Arginine vasotocin (AVT) is a potent regulator of social behavior in many species, but little is known about its role in reptilian behavior. Here we examine the effect of exogenous AVT on aggressive responding and courtship behavior in the green anole lizard (Anolis carolinensis). Aggressive behavior was stimulated in two ways: (1) mirror presentation (no relative status formed) and (2) size-matched pairs (where a social status is achieved). To elicit courtship behavior, a novel female was introduced into the home cage of a male. Regardless of the behavior condition, male anoles were injected i.p. with either reptile Ringer solution (vehicle) or AVT prior to testing. Animals treated with AVT performed fewer aggressive display bouts during mirror presentation but AVT treatment did not affect the overall number of aggressive display bouts within size-matched pairs. Male courtship behavior was not affected by AVT; however, untreated females displayed more frequently when paired with an AVT-treated male than a vehicle-injected control, suggesting that AVT-treated males were more attractive to females. Regardless of behavior condition, AVT injections led to increases in circulating corticosterone. Overall, we found that AVT tended to reduce aggressive behavior as has been reported for other territorial species. AVT did not perceptibly alter male courtship but did increase the display behavior of untreated females paired with treated males. Our study supports a role for AVT in the regulation of reptile social behavior.

It has been suggested from studies in human subjects that sex, handedness, and brain asymmetries influence variation in corpus callosum (CC) size and these differences reflect the degree of connectivity between homotopic regions of the left and right cerebral hemispheres. Here we report that handedness is associated with variation in the size of the CC in chimpanzees. We further report that variation in brain asymmetries in a cortical region homologous to Broca's area is associated with the size of the CC but differs for right- and left-handed individuals. Collectively, the results suggest that individual differences in functional and neuroanatomical asymmetries are associated with CC variation not just in humans but also in chimpanzees and therefore may reflect a common neural basis for laterality in these 2 species.

Findings suggest that in humans, sex and hand preference may be associated with the size of the corpus callosum (CC). The authors measured CC morphology from MRIs in 67 chimpanzees (Pan troglodytes) to see whether similar effects were present in this species. Hand preference was assessed by performance on 4 tasks, and chimpanzees were classified as left-handed, right-handed, or ambidextrous. In a subsequent analysis, the chimpanzees were reclassified into 2 groups: righthanded and left-handed. The results revealed no sex difference in CC area, but significant effects of hand preference were found for several CC regions (rostrum body, anterior midbody, posterior midbody, isthmus, and splenium) and for overall CC size, with left-handed chimpanzees exhibiting significantly smaller CC measurements than right-handed chimpanzees. The results indicate that lateralized hand use in chimpanzees, as in humans, is associated with variation in CC size. Keywords Pan troglodytes; corpus callosum; handednessThe corpus callosum (CC) is the major set of fibers connecting homologous and heterologous cortical regions in the left and right cerebral hemispheres as well as some subcortical structures of the brain (Bermudez & Zatorre, 2001;Gazzaniga, 2000). Its presence allows for interhemispheric communication of sensory and motor functions within the brain. Previous research has shown that projections through the CC proceed on an anterior-to-posterior gradient that roughly connects cortical regions from the frontal to occipital lobe (Witelson, 1989). The morphology of the CC has been the topic of considerable debate, particularly as it relates to sex differences and lateralization (Byne, Bleier, & Houston, 1988;Denenberg, Kertesz, & Cowell, 1991;Driesen & Raz, 1995;Habib et al., 1991;Jancke & Steinmetz, 1998;Peters et al., 2002;Westerhausen et al., 2003).The presence of a sexual dimorphism in the human CC was first reported by de LacosteUtamsing and Holloway (1982). In their study, de Lacoste-Utamsing and Holloway found that women had a larger and more bulbous splenium (posterior fifth of the CC) than did men. Furthermore, de Lacoste-Utamsing and Holloway found that when brain weight was accounted for, women had a larger overall CC. Significant findings of a dimorphism favoring a larger total CC area or regional CC area in female humans have been reported in subsequent studies on cadaver specimens as well as from in vivo imaging studies (Achiron, Lipitz, & Achiron, 2001;Bermudez & Zatorre, 2001;Burke & Yeo, 1994 Innocenti, 1989;Witelson, 1989); however, several studies have found no evidence of sex differences in the size of the CC (Bishop & Wahlsten, 1997;Driesen & Raz, 1995;Habib et al., 1991;Horton, Crawford, Harrington, & Downs, 2004;Witelson, 1985).In addition to sex differences in CC morphology, the relationship between handedness and CC morphology has also been considered. In one of the earliest studies, Witelson (1985) found that mixed-handed individuals (those who did not consistently use their right hand for specifi...

Although behavioral and brain asymmetries have been documented in non-human primates, lateralization in cortical connectivity as reflected in white matter has not been described in any species, despite the intrinsic theoretical interest in white matter expansion during primate brain evolution. Here we report evidence of population-level leftward asymmetries in the white matter of chimpanzees. We further report that lateralization in white matter correlates with their handedness as well as neuroanatomical asymmetries in the precentral gyrus. These findings suggest that chimpanzees show asymmetries in cortical connectivity and these may serve as the foundation for morphological and behavioral laterality in primates, including humans.

Kisspeptins are a recently identified class of neuropeptides belonging to the RFamide peptide family. Despite growing evidence supporting kisspeptin as a key regulator of reproduction, data addressing whether kisspeptin is a conserved reproductive signal are lacking. We investigated the distribution of kisspeptin in adult green anole lizards (Anolis carolinensis) via immunohistochemistry. Additionally, we examined the possibility of a sexual dimorphism in kisspeptin expression. Kisspeptin immunoreactivity was observed rostrally in the preoptic area and caudally in an area lateral to the dorsal hypothalamic nucleus in both male and female anoles. These kisspeptin immunoreactive cells are associated with vesiculated fibers traveling through the paraventricular zone of the hypothalamus and preoptic area and extending into the rostral telencephalon. Preabsorption of the antiserum with gonadotropin inhibitory hormone (GnIH), a second RFamide peptide known to cross-react with the kisspeptin antiserum, eliminated staining of the caudal population of cells but retained staining in the rostral population, suggesting that kisspeptin is present in this area. Preabsorption with kisspeptin eliminated all immunoreactivity. These preabsorption results suggest that kisspeptin is restricted to a single population in the preoptic area in anoles. No sex differences were found in kisspeptin immunoreactive cell number. The presence of kisspeptin RFamide peptide in the green anole suggests that this reproductive regulatory signal is indeed evolutionarily conserved. Whether this reproductive signal functions similarly in regulating the reproductive axis of ectotherms requires further study.