The eggs and hatchlings of the octopus Robsonella fontaniana (Cephalopoda: Octopodidae)

Abstract

Very little is known about the life history of Robsonella fontaniana. In particular, there are no descriptions of the early life stages that enable correct identification of samples taken from the wild. In this work, eggs and hatchlings are described from egg clutches obtained in the field with brooding females and incubated until hatching. Individual eggs exhibited marked differences in stages of embryonic development within egg clutches or even within a single egg string. For one clutch collected at early stages of embryonic development, embryogenesis took 91 days at 11.5 °C and for a second clutch at intermediate developmental stages it took 68 days at 11 °C and 39 days at 14 °C. For the later clutch the hatching period lasts 25 days at 14 °C. The eggs and paralarvae were small, with an egg length of 3.9-5.2 mm, a dorsal mantle length of 2-3 mm and a total paralarvae length of 3.4-6.0 mm. Chromatophore shape and distribution presented a very distinctive pattern. Characteristics of the eggs, egg strings and paralarvae make it possible to distinguish the early stages of R. fontaniana from those of other octopodid species found off the Atlantic coast of Patagonia.