Reproductive cycles and larval morphology of three Recent species of Argyrotheca (Terebratellacea: Brachiopoda) from Mediterranean submarine caves

Abstract

Although the three examined species of Argyrotheca are quite common in the Mediterranean, little is known about their reproductive cycles. This study shows that Argyrotheca cordata and Argyrotheca cistellula have continuous breeding activity, indicated by the occurrence of ripe eggs and larvae in their brood pouches throughout the year. The absolute number of larvae found in the brood pouches of both species corresponds to the adult's size. The third species examined, Argyrotheca cuneata, tends to breed in autumn, with larvae only present in September and November, but the sample-size was small. Larval development is very similar in all three Argyrotheca species, each embryo going through a gastrula stage, a two-lobed and a three-lobed stage. Before leaving the brood pouch, the larvae have an apical lobe with a girdle of elongated cilia, a mantle lobe with a midventral band of cilia and a pedicle lobe without ciliation. The larvae of A. cordata and A. cuneata possess four bundles of larval setae, whereas A. cistellula shows no setae at all.