Polyonyx heok Osawa & Ng, 2016

Osawa, Masayuki, Naruse, Tohru & Ng, Peter K. L., 2018, New records of species of the Polyonyx sinensis group (Crustacea: Decapoda: Anomura: Porcellanidae) from Japan, the Philippines, Singapore, and Malaysia, with descriptions of two new species, Zootaxa 4429 (2), pp. 303-323 : 306-307

Polyonyx heok Osawa & Ng, 2016

( Fig. 1B )

Polyonyx pedalis . — Haig 1964: 381.— Osawa 2007a: 26, fig. 3; 2007b: 37 (not Polyonyx pedalis Nobili, 1906 ).

Polyonyx heok Osawa & Ng, 2016: 506 , figs. 6–8, 15C, D (type locality: Singapore Strait, Pulau Jong , 1°12’54”N 103°47’12”E, 15.4 m).

Material examined. Japan. Iriomote Island, Ryukyu Islands: RUMF-ZC-4395, 1 male (cl 3.7 mm), Nazuni, off

Sonai, Dive 1, 20 m, in tube of Chaetopterus pacificus (RUMF-ZO-23), SCUBA diving, coll. T. Naruse & R. Yoshida, 30 September 2016; RUMF-ZC-4736, 1 ovigerous female (cl 7.6 mm), Nazuni, off Sonai, Dive 2, 20 m, in tube of C. pacificus (RUMF-ZO-24), SCUBA diving, coll. T. Naruse & R. Yoshida, 30 September 2016. Kagoshima Prefecture ( southern Kyushu ): RUMF-ZC-4501, 1 male (cl 9.0 mm), 1 ovigerous female (cl 10.7 mm), Tategamiiwa, Okikojima , Kagoshima (Sakurajima, Kinko Bay ), 19.8 m, in tube of C. pacificus (RUMF-ZO-26), SCUBA diving, coll. R. Yoshida, D. Uyeno, Y. Endo & T. Naruse, 25 October 2016 ; RUMF-ZC-4502, 1 male (cl 9.4 mm), 1 ovigerous female (cl 10.5 mm), Kannonzaki, Kagoshima (Sakurajima, Kinko Bay ), 15 m, in tube of C. pacificus (RUMF-ZO-25), SCUBA diving, coll. R. Yoshida, D. Uyeno, Y. Endo & T. Naruse, 24 October 2016 .

Coloration in life. The coloration of the specimens examined ( Fig. 1B ) agrees well with what was reported by Osawa & Ng (2016).

Distribution. Known from wide area of the western Pacific: Singapore, Indonesia, New Caledonia, Vanuatu, and Japan ( Osawa & Ng 2016). The previous record of P. heok from the Japanese waters was based on a specimen from Okinawa Island, Ryukyu Islands. The present specimens extend the distribution range of the species to the north, Kagoshima in Kyushu, Japan.

Habitat. Occurring on sand and mud; depths of 7–65 m ( Osawa & Ng 2016). The type specimens of P. heok are a heterosexual pair from Singapore and were collected from the tubes of Chaetopterus aff. pacificus Nishi, 2001 , living on sandstones in subtidal reefs ( Osawa & Ng 2016). The specimens examined from Iriomote Island and Kagoshima were obtained from parchment tubes of Chaetopterus pacificus which usually adhere to the underside of rocks partially buried in sand or gravel bottom. These suggest that P. heok probably prefers to live symbiotically with species of Chaetopterus that have their tubes underneath rocks.

Remarks. The present specimens agree well with the original description of P. heok by Osawa & Ng (2016) in all diagnostic aspects. Two heterosexual pairs from Kagoshima (males, cl 9.0, 9.4 mm; ovigerous females, cl 10.5, 10.7 mm; RUMF-ZC-4501, 4502) are the largest known specimens.

Figures

FIGURE 1. Five Polyonyx species. Fresh specimens (A–D, G, H) and preserved specimens (E, F), entire animal, dorsal view. A, Polyonyx boucheti Osawa, 2007, probably female (cl 1.7 mm), Panglao Island, ZRC 2017.204; B, Polyonyx heok, ovigerous female (cl 7.6 mm), Iriomote Island, RUMF-ZC-4736; C, Polyonyx pilosibrachium n. sp., paratype, male (cl 3.1 mm), Iriomote Island, RUMF-ZC-4392; D, Polyonyx pilosibrachium n. sp., paratype, ovigerous female (cl 3.3 mm), Iriomote Island, RUMF- ZC-4389; E, Polyonyx sasekumari n. sp., paratype, male (cl 3.2 mm), Jeram, ZRC 2016.527; F, Polyonyx sasekumari n. sp., paratype, ovigerous female (cl 4.6 mm), Jeram, ZRC 2016.527; G, Polyonyx thai Werding, 2001, male (cl 2.8 mm), Johor Straits, St. DW131, ZRC 2017.202; H, Polyonyx thai Werding, 2001, ovigerous female (cl 3.5 mm), Johor Straits, St. DW131, ZRC 2017.202.