Enoplometopus chacei Kensley & Child, 1980

Chan, Tin-Yam & Fujita, Yoshihisa, 2012, Reef lobsters of the genus Enoplometopus A. Milne-Edwards, 1862 (Crustacea: Decapoda: Nephropidea) from the KUMEJIMA 2009 Expedition in Okinawa, with the second record of the rare species E. chacei Kensley & Child, 1986 *, Zootaxa 3367, pp. 126-133 : 127-130

Enoplometopus chacei Kensley & Child, 1980

( Figs. 1, 2A, B, 3, 4A)

Enoplometopus chacei Kensley & Child, 1980: 520 , figs. 1–2 [type locality: Philippines]. — Chan & Ng, 2008: 354, fig. 5B.

[?] Enoplometopus occientalis . — Kubo, 1952: 97, fig. 3, pl. 6. (not Randall, 1840)

Material examined. Kume Island, Okinawa: Hiyajo , scuba diving, 10 m, 1 Mar. 1992, 1 male (dotted) cl 33.0 mm ( CBM-ZC 6696 ) ; Maenohama , gill net, 10 m, 9 Mar. 1997, 1 male (non-dotted) cl 40.9 mm ( CBM-ZC 6697 ) ; KUMEJIMA 2009stn Dive 15, Ebi-ana , scuba diving, 10 m, 13 Nov. 2009, 1 female (dotted) cl 35.5 mm ( NTOU M00995 ) , 1 female (non-dotted) cl 35.3 mm ( NTOU M00994 ) ; KUMEJIMA 2009 stn Dive 28, Oyako-iwa , scuba diving,> 20 m, 17 Nov. 2009, 1 male (dotted) cl 31.3 mm ( NTOU M00993 ) ; Tokujimu , scuba diving, 6 Dec. 2010, 1 male (dotted) cl 32.4 mm (RUMF-ZC-01323), 1 female (non-dotted) cl 25.1 mm (RUMF-ZC-01324) .

Philippines, Batan Island , hand net, 2 m, 8 Jun. 1985, holotype male cl 36.7 mm ( NMCR) .

Diagnosis. Size moderately large (up to 40.9 mm cl). Carapace with 3 lateral, 2 intermediate, 4 median (sometimes also bearing 1 minute anterior tubercle) and 1 postcervial teeth. Postcervical tooth small but distinct, with tip well separated from carapace. Rostrum distinctly or just overreaching antennal peduncle, with 2–3 lateral teeth. Ischium of maxilliped III lacking distoventral spine. Large chelae with surface sharply granular; outer margin of fixed finger more or less spinose while that of movable finger only bearing distal spines; dorsal hinge of fingers with 1 distinct spine; ventral surface with posterior margin bearing 1 distinct spine (more often) or large tubercle at medial part near hinge between chela and carpus; merus with entire or distal 3/4 dorsal margin spinose. Abdominal pleura terminated in sharp angles but posterior margin not notched. Posterior margin of abdominal tergite VI lacking distinct spines. Telson with 1 pair of lateral spines.

Colouration. Body generally orange-red, with tips of spines and teeth whitish. Carapace with lateral surface either uniformly orange-red or covered with numerous red dots at ventral 1/3–2/3; but margins of carapace always alternated with red and white marks, with branchiostegal angle purplish red and followed by a large white spot along carapace margin; posterodorsal surface behind postcervical tooth also always covered with red dots. Antennular and antennal flagella uniformly orange-red. Lateral part of basicerite whitish. Eyes dark brown. Large chelipeds generally orange-red except dorsodistal parts of carpus and merus reddish; fingers of chela covered with 2 somewhat redder bands in males. Pereiopods II to V uniformly orange. Abdomen uniformly orange-red to more or less covered with red dots, but posterior margins of somites always alternated with red and white marks; lateral part of tergite I and pleuron I reddish and with a large white spot; ventral parts of pleura II to V also reddish with large white spots. Abdominal somite VI and tailfan uniformly orange-red, only with movable lobe at exopod of uropod bearing a large lateral dark purplish spot.

Distribution. The Philippines and Okinawa, perhaps also in Japan mainland (see Remarks), at depths of 2 to about 20 m.

Remarks. The present material from Okinawa agrees very well with the holotype from the Philippines in every diagnostic character. The postcervical tooth is damaged in the holotype and with the tip eroded. Nevertheless, the size and shape of the base of the postercervical tooth is identical between the holotype and the Okinawa material. The only obvious difference is that three specimens (1 male and 2 females; CBM ZC6696, NTOU M00994 , NTOU M00995 ) have three lateral teeth on the right side of the rostrum ( Fig. 1B). Thus, the number of lateral rostral teeth proposed by Chan & Ng (2008) to distinguish E. chacei from the closely related E. debelius and E. daumi becomes rather unreliable. Nonetheless, the length of the rostrum is always greater in E. chacei . Of the eight specimens known for this species, six have the rostrum distinctly overreaching the antennal peduncle ( Fig. 1G). Only two specimens (NTOU M00994 and RUMF-ZC-01324) have the rostrum just exceeded the antennal peduncle ( Fig. 1A). The rostrum of E. debelius is always distinctly shorter than the antennal peduncle. In E. daumi , the rostrum is often shorter than the antennal peduncle and rarely almost extending to the tip of the antennal peduncle. With more specimens of E. chacei available, one more character is found to be useful to separate the present species from E. debelius and E. daumi . At the posterior margin of the ventral surface of the large chela, there is a distinct spine, or infrequently a large tubercle, located at the medial part of the margin near the hinge between the chela and carpus in E. chacei ( Fig. 2A, B). In E. debelius and E. daumi , there is no distinct spine at the posterior margin of the ventral chela and at most only some small tubercles may be present at this part ( Fig. 2C, D). Furthermore, the size seems to be useful to separate E. chacei from E. debelius and E. daumi . Available specimens and information shows that E. debelius and E. daumi are smaller than cl 26 mm (including ovigerous females, see Chan & Ng 2008; Holthuis 1983) but E. chacei can reach to cl 40.9 mm.

All the present Okinawa specimens are accompanied with colour photographs and make known the actual colour pattern of E. chacei . Nevertheless, the Okinawa material showed two rather different colour patterns; one form with the carapace and abdomen more or less distributed with red dots ( Fig. 3 A–D), while the other form completely lacking red dots on the lateral carapace and abdomen ( Figs. 3E, F, 4A). The “dotted” (3 males and 1 females cl 32.4–35.5 mm) and “non-dotted” (1 male and 2 females 25.1–40.9 mm) colour patterns are not related to size and sex, nor the number of lateral teeth on the rostrum (both sides 2 lateral teeth—2 “dotted” and 2 “nondotted” specimens, Fig. 1H; one side 2 and other side 3 lateral teeth—2 “dotted” and 1 “non-dotted” specimens, Fig. 1B). Furthermore, in the dotted form the red dots can be rather few or restricted to the lower carapace and dorsal abdomen (RUMF-ZC-01323 and NTOU M00993 ; Fig. 3A), distributed over the entire carapace and abdomen (CBM ZC 6696, Fig. 3D) or in-between these two extremes (NTOU M00995 , Fig. 3B, C). From the original description and drawing provided by Kensley & Child (1986: 524, fig. 1), the holotype of E. chacei should belong to the fewer “dotted” form like the NTOU M00993 specimen ( Fig. 3A). A comparison of partial COI sequence (658 bp) between the dotted (GenBank accession no. JF331659 ) and non-dotted (GenBank accession no. JF331660 ) forms shows that they have only 0.2% genetic divergence; confirming that they belong to the same species. The COI sequence divergence between E. chacei and E. debelius (GenBank accession no. JF331661 )/ E. daumi (GenBank accession no. JF331662 ) is 8.8–10.1%, while that between E. debelius and E. daumi is 4.1%. Although it is now confirmed that E. chacei has a colouration very different from E. debelius and E. daumi , the “dotted” form has a colour pattern somewhat similar to E. debelius . Enoplometopus debelius is characteristic in having the carapace and abdomen densely covered with dots (see Allen & Steene 1994; Debelius 1986, 1999; Debelius & Baensch 1994; Gosliner et al. 1996; Holthuis 1983; Hoover 1998; Poupin & Juncker 2010). However, the body of E. debelius is whitish and the dots are purplish. In the “dotted” form of E. chacei the body is orange-red and the dots are reddish, and therefore, the dots are rather indistinct and not that striking as in E. debelius . Thus, E. chacei can be easily distinguished from E. debelius by colouration. Nevertheless, the “ E. occidentalis ” specimen (male cl 23 mm) reported by Kubo (1952) from Wakayama in Japanese mainland seems to have a colour pattern inbetween E. debelius and E. chacei . The black and white photograph provided by Kubo (1952: pl. 6) showed a dotted pattern more similar to that of E. debelius . However, Kubo (1952: 99) described the colouration of the Wakayama specimen as “All body and appendages are stained with light whitish chrome orange colour. Body marked with many spots of rather deep chrome orange colour. The spots measure about 2 mm in diameter, those of both sides of body are defined more clearly than those found on the other parts of the body...”. Thus, Kubo’s (1952) colour description fits better the “dotted” form of E. chacei . Unfortunately, the whereabouts of Kubo’s (1952) specimen is now not known ( Usami & Watanabe 2010). From the rather unclear photographs provided by Kubo (1952: pl. VI), the rostrum of the Wakayama specimen seems to be rather slender and longer than the antennal peduncle, and thus likely represents E. chacei instead of E. debelius .

Enoplometopus chacei has been previously thought to be very rare but seven specimens are now reported from the Kume Island. From local divers and fishermen in Kume Island, this species is not very rare there though it is mostly found in caves. The species E. crosnieri Chan & Yu, 1998 was also thought to be rather rare but recently many specimens were found from a wide range of localities ( Chan & Ng 2008; Poupin 2003) including Japan ( Nomura 2003). It is likely that E. chacei is not that rare when its habitat is better known (see also Mendoza et al. 2010). Enoplometopus chacei is a new record from Japan and the standard Japanese name for this species is given as Kumi-shogun-ebi.