Int. J. Dev. Biol. In Press
doi: 10.1387/ijdb.200157fo
© UPV/EHU Press

Mexican dancer in Ecuador: molecular confirmation, embryology and planktotrophy in the sea slug Elysia diomedea

Lola Moreano-Arrobo1, Oscar D. Pérez1,2,3, Federico D. Brown2,3, Fernanda X. Oyarzún*,4,5,6, Cristian B. Canales-Aguirre6,7

1Laboratorio de Biología del Desarrollo 113, Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Ecuador, 2Departamento de Zoología. Instituto de Biociências, Universidade de Sao Paulo, Brazil, 3Centro de Biologia Marinha (CEBIMAR), Universidade de São Paulo, Brazil, 4Centro de Investigación en Biodiversidad y Ambientes Sustentables (CIBAS), Universidad Católica de la Santísima Concepción, Concepción, Chile, 5Departamento de Ecología, Universidad Católica de la Santísima de Concepción, Concepción, Chile, 6Centro i~mar, Universidad de Los Lagos, Camino Chinquihue Km 6, Puerto Montt, Chile and 7Núcleo Milenio de Salmónidos Invasores (INVASAL), Concepción, Chile

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.

Keywords:

extra-zygotic yolk (EZY), spiral cleavage, reproductive mode, Sacoglossa

*Corresponding author e-mail: fernanda.oyarzun@ucsc.cl