Mesothuria intestinalis

Erroneous— Mesothuria intestinalis (Ascanius, 1805) Reports for the Azores:

Mesothuria intestinalis (Ascanius, 1805) — Mortensen 1927a: 381; Nobre 1938: 150–152; Deichmann 1954: 385–386; Tortonese 1965: 69–70, fig. 26; Pérez-Ruzafa et al. 1992b: 144; Micael & Costa 2010: 323; Micael et al. 2012: 4.

Type locality: Norway.

See: Gebruk et al. (2012: 291–300, figs. 1, 9C–D).

Occurrence: Mediterranean Sea and North Atlantic, from the Caribbean waters eastwards to the Gulf of Guinea, north to Scandinavian waters, including Canaries (Gebruk et al. 2012).

Depth: 20– 2,480 m, infralitoral depths tend to be restricted to higher latitudes (Gebruk et al. 2012).

Habitat: muddy substrates, usually covers itself with shell fragments and other bottom material (Mortensen 1927a).

Larval stage: probably direct or lecithotrophic; hermaphroditic (Mortensen 1927a).

Remarks: historically, reports of M. intestinalis and M. verrilli are intermingled. For example, Hérouard (1902) considered M. verrilli as just a variety of M. intestinalis, and placed the material collected by Princesse Alice under the later. Hérouard decision led subsequent bibliography (e.g., Mortensen 1927a; Nobre 1938) to include M. intestinalis in the Azorean fauna, disregarding the specific value of the variety. Later, Hérouard (1923) reconsidered M. verrilli as distinct species, an ‘abyssal representative’ of M. intestinalis. On reviewing M. verrilli historical material from the NE Atlantic (including the material taken by Talisman in Azorean waters), Gebruk et al. (2012) discovered a second species, M. milleri. Additionally, by studying ontological changes in M. milleri Gebruk recognized his new species in the M. verrilli descriptions by Marenzeller (1893) and Hérouard (1902, 1923). Coincidently, such age dependent variation is very close as well of what is known for M. intestinalis, leading to the possibility of both species being present among the material collected in the Azores by Princesse Alice and Hirondelle. Conversely, Gebruk et al. (2012) also remarked that M. intestinalis is easily distinguished from other Mesothuria species by having a sequential hermaphrodite gonad. This particularity was acknowledged by Hérouard (1923) at the time and used this diagnosing character to further substantiate the promotion of M. verrilli to a distinct species. Marenzeller (1893) described Hirondelle ’s specimens as gonochoristic. Thus, the presence of M. intestinalis is still to be confirmed in the Azores in spite of its widespread distribution in the North Atlantic (see remarks under M. milleri).