Chiridota rigida Semper 1867
Creators: name: Yamana, Yusuke
name: Tanaka, Hayato
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Apodida
Chiridotidae
Chiridota
Chiridota rigida

description: Chiridota rigida Semper, 1867
Figures 1, 2
Material examined. 6 specimens: WMNH-INV- 2014-36 (length 32.6 mm, width 4.1 mm); WMNH-INV- 2017-25 (anterior half only: length 22.9 mm, width 4.3 mm); WMNH-INV- 2017-26 (anterior half only: length 12.6 mm, width 2.4 mm); WMNH-INV- 2017- 38 (anterior half only: length 17.4 mm, width 2.4 mm); WMNH-INV- 2017-39 (length 26.9 mm, width 3.3 mm); WMNH-INV- 2017-40 (length 44.1 mm, width 4.2 mm).
Description. Body medium, cylindrical, length of largest specimen: 44.1 mm (Table 1). Body colour, faint reddish brown or faint yellow in preserved specimens (Fig. 1A), red or reddish brown in living specimens (Fig. 1B). Mouth anterior; anus posterior. Oral disc slightly inclined toward ventral side. Wheel-papillae, dense in dorsal, sparse in ventral, hemispherical shape, diameter approximately 0.3–1.2 mm, dense in inter-radius, sparse in radius, colour white (preserved and living specimens). Contents of wheel-papillae forming a normal hemispherical structure (Fig. 1C).
Polian vesicle 6–10 (Fig. 1D, Table 1), 1–3 long and others short. Stone canal single, long and thick. Madreporite long and thin, madreporite tip adhered with dorsal body wall. Each 4–5 reproductive tubules in both sides of dorsal mesentery, immature. Intestine has normal two loops. Ciliated funnels situated along mid-dorsal and left lateral mesentery, through anterior to posterior. Ciliated funnels mostly isolated, sometimes grouped, not gathered to make a stalked cluster.
Twelve tentacles, non-retractile, each with 3–6 pairs of digits (frequently unpaired digit present), distal pair largest (Fig. 1D, Table 1). Sensory cup absent. Colour of tentacles white (preserved and living specimens). Calcareous ring composed of five radial and seven inter-radial plates, in which two inter-radial plates continuously presented in dorsal lateral side (Fig. 2A). Both radial and inter-radial plates with slight posterior depression, plates on ventral side larger than that on dorsal side. Radial plate with a complete perforation in dorsal side, however, only a notch or incomplete perforation in ventral side
Tentacles containing curved rod ossicles, length 24–68 µm (means of 46–47 µm in different specimens), width 2–6 µm (means 4 µm), with spinous processes and many branches, frequently straight and lacking processes (Fig. 2B, Table 2).
Registration a Coll. date Body size (mm) Counts
Tentacles Tentacle Stone Polian Length Width digits canal vesicles
Chiridota rigida Semper, 1867
WMNH-INV- 2014-36 Jan. 29, 2014 32.6 4.1 12 8– 10 1 9 WMNH-INV-2017-25 Dec. 15, 2016 22.9b 4.3 12 8– 10 1 9 WMNH-INV-2017-26 Dec. 15, 2016 12.6b 2.4 12 6–8 1 7 WMNH-INV- 2017-38 Jan. 13, 2017 17.4b 2.4 11 6–8 1 6 WMNH-INV- 2017-39 Jan. 13, 2017 26.9 3.3 12 10–12 1 10 WMNH-INV- 2017-40 Jan. 13, 2017 44.1 4.2 12 9–11 1 10 C. impatiens sp. nov.
WMNH-INV- 2016-56 Feb. 11, 2016 66.5 4.1 12 8– 14 1 4 WMNH-INV- 2016-57 Feb. 11, 2016 58.8 5.7 12 9– 14 1 5 a WMNH-INV: Invertebrate Collection of the Wakayama Prefectural Museum of Natural History b The length measured from anterior half only
Chiridota rigida
! " # n $ % & n $ % " n ’ (#) * +, %, %, %, %, %, %, %
(­./(0.12 3.4
5 46 3 2 4 2 6 2 2
137 17
8 1 42 3 3 2 3 3 42 2 1 1 19 96 3 1 1 2 1 4 12 6 1 14746 479 12743 7 1
(­./(0.12.46
5 49 3 2 4 6 2 9 2 2
4 7 3 47
8 44 6 4 4 4 2 9 11 6 9 1 2 13 1 6 1 1 12 6 1 732 479 9742 37 2 347 67 713
: 4 6 4 4 2 3 4 1 2 1 6 1 2 1 6 9 3 2 1 4 11 1 1 9 13732 473 1 742 7 3 3 7 23 27 716
8 44 44 1 4 9 3 2 3 6 13 6 4 9 9
14732 479 12742 7
: 19 44 2 4 4 3 1 2 1 1 4 1 6
1 74 479 74 47 2 ……continued on the next page
! " #
n $ % & n $ % " n ’ (#)
* +
, %, %, %, %, %, %, % (­./(0.12.32
5 46 3 4 6 4 2 4 2 2
1 7 473
8 4 2 1 6 4 6 2 4 1 1 2 4 6 1 2 1 9 1 4 4 1 2 11 6 3 4173 479 12744 37 2 39762 27 1 71: 1 49 3 1 3 2 2 4 1 6 1 9 1 1 3 3 3 4 2 11 1 4273 479 1174 7 4 3 7 4 2712 6719
8 4 41 4 4 9 4 6 2 4 4 1 3 1 1
1474 479 12743 976
: 4 41 3 9 3 2 2 3 1 1 3 3
11732 479 731 7 1
(­./(0; / # " * <: (­ <)) = *) <
) = %
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Body wall containing curved rod, flattened rod, however wheel ossicles only in wheel papillae (Figs 2C, D, Table 2). Curved rod ossicles, mostly present in body wall, distally spreading with low number of processes, and also rarely having one or two branches. Curved rod ossicles, length 23–40 µm (means 30–33 µm) and width 3–5 µm (means 4 µm) in anterior ventral side, length 21–41 µm (means 31–36 µm) and width 3–5 µm (means 4 µm) in anterior dorsal side, length 22–40 µm (means 31–33 µm) and width 3–5 µm (means 4 µm) in posterior ventral side, length 24–47 µm (means 32–36 µm) and width 3–5 µm (means 4 µm) in posterior dorsal side (Table 2). Flattened rod ossicles, mostly present along longitudinal muscle and along mesentery, elongated peanut shape, flat surface, without spine. Flattened rod ossicles, length 20–35 µm (means 25–32 µm) and width 5–13 µm (means 7–10 µm) in anterior ventral side, length 15–43 µm (means 23–30 µm) and width 4–12 µm (means 7–9 µm) in anterior dorsal side, length 11–42 µm (means 26–27 µm) and width 3–12 µm (means 7–10 µm) in posterior ventral side, length 21–35 µm (means 26–27 µm) and width 5–14 µm (means 8–9 µm) in posterior dorsal side (Table 2).
Wheel ossicles round-hexagonal form with six spokes (Fig. 2C). Inner margin of rim mostly parallel to outer margin. Large sized wheel ossicles (that present in basal part of papillae) rarely incomplete, lacking teeth and having under-grown rim and spoke. Teeth of inner margin of rim increased in size at corners, sharp triangular form, 6–20 per radiant (means of 12–14 in different specimens). In anterior dorsal side, complete form of wheel ossicles, diameter 39–90 µm (means 59–66 µm), with 6–18 teeth per radiant (means 12–13), and spoke width composing 17–26% of diameter (means 21–23%) (Table 2). In posterior dorsal side, complete form of wheel ossicles, diameter 46–113 µm (means 67–78 µm), with 10–20 teeth per radiant (means 13–14), and spoke width composing 18–29% of diameter (means 22%) (Table 2).
Distribution. Bohol Island (Semper 1867), South coast of China (Liao & Clark 1995), Taiwan Island (Chao 1998), Guam Island (Miller et al. 2017). In sandy-sediments (depth of approximately 5–15 cm from surface) in the intertidal zone, Susami Town, Wakayama, western Japan.
Ecology. At the present locality. We collected the following other species of sea cucumber nearby: Afrocucumis africana (Semper, 1867); Holothuria (Lessonothuria) pardalis Selenka, 1867; H. (Mertensiothuria) leucospilota Brandt, 1835; H. (Platyperona) sp.; H. (Thymiosycia) arenicola Semper, 1867; Phyrella sp.; Polycheira sp.; Pseudocnus pawsoni Won & Rho, 1998; Thyone susamiensis Yamana et al., 2015.
DNA barcode sequence. The 819bp sequence of the mitochondrial CO1 gene was obtained from a specimen (WMNH-INV- 2017-40, GenBank accession number LC 271193). Base frequency was A=18.3%, C=18.8%, G=23.4%, T=39.4%. The CO 1 sequence showed the highest similarity to that of Chiridota rigida from Guam (accession no. KX874401, Miller et al. 2017), i.e., the identity is 99% (655/656 bp).
description: Published as part of Yamana, Yusuke & Tanaka, Hayato, 2017, A new species of Chiridota (Echinodermata: Holothuroidea: Apodida: Chiridotidae) from Japan, and First record of C. rigida from Japan, pp. 243-257 in Zootaxa 4341 (2) on pages 245-250, DOI: 10.11646/zootaxa.4341.2.4, http://zenodo.org/record/1039472