Dipodarctus subterraneus ( Renaud-Debyser, 1959 )

Bartels, Paul J., Fontoura, Paulo & Nelson, Diane R., 2018, Marine tardigrades of the Bahamas with the description of two new species and updated keys to the species of Anisonyches and Archechiniscus, Zootaxa 4420 (1), pp. 43-70 : 55-56

Dipodarctus subterraneus ( Renaud-Debyser, 1959)

Material examined: Six specimens. Four specimens collected from site 15 (2 females, 108 and 109 µm long, and 2 individuals of unknown gender, 1 was 99 µm long and the other not properly oriented to be measured); and 2 females (98 and 99 µm long) collected from site 2.

Remarks: Five species are currently known in the genus Dipodarctus . In three of these, one digit on legs I–III is much longer than the other digits. According to their original descriptions, in two other species, D. anaholiensis Pollock, 1995 and D. subterraneus , all digits on legs I–III are similar in length. However, in specimens attributed to D. anaholiensis from French Polynesia the innermost digit on legs I–III is slightly but consistently shorter than the other digits ( Bartels et al. 2015a). In our Bahamian specimens this difference is not clear (two specimens have digits on legs I–III of similar lengths and in three others digit I is slightly shorter). Dipodarctus subterraneus was originally described in the genus Halechiniscus Richters, 1908 , further described and renamed Hemitanarctus subterraneus by de Zio Grimaldi et al. (1995 /96), and subsequently moved to the genus Dipodarctus (see Jørgensen et al. 2014 for complete history). When the genus Dipodarctus was erected by Pollock (1995), he did not compare the very similar D. anaholiensis to the species then known as Halechiniscus subterraneus , so differentiating characters of these two are minimal. The only two characters clearly identifying D. subterraneus are a small lateral projection just anterior to leg IV and segmented cephalic cirri. These characters are observable in our best specimens, and since the Bahamas is the type locality for this species, we have assigned all our specimens to D. subterraneus . As mentioned by Kaczmarek et al. (2015), D. subterraneus is in need of redescription.

Although the Bahamas is the type locality for D. subterraneus , the species is reported to have a very broad distribution and wide habitat preferences (see Bartels et al. 2015b for interactive map), indicating these reports need to be verified (Kaczmarek et al. 2015).