Zoological Studies

Vol. 45 No. 4, 2006

Postembryonic Growth, Development and Reproduction of Gammarus aequicauda (Martynov, 1931) (Gammaridae) in Laboratory Culture

Ermelinda Prato*, Francesca Biandolino, and Christian Scardicchio

CNR - Institute for Coastal Marine Environment, Section of Taranto, Via Roma 3, 74100 Taranto, Italy

Ermelinda Prato, Francesca Biandolino, and Christian Scardicchio (2006) Gammarus aequicauda (Martynov, 1931) (Gammaridae) is an epibenthic amphipod very well adapted to life in estuaries and shallow coastal waters. In Mar Piccolo in Taranto, Italy, it is the most abundant macrofaunal species of soft-bottom communities. The life history of G. aequicauda was analyzed in laboratory culture under controlled conditions of 18C and a salinity of 36 in order to assess postembryonic growth, development, and reproduction. Pairs of amphipods in precopula were observed daily until the female was found to be ovigerous. The fecundity was estimated as the number of juveniles released by each female. Juveniles produced in the laboratory were transferred to new aquaria, and at an interval time of 7 d, the head length was measured, the antennal segments were counted, and the sexual maturation stage was assessed. The mean time spent in precopula ranged 1-3 d and embryonic development ranged 5-8 d. The head length of newly born G. aequicauda was approximately 0.23 mm (0.1 mg dry weight), and the head reached a maximum length of about 1.8 mm (11.85 mg) after 140 d. There was a significant correlation between head length and the number of articles on the 1st antennae. A positive correlation between the number of juveniles and the size of G. aequicauda females (in terms of head length) was also observed. Females produced at least 3 consecutive broods with a mean offspring number of 19.3 13.3. Males were on average larger than females. The sex of the males could be determined at an age of 30-37 d, and the 1st precopula was observed after 40 d. The increase in egg volume during development was not significant (p > 0.05). Growth continued throughout life under laboratory conditions. One important feature of this study was to provide the essential basis for the development of laboratory toxicity tests with cultured animals. There are several advantages of using laboratory cultured populations: the individuals are close to a normal physiological state, they are capable of growing and reproducing in captivity; and the animals are of known ages and are available throughout the year.

Key words: Gammaridean amphipod, Life cycle, Laboratory culture.

*Correspondence: E-mail:linda.prato@iamc.cnr.it