First detection of an ocellate octopus in the Revillagigedos ecoregion, a biodiversity hotspot located in the Tropical East Pacific Province

Alejandra Valdez-Cibrián,Jesús Emilio Michel-Morfín,Mariana Díaz-Santana-Iturrios,Víctor Landa-Jaime

doi:10.3897/zookeys.986.53250

Abstract

The biodiversity of mollusks, particularly cephalopods, has not been exhaustively determined in the Revillagigedos ecoregion, which is a biodiversity hotspot for several marine groups located in the Tropical East Pacific Province. In our study, we detected and examined ocellate octopuses from Socorro and Clarion Islands, and determined their identity using morphological criteria and molecular data from two mitochondrial genes (COIII and COI). The taxon identified was Octopus oculifer, a species considered endemic to the Galapagos Archipelago. In addition, according to our analyses, O. mimus, O. hubbsorum and O. oculifer are very closely related and may represent a species complex comprised of three morphotypes. We found that the evolutionary relationships among octopuses are not determined by the presence of ocelli. This study is the first to report a clade represented by ocellate and non-ocellate species, in addition, the identity of cephalopods in the Revillagigedos was determined with analytical support.

Highlights

Octopuses are soft-bodied cephalopods of the order Octopoda Leach, 1818, which comprises 13 families with around 300 pelagic or benthic species (Jereb et al 2016)
The individuals analyzed belonged to the genus Octopus Cuvier, 1797; these presented an ink sac and suckers in a two-row arrangement
The individuals were identified as Octopus oculifer (Hoyle, 1904) based on morphological and molecular examinations; the overlap of characters among the species reviewed in literature, especially between O. oculifer and O. hubbsorum, and the slight variation of arm formula in regard to original description (i.e., 3>4>2>1 instead of 3>2>4>1), explained why Jereb et al (2016) pointed out that these species are a confusing complex that needs to be carefully re-evaluated (Table 3)

Summary

Introduction

Octopuses are soft-bodied cephalopods of the order Octopoda Leach, 1818, which comprises 13 families with around 300 pelagic or benthic species (Jereb et al 2016). The family Octopodidae dOrbigny 1940 includes 13 ocellate species catalogued in two genera, Octopus Cuvier, 1797 and Amphioctopus Fischer, 1882 (Jereb et al 2016). Ocellate species (Octopus cyanea (Gray, 1849), Amphioctopus exannulatus (Norman, 1993), A. fangsiao (d’Orbigny, 1839‐1841), A. kagoshimensis (Ortmann, 1888), A. mototi (Norman, 1993), A. neglectus (Nateewathana & Norman, 1999), A. rex (Nateewathana & Norman, 1999), A. siamensis (Nateewathana & Norman, 1999), A. ovulum (Sasaki, 1917), O. bimaculatus Verrill, 1883 and O. bimaculoides Pickford & McConnaughey, 1949) inhabit the Indian, Indo-Pacific and northwestern Pacific Oceans, except for O. maya Voss & Solis, 1966 and O. oculifer (Hoyle, 1904), which are considered endemic to the Yucatan Peninsula and the Galapagos Archipelago, respectively (Jereb et al 2016). Diagnostic features are highly valuable and needed, mainly due to the increased number of taxonomic confusions that derive from overlapped morphological characters among species (Norman and Hochberg 2005). Octopodids from the northeastern Pacific are no exception, for instance, Pliego-Cardenas et al (2014) suggested that O. mimus Gould, 1852 and O. hubbsorum Berry, 1983 could be conspecific, and Díaz-Santana-Iturrios et al (2019) confirmed that O. californicus Berry, 1911 and O. alecto Berry, 1953 should be reassigned into new genera

Methods

Results

Conclusion