Periclimenaeus karantina Park & De Grave 2021, sp. nov.

Periclimenaeus karantina sp. nov. Park and De

Grave (Figs. 2–9) urn:lsid:zoobank.org:act: 5157B8FA-51BE-476E-8B98- 100D6ABDF592

Material examined: Holotype. 1 male (pocl 3.3); Oct. 22, 2019; Munseom Islet, Jejudo Island (33°13'30"N 126°34'13"E), 21 m, leg. JH Park (NIBRIV0000862971). Paratypes. 1 female (pocl 3.5); Aug. 08, 2016; same location, 20 m, leg. JH Park (NIBRIV 0000862966, transferred from SNU KR_JH 474); 1 ovig. female, 1 male (pocl 4.1, 3.5); Aug. 16, 2019; Seopseom Islet, Jejudo Island (33°13'44.37"N 126°35'43.74"E), 38 m, leg. JH Park (NIBRIV 0000862967-68); 1 female, 1 male (pocl 3.8, 3.5); Aug. 16, 2019; same location, leg. JH Park (OUMNH. ZC.2018 -03-027, OUMNH. ZC.2018 - 03-028); 1 ovig. female, 1 female, 2 males (pocl 4.5, 3.2, 3.4, 2.8); Oct. 21, 2019; same location, depth, leg. JH Park (NIBRIV 0000862972-862974, NIBRIV 0000877272); 1 juv., 1 ovig. female, 1 male (pocl 1.9, 3.4, 3.1); same data as holotype, leg. JH Park (NIBRIV 0000862969-862970, NIBRIV 0000877273); 1 ovig. female, 1 female, 2 males (pocl 4.6, 3.5, 3.8, 3.3); Jan. 13, 2020; Munseom Islet Jejudo Island, 32m, leg. JH Park (NIBRIV 0000877274-877277); 1 ovig. female, 1 female, 2 males (pocl 4.1, 3.4, 3.7, 2.9); Jan. 14, 2020; same location, 24 m, leg. JH Park (NIBRIV 0000877278-877281); 1 ovig. female, 1 male (pocl 4.4, 3.5); Jan. 14, 2020; same location, 24 m, leg. JH Park (NIBRIV 0000877282-877283); 1 male (pocl 3.1); Jan. 15, 2020; same location, 21 m, leg. JH Park (JH 1108). All collected from a colonial didemnid ascidian Leptoclinides sp. (Ascidiacea: Aplousobranchia: Didemnidae) (Fig. 9). GenBank accession numbers for DNA sequences data are presented as table 1.

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Description: Body medium-sized, subcylindrical form (Fig. 2).

Rostrum (Figs. 2, 3 A) straight, trending

Used symbols: N/A – not available; * Leptoclinides sp. – tissue sample of the host colonial ascidian of Periclimenaeus karantina sp. nov. (NIBRIV0000862967).

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downwards, about 0.4 of pocl, reaching slightly beyond distal margin of basal segment of antennular peduncle, with 4 equally spaced dorsal teeth, without ventral tooth.

Carapace (Fig. 2) smooth, glabrous, without supraorbital tooth or tubercles, with feeble supraorbital ridges; antennal tooth acute; inferior orbital angle with round blunt process (Fig. 3C); pterygostomial angle produced.

Abdomen (Fig. 2) with smooth pleon, first segment without anteromedian dorsal lobe; pleura broadly rounded, sixth segment about 1.1 times length of fifth, about 0.5 of telson length, posterolateral angle rounded, posteroventral angle acute (Fig. 3D, E).

Telson (Fig. 2) about 0.7 of pocl, about 2 times longer than maximal width (Fig. 3E); two pairs of dorsal spiniform setae, subequal in size, at about 0.3 and 0.8 of telson length respectively, posterior margin with three pairs of spiniform setae, lateral posterior spiniform setae short, about 0.5 of length of intermediate pair, intermediate pair long and stout, submedian pair about 0.8 of intermediate pair length, distally setulose (Fig. 3F).

Eye (Fig. 4A, B) with hemispherical cornea, about 1.5 times longer than maximum dorsal width, about 1.2 times longer than maximum lateral width, nebenauge absent.

Antennule (Fig. 4C) with proximal segment of peduncle bearing acute distolateral tooth, with acute tooth at ventromedial margin (Fig. 4D); stylocerite broad, bearing sharp point, reaching to about 0.5 of proximal segment; intermediate segment short, about 0.3 times of proximal segment length, subequal to distal segment length; upper flagellum biramous, proximal five segments fused, short free ramus with two segments, longer free ramus with seven segment; lower flagellum with fourteen segments, filiform.

Antenna (Fig. 4E) with rounded boss proximally on coxa; basicerite without distoventral tooth, ischiocerite and merocerite unarmed; carpocerite exceeding scaphocerite; scaphocerite about 2.4 times as long as maximal width, distal lamella rounded, exceeding acute distolateral tooth situated at about 0.8 of scaphocerite length.

Mouthparts not dissected. Second maxilliped with normal endopod, exopod, oval epipod without podobranch. Third maxilliped (Fig. 5A) with ultimate segment about 0.5 times as long as antepenultimate segment, tapering distally, with dense tufts of long setae; penultimate segment about 0.6 times antepenultimate segment length, with ventromedial row of long setae; antepenultimate segment with long setae on ventromedial margin; exopod reaching middle of penultimate segment, distally with six plumose setae; coxa with rounded lateral plate, without arthrobranch.

First pereiopod (Figs. 2, 6A) with coxa and basis without special features; ischium about 0.6 of merus length, unarmed; merus subequal to carpus length, unarmed; carpus about 1.2 times as long as chela, tapering proximally; carpo-propodal cleaning brush developed; chela about 0.4 times as long as pocl, about 0.7 times as long as merus length; palm subcylindrical, smooth, non-tuberculate; fingers about 0.9 of palm length, subspatulate, with subterminal group of setae (Fig. 6B), with three terminal teeth, pair of subterminal teeth short, about 0.6 of median tooth length (Fig. 6C).

Second pereiopods (Figs. 2, 7) robust, dissimilar in shape, unequal in size.

Major second pereiopod (Fig. 2) with coxa and basis without special features; ischium about 0.8 of merus length, tapering proximally, unarmed; merus about 0.3 of palm length, with minute tubercles on ventral margin (Fig. 8E, F); carpus about 0.3 of palm length, tapering proximally, unarmed; chela about 1.7 to 2.6 times as long as pocl, about 4.3 times as long as merus length (Fig. 7A); palm subcylindrical, smooth, non-tuberculate; fingers (Fig. 7B) about 0.4 of palm length, distally curved mesially (Fig. 7C), with subterminal group of setae; fixed finger with strong subacute tip, distal cutting edge concave, entire, proximal cutting edge with deep oval fossa, mesial margin with triangular process (Fig. 7B), lateral margin with lower rounded process (Fig. 7A); dactylus with strong subacute tip, distal cutting edge with about 50 small acute teeth (Fig. 7D), proximal cutting edge with large molar process.

Minor second pereiopod (Fig. 2) with coxa and basis without special features; ischium subequal to merus length, tapering proximally, unarmed; merus about 0.4 of palm length, with minute tubercles on ventral margin (Figs. 7E, 8D); chela about 1.2 times as long as pocl, about 0.5 of major chela length, about 3 times as long as merus, with fingers unequal in size; palm subcylindrical, smooth, non-tuberculate; carpus about 0.3 of palm length, tapering proximally, unarmed; fixed finger about 0.7 of dactylus length, with strong subacute tip, cutting edge with long groove extending to 0.9 of fixed finger from apex (Fig. 8A), lateral cutting edge slightly convex, proximal margin with lower rounded process, with denticulate mesial cutting edge (Fig. 8A, C), proximal margin with triangular tuberculate process (Fig. 8A, C); dactylus (Fig. 7F) about one third of palm length, about 2.0 times as long as maximal depth in midlength, exceeding fixed finger, with broadly rounded dorsal margin, tip with blunt tooth continuous with sinuous cutting edge, distally concave, proximally convex, with about 40 small acute teeth, decreasing in size proximally (Fig. 8 A, B), proximal cutting edge with right-angular obtuse process fitting to proximal end of occlusal groove on fixed finger (Fig. 8B).

© 2021 Academia Sinica, Taiwan

© 2021 Academia Sinica, Taiwan

Ambulatory pereiopods (Fig. 2) subequal in shape, third pereiopod strongest, fourth and fifth gradually slightly slender.

Third pereiopod (Fig. 6D) robust, sparsely setose; coxa and basis without special features; ischium about 0.7 of merus length, unarmed; merus about 1.2 of carpus length, unarmed; carpus about 0.9 of propodus length, tapering proximally, unarmed; propodus about 2.9 times longer than maximal depth, tapering distally, with two or three stout distoventral spiniform setae (Figs. 6E, 8G); dactylus about 0.2 of propodus length, unguis distinctly demarcated, simple, curved, about 0.3 of dorsal corpus length, corpus without distal accessory tooth, slightly convex distally, with minute acute proximal tooth (Figs. 6E, 8G), with sensory setae distolaterally.

© 2021 Academia Sinica, Taiwan

Fourth pereiopod (Fig. 6F) robust, sparsely setose; coxa and basis without special features; ischium about 0.8 of merus length, unarmed; merus about 1.2 of carpus length, unarmed; carpus about 0.9 of propodus length, tapering proximally, unarmed; propodus about 3.3 times longer than maximal depth, tapering distally, with pair of stout distoventral spiniform setae (Fig. 6G); dactylus about 0.16 of propodus length, unguis distinctly demarcated, simple, curved, about 0.4 of dorsal corpus length, corpus without distal accessory tooth, slightly convex distally, with minute acute proximal tooth (Fig. 6G), with sensory setae distolaterally.

Fifth pereiopod (Fig. 6H) robust, sparsely setose; coxa and basis without special features; ischium about 0.7 of merus length, unarmed; merus about 1.4 of carpus length, unarmed; carpus about 0.7 of propodus length, tapering proximally, unarmed; propodus about 4.7 times longer than maximal depth, tapering distally, with single stout distoventral spiniform setae, with distoventral setulose setae, with single spiniform setae distomedially (Fig 6I); dactylus about 0.13 of propodus length, unguis distinctly demarcated, simple, curved, about 0.3 of dorsal corpus length, corpus without distal accessory tooth, slightly convex distally, with minute acute proximal tooth (Fig 6I), with sensory setae distolaterally.

Second pleopod of male (Fig. 5B) with endopod with short appendix masculina in relation to appendix interna, with two long terminal setulose setae; appendix interna about 3.0 times as long as appendix masculina (Fig. 5C).

Second pleopod of female with protopod medially with two to four ovigerous setae proximally, two to three distally, proximo-laterally with single seta (Fig. 5D, E).

Uropod (Fig. 3E) reaching to telson tip; exopod slightly shorter than endopod, outer margin entire, with single spiniform setae, curved inward, about 2.3 times longer than acute distolateral tooth.

Variation: All intact 21 adult specimens have the same rostral formula (4/0) except for a single ovigerous specimen (pocl 4.6 mm, 3/0). The general morphology of both sexes is very similar, although the major second chela is distinctly larger in the relatively smaller male specimens. For example, the major second chela is about 2.6 times as long as the pocl in the holotype male (pocl 3.3 mm) and about 1.7 times in the largest ovigerous female paratype (pocl 4.6 mm). The dentition of the cutting edge of the fixed finger in the minor second chelae varies considerably (Fig. 8A, C) in the number of small teeth, ranging from none to 30 (holotype).

© 2021 Academia Sinica, Taiwan

© 2021 Academia Sinica, Taiwan

Colouration: Whole body and appendages semitransparent with a pale orange-cream background colour when alive (Fig. 9A); bright white and orange chromatophores scattered all over body and appendages (Fig. 9A, B).

© 2021 Academia Sinica, Taiwan

© 2021 Academia Sinica, Taiwan

Etymology: From the Greek karantina (καραντίνα, quarantine), referring to the lifestyle of the new species within the host ascidian species (Fig. 9B). It also alludes to the quarantine of human society due to the coronavirus pandemic (COVID-19), during which time this paper was written. Used as a noun in apposition.

© 2021 Academia Sinica, Taiwan

Host: The shrimp specimens were found inside the common cloacal system of an colonial didemnid ascidian Leptoclinides sp. (Ascidiacea: Aplousobranchia: Didemnidae) (Fig. 9B, C).

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

Remarks: The species is considered to be typical for ascidian associates due to the presence of a denticulate dactylus on the minor second pereiopod. Periclimenaeus karantina sp. nov. appears morphologically close to seven species: P. colemani Bruce, 2014, P. dactylodon Bruce, 2012a, P. devaneyi Bruce, 2010, P. diplosomatis Bruce, 1980, P. kottae Bruce, 2005a, P. myora Bruce, 1998, P. orbitocarinatus Fransen, 2006; and possibly P. zarenkovi Ďuriš, 1990. All these species share the following characters: 1) first abdominal tergite without anterodorsal medial lobe; 2) major and minor second chela with denticulate cutting edges on dactylus; and 3) the dactyli of the ambulatory pereiopods having a proximal ventral tooth, but no distoventral accessory tooth.

The new species shares with P. devaneyi, P. dactylodon, P. kottae and P. orbitocarinatus the presence of median tubercles on the ventral margin on the merus of both second pereiopods. However, P. devaneyi can be readily distinguished from the new species by the presence of a large spine on the distoventral angle of the carpus of the ambulatory pereiopods (vs. absent in P. karantina sp. nov.). Periclimenaeus dactylodon and P. kottae can also readily be distinguished from the new species by the presence of the proximal process on the corpus of the dactylus of the third pereiopod (with large rounded boss in P. kottae or large triangular basal tooth in P. dactylodon vs. with minute proximal tooth in P. karantina sp. nov.). Periclimenaeus orbitocarinatus clearly differs from the new species by the strongly pronounced postorbital ridge along the anterior margin of the carapace and the antennal carpocerite not overreaching the scaphocerite (vs. with feebly pronounced postorbital ridge and carpocerite overreaching the scaphocerite in P. karantina sp. nov.).

Periclimenaeus karantina sp. nov. can also be distinguished from P. diplosomatis, P. myora and P. zarenkovi, on the basis of the dactylus of the minor second pereiopod not exceeding the fixed finger and the ventral margin of the merus of the second pereiopods not being tuberculate (vs. dactylus exceeding fixed finger and tuberculated ventral margin in P. karantina sp. nov.). Periclimenaeus diplosomatis can be distinguished by the absence of an epipod on the second maxilliped and distolateral tooth of the scaphocerite exceeding anterior margin of the lamella (vs. with epipod and not exceeding in P. karantina sp. nov.). The new species also differs from P. myora and P. zarenkovi in the presence of a long carpocerite which exceeds the anterior margin of the scaphocerite (vs. not exceeding in P. myora and P. zarenkovi).

Periclimenaeus karantina sp. nov. most closely resembles P. colemani, with which it shares the carpocerite of the antenna exceeding the distal margin of the scaphocerite, and the scaphocerite with the lamella exceeding the distolateral tooth. The new species can be distinguished from P. colemani on the basis of the combination of the following characters: 1) antennule with rounded distolateral tooth (vs. sharp distolateral tooth in P. karantina sp. nov.); 2) dactylus of the minor chela being about 2.8 times greater than the maximal depth (vs. about 2 times in P. karantina sp. nov.); 3) dactylus of minor second pereiopod not exceeding fixed finger (vs. exceeding in P. karantina sp. nov.); 4) major and minor second pereiopods with cutting edge of dactyli with about 20 and 25 teeth, respectively (vs. with about 50 and 40 teeth in P. karantina sp. nov.); 5) fifth pereiopod propodus without distoventral spiniform setae (vs. single stout distoventral and single subdistal spiniform seta in P. karantina sp. nov.); 6) non-tuberculate ventral margin of merus of second pereiopods (vs. tuberculate ventral margin in P. karantina sp. nov.); 7) sixth pleuron with acutely produced posterolaterally (vs. posterolateral angle rounded in P. karantina sp. nov.).