Homola dickinsoni Eldredge, 1980

Ng, Peter K. L., Forges, Bertrand Richer De & Martin, Joel W., 2020, The Homolidae of the Hawaiian Islands, with notes on the taxonomy of Moloha major (Kubo, 1936) (Crustacea: Decapoda: Brachyura), Zootaxa 4809 (2), pp. 306-328 : 308-310

Homola dickinsoni Eldredge, 1980

( Fig. 1F )

Homola dickinsoni Eldredge, 1980: 274 , figs. 2, 3; Guinot & Richer de Forges 1995: 338, figs. 9g, 13e, 14a, b; Ng et al. 2008: 40; Castro 2011: 34 .

Homola ikedai — Guinot & Richer de Forges 1981: 536, figs. 2A, A1, pl. 2 figs. 2, 2a, 2b, pl. 8 fig. 1, 1a (not Homola ikedai Sakai, 1979 ).

? Homola ikedai — Titgen 1988: 144.

Material examined. Guam: 1 male holotype (42.0 × 37.0 mm) ( BPBM S8595 ), off Double Reef , 366 m, coll. trap number 49, 6August 1975 .— 1 female paratype (32.0 × 26.6 mm) ( BPBM S8596 ), same data as holotype .— 1 female (45.6 × 36.7 mm) ( ZRC 1997.0691 ), Double Reef , 243.8 m, coll. shrimp trap, 30 January 1976 .— 1 female ( BPBM S10479 ), Double Reef , 243.8 m, shrimp trap, 30 November 1976 .— 1 female (40.0 × 31.5 mm) ( ZRC 2001.0758 ), left tip of Anae and Silver Reef top, Anae Island, coll. shrimp trap, 16 October 1975 .— 1 female ( BPBM S10477 ), Oca Point (= Hospital Point), 457.2 m, in shrimp trap number 15, coll. November 1973 - April 1974 . Hawaiian Islands : 1 male (40.3 × 33.3 mm) ( BPBM S1976.259 ), Pearl Harbour entrance, O‘ahu, 340 m, coll. “Easy Rider”, E. Chave, in shrimp trawl, 27 September 1976 .— 1 male (42.0 × 36.3 mm) (LACM-MBC-5503), reef slope, station FFS-0001, DRS-1, BAIT-1, 23.74°N 166.387°W– 23.734°N 166.381°W, NWI, French Frigate Shoals , 180–250 m, baited trap, coll. R. Moffitt, T. Lotufo, K. Coontz, L. Harris, E. Soto & C. Pittman, 11 October 2006 (photograph voucher JM0038 ) .

Remarks. Our specimen agrees well with the original description of the species from Guam by Eldredge (1980) as well as the subsequent redescription and photographs of the paratypes in Guinot & Richer de Forges (1995: figs. 9g, 13e, 14a, b). The only previous record of the species in Hawaii is a report by Titgen (1988) based on two speci- mens collected in 1976 at 338 m depth near the entrance to Pearl Harbor in O‘ahu. Titgen (1988: 144) referred these two specimens to Homola ikedai Sakai, 1979 , but after examining one of Titgen’s specimens (a 40.3 mm carapace length male, BPBM Acc. No. 1976.259), Guinot & Richer de Forges tentatively assigned it to Homola dickinsoni instead.

As discussed by Richer de Forges & Ng (2007: 32), H. dickinsoni belongs to a group of species that have in common a strongly rectangular carapace and a strong anterolateral tooth. This group includes, in addition to H. dickinsoni , H. ikedai from the western Pacific, H. eldredgei from the Indian Ocean ( Seychelles), and H. coriolisi from New Caledonia and the Loyalty Islands (see Richer de Forges & Ng 2007; Cleva et al. 2007). Homola dickinsoni is morphologically similar to the relatively smaller H. ikedai (see Guinot & Richer de Forges 1995: 340) and can be misidentified. Richer de Forges & Ng (2007: 33) separated H. dickinsoni in that the tip of its rostrum is minutely bifid (simple in H. ikedai ), the carpus of the cheliped is more spinous, the P3 and P4 merus has two rows of ventral spines (unarmed in H. ikedai ), and the P5 merus is relatively shorter, with four or five ventral spines (merus relatively longer and with three ventral spines in H. ikedai ). On this basis, the six specimens from Balicasag Island in the Philippines referred to “ H. dickinsoni ” by Takeda & Manuel-Santos (2007: 87) were referred to H. ikedai as well by Richer de Forges & Ng (2007: 33). The fresh colour of H. dickinsoni ( Fig. 2F ) shown here for the first time provides another differentiator. In H. ikedai , the chelae and dactyli of the ambulatory legs are white ( Richer de Forges & Ng, 2007: fig. 1B) whereas these structures are all orange, with faint light banding on the merus of the ambulatory legs, in H. dickinsoni ( Fig. 1F ). On the basis of the above characters, the present specimen from Hawai‘i and Titgen’s (1988) material are clearly H. dickinsoni .

Distribution. Known only from Guam and the Hawaiian Islands (O‘ahu), 300–500 m ( Eldredge 1980; Guinot & Richer de Forges 1995; Richer de Forges & Ng 2007), and now from the Northwestern Hawaiian Islands (French Frigate Shoals).

Figures

FIGURE 1. Colour in life, overall dorsal view. A, Homola orientalis, female (44.6 × 37.8 mm), JM0048 (LACM-MBC-5514); B, H. orientalis, JM0081 (LACM); C, H. orientalis carrying sponge, JM0078 (LACM); D, H. orientalis, male carrying sponge, JM0049 (LACM-MBC-5514), E, H. orientalis, female carrying sponge, JM0062 (LACM); F, H. dickinsoni, male (42.0 × 36.3 mm) JM0038 (LACM-MBC-5503). All from Hawai’i.

FIGURE 2. Colour in life. A, Moloha major, male (78.1 × 71.6 mm), JM0095 (LACM-MBC-5564); B, M. major, male (60.3 × 52.4 mm), JM0043 (ZRC 2019.1109). C–E, Yaldwynopsis hawaiiana, female (51.0 × 46.4 mm) carrying gorgonian, JM0211 (LACM-MBC-5664). A–C, overall dorsal view; D, left cheliped and front; E, outer view of left chela.All from Hawai’i.