Periclimenaeus apomonosi, Park & De Grave, 2021

Park, Jin-Ho & De Grave, Sammy, 2021, Two New Species and a Further Country Record of the Caridean Shrimp Genus Borradaile, 1915 from Korea (Decapoda: Palaemonidae)., Zoological Studies 60 (1), pp. 1-27 : 13-20

publication ID	https://doi.org/ 10.6620/ZS.2021.60-01
DOI	https://doi.org/10.5281/zenodo.8055883
persistent identifier	https://treatment.plazi.org/id/03AB9F22-FF8D-FFEE-1D63-FBB1FCEDFDA7
treatment provided by	Valdenar
scientific name	Periclimenaeus apomonosi
status	sp. nov.

Treatment

Periclimenaeus apomonosi View in CoL sp. nov. Park and

De Grave ( Figs. 10–15 View Fig View Fig View Fig View Fig View Fig View Fig ) urn:lsid:zoobank.org:act:BDC1C00D-392A-421F-8E7B-2933E1B31FF4

Material examined: Holotype. 1 female (pocl 3.4); Jun. 20, 2018; Munseom Islet, Jejudo Island (33°13'37"N 126°34'8"E), 45m, inside of unidentified sponge host, leg. JH Park ( NIBRIV0000862976 ) GoogleMaps . Paratypes. 1 female (pocl 2.4); Mar. 31, 2018; same location, 45 m, leg. JH Park ( OUMNH. ZC.2018-03- 029), 1 male (pocl 2.6); Mar. 31, 2018; same location, 30 m, inside of same unidentified sponge host, leg. JH Park ( NIBRIV 0000862975). GenBank accession numbers for DNA sequences data are presented in table 1 View Table 1 .

Description: Body medium-sized, subcylindrical form ( Figs. 10 View Fig , 15A View Fig ). Rostrum ( Fig. 11B View Fig ) straight, slightly inclined downwards, about 0.4 of pocl, overreaching end of basal segment of antennular peduncle, 7–8 dorsal teeth along entire length, without ventral tooth.

Carapace ( Fig. 11A, B View Fig ) smooth, glabrous, with small acute supraorbital tooth, with feeble supraorbital ridge; antennal tooth acute; inferior orbital angle with pointed process ( Fig. 11C View Fig ); pterygostomial angle rounded, not produced anteriorly.

Abdomen smooth ( Fig. 11D View Fig ), first segment with anteromedian dorsal lobe; pleura broadly rounded, sixth segment about 1.2 times length of fifth, about 0.5 of telson length, posterolateral angle sharply pointed, posteroventral angle acute.

Telson ( Fig. 11E View Fig ) about 0.6 of pocl, about 2.2 times longer than maximum width; two pairs of dorsal subequal spiniform setae at about 0.1 and 0.6 of telson length respectively, posterior margin ( Fig. 11F View Fig ) with three pairs of spiniform setae, lateral posterior spiniform setae short, about one third of length of intermediate pair, intermediate pair long and stout, submedian pair about 0.8 of intermediate pair length, setulose.

Eye ( Fig. 12A View Fig ) with hemispherical cornea, about 1.3 times longer than maximum dorsal and lateral width, without nebenauge.

Antennule ( Figs. 11A View Fig , 12B View Fig ) with proximal segment of peduncle bearing acute distolateral tooth, with small acute tooth at ventromedial margin; stylocerite bearing sharp point, reaching to about 0.5 of proximal segment; intermediate segment short, about 0.25 times of proximal segment length, subequal in length to distal segment; upper flagellum biramous, proximal five segments fused, short free ramus with three segments, longer free ramus with eleven segments; lower flagellum filiform.

Antenna ( Fig. 12C, D View Fig ) with rounded medial boss proximally; basicerite with distinct teeth distolaterally an d d is to med ially (F ig. 1 2 C), is ch io cer ite a n d merocerite unarmed; carpocerite reaching about 0.6 of scaphocerite; scaphocerite about 2.0 times as long as maximum width, rounded distal end of lamella almost in line with distolateral tooth.

Mouthparts not dissected, typical for genus in external observation. Third maxilliped ( Fig. 12E View Fig ) with ultimate segment length about 0.4 times antepenultimate segment, tapering distally, with dense tufts of long setae; penultimate segment length about 0.6 times antepenultimate segment, with ventral row of long setae; antepenultimate segment with long setae on ventromedial margin; exopod reaching 0.9 of antepenultimate segment, with four plumose distal setae; coxa with rounded lateral plate. Arthrobranch absent.

First pereiopod ( Figs. 10 View Fig , 13A View Fig ) with coxa and basis without special features; ischium about 0.7 of merus length, unarmed; merus about 1.2 times as long as carpus length, unarmed; carpus about 1.1 times as long as chela length; carpo-propodal cleaning setae developed; chela about 0.3 times as long as pocl; palm subcylindrical, smooth, non-tuberculate; fingers ( Fig. 13B View Fig ) similar in shape, about 0.4 of palm length, with group of setae, subspatulate, with elongate apices of fingers, cutting edges medial, entire.

Second pereiopods ( Figs. 10 View Fig , 13C, E View Fig ) robust, dissimilar in shape, unequal in size.

Major second pereiopod ( Figs. 10 View Fig , 13C View Fig ) with coxa and basis without special features; ischium subequal to merus length, tuberculate ventrally; merus about 0.4 of palm length, tuberculate ventrally; carpus one third of palm length, tapering proximally, unarmed; chela ( Fig. 13D View Fig ) about 1.4 times as long as pocl, about 3.4 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; 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. 10 View Fig , 13E View Fig ) with coxa and basis without special features; ischium subequal to merus length, tuberculate ventrally; merus about 0.5 of palm length, tuberculate ventrally; carpus about 0.3 of palm length, tapering proximally, unarmed; chela ( Fig. 13F View Fig ) about 0.85 times as long as pocl, about 0.6 of major chela length, about 2.6 times as long as merus; palm subcylindrical, tuberculate; fingers unequal in size; fixed finger about 0.85 of dactylus length, with strong subacute tip, cutting edge with groove extending to 0.9 of fixed finger, cutting edge slightly concave, proximal margin with lower triangular process; dactylus about one third of palm length, about 1.7 times as long as maximal depth, slightly exceeding fixed finger, with broadly rounded dorsal margin, tip with large tooth, cutting edge entire, convex, proximal cutting edge angular.

Ambulatory pereiopods subequal ( Figs. 10 View Fig , 14 View Fig ) in shape, fifth pereiopod slightly more slender than third and fourth.

Third pereiopod ( Fig. 14A, B View Fig ) with coxa and basis without special features; ischium about 0.8 of merus length, unarmed; merus about 1.5 of carpus length, unarmed; carpus about 0.7 of propodus length, unarmed; propodus about 4.6 times as long as maximal depth, sparsely setose, with pair of stout distoventral spiniform setae, five or six spiniform setae along whole ventral border; dactylus about 0.2 of propodus length, biunguiculate; unguis demarcated, curved, corpus compressed, tapering distally, dorsal margin slightly convex, ventral margin slightly concave with distinct acute distal accessory tooth about 0.4 of unguis length, distal two thirds with five acute denticles, sensory setae distolaterally.

Fourth pereiopod ( Fig. 14C, D View Fig ) with coxa and basis without special features; ischium about 0.7 of merus length, unarmed; merus about 1.5 of carpus length, unarmed; carpus about 0.7 of propodus length, unarmed; propodus about 5.5 times as long as maximal depth, sparsely setose, with pair of stout distoventral spiniform setae, five spiniform setae on ventral border; dactylus about 0.2 of propodus length, biunguiculate; unguis demarcated, curved, corpus compressed, tapering distally, dorsal margin slightly convex, ventral margin slightly concave with distinct acute distal accessory tooth, distal two thirds with four acute denticles, sensory setae distolaterally.

Fifth pereiopod ( Fig. 14E, F View Fig ) with coxa and basis without special features; ischium about 0.6 of merus length, unarmed; merus about 1.3 of carpus length, unarmed; carpus about 0.7 of propodus length, unarmed; propodus about 7.6 times as long as maximal depth, with two rows of distolateral setae, with single stout distoventral spiniform setae, two spiniform setae distomedially; dactylus about 0.2 of propodus length, biunguiculate; unguis demarcated, curved, corpus compressed, tapering distally, dorsal margin slightly convex, ventral margin slightly concave with distinct acute distal accessory tooth, with five acute denticles, sensory setae distolaterally.

Second pleopod of male ( Fig. 12G View Fig ) with endopod with long appendix masculina in relation to appendix interna, with two long terminal setulose setae; appendix interna about 1.3 times longer than appendix masculina ( Fig. 12H View Fig ).

Second pleopod of female ( Fig. 12F View Fig ) with endopod with appendix interna, protopod medially two ovigerous setae proximally, one distally, laterally with single seta proximally.

Uropodal exopod ( Fig. 11E View Fig ) shorter than endopod, outer margin entire, slightly convex, with single spiniform setae, curved inward, about 2.0 times as long as acute distolateral tooth.

Variation: The general morphology is very similar between both sexes, even in the relative sizes of the major and minor second chela.

Host: The specimens were collected from an unidentified sponge ( Fig. 15B View Fig ).

Etymology: From the Greek apomonosi (απομόνωση, isolation and seclusion), referring to the lifestyle of the new species within the host sponge species. It also alludes to the seclusion of human society due to the coronavirus pandemic (COVID-19), during which time this paper was written. Used as a noun in apposition.

Distribution: Presently only known from the type locality in Jejudo Island, Korea ( Fig. 1A, B View Fig ).

Remarks: Periclimenaeus apomonosi sp. nov. appears morphologically close to P. hebedactylus Bruce, 1970 and P. nufu Ďuriš, Horká & Hoc, 2009 , sharing with those species the presence of a supraorbital tooth or ridge, the non-denticulate cutting edges of the dactyli of the first and second pereiopods, and a distal accessory tooth as well as the corpus with ventral denticles on the ambulatory dactyli. Periclimenaeus tuamotae Bruce, 1969 and P. bidentatus Bruce, 1970 also resemble the species in having a supraorbital tubercle and non-tuberculate cutting edges. However, the presence of the anterodorsal medial lobe of the first abdominal tergite is not clear in the type (and only) descriptions ( Bruce 1969 1970).

Periclimenaeus hebedactylus is readily distinguished from P. apomonosi by the position of the dorsal spiniform setae on the telson (both pairs at 0.2 of telson length in P. hebedactylus vs. proximal pair at about 0.2 and distal pair at 0.6 in P. apomonosi sp. nov.). Periclimenaeus nufu is also readily separated from the new species by the presence of serrations on the uropodal exopod (vs. non-serrated in P. apomonosi sp. nov.). Periclimenaeus bidentatus clearly differs from the new species by the bidentate distal dactylus of the minor second pereiopod (vs. single tooth in P. apomonosi sp. nov.).

Bruce (1969) provided a detailed, but unillustrated description of P. tuamotae . Based on his description, P. tuamotae and the new species share several characters: 1) carpocerite not exceeding the distal margin of the scaphocerite, 2) a finely tuberculate ventral margin of the second pereiopod chelae, and 3) the presence of tubercles along the ventral margin on the merus and ischium of both second pereiopods. However, P. tuamotae differs from P. apomonosi as follows: 1)

inferior orbital angle obsolete (vs. with pointed process in P. apomonosi sp. nov.), 2) basicerite of antenna unarmed (vs. with distinct teeth distolaterally and distomedially on dorsal margin in P. apomonosi sp. nov.), 3) scaphocerite not exceeding second segment of antennular peduncle (vs. exceeding distal margin of antennular peduncle in P. apomonosi sp. nov.), 4) distolateral tooth of scaphocerite extending beyond the lamella (vs. slightly exceeding or almost in line in P. apomonosi sp. nov.), 5) eye exceeding the rostrum (vs. not in P. apomonosi sp. nov.), 6) fingers of first pereiopod 0.6 of length of palm (vs. 0.4 in P. apomonosi sp. nov.), 7) carpus of first pereiopod about 1.5 times the length of the chela (vs. about 1.1 times in P. apomonosi sp. nov.), 8) two to three spiniform setae along ventral border of fourth pereiopod and none on fifth pereiopod (vs. five and two respectively in P. apomonosi sp. nov.).