Kaviengella jeffkinchi, Šobáňová & Ďuriš, 2018

Šobáňová, Anna & Ďuriš, Zdeněk, 2018, Kaviengella jeffkinchi, a new genus and species of symbiotic shrimp (Crustacea: Decapoda: Palaemonidae) from Papua New Guinea, Zootaxa 4415 (1), pp. 118-134 : 125-130

Kaviengella jeffkinchi sp. n.

( Figs 1–5 )

Type material. Holotype: female, CL 1.45 mm, MNHN-IU-2014-894, Expedition KAVIENG 2014, Martha's Shoal, Kavieng Lagoon, N.W. New Ireland, Papua New Guinea, 23 Jun. 2014, stn. KB60, 02° 32.5' S – 150° 35.3' E, depth 20 m, bottom—sand and coarse rubble in gutter, brushed from of dead corals.

Description. Small shrimp of slender subcylindrical vermiform body shape ( Fig. 1 ).

Rostrum ( Fig. 2A, B ) greatly reduced, obsolescent, about 0.05 of CL, compressed, triangular in dorsal view, only slightly overreaching proximal border of eyestalk. Both apex and single small dorsal subterminal tooth acute, directed anteriorly. Ventral margin simple, nearly straight, unarmed. Carapace ( Figs 1 , 2A, B ) smooth, subcylindrical, without antennal, hepatic, supraorbital or epigastric spines. Orbits feebly developed, inferior orbital angle produced, acute. Anterolateral angle of carapace subrectangular, blunty rounded.

Pleon ( Fig. 1 ) long, slender, about 2.5 times longer than CL, pleonal segments smooth, glabrous, pleurae small, first four of them similar in size, not distinctly enlarged proximally, all broadly rounded. First pleonal segment without anterodorsal median lobe, third tergite not produced posterodorsally. Fifth pleonal segment with pleurae much smaller than those of more anterior segments. Fifth and sixth segment subequal in length, latter about twice longer than deep, about 0.3 of CL, with posteroventral angle expanded, broadly rounded, posterolateral angle small, blunty rounded.

Telson ( Fig. 2C–E ) about 1.6 times sixth pleonal segment length, about 0.5 of CL, long, slender, slightly more than 2 times longer than maximal telson width; lateral margins almost straight, feebly convergent posteriorly, dorsal surface with two pairs of dissimilar, strong submarginal spines, both situated close to anterior margin of telson—at about 0.08 and 0.22 of telson length from anterior margin; proximal pair longer and stronger than posterior one, about 0.23 of telson length, slightly corrugated, distal pair of dorsal telson spines smaller, about 0.15 of telson length, with tips slightly curved downwards; posterior margin ( Fig. 2C ) broadly rounded, without median process, about 0.5 (including lateral spines) of maximal telson width, with 5 posterior cuspidate setae, i.e. two pairs laterally from single median seta ( Fig. 2C–E ); lateral posterior setae subdorsal, very small, obsolescent, about 0.1 of intermediate setae length, intermediate setae and median seta well eveloped, very long, stout, with tips thin, elongate, strongly curved upwards, hooked; intermediate spines about 0.3 of telson length, 0.66 times length of single submedian spine; submedian spine longest, about 0.5 of telson length, non-setulose.

Eyes ( Figs 1 , 2A, B ) well developed, large, elongate, about 0.5 of CL, reaching middle of second segment of antennular peduncle and distal end of carpocerite; cornea well pigmented, large, globular, with diameter about 0.14 of CL, situated obliquely on stalk, occupying 1/3 of lateral margin of eye; small accessory pigment spot present dorsolaterally on posterior margin of cornea; eyestalk long, subcylindrical, slightly swollen proximally, about 2.75 times longer than maximal width.

Antennule ( Fig. 2F, G ) of normal form, with peduncle well extending beyond distal margin of cornea and carpocerite; basal segment of antennular peduncle long and narrow, tapering distally, more than 5 times longer than proximal width; stylocerite small, short, leaf-like, distally acute, reaching to about 0.25 of basal antennular segment length; statocyst normally developed, with statolith; lateral margin of basal segment angular proximally in front of stylocerite, almost straight distally terminating in acute distolateral tooth reaching almost to middle of intermediate segment; medial margin almost straight, without ventromedial tooth, elongate blunty rounded ridge present ventromedially instead; intermediate and distal segments of antennular peduncle normal, short, subequal, together measuring about 0.3 of proximal segment length; flagella broken, upper flagellum stouter, with only three elongated segments remaining, lower flagellum simple, filiform, with few elongated segments remaining.

Antenna ( Fig. 2A, H ) with basicerite dorsally and laterally unarmed; ischiocerite and merocerite normal; carpocerite of antennal peduncle subcylindrical, long, slender, slightly overlapping scaphocerite, exceeding proximal segment of antennular peduncle, 7–8 times longer than central width, flagella missing. Scaphocerite strongly bidentate, reaching distal margin of basal segment of antennular peduncle, failing to reach end of carpocerite, lamella devoid of setae, strongly tapering distally to acutely produced tip, lateral margin short, slightly sinuous, with distinct robust acute distolateral tooth placed at midlength of scaphocerite ( Fig. 2H ).

Mouthparts ( Fig. 3 ) from right side, and left maxillula, dissected. Mandible ( Fig. 3A–D ) with corpus elongate, without palp; incisor process well developed, narrow, strongly bidentate apically; molar process elongate, slender, apex subquadrate, surrounded by approximately 10 long slender spiniform teeth ( Fig. 3B–D ).

Maxillula ( Fig. 3E ) with distinctly bilobed palp, lower palp lobe rounded, with small tubercle bearing short seta, upper lobe strong, blunty acute distally; upper lacinia short and broad, dorsal margin slightly convex, distal margin with about 10 short, stout, simple spinules diminishing in size proximally, complemented with several simple, slender, short setae; lower lacinia long, ovoid, tapering distally, with distal margin bearing tuft of long, strong, simple terminal setae.

Maxilla ( Fig. 3F ) normal, with slender, distally tapering compressed palp of almost same length as basal endite, apex simple devoided of setae; basal endite long, simple, with blunty rounded apex covered with about 6 long marginal setae; coxal endite indistinct, obsolete; scaphognathite well developed, narrow, about 4 times longer than central width, lined with short marginal plumose setae.

First maxilliped ( Fig. 3G ) with palp about 6 times longer than central width, simple, with rounded apex bearing small tubercle with slender simple seta preterminally; basal endite feebly separated from coxal endite by shallow emargination, broad, ovate, medially and subdistally covered with tufts of long simple setae; coxal endite reduced but distinct, convex, cuspidate setae non-setose; exopod of first maxilliped narrow, short, with flagellum reduced to only one simple and one plumose seta placed terminally; caridean lobe well developed, long and broad, about 3 times longer than central width, subrectangular, covered with plumose setae marginally; epipod small, feebly bilobed, cordiform (lost in dissection).

Second maxilliped ( Fig. 3H ) stout, with endopod of normal form, dactylar segment of endopod moderately broad, about 2 times longer than maximal width, with distomedial margin slightly convex, covered with numerous stout simple setae; propodal segment narrow, with distomedial margin not produced, bearing several stout simple setae, similar to those of dactylar segment; carpus and merus short, subtriangular from side; ischium completely fused to basis, combined segment short, without special features; coxa medially produced, rounded, bearing small short simple seta; exopod well developed, slender, with approximately 4 plumose, terminal setae; epipod small, simple, suboval, without podobranch.

Third maxilliped ( Fig. 3I ) normally developed, slender; terminal segment stout, tapering distally, about 0.7 of penultimate segment length, 2.0 times longer than basal width, with rows of setae distributed medially and ventrally; penultimate segment subcylindrical, about 0.4 of ischiomerus and basis length combined, 2.4 times longer than central width, slightly swollen and covered with simple setae medially; ischiomerus and basis completely fused, sutures feebly demarcated, ischiomerus slender, subcylindrical, more than 4 times longer than proximal width, lateral margin straight, distal margin with row of long simple setae, medial margin with distinct suture proximally on meral part of combined segment, medial margin distally with scattered marginal setae; basis broadly rounded medially; exopod well developed but failing to reaching distal end of ischiomerus, with 4 long plumose terminal setae; coxa stout, not produced medially, with lateral plate obsolete, without arthrobranch.

First pereiopods ( Figs 4A , 5A–C ) moderately stout, similar, equal, overreaching carpocerite by distal half of carpus. Chela ( Fig. 5A–C ) about 0.28 of CL, palm short, subquadrate from side, about as long as deep, slightly compressed, with distinct longitudinal furrow in centre of medial side, dorsal side broadly convex in lateral aspect and rounded from apical aspect, ventral margin sinuate with broad concavity in midlength of palm, propodal part of carpo-propodal brush lacking; fingers occupying amost two thirds of chela length. Movable finger about 2 times longer than maximal depth, exceeding fixed finger, deeply spatulate, laterally broadly expanded, distally rounded, medially feebly expanded, all latter margins finely denticulate thoughout, medial denticles stronger but less dense, diminishing proximally ( Fig. 5A–C ); upper surface with few long, slender setae. Fixed finger short, failing to reach distal end of movable finger, about 3 times longer than proximal depth, subriangular from side, tapering strongly distally, tip armed with three strong acute spiniform teeth projecting distally, distodorsal margin of fixed finger with series of about 8 strong but smaller acute teeth diminishing proximally ( Fig. 5B–C ), ventral surface of fixed finger convex, with transverse rows of several long, slender setae. Carpus subcylindrical, tapering proximally, about 2.5 times longer than distal width, 0.9 times of chela length, distoventral margin with row of cleaning setae; merus subcylindrical, slightly swollen proximally, about 6 times longer than distal width, about 1.2 times chela length, 1.3 times longer than carpus, unarmed; ischium short, about 0.6 of merus length, subcylindrical, about 4 times longer than distal width, unarmed, with distinct transverse ridge situated ventrally on proximal half of ischium; basis and coxa normal, short, without special features.

Both second pereiopods missing, details of their shape unknown; coxae with bases intact, their unequal sizes indicating unequal size of second pereiopods.

Ambulatory pereiopods ( Fig. 4B–H ) normal, smooth, dissimilar in size, third pereiopods ( Fig. 4B–E ) moderately robust, fourth legs detached, lost, fifth pereiopods ( Fig. 4F–H ) slender. Dactylus of third pereiopod stout, about 0.3 of propodus length, corpus compressed, 1.75 times longer than proximal depth, strongly tapering distally, dorsal margin feebly convex, ventral margin armed with small acute distoventral accessory tooth at distal third of ventral length of corpus, corpus bearing single seta distally on both sides of corpus; propodus about 0.3 of CL, subcylindrical, slightly compressed, 3.5 times longer than dactylus length, about 4.4 times longer than central depth, with few setae distodorsally on propodus, ventral border straight, distoventral angle with pair of short acute distoventral spines about 0.3 of dactylus length, one short ventral spine more posteriorly at 0.7 of propodus length from proximal end; carpus about 0.8 of propodus length, stout, 3 times longer than distal depth, unarmed, dorsal marin convex; merus robust, subcylindrical, slightly compressed, dorsal and ventral margins broadly convex, about 1.2 of propodus length, 2.8 times longer than central width, unarmed; ischium about 0.75 of propodus length, 2 times longer than central width, unarmed; basis and coxa normal, without special features. Fifth pereiopods ( Fig. 4F–H ) similar to third but shorter and distinctly more slender, dactylus similar to that of third pereiopod but smaller, ventral accessory tooth on corpus smaller, distoventral pair of spines as well as ventral spine placed posterior to distoventral spines small, reduced in size.

Uropod ( Fig. 2C, I, J ) extending beyond distal margin of telson; protopodite simple, unarmed; exopod about twice as long as maximal width, lateral margin almost straight, sparsely covered with short setae, ended in long and robust, depressed, slightly medially curved distolateral lobe far overreaching lamina, about 0.2 of exopod length, with movable spine medially, about half of distolateral lobe length ( Fig. 2I ), movable spine lost on right exopod ( Fig. 2J ); distal lamella reduced, margin truncate, diaeresis lacking; endopod normal, ovate, 2.2 times longer than broad, about 1.2 times exopodal lamella length.

Measurements. Female holotype: total body length 5.8 mm; postorbital carapace length (CL) 1.45 mm; carapace and rostrum length 1.61 mm; first pereiopod chela length 0.38 mm.

Etymology. The new species is dedicated to Dr Jeff Kinch, Principal of Papua New Guinea National Fisheries Authority's National Fisheries College in Kavieng. Dr Kinch was a co-Principal Investigator of the KAVIENG 2014 marine biodiversity expedition hosted at the Nago Island Mariculture and Research Facility (NIMRF), during which many new species of fish and invertebrates were discovered.

Coloration. Unknown.

Host. The host of K. jeffkinchi gen. & sp. n. is unknown. Based on general morphological similarity to several sponge-associated shrimps, it is likely also a spongobiont.

Distribution. Presently known only from the type locality, New Ireland, Papua New Guinea.

Remarks. The second pereiopods are lost in the single available specimen, thus the details of their shape remain unknown. As the remaining proximal segments, still attached to the body, are unequal in size on the left and right sides, the second pereiopods evidently were distinctly unequal in size too. Such unequal second pereiopods are present in most of sponge endosymbiotic palaemonids (e.g. Fujino & Miyake 1968; Bruce & Bauer 1997; Bruce 1970b, 1995).

Besides the genus Nippontonia (see Systematic position, above), reduced scaphocerites are also typical for other sponge-associated genera, e.g. Onycomenes Bruce , Typton Costa, Typtonoides , or Typtonychus Bruce , but in those genera are rudimentary or small (e.g. Bruce 1995, 2009, 2010b, 2011), instead of large, acutely produced, with reduced non-setose lamella in Nippontonia and the new genus. The antennal carpocerite is longer than the scaphocerite in the new genus as well as in Typton spp., but is distinctly shorter in Nippontonia (e.g. Bruce & Bauer 1997; Bruce 2014; Fransen 2013).

Kaviengella jeffkinchi gen. & sp. n. is easily distinguishable from other palaemonid genera by the unusual shape of chelae of the first pereiopod with the spoon-like dactylus and its marginal denticulation. In general, spatulate and denticulate dactyli of chela of the first pereiopods have been also described for some Periclimenaeus species, e.g. the IWP P. rastrifer Bruce, 1980 and P. tchesunovi Ďuriš, 1990 , and remarkably developed in the western Atlantic P. pectinidactylus Ďuriš, Horká & Sandford, 2009 . However, in all these species both fingers of the first pereiopods (dactylus and fixed finger) are similarly shaped and subequal (Bruce 1980a; Ďuriš 1990; Ďuriš et al. 2009), not strongly unequal and dissimilar as in K. jeffkinchi gen. & sp. n. The lateral denticulate expansion of the dactylus is somewhat similar to that of the spongobiotic genus Periclimenoides Bruce , but medial sides of dactyli in that genus are simple, with fixed fingers subequal to the dactyli and hooked apices. Periclimenoides spp. have normally developed dentate rostrum, antennal scaphocerite as well as more conventional telson and uropodal exopod ornamentation (Bruce 1990; Šobáňová et al. 2017). Spatulate and denticulate dactyli are also known in species of echinoderm-associated genus Zenopontonia Bruce (Bruce 1975, 1995; Marin 2012a), and in the freeliving, occasionally coral-associated, species of the genera Exoclimenella Bruce and Periclimenella Bruce (Ďuriš & Bruce 1995) . Asides from cleaning of their body, the first pereiopods are generally used by palaemonid shrimp for collecting small-sized food particles, detritus and mucus; specifically, the spongobiotic shrimps potentially feed predominantly on soft sponge tissues (Ďuriš et al. 2011). The peculiar shape of chelae of the first pereiopods is very probably related to a similar function in K. jeffkinchi gen. & sp. n.

The curved and anteriorly closely set pairs of the dorsal telson spines are rarely present in Indo-West Pacific species, clearly systematically unrelated, e.g. in the spongobiotic Periclimenaeus djiboutensis Bruce, 1970 , the bivalve mollusc endosymbiotic Anchiopontonia hurii ( Holthuis, 1981) , the ascidian associated Cainona medipacifica ( Edmondson, 1935), and the Atlantic spongobiotic Typton serratus Holthuis, 1951 (e.g. Bruce 1970b, 1980b; Holthuis 1951, 1981; Fransen 2002). However, it is the posterior telson ornamentation of Kaviengella jeffkinchi sp. nov. which is (if confirmed in wider series of specimens in the future) without parallel among palaemond shrimps. Composed of five cuspidate setae, their lateral and intermediate setae are normally paired, but the median seta is single, non-setulose, extremely long, and strongly hooked dorsally, similarly to the intermediate setae which also are long and hooked, but distinctly shorther than the median seta. Three pairs of those setae are normally present in the majority of palaemonids, with the intermediate ones longest, and the submedian ones setulose on sides; their variation is reviewed by De Grave et al. (2015). Among most remarkable exceptions are species of the genera Hamopontonia Bruce and Yemenicaris Bruce with greatly modified posterior telson margin with the marginal setation reduced to only a pair of lateral ones, and with ventrally curved V-shaped (former), or broadly rounded (latter), posterior margin (Bruce 1970a, 1997; Marin 2012b; Ďuriš 2017). Both these genera are coral-associated, and can be easily distinguished from Kaviengella gen. nov. by a well-developed dentate rostrum, and more conservative shape of chelae of the first pereiopods.

Figures

FIGURE 1. Kaviengella jeffkinchi gen. & sp. n. female holotype, habitus, lateral aspect.

FIGURE2. Kaviengella jeffkinchigen.& sp.n.,female holotype. A, anterior carapace and antennae, dorsal.B, same, lateral. C, posterior sixth pleonal segment, telson, and left uropod, dorsal. D, telson, lateral. E, distal endo of telson, dorsolateral. F, right antennule, dorsal. G, same, lateral. H, left antenna, ventrolateral.I, distolateral angle of exopod of right uropod, dorsal. J, same, right uropod.

FIGURE 3. Kaviengella jeffkinchi gen. & sp. n., female holotype, mouthparts (from left side, except maxillula). A, mandible, inner aspect.B, same, outer aspect.C, distal end of molar process.D, same, outer aspect. E, maxillula. F, maxilla.G, first maxilliped.H, second maxilliped. I, third maxilliped.

FIGURE 4. Kaviengella jeffkinchi gen. & sp. n., female holotype. A, right first pereiopod, lateral. B, right third pereiopod, lateral. C, same, distal segments. D, same, distal propodus and dactylus, lateral. E, same, ventromedial. F, fifth pereiopod, lateral.G, same, distal segments. H, same, dactylus and distal propodus, lateral.

FIGURE 5. Kaviengella jeffkinchi gen. & sp. n., female holotype. A, right first pereiopod, chela and distal propodus, lateral. B, left first pereiopod, chela and distal propodus, medial.C, same, ventromedial.