Background:

Isopods are highly diverse organisms, however, despite of their abundance and importance in ecological dynamics have been neglected in many of the aspects of their biology.

Objectives:

This paper analyses E. attenuata male and female histological characteristics, especially the reproductive structures, to increase the information of the reproductive biology and help to understand the sexual characteristics of other free-living isopods to favour comparative studies with other groups and environmental conditions.

Methods:

Organisms sampled between July 2010 and August 2011 were fixed and processed for histological preparations; Haematoxylin-Eosin and Lendrum staining techniques were applied to differentiate structures. Microphotographies were taken and analysed.

Results:

The internal organography was found to be similar on both sexes. The ovaries are modified during the maturation of the oocytes, after spawning, embryos are born in the marsupium. In some cases, a cohort in initial stages of maturation is observed in the dorsal region of the body in addition of the ones seen in the marsupium. A couple of testicles, comprising three cysts and in which different cell stages of spermatogenesis can be found, are observed in males.

Conclusions:

Since maturation of gametes occurs during the whole year, it is concluded that E. attenuata has a continuous reproductive cycle. We describe for the first time the reproductive characteristics of this isopod, which is important as reproductive aspects of these crustaceans have been neglected, thus, it is necessary to update and extend the morphological and histological information.