachium rosenbergii (Crustacea,Decapoda, Caridea)

The giant freshwater prawn, Macrobrachium rosenbergii, is a large shrimp extensively used in aquaculture whose grooming behaviors were analyzed in this study. Macrobrachium rosenbergii exhibits three unique male morphotypes that differ in their behavior, morphology and physiology: small-clawed males (SM), orange-clawed males (OC) and blue-clawed males (BC). The largest and most dominant males, BC males, are predicted to have significantly different grooming behaviors compared to females and the other two male morphotypes. These BC males may be too large and bulky to efficiently groom and may dedicate more time to mating and agonistic interactions than grooming behaviors. Observations were conducted to look at the prevalence of grooming behaviors in the absence and presence of conspecifics and to determine if any differences in grooming behavior exist among the sexes and male morphotypes. Significant differences in the grooming behaviors of all individuals (females and male morphotypes) were found. BC males tended to have the highest grooming time budget (percent of time spent grooming) while SM males had a relatively low grooming time budget. The grooming behaviors of the male morphotypes differed, indicating while these males play distinct, separate roles in the social hierarchy, they also have different grooming priorities. The conditions in which Macrobrachium rosenbergii are cultured may result in increased body fouling, which may vary, depending on the grooming efficiencies and priorities of these male morphotypes. Overall, grooming behaviors were found to be a secondary behavior which only occurred when primary behaviors such as mating, feeding or fighting were not present.     

Phylogeny and classification of the shrimp genera Acetes,Peisos, and Sicyonella (Sergestidae: Crustacea: Decapoda)

Despite their role in marine systems, Sergestidae remain one of the most poorly understood families amongst planktonic shrimps with regard to phylogeny. Recent morphological and phylogenetic revisions of a number of sergestid genera have disentangled classificatory problems and emphasized the importance of reproductive structures for the taxonomy and phylogeny of the Sergestidae. Only three genera, Acetes, Peisos, and Sicyonella, remain unrevised phylogenetically. We undertook a phylogenetic analysis of these groups based on 124 morphological characters (120 binary, four multistate). Eighteen new characters were based on scanning electron microscopy studies of the clasping organ and petasma. The phylogenetic analysis revealed statistically supported monophyly of the clades Sicyonella and Acetes + Peisos. We combine Peisos and Acetes into a monophyletic genus Acetes, give emended diagnoses and keys to all species of Sicyonella and Acetes, and discuss morphological trends within these genera. We present maps of geographical distribution for all valid species of Acetes. © 2015 The Linnean Society of London     

Sexual dimorphism in the tusked frog, Adelotus brevis (Anura:Myobatrachidae): the roles of natural and sexual selection

At least two adaptive processes can lead to the evolution of sexual dimorphism: sexual selection (e.g. male-male combat) or natural selection (e.g. dietary divergence). We investigated the adaptive significance of a distinctive pattern of sexual dimorphism in a south-eastern Australian frog, Adelotus brevis. Male Adelotus grow larger than female conspecifics, have larger heads relative to body size, and have large paired projections (‘tusks’) in the lower jaw. All of these traits are rare among anurans. We quantified the degree of dimorphism in Adelotus, and gathered data on diets and mating systems of this species to evaluate the possible roles of sexual selection and dietary divergence in favoring die evolution of these sexually dimorphic traits. Analysis of prey items in alimentary tracts revealed significant sex differences in prey types. For example, females ate proportionally more arthropods and fewer molluscs than did males. However, this difference is likely to be a secondary consequence of habitat differences between the sexes (due in turn to their different reproductive roles) rather than a selective force for the evolution of sexual dimorphism. Calling males spend their time in moist habitats where pondsnails are abundant, whereas females are more often encountered in the drier arthropod-rich woodlands. A three-year behavioural ecology study on a field population revealed that reproductive males engage in agonistic interactions, with the sexually dimorphic tusks used to attack rivals. Larger body size contributed to male reproductive success. Small males were excluded from calling sites and, among the calling males, larger animals had higher reproductive success (numbers of matings) than did smaller individuals. Hence, the atypical pattern of sexual dimorphism in Adelotus brevis seems to have resulted from sexual selection for larger body size and tusk size in males, in the context of male-male agonistic behaviour, rather than natural selection for ecological divergence between the sexes.