Teeth morphology and dental sexual dimorphism of three species of the sandskate genus Psammobatis Günther, 1870 from the Brazilian coast (Rajiformes, Arhynchobatidae)

Alvaro Brum-Neto,Carlos Alberto Santos De Lucena

doi:10.5007/2175-7925.2020.e70290

Alvaro Brum-Neto, Carlos Alberto Santos De Lucena

Open Access

https://doi.org/10.5007/2175-7925.2020.e70290

Copy DOI

Abstract

Conjuntos de mandíbulas das raias Psammobatis extenta (n = 10), P. lentiginosa (apenas indivíduos adultos, n = 8) e P. rutrum (apenas indivíduos adultos, n = 10) foram examinados utilizando microscopia eletrônica de varredura. Os dentes das fêmeas das três espécies e os dos imaturos de P. extenta não apresentaram diferenças, todos com dentes esmagadores monocuspidados, com uma cúspide pequena ou ausente. A heterodontia monognática foi observada em espécimes adultos de ambos os sexos das três espécies analisadas. Espécimes imaturos de P. extenta e fêmeas das três espécies diferiram dos machos adultos por ter dentes esmagadores ao invés dos dentes agarradores dos machos, indicando heterodontia sexual. Os dentes dos machos de P. extenta são pontiagudos e bem pronunciados, com as cúspides arredondadas, enquanto os machos de P. rutrum e P. lentiginosa possuem cúspides elípticas e similares entre si. Espécimes imaturos de P. extenta possuem cúspides pequenas. Os dentes de P. lentiginosa apresentam um sulco longitudinal em sua face labial, um caráter aqui hipotetizado como uma condição derivada.

Highlights

Species of Psammobatis Günther, 1870 are endemic to the eastern South Pacific and western South Atlantic coasts of South America, occurring from Rio de Janeiro, Brazil to Chile (EBERT; COMPAGNO, 2007)
Studies of species of Psammobatis are mostly limited to reproductive biology (e.g., BRACCINI; CHIARAMONTE, 2002; MARTINS; ODDONE, 2017), feeding habits (e.g., MUTO et al, 2001; MABRAGAÑA; COUSSEAU, 2004; BRACCINI; PEREZ, 2005) and geographical distribution (e.g., MENNI; STEHMANN, 2000; GOMES et al, 2010)
Females of the three species were differentiated from adult males by having a crushing type of dentition as opposed to a clutching type of dentition in males, indicating a gynandric heterodonty

Summary

Introduction

Species of Psammobatis Günther, 1870 are endemic to the eastern South Pacific and western South Atlantic coasts of South America, occurring from Rio de Janeiro, Brazil to Chile (EBERT; COMPAGNO, 2007). Studies of species of Psammobatis are mostly limited to reproductive biology (e.g., BRACCINI; CHIARAMONTE, 2002; MARTINS; ODDONE, 2017), feeding habits (e.g., MUTO et al, 2001; MABRAGAÑA; COUSSEAU, 2004; BRACCINI; PEREZ, 2005) and geographical distribution (e.g., MENNI; STEHMANN, 2000; GOMES et al, 2010). Concerning sexual dimorphism, the unpublished study of Paragó (2001) analyzed P. extenta and P. rutrum and sex-related shape of the anterior margin of the disc; Barbini and Lucifora (2012) recorded the gynandric heterodonty in Psammobatis bergi and P. extenta, and Braccini and Chiaramonte (2002) sexrelated differences in measurement variables and in tooth morphology in both sexes of P. extenta to the reproductive habit of the species. The same authors affirm that ontogenetic heterodonty is present only in males by a low tooth cusp, which grows to large size in maturing specimens

Methods

Results

Conclusion