Plastron Length Research Articles

Morphometric Study of African Spurred Tortoise (Centrochelys sulcata) Based on Age Group

Centrochelys sulcata are kept and bred to prevent extinction. The sulkata tortoises were identified to determine their respective identities by measuring them morphometrically. Morphometric studies on sulkata tortoises are still minimal, so a morphometric study of the sulkata tortoises is needed. The purpose of this study was to identify and describe the morphometry of sulcata tortoises with three different age ranges kept in ex-situ conservation. The research sample used 15 sulcata turtles which were divided into 3 groups namely group A (1 year), Group B (2 years), and Group C (3 years). The morphometric parameters measured were body weight, head, carapace, plastron, forelimb, hindlimb and bridge. The results showed that the average body weight of group A, B and C turtles was 2,179 kg, 1,289 kg and 0,167 kg respectively. The average maximum carapace length in a row for groups A, B, C, namely 11.64, 23.18 and 16.72 cm. The average plastron lengths for groups A, B, C were 9.08, 6.44 and 9.24 cm respectively. The average forelimb length in groups A, B and C were 3.04, 6.28 and 7.78 cm respectively. The average hindlimb length for groups A, B, and C were 1.86, 3.5 and 4.04 cm, respectively. The average bridge width for groups A, B and C were 4.36, 8.94 and 10.1 cm respectively. Based on the results of morphometric measurements of the three groups of sulcata tortoises, it was shown that group C had a larger morphometric size than groups B and A, this was due to differences in age and growth factors. Sulcata tortoises group C is 3 years old and belongs to the juvenile group. Sulcata tortoise groups A and B aged 1 and 2 years are included in the yearly group

Development and evaluation of a medium-free incubation method for hatching Chinese soft-shelled turtle (Pelodiscus sinensis) eggs

In aquaculture, the traditional method for hatching Pelodiscus sinensis eggs needs further investigation. Here, we developed a medium-free incubation method for hatching P. sinensis eggs and evaluated its differences from the traditional vermiculite incubation method and the effects of light on it. We found that medium-free incubation had no significant effects on hatching success, body weight, carapace length, carapace width, plastron length, plastron width, and righting response time of P. sinensis compared with those under traditional vermiculite incubation, irrespective of thermostatic or fluctuating temperature conditions. Furthermore, light treatment significantly shortened the incubation period and negatively affected body weight, carapace length, carapace width, plastron length, and righting response time during medium-free incubation. Additionally, this study is the first to report the phenomenon of egg-hatching synchrony in P. sinensis. Overall, our results provide basic data and novel insights for improving the method for hatching P. sinensis eggs.

Biometrics of neonates and characterization of the Amazon Turtle (Podocmenis expansa) nests in the Crixás-açu river, Mundo Novo, Goiás, Brazil

The objective of this study was to evaluate newborn biometrics and characterization of Podocnemis expansa turtle nests in the Crixás-Açu rivers, municipalities of Mundo Novo, Goais, Brazil. It consists of evaluating the newborns and the characterization of the nests after hatching. There was no statistical difference between eggs with oil, predatory nests, dead newborns, un hatched eggs, shell (total number of eggs counted within a nest), as well as hatching and survival rates for the distance of 30 meters from the river course. Animal weight, hoof length, hoof width, plastron length, plastron width or number of shields were obtained statistically significant considering the same fixed distance of 30 or greater than 30 meters from the river bank. In the eggshell analysis, there was a statistical difference regarding the amount of the element "Carbon" found, unlike the samples of pH, "phosphorus", "potassium", "hydrogen", "aluminium", "calcium", "magnesium" and matter. Organic. As for the particle size analysis of the sand extracted from the nests, there was a statistical difference in two sizes; 1 and 2 millimeters. This study shows that nests near vegetation are more successful in hatching.

Sustainability of the plastron on nano-grass-covered micro-trench superhydrophobic surfaces in high-speed flows of open water

This paper studies the sustainability of plastrons on superhydrophobic (SHPo) surfaces made of longitudinal micro-trenches covered by nano-grass with the main interest on hydrodynamic friction drag reduction in high-speed flows of open water, which represent the operating conditions of common watercraft. After revising the shear-driven drainage model to address the air diffusion for SHPo surfaces, the existing theories are combined to reveal the trends of how the immersion depth, air saturation level and shear stress affect the maximum attainable plastron length. Deviations from the theories by the dynamic effect at the two ends of the trench, the interfacial contaminations and turbulent fluctuation are also discussed. A combinatorial series of well-defined SHPo trench surfaces (4 cm × 7 cm in size with varying trench widths, depths, lengths and roughnesses) is microfabricated and attached underneath a 4 m long motorboat on seawater in turbulent flows up to 7.2 m s−1(shear rate ∼83 000 s−1and friction Reynolds number ∼5500). Because the plastron can provide a substantial slip only while its air–water interfaces are pinned (or only slightly depinned) at the trench top, two underwater cameras are employed to differentiate the pinned (and slightly depinned) interfaces from the depinned (and no) interfaces. In addition to achieving pinned plastrons on 6 cm long trenches aligned to high-speed flows in open water, the experimental results corroborate the theoretical estimations, supporting the design of SHPo surfaces for field applications.

Pengaruh Suhu Inkubasi Terhadap Profil Ekspresi Gen Determinasi Seks Tukik Lepidochelys olivacea

Sex determination in turtles is not only based on genotype, but also depends on the incubation temperature. In addition, sex differentiation takes place during the thermosensitive period (TSP). This review article aims to examine the effect of incubation temperature on the expression profile of the sex determination gene for tortoises. Fertile eggs are incubated at two temperatures, namely the feminine temperature (30-33 ° C), and the masculine temperature (26-27 ° C). The results of bioreproduction and phenotype measurements of hatchlings, namely, embryo growth, incubation time, morphometrics, and locomotor performance of hatchlings were analyzed by regression analysis and Student's t test. The results of analysis from several literatures showed that the expression of aromatase and Rspond 1 genes (which play a role in ovarian differentiation) after TSP from incubated embryos at a higher feminine temperature and different from the masculine temperature. Regarding bioreproduction, the incubation period at the feminine temperature is shorter than the masculine temperature. Likewise embryos grow more rapidly at feminine temperatures. Incubation at feminine temperature had a significant effect on the phenotype of hatchlings, namely carapace width, plastron length and width, long flipper and hind arms, long neck, and flipper swing frequency.

Fecundity, Female Maturation, and Nesting Season of Western Chicken Turtles (Deirochelys reticularia miaria) in Texas

The reproductive lifespans of turtles are consistently long, but reproductive cycles are under environmental control and thus can vary within species, populations, and individuals over time and space. Knowledge of turtle species' reproductive traits and their associated variances over time and space are critical to understanding the dynamics of turtle populations, especially those requiring management or conservation. Deirochelys reticularia is a species being considered for protection by the US Fish and Wildlife Service and contains 3 subspecies with some differences in reproductive characteristics of nesting season, annual nesting frequency, and egg retention. We collected ultrasound and x-radiograph data in Texas to identify the maturation size, nesting season, annual nesting frequency, and clutch size of female D. r. miaria in Texas. We observed no reproductive activity in individuals from 101 to 146 mm in plastron length (PL) and detected either unshelled eggs, shelled eggs, or both in individuals from 150 to 197 mm PL. Maturation sizes were similar to those in other regions and for other subspecies. We observed shelled clutches or nesting events from April to July, confirming a spring–summer nesting season in Texas consistent with other D. r. miaria sites and supporting the paradigm that the western subspecies does not follow the autumn–winter nesting season of the other subspecies. We found no evidence that individuals retain shelled eggs while aestivating or overwintering. Individuals nested up to 3 times/yr in Texas. Individuals laid 7–11 eggs and the mean clutch size was 9.2 eggs, similar to other regions and other subspecies. Nesting phenology is regionally variable, so management plans and policies for the species will need to consider that variation and potentially recognize management differences among D. reticularia subspecies.

Clutch Size, Clutch Frequency, and Egg Characteristics of Diamond-Backed Terrapins (Malaclemys terrapin) in Southwestern Louisiana

The reproductive output of Malaclemys terrapin (Diamond-backed Terrapin) is highly variable across its geographic range. While much of the literature is based on populations from the Atlantic coast of the United States, little reproductive-output data exists for the Gulf of Mexico populations. We captured female Diamond-backed Terrapins in southwestern Louisiana and assessed their reproductive output using radiographic- and ultrasound-imaging techniques. X-rays identified that average clutch size was 7.2 and average egg width was 21.9 mm. We revealed a positive relationship between female size (plastron length) and both clutch size and egg width, but no relationship between egg size and clutch size. Ultrasound imaging in a subset of individuals revealed large pre-ovulatory follicles and fully shelled eggs concurrently in females, indicating the potential for at least 2 clutches annually in this region. Our results suggest Diamond-backed Terrapins in southwestern Louisiana show variation in reproductive output compared to other populations at similar latitudes, indicating the need for additional study within and between populations in the region.

Morphometric study of Balkan Terrapin, Mauremys rivulata (Testudines: Geoemydidae) in Çanakkale (Turkey)

Mauremys rivulata (Family Geoemydidae) is a medium-sized freshwater turtle inhabiting various natural and manmade habitats, including rivers, seasonal ponds, lakes, brackish coastal lagoons, irrigation canals, and reservoirs. In this study, the morphology of four different Mauremys rivulata populations in Çanakkale was evaluated between populations and sexes. The straight carapace length (SCL), carapace width (CW), plastron length (PL), plastron width (PW), body weight (W) measurements were obtained from a total of 114 adult specimens from four populations. The body sizes were examined comparatively in four Mauremys rivulata populations from Kavak Delta located in the Thrace region, City Center located in Anatolia, and two islands (Gökçeada and Bozcaada) which are the districts of Çanakkale. Significant differences were found between males and females in all populations, with females being larger than males. When the four populations were compared, it was determined that Gökçeada population is the largest specimens (Female SCL 197,23±7,545; Male SCL 187,47±13,757) and City Center population is the smallest specimens (Female SCL 152,02±23,391; Male SCL 129,67±20,466).

Breeding Biology of Northern River Terrapin Batagur Baska in Captivity in Bangladesh

Northern River Terrapin, Batagur baska, is an ecologically extinct species in Bangladesh. The ‘Project Batagur’ has undertaken some important initiatives to resuscitate the nearly deceased population through captive breeding at Bhawal National Park, Gazipur, Bangladesh. We conducted a study on breeding biology of B. baska from May 2016 to June 2017 in the project site. Four adult females and three adult males comprised breeding pair in the study site. Male Batagur baska developed black colouration on head and neck, with rich crimson on dorsal portion of the neck during breeding season. During our study, we observed paired basking behaviour rather courtship and parental care. We found three nests from mid-March to first week of April. Females laid eggs at night and a total of 67 eggs were extracted from three nests; eggs were elliptical and whitish in colour. Clutch size varied from 18 to 28 eggs. There was significant positive correlation between clutch size and nest diameter (p = 0.03). The relationship was also positive and significant between egg weight and diameter (p = 0.01).The size of the egg was not related with the size of breeding females (r = 0.143).Average incubation period was (68.26 ± 5.23) days and there was significant negative relationship with temperature (p= 0.000), clutch size (p = 0.001), and hatching success (p = 0.004). Hatching success was also negatively co-related with temperature (p= 0.001). Hatching started in May and ended in the first week of June 2017 with mean hatching success of 91%. Simple linear regression showed positive relationship between egg length and hatchlings’ carapace length, plastron length, and height. We also found positive relationship between egg diameter and hatchlings weight, and carapace width. This study can be used as a protocol for captive breeding and rearing activities of threatened chelonians around the world. Dhaka Univ. J. Biol. Sci. 31(1): 67-78, 2022 (January)

Reproductive biology of the Rote Snake-necked Turtle Chelodina mccordi (Rhodin, 1994) in Oelsonbai Captivity, Kupang

The Rote snake-necked turtle (Chelodina mccordi Rhodin, 1994) or Kura-kura Leher Ular Rote is an endangered species endemic to Rote Island, East Nusa Tenggara. It is listed as Critically Endangered by the IUCN. However, based on surveys in recent years, C. mccordi was presumed extinct in the wild. Ex-situ conservation is one alternative to conserve C. mccordi. The purpose of this paper is to describe the reproductive biology of the Rote snake-necked turtle in captivity. Three (one male and two female) C. mccordi were observed in Oelsonbai captivity, Kupang, from 2009 to 2020 to obtain data on the species’ reproductive biology. The first mating behaviour was observed when the turtles were six years old. Hatches occurred two or three times a year, with clutch size varied from five to twenty eggs. Egg hatchability was 75-100 percent, with an incubation period of 76 to 102 days. Female size when mature straight-line carapace length (SCL) 178 mm, carapace width 145 mm, and plastron length 142 mm. Male size straight-line carapace length (SCL) 190 mm, carapace width 150 mm, and plastron length 143 mm.

Terrapin Station: Individual, Sex, and Site Factors Related to Turtle Growth Variability

For many turtle species, life history traits such as body size, age at maturity, and somatic growth rate can vary among individuals and habitats and between the sexes. Therefore, it is important to consider factors that may influence growth when modeling (somatic) growth for turtles. Long-term capture–mark–recapture studies lend themselves to studying somatic growth in turtles due to the repeated measurements of individuals over time. We used a long-term dataset to examine growth patterns of philopatric Diamondback Terrapins (Malaclemys terrapin) on Kiawah Island, South Carolina, USA. We used a hierarchical three-parameter von Bertalanffy model to estimate individual growth of 44 female and 36 male Diamondback Terrapins that were each captured 3–17 times between 1983 and 2019. Sex and site (i.e., tidal creeks) were included as second-level model effects. Mean maximum asymptotic size (plastron length; L ∞ = 173.4 mm for females and L ∞ = 104.4 mm for males) and mean growth coefficients (K = 0.28 for females and K = 0.61 for males) varied between sexes. Growth variability among individuals was high, ranging from 23 to 56% within species for different parameters, suggesting that models not accounting for individual variability would be pooling dissimilar information. Site was a significant covariate for male growth, but not female growth. Understanding how Diamondback Terrapin somatic growth varies within a population may inform habitat quality as well as population health and vulnerability to anthropogenic stressors. Our model can serve as a comparison for other Diamondback Terrapin populations and provide more detailed information for demographic models that can be used in conservation decisions.

Influence of Herbicide Exposure and Ranavirus Infection on Growth and Survival of Juvenile Red-Eared Slider Turtles (Trachemys scripta elegans).

Ranaviruses are an important wildlife pathogen of fish, amphibians, and reptiles. Previous studies have shown that susceptibility and severity of infection can vary with age, host species, virus strain, temperature, population density, and presence of environmental stressors. Experiments are limited with respect to interactions between this pathogen and environmental stressors in reptiles. In this study, we exposed hatchling red-eared slider turtles (Trachemys scripta elegans) to herbicide and ranavirus treatments to examine direct effects and interactions on growth, morbidity, and mortality. Turtles were assigned to one of three herbicide treatments or a control group. Turtles were exposed to atrazine, Roundup ProMax®, or Rodeo® via water bath during the first 3 weeks of the experiment. After 1 week, turtles were exposed to either a control (cell culture medium) or ranavirus-infected cell lysate via injection into the pectoral muscles. Necropsies were performed upon death or upon euthanasia after 5 weeks. Tissues were collected for histopathology and detection of ranavirus DNA via quantitative PCR. Only 57.5% of turtles exposed to ranavirus tested positive for ranaviral DNA at the time of death. Turtles exposed to ranavirus died sooner and lost more mass and carapace length, but not plastron length, than did controls. Exposure to environmentally relevant concentrations of herbicides did not impact infection rate, morbidity, or mortality of hatchling turtles due to ranavirus exposure. We also found no direct effects of herbicide or interactions with ranavirus exposure on growth or survival time. Results of this study should be interpreted in the context of the modest ranavirus infection rate achieved, the general lack of growth, and the unplanned presence of an additional pathogen in our study.

Comparative Reproductive Allometry of Syntopic Black-Knobbed Sawbacks (Graptemys nigrinoda) and Alabama Map Turtles (Graptemys pulchra) in the Alabama River, with Comparison to Three Congeners

In many freshwater turtle species, increasing adult female body size is accompanied by increases in both clutch size and egg size. Because clutch size and egg size represent competing sinks for the increasing abdominal space that can be devoted to reproductive potential as a female grows larger, both are hypoallometrically related to body size, i.e., each increases at less than the rate at which body size is increasing. I studied the reproductive allometry of 2 species of the map turtle and sawback genus (Emydidae: Graptemys) in syntopy in the Alabama River. Relative to congeners, Graptemys nigrinoda is a small-bodied species and Graptemys pulchra is a large-bodied species. In the study populations, adult female G. pulchra were on average 23% larger in plastron length and 125% larger in body mass and there was no overlap in size. Both species had positive but hypoallometric relationships of both clutch size and egg size with body size, a pattern reported for 3 congeners previously, thus further demonstrating the competing sinks of increases in both variables and refuting the optimal egg size hypothesis. For interspecific comparisons using analysis of covariance, there was no significant effect of species on clutch size after accounting for the effect of plastron length. The effect of species on egg width and width of the pelvic aperture was significant, with G. pulchra having relatively wider eggs and pelvic apertures, perhaps related to the more domed carapace and larger body sizes of their hatchlings. Compared with 3 congeners, the 2 Alabama River species had relatively small clutches of relatively large eggs. Latitudinal effects on reproductive output may be important in Graptemys, with more-northerly populations tending toward larger clutches of smaller eggs. There is a need to analyze more data from more populations with log-log analyses of reproductive allometry to confirm the trend. There is also a need to consider shape allometry in future analyses; in particular, the hypoallometry of both shell height and shell width relative to shell length.

Allometric models for sex ratio determination in all stages of ontogeny of Chelonia mydas from Bahía de los Ángeles, México

AbstractIn order to determine the sex of Chelonia mydas individuals found within one of the principal foraging areas of the Gulf of California during any given stage of ontogeny, 529 individuals were sampled in Bahía de los Ángeles from 1995–2012, and their morphometric data were collected. A principal component analysis (PCA) was performed for the morphometric variables, and two principal components were obtained that unambiguously separated sexes and ontogenetic stages. The first component was defined by straight carapace length (SCL), curve carapace length (CCL), plastron length (PL) and carapace depth (CD), while the second factor was represented by total tail length (TTL). Allometric models were fitted with the most important variables determined by the PCA. The model PL = αSCLβ was able to distinguish between adults and immature individuals. For adult organisms, the model that best separated males from females was TTL = αSCLβ. Adult females had SCL values of 66–96.7 cm and TTL values of 16.3–25 cm, while adult males had SCL values of 66.4–12.5 cm and TTL values > 25 cm. As the organisms were considered immature only if SCL < 77.3, we were able to determine the TTL values for immature individuals by using elemental mathematics and solving for SCL in the equation TTL = αSCLβ for each group (i.e. adult females, adult males and immatures). So, considering the mathematical approach and acknowledging the lack of background information, immature individuals may be considered potential females if the TTL value is between 7.04–17.8 cm and potential males if the TTL value > 17.8 cm.

Serum biochemistry of Trachemys scripta elegans and Trachemys dorbignyi (Testudines: Emydidae) bred in captivity in the Northeastern semiarid region of Brazil.

Aim:This study aimed to assess fundamental biochemical values of healthy animals and to provide useful data on comparative physiologies of Testudines, being assessed the serum biochemistry profiles, and body and tail biometry of Trachemys scripta elegans and Trachemys dorbignyi bred in interaction in the semiarid region of the São Francisco river valley.Materials and Methods:Serum biochemistry variables (urea, creatinine, glucose, total serum protein, albumin, globulin, and albumin/globulin ratio), and biometry values of the body (mass [body mass (BM)], maximum curvilinear length [carapace length (CL)], and width [carapace width (CW)] of the carapace, maximum curvilinear length [plastron length (PL)], and width [plastron width PW] of the plastron), and the tail (total length of the tail [TLT], pre-cloacal tail length [PrCL], post-cloacal tail length [PoCL]) were measured after 24 h fasting.Results:T. s. elegans displayed higher BM, CL, CW, PL, PW, AST, TP, albumin, and globulin values. T. dorbignyi displayed higher values of glucose, TLT, and PrCL. Variables aspartate aminotransferase (AST) and total protein (TP) in T. s. elegans and glucose in T. dorbignyi explained most of the variance between the species and could serve to distinguish them.Conclusion:We conclude that most of the differences between T. s. elegans and T. dorbignyi shall be explained by biometric variables, AST, TP, and glucose, which characterize interspecific differences. Our results point out terms of reference for these species bred in captivity in the semiarid region of Brazilian Northeastern region and serve as a model for the comparative intra- and inter-species physiology and as a base for the health assessment of these species.

Comparisons of Population Structure and Morphology of a Saltmarsh Keystone Species (Malaclemys terrapin) Across Coastal Louisiana

Diamondback terrapins (Malaclemys terrapin) are an ecologically important species in salt marsh habitats, and they occur along the Gulf of Mexico and the Atlantic coastlines of the USA. Terrapins are subjected to a myriad of threats including loss of coastal marsh/nesting habitat and differential adult mortality in fisheries bycatch. In Louisiana, knowledge of terrapin populations is lacking even though they likely face these same threats. To address this knowledge gap, we sampled terrapins across coastal Louisiana from 2011 to 2015 using unbaited fyke nets at six study sites. We sexed all individuals and measured morphometric characters (including plastron length, PL and carapace height, CH). We captured 1111 individuals at all sites, and each site was represented by ≥ 96 individuals. Skewed sex ratios were found at five of the six sites, while three of the six populations were lacking individuals in the 13–15 cm PL size classes. Male and female PL varied, with Chenier Plain males being larger than Deltaic Plain males, while Deltaic Plain females were larger than Chenier Plain females. Similarly, CH also varied, with Deltaic Plain males and females being relatively deeper than individuals from the Chenier Plain. A number of biotic, abiotic, and anthropogenic factors likely interplay to influence population structure, shell morphology, and demographics. However, the latter, including bycatch in crab traps, is possibly influencing terrapin population structure at some study sites via selective mortality of males and juvenile females. We suggest that future studies research the effects of anthropogenic factors on terrapin populations.

Reproductive ecology of the endangered Beal's-eyed turtle, Sacalia bealei.

The Beal’s-eyed turtle (Sacalia bealei) is endemic to southeastern China and endangered due to poaching and habitat loss. Knowledge of S. bealei ecology is lacking and this study provides baseline information of its reproduction in a natural environment. We studied the reproductive ecology of S. bealei using X-ray, spool-and-line tracking, and direct observation. Six nesting females were successfully tracked and their nesting behaviors are documented in detail. Females produced a mean clutch size of 2.2 eggs (range 1–3). The hard-shelled eggs were ellipsoidal with a mean length of 45.50 mm, a mean width of 23.20 mm, and mean weight of 14.8 g. The relative clutch mass was 9.47%, while the relative egg mass was 4.60%. The mean incubation period was 94.7 days with a mean nest temperature of 25.08 °C. Hatchlings had a mean weight of 9.7 g, carapace length of 40.1 mm, carapace width of 33.3 mm, carapace height of 17.4 mm, plastron length of 31.6 mm, and plastron width of 25.4 mm. The results of this study provide important information to inform conservation plans and ex-situ breeding for this endangered species.

Plastron Pigmentation Variation in a Coastal Turtle Species of Conservation Concern (Malaclemys terrapin)

Abstract Malaclemys terrapin inhabits salt marshes of the coastal United States and has been historically divided into seven subspecies. Two of the described subspecies, M. t. pileata and M. t. littoralis, occur along the western and eastern coastlines of Louisiana, respectively. To better understand potential boundaries of these two subspecies, we documented pigmentation variation of the plastron along the coast of Louisiana where the subspecies supposedly intergrade. Photographs of the plastron were taken of captured individuals and we quantified pigment with a photoprocessing software (ImageJ). We found pigmentation differences between sexes, with females having lighter plastrons than males. The plastron pigmentation of females decreased with increasing plastron length, whereas that of males varied by site but not length. Plastron pigmentation did not correlate with longitude in either sex, indicating that there is no geographical cline in this trait. We suggest that large females might be released fro...

Sexual Dimorphism in Red-Eared Sliders (Trachemys scripta elegans) from the Wild Animal Triage Center of the Tiete Ecological Park, São Paulo, Brazil

Background: Trachemys scripta elegans is an aquatic turtle native to North America and distributed geographically from the eastern United States to northeastern Mexico. In Brazil, it is an exotic and invasive species and the most illegally traded pet animal. When these turtles grow and they cease to be attractive as pets, they are released clandestinely in lakes, ponds, rivers, and other bodies of water, where they threaten biodiversity and native populations. The present study aimed to characterize specimens of T. s. elegans from the Centro de Triagem de Animais Silvestres do Parque Ecológico do Tiete by analyzing body biometrics, sexual dimorphism, and structure of specimens for sex ratio and size classes.Materials, Methods & Results: Trachemys scripta elegans turtles (39 females and 30 males) were anesthetized, euthanized and frozen. After being thawed, the turtles were sexed according to measurements on secondary sex characters such as claw length (CWL) of the third finger of the right forearm and length of the tail from the tip to the beginning of the cloacal opening (postcloacal tail length, PTL); subsequently, sex was confirmed through dissection. Subsequently, body mass (BM, g) and maximum carapace length (MCL, cm), maximum carapace width (MCW, cm), maximum plastron length (MPL, cm), maximum plastron width (MPW) and shell height (HGT, cm, measured laterally until obtaining the greatest value) were evaluated and the sexual dimorphism index (SDI) was also calculated. All analyses were performed using SAS v. 9.4 software. The results indicate a sex ratio of 1.3 females per male. The identification of males by secondary sex characteristics was performed using only claw length (CWL), which was related to sex and not to maximum carapace length (MCL). The most discriminatory variables were CWL in males and body mass (BM) in females. With the exception of CWL, the sexual dimorphism index (SDI) values all favored females and varied from 1.21 to 2.49, with the greatest value for BM and the lowest value for postcloacal tail length (PTL). Males exhibited a unimodal tendency at a classification interval of 15.0 cm MCL, and females exhibited a bimodal tendency at 21.0- and 22.0 cm MCL. Sexual maturity was identified at 12.0 cm MCL in males and at 12.5 cm MCL in females. The rate of CWL growth in males was higher at the beginning of sexual maturity and subsequently decreased, whereas in females, the rate of CWL escalated after 19.0 cm MCL. In both sexes, principal component 1 (PC1) was composed of the variables related to size and BM, and principal component 2 (PC2) and principal component 3 (PC3) were composed of variables related to secondary sex characteristics (CWL and PTL).Discussion: In members of the genus Trachemys, several secondary sex characteristics can be used to differentiate between the sexes, however, in the present study, recognition of males was performed only by claw length, as it was confirmed by the discriminate analysis and the principal components analysis (PCA) which showed that CWL was the variable that was most discriminatory in males (approximately 76.0%), followed by BM (approximately 50%) in females. The results reinforcing the claim that the degree of development of secondary sex characteristics varies between species as well as between distinct populations of the same species and establish that even under unnatural habitat, sexual dimorphism of size in favor of females is maintained for variables related to mass and size.

Immunocompetence in a long‐lived ectothermic vertebrate is temperature dependent but shows no decline in older adults

Summary Temperature affects nearly all aspects of the physiology of ectotherms, including their ability to mount an immune response. Typically, the ectothermic vertebrate immune system can respond over a wide range of temperatures, but there is a species‐specific temperature at which responses are strongest, with impaired responses above and below this threshold. In long‐lived ectotherms, ageing could also influence the ability to respond to temperature changes as immunosenecence, the functional decrease in immune function with age, is widely reported. This study examined the effects of the interaction between temperature and age on B‐cell function in a long‐lived reptile, the red‐eared slider turtle, Trachemys scripta. B cells in this species have previously been shown to have two main functions, phagocytosis and antibody production. Adult turtles were trapped and blood samples taken. Because sliders grow throughout their lifetime, plastron length was used as a proxy for age. Leucocytes were isolated and used in either an ELISpot assay to examine their ability to produce antibodies spontaneously or when stimulated, or used in a phagocytic assay. The ELISpot and phagocytic assays were conducted over a range of biologically relevant temperatures. We found no interaction between age and temperature on any measure of B‐cell function. In all cases there was a significant effect of temperature, with impaired function at temperatures below 29 °C, but no impairment of function at higher temperatures. We also found little evidence of immunosenescence in any response. This study provides insight into the thermal biology of B‐cell function in sliders and provides an interesting connection between immunology, behaviour and ecology in this long‐lived turtle. A lay summary is available for this article.