Sexual Traits Research Articles

Personality, sperm traits and a test for their combined dependence on male condition in guppies.

There is evidence that animal personality can affect sexual selection, with studies reporting that male behavioural types are associated with success during pre- and post-copulatory sexual selection. Given these links between personality and sexual traits, and the accumulating evidence that their expression can depend on an individual's dietary status (i.e. condition), a novel prediction is that changes in a male's diet should alter both the average expression of personality and sexual traits, and their covariance. We tested these predictions using the guppy Poecilia reticulata, a species previously shown to exhibit strong condition dependence in ejaculate traits and a positive correlation between sperm production and individual variation in boldness. Contrary to expectation, we found that dietary restriction—when administered in mature adult males—did not affect the expression of either behavioural (boldness and activity) or ejaculate traits, although we did find that males subjected to dietary stress exhibited a positive association between sperm velocity and boldness that was not apparent in the unrestricted diet group. This latter finding points to possible context-dependent patterns of covariance between sexually selected traits and personalities, which may have implications for patterns of selection and evolutionary processes under fluctuating environmental conditions.

Contamination effects on sexual selection in wild dung beetles.

Sexual selection influences the expression of secondary sexual traits, which are costly to produce and maintain and are thus considered honest indicators of individual condition. Therefore, sexual selection could select for high-quality individuals able to respond to stressful conditions, with impacts on population-level fitness. We sampled dung beetles from 19 pastures and investigated if contamination by herbicides and veterinary drugs modifies male investment in sexually selected traits and has associated population-level effects. We measured horn size, condition dependence (i.e. size-corrected body mass) and allometry, besides abundance and sexual size dimorphism in three species: Copris incertus, Euoniticellus intermedius and Digitonthophagus gazella. In contrary to our expectations, horn size was independent of contamination and individual condition. However, strong positive allometric relationships were reduced by herbicide contamination for C. incertus and D. gazella and were increased by ivermectin for C. incertus, revealing differential investment in horn production according to body size in contaminated habitats. At the population level, large-horned C. incertus males were more abundant in contaminated pastures, potentially revealing a case of evolutionary rescue by sexual selection or a plastic response to higher population densities. Finally, chemical compounds affected the sexual size dimorphism of all three species, with potential effects on female fecundity or intrasexual selection. Together, our findings indicate that contamination interferes with sexual selection processes in the wild, opening new questions regarding the role of sexual selection in favouring species persistence in contaminated environments.

Mosaic Evolution of Craniofacial Morphologies in Ghost Electric Fishes (Gymnotiformes: Apteronotidae)

Ghost electric knifefishes (Gymnotiformes: Apteronotidae) are a dominant component of the species diversity and biomass of large lowland rivers in Greater Amazonia, including 77 species that exhibit diverse craniofacial morphologies associated with trophic and secondary sexual traits. Here we use open-source computed micro-tomography (µCT) scans to generate 3D reconstructions for a majority of apteronotid species and almost all valid genera, and geometric morphometric and phylogenetic analyses to explore patterns of skull evolution. As with most vertebrates, principal component 1 (PC1) summarizes variance from brachycephalic to dolichocephalic morphologies, previously described as heterocephaly, and PC2 summarizes variance from recurved (upturned) to decurved (downturned) snout morphologies, described here as heterorhynchy. Phylomorphospace and traitogram analyses found instances of both convergent and divergent evolution along both of the first two PC axes, as well as a preponderance of clades characterized by morphological stasis or phylogenetic conservatism. Certain phenotypic combinations predominate among species and clades, including elongated-downturned snouts and foreshortened-upturned snouts, while other phenotypic combinations are not observed, including elongated-upturned snouts and foreshortened-downturned snouts. These results highlight the power of 3D geometric morphometrics in the study of craniofacial evolution and indicate developmental or functional constraints in the evolution of craniofacial phenotypes in an ecologically dominant clade of riverine Amazonian fishes.

Rapid diversification of the Variable Seedeater superspecies complex despite widespread gene flow

Disentangling the evolutionary relationships of rapidly radiating clades is often challenging because of low genetic differentiation and potentially high levels of gene flow among diverging taxa. The genus Sporophila consists of small Neotropical birds that show, in general, relatively low genetic divergence, but particularly high speciation rates and pronounced variation in secondary sexual traits (e.g., plumage color), which can be important in generating premating reproductive isolation. In cases like these, the use of genome-wide sequence data can increase the resolution to uncover a clade’s evolutionary history. Here, we used a phylogenomic approach to study the evolutionary history and genetic structure of the Variable Seedeater superspecies complex, which includes S. corvina, S. intermedia, and S. americana. Using ∼25,000 genome-wide single nucleotide polymorphisms (SNPs), we confirmed that the Variable Seedeater superspecies complex is monophyletic. However, a phylogenetic reconstruction based on a mitochondrial marker (ND2) resulted in a discordant tree topology, particularly in the position of Wing-barred Seedeater S. americana, which might be due to a mitochondrial capture event. Our results suggest historical gene flow among lineages, particularly between species with conflicting topologies. Among the four phenotypically variable S. corvina subspecies, our structure analyses identified three main distinct genetic groups (K = 3), and that the entirely black subspecies, S. c. corvina, is derived from within a pied-colored clade. Further, we inferred widespread gene flow across the whole species’ distribution, including between subspecies. However, gene flow was about 100 times lower at the geographic boundaries of the entirely black and the pied subspecies, suggesting an important role for plumage divergence in limiting gene flow. Overall, our findings suggest that the early diversification of the Sporophila genus occurred rapidly despite historical gene flow between lineages and that divergence in plumage color possibly influences the extent of gene flow among taxa.

Long-Term Decrease in Coloration: A Consequence of Climate Change?

AbstractClimate change has been shown to affect fitness-related traits in a wide range of taxa; for instance, warming leads to phenological advancements in many plant and animal species. The influence of climate change on social and secondary sexual traits, which are associated with fitness because of their role as quality signals, is, however, unknown. Here, we use more than 5,800 observations collected on two Mediterranean blue tit subspecies (Cyanistes caeruleus caeruleus and Cyanistes caeruleus ogliastrae) to explore whether blue crown and yellow breast patch colorations have changed over the past 15 years. Our data suggest that coloration has become duller and less chromatic in both sexes. In addition, in the Corsican C.c. ogliastrae, but not in the mainland C.c. caeruleus, the decrease is associated with an increase in temperature at molt. Quantitative genetic analyses do not reveal any microevolutionary change in the color traits over the study period, strongly suggesting that the observed change over time was caused by a plastic response to the environmental conditions. Overall, this study suggests that ornamental colorations could become less conspicuous because of warming, revealing climate change effects on sexual and social ornaments and calling for further research on the proximate mechanisms behind these effects.

Settlement Phenotypes: Social Selection and Immigration in a Common Kestrel Population

Dispersal decisions are affected by the internal state of the individual and the external environment. Immigrants entering a new population are phenotypically different from residents due to selection that mitigate costs of dispersal and facilitate settlement. Sexual and status signaling traits may influence individual’s ability to settle in a population, either by showing a subordinate phenotype thus reducing aggressive interactions, or by signaling a more competitive phenotype, thus gaining local breeding resources, including mates. By comparing immigrants vs. residents in a common kestrel population across 17 years, we evaluated the influence of dispersal on fitness components (laying date, clutch size and number of fledglings) and investigated if sex, age and phenotypic traits (body size, body condition and plumage coloration) involved in movement and social interactions affected settlement. We found that population characteristics affected sexes and age classes differently, as the admission of females and young males into our population had fewer obstacles than the admission of males. In females, immigrant young were larger, had longer wings and tails, showed better body condition, had less gray tails, started breeding earlier, and laid larger clutches than residents. Adult female immigrants also showed better body condition and less gray tails. In males, immigrants had longer tails and higher number of black spots than residents. Summarizing, immigrants are good-quality individuals and, as deduced from their breeding performance, they benefited by signaling subordination, thus reducing the probability of aggressive encounters and facilitating settlement. Our study highlights the role of phenotypic traits related to signaling to study dispersal.

Effects of genetic vs. environmental quality on condition-dependent morphological and life history traits in a neriid fly.

Condition is assumed to reflect both genes and environment, enabling condition‐dependent signals to reveal genetic quality. However, because the phenotypic effects of variation in genetic quality could be masked by environmental heterogeneity, the contribution of genetic quality to phenotypic variation in fitness‐related traits and condition‐dependent signals remains unclear. We compared effects of ecologically relevant manipulations of environmental quality (nutrient dilution in the larval diet) and genetic quality (one generation of inbreeding) on male and female morphology, life history and reproductive performance in the neriid fly Telostylinus angusticollis. We found that larval diet quality had strong, positive effects on male and female body size, male secondary sexual traits, and aspects of male and female reproductive performance. By contrast, inbreeding had weak effects on most traits, and no trait showed clear and consistent effects of both environmental and genetic quality. Indeed, inbreeding effects on body size and male competitive performance were of opposite sign in rich vs. poor larval diet treatment groups. Our results suggest that environmental quality strongly affects condition, but the effects of genetic quality are subtle and environment‐dependent in this species. These findings raise questions about the genetic architecture of condition and the potential for condition‐dependent traits to function as signals of genetic quality.

Bidirectional relationships between the gut microbiome and sexual traits.

The human gut microbiota is known to be shaped by a variety of environmental factors (diet, drugs, geography, and sanitation) and host intrinsic factors (age and sexual development). The differences in gut microbiota between sexes are minimal before adulthood and late adulthood, and marked during adulthood. For instance, consistent higher relative abundances of Akkermansia and Ruminococcus have been observed in adult women compared with men and most studies have found higher relative abundances of Prevotella and Fusobacterium (linked to a diet rich in animal proteins) in adult men compared with women. The gut microbiota taxonomy and functionality present in women is more similar to men once reached the menopause. In fact, specific taxa have been associated with the levels of different sexual hormones and their precursors in blood. The gut microbiota composition and circulating testosterone levels are also tightly linked to the extent that microbial signatures can predict its levels in blood. At the same time, the gut microbiota participates in the metabolism of sexual hormones, with some bacteria being able to metabolize gonadal steroid hormones (one example is 3β-hydroxysteroid dehydrogenase, a testosterone degrading enzyme). In summary, the relationships between the gut microbiome and sexual traits are bidirectional. In addition, other phenotypes and cultural gender-related factors could drive sex-related differences. It is important to note that other members of the microbiome (Archaea, viruses, and fungi) have been largely unexplored in relation to this sexual dimorphism. More research is needed on this topic.

Flashy male Jamaican anoles Anolis grahami show accelerated telomere attrition

Secondary sexual traits have evolved through sexual selection, many species have developed signals that can indicate their level of other fitness-relevant traits such as fight ability. Previous studies have shown that male sexual signals are honest signals about quality in an intrasexual context, demonstrating a direct relationship between the signal’s design and the fighting ability of its possessor. However, signals can be costly since conspicuous signals are more likely to attract predators or be energetically expensive. Here we have analysed if dewlap size and colouration were reliable signs of a male’s bite force, and the physiological costs associated with larger dewlaps and intense colouration in Jamaican anoles (Anolis grahami). We analysed dewlap size and colouration against bite force, and telomere attrition. Our results supported the hypothesis that dewlap size and colour intensity are honest predictors of an individual’s fighting potential as indicated by bite force. However, we have also found a relationship between colour intensity with higher telomere attrition rates, thereby indicating a possible cost of this trait for the individual.

Ewe are what ewe wear: bigger horns, better ewes and the potential consequence of trophy hunting on female fitness in bighorn sheep.

In polygynous species, secondary sexual traits such as weapons or elaborate ornaments have evolved through intrasexual competition for mates. In some species, these traits are present in both sexes but are underdeveloped in the sex facing lower intrasexual competition for mates. It is often assumed that these underdeveloped sexually selected traits are a vestige of strong sexual selection on the other sex. Here, we challenge this assumption and investigate whether the expression of secondary sexual traits is associated with fitness in female bighorn sheep. Analyses of 45 years of data revealed that female horn length at 2 years, while accounting for mass and environmental variables, is associated with younger age at primiparity, younger age of first offspring weaned, greater reproductive lifespan and higher lifetime reproductive success. There was no association between horn length and fecundity. These findings highlight a potential conservation issue. In this population, trophy hunting selects against males with fast-growing horns. Intersexual genetic correlations imply that intense selective hunting of large-horned males before they can reproduce can decrease female horn size. Therefore, intense trophy hunting of males based on horn size could reduce female reproductive performance through the associations identified here, and ultimately reduce population growth and viability.

Sexual Selection May Not Often Reduce Gene Flow Between Locally Adapted Populations. A Review of Some Evidence, and Suggestions for Better Tests

Sexually selected traits often depend on an individual’s physical condition, or otherwise indirectly reflect the ecological performance of individuals. When individuals disperse between populations that are locally adapted to different environments, their ecological performance may decline. This in turn may result in more poorly expressed sexual traits, and therefore in a lower reproductive success. Hence, sexual selection may reduce the effective gene flow between populations, and thereby maintain or even enhance population divergence. This hypothesis was published in a highly visible journal (van Doorn et al., 2009, Science). Here I review the subsequently published empirical tests of this hypothesis. I downloaded all metadata (incl. abstracts) of papers citing van Doorn et al. (2009) and read those papers that undertook relevant tests. To my surprise, only very few papers provided explicit tests of the hypothesis, this never involved plants, and only one study found support for it. While sexual selection may therefore not often reduce gene flow between locally adapted populations, some improvements to experimental design and choice of study system are noted. I therefore also provide a detailed list of suggestions for high quality tests of this hypothesis. This hopefully acts as a catalyst for more and better studies to test whether sexual and natural selection can work in synergy to reduce effective dispersal, and thereby protect and promote adaptive population divergence.

The effect of autistic traits on disembedding and mental rotation in neurotypical women and men

Recent data has revealed dissociations between social and non-social skills in both autistic and neurotypical populations. In the present study, we investigated whether specific visuospatial abilities, such as figure disembedding and mental rotation, are differently related to social and non-social autistic traits, in neurotypical women and men. University students (N = 426) completed the Autism Spectrum Quotient (AQ), figure disembedding and mental rotation of two-dimensional figures tasks. AQ social skills (AQ-social) and attention-to-details (AQ-attention) subscales were used as measures of social and non-social autistic traits, respectively. Mental rotation was affected by a significant interaction between sex, social and non-social traits. When non-social traits were above the mean (+ 1 SD), no sex differences in mental rotation were found. Instead, below this value, sex differences depended on the social traits, with men on average outperforming women at middle-to-high social traits, and with a comparable performance, and with women on average outperforming men, at lower social traits. A small positive correlation between figure disembedding and social traits was observed in the overall sample. These results are interpreted in terms of the hyper-systemizing theory of autism and contribute to the evidence of individual differences in the cognitive style of autistic people and neurotypical people with autistic traits.

Phenotypic selection on an ornamental trait is not modulated by breeding density in a pied flycatcher population

Most studies of phenotypic selection in the wild have focussed on morphological and life‐history traits and looked at abiotic (climatic) variation as the main driver of selection. Consequently, our knowledge of the effects of biotic environmental variation on phenotypic selection on sexual traits is scarce. Population density can be considered a proxy for the intensity of intrasexual and intersexual competition and could therefore be a key factor influencing the covariation between individual fitness and the expression of sexual traits. Here, we used an individual‐based data set from a population of pied flycatchers (Ficedula hypoleuca) monitored over 24 years to analyze the effect of breeding density on phenotypic selection on dorsal plumage colouration, a heritable and sexually selected ornament in males of this species. Using the number of recruits as a fitness proxy, our results showed overall stabilizing selection on male dorsal colouration, with intermediate phenotypes being favoured over extremely dark and dull individuals. However, our results did not support the hypothesis that breeding density mediates phenotypic selection on this sexual trait. We discuss the possible role of other biotic factors influencing selection on ornamental plumage.

Allometry, sexual selection and evolutionary lines of least resistance shaped the evolution of exaggerated sexual traits within the genus Tyrannus.

Variational properties hold a fundamental role in shaping biological evolution, exerting control over the magnitude and direction of evolutionary change elicited by microevolutionary processes that sort variation, such as selection or drift. We studied the genus Tyrannus as a model for examining the conditions and drivers that facilitate the repeated evolution of exaggerated, secondary sexual traits in the face of significant functional limitations. In particular, we explore the role of allometry, sexual selection and their interaction, on the diversification of tail morphology in the genus, assessing whether and how they promoted or constrained phenotypic evolution. Non-deep-forked species tend to show reduced sexual dimorphism and moderate allometric variation in tail shape. The exaggerated and functionally constrained long feathers of deep-forked species, T. savana and T. forficatus, which show both marked sexual dimorphism and allometric tail shape variation, independently diverged from the rest of the genus following the same direction of main interspecific variation accrued during the evolution of non-deep-forked species. Moreover, the latter direction is also aligned with axes summarising sexual dimorphism and allometric variation on deep-forked species, a feature lacking in the rest of the species. Thus, exaggerated tail morphologies are interpreted as the result of amplified divergence through reorientation and co-option of allometric variation by sexual selection, repeatedly driving morphology along a historically favoured direction of cladogenetic evolution.

Sexual reproduction trait expressions of grassland species along a gradient of nitrogen: phosphorus stoichiometry

AimsPlant investment in sexual reproduction is affected by nitrogen (N): phosphorus (P) stoichiometry. It has been suggested that an important adaptation to strong P limitation is reduced investment in sexual reproduction. We aim to investigate the specific influence of N:P on sexual reproduction performance within and between grassland species.MethodsEleven grassland species were selected in ten plots covering N limitation, co-limitation and P limitation. Nutrients in soil and above-ground biomass were determined, plus soil pH and soil moisture. A range of sexual reproduction traits were measured as a proxy for investment in sexual reproduction.ResultsAt the intraspecific level: compared with N-limited plots, in P-limited/co-limited plots, flowering time was later, flowering period in individuals was shorter, and number of flowers (inflorescences) per individual was smaller. At the interspecific level, in P-limited/co-limited plots, species had a significantly earlier flowering time and a longer seed stalk and seed panicle, than those in N-limited plots. However, flowering period was shorter and number of flowers (inflorescences) per individual was smaller under P limitation/co-limitation. Moreover, significant correlations between soil pH and soil moisture, and sexual reproduction performance of the selected grassland species were also found.ConclusionsP limitation/co-limitation restrict the sexual reproduction of grassland species, which may hamper their dispersal capacity. We recommend future studies further analyze the relationship between soil pH and N:P stoichiometry and the influence of soil pH, as well as soil moisture on sexual reproduction performance of grassland species in addition to analyzing N:P stoichiometry.

A comprehensive overview of the effects of urbanisation on sexual selection and sexual traits.

ABSTRACTUrbanisation can affect mating opportunities and thereby alter inter‐ and intra‐sexual selection pressures on sexual traits. Biotic and abiotic urban conditions can influence an individual's success in pre‐ and post‐copulatory mating, for example through impacts on mate attraction and mate preference, fertilisation success, resource competition or rival interactions. Divergent sexual selection pressures can lead to differences in behavioural, physiological, morphological or life‐history traits between urban and non‐urban populations, ultimately driving adaptation and speciation. Most studies on urban sexual selection and mating interactions report differences between urban and non‐urban populations or correlations between sexual traits and factors associated with increased urbanisation, such as pollution, food availability and risk of predation and parasitism. Here we review the literature on sexual selection and sexual traits in relation to urbanisation or urban‐associated conditions. We provide an extensive list of abiotic and biotic factors that can influence processes involved in mating interactions, such as signal production and transmission, mate choice and mating opportunities. We discuss all relevant data through the lens of two, non‐mutually exclusive theories on sexual selection, namely indicator and sensory models. Where possible, we indicate whether these models provide the same or different predictions regarding urban‐adapted sexual signals and describe different experimental designs that can be useful for the different models as well as to investigate the drivers of sexual selection. We argue that we lack a good understanding of: (i) the factors driving urban sexual selection; (ii) whether reported changes in traits result in adaptive benefits; and (iii) whether these changes reflect a short‐term ecological, or long‐term evolutionary response. We highlight that urbanisation provides a unique opportunity to study the process and outcomes of sexual selection, but that this requires a highly integrative approach combining experimental and observational work.

Reproductive Isolation in the Cryptic Species Complex of a Key Pest: Analysis of Mating and Rejection Behaviour of Onion Thrips (Thrips tabaci Lindeman).

Simple SummaryThe onion thrips (Thrips tabaci), which is a key pest worldwide, includes three characteristic, distinct groups (i.e., lineages) under the same species name. In the current report, we addressed the question of whether individuals from these lineages recognize and assess each other as potential mating partners. We demonstrated that at least two of these lineages do not belong to the same species, since under our laboratory conditions no mating occurred between them. Moreover, specimens from these cross pairings often exhibited an escape response upon contact with the other thrips, while most of the pairs from the same lineages readily mated at their first interaction. The behaviour of males clearly indicated that they can assess the mating status of a female and usually only try to copulate with virgins. Our findings are important not only because in agriculture it is vital to know whether morphologically similar entities belong to the same species, but also because knowledge about the communication of insects and the possible role of the cues involved can help the development of new plant protection techniques.Thrips tabaci Lindeman is a serious pest of various cultivated plants, with three, distinct lineages within a cryptic species complex. Despite the well-known significance of this pest, many attributes of these lineages are not yet fully understood, including their reproductive behaviour. We performed no-choice-design cross-mating experiments under a controlled laboratory environment with virgin adult individuals from all three lineages. The behaviour of thrips was recorded with a camera mounted on a stereomicroscope, and the recordings were analysed in detail. We found that the so-called leek-associated lineages of this cryptic species complex are reproductively isolated from the tobacco-associated lineage; therefore, they represent different species. Divergence in the behaviour of conspecific and heterospecific pairs became evident only after contact. There were no marked differences between the lineages in their precopulatory and copulatory behaviour, except in the duration of the latter. We confirmed mating between thelytokous females and arrhenotokous males; however, we assume some form of loss of function in the sexual traits of asexual females. The post-mating behaviour of males indicated the presence and role of an anti-aphrodisiac pheromone. We also demonstrated differences between lineages regarding their activity and their propensity for exhibiting an escape response upon interaction with heterospecific thrips.

Sperm competition intensity affects sperm precedence patterns in a polyandrous gift-giving spider.

Sperm competition drives traits that enhance fertilization success. The amount of sperm transferred relative to competitors is key for attaining paternity. Female reproductive morphology and male mating order may also influence fertilization, however the outcome for sperm precedence under intense sperm competition remains poorly understood. In the polyandrous spider Pisaura mirabilis, males offer nuptial gifts which prolong copulation and increase sperm transfer, factors proposed to alter sperm precedence patterns under strong sperm competition. First, we assessed the degree of female polyandry by genotyping wild broods. A conservative analysis identified up to four sires, with a mean of two sires per brood, consistent with an optimal mating female rate. Then we asked whether intense sperm competition shifts sperm precedence patterns from first male priority, as expected from female morphology, to last male advantage. We varied sexual selection intensity experimentally and determined competitive fertilization outcome by genotyping broods. In double matings, one male monopolised paternity regardless of mating order. A mating order effect with first male priority was revealed when females were mated to four males, however this effect disappeared when females were mated to six males, probably due to increased sperm mixing. The proportion of males that successfully sired offspring drastically decreased with the number of competitors. Longer copulations translated into higher paternity shares independently of mating order, reinforcing the advantage of traits that prolong copulation duration under intense competition, such as the nuptial gift. Sperm competition intensity enhances the impact of competitive sexual traits and imposes multiple effects on paternity.

A High-Density Genetic Map and QTL Fine Mapping for Growth- and Sex-Related Traits in Red Swamp Crayfish (Procambarus clarkii).

Red swamp crayfish (Procambarus clarkii) is a commercially important species in global aquaculture and most successfully invasive freshwater shrimp in China. In order to determine the genetic basis of growth- and sex-related traits, a high-density genetic linkage map was constructed using 2b-RAD sequencing technology in a full-sib family. The consensus map contains 4,878 SNP markers assigned to 94 linkage groups (LGs) and spanned 6,157.737 cM with an average marker interval of 1.26 cM and 96.93% genome coverage. The quantitative trait locus (QTL) mapping for growth and sex traits was performed for the first time. QTL mapping uncovers 28 QTLs for growth-related traits in nine LGs, explaining 7.9–14.4% of the phenotypic variation, and identifies some potential candidate growth-related genes such as mih, lamr, golgb1, nurf301, and tbcd1 within the QTL intervals. A single major locus for sex determination was revealed in LG20 that explains 59.3–63.7% of the phenotypic variations. Some candidate sex-related genes, such as vps4bl, ssrf, and acot1, were identified in the QTL intervals and found to be differentially expressed in the muscle tissues between the females and the males. Furthermore, the identified SNPs were revealed to be female heterozygotes, suggesting that red swamp crayfish might have the female heterogametic ZZ/ZW sex determination system. The present study provides a valuable resource for marker-assisted selection and genetic improvement and for further genetic and genomic research in red swamp crayfish.

Morphometric Analysis of Orbital Cavity in South Indian Population

Introduction: Each orbital cavity is actually meant as a socket for the eyeball. The human orbit is a complicated anatomic area, which performs predominant position in the craniofacial complex.
 Aim: The aim of the study is to provide the normal reference orbital parameters for the south Indian population.
 Materials and Methods: The present study has adopted 30 south Indian dry skulls. An orbital cavity was measured using vernier callipers. With the help of vernier calliper and ruler, the measurements such as length, breadth of the orbital cavity and biorbital breadth, interorbital breadth of the orbital cavity were measured. The paired t-test is the statistical method used in this study.
 Results: The mean orbital breadth of the right orbit is 34.6±1.777 and left orbit was 34.701±1.711
 The mean orbital height of the right orbit is 33.417±1.494 and the left orbit is 33.38±1.560. The mean biorbital breadth of the orbital cavity is 94.16 ± 2.533 and means interorbital breadth of the orbital cavity is 20.615±1.172. Paired t test demonstrated no significant statistical difference between the right and left orbit.
 Conclusion: The orbital cavity additionally used for determination of sex and ethnic courses of a cadaver and its phase of the cranium that posses manipulate over sexual dimorphic traits.