Sperm storage in coral snakes: a spermatozoa ultrastructural approach (Serpentes: Elapidae)

ABSTRACT

Reproduction in snakes employs a wide range of mechanisms such as long-term sperm storage, mating aggregations and male–male combat. These varied mechanisms can be better understood when combined with the study of the ultrastructural morphological variability of spermatozoa. Within the coral snakes, genus Micrurus, there are differences in the reproductive strategies adopted between monads (BRM) and triads (BRT); the aim of this work was to relate these two strategies to morphological differences among spermatozoa within different species. The semen of six Micrurus was collected using a non-invasive technique, fixed and processed for scanning and transmission electron microscopy. Micrurus spermatozoa have the same ultrastructure as those of other snake species, comprising the head, divided into acrosome, nucleus and neck; the midpiece; and the two parts of the tail, the principal piece and the end piece. Micrurus corallinus and Micrurus surinamensis presented evident multilaminar membranes occurring along all the pieces, while Micrurus frontalis and Micrurus altirostris showed cytoplasmic droplets occurring mainly in the midpiece. The differences found in spermatozoa morphology may be related with sperm storage in these four coral snakes, since the development of multilaminar membranes in the midpiece and the maintenance of cytoplasmic droplets in the mature sperm are both features related to extra energy provision for the spermatozoa while stored.