Polycheles amemiyai Yokoya, 1933

Ahyong, Shane T. & Chan, Tin-Yam, 2004, Polychelid Lobsters Of Taiwan (Decapoda: Polychelidae), Raffles Bulletin of Zoology 52 (1), pp. 171-182 : 173-176

Polycheles amemiyai Yokoya, 1933

( Figs. 2 , 4C )

Polycheles amemiyai Yokoya, 1933: 44-45 , Fig. 23 [type locality: Bungo Strait , Japan].

Stereomastis nana - Baba et al., 1986, pl. 109 [not S. nana ( Smith, 1880) ].

Polycheles enthrix - Chan & Yu, 1993: 107; Galil, 2000: 322-325 [part] [not P. enthrix ( Bate, 1878) ].

Material examined. – Taio-Yu-Tai, N Taiwan: 1 ovigerous female (cl. 50.5 mm), ( NTOU), commercial trawler, coll. C. W. Lin, 10 Jun.2001 . Tai-Shi fishing port, I-Lan County, NE Taiwan: 1 male (cl. 45.2 mm), ( NTOU), commercial trawler, 28 May.1998 ; 1 ovigerous female (cl. 63.4 mm), ( NTOU), commercial trawler, 6 Jun.1998 ; 1 female (cl. 53.2 mm), ( NTOU), commercial trawler, 27 Sep.2002 ; 1 male (cl. 49.1 mm), ( ZRC 2001.0126 ) , commercial trawler, coll. P. Ng. Nangfangao fishing port, I-Lan County, NE Taiwan: 2 females (cl. 21.3-25.3 mm), ( NTOU), commercial trawler, 10 Apr.1991 . SW Taiwan: 1 female (cl. 25.4 mm), ( NTOU), 22º11.40’N, 120º22.58’E, 452- 280 m, TAIWAN 2001 CD140, 23 Nov.2001 .

Diagnosis. – Carapace with two rostral spines and a single spine midway between rostral spines and spine on inner orbital margin. Outer proximal margin of basal antennular segment with 2 spines. Gastric region of carapace with 1 or 2 spines of similar size to spines of median carina; branchial carinae obsolete; branchial groove without spines; postcervical groove with antrorse spine on posterior margin between median carina and branchial carina. Median carina of abdominal tergites 1-4 entire, with short antrorse tooth on tergites 1-3 or 4, each without posterior upright tooth. Abdominal tergites 2-5 relatively smooth, without distinct oblique grooves. Pereopod 1 merus with dorsal and ventral margins minutely and sparsely spinulate.

Description. – Carapace subrectangular, margins slightly convergent proximally; dorsal surface sparsely setose, faintly punctate; gastric region at most with single spine of similar size to median spines, and occasionally with scattered, minute spinules; lateral surface with row of setae along lateral carina; frontal margin broadly curved, with two rostral spines, and a single spine midway between rostral spines and spine on inner orbital margin; lower anterior margin with 2 small spines adjacent to antennal protopod. Median submarginal tooth short, inconspicuous. Dorsal orbital sinus broadly triangular; outer angle of orbital sinus produced anteriorly, margin unarmed. Lateral margins of carapace with evenly graded spines, slightly decreasing in size posteriorly; spine formula 7-10: 4-5: 12-18. Cervical and postcervical incisions with smooth margins. Postcervical groove unarmed. Median postrostral carina prominent, spine formula 1,1,1-2:0-1. Median postcervical carina prominent, irregular, spine formula 2, 0-2. Postorbital carina ill-defined. Branchial carina sinuous, indicated by row of well-spaced tubercles. Branchial groove unarmed. Dorsal posterior border of carapace smooth, with 2 pairs of antrorse spines.

Abdominal tergites smooth, punctate, mesially carinate; dorsum without oblique grooves. Anterior margin of tergite 1 with short antrorse median tooth and small sublateral spine. Tergites 2-3 or 4 with short antrorse median tooth, shorter and blunter posteriorly. Tergite 5 with blunt median carina; tergite 6 with short median carina posteriorly. Pleuron 2 pointed anteriorly; surface smooth; margins setose but not granulate or denticulate; lower margin faintly concave. Telson with low, obsolete proximal swelling; without granules. Pleura 3-6 becoming narrower posteriorly; margins smooth, without denticles or tubercles. Uropodal protopod without tubercles or granules; endopod with blunt mid-rib, surface slightly irregular; exopod with median sulcus, surface slightly wrinkled.

Eyestalk with small dorsal conical tooth.

Basal antennular segment produced anteriorly to a sharp point, mesial margin with 8-12 teeth, apex extending beyond distal segment of antennular peduncle; outer proximal margin rounded, with two spines of which the distal most is largest. Distal segment of antennular peduncle with blunt inner tooth.

Distal and proximal segments of antennal peduncle with stout inner distal spine; scaphocerite lanceolate, not extending anteriorly beyond distal segment.

Maxilliped 3 epipod rudimentary, about 0.21-0.26 ischium length.

Pereopod 1 about as long as body. Merus with curved spine on dorsal distal margin; dorsal and ventral margins minutely and sparsely spinulate, with spines on lower margin more numerous. Carpus nearly as long as merus; adults with 2 rows of irregular spinules on distodorsal surface; ventral surface smooth, distally with spinule and blunt projection mesially. Dactylus about as long as palm; palm minutely spinulate along upper and ventral margins, bearing distolateral spine as well as blunt projection.

Pereopod 2 with ischium and basis fused; ischiobasis articulating with merus; merus and ischiobasis unarmed; carpus with dorsodistal spine; propodus dorsally cristate; dactylus and pollex with curved apices, opposable margins pectinate.

Pereopods 3-5 with merus and ischium fused, articulating with basis. Pereopod 5 in males with pollex about one-quarter length of dactylus; adult females with pollex and dactylus of equal length.

Pleopod 1 uniramous, forming copulatory organ, comprising distal and proximal segments; proximal segment (basis) shorter than distal segment, outer margin setose; distal elongate, spatulate, with appendix interna on inner subdistal margin; inner proximal margin sparsely setose.

Colour in life. – Body and limbs orange-pink in large adults and somewhat pink-red in smaller specimens. Carapace grooves, median carina and lateral spines whitish. Abdominal tergites 2-5 with pair of submedian white patches near anterior margin. Base of uropodal protopod whitish. Eggs bright orange.

Remarks. – In revising the Polychelidae, Galil (2000) synonymised P. amemiyai Yokoya, 1933 , from Japan, and P. kermadecensis ( Sund, 1920) , from the Kermadec Islands, with P. enthrix Bate, 1888 . Although the three nominal species closely resemble each other, P. kermadecensis was recently shown to be distinct from P. enthrix (see Ahyong & Brown, 2002). Similiarly, on the basis of the present study, we believe that P. amemiyai should also be removed from the synonymy of P. enthrix .

Galil (2000) identified Japanese material reported by Baba et al. (1986) (under Stereomastis nana ) and Taiwanese material reported by Chan & Yu (1993) (under Polycheles enthrix ) as P. enthrix . Comparison of P. enthrix sensu stricto with Taiwanese specimens and the account of Baba et al. (1986) shows that they differ subtly but consistently. The Taiwanese/Japanese form differs from P. enthrix in having fewer spines on the frontal margin of the carapace, in having a short median carina instead of an indistinct swelling on the sixth abdominal tergite, and in colour-in-life. In P. enthrix the frontal margin between the inner orbital margins is lined with spines. Conversely, in the Taiwanese/Japanese form, only a single spine is present between the paired rostral spines and the spine of the inner orbital margin. The most striking difference between the two forms, however, is the colour-in-life. Polycheles enthrix is uniformly deep-red in life (Ahyong & Brown, 2002), whereas the Taiwanese/Japanese form is generally orange-pink or pink-red with the cervical and branchial grooves, lateral and posterior margins of the carapace white or cream in colour. The Taiwanese/Japanese form agrees in almost all respects with the figure and brief account of P. amemiyai Yokoya, 1933 , described from Japan. Yokoya (1933) did not record the colour-in-life of P. amemiyai , but his description and figure clearly indicate the spination of the frontal margin of the carapace – in precise agreement with the specimens reported here. Unfortunately, the holotype of P. amemiyai appears to be lost ( Galil, 2000, T. Komai, pers. comm.) and Yokoya’s (1933) account of P. amemiyai neither mentions the number of spines on the anterolateral margin of the basal antennular segment, nor are any spines shown in his figure. However, in all other respects, the present specimens agree with the type description and figure of P. amemiyai . Therefore, P. amemiyai is herein recognised as a distinct species and removed from the synonymy of P. enthrix .

As with P. enthrix , P. amemiyai differs from P. kermadecensis in colour-in-life and in lacking the numerous dorsal spines on the gastric and branchial regions of the carapace. As with P. enthrix , P. kermadecensis also differs from P. amemiyai in bearing more numerous frontal spines on the carapace. Polycheles kermadecensis bears a similar colour pattern to P. amemiyai in having white carapace grooves and margins, but differs in being pale pinkish-purple instead of orangishpink or pinkish-red in life.

The Taiwanese specimens of P. amemiyai are morphologically uniform, showing slight variation in the lateral carapace spination and acuteness of the antrorse median abdominal spines. The antrorse median spines on abdominal tergites 1-4 are generally sharp in small specimens and blunt in adults. Hence, variation in the acuteness of the median antrorse tooth on the posterior abdominal tergites in P. amemiyai resembles that of P. enthrix and P. kermadecensis as reported by Ahyong & Brown (2002). Variation is also present in the chelation of the fifth pereopod in the females. In the juvenile female, the dactylus is about twice as long as the pollex, whereas in the adult, the pollex and dactylus are equal. In females, the dactylus becomes relatively shorter with increasing body size.

The Japanese specimen figured in colour by Baba et al. (1986) as Stereomastis nana is clearly referable to P. amemiyai . The colour and frontal ornamentation of the carapace agree precisely with the present specimens of P. amemiyai . In removing P. kermadecensis from the synonymy of P. enthrix, Ahyong & Brown (2002) suggested that all records of P. enthrix require verification. Judging by the known distribution of P. amemiyai , it is likely that other records of P. enthrix from the East China Sea and Japan are also based on the former species. Thus, P. enthrix has a central to western Pacific distribution, ranging from Fiji to eastern Australia. Polycheles kermadecensis has a southwestern Pacific distribution, ranging from the Kermadec Islands to eastern Australia, and P. amemiyai is presently known only from the northwestern Pacific around Japan and Taiwan.

Distribution. – Presently known only from Taiwan and Japan at depths of 452 (perhaps 280, see station data of CD140) - 1000 m ( Baba et al., 1986, as Stereomastis nana ).

Figures

Fig. 2. Polycheles amemiyai Yokoya, 1933. A-J, NTOU, female, cl. 25.4 mm. K, NTOU, female, cl. 50.5 mm. L, M, ZRC 2001.0126, male, cl. 49.1 mm. A, anterior carapace, dorsal. B, anterior cephalothorax, right lateral. C, anterior cephalothorax, right ventral. D, antennule, right dorsal. E, maxilliped 3, right. F, pereopod 2, right lateral. G, pereopod 3, right lateral. H, pereopod 4, right lateral. I, pereopod 5, right lateral. J-L, pereopod 5 chela, right internal. Scale A-C, E-I = 4 mm, D, L, K = 2 mm, M = 8 mm.

Fig. 4. A, Pentacheles laevis Bate, 1878 (TAIWAN 2000 stn CP 23, female cl. 27 mm). B, Polycheles aculeatus Galil, 2000 (Tai-Shi fishing port, 1 male cl. 34.6 mm). C, Polycheles amemiyai Yokoya, 1933 (Tai-Shi fishing port, ovigerous female cl. 63.4 mm). D, Polycheles auriculatus (Bate, 1878) (TAIWAN 2000 stn CP 61, male cl. 15.0 mm). E. Polycheles coccifer Galil, 2000 (Tai-Shi fishing port, male cl. 33.5 mm). F, Polycheles galil Ahyong & Brown, 2002 (TAIWAN 2001 stn CD 138, male cl. 41.7 mm). G, Polycheles helleri Bate, 1878 (TAIWAN 2001 stn CP 125, ovigerous female cl. 50.0 mm). H, Polycheles typhlops Heller, 1862 (Tai-Shi fishing port, ovigerous female cl. 54.3 mm).