Thyone susamiensis, Yamana & Hirai & Hirashima, 2015

Yamana, Yusuke, Hirai, Atsushi & Hirashima, Kentarou, 2015, A New Species of Thyone (Echinodermata: Holothuroidea: Dendrochirotida: Phyllophoridae) from Wakayama, Japan, Species Diversity 20, pp. 141-151 : 142-146

publication ID	https://doi.org/ 10.12782/sd.20.2.141
publication LSID	lsid:zoobank.org:pub:78DD2363-D706-40C8-9F7D-2C9F2E116D55
persistent identifier	https://treatment.plazi.org/id/E8F04428-C432-4E1B-98D4-87E9153B335C
taxon LSID	lsid:zoobank.org:act:E8F04428-C432-4E1B-98D4-87E9153B335C
treatment provided by	Felipe
scientific name	Thyone susamiensis
status	sp. nov.

Treatment

Thyone susamiensis View in CoL sp. nov.

( Figs 1–7 View Fig View Fig View Fig View Fig View Fig View Fig View Fig )

Material examined. Holotype, WMNH-2014-INV-2 (anaesthetized; length 127 mm, width 20 mm). Paratypes: WMNH-2014-INV-1 (anaesthetized; length 111 mm, width 17 mm); WMNH-2014-INV-3 (anaesthetized; length 121 mm, width 19 mm); WMNH-2014-INV-4 (anaesthetized; length 94 mm, width 18 mm); WMNH-2014-INV-5 (anaesthetized; length 74 mm, width 8 mm); WMNH- 2014-INV-6 (unanaesthetized; length 54 mm, width 22 mm); WMNH-2014-INV-7 (unanaesthetized; length 51 mm, width 9 mm); WMNH-2014-INV-8 (unanaesthetized; length 71 mm, width 23 mm); WMNH-2014-INV-9 (unanaesthetized; length 58 mm, width 25 mm); WMNH- 2014-INV-10 (unanaesthetized; length 65 mm, width 22 mm). All specimens from type locality; collection details given in Materials and Methods section above.

Description. Appearance of anaesthetized specimens not drastically altered by fixation. General colour of specimens also not seriously affected by fixation/preservation ( Fig. 1A–C View Fig ). Body slightly curved or U-shaped, with both ends tapered and turned upwards; body wall soft and thin. Body whitish-yellow or cream, with blackish-purple marbling. Anterior and posterior ends with blackish-purple pigmentation in most specimens.

Tentacles arranged in single circle; two tentacles on ventral side smaller ( Fig. 2A View Fig ). Colour of tentacles and introvert whitish-yellow or cream, and generally pigmented with brown or blackish-purple markings, occasionally variegated. Tentacle tips (nodules) tinged with brown or blackish-purple. Short processes present, surrounding entrance of oesophagus.

Non-retractile pedicels covering entire body at constant density. On each side of narrow longitudinal muscles, pedicels forming ambiguous, contiguous row. Pedicels generally paler than adjacent body. Pedicels becoming gradually smaller anterior and posterior to those in middle portion of body, absent in introvert region ( Fig. 1B–D View Fig , Table 1). Pedicels blackish-purple on both ends of body in most speci-

Size of calcareous ring element in

Type Body Gonad

Body size abdominal-lateral side (mm) Counts

No.

a statusb statec stated Tentacles

Length Width Length Width Length Width Body Introvert papillae scale canals vesicles 1 p a t 111 17 15.4 1.4 9.5 1.4>150 0 10 10 7 1 1

2 h a t 127 20 21.3 1.4 13.7 1.4>180 0 10 10 5 1 1

3 p a o 121 19 17.4 1.3 11.5 1.3>190 0 10 10 5 1 1

4 p a o 94 18 16.5 1.6 8.5 1.5>170 0 10 10 5 1 1

5 p a i 74 8 13.8 1.4 6.1 1.1>120 0 12 7 3 1 1

6 p u o 54 22 18.2 1.6 10.2 1.0? 0 10 10 5 1 1

7 p u i 51 9 13.4 1.0 6.0 1.0? 0 10 10 5 1 1

8 p u o 71 23 16.7 1.4 9.7 1.9? 0 10 10 5 2 1

9 p u o 58 25 18.5 1.5 9.8 1.2? 0 10 10 5 1 1

10 p u t 65 22 21.2 1.7 9.4 1.5? 0 10 10 5 2 1

a Registration No. Wakayama Prefectural Museum of Natural History , Invertebrate Collection of 2014 (WMNH-2014-INV-) . b p: paratype, h: holotype. c a: anaesthetized, u: unanaesthetized. d i: immature, o: ovarium, t: testis. e Number of pedicels in a row along to longitudinal muscle in abdominal side.

mens.

Ten anal papillae and five anal scales in most radii (five pairs of anal papillae in outer circle and five anal scales in inner circle; Fig. 2B View Fig , Table 1), generally pigmented brown or blackish-purple. Each anal scale containing a long calcareous structure. Base of anal scale connected to thin calcareous plate forming delicate calcareous ring surrounding anal region.

Tubular composite calcareous ring present, encircling oesophagus. Pieces of radial and inter-radial elements forming mosaic pattern (i.e., not lined up). Radial elements bifurcate posteriorly, approximately twice as long as inter-radials, posterior forks of radial elements starting posterior to ends of adjacent inter-radial elements ( Fig. 3A, B View Fig , Table 1). Radials and inter-radials with sharp anterior projections; some projections on radials bifid at tip; anterior first piece of each radial and inter-radial element broad, pieces after that narrow, and usually aligned roughly in one to three (mostly two) longitudinal row. Most specimens (n =8, including holotype) with one Polian vesicle and one stone canal ( Table 1). Tubules of gonads unbranched.

Two types of ossicles found in tentacles, viz., ‘rosettes’ and ‘rods’, as well as full series of intermediate forms; these ossicles, irrespective of form, with mean length and mean central width 61–78 µm and 17–20 µm (depending on specimen), respectively ( Fig. 4A, B View Fig , Table 2). Ossicle size not significantly different among three specimens examined (Kruskal-Wallis test, P s>0.05).

Two types of ossicles found in peri-oral skin: 1) ‘rosettes’, with mean length and mean central width 32–35µm and 19–21 µm (depending on specimen), respectively; size not significantly different among three specimens examined (Kruskal-Wallis test, P s>0.05); and 2) ‘tables’ with short spires and large discs, spires with two pillars and zero to two cross-beam connections, discs chiefly oval. Mean length and mean central width of discs 64–70 µm and 39–57 µm (depending on specimen), respectively ( Fig. 5A, B View Fig , Table 3); number of perforations in each disc 8–40, with mean of 18–27 holes (depending on specimen). Statistical analysis not applied to this type of ossicle, due to their very low frequency of occurrence.

Single type of ossicle (viz., ‘small rosettes’) found in processes of oesophagus, mean length and mean central width 22–25 µm and 9–12 µm (depending on specimen), respectively ( Fig. 5A, B View Fig , Table 3). Measurements not different significantly among three examined specimens (Kruskal-Wallis test, P s>0.05).

Single type of ossicle (viz., ‘rosettes’) found in introvert throughout its anterior, middle, and posterior parts; mean length and mean central width 31–39 µm and 21–27 µm (depending on specimen), respectively ( Fig. 5A, B View Fig , Table 3). These sizes not differing significantly among the three parts and three examined specimens (Kruskal-Wallis test, P s>0.05). Ossicles in posterior part not dense.

Integument of body wall lacking ossicles throughout anterior, middle, and posterior parts, on both abdominal and dorsal sides.

Pedicels displaying only one type of ossicle (viz., ‘endplates’). In middle part of abdominal side, diameter of endplates 117–195 µm (mean 149–180µm, depending on specimen) and approximately 47–144 holes (mean 81–123, depending on specimen) ( Fig. 6A, B View Fig , Table 4). Diameter of endplates significantly different among three specimens (Kruskal-Wallis test, P <0.01), smaller in smaller specimens. Approximately three different forms of hole arranged in three concentric areas on each endplate, viz., latitudinally elongated holes near rim, longitudinally elongated holes in mid region, and almost circular holes in central area.

Body-wall around anus lacking ossicles, except for fragments of calcareous plates surrounding anal region. Usually, anal appendages with one type of ossicle (viz., ‘rods’) in anal papillae ( Fig. 7A, B View Fig , Table 5), mean length and mean central width 91–96 µm and 4.4–6.3 µm (depending on specimen), respectively, not significantly different in size among three examined specimens (Kruskal-Wallis test, P s>0.05). Only one of these three specimens displaying, in low frequency, another type of ossicle (viz., ‘rosettes’) in anal appendages, with mean length of 39 µm and mean central width of 23 µm ( Fig. 7B View Fig , Table 5).

Distribution. So far known only from type locality.

Ecology. At the type locality, individuals of Thyone susamiensis were found burrowing in sand and pebbles that filled up spaces between boulders, often spreading their tentacles into the water (at least at night). We collected the following other species of sea cucumber nearby: Holothuria (Lessonothuria) pardalis Selenka, 1867 ; H. (Mertensiothuria) leucospilota Brandt, 1835 ; H. ( Platyperona ) sp.; Afrocucumis africana (Semper, 1867) ; Lipotrapeza sp. ; Polycheira sp. ; and Chiridota sp.

Etymology. The specific name susamiensis is an adjective, derived from the type locality, Susami town.