Abstract:
Elysia diomedea varies in adult size and color across its geographical distribution in
Ecuador. Because of morphological variation and the absence of genetic information
for this species in Ecuador, we analyzed mtDNA sequences in three populations
(Ballenita, La Cabuya, and Mompiche) and confirmed that (1) individuals from the
three locations belonged to E. diomedea and (2) that there was no population structure
that could explain their morphological differences. Next, we analyzed general aspects
about the reproductive biology and embryology of this species. Live slugs from the
Ballenita population were maintained and reproduced ex situ. Egg ribbons and
embryos were fixed and observed by brightfield and confocal microscopy. We
observed a single embryo per capsule, 98 embryos per mm2 of egg ribbon, and
compared the cleavage pattern of this species to other heterobranchs and spiralians.
E. diomedea early development was characterized by a slight unequal first cleavage,
occurrence of a 3-cell stage in the second cleavage, and the formation of an enlarged
second quartet of micromeres. We observed clear yolk bodies in the egg capsules of
some eggs ribbons at early stages of development. Both reproductive and
embryological characteristics, such as presence of stomodeum in the larva, and
ingestion of particles after hatching confirmed the planktotrophic veliger larvae of this
species, consistent with the majority of sacoglossans from the Eastern and Northeast
Pacific Oceans.