Embryonic Abnormalities of Two Seaslug Species from South Spain

Resumen

The spawns and the embryonic development of the nudibranch species Polycera aurantiomarginata (García and Bobo in Cah Biol Mar 25:361–373, 1984) and Polycera quadrilineata (Müller, 1776) were studied for two years. Throughout this study some abnormalities were detected in the embryonic and larval development of both species. First, the spawn seemed a pearl necklace because the eggs did not have intracapsular liquid and the capsular wall appeared very close to the egg. Second, embryos showed a normal development until the gastrula stage then a transparent sphere with two opposite cilia tuffs was developed instead the normal veliger larva. Third, aberrant veliger larvae were detected, in P. quadrilineata some of them showed a black zone. In P. aurantiomarginata the teratological events could be related to adult size and spawn number. Animals smaller than 15 mm never laid viable spawns while the egg masses of adults with 16–25 mm in size showed abnormalities in 80%. In the other hand, it is remarkable that animals bigger than 25 mm, which had already spawned several times, laid egg masses with abnormalities. The percentage of pearl necklace spawns was bigger in P. aurantiomarginata than in P. quadrilineata, while the percentage of spawns with aberrant veligers was bigger in the last one. However the values of egg masses with transparent ciliated spheres were similar in both species.