Calappa karenae, Ng, Peter K. L. & Lai, Joelle C. Y., 2012

Ng, Peter K. L. & Lai, Joelle C. Y., 2012, Calappa karenae, a new species of box crab from Guam (Crustacea: Decapoda: Brachyura: Calappidae), Zootaxa 3393, pp. 57-65 : 57-64

Calappa karenae sp. nov.

( Figs. 1–5 )

Calappa sp. 1 ( aff. sebastiani Galil, 1997 )— Paulay et al. 2003: 496 [not Calappa sebastiani Galil, 1997 ] Material examined. Holotype: male (180.4 by 95.9 mm) (USNM 1150290 ), Haputo, Guam, in crab-trap, 100 fathoms (= 183 m), coll. E. Smith & L. Eldredge, 10 April 1986. Paratype: 1 male (CL 89.6 mm, damaged carapace; dimensions estimated from Fig. 1 , 197.0 mm by 95.0 mm) (USNM 1150291 ), same data as holotype.

Diagnosis. Carapace much broader than long, width to length ratio 1.88–2.07. Anterior two-thirds of dorsal surface with large, round submammillate tubercles; posterior one-third with numerous low small granules ( Fig. 1 , 2 ). Pterygostomian lobe with broad inner oblique longitudinal groove ( Fig. 4 D). Posterolateral margin of clypeiform expansion with 8 triangular teeth ( Figs. 1 , 2 ). Outer margin of merus of cheliped with 4 lobes ( Fig. 4 C). Chela with 6 high, lamelliform teeth on dorsal margin ( Figs. 3 A, 4A, B). Male thoracic sternites 4–6 relatively broad ( Fig. 3 B, C). Male abdomen relatively broad; somite 6 subrectangular, slightly wider than long ( Fig. 3 B, C). G1 C-shaped; tip truncated ( Fig. 5 B, C, D, E).

Description. Carapace transversely ovate, much broader than long, width to length ratio 1.88 (holotype), 2.07 (estimated from photograph of paratype when intact) ( Figs. 1 , 2 ). Dorsal surface convex, anterior two-thirds covered with large, round submammillate tubercles, resembling low pustules, surface between tubercles finely granular; posterior third with numerous low small granules, short transverse striae, becoming more prominent, relatively larger towards posterior margin ( Figs. 1 , 2 ). Gastric region convex, with median part highest point of carapace, surface with low granules, tubercles; longitudinal gastro-cardiac grooves relatively deep, extending to just before posterior margin ( Figs. 1 , 2 ). Frontal margin distinctly bifurcated, with deep, broad U-shaped median cleft separating triangular teeth, separated from supraorbital margin by broad cleft ( Fig. 2 A). Supraorbital margin uneven, granular, with 2 narrow longitudinal fissures on outer half ( Fig. 2 A). Eyes folded obliquely, external orbital tooth low, tubercular ( Fig. 3 A). Suborbital margin broad, dentiform, appearing sublobiform, with 3 low but distinct teeth, separated from external orbital angle by deep fissure ( Fig. 3 A). Pterygostomian lobe at end of posterior margin of epistome with relatively broad inner oblique longitudinal groove ( Fig. 3 A). Basal antennal article subquadrate, cusp-like, with transverse median ridge; proximal margin with prominent granules, distal margin deeply notched ( Figs. 3 A, 5A). Longitudinal epistomial septum appears anteriorly complete ( Figs. 3 A, 4D). Proepistome rounded ( Fig. 3 A). Third maxilliped with margins of merus densely setose, distal margin cleft, anterolateral angle auriculiform ( Fig. 4 D). Anterolateral margin arcuate, with 12–15 blunt, rounded unevenly sized tubercles, first tubercle distinct, subsequent ones very low, not easily discernible; last 5 or 6 progressively larger, more dentiform. Posterolateral margin of clypeiform expansion well developed, margins densely setose but not obscuring margin, with 8 triangular teeth, each tooth with denticulate margins, longitudinal median ridge (very strong in last 3 posterior teeth); first 4 teeth symmetrical, directed obliquely anteriorly; fifth tooth slightly asymmetrical, posterior part slightly longer, directed laterally; sixth tooth largest, broadest, asymmetrical, inner margin twice length of outer margin, directed posteriorly; last 2 teeth progressively smaller; posterior carapace margin gently concave, granular, not flanked by teeth but low lobes ( Figs. 1 , 2 ).

Chelipeds asymmetrical, right larger ( Figs. 1 , 2 A, B, 3A). Outer margin of merus with 4 lobes, first lobe very low, distalmost largest, sharpest; tip of lobes 3, 4 with sharp tubercle distally ( Fig. 4 C). Carpus subtriangular, outer surface granular with scattered low tubercles ( Fig. 4 B, C). Chela high, dorsal margin with prominent crest, with 6 high, lamelliform teeth, first smaller than second, directed slightly anteriorly; next 5 teeth vertical, acutely triangular, progressively smaller; base of crest with 2 small teeth; outer surface of manus with numerous granules, more prominent becoming denser, more prominent towards ventral margin with scattered large rounded tubercles; granules relatively more prominent in smaller chela; ventral margin lined with prominent row of granules, with prominent triangular tooth on proximal edge of ventral margin ( Figs. 3 A, 4A-C). Dactylus of major chela with distinct basal curved cutting tooth, rest of margin with several low teeth; pollex with 3 molariform teeth, first tooth largest, subsequent teeth small. Dactylus of minor chela slender, curved, proximal two-thirds granular, cutting margin lined with denticles; pollex relatively stouter, surface granular, proximal cutting margin lined with denticles, distal part more blade-like ( Fig. 4 A, B). Ambulatory legs slender, surfaces smooth; first leg longest; merus, carpus, propodus laterally flattened; dactylus styliform, gently curved ( Fig. 1 ).

Thoracic sternum narrow; sternites 1, 2 completely fused; separated from sternite 3 by convex shallow groove; sternites 3, 4 fused but median sutures still visible, medially interrupted with longitudinal depression ( Fig. 3 B); male thoracic sternites 4–6 relatively low, broad, surface covered with low, flattened granules ( Fig. 3 B, C). Sternoabdominal cavity almost reaching thoracic suture 3/4 ( Fig. 3 B).

Abdomen relatively broad; somite 1 longitudinally narrow with lateral parts expanded, anterior margin distinctly granular; somite 2 with lateral parts expanded to form subauriculiform process, surface prominently granular; somites 3–5 fused but median sutures just visible as shallow broad grooves, present as clefts laterally; somite 3 sub-rectangular, outer margin appears lobiform, granular, scalloped; somite 4 trapezoidal, lateral margins sinuous; somite 5 rectangular, lateral margins concave, distal margin granular; somite 6 subrectangular, slightly wider than long, lateral margins concave; telson acutely triangular, converging gradually to sharp tip; lateral margins gently concave ( Fig. 3 B, C).

G1 relatively stout, slightly sinuous ( Fig. 5 B, C); tip truncated, distal surface lined with numerous minute spinules ( Fig. 5 D, E). G2 subequal in length to G1, slender, curved, distal tip rounded ( Fig. 5 F, G).

Colour. On the basis of the colour photograph by Roy Kropp ( Fig. 1 ), the live colouration of C. karenae is striking. It ranges from orange-red anteriorly to a light salmon pink in the posterior part of the carapace, with the round, submammillate tubercles in the middle third of the carapace scarlet red and bright yellow at the apex, resembling small pustules. Tips of movable fingers are dark brown, as are the tips of propodus on its ambulatory legs. The inner surface of the cheliped carpus is red, and the inner surface of its manus bears numerous small red spots. The preserved specimens have lost their colour and are now uniformly beige.

Etymology. The authors are delighted to dedicate this distinctive new species to Ms Karen Reed, a custodian to the priceless crustacean collections at USNM, who helped us eventually locate these elusive specimens.

Remarks. A label associated with the present specimens, written in 1979 by the late Austin Williams notes that the species “keys to hepatica in Sakai 1976 but cannot be that”. The general features of C. karenae sp. nov. superficially resemble C. hepatica ( Linnaeus, 1758) , but the differences are marked. Calappa hepatica has a green to purplish-grey carapace, never red. The front does not project so far anteriorly, there are no mammary-like tubercles on the carapace, and most importantly, the carapace is much less broad, with the width to length ratio of about 1.6 to 1.7 (see Galil 1997). The basal article of the antenna is also completely different ( Galil 1997: Fig. 14a). The carapace of C. karenae sp. nov. is wider than any other Calappa species in the Indo-West Pacific: C. calappa ( Linnaeus, 1758) the next widest species, has a width to length ratio of 1.7 to 1.8 ( Galil 1997). The carapace width to length ratios of the holotype and paratype of C. karenae sp. nov. is 1.88 and 2.07. respectively Calappa japonica Ortmann, 1892 has been reported to attain a larger carapace length (see Lai & Ng 2006; Ng et al. 2011) but its width to length ratio is approximately 1.4 in adult males.

Calappa karenae sp. nov. was originally identified as C. sebastieni Galil, 1997 (labelled as “ Calappa aff. sebastieni ” in Paulay et al. 2003) on the basis of the photograph taken by Roy Kropp, but they are clearly different species, with C. sebastieni possessing a very different rostrum ( Galil 1997: fig. 20f) and a proportionately narrower carapace.

The species perhaps closest to C. karenae sp. nov. is the poorly known C. yamasitae Sakai, 1980 , described from two specimens (holotype male 110.0 × 66.0 mm and paratype female 100.0 × 62.0 mm) from Mie Prefecture in Japan. Unfortunately, comparisons between the two species can only be made based on Sakai’s publication, as the whereabouts of the only two known specimens of C. yamasitae is unknown. They are neither present in the various Japanese museums where Sakai’s material are known to be deposited, nor in Senckenberg Museum in Frankfurt where a good part of his collection was posthumously donated. The specimens may be lost, mislabeled, or misplaced in one of these museums. Sakai provided a colour photograph of C. yamasitae ( Sakai 1980: frontispiece fig. 2) although we do not know if it is an accurate representation of its live colour. The holotype as figured by Sakai (1980: frontispiece Fig. 2 ) had a carapace that was reddish-orange, with the large tubercles relatively darker in colour. The colouration, presence of mammary-type tubercles on carapace and general form of the chela are shared characters in both species. Their carapace proportions, however, are different; the width to length ratio is 1.6 for C. yamasitae whereas it is 1.88 in the holotype of C. karenae sp. nov. (2.07 in the paratype). While this disparity may be due to the much larger sizes of our specimens (CW 110.0 mm, C. yamasitae vs. 180.4 mm, C. karenae ), it seems rather unlikely. The carapace width to length ratios of adult Calappa species do not usually vary by more than 0.2 even when considering changes associated with size are considered (unpublished data; based on 10 C. calappa adult males with CW greater than 100.0 mm).

From the colour photograph of C. yamasitae ( Sakai 1980: frontispiece fig. 2), this species also appears to possess a more depressed hepatic (similar to C. gallus ) region than C. karenae sp. nov. The curvatures of the antero-lateral margins of both species are different. It is more when compared with convex in C. yamasitae than C. karenae sp. nov., although this is likely due to the relative width differences between the two species. The lateral spines along the clypeiform expansions on the posterolateral margin of the carapace points laterally in C. yamisitae but anteriorly in C. karenae sp. nov.

The dorsal crest of the chela was also described as having 9 or 10 long teeth in C. yamasitae (see Sakai 1980: 7), but there are only six such teeth in C. karenae sp. nov., and even counting the two low teeth on the proximal part of the palm, there are a total of eight ( Fig. 4 A, B). The teeth of the dorsal crest are more acute in C. karenae sp. nov.; they are higher and have narrower bases than those seen in C. yamasitae . The front also does not protrude very much in C. yamasitae (see Sakai 1980: frontispiece fig. 2, text fig. 2a) while it does so prominently in C. karenae sp. nov. ( Figs. 1 , 2 A, B). Sakai (1980: 6) described the front of C. yamasitae as “consisting of two median obtuse teeth, which are separated medially by a U-shaped sinus”. The frontal margin of C. karenae comprises two relatively sharp teeth, separated by a deeper U-shaped sulcus instead.

More importantly, the male abdominal somite 6 of C. yamasitae is more transversely rectangular, with the telson evenly triangular, and the lateral margins of both structures are convex ( Sakai 1980: text fig. 3b). In contrast, the male somite 6 is quadrate, with curved, concave lateral margins and the telson more elongated, with straight lateral margins in C. karenae sp. nov. ( Fig. 3 B). The G1 is also relatively more slender in C. karenae sp. nov. ( Fig. 5 B, C), with the median and basal parts proportionately stouter in C. yamasitae ( Sakai 1980: text fig. 3c)

The new species also resembles species in the C. japonica Ortmann, 1892 , group, which includes C. exanthematosa Alcock & Anderson, 1894 , and C. africana Lai & Ng, 2006 (see Ng et al. 2011), especially in the general form of the mammary-like granules on the carapace. Other than the different colour patterns, C. karenae sp. nov. can be separated from C. japonica , C. exanthematosa and C. africana by its much broader carapace, more deeply clefted distal margin of the first maxilliped endopod, the rounded rather than triangular and compressed proepistome, and proportionately broader groove on the pterygostomian lobe (cf. Lai & Ng 2006; Ng et al. 2011).

The use of deep-water traps in Guam and the rest of the Mariana Is have already uncovered many new and/or rare species of homolids, poupiniids, inachids and mathildellids ( Eldredge 1980; Williams & Moffitt 1991; Ng & Wang 2002; Crosnier & Ng 2004). The present discovery of Calappa karenae sp. nov. attests to the value of using trapping in areas with deep steep cliffs which cannot be sampled by trawls or dredges (see Mendoza et al. 2010).

Figures

FIGURE 1. Calappa karenae sp. nov. Paratype male (89.61 mm) (USNM 1150291), Guam. Colour in life, photograph by Roy Kropp.

FIGURE 2. Calappa karenae sp. nov. Holotype male (180.44 by 95.92 mm) (USNM 1150290), Guam. Differently angled dorsal views to show features and convexity of the carapace.

FIGURE 3. Calappa karenae sp. nov. Holotype male (180.44 by 95.92 mm) (USNM 1150290), Guam. A, frontal view of carapace; B, ventral view showing anterior thoracic sternites, distal abdominal somites and telson; C, ventral view showing posterior thoracic sternites and proximal abdominal somites.

FIGURE 4. Calappa karenae sp. nov. Holotype male (180.44 by 95.92 mm) (USNM 1150290), Guam. A, outer view of right chela, carpus and merus; B, outer view of left chela; C, dorsal view of merus and carpus of left cheliped; D, frontal view showing third maxillipeds, front, orbit, antennules and antennae.

FIGURE 5. Calappa karenae sp. nov. Holotype male (180.44 by 95.92 mm) (USNM 1150290), Guam. A, left basal antennal segment; B, C, left G 1; D, E, distal part of left G 1; F, left G 2; G, distal part of left G 2. Scale = 1.0 mm.