Molpadiodemas villosus ( Théel, 1886a )

Madeira, Patrícia, Kroh, Andreas, Cordeiro, Ricardo, De, António M., Martins, Frias & Ávila, Sérgio P., 2019, The Echinoderm Fauna of the Azores (NE Atlantic Ocean), Zootaxa 4639 (1), pp. 1-231 : 178-179

Erroneous— Molpadiodemas villosus ( Théel, 1886a)

Reports for the Azores:

non Pseudostichopus villosus Théel, 1886 — $ Hérouard 1902: 11–13, pl. 2, figs. 1–3, pl. 7, fig. 3 [misidentified]; Grieg 1932: 4 [based on Hérouard 1902]; García-Diez et al. 2005: 51 [based on Hérouard 1902].

Type locality: off Japan, Pacific (35°22’N, 169°53’E) .

See: Théel (1886a: 170–171, as Pseudostichopus villosus ); O’Loughlin & Ahearn (2005: 164–165, figs. 2a, e, 7d–f, 8q–t, 12a–d).

Occurrence: cosmopolitan; in the Atlantic from the North American Basin south to the Scotia Sea and Antarctica ( O’Loughlin & Ahearn 2005).

Depth: 681– 5,304 m ( O’Loughlin & Ahearn 2005).

Habitat: soft sediments, from mud to ooze ( O’Loughlin & Ahearn 2005).

Larval stage: a probable brooder ( O’Loughlin & Ahearn 2005).

Remarks: Théel (1886a) remarked that among the material collected by H.M.S. Challenger off Chilean waters there were specimens closely resembling his newly described species Molpadiodemas villosus (= Pseudostichopus villosus ), but which lacked tube feet. Perrier (1902) believed that those specimens belonged to his newly described species, M. atlanticus . More recently, O’Loughlin & Ahearn (2005) re-examined the material in question and confirmed Perrier’s assumption. In the same year of Perrier’s publication, Hérouard (1902) reported Molpadiodemas villosus (= Pseudostichopus villosus ) from the archipelago based on the material collected by Princesse Alice (sta 652: 36°55’00”N, 22°22’45”W; 4,261 m). Coincidently, Hérouard’s description and figures presented an animal with a smooth surface, likewise close to the Chilean material taken by H.M.S. Challenger but not to M. villosus , which has a hairy like body surface. Deichmann (1930) compared her specimens of M. atlanticus from the Caribbe- an with Hérouard figures and concluded that they were identical. Perrier (1902) believed the distribution of ossicles could be used as a diagnostic character of M. atlanticus since M. villosus completely lacks ossicles in its tegument. Princesse Alice specimens completely lacked ossicles, except in the gonads. On the other hand, it is not uncommon for ossicles to dissolve during preservation, a problem Deichmann (1930) noted in her own M. atlanticus specimen. She attributed this to the acidic nature of the alcohol used to preserve her material. Moreover, in O’Loughlin & Ahearn (2005) ’s review stated that ossicles are not always present in this species.

Conversely, Deichmann (1930) omitted data on the internal anatomy, probably because her own specimen had almost no internal organs, due to evisceration. The striking difference that separates Princesse Alice material from M. atlanticus is its simple non-branching sac-like gonad structure. The genus Molpadiodemas as it was re-diagnosed by O’Loughlin & Ahearn (2005) encompasses only holothurians with branching gonads, with tubules arising from a common source at end of a gonoduct, thus excluding M. atlanticus and invalidating Deichmann’s (1930) suggestion. In contrast, O’Loughlin (2002) believed Princesse Alice ’s M. villosus belonged to the highly variable species Pseudostichopus peripatus , a close similar species known to occur in the Azores. Unlike M. atlanticus the unbranching gonad structure poses no diagnostic problem. However, O’Loughlin (2002) noted that Hérouard’s description encompassed far too large individuals (up to 170 mm), with no distinctive lateroventral margin, and as result the author marked the record as uncertain. Regardless, and in spite of the presence of both M. atlanticus and M. villosus in the vicinity of the Azorean, the presence of both species in the archipelago is still to be confirmed.