Holothuria (Halodeima) mexicana? Ludwig, 1875

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 : 147

Holothuria (Halodeima) mexicana? Ludwig, 1875

Reports for the Azores:

Holothuria mexicana Ludwig, 1875 —? $ Hérouard 1902: 7–8, pl. 1, fig. 16; Deichmann 1957: 9–11, figs. 21–38; Pereira 1997: 333; García-Diez et al. 2005: 51; Micael & Costa 2010: 323; Micael et al. 2012: 4.

Type locality: Gulf of Mexico .

See: Deichmann (1930: 74–76, pl. 5, figs. 15–20; 1957); Cutress (1996: 55, 63, figs. 4E–J, 7–9); Benavides- Serrato et al. (2012: 186–187).

Occurrence: Western Atlantic, in the Gulf of Mexico and the Caribbean ( Purcell et al. 2012); possibly extending its distribution to the Azores ( Hérouard 1902).

Depth: 0–20 m ( Laguarda-Figueras et al. 2001);? AZO: 98 m ( Hérouard 1902).

Habitat: sand, coralligenous to rocky substrates, coral reefs, seagrass beds, sandy or rubble bottoms and mangrove habitats ( Purcell et al. 2012).

Larval stage: planktotrophic ( McEdward & Miner 2001).

Commercial value: edible ( Purcell et al. 2012).

Remarks: Hérouard (1902) believed that the two specimens collected by Princesse Alice in the Azores (sta 882: 38°3’40”N, 28°34’45”W, 98 m) belonged to the tropical shallow-water species H. mexicana . Deichmann (1954), however, considered that the presence of H. mexicana in the East Atlantic was either due to mislabelling or to a recent introduction, but ‘without being really established’. We are more incline to believe that it was a result of a misidentification. Hérouard (1902) described the Azorean individuals as small and poorly preserved, with the calcareous ring partially dissolved, a particularity that could explain the absence of ossicles in the specimens, i.e. most probably dissolved by the used preservation medium. In the absence of diagnostic characters, the identification by Hérouard rested entirely on the colour pattern. He remarked on the small brown spots covering the dorsal side, which can be found in a number of holothurians species present in the NE Atlantic, including the Azores. In contrast, adults of H. mexicana typically have a black or dark brown upper side and light coloured under side, occasionally totally black or with brown spots ventrally and pale dorsally ( Deichmann 1930, 1954, 1957). Cutress (1996) described a colour pattern in small juveniles belonging to this species similar to what was observed by Hérouard. However, Cutress also noted that by the time juveniles reach 20 mm, the brown flecks already started to coalesce forming irregular dark patches. Hérouard did not mention the precise size of the second specimen, but the illustration given (pl. 1, fig. 1) was of a specimen of about 70 mm TL when alive (30 mm TL after preservation). Thus, the colour pattern as presented in this specimen does not support Hérouard identification as an animal at this size should have had a more solid colour pattern closer to what is observed in a typical H. mexicana adult. Furthermore, H. mexicana is a strictly shallow-water species, with a maximum reported depth of 20 m, which places the Azorean specimens outside its maximum depth range. Though, the small size of the Princesse Alice specimens and the destruction of main diagnostic characters make the identification of the specimens virtually impossible, the colour pattern and depth may offer some clues. For example, comparing the description and illustration presented by Hérouard with the one presented by Marenzeller (1893) for H. lentiginosa the two seem strikingly similar. The later was described based on a single specimen dredged by Hirondelle near Pico and Faial islands.