We analyzed growth in a population of Siren intermedia nettingi, Western Lesser Siren, from northwestern Louisiana using a mark–recapture technique employing PIT tags from January 1992 through March 1998. Traps were monitored for eight consecutive trap nights for all four seasons from 1992 to 1996, January and December winter trapping sessions in 1997, and late February through early March in 1998. A total of 1,004 siren captures included 575 original captures and 429 recaptures. A total of 223 sirens were recaptured at least once for a recapture rate of 38.7%. Thirty-five of the original sirens captured were recaptured in the same season and year and were not used in the analyses. Therefore, we had a usable recapture rate of 32.7%. Based on captures, bites by conspecifics, and presence of juveniles in the study pond, we concluded that sirens in this population were most active in autumn and winter and presumably had a winter breeding season. Males grew faster and reached larger sizes than females due to the large energy investment of females that produced ova and the importance of male agonistic behavior toward other male and female conspecifics. The greatest growth occurred in the spring, despite increased activity in autumn and winter. Sirens were least active in the summer. Growth was inversely proportional to size and smaller sirens grew at a faster rate than larger ones.

Chalcides ocellatus (Ocellated Skink) and Sphenops sepsoides (Wedge-snouted Skink) give birth and co-occur in many areas of Egypt. This study examined the intra- and interspecific morphological variables and seasonal changes in the masses of oviducts and fat bodies and reproductive traits of females of both species to evaluate the extent of their relationship. Both species were highly divergent morphologically. Females and males of Ocellated Skinks showed larger morphological variables for all measured characteristics than the corresponding sexes of Wedge-snouted Skinks. They were sexually dimorphic, with females having larger body and abdomen sizes than males. Relative head size (length and width) was significantly larger in males than females of Ocellated Skinks, unlike Wedge-snouted Skinks where females possessed wider heads. Males mature at a larger size in Ocellated Skinks than in females, but females and males of Wedge-snouted Skinks mature at comparable sizes. Based on the simultaneous occurrence of yolked ovarian follicles and ova or embryos in the oviduct, some females in both species produced two clutches per reproductive season. In Ocellated Skinks, the average number and relative mass of late-stage embryos were 4.18 (range 2–7) and 0.25 (range 0.09–0.63), respectively, and were positively and significantly associated with female body size; in Wedge-snouted Skinks, the average number and relative mass of late-stage embryos were 2.75 (range 2–6) and 0.24 (range 0.07–0.43), respectively, and were not correlated with female body size. Postbreeding, females of both species stored fat in their fat bodies. Females had a marked seasonality in reproduction (spring–summer), which was correlated with ambient temperature and day length. This seasonality simultaneously negatively impacted the fat body and positively impacted the oviduct referring to the utilization of storage material during embryonic development.

Energetic constraints caused by reproductive investment may incur immunological and oxidative costs to a female and potentially to her developing offspring. Oviparous reptiles are capable of altering offspring phenotype through differential allocation of physiological factors during vitellogenesis (yolk formation), depending upon the external environment and the physiological state of the female. Despite its importance in protecting developing offspring against infection, maternal transfer of immune factors has rarely been studied in reptiles. Furthermore, the extent to which offspring may be impacted by the inherent oxidative costs of vitellogenesis is not well understood. Using the Side-blotched Lizard (Uta stansburiana) as a model, we examined how reproductive investment (clutch size and mass) influenced maternal immunological (BKA) and oxidative state (ROMs) and whether these metrics covaried with egg yolk immunity and oxidative state. We assessed factors influencing variation in egg yolk BKA and ROMs within and across clutches from all females and found that females with smaller clutches had higher BKA and ROMs than females with larger clutches. There was also an overall positive relationship between maternal BKA and ROMs and clutch mass, regardless of clutch size. We did not find maternal and egg yolk BKA and ROMs to be directly related, but yolk ROMs decreased as egg mass increased. Within-clutch variation in yolk BKA and ROMs was not related to maternal investment, but variation among clutches was explained by maternal identity. Because egg yolk physiology can impose long-lasting or permanent changes to offspring, these results create a foundation for future work investigating factors contributing to yolk physiology and highlight the necessity of considering multiple physiological and ecological variables when conducting eco-immunological research.

Glaridoglanis ramosa, new species, is described from a cryptorheic basin in northern Shan State, Myanmar. The new species can be distinguished from G. andersonii, the sole congener, in having fewer vertebrae (39–40 vs. 42–44), more branched pectoral-fin rays (13–14 vs. 8–10), a longer maxillary barbel (reaching beyond proximal half vs. not more than proximal third of first pectoral-fin element; 87–101% head length vs. 75–79), a shorter pelvic fin (10.8–16.3% standard length vs. 18.0–22.4) and dorsal-to-adipose distance (7.1–11.7% standard length vs. 17.5–20.0), absence (vs. presence) of a thin, pale midlateral stripe, and an adipose fin that is strongly incised (vs. without incision or with a weak incision) at the posterior extremity of its base. We also investigated the taxonomic status of Glyptosternon malaisei, and conclude that it is a junior subjective synonym of Glaridoglanis andersonii.

Gradients in environmental conditions across a species' geographic distribution can drive variability in a variety of life history traits. In North American freshwater turtles, both body and clutch size have commonly been shown to vary latitudinally, and these two traits are often directly related, with larger individuals producing larger clutches. We studied the reproductive ecology in two Georgia populations of Spotted Turtles (Clemmys guttata) from 2016–2020 by attaching radio transmitters to female turtles during the breeding season. We x-rayed turtles to determine clutch sizes and used thread bobbins to locate nesting locations, allowing us to determine nest fates. Across all Spotted Turtle clutches (n = 41), mean clutch size was 2.1 (range: 1–4) eggs per clutch. Approximately 92% of individuals that we monitored produced at least one clutch during the breeding season, and we identified 16 instances of individuals producing more than one clutch in a single year, including six turtles triple clutching during 2018. We located 24 Spotted Turtle nests during the study, nine (37.5%) of which either hatched or partially hatched. The other nests were either depredated (41.7%), did not hatch due to infertility or environmental reasons (8.3%), or had an undetermined fate (12.5%). Our results indicate that annual reproductive output in southern Spotted Turtle populations can exceed that of northern populations where individuals produce a single larger clutch per reproductive season. Finally, opportunistic observations in Florida from 2014–2021 indicated that the reproductive season can begin over a month earlier than in southern Georgia, highlighting the variability in reproductive ecology even across a relatively short latitudinal distance.

Speciation through niche divergence often occurs as lineages of organisms colonize and adapt to new environments with novel ecological opportunities that facilitate the evolution of ecologically different phenotypes. In snakes, adaptive diversification may be driven by the evolution of traits relating to changes in their diets. Accordingly, habitat-mediated differences in prey available to ancestral snakes as they colonized and occupied novel dynamic landscapes are likely to have been a strong selective agent behind the divergence and radiation of snakes across the globe. Using an ancestral reconstruction approach that considers the multivariate nature of ecological phenotypes while accounting for sampling variation between taxa, we explored how diet and macro-habitat use coevolved across a phylogeny of 67 species of Afro-Asian colubrine snakes. Our results show that the most recent common ancestor of this clade was likely a dietary generalist that occupied tropical forests in Asia. Deviations from this generalist diet to a variety of specialist diets each dominated by the utilization of single prey types repeatedly occurred as ancestral colubrines shifted from tropical forests to savanna and grassland habitats across Africa. We additionally found that dietary specialist species were on average smaller in maximum length than dietary generalists, congruent with established predator-size, prey-diversity dynamics in snakes. We speculate that adaptive divergence in ancestral colubrines arose as a result of a selective regime that favored diets comprised of terrestrial prey, and that partitioning of different prey types led to the various forms of dietary specialization evident in these lineages today. Our findings provide new insights into the ecological correlates associated with the evolution of diet in snakes, thereby furthering our understanding of the driving forces behind patterns of snake diversification.

Compensatory growth, where an organism can grow faster during recovery from low resource periods, is a mechanism used by a wide variety of taxa to mitigate previous deficiencies. Here we present experimental data to test whether pond-breeding salamander juveniles raised in different quality larval habitats can catch up to larger cohort members after metamorphosis. We reared larval Spotted Salamanders (Ambystoma maculatum) in ponds of differing habitat quality resulting in large size differences at metamorphosis. We then kept juveniles in the lab for a year, fed them ad libitum, and measured their growth at three time points post-metamorphosis. We found large differences in size at metamorphosis related to larval habitat, but salamanders that were small at metamorphosis remained smaller a year later and relative growth rates were equal across all metamorphic sizes. Thus, we have little evidence that juveniles can compensate for small size by growing more in the year after metamorphosis, even in conditions of unlimited food. Our data suggest compensatory growth in amphibians may be species-specific, and that poor quality larval environments may be a disadvantage during subsequent life stages.

Hemipenial characteristics have historically provided a wealth of comparative morphological characters for the systematic classification of snakes. However, the organs remain poorly known in many groups, particularly tropical and burrowing lineages. Here, we report on hemipenial morphology for 12 species from five genera from the family Uropeltidae: Melanophidium punctatum, M. cf. wynaudense, Plectrurus perrotetii, Rhinophis karinthandani, R. melanoleucus, R. saffragamus, R. sanguineus, Teretrurus cf. hewstoni, Uropeltis bhupathyi, U. cf. ceylanica, U. macrolepis, and U. rajendrani. Many are photographed or illustrated here for the first time. In Melanophidium, the organ is bulbous and mushroom-shaped, with the sulcus spermaticus winding through numerous convoluted folds. In Plectrurus and Teretrurus, it is simple, smooth, and conical. In Sri Lankan Rhinophis and some Uropeltis, the organ generally resembles previously described hemipenes from other species in those genera in being simple, subcylindrical, and covered in fine spines. However, a median lobular process is observed in the Indian species R. karinthandani, R. melanoleucus, and R. sanguineus, seemingly representing a novel bilobate morphology. One species, U. bhupathyi, exhibits a novel, bulbous morphology, but this may be an artifact of preservation. The hemipenes of the Uropeltidae and their sister group Cylindrophiidae resemble some typhlopoid blindsnakes more than their henophidian relatives such as pythons and boas. Whether this is due to convergence related to microhabitat, a form of sexual selection unrelated to ecomorphology, or symplesiomorphy from an ancestral snake morphology is unclear. Gross hemipenial morphology can now serve to diagnose uropeltids to the genus level or species group, though more data and comparative series are needed to determine whether other characters, such as the number and location of spines, can potentially differentiate taxa at finer scales.

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.

New genetic and morphological data support the recognition of a distinct monophyletic group, the Cyphocharax saladensis clade, which includes C. vanderi, C. saladensis, C. boiadeiro, and a new species. This four-species group can be recognized by modifications in the laterosensory system with instances of incomplete or interrupted poring, by the ontogenetic development of the lateral line with larger specimens having a more developed laterosensory system, and by the presence of a patch of dark pigmentation over the caudal peduncle. The new species is described from the upper Rio Correntes, an upland tributary of the upper Rio Paraguai in central Brazil and is diagnosed by the presence of a thin longitudinal black stripe, by the variable shapes of the dark blotches on the caudal peduncle, and by morphometric and meristic data. New mitochondrial data from paratypes provide clear evidence of genetic distinction between the new species and congeners, and additionally place it as the sister species to C. boiadeiro from the upper Rio Araguaia. Based on the updated molecular phylogeny and biogeographic information, we propose an evolutionary hypothesis with four events of river captures with subsequent allopatric speciation of the new species and C. boiadeiro in the Correntes and Araguaia systems. The new species is suggested to be categorized as Near Threatened, living in a strongly impacted region of the Brazilian Cerrado.

Male–male aggressive encounters in lizards may involve physical confrontation or the use of multiple cues to signal fighting ability. Behavioral, chromatic, and morphological traits may be associated to reinforce gradual messages to escalate or deescalate interactions during encounters. Our first aim was to provide a detailed ethogram of male–male aggressive encounters in the social lizard Tropidurus spinulosus. Then, we aimed to elucidate the association among behaviors and morphological and chromatic characters. Our results showed several behavioral displays organized in sequential phases, with two displays being characteristic of this species; furthermore, increasingly threatening displays may be repeated several times before reaching physical aggression. Males that dominated the encounters usually had more extended color bands in the most visible body parts, lower body condition, and preferentially had performed pushup early in the bout, whereas males that were ultimately chased had high color band extension in the chest and high testicular volume and performed more lateral compression and head-swipe escalating readily to physical aggression by biting the opponent. In conclusion, the behavioral displays employed by different males were associated with their morphological and chromatic characters, highlighting the existence of signaling strategies among individuals.

Joining the ranks of vertebrates that glow is the Pacific Spiny Lumpsucker, Eumicrotremus orbis, a subtidal species widely distributed across the North Pacific Ocean. Aside from their charismatic appearance, the Pacific Spiny Lumpsucker is known for its ventral suction disc that is used to stick to substrates amid changing currents and tides. Here we show that red lumpsuckers, which are usually male and a deep red color under broad-spectrum light, fluoresce bright red under ultraviolet (UV) light and blue light (360–460 nm), while green color morphs (usually female) do not. In all color morphs, the suctorial disc glows green-yellow. The red glow of the males matches the red glow of encrusting algae in their nesting areas, while the suctorial disc may be a signaling system. The green and red fluorescence observed in red lumpsuckers is the rarest fluorescent pattern and is only seen in 17 families of marine fishes. Pacific Spiny Lumpsuckers are cryptically colored under broad-spectrum light; our observed fluorescence suggests a potential avenue of communication and camouflage in an environment where red light is absent or rare.

A multitude of different statistical models are commonly used to monitor trends in wildlife populations. Most are used to estimate abundance or survival (or both), and these estimates are then examined over time to infer trends in a population. The choice of which model to use is influenced by the key research question of interest and the types of data available. The accuracy and precision of any estimate from a population model are determined by whether the data meet the model assumptions. We assessed the performance of both closed and open capture–recapture models for determining trends in abundance and survival of River Cooters, Pseudemys concinna, in the Santa Fe River, Florida from 2009–2019. We fit three closed models to estimate abundance, one open model to estimate survival, and two robust design models to estimate both abundance and survival. We then used simulation to generate three datasets that represented different sampling designs, including one that mimics our field data, to assess model performance and compare tradeoffs in sampling design. We recommend using the robust design framework when possible as this design and model estimation returned accurate and precise estimates of abundance and survival. This model estimated survival ranging from 0.69–0.95 and capture probability from 0.21–0.25. This design requires consistent sampling of at least three events per year during a closed period, repeated over at least five years, to estimate survival between years. In situations where samples could not be repeated across years, closed population models are likely the most reliable framework in terms of model precision and accuracy. Overall, sampling designs that allow for repeated sampling and align the biology of the study species and the assumptions of the statistical model are likely the most informative approaches for sampling River Cooters and similar species.

A new species of the rubbernose pleco genus Chaetostoma is described from the Maicuru and Seiko Rivers, a northern tributary of the lower Amazon River and a tributary of the lower Xingu River, respectively, both in Pará State, Brazil. The new species is diagnosed from all congeners, except members of the Chaetostoma anale species group, by having an enlarged second unbranched anal-fin ray with posterior paired dermal flaps. Additionally, the new species is distinguished from its only other currently recognized congeners from rivers draining the Guiana Shield (C. jegui and C. vasquezi) by having a smaller opercle and a supraoccipital excrescence undeveloped, comprising a simple skin area present in juveniles and absent in adults. A revised multi-locus phylogeny for the species of Chaetostoma is presented, and the Chaetostoma anale species group is discussed and rearranged.

Uma nova espécie de Chaetostoma é descrita dos rios Maicuru, um afluente norte do baixo rio Amazonas, e Seiko, um afluente do baixo rio Xingu, ambos no estado do Pará, Brasil. A nova espécie é diagnosticada de todos os seus congêneres, exceto membros do grupo Chaetostoma anale, por apresentar o segundo raio não ramificado da nadadeira anal aumentado e com abas dérmicas posteriores. Além disso, a nova espécie se distingue dos únicos outros congêneres atualmente reconhecidos do Escudo das Guianas (C. jegui e C. vasquezi) por ter o opérculo menor e a protuberância supraoccipital não desenvolvida, composta por uma área de pele simples em juvenis e ausente em adultos. Uma filogenia multilocus revisada para as espécies de Chaetostoma é apresentada e o grupo Chaetostoma anale é discutido e reorganizado.

Blanding's Turtles (International Union for Conservation of Nature [IUCN] Endangered) are long-lived reptiles with delayed sexual maturity. Anthropogenic landscape changes have increased threats to juvenile turtles, resulting in unnaturally low recruitment. Head-starting has become a popular conservation strategy that aims to increase juvenile recruitment by avoiding the increased predation of the vulnerable nest and hatchling age class. However, there is still debate about whether or not it is an effective management tool. Assessments of head-starting are becoming more prevalent, but long-term studies are needed to critically evaluate the success of such interventions. In particular, information is needed on how head-starts fare compared to wild-hatched turtles. The Lake County Forest Preserve District (LCFPD) in northeastern Illinois initiated a long-term capture–mark–recapture project in 2004. As of 2018, 127 wild-hatched juvenile turtles had been captured (59 of which had been captured in multiple years) and 148 adult turtles had been captured (116 of which had been recaptured in multiple years). Since 2010, LCFPD has released 491 headstarted turtles during the year following hatching, 138 of which have been recaptured during successive years. We used von Bertalanffy growth analysis to compare growth trajectories and Cormack-Jolly-Seber modeling techniques to compare survival rates of wild-hatched and head-started turtles. At release, head-started turtles were about the size of two-year-old wild-hatched turtles and grew in parallel to their wild-hatched counterparts. The top-ranked survival models demonstrated that survival increased with age for both wild-hatched (71–98%) and head-started turtles (63–90%), with overlapping confidence intervals. These results suggest that head-started juveniles perform similarly to like-aged wild-hatched juveniles despite head-starts having attained greater body size. We estimated adult survival to be 95% with an environmental variance of 0.0011 and stable or positive population growth (k). Although the success of head-starting cannot be fully assessed until turtles are recruited into the adult population and successfully reproduce, patterns of head-start growth and survival provide positive intermediate measures of success. Our estimation of juvenile and adult survival, along with other demographic information from this population, will provide for more accurate population projections that will aid in evaluating conservation strategies for this population and potentially for Blanding's Turtles elsewhere.

Demographic models are useful for analyzing the effect of selective pressures on populations. Polymorphic populations display dramatic variation in phenotype, and different morphotypes representing alternative strategies are characterized by specific sets of behavioral, physiological, and morphological traits. Coloration is a classic polymorphic trait, and variation in this trait has been linked to other traits, such as aggressiveness, size, and immune responses. Many studies of polymorphic populations have placed individuals into discrete categories, assuming that all individuals of each morphotype have the same performance; however, traits related to color can vary between individuals possessing the same coloration or classified as the same morphotype. Here, we determined the association of survival to a continuous or a discrete classification based on the percentage of colored area in the gular spots in four populations of the Mesquite Lizard Sceloporus grammicus and tested for patterns among populations. In two of our study sites (both located in the volcano “La Malinche”), there was no association of coloration on survival with either a discrete or continuous classification. At the other two study sites, there was a continuous association of color on survival, which suggests that previous studies of variation in polymorphic species might have often been conducted at an inappropriate “resolution” and that predictions in our analyses could be improved.

The Hellbender (Cryptobranchus alleganiensis) is a giant salamander inhabiting streams in the eastern United States that has experienced range-wide declines. It is estimated that Hellbenders have declined by 70% in some portions of their range, and many populations are composed solely of older adults, suggesting that a lack of successful breeding or low larval survival may be driving some declines. Although successful reproduction and larval survival influence the long-term stability of Hellbender populations, little is known about the ecological requirements of immature age classes. Understanding the requirements of immature Hellbenders is essential for accurately gauging population health and designing long-term conservation efforts. The objective of our study is to investigate associations between immature Hellbender habitat use and abiotic factors hypothesized to influence survival. We quantified habitat selection of immature Hellbenders within a use/availability framework in six streams in North Carolina known to contain all Hellbender age classes. Our results suggest that immature Hellbenders select home ranges based on a reduced water velocity and the presence of unembedded cobble beds and, within that home range, select unembedded mid-sized cover (18–28 cm) as microhabitat. We recommend targeting immature age classes during monitoring surveys to ensure a complete understanding of a population's status. This can be accomplished by conducting targeted surveys in areas of the stream with a slower current and beds of heterogeneous, unembedded cobble. We also recommend considering habitat preferences of immature age classes when selecting sites for Hellbender reintroductions and designing stream restoration initiatives to benefit Hellbender populations.