A New Species of Crangonid Shrimp ofthe Genus Philocheras (Crustacea: Decapoda: Caridea) from Hawai'F Tomoyuki KomaiZ Abstract: Philocheras breviflagella, a new species of crangonid shrimp, is de­ scribed and illustrated on the basis of a single ovigerous female collected from O'ahu, Hawai'i, at subtidal depth. The new species is most similar to P. sabse­ chota (Kemp, 1911) known with certainty only from the Andaman Islands, east­ ern Indian Ocean. It differs from P. sabsechota in several features, including the much narrower rostrum, the unarmed second lateral carina of the carapace, and the truncate posterior margin ofthe uropodal exopod. Other differences include the shorter fingers (each with an elongate unguis) of the second pereopod, and medially notched posterodorsal margins of the second and fourth abdominal somites. The new species is the first representative of the genus found to occur in the central Pacific. THE GENUS Philocheras Stebbing, 1900, is the During an ongoing study of Crangonidae most speciose among the Crangonidae, in­ in the Indo-Pacific, a small ovigerous speci­ cluding nearly 50 species worldwide (de Man men from O'ahu, Hawai'i, was made available 1920, Holthuis 1951, 1961, Yaldwyn 1960, for study by Dr. P. K L. Ng of the National 1971, Zarenkov 1968, Crosnier 1971, Fujino University of Singapore. Detailed examina­ and Miyake 1971, Dardeau 1980, Chace tion has shown that this specimen represents 1984, Wicksten 1989, Burukovsky 1990a,b, a distinct undescribed species of Philocheras. Bruce 1994, De Grave 2000, Kim and Hay­ Although only a single specimen was available ashi 2000). Although Kemp (1911) synony­ for examination, its distinctiveness has led me mized Philocheras with Pontophilus Leach, to describe it as a new species, P. breviflagella. 1817, the genus was revived on the basis of This new species represents the first record of the laterally unarmed rostrum, the absence of Philocheras in the central Pacific. a postorbital suture on the carapace, and the The holotype is deposited in the Raffles absence of an exopod on the first pereopod Museum of Biodiversity Research, National (Chace 1984). Christoffersen (1988) showed University of Singapore (ZRC). The abbrevia­ that Philocheras is a clade, characterized by tion "cl" indicates postorbital carapace one autapomorphy (the antennular stylocerite length. The drawings were made with the aid is transversely oblong) and one homoplasy of a drawing tube mounted on a stereo­ (the exopod is absent from the first pereo­ microscope (Leica MZ8). pod). Philocheras is well represented in the Indo-West Pacific by 19 species, but there TAXONOMIC ACCOUNT has been no record of the genus from the central Pacific, including Hawai'i. Philocheras breviflagella Komai, n. sp. Figures 1-3 MATERIAL EXAMINED: Holotype: Ala 1 Manuscript accepted 7 February 2001. Moana, O'ahu, Hawai'i, subtidal, 22 Decem­ 2 Natural History Museum and Institute, Chiba, 955-2 Aoba-cho, Chuo-ku, Chiba 260-8682, Japan ber 1999, colI. D. Takaoka, ovigerous female (E-mail: [email protected]). (cl 2.6 mm) (ZRC 2000.0369). DESCRIPTION: Body (Figure lA,B) robust, slightly flattened dorsoventrally. Integument Pacific Science (2001), vol. 55, no. 4:419-427 of carapace and abdomen microscopically © 2001 by University of Hawai'i Press pitted, with scattered short (curled) or long All rights reserved (plumose) setae. 419 420 PACIFIC SCIENCE· October 2001 Rostrum (Figure lA,E) reaching anterior pace, short, rather thick, anteriorly with margin of corneas of eyes, broad, constricted mesially curved hepatic spine; branchiostegal at midlength; anterior margin weakly con­ carina sharp, supporting branchiostegal spine, cave, its width 0.16 of carapace length; dorsal extending to level of hepatic spine, unarmed; surface deeply concave; lateral margins orbital margin strongly elevated; gastric re­ greatly elevated, unarmed, forming supra­ gion shallowly depressed on either side of orbital eave covering base of ocular peduncle; midline; antennal spine showing as broad anterolateral angle rounded; ventral margin triangular projection with blunt apex; bran­ weakly concave in lateral view. Carapace chiostegal spine moderately large, reaching (Figure lA,E) almost as long as wide, slightly anterior margin of cornea of eyes, directed broadened posteriorly; median carina extend­ slightly dorsally and mesially; pterygostomian ing from anterior 0.4 of carapace, becoming spine small, arising from ventromesial to base gradually obsolete in posterior 0.2, terminat­ of branchiostegal spine. ing anteriorly in moderately large gastric Thoracic sternum broad, elevated medi­ spine, dorsal margin weakly sinuous in lateral ally, with long median spine reaching coxae view; first (dorsolateral) carina extending of second pereopods. from anterior 0.2 to near posterolateral mar­ Abdomen (Figure lA,E) widest at second gin of carapace, somewhat convergent poste­ somite, abruptly becoming narrower at fourth riorly against midline, divided in two sections somite. First somite with distinct transverse by wide, shallow notch at about midlength carina along posterodorsal margin on tergum, of carina, anterior section distinct, posterior but without median carina; lateral longitudi­ section becoming blunt posteriorly; hepatic nal carina low, not in contact with transverse carina beginning from anterior 0.14 of cara- carina; pleuron rounded ventrally. Second so- AS 1 mm B FIGURE 1. Philocheras breviflagella, n. sp. Holotype, ovigerous female from O'ahu, Hawai'i (el 2.6 mm; ZRC 2000.0369). A, Entire animal, lateral; B, same, dorsal; C, sixth abdominal somite and telson, dorsal, setae partially omitted. A New Species of Crangonid Shrimp of the Genus Philocheras . Komai 421 mite with two transverse carinae on tergum; timate segment shorter than broad, with posterodorsal margin with deep median anterodorsal margin slightly produced. Ulti­ notch; lateral carina broad, faint, in contact mate segment short, unarmed. Dorsal flagel­ with anterior transverse carina; pleuron with lum very short and stout, falling slightly short obtuse point on ventral margin. Third somite of distal margin of antennal scaphocerite, with distinct median carina running over en­ composed of six articles (distal three articles tire length; tergum with four low transverse with aesthetascs); ventral flagellum shorter carinae, anterior three carinae not in contact than dorsal flagellum, composed of four with either median or lateral carina, posteri­ articles. ormost carina marginal, in contact with both Antenna (Figures IA,B, 2B) with basicerite median and lateral carinae; lateral carinae stout, unarmed laterally. Scaphocerite 0.43 low, faint; pleuron with blunt angle on ventral times as long as carapace and 1.96 longer than margin. Fourth somite with low median ca­ broad; lateral margin slightly sinuous, un­ rina bearing faint pits or depressions; pos­ armed; distolateral tooth weakly curved me­ terodorsal margin with shallow, but distinct sially, reaching broadly rounded distal margin median notch; tergum and pleuron faintly of blade; mesial margin strongly convex. sculptured by transverse carinae; ventral Carpocerite weakly flattened dorsoventrally, margin of pleuron forming blunt angle pos­ slightly overreaching distal margin of sca­ teriorly. Fifth somite with low median carina, phocerite. Flagellum broken off. bifurcate posteriorly, anterior part with shal­ Mouthparts as usual in crangonids. Man­ low median sulcus; tergum with obliquely dible (Figure 2C) with five distal teeth in total transverse carina laterally; pleuron with short (three on external edge). Maxillule (Figure obliquely transverse (vertical) carinae later­ 2D) with proximal endite flattened, subovate, ally, ventral margin broadly rounded. Sixth with row of sparse long setae on mesial mar­ somite (Figure lA-C) with two low sub­ gin; distal endite with four spines on truncate median carinae, each produced beyond pos­ mesial margin. Maxilla (Figure 2E) with terodorsal margin as rounded lobe; lateral rudimentary endite bearing one long apical surface with row of scalelike setae along sub­ bristle; endopod curved mesially, tapering median carinae in posterior half; postero­ distally, with long plumose setae; posterior lateral process rounded; posteroventral angle lobe of scaphognathite not elongate, but with forming subacute tooth; ventral surface shal­ very long setae on posterior margin. First lowly concave, lacking preanal spine. Telson maxilliped (Figure 2F) lacking endites; endo­ (Figure IC) with broad median sulcus; dor­ pod flattened, with sparse row of long plu­ solateral ridges distinct in anterior 0.7 length mose setae on mesial margin; exopod with of telson, with two pairs of small, distally moderately narrow caridean lobe bearing row truncate spines (anterior pair arising from 0.4 of setae on lateral margin; exopodal flagel­ length of telson); posterior margin rounded, lum well developed; epipod well developed, with one pair of tiny, blunt posterolateral bilobed (broken during dissection). Second spines and two pairs of long plumose setae. maxilliped (Figure 2G) with three long Abdominal sternum unarmed medially. spines on mesial margin of dactylus; exopod Eye (Figure IA,B) partially covered by tapering distally, with well-developed fla­ orbit formed by rostrum and antennal spine gellum; epipod small, devoid of podobranch. of carapace; ocular peduncle short, slightly Third maxilliped (Figure JA,B) overreaching wider than cornea, with small, low tubercle distal margin of scaphocerite by half