First description of eggs, hatchlings and hatchling behaviour of Enteroctopus megalocyathus (Cephalopoda : Octopodidae)

摘要

As for many other commercially exploited octopodid species, there are no detailed descriptions of the eggs and hatchlings of Enteroctopus megalocyathus that can be used for the identification of individuals captured in plankton samples. Eggs, clutches and hatchlings are described here for the first time and compared with those of both other Patagonian octopodids and other Enteroctopus species. Relative to other Enteroctopus, hatchlings were large with total length (TL) 14.8-21.5 mm, mantle length (ML) 7-9.5 mm and arm length (AL) representing 90.5% of the mantle. Dorsal chromatophores were more abundant than ventral ones, and their shape and distribution created a very distinctive pattern. Eggs and hatchlings were found to have several characteristics that can be used for species identification. Although the mode of life of newly hatched cephalopods is often categorized as either planktonic or benthic, the hatchlings in aquaria showed no preference for swimming or settling. Additionally, the size of eggs and hatchlings which is correlated with the mode of life at hatching in other octopodid species, fitted both planktonic and benthic in E. megalocyathus. Furthermore, morphological and behavioural characteristics were similar to the pre-settlement stage of planktonic hatchlings of Octopus vulgaris. Therefore, we suggest that hatchlings of E. megalocyathus have an unusual, suprabenthic mode of life.