Behavioural plasticity in activity and sexual interactions in a social lizard at high environmental temperatures

Sexual selection often shapes social behavioural activities, such as movement in the environment to find possible partners, performance of displays to signal dominance and courtship behaviours. Such activities may be negatively influenced by increasing temperatures, especially in ectotherms, because individuals either have to withstand the unfavourable condition or are forced to allocate more time to thermoregulation by increasing shelter seeking behaviour. Thus, they "miss" opportunities for social and reproductive interactions. Moreover, behavioural displays of ectotherms closely depend on temperature; consequently, mate choice behaviours may be disrupted, ultimately modifying sexual selection patterns. Therefore, it would be interesting to elucidate how increasing temperatures associated with global warming may influence activity and social interactions in the species' natural habitat and, specifically how high temperatures may modify intersexual interactions. Consequently, our aim was to explore differences in the daily pattern of social interactions in an ectotherm model, Tropidurus spinulosus, in two thermally different habitats and to determine how high temperatures modify mate choice. High environmental temperatures were found to be associated with a bimodal pattern in daily activity, which was closely linked to the daily variations in the thermal quality of the habitat; whereas the pattern and frequency of social displays showed less plasticity. The time allocated to mate choice generally decreased with increasing temperature since individuals increased the use of thermal refuges; this result supports the hypothesis of "missed opportunities". Moreover, at high temperatures, both sexes showed changes in mate selection dynamics, with females possibly "rushing" mate choice and males showing an increase in intermale variability of reproductive displays. In our ectotherm model, plastic adjustments in the behavioural activity pattern induced by high temperatures, plus the modification of the displays during courtship may ultimately modify mate choice patterns and sexual selection dynamics.

Macro- and microscopic brain anatomy of the amazon lava lizard (Tropidurus torquatus) (WIED, 1820)

Abstract Reptiles have a key role in understanding amniotes’ reproductive independence of water. Many adaptations arose, including in locomotor patterns and behaviours, and the nervous system adapted to those new habits. We have described the macroscopic anatomy and cytoarchitecture of the Amazon Lava Lizard brain (Tropidurus torquatus), an abundant lizard in South America. Fifteen specimens were captured, euthanized and their brains were dissected, eight of these were processed and stained in haematoxylin-eosin. Their main areas of the brain are the telencephalon and diencephalon, in the forebrain, tectum and tegmentum, in the midbrain and medulla oblongata and cerebellum, in the hindbrain. The main and accessory olfactory bulbs are the most rostral structure of the brain and are composed of six layers. Brain hemispheres compose the telencephalon and are divided in pallium and subpallium. Medial, dorsomedial, lateral and dorsal cortices are part of the pallium. Striatum, pallidum and septum compose the subpallium. The diencephalon is composed of thalamus, epithalamus and hypothalamus. The midbrain has a ventral tegmentum, composed of torus semicircularis and a dorsal 14 layered optic tectum. Most part of the hindbrain is composed of the medulla oblongata, and the cerebellum arises from it, forming a three-layered plate like structure. In general, the brain of Tropidurus torquatus resembles those of other lizards, with its own adaptations.

Anatomia macro- e microscópica do encéfalo do calango (Tropidurus torquatus) (WIED, 1820)

Resumo Os répteis têm um papel fundamental para a compreensão da independência reprodutiva da água que surgiu nos amniotas. Várias adaptações ocorreram, inclusive em padrões e comportamentos locomotores, e o sistema nervoso se adaptou a esses novos hábitos. Descrevemos a anatomia macroscópica e a citoarquitetura do encéfalo do calango (Tropidurus torquatus), um lagarto abundante na América do Sul. Quinze espécimes foram capturados, eutanasiados e seus encéfalos dissecados, oito destes foram processados e corados em hematoxilina-eosina. As principais áreas do cérebro são o telencéfalo e o diencéfalo, na parte anterior do encéfalo, teto e tegmento, no mesencéfalo e bulbo e cerebelo, na parte posterior do encéfalo. Os bulbos olfatórios principais e acessórios são as estruturas mais rostrais do cérebro e são compostos por seis camadas. Os hemisférios cerebrais compõem o telencéfalo e são divididos em pálio e subpálio. Os córtices medial, dorsomedial, lateral e dorsal fazem parte do pálio. Estriado, pálido e septo compõem o subpálio. O diencéfalo é composto pelo tálamo, epitálamo e hipotálamo. O mesencéfalo possui um tegmento ventral, composto de torus semicircularis e um tecto óptico dorsal com 14 camadas. A maior parte da parte posterior do encéfalo é composta pelo bulbo, e o cerebelo surge como uma projeção dessa estrutura, em formato plano, com três camadas. Em geral, o encéfalo de Tropidurus torquatus se assemelha ao de outros lagartos, com suas próprias adaptações.

A guide to incubate eggs of Tropidurus lizards under laboratory conditions

Studies in Evo-Devo benefit from the use of a variety of organisms, as comparative approaches provide a better understanding of Biodiversity and Evolution. Standardized protocols to incubate eggs and manipulate embryo development enable postulation of additional species as suitable biological systems for research in the field. In the past decades, vertebrate lineages such as Squamata (lizards, snakes, and amphisbaenians) emerged as crucial study systems for addressing topics as diverse as phenotypic evolution and climate change. However, protocols for maintaining gravid females and incubating eggs in the lab under experimental conditions are available to only a few squamate species. This resource article presents a simple incubation guide that standardizes conditions to maintain embryos of Tropidurus catalanensis (Squamata: Tropiduridae) under different experimental conditions, manipulating relevant environmental factors like temperature and humidity. We identified associated effects relating the egg incubation condition to developmental stage, incubation time, hatching success, and resulting morphotypes. Temperature and humidity play a key role in development and require attention when establishing the experimental design. Current literature comprises information for Tropidurus lizards that ponders how general in Squamata are the ecomorphs originally described for Anolis. Studies evaluating phenotypic effects of developmental environments suggest plasticity in some of the traits that characterize the ecomorphological associations described for this family. We expect that this incubation guide encourages future studies using Tropidurus lizards to address Evo-Devo questions.

Phenotypic diversity and its relationship to reproductive potential in changing social contexts in a lizard model

Phenotype in lizards is related to reproductive function, and hence to reproductive output. Besides the intraspecific diversity in phenotypes, their temporal variation throughout the reproductive season in relation to the variation of social contexts builds extra complexity into sexual selection scenarios. One useful model for understanding phenotypic diversity dynamics is Tropidurus spinulosus because it presents sexual dimorphism in different phenotypic traits, dichromatism in regions related to reproductive behaviour, and it has intense social reproductive interactions. We aimed to evaluate how the reproductive and phenotypic traits of individuals vary with changing social contexts, and how intrasexual phenotypic diversity and reproductive potential are explained by the phenotypic traits. In this study, we used data obtained during four consecutive breeding seasons (2015–2018) in a wild population. The social context, characterized according to the operational sex ratio, varied between months and, therefore, some phenotypic and reproductive traits also varied. We found that body robustness and chromatic diversity were the main sources of phenotypic diversity and were related to reproductive traits in both sexes. Our results help to understand the dynamics and reproductive implications of phenotypic diversity in changing social contexts in a lizard social model.

Reproductive biology of a viviparous lizard (Mabuya dorsivittata) from the subtropical Wet Chaco of Argentina: geographical variations in response to local environmental pressures

Herein we studied the reproductive biology of a viviparous lizard (Mabuya dorsivittata) from the Wet Chaco region (northeastern Argentina) and compared the results with other populations from the Espinal (central Argentina) and the Atlantic Forest (southeastern Brazil), and with other Neotropical species of Mabuya to better understand the possible causes of its reproductive phenotype variation. Males and females of M. dorsivittata from the Wet Chaco exhibited associated, seasonal, and annual reproductive cycles. Spermatogenic activity related positively to a lengthening photoperiod reaching maximum activity in late spring (December). Females displayed an extended gestation period of 11 months, from mid-summer (February) to late spring or early summer (December) when births occur. Embryonic development was associated with temperature and historical rainfall. Litter size ranged from 3 to 8 (mean = 5.3 ± 1.3 SD) and increased with body size and body mass of females. Fat-body mass varied seasonally and was inversely correlated with spermatogenesis and to embryonic development. Females were larger in body size and interlimb length, and smaller in head length than males. We observed interpopulational differences in minimum body size, litter size, and timing of birth, probably as a result of phenotypic plasticity, genetic divergence or both.

Development and differentiation of the reproductive system of Tropidurus catalanensis (Squamata: Tropiduridae)

Development and differentiation of the reproductive system in lizards begin in the embryonic period, although the stage and time of their occurrence vary according to populations and species. In this study, the events of the development and differentiation of the reproductive system of males and females of Tropidurus catalanensis were characterized during the embryonic, neonatal, and juvenile periods. Embryos at Stages 27, 34, 37, 40, and 41, neonates and juveniles, from Corrientes, Argentina, were analyzed. At Stage 27, the genital ridge was not observed but primordial germ cells were recorded in the yolk sac as well as the mesenteric mesenchyme, indicating the beginning of germ cell migration. Gonadal differentiation commenced at Stage 34. In males from Stage 37, the testes possessed seminiferous cords with Sertoli cells and spermatogonia, while in hatchlings seminiferous tubules and interstitial tissue with mature Leydig cells were present. Spermatogenesis was observed in a specimen of 51.9 mm snout-vent length, corresponding to the minimum reproductive size. In females, from Stage 37 until hatching, the ovaries had a cavernous medulla and a cortex with somatic cells and abundant oogonia. The onset of meiosis and folliculogenesis occurred in the juvenile period.

How does a viviparous semifossorial lizard reproduce? Ophiodes intermedius (Squamata: Anguidae) from subtropical climate in the Wet Chaco region of Argentina

The best predictors of reproductive patterns are commonly associated with climate factors, but evolutionary history also plays an important role. The semifossorial and viviparous lizard Ophiodes intermedius from the Wet Chaco region of Argentina showed an annual cycle with asynchrony between males and females and an unusual pattern for subtropical climates, with vitellogenesis beginning in autumn, ovulation and copulation in spring, and births occurring in summer. Males exhibited annual variation of testicular size associated with spermatogenic activity, reaching their maximum gonadal activity in late summer (March), but sperm storage in the epididymis and/or deferent duct occurred throughout the year. Females showed an extended reproductive cycle beginning in mid-autumn (May) with vitellogenesis and finishing with births from late spring to mid-summer (December to February). Litter size varied from 4 to 9 offspring. Females reached sexual maturity at a larger snout-vent length and, overall, showed greater body size than males, while males exhibited larger heads than females. Fat body cycles indicated that females use lipid reserves to support vitellogenesis and embryo development, while males allocate lipid resources to the search for females, courtship and copulation rather than to gametogenesis. Ophiodes intermedius differed from other species of the genus in litter size, gestation period, timing of birth and the minimum size at sexual maturity, probably as a result of the influence of ecological, historical and phylogenetic factors.