Directional asymmetry and correlation of tail injury with left-side dominance occur in Serpentes (Sauropsida)

Recent evidence on directional asymmetry (DA) in species of the paraphyletic assemblage “Lacertilia” indicates a possible biological significance of this phenomenon, and we tested its occurrence in Serpentes by examining bilateral morphological characters, such as the numbers of supralabial and infralabial scutes and the diameter of the eyes, on both sides of museum specimens of seven species: Coronella austriaca, Elaphe longissima, Hierophis viridiflavus, Natrix natrix, Natrix tessellata, Platyceps saharicus, and Vipera aspis. Significant DA (not antisymmetry) occurred in at least one sex of four species and in two characters: H. viridiflavus—the number of infralabial scutes in males; N. tessellata—the diameter of the eyes in males; P. saharicus—the number of infralabial scutes in males and the diameter of the eyes in females; and V. aspis—the number of infralabial scutes in the pooled sexes. In N. tessellata and P. saharicus the DA varied geographically. Rank correlation between the DA of different characters, positive or negative, was significant in one character pair in each of three species. In the largest sample (N. tessellata males from the Levant), tail injury correlated with morphological left-dominant asymmetry (a greater number on the left) of infralabial scutes. Four of ten morphologically left-dominant males, but only 1 of 37 symmetrical or right-dominant males, had an injured tail. The syndrome of morphological DA with functional handicap may be genotypical or phenotypical. Our results support three earlier conclusions: bilateral characters should be examined on both sides of an animal; asymmetry should be analyzed separately in each sex; and the accident proneness of left-handed Homo sapiens merits re-evaluation in view of the apparently wide-spread accident proneness in left-biased Sauropsida (exclusive of Aves).     

Unusual aetosaur armor from the Upper Triassic of West Texas,U.S.A.

We report two unusual aetosaur scutes from the Tecovas Member of the Dockum Formation, Chinle Group (upper Carnian) of Crosby County, Texas, U.S.A. Originally collected by University of Michigan expeditions in the 1920’s, these scutes cannot be assigned with certainty to any known species of aetosaurs known from the American Southwest. One of these scutes may be a cervical horn ofParatypothorax, and if so confirms the similarities of this aetosaur toDesmatosuchus in the possession of horned lateral spikes. The other is a paramedian scute of a new aetosaur taxon inadequately known at present to be assigned a formal name. These scutes indicate that aetosaurs were more diverse in the Chinle Group than currently known, but do not alter the robust Late Triassic biochronology based on aetosaurs.     

Relationships among turtles of the genus Clemmys (Reptilia, Testudines, Emydidae) as suggested by plastron scute morphology

The Conservative morphology of hardshelled turtles has fostered the use of size relationships between epidermal scutes (scales) on the shell to differentiate between species and subspecies of many taxa. The size relationship of the six major pairs of plastral scutes were used to compare the four currently recognized species of the genus Clemmys with each other. as well as with the distantly related Graptemys barbouri using Jaccard Coefficients. Shannon-Weiner diversity indices, and multivariate analysis. Results were concordant among the three techniques used and confirm our prediction that plastral morphology varies little among closely related species and widely among distantly related taxa. Clemmys muhlenbergii appears to he more different from Clemmys guttata than previously suggested. Analysis of plastral morphology shows promise as a taxonomic tool for turtle systematists.     

Reproductive biology of the endemic Iranian cichlid, <Emphasis Type="Italic">Iranocichla hormuzensis</Emphasis> Coad, 1982 from Mehran River,southern Iran

We studied the reproductive biology of the endemic Iranian cichlid Iranocichla hormuzensis, a maternal mouthbrooder, in the Mehran River. Overall sex ratio was 1.44 M: 1F indicating a significant male bias. Monthly sex ratios did not differ from unity except in May and June when the sex ratios were strongly biased in favor of males. Four different reproductive indices and the high frequency of large oocytes, all suggest that the Iranian cichlid spawns at the end of winter and the beginning of spring. Mircoscopic gonadal maturation stages for both males and females were correlated to the gonadosomatic indices. The maximum number of larvae in the mouth of a female was 153.     

The defensive role of scutes in juvenile fluted giant clams (Tridacna squamosa)

This study tests the hypothesis that the scaly projections (scutes) on the shells of juvenile giant fluted clams, Tridacna squamosa, are an adaptation against crushing predators such as crabs. The forces required to crush scutes and clams were measured with a universal testing machine whereas crab chela strength was measured with a digital force gauge connected to a set of lever arms. Results for shell properties and chela strength are used to create two, non-mutually exclusive, predator–defense models. In Model 1, scutes increase the overall shell size, consequently reducing the number of crab predators with chelae that are large enough to seize and crush the prey. In Model 2, the chela has to open more to grasp a prey with these projecting structures which leads to a loss of claw-closing force such that crabs fail to crush the scutes, and consequently the clam. Clam scutes may also deter crab predators by increasing the risk of claw damage and/or handling time.     

Sites of cell proliferation during scute morphogenesis in turtle and alligator are different from those of lepidosaurian scales

Cell proliferation in forming shield scutes has been studied by immunofluorescence in embryos of turtle, alligator and snake after injection of 5‐bromo‐deoxy‐uridine. Hinge regions of scutes in alligator and turtle carapace derive from an initial waving and invagination of the epidermis that contains 5‐bromo‐deoxy‐uridine‐labelled cells. This suggests that down growth of the epidermis into the dermis is driven by local proliferation in addition to dermal anchorage and stabilization of hinge regions. Few keratinocytes migrate into suprabasal layers 1 day after injection of 5‐bromo‐deoxy‐uridine and keratinocytes reach the precorneous layer in about 5 days. Proliferating keratinocytes are randomly distributed in the outer scale surface of symmetric scutes but are more numerous in the outer scale surface of asymmetric or overlapped scutes indicating epidermal expansion. Higher localization of proliferating cells along hinge regions of embryonic turtle and alligator scutes is maintained in adult scutes where most growth occurs. In snake, skin proliferation becomes prevalent on the elongating outer side of the asymmetric scale. Comparison between proliferation sites in turtle–alligator–chick scales with lepidosaurian scales indicates that placodes are present only in turtle–alligator–chick scales. Conversely, scale primordia detected only using gene markers are found in most crocodilian and lepidosaurians embryonic skin.     

A universal and reliable assay for molecular sex identification of three‐spined sticklebacks (Gasterosteus aculeatus)

In heterogametic species, biological differences between the two sexes are ubiquitous, and hence, errors in sex identification can be a significant source of noise and bias in studies where sex‐related sources of variation are of interest or need to be controlled for. We developed and validated a universal multimarker assay for reliable sex identification of three‐spined sticklebacks (Gasterosteus aculeatus). The assay makes use of genotype scores from three sex‐linked loci and utilizes Bayesian probabilistic inference to identify sex of the genotyped individuals. The results, validated with 286 phenotypically sexed individuals from six populations of sticklebacks representing all major genetic lineages (cf. Pacific, Atlantic and Japan Sea), indicate that in contrast to commonly used single‐marker‐based sex identification assays, the developed multimarker assay should be 100% accurate. As the markers in the assay can be scored from agarose gels, it provides a quick and cost‐efficient tool for universal sex identification of three‐spined sticklebacks. The general principle of combining information from multiple markers to improve the reliability of sex identification is transferable and can be utilized to develop and validate similar assays for other species.     

Genetic variability of sexual size dimorphism in a natural population of<Emphasis Type="Italic">Drosophila melanogaster</Emphasis>: An isofemale-line approach

Most animal species exhibit sexual size dimorphism (SSD). SSD is a trait difficult to quantify for genetical purposes since it must be simultaneously measured on two kinds of individuals, and it is generally expressed either as a difference or as a ratio between sexes. Here we ask two related questions: What is the best way to describe SSD, and is it possible to conveniently demonstrate its genetic variability in a natural population? We show that a simple experimental design, the isofemale-line technique (full-sib families), may provide an estimate of genetic variability, using the coefficient of intraclass correlation. We consider two SSD indices, the female-male difference and the female/male ratio. For two size-related traits, wing and thorax length, we found that both SSD indices were normally distributed. Within each family, the variability of SSD was estimated by considering individual values in one sex (the female) with respect to the mean value in the other sex (the male). In a homogeneous sample of 30 lines ofDrosophila melanogaster, both indices provided similar intraclass correlations, on average 0.21, significantly greater than zero but lower than those for the traits themselves: 0.50 and 0.36 for wing and thorax length respectively. Wing and thorax length were strongly positively correlated within each sex. SSD indices of wing and thorax length were also positively correlated, but to a lesser degree than for the traits themselves. For comparative evolutionary studies, the ratio between sexes seems a better index of SSD since it avoids scaling effects among populations or species, permits comparisons between different traits, and has an unambiguous biological significance. In the case ofD. melanogaster grown at 25?C, the average female/male ratios are very similar for the wing (1.16) and the thorax (1.15), and indicate that, on average, these size traits are 15–16% longer in females.     

Scute’s polymorphism as a source of evolutionary development of the turtle shell

The scute mosaic (pholidosis) of the turtle shell is a complex correlated system of the modular type. Horny scutes are separate morphological elements partially closely connected with each other and partially relatively autonomous in development. The last feature causes high variability of scutes in the shape, size, rate and direction of growth, and provides the basis of transformation of the entire mosaic. In the evolution of turtles, the horny shell changed towards a decrease in the number of elements composing it. The process of oligomerization developed through reduction and fusion of scutes or their anlages. The traces of these transformations are observed in the ontogeny of living turtles. The scutes undergoing reduction display the following developmental deviations: (1) a decrease in size of the scute anlage, (2) the temporal shift in initiation to later embryonic stages, (3) absence of an anlage of a own furrow (the boundaries of the scute are formed by the furrows of neighboring scutes), and (4) a decrease in size of the zone and rate of the scute growth. The fusion of horny scutes follows two patterns: (1) fusion of scute anlages and (2) reduction of horny furrows separating scutes before. Secondary polymerization of the scute mosaic by the appearance of additional elements usually results from abnormal development and is infrequently fixed in evolution. The main mechanism of evolutionary changes in turtle pholidosis was heterochrony, i.e., the time shift in initiation and developmental rate of scutes. The heterotopies, i.e., changes in the position of scute anlages, played a minor role in the evolution of turtles; they usually caused only scute abnormalities, which was frequently asymmetrical.     

Proliferation in the epidermis of chelonians and growth of the horny scutes

The proliferation of the epidermis in soft skin, claws, and scutes of the carapace and plastron in the tortoise (Testudo hermanni) and the turtle (Chrysemys picta) were studied using autoradiographic and immunocytochemical methods. During the growing season, a basal keratinocyte in the epidermis of soft skin and claws takes 5-9 days to migrate into the corneous layer. In the tortoise, during fall/winter (resting season) a few alpha-keratin cells are produced in soft epidermis and hinge regions among scutes and occasional beta-keratin cells in the outer scute surface. When growth is resumed in spring (growing season), cell proliferation is intense, mainly around hinge regions and tips of marginal scutes. No scute shedding occurs and numerous beta-keratin cells are produced around the hinge regions, while alpha-keratin cells disappear. Beta-cells form a new thick corneous layer around the hinge regions, which constitute the growing rings of scutes. Beta-keratin cells produced in more central parts of scutes maintain a homogeneous thickness of the corneous layer along the whole scute surface. In the turtle, a more complicated process of scute growth occurs than in the tortoise. At the end of the growing season (late fall) the last keratinocytes formed beneath the old stratum corneum of the outer scale surface and hinge regions produce more alpha- than beta-keratin. These thin alpha-keratin cells form a scission layer below the old stratum corneum, which extends from the hinge regions toward the center of scutes and the tip of marginal scutes. In the resting season (fall/winter) most cells remain within the germinative layer of the carapace and plastron and a few alpha-cells move in 7-9 days into the corneous layer above hinge regions. In the following spring/summer (growing season) a new generation of beta-keratin cells is produced beneath the scission layer from the hinge region and more central part of the scutes. The epidermis of the inner surface of scutes and hinge regions contains most of the cells incorporating thymidine and histidine, while the remaining outer scute surface is less active. It takes 5-9 days for a newly produced beta-cell to migrate into the corneous layer. These cells form a new corneous layer that extends the whole scute surface underneath the maturing scission layer. The latter contains lipids and eventually flakes off, determining shedding of the above outer corneous layer in late spring or summer.     

Developmental structure of the vertebral column,fins, scutes and scales in bester sturgeon,a hybrid of beluga Huso huso and sterlet Acipenser ruthenus

In the larval bester, a hybrid sturgeon of beluga Huso huso and sterlet Acipenser ruthenus, development of cartilage around the notochord began 7 days post hatch (dph) (14·0 mm, total length, L_T). The vertebral cartilage develops in the following sequence: basidorsals and basiventrals, neural canals, neural spines and ribs. The development of ribs remained incomplete in the largest specimen (181 dph, 179 mm L_T) that was examined. Endoskeletal development of the fins began 4 dph for the dorsal and anal fins, 6 dph for the pectoral fin and 10 dph for the caudal and pelvic fins. Complete elements of all fins were observed by 91 dph and complete ossification of fin rays was observed by 122 dph in the double‐stained specimens. Observation of the histological sections, however, suggested that ossification occurred soon after the formation of the organic matrix in the fin rays. Dorsal scutes were first visible by 25 dph, followed by the lateral and ventral scutes, which were visible by 37 and 44 dph, respectively. The number of scutes was fixed at 44, 59 and 91 dph and ossification was complete by 59 (dorsal) and 91 dph (lateral and ventral scutes) in the double‐stained specimens. Ossification occurred soon after the formation of the scute organic matrix in the histological sections. Four types of scales were observed in the H. huso×A. ruthenus hybrid. Median predorsal, preanal and small scales on the anterior section of the head were visible by 59 dph. Scales on the caudal fin were visible by 91 dph and a variable assemblage of scales anterior to the anal fin was visible by 122 dph. Both the scutes and scales developed in a process that is similar to that of intramembranous ossification.     

Comparing aging precision of calcified structures in shovelnose sturgeon

Age estimates for population analysis must be precise. We assessed the usefulness of pectoral fin rays, sphenoids, opercula, and dorsal scutes of shovelnose sturgeonScaphirhynchus platorynchus (n = 30) as aging structures based on ease of collection, distinctness of annuli, and measures of precision both between and within readers. We also determined how age estimates from paired fin rays of individuals were related (n = 106). Pectoral fin rays generated the highest within‐reader precision (100% within 2 years) followed by sphenoids (58%), opercula (56%), and dorsal scutes (49%). Ages estimated by the pectoral fin ray also had higher between‐reader agreement (80% within 1 year) than did those from the operculum (60%), sphenoid (59%), or dorsal scute (56%). Likewise, age estimates from pectoral fin rays had the lowest mean coefficient of variation (8.2%) followed by sphenoids (9.9%), opercula (11.3%), and dorsal scutes (11.5%). Only the operculum produced biased estimates between readers. Ages from paired fin rays agreed poorly (36% exact, 30% within 1 year) although no aging bias occurred. The pectoral fin ray is typically used to age shovelnose sturgeon. Because uncertainty about accuracy and precision of age estimates from this structure remains, shovelnose sturgeon management objectives that result from age data should remain conservative.     

A survey of the epibiota of Eretmochelys imbricata (Testudines: Cheloniidae) of Mona Island, Puerto Rico

Epibiotic organisms inhabiting non-nesting hawksbill sea turtles, Eretmochelys imbricata (Linnaeus, 1766), are described from Mona and Monito Islands, Puerto Rico. Epibiont samples from 105 turtles of shallow (< 40 m) water foraging habitats were collected and identified to the lowest possible taxon. This epibiotic assemblage consisting of at least 4 algal functional groups and 12 animal phyla represents the greatest phylogenetic diversity for marine turtle epibiota. Six groups are considered new reports for marine turtles. Most epibiont colonization was found on posterior marginal scutes and under overlapping scutes. Ecological attributes of epibiota and their symbiosis with E. imbricata provide a tool to understand basi and epibiont populations.     

A simple and improved PCR-based technique for white-tailed deer (<Emphasis Type="Italic">Odocoileus virginianus</Emphasis>) sex identification

We describe a simple single-reaction technique for identifying the sex of white-tailed deer (Odocoileus virginianus) based on the PCR amplification of a zinc-finger intron using one pair of primers. Although Sry-coamplification confirmed sex identities, use of the Sry marker was unnecessary due to dimorphic alleles on the X and Y chromosomes at the zinc-finger locus. Insertions in intron 7 of the Y-linked allele (417 bp) make it nearly twice as long as the X-linked allele (236 bp) and thus the amplification products are easily discernable by simple agarose gel electrophoresis. The relatively short size of these products makes them useful for DNA-based sex identification from potentially low-yield tissue samples (e.g., hair, feces). This technique will provide ecologists, conservation geneticists and wildlife managers with a mechanism to readily and reliably identify the sex of unknown white-tailed deer tissue samples, and likely similar samples from other cervid species.     

Effects of the egg incubation environment on turtle carapace development

Developing organisms are often exposed to fluctuating environments that destabilize tissue-scale processes and induce abnormal phenotypes. This might be common in species that lay eggs in the external environment and with little parental care, such as many reptiles. In turtles, morphological development has provided striking examples of abnormal phenotypic patterns, though the influence of the environment remains unclear. To this end, we compared fluctuating asymmetry, as a proxy for developmental instability, in turtle hatchlings incubated in controlled laboratory and unstable natural conditions. Wild and laboratory hatchlings featured similar proportions of supernumerary scales (scutes) on the dorsal shell (carapace). Such abnormal scutes likely elevated shape asymmetry, which was highest in natural nests. Moreover, we tested the hypothesis that hot and dry environments cause abnormal scute formation by subjecting eggs to a range of hydric and thermal laboratory incubation regimes. Shape asymmetry was similar in hatchlings incubated at five constant temperatures (26–30°C). A hot (30°C) and severely Dry substrate yielded smaller hatchlings but scutes were not overtly affected. Our study suggests that changing nest environments contribute to fluctuating asymmetry in egg-laying reptiles, while clarifying the conditions at which turtle shell development remains buffered from the external environment.     

Social Dominance Hierarchies and Phenotypic Correlates of Dominance in Captive Groups of the Grey‐cheeked Fulvetta Alcippe morrisonia in Taiwan

Dominance hierarchies usually form quickly among avian foraging groups because they are beneficial to most individuals by reducing conflict. Several characteristics that correlate with dominance rank have been identified in birds, but most of these conclusions rely on studies of temperate species. Hence, we studied whether captive group members of a subtropical species, grey‐cheeked fulvetta Alcippe morrisonia, form social dominance hierarchies when competing for food during the non‐breeding season. We also investigated whether sex, age, body condition and fat score were related to an individual's dominance rank which was established by counting aggressive interactions in six captive groups of nine individuals each. In all groups, linear dominance hierarchies were formed whereby yearlings dominated over adult birds, and individuals with a better body condition were also more dominant, while sex and fat score had no discernable effect. Male yearlings had significantly higher body masses and body condition indices than male adults, while female yearlings had significantly higher body masses, body condition indices and fat scores than female adults. However, there were no significant differences between male and female yearlings or adults for any of these variables. We suggest possible reasons for the dominance of yearlings, such as captive conditions or the higher body weight of yearlings.     

Local and neighboring patch conditions alter sex‐specific movement in banana weevils

Understanding the mechanisms underlying the movements and spread of a species over time and space is a major concern of ecology. Here, we assessed the effects of an individual's sex and the density and sex ratio of conspecifics in the local and neighboring environment on the movement probability of the banana weevil, Cosmopolites sordidus. In a “two patches” experiment, we used radiofrequency identification tags to study the C. sordidus movement response to patch conditions. We showed that local and neighboring densities of conspecifics affect the movement rates of individuals but that the density‐dependent effect can be either positive or negative depending on the relative densities of conspecifics in local and neighboring patches. We demonstrated that sex ratio also influences the movement of C. sordidus, that is, the weevil exhibits nonfixed sex‐biased movement strategies. Sex‐biased movement may be the consequence of intrasexual competition for resources (i.e., oviposition sites) in females and for mates in males. We also detected a high individual variability in the propensity to move. Finally, we discuss the role of demographic stochasticity, sex‐biased movement, and individual heterogeneity in movement on the colonization process.     

A method for estimating population sex ratio for sage‐grouse using noninvasive genetic samples

Population sex ratio is an important metric for wildlife management and conservation, but estimates can be difficult to obtain, particularly for sexually monomorphic species or for species that differ in detection probability between the sexes. Noninvasive genetic sampling (NGS) using polymerase chain reaction (PCR) has become a common method for identifying sex from sources such as hair, feathers or faeces, and is a potential source for estimating sex ratio. If, however, PCR success is sex‐biased, naively using NGS could lead to a biased sex ratio estimator. We measured PCR success rates and error rates for amplifying the W and Z chromosomes from greater sage‐grouse (Centrocercus urophasianus) faecal samples, examined how success and error rates for sex identification changed in response to faecal sample exposure time, and used simulation models to evaluate precision and bias of three sex assignment criteria for estimating population sex ratio with variable sample sizes and levels of PCR replication. We found PCR success rates were higher for females than males and that choice of sex assignment criteria influenced the bias and precision of corresponding sex ratio estimates. Our simulations demonstrate the importance of considering the interplay between the sex bias of PCR success, number of genotyping replicates, sample size, true population sex ratio and accuracy of assignment rules for designing future studies. Our results suggest that using faecal DNA for estimating the sex ratio of sage‐grouse populations has great potential and, with minor adaptations and similar marker evaluations, should be applicable to numerous species.