Abstract
Cephalopods (nautiluses, cuttlefishes, squids and octopuses) exhibit direct development and display two major developmental modes: planktonic and benthic. Planktonic hatchlings are small and go through some degree of morphological changes during the planktonic phase, which can last from days to months, with ocean currents enhancing their dispersal capacity. Benthic hatchlings are usually large, miniature-like adults and have comparatively reduced dispersal potential. We examined the relationship between early developmental mode, hatchling size and species latitudinal distribution range of 110 species hatched in the laboratory, which represent 13% of the total number of live cephalopod species described to date. Results showed that species with planktonic hatchlings reach broader distributional ranges in comparison with species with benthic hatchlings. In addition, squids and octopods follow an inverse relationship between hatchling size and species latitudinal distribution. In both groups, species with smaller hatchlings have broader latitudinal distribution ranges. Thus, squid and octopod species with larger hatchlings have latitudinal distributions of comparatively minor extension. This pattern also emerges when all species are grouped by genus (n = 41), but was not detected for cuttlefishes, a group composed mainly of species with large and benthic hatchlings. However, when hatchling size was compared to adult size, it was observed that the smaller the hatchlings, the broader the latitudinal distributional range of the species for cuttlefishes, squids and octopuses. This was also valid for all cephalopod species with benthic hatchlings pooled together. Hatchling size and associated developmental mode and dispersal potential seem to be main influential factors in determining the distributional range of cephalopods.
Highlights
The early life of marine organisms is a decisive phase as it determines survival and recruitment success dictating many aspects of the species population dynamics
Hatchling size was recorded for 110 species of cephalopods (30 sepioids, 27 squids, 53 octopods), ranging from 0.6 (Argonauta hians) to 28.0 (Graneledone boreopacifica) mm mantle length (ML), with an average size of 3.9±3.5 mm ML
The distribution of sizes for species with planktonic hatchlings showed a maximum for Enteroctopus megalocyathus (8.4 mm ML) and a minimum for A. hians
Summary
The early life of marine organisms is a decisive phase as it determines survival and recruitment success dictating many aspects of the species population dynamics. Cephalopods play an important role as predators and prey in marine ecosystems [4] and their relative abundances have increased worldwide in recent years [5] For adult cephalopods, both latitude and depth range have a significant effect on maximum body size, and temperature seems to be the most important factor in determining the distribution of adult body size along the continental shelves of the Atlantic Ocean [6]. Both latitude and depth range have a significant effect on maximum body size, and temperature seems to be the most important factor in determining the distribution of adult body size along the continental shelves of the Atlantic Ocean [6] These molluscs have both planktonic and benthic hatchling modes of life depending on the species. Most of the cephalopod species that have small hatchlings are planktonic during their early life, while those that produce larger hatchlings are usually benthic, with some exceptions
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