Descripción de la paralarva del calamar ommastréfido Todarodes sagittatus, obtenida por fertilización in vitro

Abstract

Little is known about the early life stages of oceanic squid, yet such information is critical to a meaningful understanding of this ecologically and economically important group. Major limitations to the study of these stages derive from the difficulty of species correct identification and the fact that currently, the larval forms of many species are still unknown. This work describes the morphology and chromatophore pattern of the ommastrephid squid Todarodes sagittatus paralarvae. Morphological characteristics, such as the peg number of the proboscis suckers, and chromatophore pattern, provide valuable taxonomical tools to discriminate the paralarvae of T. sagittatus from other ommastrephid species described to date. Using in vitro fertilization techniques, fertilized eggs were obtained and incubated at 15 and 17 ºC until hatchling stage. The fertilization and survival rates of these experiments were low and, as observed in other oceanic squid fertilized in vitro, all individuals hatched prematurely. By comparing the final developmental stages of this species, we also attempted to identify its natural hatching stage. In agreement with the putative morphological features of a rhynchoteuthion hatchling in nature, developmental stage XXXII is here proposed as this species natural hatchling stage. Furthermore, hatchling behaviour, including proboscis extension, is also reported. This work thus highlights the morphological features of T. sagittatus paralarvae, hopefully contributing to our knowledge of rhynchoteuthion paralarvae