Scotothuria herringi Hansen, 1978

Scotothuria herringi Hansen, 1978 View in CoL

Scotothuria herringi Hansen, 1978: 34–37 View in CoL , figs 1–9.— Billett et al., 1985: 406–407, fig. 5.— Miller and Pawson, 1990: 4.— Gebruk et al, 2014: 169.

Material examined. NMV F308231 About NMV * (1) [IN 2022 V08 122] ; NMV F308338 About NMV * (1), [IN 2022 V08 196] .

Diagnosis of IOT material. Deep violet to almost black specimens, soft and gelatinous with few features remaining other than some partly fused and some free podia giving a shaggy appearance. Spongey when preserved, some lumps at one end of NMV F308338 About NMV that may have been a damaged mouth, exposed gut, and flat longitudinal muscles. No additional external features observed in these specimens, but type description includes ~18 retractile dendritic tentacles and body surrounded by lateral brim of partially fused to wholly embedded podia, plus some minute posterior midventral tube feet. IOT specimens small and damaged, ~ 72 mm long and 26 mm wide ( NMV F308338 About NMV , pre-preservation) to ~ 95 mm long and 55 mm wide ( NMV F308231 About NMV , pre-preservation). The larger specimen shrank to ~ 60 mm long on preservation. Dense with distinctive cross-like table ossicles with four arched arms and single tall central spire terminating in palm-tree or umbrella-like hood of downward projecting hooks, some apophyses with pointed tip projecting above this. Umbrella-like hooked structures sometimes also present at further intervals along spire or replaced by rings of reduced spines. Arms also have regularly spaced rings of spines. Apophyses and arms otherwise smooth. Ossicle arm width and spire height are variable (fig. 49c–h). Second type of ossicle very irregular rods, crosses, and Ys (typically ~90–130 μm long), covered by rings of spines and terminating in thickened spinous ends (fig. 49i, k, l). One specimen ( NMV F308231 About NMV ) also has perforated plates, a feature not previously reported for this species. Considering the state of the specimens these might be contaminants, but the sample has at least five plates, of variable shape and size (~520–1000 μm wide). Shape, number, and size of perforations were also variable, and there were some weak initial indications of secondary layering (fig. 49j) .

Remarks. Specimens with few remaining external characters and distinguished almost entirely based on their distinctive ossicle form. While illustrations provided by Hansen (1975) and subsequent images provided by Bohn (2006) of Psychropotes semperiana Théel, 1882 have a similar downward hook-shaped cap to their cross-like ossicles, P. semperiana ossicles are much more spinous and robust, and lack the curved arms and additional circles of hooks present in Scotothuria herringi Hansen, 1978 , along with the additional irregular rods, crosses, and Ys noted above.

One specimen ( NMV F308338) was from a station with magnesium nodules, which may have led to its slightly darker colour, but both specimens were dark violet to black. Specimens were similar in size to the range given for the types for Scotothuria herringi Hansen, 1978 , which were 55–85 mm long pre-preservation, shrinking to 48–80 mm after ( Hansen, 1978). A larger specimen from a subsequent collection was 150 mm pre-preservation, shrinking to 70 mm after (Billet et al., 1985).

SolÍs-MarÍn (2003) suggested that similarities with ossicles from Galatheathuria aspera ( Théel, 1886a) might indicate S. herringi is a juvenile of that species, but more taxonomic work is required. Billet et al. (1985) and Miller and Pawson (1990) note that Scotothuria herringi Hansen, 1978 is a possible synonym of Dendrothuria similis ( Koehler and Vaney, 1905) , but more material from the type localities would be required before any decision on synonymy. Because the distinct “umbrella-hook” apophyses were not described in D. similis , we have placed our specimens in S. herring for now, with ossicles being a perfect match for the type material and subsequent work by Billet et al. (1985). While no comparative genetic sequences for Scotothuria were available, the sequences for both Scotothuria examined in this study comprise a well-supported monophyly and form a clade with Paelopatides (fig. S5).

Distribution. Eastern Atlantic and Indian Oceans.

Full bathymetric range. 1250–5414 m (IOT 1874–5414 m).

Type locality. North Atlantic Ocean (west of Ireland), collected at 1250–1500 m (station depth 5161 m) .

This species not previously recorded from Australia in AFD or ALA (January 2024) .

This IOT material represents a geographic and bathymetric range extension for the genus and species, previously with multiple records from the East Atlantic but only a single record from the Indian Ocean off Kenya at 1250–4980 m ( Gebruk et al., 2014).

References. AFD (2024), ALA (2024), Billet et al. (1985), Bohn (2006), Gebruk et al. (2014), Hansen (1978), Koehler and Vaney (1905), Miller and Pawson (1990), SolÍs-MarÍn (2003).