No abstract

Most lizards feed on a variety of food items that may differ dramatically in their physical and behavioral characteristics. Several lizard families are known to feed upon hard-shelled prey (durophagy). Yet, specializations toward true molluscivory have been documented for only a few species. As snails are hard and brittle food items, it has been suggested that a specialized cranial morphology, high bite forces, and an adapted feeding strategy are important for such lizards. Here we compare head and skull morphology, bite forces, and feeding kinematics of a snail-crushing teiid lizard (Dracaena guianensis) with those in a closely related omnivorous species (Tupinambis merianae). Our data show that juvenile D. guianensis differ from T. merianae in having bigger heads and greater bite forces. Adults, however, do not differ in bite force. A comparison of feeding kinematics in adult Dracaena and Tupinambis revealed that Dracaena typically use more transport cycles, yet are more agile in manipulating snails. During transport, the tongue plays an important role in manipulating and expelling shell fragments before swallowing. Although Dracaena is slow, these animals are very effective in crushing and processing hard-shelled prey.

Sexual dimorphism may be indicative of differential natural and/or sexual selection pressures acting on males and females. Although similar degrees of adult sexual dimorphism may be observed among populations and species, underlying physiological, developmental and ecological processes driving growth during the juvenile stages may vary. Unraveling how and when differences arise during ontogeny is important to our understanding of the evolutionary patterns observed among adults. In addition, growth patterns may differ among traits within a single individual. Anolis lizards vary greatly in the degree of adult sexual size and shape dimorphism. Ultimate hypotheses (e.g. sexual selection, habitat partitioning) have been put forward to explain this variation, but proximate mechanisms operating during the juvenile stages remain largely unknown. Herein, we aim at elucidating the proximate mechanisms of sexual dimorphism in head and limb shape, performance and dewlap size in Anolis baracoae, a crown-giant anole. We used a longitudinal approach and raised 23 captive-bred juvenile A. baracoae lizards through adulthood. By quantifying body size, head and limb dimensions, dewlap size and bite performance, we obtained growth trajectories that were compared between the sexes and among traits. Our results show that the growth of head and limb shape is similar in males and females, whereas dewlap size and bite performance diverge at a specific age. Based on these results, we hypothesize that, whereas selection favors a similar head and limb shape in males and females, selection pressures on dewlap size and bite performance likely differ between the sexes. In addition, dewlap size starts diverging around the time the animals reach sexual maturity, whereas bite performance diverges much earlier in (sexually) immature males.

Crown-giant anole ecomorphs have evolved independently across the Greater Antilles (Cuba, Hispaniola, Jamaica, and Puerto Rico), but only a few of these species have well documented life histories. Herein we report previously undocumented observations of copulation, oviposition, and hatchlings for the Green-blotched Giant Anole (Anolis smallwoodi) of southeastern Cuba. We observed eight mating events (three with A. s. smallwoodi and five with A. s. palardis) along the coastline between Santiago de Cuba and Guantánamo Province during June 2010 and September 2011. One female A. s. palardis mated with two males in the same territory. Females dig a hole with their snouts, oviposit single eggs, and cover them with substrate. We monitored eight eggs incubated in slightly moist vermiculite. The minimum incubation times were 54-69 days (varying with temperature). Juveniles usually are colored like adults, bright green with white spots on the body, pale postlabial bands, and suprascapular stripes.