Reproductive biology of two species of Hyalella Smith, 1874 (Crustacea: Amphipoda: Hyalellidae) from southern Brazil

ABSTRACT

Reproduction is a critical event in the life cycle of animals, and a high amount of energy is allocated to it. The aim of this study was to characterize the reproductive biology of two recently described species of Hyalella from the north-east region of state of Rio Grande do Sul in southern Brazil. The specimens were collected during 12 months from a stream source (Hyalella georginae) and from a water reservoir (H. gauchensis), in Palmeira das Missões municipality, state of Rio Grande do Sul. Upon sampling, ovigerous females and pairs in precopulatory behaviour were separated into microtubes. In the laboratory, the cephalothorax length (CL in mm) of all specimens was measured. Male size at onset of sexual maturity was larger than that of the females, in both species. There was a correlation between the size of paired males and females: larger males carried larger females, in both Hyalella species. Precopulatory pairs were found throughout the year; however, H. georginae had a higher frequency in spring, and H. gauchensis in autumn. There was a positive correlation between the CL of ovigerous females and the number of eggs/juveniles. A reduction in the number of eggs throughout the embryonic development was observed in H. georginae. The average fecundity of H. georginae was significantly higher than H. gauchensis. The differences between the reproductive biology of these species may be related to the physical and environmental conditions at which they are exposed in their habitats.

KEYWORDS:

• Fecundity
• sexual maturity
• amphipods
• reproductive biology

Acknowledgements

Coordination of Higher Education Personnel Improvement CAPES for the financial support provided to me by granting scholarship and National Council for Scientific and Technological Development CNPq. Colleagues of Zoology and Ecology Laboratory, CESNORS, Federal University of Santa Maria for help in carrying out the collection and sorting of materials and in particular Vanessa de Castro for the help during the process by which individuals were measured.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by [Coordination of Higher Education Personnel Improvement CAPES and National Council for Scientific and Technological Development CNPq] under Grant [Proc. number 405061/2015-3].