Faculty Bibliography

Arginine vasotocin (AVT) is a neuropeptide that modulates social behavior in amphibians and activates calling in frogs. The Puerto Rican coqui frog, Eleutherodactylus coqui, is a terrestrial anuran that exhibits complex social behaviors, including territoriality and paternal care. Males have a distinctive social hierarchy and can be any of the following: satellite (non-calling), territorial (calling), or paternal (guards and broods embryos). Field experiments were conducted to determine the effects of AVT on satellite behavior and the male social hierarchy of E. coqui. Satellite males were captured within the territory held by a resident male, given injections (i.p.) of AVT or saline (control) and placed back in their original location. To determine if AVT affects all males, not merely satellite males, territorial (calling) males were injected with AVT. Significantly more satellite males commenced advertisement calling following AVT injections than did control males injected with saline. AVT-activated satellites did not challenge the resident territorial male for possession of the territory but instead moved into a new area before commencing to call. In fact, AVT-activated satellite males were significantly more likely to move into a new territory following AVT injections than AVT-injected territorial males. The effect of AVT was short lived, lasting only one night in all but two cases. It is concluded that AVT stimulates advertisement calling and AVT-activated males displayed territorial characteristics of E. coqui

Nearly all vertebrates possess an olfactory organ but the vomeronasal organ is a synapomorphy for tetrapods. Nevertheless, it has been lost in several groups of tetrapods, including aquatic and marine animals. The present study examines the development of the olfactory and vomeronasal organs in two terrestrial anurans that exhibit different developmental modes. This study compares the development of the olfactory and vomeronasal organs in metamorphic anurans that exhibit an aquatic larva (Bufo americanus) and directly developing anurans that have eliminated the tadpole (Eleutherodactylus coqui). The olfactory epithelium in larval B. americanus is divided into dorsal and ventral branches in the rostral and mid-nasal regions. The larval olfactory pattern in E. coqui has been eliminated. Ontogeny of the olfactory system in E. coqui embryos starts to vary substantially from the larval pattern around the time of operculum development, the temporal period when the larval stage is hypothesized to have been eliminated. The nasal anatomy of the two frogs does not appear morphologically similar until the late stages of embryogenesis in E. coqui and the terminal portion of metamorphosis in B. americanus. Both species and their respective developing offspring, aquatic tadpoles and terrestrial egg/embryos, possess a vomeronasal organ. The vomeronasal organ develops at mid-embryogenesis in E. coqui and during the middle of the larval period in B. americanus, which is relatively late for neobatrachians. Development of the vomeronasal organ in both frogs is linked to the developmental pattern of the olfactory system. This study supports the hypothesis that the most recent common ancestor of tetrapods possessed a vomeronasal organ and was aquatic, and that the vomeronasal organ was retained in the Amphibia, but lost in some other groups of tetrapods, including aquatic and marine animals

The avian hippocampal formation (HF) is a structure necessary for learning and remembering aspects of environmental space. Therefore, understanding the connections between different HF regions is important for determining how spatial learning processes are organized within the avian brain. The prevailing feed-forward, trisynaptic internal connectivity of the mammalian hippocampus and its importance for cognition have been well described, but the internal connectivity of the avian HF has only recently been investigated. To examine further the connectivity within the avian HF, small amounts of cholera toxin subunit B, primarily a retrograde tracer (n = 15), or biotinylated dextran amine, primarily an anterograde tracer (n = 10), were injected into localized regions of the HF. Examination of the immunohistochemically labeled tissue showed projections from extrinsic sensory processing areas into dorsolateral HF and the dorsal portion of the dorsomedial HF (DMd). DMd in turn projected into the medial (VM) and lateral (VL) ventral cell layers. A projection from VM into VL was found, and together these areas and DM provided input into the contralateral ventral cell layers. Ipsilaterally, a ventral portion of dorsomedial HF (DMv) received input from VL and VM. From DMv, projections exited HF laterally. The highlighted projections formed a discernible feed-forward processing network through the avian HF that resembled the trisynaptic circuit of the mammalian HF

Ordered hexagonal arrays of parallel collagen fibers produce the brilliant green structural color of the fleshy, supraorbital caruncles of male Velvet Asity (Philepitta castanea; Aves: Eurylaimidae). The collagen arrays are organized in larger macrofibrils that are packed irregularly within cone-shaped papillae that cover the surface of the caruncle. The color of the caruncle conforms closely to the wavelengths predicted by applying Bragg's Law of constructive reflection to measurements of the size and spatial organization of the collagen arrays. These observations constitute a novel mechanism of structural color production in animals. These collagen arrays are convergently similar to the smaller, highly structured collagen arrays in the mammalian cornea, which exploit the same physical mechanism to produce optical transparency. © 1994 Wiley-Liss, Inc.

A population of cells has been found in the chick optic tract and chiasm exhibiting GABA-like immunoreactivity (GABA+; Granda and Crossland, J. Comp. Neurol. 287:455-469, '89). It is not known, however, whether the cells are neurons. We have studied the GABA+ cells by using morphological and immunocytochemical methods. We found that there are more than 500 cells in each tract. At the light microscopic level, the cells possess processes resembling dendrites and axons. At the electron microscopic level, the organelle content of the cells is similar to that of neurons. The cells are immunoreactive with antibodies to MAP2 and neuron specific enolase, two proteins characteristic of neurons. Taken together the findings indicate that the GABA+ cells of the chick optic tract are neurons, perhaps similar to the interstitial neurons found in the white matter of other vertebrates