''Macrotritopus'' is a poorly known

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...

es in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Octopodidae The Octopodidae comprise the family containing the majority of known octopus species (about 175 species). Genera The World Register of Marine Species lists these 23 genera: *'' Abdopus'' Norman & Finn, 2001 (7 species) *'' Ameloctopus'' Norman, ...

. As it stands, ''Macrotritopus'' contains two valid described species, '' Macrotritopus defilippi'' from the NE Atlantic and Mediterranean, and ''

Macrotritopus beatrixi ''Macrotritopus'' is a poorly known genus of octopuses in the Family (biology), family Octopodidae. As it stands, ''Macrotritopus'' contains two valid Species description, described species, ''Macrotritopus defilippi'' from the NE Atlantic and M ...

'' from the Caribbean and SW Atlantic. Two poorly described, unresolved taxa are known only from planktonic hatchlings ('' Macrotritopus equivocus'' and '' M. scorpio''), and a further three undescribed

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

species may be attributable to this genus. The genus ''Macrotritopus'' was described by Grimpe (1922) for the single planktonic specimen of ''Octopus gracilis'' Verill, 1884, the name referring to the very long third arm pair on the paralarvae. Given that ''O.'' ''gracilis'' Verill, 1884 was a junior homonym of '' O. gracilis'' Souleyet, 1852, authors Joubin & Robson (1929) replaced it with ''Octopus'' (''Macrotritopus'') ''equivocus'', with ''Macrotritopus'' regarded as a subgenus at that time, these authors also described ''M. danae''. For a time these ''Macrotritopus'' species (all known from paralarvae) were misidentified as juveniles of ''

Scaeurgus unicirrhus ''Scaeurgus'' is a genus of octopuses in the family Octopodidae. The species of this genus are characterized by inhabiting the upper bathyal benthic zone from temperate and tropical latitudes in all major oceans. Species * ''Scaeurgus jumeau'' ...

''. Researchers in the late 1970s/early 1980s proved that ''Macrotritopus'' paralarvae from the Atlantic grew into the previously described ''Octopus deflippi'' Verany, 1851, thus connecting the juveniles with the adults (and moving ''Octopus deflippi'' to genus ''Macrotritopus''). Therefore, the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

of ''Macrotritopus'' (''M.'' ''equivocus'') is a juvenile, and ''M. defillipi'' was the only species where the adult form was known (until the 2018 description of ''M. beatrixi''). The presence of "''Macrotritopus'' larvae" off South Africa and the Indo‑West Pacific from Australia to

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

indicates that there may be a number of yet to be described species within this genus.

Description

The genus ''Macrotritopus'' are small octopus with elongate-ovoid mantle, and with long and slender arms 4-7 times the mantle length and with the third arm pair distinctly longer than the others (and with the dorsal arm pair always shortest). The arms are also capable of

autotomy Autotomy (from the Greek ''auto-'', "self-" and ''tome'', "severing", αὐτοτομία) or 'self-amputation', is the behaviour whereby an animal sheds or discards an appendage, usually as a self-defense mechanism to elude a predator's grasp ...

near the arm bases, have only very shallow webbing, and the males have a very small hectocotylus on the third right arm (hectocotylus length <3% the arm length). Molecular work which includes ''Macrotritopus'' sp. from the SW Atlantic (possibly ''M.'' ''beatrixi'') has recently shown that the genus groups very closely with ''

Thaumoctopus mimicus The mimic octopus (''Thaumoctopus mimicus'') is a species of octopus from the Indo-Pacific region. Like other octopuses, it uses its chromatophores to disguise itself. It is noteworthy for being able to impersonate a wide variety of other marine ...

'' and ''

Wunderpus photogenicus ''Wunderpus photogenicus'', the wunderpus octopus, is a small-bodied species of octopus with distinct white and rusty brown coloration. 'Wunderpus' from German "wunder" meaning 'marvel or wonder'. Due to the appearance and behavior of the wunder ...

'', which are also long-armed species living in shallow sandy environments.

Species

*'' Macrotritopus defilippi'' ( Vérany, 1851), Type species of genus, restricted to NE Atlantic and Mediterranean ('' Macrotritopus danae'' Joubin & Robson, 1929 is considered a synomym) . *'' Macrotritopus equivocus'' ( Robson, 1929) (''

taxon inquirendum In biological classification, a ''species inquirenda'' is a species of doubtful identity requiring further investigation. The use of the term in English-language biological literature dates back to at least the early nineteenth century. The ter ...

'', juvenile: identity unresolved) *'' Macrotritopus scorpio'' (

Berry A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit although many pips or seeds may be present. Common examples of berries in the cul ...

, 1920) (''taxon inquirendum'', unresolved, potential name for West Atlantic "''defillipi''") *''

'' (Guerrero-Kommritz & Rodriguez-Bermudez, 2018), Described for adult ''Macrotritopus'' from the southern Caribbean, it is probably a junior synonym of ''M. scorpio'', but this couldn't be determined by the authors, who thus chose to allocate it a new name.

References

{{Taxonbar, from=Q18592031 Octopuses Cephalopod genera Taxa named by Georg Grimpe