Pinnoctopus, Enteroctopus or Octopus

Steve O'Shea

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Nov 19, 2002
Recently Norman & Hochberg (2005) have proffered a review of the current status of octopus taxonomy that alternately disregards, misrepresents and misreports earlier research to such an extent that I am compelled to critique their account herein. To a great extent this critique quotes passages directly from the contributions of O'Shea (1999) and Norman & Hochberg (2005). This brief critique concerns the systematic status of the genera Pinnoctopus d’Orbigny, 1845, Macroctopus Robson, 1928, Callistoctopus Taki, 1964 and Enteroctopus Gould, 1852; and reaffirms the distinction between ‘poor preservation’ and ‘initial treatment history’.

Pinnoctopus cordiformis
Norman & Hochberg 2005 (130) state “In the absence of type material, O’Shea resurrects Pinnoctopus cordiformis (Quoy and Gaimard, 1832) as the senior synonym of Macroctopus maorum Hutton, 1880 [sic.]. Quoy and Gaimard’s original description of cordiformis refers to a large animal with arms of almost equal length, the lateral pairs being slightly shorter. This arm formula does not match with that of the species previously treated under the name maorum, which has an arm formula of 1>2>3>4, the dorsal arms being obviously longer and more robust than the subsequent arm pairs. Quoy and Gaimard’s description more closely matches Enteroctopus zealandicus, another large octopus found in the same general region. The genus Pinnoctopus was coined by Orbigny (1845) with the diagnostic character of a fin-like flap around the margin of the mantle. We believe that this structure is an artefact of poor preservation, where loose skin settles in a flange around the lateral mantle border. We have observed such a structure while preserving specimens of Enteroctopus dofleini (Wülker, 1910) from the northern Pacific Ocean. This has not been observed while preserving specimens of maorum. This preservation artefact further supports the suggestion that Quoy and Gaimard's species is in fact a member of the genus Enteroctopus (namely zealandicus). In the light of this confusion, the limited original description and the absence of a type specimen for cordiformis, we chose at this stage to leave the name Pinnoctopus cordiformis as unresolved, making Macroctopus maorum the available name for the distinctive species found in New Zealand and temperate Australian waters.”

Recognising artefacts caused by initial treatment history is necessary to accurately differentiate species in museum collections that have been fixed in a variety of ways (O'Shea 1997). I do not know what curatorial practices are followed in the laboratories of either Norman or Hochberg, so cannot discount the possibility that poor preservation is responsible for observed lateral flanges in their Enteroctopus; however a distinction must be drawn between initial treatment history and poor preservation, and Norman and Hochberg do not do so. With this in mind, the following description is made for P. cordiformis by myself (1999: 136): “Mantle elongate to ovoid (MW about 36-95% ML), dorsoventral compression absent; lateral keel or fold of skin absent in live- or narcotised-fixed specimens but often present in postmortem-fixed material.” Additionally, I (ibid.: 138, 139, Figs 86A, C) illustrate two specimens of P. cordiformis with the lateral fold of skin clearly visible around the mantle; both specimens were received frozen, and were defrosted and subsequently fixed. Moreover, in a redescription of P. kermadecensis (Berry, 1914), I (ibid.: 144, 145) state “The ‘adventitious’ fold of skin around the mantle described for this specimen is very obvious [referring to the type], but is, however, absent on the only other known specimen identified as this species. This lateral fold of skin has already been attributed to an artefact of preservation in P. cordiformis.”

Norman & Hochberg might well have limited experience fixing specimens of Australian ‘O. maorum’, especially those received frozen prior to fixation, although this does not excuse their flagrant disregard of a detailed description of this species (as P. cordiformis) based on 71 specimens deliberately subjected to various initial treatment histories to determine the relationship between ‘keeled’ and ‘non-keeled’ morphologies (O’Shea ibid.: 135-143), or further disregarding two full-page plates of this species dedicated to depicting the ‘keeled’ condition. To the contrary, no lateral fold of skin has been observed in any of 37 fresh (live or narcotised) or frozen (and subsequently thawed, fixed and preserved) specimens attributed to Enteroctopus zealandicus (Benham, 1944) (O’Shea ibid.: 183-191). With regard to type specimens, I (1999: 135) state “Given that the holotype of P. cordiformis is not extant (Lu et al. 1995) a neotype is designated for it to stabilise the concept of Pinnoctopus.”; therefore type material is extant, although this fact is also overlooked by Norman & Hochberg. The only ‘confusion’ (sensu Norman & Hochberg) here is that generated by these two authors’ evident inability to read a systematic work in sufficient detail to comprehend it.

With regard to the arm formula, I (1999: 176) cite for P. cordiformis “Arms slender, very short to long (female about 58-83% TL; male about 32-84% TL), gradually tapering to delicate tips; arms 1 and 2 usually longest, 3 and 4 shortest, without consistent disparity in relative arm lengths.” Arm formulae are given for 9 specimens, with slight damage precluding an accurate formula being determined for three others (O’Shea ibid: Tables 63, 64: 142); the formula is certainly not as simplistic as relayed by Norman & Hochberg, the generalised 1>2>3>4, although the dorsal arms are almost invariably longest (the lateral arms are often only marginally shorter than the dorsal pair; moreover, the arm formula on right and left sides of the animal most often differs). For E. zealandicus the arms and arm formula are cited as “Arms thick, square to ovoid in section, very short to long (AL about 48-81% TL), gradually tapering to not unduly delicate tips; no consistent disparity in relative arm lengths apparent” (O’Shea ibid.: 183-191). The arm formula in E. zealandicus is variable, with any arm potentially the longest; almost every arm formula combination is manifested in one of the 6 specimens for which this could be reliably determined (O’Shea ibid.: Tables 91, 92, p. 186). Thus the arm formula is an unreliable character state for differentiating Pinnoctopus from Enteroctopus, and Norman & Hochberg’s justification for doing so is moot.

Norman & Hochberg also disregard the unusual pigmentation regime of Pinnoctopus (illustrated by Quoy & Gaimard with blue lunules) and that of Enteroctopus, and the bathymetric and geographic distribution of these two species. Enteroctopus zealandicus is quite unusual in that “Specimens fixed live or narcotised entirely smooth bodied; enlarged ocular cirri not apparent. Post-thaw-fixed specimens with entire dorsal and ventral body surfaces light orange coloured.” (O’Shea ibid.: 185), to which I herein add ‘uniformly so’. This is clearly inconsistent with the description for Pinnoctopus, with its reticulated and blotched pattern of variously coloured chromatophores, distributed over a surface that is anything but smooth (O’Shea ibid.: 137). Additionally, the type locality of P. cordiformis, Tasman Bay (northernmost South Island), is an area in which the species ‘Octopus maorum’ is common in intertidal and shallow sublittoral waters, and from which Enteroctopus zelandicus is not known (O’Shea 1999). Norman & Hochberg allude to synonymy of P. cordiformis and E. zealandicus partly on grounds of sympatry, in that these two species occur “in the same general region”, but the reality is that their recognised intertidal distribution is separated by no less than 9° latitude, and their bathymetric distribution by about 400 metres.

... contd.
Although Norman & Hochberg suggest Enteroctopus zealandicus (Benham) is a junior synonym of Pinnoctopus cordiformis (Quoy & Gaimard), and for this reason refer the species (frequently referred to as) ‘O. maorum’ to the genus Macroctopus, their rationale is fundamentally flawed and confused; the two species cannot be considered either conspecific or congeneric. Accordingly, no justification exists for considering Pinnoctopus distinct from Macroctopus, nor is there any reason for recognising Macroctopus distinct from Callistoctopus. Earlier I had concluded (O’Shea 1999: 134, 135), “Pinnoctopus is the oldest available name for a complex of species characterised by possession of long dorsal arms. It has frequently been referred to as the Octopus macropus or Callistoctopus complex. Since Octopus maorum is a junior synonym of Octopus cordiformis, and O. cordiformis is the type species of Pinnoctopus and typical of the O. macropus group, Macroctopus and Callistoctopus are both junior synonyms of Pinnoctopus.” Hypocritically Norman & Hochberg (138) refer ‘Polypuskermadecensis Berry, 1914 to Callistoctopus - a species clearly congeneric with maorum and therefore referable to Pinnoctopus, as earlier referred (O’Shea ibid: 143). Norman & Hochberg’s critique leads to an untenable situation where three genera are unnecessarily proposed to accommodate a single group of related species, Pinnoctopus, Macroctopus and Callistoctopus, for which the single valid taxon is Pinnoctopus.

Lu CC, Boucher-Rodoni R, Tillier A 1995. Catalogue of types of Recent Cephalopoda in the Muséum national d’Histoire naturelle (France). Bulletin of the Muséum National d’Histoire Naturelle 17: 307-343.

Norman MD, Hochberg FG 2005. The current status of octopus taxonomy. Phuket Marine Biological Centre Research Bulletin 66: 127-154.

O’Shea S 1997. A new technique for assessing fixation-induced morphological variation in octopus (Mollusca: Cephalopoda). New Zealand Journal of Zoology 24: 163-166.

O’Shea S 1999. The marine fauna of New Zealand: Octopoda (Mollusca: Cephalopoda). NIWA (National Institute of Water & Atmospheric Research Ltd) Biodiversity Memoir 112: 280pp.

Quoy JRC, Gaimard J 1832. Mollusques. In Voyage de décourtes de l’Astrolabe pendant les années 1826-1829, Zoologie 2: 1-320. Paris.

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