Rhynchocinetes Rathhunae, a New Shrimp from the Hawaiian Islands (Crustacea: Decapoda: Rhynchocinetidae)L

Rhynchocinetes rathhunae, a New Shrimp from the Hawaiian Islands (Crustacea: Decapoda: Rhynchocinetidae)l

JUNn OKUN0 2

ABSTRACT: A new species of caridean shrimp of the family Rhynchocineti dae, Rhynchocinetes rathbunae Okuno, is described and illustrated based on six males, an ovigerous female, a second female, and a juvenile from the Hawaiian Islands. It is closely related to R. brucei Okuno from the tropical western Pacific and R. rugulosus Stimpson from southern Australian waters, but is readily dis tinguishable from the two latter species by absence of a podobranch on the second maxilliped, the longer rostrum, forms of the stylocerite and endopod of male first pleopod, meral dentition of the ambulatory pereiopods, and the color in life.

IN THE ORIGINAL DESCRIPTION of Rhynchoci Rhynchocinetes rugulosus: Rathbun, 1906, netes brucei Okuno, 1994, it was suggested 911, fig. 64; Edmondson, 1952,70 (in part), that another Hawaiian rhynchocinetid shrimp fig. 2 (not Stimpson, 1860). in the collections ofthe B. P. Bishop Museum, ? Rhynchocinetes rugulosus: Edmondson, Honolulu, Hawai'i, might be an undescribed 1925, 6; Hiatt, 1948, 79 (not Stimpson, species. Through the courtesy of L. G. El 1860). dredge, I examined the specimens in question during a short visit to the museum. In addi TYPE MATERIAL: Holotype: Male (BPBM tion, John Hoover, an underwater photogra S11275, 7.0 rom CL), Hawaiian Islands, pher in Honolulu, kindly sent me some speci O'ahu, Waimea Bay, 21 0 38.0' N, 158 0 04.0' mens of the shrimp captured at Waimea Bay W, 29 November 1994, colI. J. Hoover and and Hanauma Bay, O'ahu. This shrimp re J. Earle. Paratypes: 1 male (BPBM S11276, sembles R. brucei and R. rugulosus Stimpson, 11.6 rom CL) and 1 ovigerous female (BPBM 1860, but differs in morphology and the SI1277, 8.0 rom CL), Hawaiian Islands, life color, and I describe it here as new to O'ahu, Kahe Pt., 21 0 20.0' N, 158 0 11.0' W, 4 science. Abbreviations are as follows: CL: February 1977; 3 males (NSMT Cr 2420, 11.3, postorbital carapace length; BPBM: Bernice 6.9, and 6.3 mm CL), same data as holotype; P. Bishop Museum, Honolulu, Hawai'i; CBM: 1 female (CBM ZC 1964, 4.7 mm CL), Ha Natural History Museum and Institute, waiian Islands, O'ahu, Hanauma Bay, 21 0 Chiba, Japan; NSMT: National Science Mu 16.3'N, 15]0 42.0' W, 25 June 1995, colI. J. seum, Tokyo, Japan; NTM: Northern Terri Hoover; ajuvenile (USNM 31008, 2.4 rom CL), tory Museum, Darwin; USNM: National French Frigate Shoals, 17 -17~ fathoms (31 Museum of Natural History, Smithsonian 32 m) depth, colI. Steamer Albatross. OTHER Institution, Washington, D.C. MATERIAL EXAMINED: male (NSMT Cr 11104, 8.6 rom CL), Hawaiian Islands, exact collec Rhynchocinetes rathbunae Okuno, n. sp. tion site unknown, colI. aquarium traders. Figures 1-3, Tables 1,2 DESCRIPTION: Body subcylindrical, typical form of Rhynchocinetes. Carapace (Figure lA) covered with fine transverse striae, armed with two acute spines on median carina, an 1 Manuscript accepted 25 October 1995. 2 Natural History Museum and Institute, Chiba, 955-2 terior spine just behind rostral articulation, Aoba-cho, Chuo-ku, Chiba 260, Japan. posterior spine feebly articulated with car- 309 B

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apace; supraorbital spine acute, directed an distally, with sparse long setae. Maxillula teriorly; antennal spine pointed, supported (Figure 2B) with slender palp with dentic by feeble carina, directed anteriorly, extend ulate long seta distally; upper lacinia broad, ing beyond tip of supraorbital spine; ptery with two rows of stout distal spines; lower gostomial angle with a small acute spine. lacinia slightly larger than the upper, with Rostrum (Figure IB) articulated with car numerous spiniform distal setae. Maxilla apace, 1.3-1.6 times as long as carapace; (Figure 2C) with slender palp; coxal endite dorsal margin armed with two teeth prox marginally oblique; distal endite bilobed, up imally, five to six small teeth subterminally; per lobe distally rounded, slightly broader ventral margin armed with 12-13 teeth. than the lower, lower lobe with indistinctly Abdominal somites (Figure I C) covered bilobed distal margin; scaphognathite well with fine striae; first three somites with developed, anterior lobe with slightly rounded pleurae marginally rounded; sixth somite distal end, posterior lobe slender, elongate, 0.5-0.7 times as long as carapace, 1.8-2.0 directed posteriorly, inner margin with con times as long as its distal depth, with an acute vex lobe proximally. First maxilliped (Figure posteroventral spine; an acute anal spine be 2D) with elongate, two-segmented palp with tween bases of uropods. Telson (Figure ID) rounded distal end; proximal endite smaller 0.6-0.8 times as long as carapace, 1.2 times than the distal, slightly rounded marginally; as long as sixth abdominal somite, armed distal endite with distal margin concave; dorsally with three pairs of spines, the first exopod well developed, caridean lobe large, pair at proximal two-fifths and the third pair flagellum slender; epipod bilobed, with feebly at distal fifth; midpoint of posterior margin pointed distal margin. Second maxilliped prominent, with three pairs of spinules, me (Figure 2E) without podobranch; epipod dian pair longest. pointed distally, with the undivided, slightly Eye well developed, with large, globular triangular remains of a podobranch on upper cornea; stalk much more slender than cornea. margin proximally; dactylar segment with Antennular peduncle (Figure IE) reaching truncate distal margin; propodal segment about to midlength of scaphocerite; stylocer broad, distomedial margin expanded; carpal ite long, reaching proximal third of distal segment with slightly convex distal end of segment; proximal segment with distolateral outer margin. Third maxilliped (Figure 2F) spine falling slightly short of distal margin of slightly overreaching tip of scaphocerite; ul median segment, ventrally with an acute tooth timate segment 0.5-0.7 times as long as car at inner margin. apace, 1.7-1.9 times as long as penultimate Scaphocerite (Figure IF) 0.8-1.0 times as segment, with six dark corneous spines dis long as carapace, 3.6-4.3 times as long as tally; penultimate segment 0.3-0.4 times as maximum width, outer margin slightly con long as carapace; antepenultimate segment cave distally; distolateral spine acute, exceed with a row of sparse setae laterally, with an ing end of lamella; basicerite with an acute acute distolateral spine; exopod well devel ventrodistal spine and with rounded lobe just oped, falling slightly short of distal margin of above spine. antepenultimate segment. Mandible (Figure 2A) with three-seg Branchial formula as shown in Table I. mented palp, distal segment rounded, with First pereiopod (Figure I G) chelate, mod dense setae marginally; incisor process stout, erately robust, falling slightly short of mid distal margin truncate, with blunt teeth; mo length of scaphocerite; chela 0.4-0.5 times as lar process subcylindrical, obliquely truncate long as carapace, 1.6-2.0 times as long as

... FIGURE I. Rhynchocinetes rathbunae, n. sp., holotype male (BPBM SI1275): A, carapace and cephalic appendages; B, anterior part of carapace with rostrum; C, fourth to sixth abdominal somites; D, telson; E, antennular peduncle, ventral view; F, scaphocerite (setae omitted); G, first pereiopod; H, second pereiopod; I, third pereiopod; J, dactylus of third pereiopod; K, endopod of first pleopod; L, second pleopod; M, uropod (setae omitted). Scales: A, 2.5 mm; B, C, F, I, 2.0 mm; D, E, G, H, L, M, 1.0 mm; J, K, 0.5 mm. A

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A- E

FIGURE 2. Rhynchocinetes rathbunae, n. sp., paratype male (BPBM SI1276): A, mandible; B, maxillula; C, maxilla; D, first maxilliped; E, second maxilliped; F, third maxilliped. Setae omitted on C, 0, E. Scales: A-E, 1.0 mm; F, 5.0 mm. New Shrimp from the Hawaiian Islands-OKuNo 313

TABLE 1 with four to five (rarely three) equidistant

BRANCHIAL FORMULA OF acute spines; dentition and proportion of Rhynchocinetes rathbunae. N. SP. carpus resembling those of fourth pereiopod; propodus 0.5-0.7 times as long as carapace, MAXILLIPEDS PEREIOPODS 1.6-1.9 times as long as carpus. Endopod of male first pleopod (Figure 2 3 2 3 4 5 IK) with distal end slightly pointed; devel Pleurobranch oped appendix interna attaches midlength Arthrobranch 2 of inner margin, with numerous granules Podobranch distally; small lobe at distal third of outer Epipod margm. Exopod Endopod of male second pleopod (Figure IL) with appendices masculina and interna attached at distal two-fifths of outer margin; carpus, tips of both fingers with dark claws; appendix masculina broad, rounded, fringed carpus 0.2-0.3 times as long as carapace, with dense setae; appendix interna consid with dorsal margin distally pointed; merus erably more slender than appendix mascu 1.6-1.8 times as long as carpus, with an lina, with numerous granules distally. acutely pointed spine at distal end of dorsal Uropodal endopod and exopod (Figure margm. 1M) overreaching tip of telson; exopod with Second pereiopod (Figure 1H) chelate, an articulated spine and a nonarticulated more slender than first pereiopod, slightly spine at distal fourth of outer margin, the overreaching midlength of scaphocerite; former much longer than the latter. chela 0.3-0.4 times as long as carapace; car COLORATION: Ground color of body gen pus 0.4-0.5 times as long as carapace, 1.2 erally transparent pink, carapace and first to 1.4 times as long as chela. fifth abdominal somites with labyrinth red Third pereiopod (Figure 1I) overreaching lines, interspaced with white dots and lines. scaphocerite by propodal apex; ischium with Rostral tip white. Third abdominal somite an acute spine; merus 0.7-0.9 times as long dorsally with a distinct, rounded (rarely as carapace, 2.2-2.5 times as long as carpus, oblong) median spot, sixth somite with lon with four to six almost equidistant acute gitudinal red lines extending to posterior spines; carpus 0.3-0.4 times as long as car margin of third somite. First and second apace, with two acute spines on outer sur pereiopods mottled with red and white. face; propodus 0.6-0.8 times as long as car Ambulatory pereiopods with meri with red apace, 1.9-2.0 times as long as carpus, with bands and carpi and propodi with red lines at short equidistant spinules on flexor margin; the margin. dactylus (Figure IJ) with three accessory spines on flexor margin, decreasing in size DISTRIBUTION: Known only from the Ha proximally. waiian Islands. It is usually found in the lit Fourth pereiopod reaching distal third toral zone (J. Hoover, pers. comm.). of scaphocerite, dentition resembling that of ETYMOLOGY: This species is named in third pereiopod; merus 0.7-0.9 times as long honor of Mary J. Rathbun (1860-1943), who as carapace, 2.1-2.2 times as long as carpus; originally suggested (1906) that a Hawaiian carpus 0.3-0.4 times as long as carapace; Rhynchocinetes was an undescribed species. propodus 0.6-0.8 times as long as carapace, 1.7-2.0 times as long as carpus. REMARKS: The juvenile paratype was re Fifth pereiopod reaching proximal third of corded as Rhynchocinetes rugulosus by Rath scaphocerite, dentitions of ischium and dac bun (1906). Its rostrum is armed dorsally tylus resembling those of third and fourth with four teeth distally and ventrally with 10 pereiopods; merus 0.6-0.7 times as long as teeth decreasing in size distally. Rathbun's carapace, 1.7-2.0 times as long as carpus, illustration is incorrect because the proximal 314 PACIFIC SCIENCE, Volume 50, July 1996

FIGURE 3. Rhynchocinetes rathbunae, n. sp., non type male (NSMT Cr 11104): Specimen alive in aquarium. four teeth are distinctly smaller than the segment, which is distinctly longer (1.1 times other teeth. The remarkable difference be the length of the carapace and 3.3 times the tween the juvenile and the other specimens is length ofthe penultimate segment) than those the length of the stylocerite, which reaches of the other specimens. The first pereiopod the distal margin of the proximal antennular reaches the distal fifth of the scaphocerite, segment but not as far as the tip of the dis and its chela is 0.6 times as long as the car tolateral spine of the segment. The unusual apace and 2.3 times as long as the carpus. length of the structure may represent intra specific variation during development. DISCUSSION: The genus Rhynchocinetes One of the male paratypes (BPBM SII276, s.l. is divided into two subgenera, Rhyncho 11.6 mm CL) has the telson armed dorsally cinetes H. Milne Edwards, 1837, and Cineto with four and two dorsal spines on the left rhynchus Holthuis, 1995 (Holthuis 1995). The and right sides, respectively, and its posterior former consists of 10 described species and margin is armed with three pairs of spinules the latter of 5 species (Okuno 1993, 1994a,b). and an extra spinule on the left side. The The new species belongs to the subgenus form of the telson in this specimen is prob Rhynchocinetes, having distinct rostral artic ably abnormal; the other specimens are con ulation, a supraorbital spine, two spines on sidered to represent the typical form of the the median carina of the carapace, and no genus. posterolateral tergal spines on the fourth and The third maxilliped and the first pereio fifth abdominal somites. It closely resembles pod of the large male (11.3 mm CL) are dis R. brucei Okuno, 1994, and R. rugulosus tinctly different from those features in the Stimpson, 1860 [=R. serratus (H. Milne females. The third maxilliped overreaches Edwards, 1837) ?] in the number of arthro the scaphocerite by one-half of the ultimate branchs and the presence of a lobe on the New Shrimp from the Hawaiian Islands-OKuNo 315

TABLE 2

COMPARISON OF CHARACTERS OF Rhynchocinetes rathbunae. N. SP. AND Two RELATED SPECIES

R. rathbunae R. brucei R. rugu/osus

Rostrum/Carapace 1.3-1.6 1.1-1.3 1.1-1.2 Stylocerite Overreaching distal Not reaching distal margin Overreaching distal margin of 2nd of 2nd antennular margin of 2nd antennular peduncle* peduncle antennular peduncle Podobranch on 2nd Absent Present Present maxilliped Meral spines 3rd pereiopod 4-6 (usually 5) 3 3-4 4th pereiopod 5 (rarely 4) 3 (rarely 4) 3 5th pereiopod 4-5 (rarely 3) 2-4 (usually 3) 3 Lobe on male 1st pleopodal Indistinct; at distal third Indistinct; at distal third of Distinct; at midlength of endopod of outer margin outer margin outer margin Median spot on 3rd Present Present Absent abdominal somite

• Not present on the juvenile paratype. outer margin of the male first pleopod. along the coasts of Peru and Chile (Holthuis Specimens of R. rathhunae were compared 1980). Of the two tropical species, R. durba with the type series of R. brueei and two nensis Gordon, 1936, is widely distributed in males (NTM Cr 000343, 5.8 and 5.2 mm CL) the Indo-West Pacific from the eastern coast and an ovigerous female (NTM Cr 003616, of Africa to the Ryukyu Islands, and R. bru 12.0 mm CL) of R. rugulosus. The differences eei is known from the tropical western Pacific among the three species are summarized in but they have not been recorded from the Table 2. The most conspicuous diagnostic oceanic islands of the central Pacific (Okuno character of R. rathbunae is the absence of and Takeda 1992b, Okuno 1993, 1994a). The the podobranch on the epipod of the second remaining species, R. ikatere Yaldwyn, 1971, maxilliped; in the other two species, a small is known only from deep waters off New podobranch occurs on the maxilliped. Zealand at depths of 80-120 fathoms (146 Rhynehocinetes rathbunae seems to be en 220 m) (Yaldwyn 1971). demic to the Hawaiian Islands, and its dis Previous authors have recorded a rhyn tributional range does not appear to overlap chocinetid species identified as R. rugulosus with those of the other 10 species belonging from several localities in the Hawaiian Is to the subgenus Rhynehocinetes. The dis lands: French Frigate Shoals (Rathbun 1906), tributions of the temperate and subtropical Laysan Island (Edmondson 1925), and off Rhynehoeinetes species suggest that the range O'ahu (Hiatt 1948, Edmondson 1952). I could of each species is limited locally as follows: only re-examine the specimens recorded by R. australis Hale, 1941, R. kuiteri Tiefen Rathbun (1906) and Edmondson (1925). The bacher, 1983, and R. rugulosus in southern specimen collected from Laysan Island (BPBM Australian waters (Hale 1941, Tiefenbacher 1270,3.7 mm CL) is dried and damaged, and 1983, Okuno 1994a); R. balssi Gordon, 1936, the other specimens from the Hawaiian Is in the southeastern Pacific from Juan Fer lands have been lost. Although their taxo mindez to Lord Howe Islands (Gordon 1936, nomic status was not determined morpho Holthuis 1972, Bruce 1985); R. eonspieio logically, the distributional patterns discussed eellus Okuno & Takeda, 1992, and R. uritai above suggest that the Hawaiian specimens Kubo, 1942, in central to southern Japanese previously recorded may be identical with R. waters (Kubo 1942, Okuno and Takeda rathbunae, except for the specimen illustrated 1992a); R. typus H. Milne Edwards, 1837, by Edmondson (1952, fig. 2), which without 316 PACIFIC SCIENCE, Volume 50, July 1996 doubt can be referred to R. rathbunae be ---. 1995. Notes on Indo-Pacific Crusta cause of the five meral spines on the fourth cea Decapoda III to IX. Zool. Meded. pereiopod. (Leiden) 69: 139-151. KUBO, I. 1942. On two new species of De capoda Macrura. Annot. Zool. Jpn. 21: ACKNOWLEDGMENTS 30-38. OKUNO, J. 1993. First record of a hinge-beak I express my sincere gratitude to L. G. shrimp, Rhynchocinetes durbanensis Gor Eldredge for his kind support during my visit don, 1936 from Japan. Izu Ocean. Park to the Bernice P. Bishop Museum and to J. Div. News (43): 2-5. (In Japanese with Hoover for kindly donating to me the speci English abstract). mens of the new species captured from ---. 1994a. A new species of hinge-beak O'ahu. I also thank A. J. Bruce for arranging shrimp from the western Pacific (Crusta the loan of materials for comparison and M. cea, Decapoda, Rhynchocinetidae). Bea Takeda for his helpful comments on the gle, Rec. North. Territ. Mus. Arts Sci. 11: manuscript. I am deeply indebted to F. A. 29-37. Chace, Jr., for sending me the Rathbun ---. 1994b. Rhynchocinetes conc%r, a specimen on loan and for critically reading new shrimp (Caridea: Rhynchocinetidae) the manuscript. from the Indo-Pacific. Proc. Jpn. Soc. Syst. Zool. (52) : 65-74. OKUNO, J., and M. TAKEDA. 1992a. Descrip tion of a new hinge-beak shrimp, Rhyn LITERATURE CITED chocinetes conspiciocellus, from southern BRUCE, A. J. 1985. Caridean shrimps from Japan, with designation ofthe lectotype of Lord Howe Island. Beagle, Occas. Pap. R. uritai Kubo, 1942. Bull. Natl. Sci. Mus. North. Territ. Mus. Arts Sci. I: 123-130. ser. A 18: 63-72, 1 pI. EDMONDSON, C. H. 1925. Crustacea of trop ---. 1992b. Distinction between two ical central Pacific. Marine zoology of hinge-beak shrimps, Rhynchocinetes dur tropical Central Pacific. (Tanagar Expedi banensis Gordon and R. uritai Kubo tion Publication No.1). Bull. B. P. Bishop (Family Rhynchocinetidae). Rev. Fr. Mus. 27: 3-26. Aquariol. 19: 85-90. ---. 1952. Additional Central Pacific RATHBUN, M. J. 1906. The brachyura and crustaceans. Occas. Pap. B. P. Bishop macrura of the Hawaiian Islands. Bull. Mus. 21 : 67-86. U.S. Fish Comm. 23: 827-930, pis. 3-24. GORDON, I. 1936. On the macruran genus STIMPSON, W. 1860. Prodromus descriptionis Rhynchocinetes with the description of a animalium evertebratorum, quae in Ex new species. Proc. Zool. Soc. Lond. 1936: peditione ad Oceanum Pacificum Septen 75-88. trionalem, a Republica Federate missa, C. HALE, H. H. 1941. Decapod Crustacea. Br. Ringgold et J. Rodgers Ducibus, obser N. Z. Antarc. Res. Exp. Rep. ser. B 4: vavit et descripsit. Proc. Acad. Nat. Sci. 257-285, 1 pI. Phil. 1860: 22-48. HIATT, R. W. 1948. Records of rare Hawai TIEFENBACHER, L. 1983. A new species of ian decapod crustacea. Pac. Sci. 2: 78-80. Rhynchocinetes from South-Australia HOLTHUIS, L. B. 1972. The Crustacea De (Crustacea, Decapoda, Rhynchocineti capoda Macrura (the Alpheidae excepted) dae). Rev. Fr. Aquariol. 9: 121-124. of Easter Island. Zool. Meded. (Leiden) YALDWYN, J. C. 1971. Preliminary descrip 46: 29-54, 2 pis. tions of a new genus and twelve new spe ---. 1980. FAO species catalogue. Vol. 1, cies of natant decapod crustacea from Shrimps and prawns of the world. An an New Zealand. Rec. Dom. Mus. (Well notated catalogue of species of interest to ington) 7 : 85-94. fisheries. FAO Fish. Synop. (125): 1-271.