A NEW SPECIES OF LOXORHYNCHUS STIMPSON (DECAPODA, MAJOIDEA, PISIDAE) FROM THE PACIFIC COAST OF MEXICO

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1 A NEW SPECIES OF LOXORHYNCHUS STIMPSON (DECAPODA, MAJOIDEA, PISIDAE) FROM THE PACIFIC COAST OF MEXICO BY MICHEL E. HENDRICKX 1,3 / and JOSE LUIS CERVANTES 2 / 1 / Instituto de Ciencias del Mar y Limnología, UNAM, Unidad Académica Mazatlán, P.O. Box 811 Mazatlán, Sinaloa, Mexico 2 / Universidad Autónoma de Baja California Sur, La Paz, Mexico ABSTRACT A new species of Majoidea belonging to the family Pisidae is described from the Paci c coast of Mexico. The species is assignedto the genus LoxorhynchusStimpson, endemic to the east Paci c and known from two species only. It is distinguished from L. grandis Stimpson, 1857, the type species, and from L. crispatus Stimpson, 1857 by several characteristics, including the shape of the tip of the rst pleopod. The rostrum of the new species is only very slightly de exed vs. strongly de ected in the other two species. The immovable basal article of the antenna is not nearly quadrate, but rather trapezoidal with the distal margin narrower than the proximal (as in other Pisidae) and there is, in addition to the latero-distal spine, a latero-proximal spine. There are 6-7 spines on the hepatic region of the new species vs. two spines (L. grandis) or one spine and a dome-like prominence (L. crispatus) in the other species. RÉSUMÉ Une nouvelle espèce de Majoidea de la famille Pisidae est décrite pour la côte du Paci que mexicain. Cette nouvelle espèce est assignée au genre Loxorhynchus Stimpson, endémique du Paci que Est et dont seulement deux espèces sont connues. Elle se distingue de L. grandis Stimpson, 1857, l espèce type du genre et de L. crispatus Stimpson, 1857, par plusieurs caractères, y-compris la forme de l extrémité du premier pléopode. Le rostre de la nouvelle espèce est peu incliné mais il l est très fort chez les deux autres espèces du genre. Le segment basal et xe de l antenne n est pas de forme carrée, mais bien trapézoïdal, avec un bord distal plus large que le bord proximal (comme chez les autres Pisidae); il possède, en plus de l épine latéro-distale, une épine latéro-proximale. Il y a 6-7 épines sur la région hépatique de la nouvelle espèce vs. deux épines (L. grandis) ou une épine et une élévation en forme de dôme (L. crispatus) chez les deux autres espèces. 3 / michel@ola.icmyl.unam.mx Koninklijke Brill NV, Leiden, 2003 Crustaceana 76 (1): Also available online:

2 104 M. E. HENDRICKX & J. L. CERVANTES INTRODUCTION The west American genus Loxorhynchus Stimpson, 1857 is represented by two species. The type species, L. grandis Stimpson, 1857 ranges from 38 ± N (Cordell Bank, California) to Thurloe Bay, Southern Baja California, Mexico, with one doubtful record along the coast of Jalisco, Mexico. The second species, L. crispatus Stimpson, 1857 is known from Redding Rock (41 ± N), California, to Natividad Island, Baja California, Mexico. Both species are large spider crabs, reaching 159 mm and mm of carapace width (CW), respectively (Garth, 1958; 1980; Wicksten, 1977; Hendrickx, 1999). During sampling operations at m off the coast of Baja California, Mexico, a large series of spider crabs was collected in traps. The specimens could not be properly identi ed at once and a closer examination reveals that they belong to a third, undescribed species of Loxorhynchus. Abbreviations used in this paper are: CW, carapace width; CL, carapace length; EMU, Estación Mazatlán UNAM Invertebrates Reference Collection; UABCS, Museo de Ciencias Naturales, Universidad Autónoma de Baja California Sur; LACM CR, Los Angeles County Museum of Natural History, U.S.A. TAXONOMY Loxorhynchus guinotae new species ( gs. 1-5) Type material. Holotype male (CW 69.3 mm; CL 84.7 mm with rostrum), 65 miles W of Boca de las Animas, Baja California Sur, Mexico (25 ± 39:8 0 N 113 ± 09:3 0 W), trap, 22 May 2001, 100 m depth (EMU-2550). Paratype male (CW 90.3 mm; CL mm with rostrum), right cheliped missing, same sampling station (EMU-2551). Paratype female (CW 64.3 mm; CL 79.5 mm with rostrum), ovigerous, same sampling station (EMU-2566). Paratype female (CW 58.4 mm; CL 72.7 mm), ovigerous, broken rostrum, same sampling station (EMU-2608). Paratype male (CW 60.2 mm; CL 75.1 mm with rostrum), same sampling station (LACM CR ). Additional material. One female (CW 70.6 mm; CL 89.5 mm with rostrum), ovigerous, off Baja California, Mexico (25 ± 39:8 0 N 113 ± 09:3 0 W), trap, 22 May 2001, 100 m depth (EMU-2704). A series of 9 males (CW mm, CL mm), 4 females (CW mm, CL mm) and 4 ovigerous females (CW mm, CL mm) off Baja California, Mexico (25 ± 52:0 0 N 113 ± 15:1 0 W), trap, 06 March 2001, 118 m depth (see table I) (UABCS), damaged and discarded after morphological analysis. Two males (CW mm; CL mm) and one female (CW 93 mm; CL 115 mm), same sampling station. Description. Carapace pyriform ( g. 1), spinose, entirely covered with microscopic vesicles containing a stiff hair and with patches of curved hairs; carapace width times postrostral length (holotype, 0.98). Rostrum short, about 0.2 times postrostral length; cleft between base of rostral spines about rostral length, rostral spines slightly depressed, slightly de exed, diverging; rows of curved hairs dorsally.

3 LOXORHYNCHUS GUINOTAE NOV. 105 TABLE I Damaged specimens of Loxorhynchus guinotae new species collected on 06 March, CW and CL (including rostrum) are in mm. Fresh weight (g) is provided as this species might represent a shery potential Sex CW CL Weight Sex CW CL Weight M M* FF FF F* F FF FF M M* M M M M M M F F F M M, male; F, female; FF, ovigerous female; * specimens held at UABCS. Six spines on fronto-orbital region, one pair beyond base of horns, one between supraocular spines, and one between postocular spines. Gastric region elevated; three spines in line on anterior part of mesogastric region, followed by a cluster of spines surrounding a central, slightly longer spine; two pairs of larger spines on metagastric region; one urogastric spine; 6 cardiac spines; intestinal region with 4 large and a few smaller spines; branchial region with over 40 spines of different size, largest, sharpest spines towards the lateral margin, there forming a series of 6-7 slightly curved marginal spines. Hepatic region small, prominent, with 6-7 spines, the largest sharp, slightly curved, on tip of prominence; one strong subhepatic spine, similar to the largest hepatic spine. Smaller spines or tubercles under hairs. Preocular spine strong, acute, diverging from rostrum; postocular spine semitubular, truncate except for a conspicuous dorsal conical tooth, lower spine sharp, almost ventrally directed; intermediate spine present, tipped with a similar conical tooth, separated form preorbital spine by a shallow notch and from postorbital spine by a dorsal, longitudinal ssure, which appears partly fused ( g. 2A-B). Eyestalk globular, much wider at base than cornea. Antennal basal segment long, moderately wide at base, narrower distally; lateral margin with two spines directed obliquely outwards, similar in size (proximal slightly shorter) and shape to preorbital spine. Second and third segment narrow, tubular, third about half length of second, not reaching tips of rostral horns ( g. 2B). Third maxilliped ( g. 2C) ventrally covered with vesicular hairs and stiff hairs; rows of long stiff hairs along inner margin of ischium, outer margin of exopod, and inner and distal margin of merus. Ischium with median depression, anterior margin

4 106 M. E. HENDRICKX & J. L. CERVANTES Fig. 1. Loxorhynchus guinotae new species, male holotype (EMU-2550), dorsal view (CW, 69.3 mm). strongly projecting mesially, a row of about 15 teeth on inner margin, teeth hidden by hairs ventrally but visible dorsally. Merus subquadrate, distally cleft on inner margin to receive palp, a strong tooth on anteromesial corner, visible dorsally.

5 LOXORHYNCHUS GUINOTAE NOV. 107 Fig. 2. Loxorhynchus guinotae new species, male holotype (EMU-2550). A, dorsal view of front; B, ventral view of front; C, ventral view of left third maxilliped (hairs omitted); D, ventral view of abdomen. Scale bars equal 10 mm. Chelipeds of immature male ( g. 3A) elongate, slender, almost equal in length, covered with vesicular hairs except on chelae which show some hair patches in proximal third; chelae not swollen, slightly compressed laterally, lateral surface almost smooth and bearing a few scattered, attened tubercles; a few sharp tubercles on lower and upper margins, larger and more numerous proximally. Fingers curved inwards, slightly (young specimens) to strongly (larger specimens) gaping in proximal 1/3; ngers about half palm length, cutting edges denticulate, a strong basal tooth on dactylus projecting in proximal gap. Carpus with three strong blunt spines on inner margin and about similar, scattered spines on external face. Merus about 0.8 times as long as chela, with four longitudinal rows of spines, one each on ventral, dorsal, inner, and outer faces; spines somewhat irregular in size and sharpness, the sharpest and longest spines on dorsal margin; some additional, smaller, scattered spines in distal third. Basi-ischium unarmed. Chelipeds of female similar to those of male, relatively shorter, armed with fewer spines and tubercles; denticulation on cutting edge of ngers weaker, projecting tooth shorter. Chelipeds of mature males (from colour picture; see g. 5) proportionally stronger than in immature specimens; merus and propodus

6 108 M. E. HENDRICKX & J. L. CERVANTES Fig. 3. Loxorhynchus guinotae new species, male holotype (EMU-2550) (hairs omitted). Lateral views of: A, left cheliped; B, second pereiopod; C, third pereiopod; D, fourth pereiopod; E, fth pereiopod. Scale bar equals 10 mm. TABLE II Length and proportion (as percentage of average length of chelipeds: 133 mm) of left pereiopods of male holotype of Loxorhynchus guinotae new species P1 130 mm (left) P1 136 mm (right) P2 129 mm (97%) P3 108 mm (81%) P4 95 mm (71%) P5 89 mm (69%) of about the same length, propodus and proximal gap between ngers wider than in immature specimens. Pereiopods 2-5 ( g. 3B-E) similar, diminishing in length posteriorly (table II), entirely covered with vesicular hairs and with stiff, straight or curved hairs dorsally, without spines or tubercles, except for a sharp spine on distal edge of dorsal

7 LOXORHYNCHUS GUINOTAE NOV. 109 TABLE III Length and proportions (as percentage of postrostral carapace length: 70.5 mm) of merus, carpus, and propodus of left pereiopods of the male holotype of Loxorhynchus guinotae new species Merus Carpus Manus Entire pereiopod P1 L 51.8 mm (73%) 17.5 mm (25%) 45.0 mm (64%) 130 mm (184%) P1 R 53.0 mm (75%) 17.7 mm (25%) 46.5 mm (66%) 136 mm (187%) P mm (66%) 21.0 mm (30%) 32.2 mm (46%) 129 mm (183%) P mm (53%) 19.3 mm (27%) 26.5 mm (38%) 108 mm (153%) P mm (47%) 18.0 mm (25%) 23.5 mm (33%) 95 mm (135%) P mm (41%) 15.5 mm (22%) 21.4 mm (30%) 98 mm (126%) margin of merus of legs 2-4, this spine wanting on leg 5. Length of merus, carpus, and propodus of pereiopods and their proportions compared to carapace length as shown (table III). Dactylus gently curved; tip naked, corneous, laterally and ventrally grooved. Sternum densely covered with vesicular hairs; sternal cavity narrow and deep. Seven free abdominal somites ( g. 2D) densely covered with similar hairs; rst abdominal somite narrow, subrectangular, with a strong median conical tubercle near posterior margin; second somite trapezoidal, about 1.5 as wide as rst one, a rounded tubercle near posterior margin; third abdominal somite the widest, rectangular, with pair of rounded elevations; somites 4-6 gradually diminishing in width, subrectangular; telson subtriangular, posterior margin rounded. First pleopod of male ( g. 4A-C) very long, shaft slightly twisted, gradually diminishing in width towards the tip; upper extremity of shaft (distal 1/6) gooseneck shaped; shaft smooth, except for some setae in proximal half. Tip of rst pleopod sharply bent ventrally, at almost 90 ± ; opening anked by two lateral lobes, the inner lobe folding over the outer one; a disto-lateral ange extending almost to the extremity of the bended tip; an opposite lobe of nearly equal size extending from the tip, downwards along the shaft. Second pleopod small, less than 1/4 length of rst pleopod; agellum short, conical ( g. 4D-E). Size. Largest specimens observed: male, CW 130 mm and CL 143 mm; female, CW 100 mm and CL 121 mm. Smallest ovigerous female, CW 58.4 mm. Fresh weight up to 860 g (table I). Specimens were all captured in traps with circular (18 cm diameter) or rectangular (13 cm largest side) inner openings. If present, larger specimens (CW > 130 mm) might not have found their way through the trap openings, as in the case of large specimens of Stenocionops ovata (Bell, 1835), which were occasionally found stuck in the passage of the traps used during this survey. Colour. General colour of carapace red, appearing brownish where hairs are densely set. White spots or areas on ventral side of chelipeds and coxae of

8 110 M. E. HENDRICKX & J. L. CERVANTES Fig. 4. Loxorhynchus guinotae new species, male holotype (EMU-2550). A, lateral view of right rst pleopod; B, same, enlarged outer view of extremity; C, same, enlarged inner view of extremity; D, lateral view of right second pleopod; E, same, enlarged view of extremity. A, D: scale bar equals 5 mm. pereiopods. Palms and ngers of chelipeds bright red, with two whitish areas on each lateral face; extremity and inner side of ngers pink or white. Etymology. The new species is named in honour of Danièle Guinot, Muséum national d Histoire naturelle, Paris, in recognition of her outstanding work on taxonomy and phylogeny of Brachyura and to acknowledge her kindness and constant support to one of us (MEH). Remarks. Assignment of the new species to the genus Loxorhynchus is made with some doubt. The material examined features the typical commencing orbits of the Pisidae (Pisinae sensu Garth, 1958), including a large, isolated, and cupped postocular tooth into which the eye retracts incompletely and a prominent supraocular eave, which in this case is produced forwards as a spine. Although partly covered by vesicular hairs, the dorsal and ventral orbital ssures are clearly visible. The two-spined rostrum, long pereiopods, and the broad basal segment of the antenna (proximal margin broad, distal narrower), together with the shape of the rst maxilliped, are also features of Pisidae. The new species features an intercalated orbital spine, as in Hyasteniinae, but the shape of the male rst pleopod is more reminiscent of the scyriform pleopod

9 LOXORHYNCHUS GUINOTAE NOV. 111 Fig. 5. Loxorhynchus guinotae new species, male specimen (CW 101 mm, CL 118 mm) (see table I). Top, dorsal view; bottom, ventral view. Scale bars equal 50 mm.

10 112 M. E. HENDRICKX & J. L. CERVANTES displayed by the Pisidae group (i.e., Loxorhynchus, Scyra, etc. : : :). Garth (1958: 249) questioned the validity of the presence-absence of the intercalated orbital spine as a good character to separate the two subfamilies and concluded that this cannot be sustained. Grif n & Tranter (1986: 104) comment on the reassignment of several species and genera of Pisinae Alcock, not including Loxorhynchus, which is endemic to the Paci c coast of America. Their de nition of the subfamily Pisinae (now generally considered at family level; see Martin & Davis, 2001) is taken from Garth (1958), except for their description of the rst pleopod which includes the several types recognized for this subfamily. Grif n & Tranter (1986), as Garth (1958) did almost 30 years before, recognized the diversity of rst pleopod shapes within the Pisinae combined with a surprisingly little diversity in other characters, especially those of the orbit, which features the typically cupped postorbital lobe. Other characteristics of Loxorhynchus as treated by Garth (1958: 256) are all found in our material, with the following exceptions. The rostrum of L. guinotae is only very slightly de exed. The immovable basal article of the antenna is not nearly quadrate, but rather trapezoidal with the distal margin narrower than the proximal (as in other Pisidae); also there is, in addition to the latero-distal spine, a latero-proximal spine. A male specimen (CW 34.5 mm) of Loxorhynchus grandis, the type species of the genus, was examined for comparative purposes together with the excellent photographs of L. grandis and L. crispatus provided by Garth (1958, pls. 28, 29). In general, the three species are very similar in shape. The upper and lower longitudinal sinuses of the orbit are clearly visible on the new species, even more so than on the specimen of L. grandis examined. The inner angle of the ischium of the third maxilliped is also clearly produced and rounded as in the type species of Loxorhynchus. Chelipeds and pereiopods 2-5 are similar to the type species and to the other species of the genus, L. crispatus. The hepatic region of L. guinotae bears 6-7 spines of different length. The other species feature only two spines (L. grandis) or a spine and a dome-like prominence (L. crispatus) on this region. Species of Loxorhynchus are known to grow to large size, particularly L. grandis (CW up to 159 mm). Length and shape of chelipeds vary during growth, as can be observed on one of the largest males of L. guinotae captured with traps ( g. 5), which features a much wider and deeper proximal gap than the holotype (see g. 2A). Species of the genus Loxorhynchus, particularly the new species, might at rst glance be confused with species of Libinia occurring in the area (i.e., L. rostrata Bell, 1835; L. setosa Lockington, 1877; L. mexicana Rathbun, 1892). Libinia rostrata features a very large lateral spine on the carapace, a character not found in any species of Loxorhynchus. The two other species of Libinia of the Paci c coast have a more accentuated pyriform shape, with much shorter spines, and are

11 LOXORHYNCHUS GUINOTAE NOV. 113 therefore much more similar to Loxorhynchus guinotae. Species of Loxorhynchus, however, present a clearly imperfect orbit, with both upper and lower longitudinal sinus deep (particularly the upper sinus which widely separates the supraocular eave and the postocular process), whereas in Libinia the orbit is small, circular, with an upper closed or nearly closed ssure, and a lower closed ssure or open sinus. The third maxilliped of Loxorhynchus presents a rounded projection at the inner angle of the ischium, a feature not observed in Libinia, which possesses a truncate distal end with no lateral projection. ACKNOWLEDGEMENTS We thank Mercedes Cordero for preparing the nal version of the manuscript, Graciano Valenzuela Leyva for the illustrations of the holotype ( gs. 2 and 3) and Germán Ramírez Reséndiz for mounting the illustrations (electronic le). Part of this study was supported by SIMAC (project ). REFERENCES BELL, T., Some account of the Crustacea of the coasts of South America, with descriptions of new genera and species; founded principally on the collections obtained by Mr. Cuming and Mr. Miller (tribus 1, Oxyrhynchi). Proc. zool. Soc. London, 3: GARTH, J. S., Brachyura of the Paci c coast of America; Oxyrhyncha. Allan Hancock Paci c Exped., 21 (1-2): , Chapter 25. Brachyura the true crabs. In: R. H. MORRIS, D. P. ABBOTT & E. C. HADERLIE (eds.), Intertidal invertebrates of California: (Stanford University Press, Stanford). GRIFFIN, D. J. G. & H. A. TRANTER, The Decapoda Brachyura of the Siboga Expedition Part VIII. Majidae. Siboga Expeditie Monogr., 39: HENDRICKX, M. E., Los cangrejos braquiuros (Crustacea: Brachyura: Majoidea y Parthenopoidea) del Pací co mexicano: (Comisión Nacional para el Conocimiento y Uso de la Biodiversidad e Inst. Cienc. Mar y Limnol., UNAM, Mexico). LOCKINGTON, W., Remarks on the Crustacea of the Paci c coast of North America, including a catalogue of the species in the Museum of the California Academy of Sciences, San Francisco. Proc. California Acad. Sci., 7: RATHBUN, M. J., Catalogue of the crabs of the family Periceridae in the U.S. National Museum. Proc. U.S. nat. Mus., 15 (901): STIMPSON, W., Notices of new species of Crustacea from western North America. Being an abstract from a paper to be published in the Journal of the Society. Proc. Boston Soc. nat. Hist., 6: WICKSTEN, M. K., Decorating in the crab Loxorhynchus crispatus Stimpson (Brachyura, Majidae): (Ph.D. Thesis, University of Southern California). First received 2 July Final version accepted 19 November 2002.