Sperm ultrastructure of Bothrops alternatus and Bothrops diporus (Viperidae, Serpentes), and its possible relation to the reproductive features of the species

Abstract

Sperm ultrastructure has been described for several species of Serpentes and other Squamata in which it has been considered a valuable character source for phylogenetic studies. However, some ultrastructural traits have been also reported as adaptations to increase motility and/or longevity under sperm competition and storage conditions. Bothrops alternatus and Bothrops diporus are medium sized, viviparous, highly venomous species, and their reproductive cycles include periods of female sperm storage between mating and fertilization. In this work we provide, for the Wrst time, a detailed ultrastructural description of the spermatozoa of B. alternatus and B. diporus and discuss its possible relation to their reproductive features. Sperm was obtained from the vas deferens, and was processed to obtain transmission electron micrographs and Xuorescence micrographs. Spermatozoa of these species show similar morphological traits, which are closely related to the general model described for the Serpentes. Furthermore, several synapomorphies for the squamates can be identiWed in these cells. Nevertheless, the observed midpiece elongation and absence of dense bodies could augment the energy producing capabilities of the spermatozoa, thus enhancing the competitive aptitude of the ejaculate.

Ultrastructure of spermatid development within the testis of the Yellow-Bellied Sea Snake,Pelamis platurus(Squamata: Elapidae)

“…31 The principal piece is surrounded by the fibrous sheath similar to the midpiece in Agkistrodon; however, the peripheral fibers 3 and 8 in P. platurus flagella extend throughout the mid, principal, and endpieces and are more robust in size than that documented in other snakes to date, including Oxyuranus microlepidotus spermatozoa. 17 Much of the morphological data presented here for Pelamis platurus corroborates the microanatomy of the mature spermatozoa described for the elapid Oxyuranus microlepidotus and the pitvipers Crotalus durissus, 8 Bothrops, 21 and with that of the spermatid descriptions for Agkistrodon piscivorus and A. contortrix. 9 Presently, Cunha et al 8 and Tourmente et al 21 studies represent the only morphological data for spermatozoa within Viperidae and the Oliver et al 17 data on O. microlepidotus spermatozoa is the only study done on elapid spermatozoa.…”

“…17 Much of the morphological data presented here for Pelamis platurus corroborates the microanatomy of the mature spermatozoa described for the elapid Oxyuranus microlepidotus and the pitvipers Crotalus durissus, 8 Bothrops, 21 and with that of the spermatid descriptions for Agkistrodon piscivorus and A. contortrix. 9 Presently, Cunha et al 8 and Tourmente et al 21 studies represent the only morphological data for spermatozoa within Viperidae and the Oliver et al 17 data on O. microlepidotus spermatozoa is the only study done on elapid spermatozoa. There are several key differences seen within the spermatids of P. platurus that are not previously described for snakes.…”

“…These very long midpieces are considered a synapomorphy for snake speramtids and spermatozoa. 9 Dense bodies are present along with functional mitochondria within the midpiece of the P. platurus and Oxyuranus microlepidotus spermatozoa, which is similar to that described for Crotallus durissus 8 but in contrast to Agkistrodon 10 and to Bothrops species, 21 where dense bodies are absent from the midpiece. Typically 10-11 mitochondria/dense bodies are contained within each concentric ring of P. platurus midpieces.…”

“…During DNA condensation, the chromatin in P. platurus condenses in a spiral fashion, which was not documented in some squamates, 23 but was noted by Ferreira and Dolder 30 in the lizard Tropidurus itambre, in some Sceloporus species, 4 in the snake Cerastes cerastes, 14 and in Cottonmouths, 10 which resulted in large areas of open nucleoplasm. These open areas of nucleoplasm continue as lacunae within the body of fully condensed nuclei in maturing spermatids in P. platurus, which is similar to Bothrops spermatozoa 21 and A. contortrix elongating spermatids, 9 but seem to have been lost in A. piscivorus spermatids, 10 Oxyuranus microlepidotus, and many other snake spermatozoa. 9,17 Also during condensation and elongation, uniform translucent areas are seen on either side of the caudally located nuclear fossa where the flagellum attaches to the nuclear body of the developing spermatid.…”

“…Their large geographic range and aquatic lifestyle may allow this snake to serve as a model species for histopathological studies on the impact heavy metals and pesticides have on the testis and spermatogenesis. The results of this study will be compare with the ultrastructure of spermatid development in Agkistrodon piscivorus and A. contortrix, 9,10 to the spermatozoa morphologies of the South American Rattlesnake, Crotalus durissus, 8 to Bothrops alternatus and B. diporus, 21 to the elapid, Oxyuranus microlepidotus 17 and to the spermatozoa of other colubrid snakes. 9 Results from this study can subsequently be combined with ultrastructural data of spermiogenesis not only within snakes, but also to that of other squamates.…”