HISTOLOGICAL AND MORPHOLOGICAL CHARACTERIZATION OF THE DEVELOPMENT OF THE KOLLIKER'S ORGANS OF GREEN OCTOPUS OCTOPUS HUBBSORUM

Incirrate octopodes are the only cephalopods that exhibit transient epidermal structures called Kolliker's organs (KO) in the early development stages. This work describes for the first time the histological formation process of these organs during embryonic development and of the paralarva of Octopus huhbsorum Berry, 1953, as well as their morphological characteristics. Egg masses were collected in the Gulf of California and the species was identified by molecular analysis. The histological formation of KO starts when the funnel is fully developed and ends when the embryo is ready for hatching. Differences were observed compared with the only complete histological description of KO currently available. In O. huhbsorum, the basal membrane wraps the basal and lateral cells until the KO erupts, and the cell conformation of KO (binding with muscle cells) is completed when the mantle covers the ventral margin of the funnel and chromatophores are visible. The KO of O. huhbsorum are of intermediate size and show a higher density compared with other species, especially in the arms. The cellular degradation of KO is reported here for the first time; KO disappears within 48 h posthatching, contrary to observations reported for other species in which these organs last more than 30 days, even before settlement. It is concluded that in this species, KO probably facilitate hatching or are an evolutionary reminiscence, and it is ruled out that they facilitate buoyancy before settlement. KEY WORDS: cephalopods, embryo, paralarvae, epidermis, octopus
INTRODUCTION Particularly in octopuses, the external morphology of some species varies markedly during early development (embryo, paralarva, and juvenile), including the number of suckers per arm, arm length, and chromatophore [...]