Natural Diet of Aegla platensis Schmitt and Aegla ligulata Bond-Buckup & Buckup (Crustacea, Decapoda, Aeglidae) from Brazil¹

BUENO², A.A.P. & BOND-BUCKUP³, G.

¹ Contribution n° 429 to the Departamento de Zoologia, Instituto de Biociências, Programa de Pós- Graduação em Biologia Animal, Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brasil.Address for correspondence:

² Laboratório de Ciências Fisiológicas, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga 6681, prédio 12, CEP 90619-900, Porto Alegre, RS, Brasil aapbueno@pucrs.br.

³ Departamento de Zoologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves, 9500, prédio 43435, CEP 91501-970, Porto Alegre, Rio Grande do Sul, Brasil ginabb@ufrgs.br.

ABSTRACT: This work aimed to characterise the trophic ecology of Aegla platensis and A. ligulata, especially regarding the food habits and circadian and seasonal variations occurring in the diet of juveniles and adults. Samplings were done from August 1999 to August 2000 from Mineiro Creek, Taquara, and from another Creek forming the Tainhas River, São Francisco de Paula, RS, respectively. Monthly, on each place, five juveniles, five males and five females were collected, at four times of the day. Stomach contents were analysed using: an estimate of the Degree of Fullness (DF), the Frequency of Occurrence (FO) and the Point Method (PM). Analysis of variance (ANOVA) was used to detect statistical differences in the DF of males and females, adults and juveniles, for different seasons and times of the day sampled. Cluster Analyses and Principal Coordinate Analyses were used to compare the diet of juveniles and adults. A total 760 stomachs of A. platensis and 703 of A. ligulata were analysed. Aegla platensis had 650 stomachs with content and 110 had empty ones, while in A. ligulata 643 stomachs showed some content and 60 were empty. The most representative items found in the stomachs were plant debris, algae, sand, immature insects of the orders Diptera, Ephemeroptera, Trichoptera and microcrustaceans like Ostracoda and Cladocera, along with Amphipoda. There were no significant differences between the feeding habits of males and females on either species. However, values of DF were higher at 24h in A. platensis and at 18h in A. ligulata. The multivariate analyses detected differences in the diets of juveniles and adults of both species. Based on these information it can be concluded that these aeglids are, regarding their natural diet, omnivorous generalists, and opportunistic.

Key-words: Crustacea, Decapoda, Aeglidae, natural diet.