Periclimenaeus djiboutensis Bruce, 1970

(Figs. 16–18)

Periclimenaeus djiboutensis Bruce, 1970: 307 (type locality: Djibouti); 1975: 1568, figs. 3G, H, 8, 9, 13A-D; 1976: 472; 1978: 256, figs. 28, 29; 1981: 11; 1984: 205; Nomura et al., 1996: 10; Marin, 2007: 227, fig. 10; Marin and Caley, 2011, 7.

Material examined: 1 ovig. female (pocl 3.7); Oct. 15, 2001; Geomundo Island, Dadohaehaesang National Park, Korea (34°2'60"N 127°19'43"E), inside of unidentified sponge host, leg. SNU staff (Laboratory of Systematics and Molecular Evolution) (NIBRIV 0000877271).

Description of Korean specimen: Body medium-sized, subcylindrical form (Fig. 16). Rostrum (Fig. 17A) straight, downward, about 0.3 of pocl, reaching 0.9 of basal segment of antennular peduncle, 7 dorsal teeth along entire length, without ventral tooth.

Carapace (Fig. 16) smooth, glabrous, with feeble supraorbital ridge, without supraorbital tooth or tubercle; antennal tooth acute; inferior orbital angle (Fig. 17B) with pointed process; pterygostomial angle rounded, produced anteriorly, with simple setae.

Abdomen (Fig. 16) smooth, first segment with anteromedian dorsal lobe; pleura broadly rounded, sixth segment as long as fifth length, about 0.6 of telson length, posterolateral angle rounded without tooth, porsteroventral angle rounded.

Telson (Fig. 17G) about 0.6 of pocl, about 2.5 times maximum width; two pairs of dorsal spiniform subequal setae at about 0.05 and 0.1 of telson length respectively, posterior margin (Fig. 17H) with three pairs of spiniform setae, lateral posterior spiniform setae short, about 0.2 of length of intermediate pair, intermediate pair long and stout, submedian pair about 0.9 of intermediate pair length, reaching distal margin of intermediate pair, setulose.

Eye (Figs. 16, 17C) with hemispherical cornea, about 1.8 times longer than maximum dorsal width, without nebenauge.

Antennule (Figs. 16, 17C) with proximal segment of peduncle bearing acute distolateral tooth, with acute ventromedial tooth at about 0.5 of proximal segment of peduncle (Fig. 17D); stylocerite bearing sharp point, reaching to about 0.5 of proximal segment; intermediate segment about 0.3 times of proximal segment length; distal segment about 0.7 times of proximal segment length; upper flagellum biramous, lower flagellum filiform.

Antenna (Fig. 17E, F) with basicerite with distinct rounded lobe laterally, with distomedial tooth; ischiocerite and merocerite unarmed; carpocerite extending to distal end of scaphocerite; scaphocerite about 2.3 times as long as maximum width, rounded distal margin of lamella exceeding acute distolateral tooth.

Mouthparts not dissected, typical for the genus in external observation.

First pereiopod (Figs. 16, 18A) with coxa and basis without special features; ischium about 0.6 of merus length, unarmed; merus about 1.1 times as long as carpus length, unarmed; carpus about 1.6 times as long as chela length; chela about 0.3 times of pocl; palm subcylindrical, smooth, non-tuberculate; fingers (Fig. 18B) about 0.2 of palm length, with group of terminal setae, with three terminal teeth.

Second pereiopods (Figs. 16, 18C, D) robust, dissimilar in shape, unequal in size.

Major second pereiopod (Figs. 16, 18C) with coxa and basis without special features; ischium about 0.8 of merus length, tuberculate ventrally; merus about 0.4 of palm length, tuberculate ventrally; carpus about 0.3 of palm length, tapering proximally, unarmed; chela about 1.9 times as long as pocl; chela about 3.6 times as long as merus length; palm subcylindrical, tuberculate; fingers unequal in size, slightly curved mesially; fixed finger with strong subacute tip, distal cutting edge entire, proximal cutting edge with deep oval fossa, mesial margin with triangular process, lateral margin with angular process; dactylus slightly exceeding fixed finger, about 0.4 of palm length, with strong subacute tip, distal cutting edge entire, proximal cutting edge with large molar process.

Minor second pereiopod (Figs. 16, 18D) with coxa and basis without special features; ischium and merus subequal in length, tuberculate ventrally; carpus about 0.3 of palm length, tapering proximally, unarmed; chela about 0.9 times as long as pocl, about 0.5 of major chela length, about 2.7 times as long as merus; palm subcylindrical, tuberculate; fixed finger about 0.4 of palm length, with acute tip, cutting edge with groove, concave, entire; dactylus incomplete, with rounded dorsal margin, cutting edge entire, proximal cutting edge angular.

Ambulatory pereiopods (Figs. 16, 18E, I, G) subequal in shape, third pereiopod longer and more robust than fourth and fifth; fourth slightly longer and more robust than fifth.

Third pereiopod (Fig. 18E, F) with coxa and basis without special features; ischium about 0.7 of merus length, unarmed; merus about 1.5 of carpus length, about 2.0 times as long as maximal depth, unarmed; carpus about 0.9 of propodus length, about 2.6 times as long as maximal depth, unarmed; propodus about 3.2 times as long as maximal depth, sparsely setose, with pair of stout distoventral spiniform setae, three spiniform setae on ventral border; dactylus about 0.2 of propodus length, biunguiculate; unguis demarcated, curved, corpus ventrally with distinct acute distal accessory tooth, distoventral tubercles obsolescent, entire proximally, sinuous, concave distally, convex proximally, sensory setae distolaterally.

Fourth pereiopod (Fig. 18G, H) with coxa and basis without special features; ischium about 0.8 of merus length, unarmed; merus about 1.5 of carpus length, about 3.1 times as long as maximal depth, unarmed; carpus about 0.8 of propodus length, about 3.3 times as long as maximal depth, unarmed; propodus about 4.9 times as long as maximal depth, sparsely setose, with pair of stout distoventral spiniform setae, two spiniform setae on ventral border; dactylus about 0.16 of propodus length, biunguiculate; unguis demarcated, curved, corpus ventrally with distinct acute distal accessory tooth, entire, sinuous, concave distally, convex proximally, sensory setae distolaterally.

Fifth pereiopod (Fig. 18I, J) with coxa and basis without special features; ischium about 0.7 of merus length, unarmed; merus about 1.2 of carpus length, about 3.7 times as long as maximal depth, unarmed; carpus about 0.8 of propodus length, about 3.6 times as long as maximal depth, unarmed; propodus about 5.3 times as long as maximal depth, with row of distolateral setae, with single stout distoventral spiniform setae, one spiniform setae distomedially; dactylus about 0.2 of propodus length, biunguiculate; unguis demarcated, curved, corpus ventrally with distinct acute distal accessory tooth, entire, sinuous, concave distally, convex proximally, sensory setae distolaterally.

Uropodal exopod (Fig. 17G) shorter than endopod, outer margin entire, with single spiniform setae, curved inward, about 2.5 times longer than acute distolateral tooth.

Host: The specimens were collected from an unidentified sponge.

Distribution: Periclimenaeus djiboutensis was described from Djibouti (Bruce 1970) and has since been reported from Tanzania (Bruce 1976), Madagascar (Bruce 1978), Vietnam (Marin 2007), Queensland, Australia (Bruce 1981; Marin and Caley 2011), and the Ryukyus, Japan (Nomura et al. 1996) (Fig. 1C). The record from Eilat, Israel (Fishelson 1974) was considered to be erroneous by Ďuriš et al. (2011a). The present record is the first for Korea (Fig. 1).

Remark: Although the distal margin of the dactylus of the minor second pereiopod is incomplete, the present specimen agrees well with previous descriptions of Periclimenaeus djboutensis by having a rounded lateral lobe on the antennal basicerite, the shape of the chela of the first pereiopod and the characteristic, dorsal spiniform setae situated on the proximal part of the telson (Bruce 1970 1975 1978). These morphological affinities easily distinguish the species from other sponge associated Periclimenaeus species. However, the Korean specimen exhibits the following differences compared with previous descriptions: 1) inferior orbital angle with dentate process in Korean specimen (Fig. 17B), versus absent in the type description (Bruce 1970), 2) corpus of the ambulatory dactyli without distoventral tubercles in Korean (Fig. 18F, H, J) and Vietnamese specimens (see Fig. 10L in Marin 2007), versus blunt tubercles present on the corpus in Madagascan specimens (see Fig. 29G in Bruce 1978), and 3) the antennal basicerite with distomedial dorsal process in Korean (Fig. 17F) and Djibouti specimens (see Fig. 9B in Bruce 1975), but absent in Vietnamese specimens (see Fig. 10B in Marin, 2007). Further, Bruce (1975 1978) illustrated a strongly hooked bidentate tip on the dactylus of the minor second pereiopod. However, Marin (2007) illustrated only a single acute tip in a Vietnamese specimen. It is presently unclear if these differences are intraspecific morphological variation or potentially could reveal further undescribed species.