Population dynamics of Caprella dilatata and Caprella equilibra (Peracarida: Amphipoda) in a Southwestern Atlantic harbour

ABSTRACT

We studied the population dynamics and reproductive biology of Caprella dilatata and Caprella equilibra in order to provide the basis for understanding the ecological role of both species in Mar del Plata Harbour. Caprellids and organisms from the fouling community were obtained by sampling in the harbour, monthly from April 2014 to March 2015. Mean density of C. dilatata was homogeneous during most of the study period (ca. 50–200 ind/100 g) and reached their maximum in May (ca. 650 ind/100 g), while C. equilibra did not show any differences during the sampling period (ca. 30 ind/100 g). Juveniles of C. dilatata reached their highest densities in May, while ovigerous females were at their maximum values in late spring, summer and early autumn, and no correlation was found between seawater temperature and monthly density. On the other hand, C. equilibra reached its maximum juvenile and ovigerous female densities in summer, and showed a positive correlation with seawater temperature. Sex-ratio was female biased in C. dilatata, but in C. equilibra it was equal between sexes. The number of eggs carried by females was positively correlated to the size in both species. The present study suggests that the population dynamics of C. equilibra are intimately related to seawater temperature, while for C. dilatata no relationship was found. Future studies of ecology and behaviour traits in caprellid species are needed in order to determine the ecological role and the environmental factors that could affect both species.

KEYWORDS:

• Caprella dilatata
• Caprella equilibra
• harbour
• population dynamics
• reproductive biology

RESPONSIBLE EDITOR:

• Francesc Maynou

Acknowledgements

The authors would like to thank to Club Naútico de Mar del Plata for facilitating access to the docks. Two anonymous referees and Francesc Maynou (subject editor) provided useful comments that contributed to improve the final version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Universidad Nacional de Mar del Plata under grants EXA 610/12 and EXA705/14; and Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET) under grant PIP 112-201101-00830.