Journal of Natural History Vol. 45, Nos. 1–2, January 2011, 77–111 The crangonid shrimp genus Metacrangon (Crustacea: Decapoda: Caridea) from New Zealand, with descriptions of four new species Tomoyuki Komaia* and Shane T. Ahyongb aNatural History Museum and Institute, Chiba, 955-2 Aoba-cho, Chuo-ku, Chiba, 260-8682 Japan; bAustralian Museum, 6 College Street, Sydney, NSW 2010, Australia (Received 24 February 2010; final version received 30 August 2010; printed 13 December 2010) Examination of collections from waters around New Zealand resulted in signifi- cant findings of six species of Metacrangon Zarenkov, 1965, a crangonid shrimp genus well represented in the North Pacific: M. knoxi (Yaldwyn, 1960); M. richard- soni (Yaldwyn, 1960); M. hikurangi sp. nov.; M. haona sp. nov.; M. rau sp. nov.; and M. teina sp. nov. The present material includes the second record of the two previously described species since their original descriptions. The four new species are all closely related to M. knoxi, suggesting a monophyletic origin of these five species. Differentiating characters among the four new species and M. knoxi are discussed in detail. All six species are known only from New Zealand waters, and they are probably endemic to the area. Keywords: Caridea; Crangonidae; Metacrangon; new species; New Zealand Introduction The crangonid shrimp genus Metacrangon Zarenkov, 1965 is currently represented by 25 species and one subspecies (Zarenkov 1965; Fujino and Miyake 1970; Butler 1980; Komai 1994, 1995, 1997; Kim and Hayashi 2003; Retamal and Gorny 2003; Kim 2005; Komai and Komatsu 2009). It is characterized by the shallowly depressed gastric region of the carapace, the usual presence of a pair of submedian teeth on the carapace, the laterally flared pleuron of the sixth abdominal somite, and the second pleopod with an appendix masculina being much shorter than the endopod (Zarenkov 1965; Butler 1980; Kim and Hayashi 2003; Kim 2005). Many species occur in the northern hemisphere (19 species and one subspecies in the North Pacific and one species in the North Atlantic), but five species, namely, M. bahamondei Retamal and Gorny, 2003, M. bellmarleyi (Stebbing, 1914), M. crosnieri Komai, 1997, M. knoxi (Yaldwyn, 1960) and M. richardsoni (Yaldwyn, 1960), are found in the southern hemi- sphere (Stebbing 1914; Yaldwyn 1960; Komai 1997; Retamal and Gorny 2003). In addition, one undescribed species is known from southwestern Australia, awaiting formal description (Poore et al. 2008; Komai and Taylor, in press). In spite of the rather wide geographic and bathymetric distributions of the genus, many species are restricted to narrow geographic areas or to narrow depth ranges. Examination of the material in the collections of the National Institute of Water and Atmospheric Research (NIWA) resulted in the significant findings of six species of Metacrangon from waters around New Zealand, including M. knoxi, M. richardsoni *Corresponding author. Email: [email protected] ISSN 0022-2933 print/ISSN 1464-5262 online © 2010 Taylor & Francis DOI: 10.1080/00222933.2010.520823 http://www.informaworld.com 78 T. Komai and S.T. Ahyong and four new species, namely, M. haona, M. hikurangi, M. rau and M. teina.These four new species are all closely related to M. knoxi, which is referred to the informal M. jacqueti (A. Milne-Edwards, 1881) species group, suggesting a monophyletic origin of the five species restricted to New Zealand waters. The material examined in this study is deposited in NIWA, the Canterbury Museum, Christchurch (CM), and the Museum of New Zealand Te Papa Tongarewa (MNZ). The measurement provided is of the postorbital carapace length (CL) mea- sured from the level of the posterior margin of the orbit to the midpoint of the posterodorsal margin of the carapace. To avoid repetitious description, only M. teina, for which seven specimens are available for study, is fully described. Taxonomy Metacrangon haona sp. nov. (Figures 1–3) Material examined Holotype. Pukaki Rise, Campbell Plateau, 49◦21.50 S, 171◦53.00 E, 353 m, stn D0210, 26 January 1964, male (CL 6.8 mm), NIWA 6257. Description Body (Figures 1, 2A,B) moderately robust. Rostrum (Figures 1, 2A) dorsoventrally flattened, directed slightly dorsally, unusually elongate (0.55 times as long as cara- pace), reaching distal margin of antennular peduncle, sinuously curved in lateral view; tip acuminate in dorsal view; dorsal surface nearly flat; lateral margin merging into orbital margin; midventral carina low, blunt, present only in proximal half. Carapace (Figures 1, 2A) not widened posteriorly, distinctly longer than wide postorbitally; sur- face covered with very short setae; dorsal midline with two very prominent, laterally compressed teeth; anterior tooth arcuate, strongly upturned (angle against horizontal plane of carapace about 50◦), arising distinctly anterior to rostral base, overlapping rostrum, tip slightly falling short of rostral tip; posterior (cardiac) tooth slightly smaller than anterior tooth, hooked, arising at 0.60 of CL; submedian tooth moder- ately small; hepatic tooth moderately small, followed by epibranchial ridge; antennal tooth moderately small, directed forward in lateral view and somewhat laterally in dor- sal view, acuminate; orbital cleft absent; anterolateral margin between antennal and branchiostegal teeth with tiny denticle inferior to base of antennal tooth; branchioste- gal tooth slender, recurved, directed laterally in dorsal view and slightly dorsally in lateral view, over-reaching level of dorsodistal margin of antennal basicerite; ptery- gostomial tooth small, not visible in lateral view; postorbital carina clearly delimited, accompanied by suture; epibranchial carina distinct. Abdomen (Figures 1, 2B) moderately sculptured; anterior five somites each with distinct, crested mid-dorsal carina, none of mid-dorsal carina on anterior four somites not extending to posterodorsal margin of each somite; mid-dorsal carina on first and second somites produced anterodorsally. First pleuron with blunt, but well-defined tooth at posteroventral angle; second pleuron with triangular tooth at middle of ven- tral margin; first and second pleura flared laterally, so ventral teeth visible in dorsal Journal of Natural History 79 Figure 1. Metacrangon haona sp. nov., holotype, male (CL 6.8 mm), NIWA 6257. Entire animal in lateral view. Scale bar: 2 mm. 80 T. Komai and S.T. Ahyong Figure 2. Metacrangon haona sp. nov., holotype, male (CL 6.8 mm), NIWA 6257. (A) Carapace and cephalic appendages, dorsal view (setae partially omitted); (B) abdomen, dorsal view (setae omitted); (C) fifth and sixth abdominal somites, lateral view. Scale bars: 2 mm. Journal of Natural History 81 view; third and fourth pleura each with distinct triangular tooth at anteroventral angle. Fifth somite (Figure 2C) with obsolete lateral ridge; dorsal margin nearly straight in lateral view; posterodorsal margin armed with small tooth on either side of median projection; pleuron rounded posteroventrally. Sixth somite 1.7 times longer than wide; submedian carinae distinct, slightly curving, not reaching posterodorsal margin; dor- solateral carina distinct, sinuous posteriorly; posterodorsal margin strongly produced, bi-toothed; pleuron strongly flared laterally, posteroventral tooth strong; posterolat- eral process strong, somewhat curved laterally, terminating in sharp tooth (Figure 2C). Telson (Figure 2B) with three pairs of dorsolateral spines, anteriormost pair located at posterior 0.4; several pairs of plumose setae distal to third pair of lateral spines. Thoracic sternum widened posteriorly; fifth thoracic sternite with relatively broad, forwardly directed median tooth; sixth to eighth sternites with prominent median keels, those on sixth and seventh sternites each with sharp point anteriorly, that of eighth sternite sharply pointed dentiform. First to fourth abdominal sternites each with prominent median tooth, fifth sternite with short median ridge. Sixth sternite wide, shallowly depressed. Eye (Figures 2A, 3A) as wide as long; cornea as wide as eyestalk, light grey- ish brown in preservative, corneal width about 0.20 of CL; eyestalk with prominent, acutely pointed dorsal tubercle over-reaching distal corneal margin. Antennular peduncle (Figures 2A, 3A) reaching midlength of antennal scale. First segment with prominent, blunt distolateral process curving anteriorly, disto- mesial margin unarmed; stylocerite terminating in acute tooth, slightly falling short of tip of distolateral process of first segment, lateral margin obtusely angular. Second segment much wider than long, widened distally, with prominent, blunt distolateral process. Third segment wider than long. Outer flagellum over-reaching distal margin of lamella of antennal scale by 0.6 length, consisting of 14 or 15 articles. Antennal basicerite (Figures 2A, 3A) stout, with produced, acutely pointed dor- sodistal lateral angle, ventrolateral tooth reaching beyond dorsodistal lateral angle. Antennal scale 0.53 times as long as carapace and 2.3 times longer than wide; lat- eral margin nearly straight; distolateral tooth moderately wide, just reaching rounded distal margin of lamella. Third maxilliped relatively slender, over-reaching antennal scale by half length of ultimate segment; ultimate segment (Figure 3B) gradually tapering distally, about 7.5 times longer than wide; penultimate segment about 3.3 times longer than wide (Figure 3B); antepenultimate segment unarmed on ventral surface. First pereopod (Figure 3C,D) reaching distal margin of antennal scale;