Thysanoteuthis rhombus: egg mass first record and paralarva distribution in the northeastern tropical Pacific

Presenting Author: Roxana De Silva

Authors: Roxana De Silva-Dávila [1], Raymundo Avendaño-Ibarra [1], Ricardo Palomares-García [1], Unai Markaida [2]

Affiliations:
1. Instituto Politécnico Nacional, CICIMAR – IPN. México.
2. El Colegio de la Frontera Sur, Pesquerías Artesanales, CONACYT. México.

An egg mass portion and one paralarvae of Thysanoteuthis rhombus found during summer 2008 in the northeastern Tropical Pacific and autumn 2014 in the Gulf of California, Mexico, respectively, represent the first evidence of reproduction of this species in the region. The egg mass portion was constituted by a gelatinous matrix in disintegration and contained 31,552 hatchlings from which 96.2% were premature, and 1,192 eggs at different developmental stages. Head chromatophore patterns, buccal crown pigmentation, arm and tentacles morphological indexes, and other morphological characteristics complement previous descriptions of Thysanoteuthis rhombus paralarvae. Zooplanktonic fauna associated to the egg mass included predatory copepods, fish larvae, and amphipods, among other. The composition of the egg mass portion and the oceanographic conditions suggest early stages of Thysanoteuthis rhombus may show a fast embryogenesis with early hatching, being able to exploit a wide environmental range. These characteristics, support its worldwide tropical subtropical distribution. Also, that predation by copepod and probably other cephalopods may contribute to a high mortality of paralarvae and juveniles.

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