César Jaeger Drehmer

Anomalies and variation in the dental formula of bats of the genus Artibeus Leach (Chiroptera, Phyllostomidae)

This paper describes and analyzes the causes of dental formula anomalies in the bats Artibeus lituratus (Olfers, 1818) and Artibeus fimbriatus Gray, 1838 (Phyllostomidae) belonging to populations inhabiting the southernmost Brazilian state of Rio Grande do Sul. Based on material examined and descriptions reported in the literature, is presented a general discussion on variation in the presence or absence of the third superior and inferior molars within members of the genus Artibeus (Leach, 1821). Of the 104 A. lituratus skulls examined was found one with an extra upper incisor and one with an extra upper right third molar, along with one case of lower third molar agenesis. In the 44 A. fimbriatus skulls examined was found one with an extra upper right second premolar, a tooth which is usually absent in this species. The occurrence of the extra molar in A. lituratus and the second premolar in A. fimbriatus are atavistic, probably reflecting the ancestral A. lituratus in the case of the extra molar and, for the premolar, an even more ancient ancestor which lived before the divergence of the Phyllostomidae family. Regarding the genus as a whole, there is variation in the presence or absence of the third superior molar in practically all Artibeus species, such variation occurring at both the intrapopulational level and geographically. There is also already a low frequency of absent third inferior molars in various Artibeus species. Both superior and inferior third molars are in the process of exclusion from the dentition of Artibeus and do not occur in some species, and, when present, are always reduced in size and extremely simplified in their cuspidal pattern and do not participate in food processing: indicating a clear evolutionary trend to the loss of these teeth. Such variation is important because variability in the presence and absence of third molars means that these teeth are not appropriate characteristic for the identification of Artibeus species.

Numerical anomalies in the dentition of southern fur seals and sea lions (Pinnipedia: Otariidae)

Cases of dental agenesis, supernumerary teeth and dental losses are presented in three species of South American Otariids: Arctocephalus australis (Zimmermann, 1783), A. tropicalis (Gray, 1872) and Otaria flavescens (Shaw, 1800). For the first time, congenital and acquired dental anomalies were comparatively diagnosed in skull samples from southern Brazil and nearby areas. The skulls and mandibles were accessed in the scientific collection of mammals of the Federal University of Santa Catarina, southern Brazil. Agenesis was found only among maxillary post-canine teeth, especially the distal ones (PC/6), due to an evolutionary trend towards reduction of the number of post-canine teeth in this family. Maxillary and mandibular supernumerary teeth were found in A. australis and A. tropicalis, but their positioning is unrelated to cases regarding phylogenetic and evolutionary implications. Dental losses were found in all species and different stages of alveolar obliteration suggest that this process is common in Otariids and does not affect their survival. The investigation of congenital and acquired dental anomalies in pinnipeds can provide information on dental formula evolution in Pinnipeds and in the phylogenetic relationships among Carnivora.

Stridulatory file and calling song of two populations of the tropical bush cricket Eneoptera surinamensis (Orthoptera, Gryllidae, Eneopterinae)

This study characterizes the calling song and ultramorphology of the stridulatory file of two geographically isolated populations of the tropical bush cricket Eneoptera surinamensis (De Geer, 1773) from city of Foz do Iguacu, state of Parana, and town of Rio Claro, state of Sao Paulo, Brazil, distant 1,000 Km from each other. The teeth are shell-shaped, the larger ones are distributed in the medium region of the file, decreasing gradually in size towards the edges. Specimens from Foz do Iguacu have a file with 82 ± 9.8 teeth, length=1.89 mm ± 0.15 with 43.76 ± 5.94 teeth per mm (n=15). Specimens from Rio Claro present a file with 87 ± 9.81, length=1.96 ± 0.19 mm with 44.52 ± 4.61 teeth per mm (n=15). Statistical differences found between the two populations are not significant. The calling song is an uninterrupted trill that alternates two sets of notes distinct for its temporal features.

Uma revisao dos atavismos em vertebrados

Este trabalho apresenta uma sintese sobre o estudo dos atavismos, destacando os tres tipos – espontâneo, experimental e taxico – e os criterios basicos para reconhecimento dos mesmos. Sao apresentados varios casos de atavismos em distintos grupos de vertebrados: casos de atavismos experimentais de formacao de digitos-extra em roedores caviomorfos e de fibulas completas em aves, e de formacao de dentes a partir do epitelio de aves em combinacao com mesenquima de roedores; varios exemplos de atavismos espontâneos como o aparecimento de membros locomotores posteriores em cetaceos e serpentes, o reaparecimento de digitos-extra em cavalos, a ocorrencia de molares mandibulares em felideos, e de musculos da cintura pelvica de passeriformes; atavismos taxicos sao discutidos a luz de filogenias robustas para os grupos (peixes ciclideos, passeriformes, pinipedios focideos, serpentes fosseis, crocodilianos gavialineos) e considerados como consequencia natural da incorporacao definitiva dos atavismos espontâneos aos distintos taxons. A irreversibilidade da evolucao, ou lei de Dollo, surge como uma discussao teorica importante e subjacente, permitindo uma visao critica sobre o papel dos atavismos na evolucao dos vertebrados. A importância dos mecanismos de regulacao genica, como dos genes Hox, o uso dos atavismos na busca de criterios de estabelecimento de homologias, e a possivel relacao dos atavismos com fenomenos macroevolutivos tambem sao apresentados, assim como todo o criticismo e analisado e discutido. Palavras-chave: vertebrados, atavismos experimentais, atavismos espontâneos, atavismos taxicos, irreversibilidade da evolucao.

Variations in dental formula of Otaria byronia Blainville (Pinnipedia, Otariidae) from Pacific: A new kind of anomaly

Fourteen South American sea lion specimens from the Pacific population (Chile and Peru) containing dental anomalies are presented from a total sample of 296 specimens. Postcanine agenesis, especially in the upper PC6, is the most frequent anomaly related to the natural instability of this tooth in this species. Although its occurrence is treated as a taxic atavism, we speculate that its presence in other otariid species may be regarded as a vestigial or rudimentary structure. Lower post-canine extra teeth at the PC6 position, corroborates the spontaneous atavism hypothesis back in time to the beginning of the Pinnipedimorpha evolution at Oligo/Miocene. The first case of multiple agenesis for Otaria byronia is here presented. The upper PC2 and PC3 and the lower PC4 are absent on both sides characterizing an oligodonty, a dental anomaly common in other mammal species, such as dogs and humans. The study of dental anomalies can furnish important amounts of information concerning dental evolution of Pinnipedia and contribute to the elucidation of their phylogenetic relationships among the Carnivora Arctoidea. Key words: agenesis, atavisms, supernumeraries, oligodonty.