JOURNAL OF CRUSTACEAN BIOLOGY, 29(3): 419-427, 2009
TWO NEW CAVERNICOLOUS SPECIES OF THE GENUS SUNDATHELPHUSA FROM WESTERN SAMAR, PHILIPPINES (DECAPODA: BRACHYURA: PARATHELPHUSIDAE) Daniel Edison M. Husana, Tohru Naruse, and Tomoki Kase (DEMH, correspondence,
[email protected]) Department of Natural Environmental Studies, Graduate School of Frontier Science, the University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan; (TN,
[email protected]) Raffles Museum of Biodiversity Research, Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Republic of Singapore 117543 (Present address: Transdisciplinary Research Organization for Subtropical and Island Studies, University of the Ryukyu, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan); (TK,
[email protected]) Department of Geology and Paleontology, National Museum of Nature and Science, 3-23-1 Hyakunincho, Shinjuku-ku, Tokyo, 169-0073 Japan ABSTRACT Two new troglobitic species of the freshwater crab genus Sundathelphusa (Parathelphusidae), S. waray, n. sp., and S. lobo, n. sp., are described from two caves in Samar, Philippines. This discovery brings the number of cavernicolous species of Sundathelphusa in the Philippines to nine. It is the first record of freshwater and true cavernicolous crab species from Samar. These two new species are morphologically closely related to S. cavernicola Takeda, 1983 and S. hades Takeda and Ng, 2001, but differ distinctly in the shape of carapace and the presence of long corneous spines in the dactyli. The new species are characterized by the non-pigmented body, greatly reduced eyes and long ambulatory legs that are associated with previously known troglobitic crabs. The presence of corneous spines on the distal two segments of the ambulatory legs is suggested as troglomorphic adaptation to subterranean habitat. A key to the cavernicolous freshwater crabs of the Philippines is also provided.
KEY WORDS: caves, Parathelphusidae, Philippines, Sundathelphusa, troglomorphy DOI: 10.1651/08-3081.1
morphological adaptation to cave habitats. A key to the cavernicolous species of Sundathelphusa from the Philippines is also provided. The two new species described here are the first record of freshwater and true cavernicolous crab species in Samar, Philippines. Measurements provided are carapace width (CW) by carapace length (CL). The terminology essentially follows that of Ng and Sket (1996). Specimens examined were deposited at the National Museum of the Philippines, Manila (NMCR); National Museum of Nature and Science (formerly National Science Museum), Tokyo (NSMT); and the Zoological Reference Collection (ZRC), Raffles Museum of Biodiversity Research, National University of Singapore. The abbreviations G1 and G2 are used for male first and second gonopods, respectively.
INTRODUCTION Cavernicolous species with troglobitic morphologies are well represented in several families of brachyuran crabs such as Sesarmidae, Varunidae, Gecarcinidae, Hymenosomatidae, Potamidae, Trichodactylidae, Pseudothelphusidae and Parathelphusidae (Holthuis, 1964, 1979; Rodriguez, 1985; Guinot, 1988; Ng, 1991a, b; Ng et al., 1994, 1996; Ng and Guinot, 2001; Naruse et al., 2008; Yeo and Ng, 1999). The parathelphusid genus Sundathelphusa Bott, 1969, currently contains 28 species from the Philippines, Sulawesi, Moluccas, and Borneo (Chia and Ng, 2006; Ng et al., 2008). Several species of Sundathelphusa have a hypogean lifestyle with varying degrees of morphological adaptation to subterranean environments, as is the case with other families of the true freshwater crabs (Holthuis, 1979; Guinot, 1988; Ng and Goh, 1987; Ng, 1992; Yeo, 2001). In the Philippines, seven cavernicolous species of Sundathelphusa have been described: S. longipes (Balss, 1937) from Quezon, Luzon; S. cavernicola (Takeda, 1983), S. boex Ng and Sket, 1996, S. sottoae Ng and Sket, 1996, S. urichi Ng and Sket, 1996, and S. vedeniki Ng and Sket, 1996, all from Bohol; and S. hades Takeda and Ng, 2001 from Mindanao. Speleological explorations in the Philippines by the first author produced specimens of cavernicolous Sundathelphusa from two caves in Samar (Fig. 1). These crabs possess unusual long spines in the inner margin of the merus of the cheliped as well as in distal segments of the ambulatory legs. We determined that there are two distinct species represented in this collection, and we here describe both these species as new. We discuss briefly their
SYSTEMATICS Parathelphusidae Alcock, 1910 Sundathelphusa Bott, 1969 Comparative Materials Examined.—The specimens examined for comparative purposes were as follows: Sundathelphusa cavernicola Takeda 1983: holotype female (25.7 3 21.0 mm), NSMT-Cr 8937, Quinapon-an Cave, Antequera, Bohol, Philippines, 9u499380N, 123u549100E, coll. S. I. Ueno, 4 March 1983; 1 = (18 3 15.4 mm), 1 R (29.2 3 24 mm), NSMT-Cr 14130, Bongkawi Cave, Antequera, Villa Aurora, Bohol, Philippines, coll. P. K. L. Ng, 16 December 2000; 1 = (26.5 3 21.6 mm), 2 R (23.1 3 18.1, 26.5 3 21.8 mm), ZRC 2000.2079, Bongkawi Cave, 419
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Sundathelphusa waray, n. sp. Figs. 2-4 Material Examined.—Holotype: male (33.4 3 25.8 mm), NMCR 27059, Langun Cave, Calbiga, Western Samar, Philippines, 11u39.0229N, 125u02.9919E, coll. D. E. Husana, 28 October 2006. Paratypes: 1 R (32.8 3 26.4 mm), ZRC 2008.0008, 1 = (39 3 23.6 mm), NSMT-Cr 17985, same locality data as holotype.
Fig. 1. Map showing the sampling localities.
Antequera, Villa Aurora, Bohol, Philippines, coll. B. Sket, 23 February 1999; 1 R (22.2 3 17.8 mm), ZRC 2001.0335, Bongkawi Cave, Antequera, Villa Aurora, Bohol, Philippines, coll. P. K. L. Ng, December 2000; 3 = (13.0 3 15.130.8 3 24.1 mm), Canantong Uno cave, Quinapon-an, Antequera, Villa Aurora, Bohol, Philippines, coll. B. Sket, 25 February 1999; Sundathelphusa boex Ng and Sket, 1996: 1 = (40.9 3 32.8 mm), ZRC 1996.1549, paratype, Batuan, Bohol, Philippines, coll. B. Sket, February 1995; 1 = (34.3 3 28.0 mm), 1 R (26.8 3 22.0 mm), ZRC 1996.1550-1551, paratypes, Castigio Cave, Batuan, Bohol, Philippines, coll. B. Sket, February 1995. Sundathelphusa sottoae Ng and Sket, 1996: 1 R (26.2 3 21.1 mm), ZRC 1996.1553, paratype, Bonugan, Batuan, Bohol, Philippines, coll. B. Sket, February 1995; 1 = (17.5 3 14.4 mm), ZRC 1996.1548, open well, Batuan, Bohol, Philippines, coll. B. Sket, February 1995; 1 = (18.0 3 14.9 mm), ZRC 2001.0343, Bongkawi Cave, Antequerra, Villa Aurora, Bohol, Philippines, coll. P. K. L. Ng, 16 December 2000. Sundathelphusa urichi Ng and Sket, 1996: 2 broken males, 1 R (32.6 3 25.0 mm), ZRC 1996.1554-1556, paratypes, Quilas Cave, Nueva Vida Norte, Batuan, Bohol, Philippines, coll. B. Sket, February 1995. Sundathelphusa vedeniki Ng and Sket, 1996: 1 = (34.0 3 26.6 mm), ZRC 1996.1552, paratype, Boho sa Bikahan, Bikahan, Antequera, Bohol, Philippines, coll. B. Sket, February 1995. Sundathelphusa hades Takeda and Ng, 2001: holotype male (19.7 3 16.4 mm), NSMT-Cr 14274, Latay Cave, Agusan del Sur, Mindanao, Philippines 8u239N, 126u059E, coll. Cave Research Group of Meiji University, 15 November 1981; paratype female (24.9 3 20.8 mm), ZRC 2001.1000, Sta. Rita Thinking Cave, Surigao del Sur, Mindanao, coll. Cave Research Group of Meiji University, 27 November 1998.
Description.—Carapace outline (Fig. 2A) quadrate to trapezoidal, widest at anterior quarter, dorsal surface convex longitudinally. Frontal region sloping anteroventrally; anterolateral regions inflated dorso-laterally, with oblique rows of granules of various shapes and lengths; cervical groove shallow; H-shaped gastric groove deep; epigastric and postorbital regions only with clusters of granules, no cristae. Frontal margin broadly protruded, two lobes clearly separated with deep broad median concavity; external orbital tooth (Fig. 3) low, less produced anteriorly, outer margin slightly longer than inner margin, margins granulated; epibranchial tooth low, blunt, separated from external orbital tooth by a shallow notch; anterolateral margin gently convex, lined with large granules, not clearly demarcated from posterolateral margin; posterolateral margin gently concave, converging gradually towards posterior margin of carapace. Frontal medial triangle (Fig. 2B) complete; dorsal and lateral margins distinct, granulose; lateral margins gently protruded over lateral ends of dorsal margin; orbit well demarcated; supraorbital margin granulated, sinuous; infraorbital margin beaded with distinct granules; outer edge reaching and fused with anterolateral margin; suborbital and subbranchial regions covered with scattered oblique long and short striae of small granules; pterygostomial region smooth with streak of oblique ridges on upper outer part. Posterior margin of epistome trilobed, median lobe large, subtriangular, lateral lobes wider and less protruded, placed more anteriorly than median lobe. Eyes (Fig. 2B) reduced, tapering, cornea with pigment, occupying one-third of orbit. Basal antennular segment large, subquadrate, flagellum long; antenna with long flagellum, distal end reaching beyond external orbital angle when stretched laterally. Ischium of third maxilliped rectangular, bearing distinct oblique submedian sulcus; merus quadrate with shallow median depression; tip of exopod reaching to midpoint of outer margin of merus, with long flagellum. Chelipeds (Figs. 2, 3) not noticeably elongated, subequal, stronger in males; all margins of merus serrated, serration more distinct in ventral outer and inner margins, dorsal margin without distinct subdistal tooth; carpus armed with strong distal sharply pointed inner angle, flattened dorso-ventrally, laterally fringed with proximal teeth; palm minutely granulated outer surface; dorsal inner margin armed with a row of long spines, ventral margin with scattered shorter granules; fingers robust, cutting edge armed with many sharp teeth of various sizes. Ambulatory legs (Figs. 2A, 4A) long, slender, third leg longest, merus of third leg 0.89-0.95 times CL (mean 5 0.92, n 5 2); anterior margins of meri indistinctly serrated,
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Fig. 2. Sundathelphusa waray, n. sp., paratype ZRC 2008.0008, female. A, habitus, dorsal view; B, cephalothorax, anterior view. Scale bars 5 10 mm in A, 5 mm in B.
without subdistal tooth or spine, posterior margins serrated on first to fourth legs, prominent and distinct on first leg but gradually disappearing and almost indistinct on fourth leg; carpi short, with longitudinal submedian ridge on dorsal surface, widened distally, outer margins indistinctly serrated; propodi armed with rows of very long spines on
Fig. 3. Right cheliped of Sundathelphusa waray, n. sp., holotype NMCR 27059, male. Scale bar 5 5 mm.
inner margins, outer margins with rows of very small spines; dactyli armed with rows of strong and long spines on all margins, spines at inner margins of first to third dactyli about four times longer than those at outer margins, spines of both outer and inner margins of fourth dactylus almost equal in length. Male pleonal cavity reaching level of proximal quarter of cheliped coxae. Male pleon (Fig. 4B) T-shaped; first segment very short, proximal and distal margins sinuous; second segment transversely subrectangular; third to fifth segments convergent distally, lateral margins of third segment convex, lateral margins of fourth and fifth segments slightly concave; sixth segment rectangular, longer than broad, lateral margins slightly concave; telson subtriangular, longer than broad, lateral margin slightly concave, rounded distally. G1 (Fig. 4C, D) relatively slender, curved outward by distal half; outer margin of subterminal segment distinctly concave; terminal segment straight, tapering, cylindrical, slightly setose. Variation.—The anterolateral-branchial regions of the only female specimen (ZRC 2008.0008, paratype, 32.8 3
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Fig. 4. Sundathelphusa waray, n. sp., holotype NMCR 27059, male, NMCR 27059. A, right second ambulatory leg, ventral view; B, pleon and telson; C, left G1, ventral view; D, distal part of left G1, dorsal view; E, left G2, ventral view; F, distal part of left G2, inner view. Scale bars 10 mm in A and B, 1 mm in C-F.
26.4 mm) appear to be less laterally swollen than in males. The female paratype also has more pointed inner angle of the carpus of the chelipeds and more serrated anterior margins of the ambulatory meri when compared with those of the male specimens. Etymology.—Named after the local dialect (Waray) and the local people (Waray) who are known for their bravery, used as noun in apposition. Remarks.—Sundathelphusa waray is distinguished from its known congeners by the presence of long spines in the inner margin of the merus of the chelipeds as well as in the margins of the propodi and dactyli of the first to fourth ambulatory legs. Sundathelphusa cavernicola Takeda, 1983, also possesses relatively long spines on the propodi of the ambulatory legs, however, the spines of S. waray are
much longer than those of S. cavernicola. Furthermore, the widest point of the carapace in S. waray is further forward than in S. cavernicola. The shape of the male pleon of S. waray also differs from that of S. cavernicola in having a generally wider appearance and a shorter sixth segment compared to a generally narrow pleon with a longer sixth segment. Lastly, the G1 of S. waray is more slender than that of S. cavernicola (Figs. 2A, 4A-D; Takeda, 1983: figs. 1, 2A, E, G, H). Sundathelphusa waray resembles Sundathelphusa hades Takeda and Ng, 2001 in that both possess strongly reduced eyes with a small trace of pigmentation at the tip of the cornea (see Figs. 2B, 8A, D; Takeda and Ng, 2001: figs. 1c, 2b), and a similar-shaped male pleon (Fig. 4B); S. waray differs from S. hades as follows: in S. waray, the carapace is wider and trapezoidal, with the widest part on its
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Fig. 5. Sundathelphusa lobo, n. sp., holotype NMCR 27061. A, habitus, dorsal view; B, cephalothorax, anterior view. Scale bars 5 10 mm in A and 5 mm in B.
anterolateral to branchial regions that are dorsally swollen, the anterolateral margins are prominently serrated, the outer edge of the infraorbital margin reaches and fuses with the anterolateral margin, the merus of the third maxilliped is quadrate, the G1 is strongly curved outwards, and the terminal segment of the G1 is proportionately longer than the subterminal segment. In contrast, in S. hades, the carapace is narrower and rather squarish, with its widest point at the anterior one-third, the anterolateral margin is granulated but not prominent, the merus of the third maxilliped is subquadrate, the curvature of the G1 is weaker, and the terminal segment of the G1 is proportionately shorter than the subterminal segments (Figs. 2, 4C, D; see also Takeda and Ng, 2001, figs. 1a-c, e, 2a, b, d, 3c-f).
NMCR 27062, same data as holotype; 2 = (21.6 3 17.5, 18 3 14.8 mm), NSMT-Cr 17986, 1 = (22.2 3 17.7 mm), ZRC 2008.0009, 1 R (21.5 3 17.0 mm), NSMT-Cr 17987, same data as holotype.
Sundathelphusa lobo, n. sp. Figs. 5-7 Material Examined.—Holotype: male (31.5 3 24.3 mm), NMCR 27061, Lobo Cave, Jiabong, Western Samar, Philippines 11u46.7869N, 124u55.7329E, coll. D. E. Husana, 1 August 2006. Paratypes: female (29.1 3 22.4 mm),
Fig. 6. Right cheliped of Sundathelphusa lobo, n. sp., holotype NMCR 27061, male. Scale bar 5 5 mm.
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Fig. 7. Sundathelphusa lobo, n. sp., holotype NMCR 27061, male. A, right second ambulatory leg, ventral view; B, left G1, ventral view; C, distal part of left G1, dorsal view; D, left G2, ventral view; E, distal part of left G2, inner view. Scale bars 5 5 mm in A and 1 mm in B-E.
Description.—Carapace outline (Fig. 5A) quadrate to trapezoidal, widest at anterior quarter, dorsal surface convex longitudinally. Frontal region sloping antero-ventrally; anterolateral regions inflated dorso-laterally, with rows of granules of various shapes and lengths; cervical groove shallow; H-shaped gastric groove deep; epigastric and postorbital regions only with clusters of granules, no cristae. Frontal margin broadly protruded, two lobes clearly separated with deep broad median concavity; external orbital tooth produced anteriorly, with sharp tip, outer margin slightly longer than inner margin, margins granulated; epibranchial tooth distinct, triangular, well separated from external orbital tooth by a deep notch, tapering anteriorly; anterolateral margin gently convex, armed with strong granules, not clearly demarcated from posterolateral margin; posterolateral margin gently concave, converging gradually towards posterior margin of carapace. Frontal medial triangle complete; dorsal and lateral margins distinct, granulose; lateral margins gently protruded than dorsal; orbit well demarcated; supraorbital margin granulated, sinuous; infraorbital margin beaded with distinct granules; outer edge
reaching and fused with anterolateral margin; suborbital and subbranchial regions covered with scattered oblique long and short striae of small granules; pterygostomial region smooth with streak of oblique ridges on upper outer part. Posterior margin of epistome with three lobes, median lobe large, subtriangular; lateral lobes wider and less protruded, placed more anteriorly than median lobe. Eyes (Fig. 5B) reduced, tapering, pigmentation of cornea barely present, occupying about half of orbit. Basal antennular segment large, subquadrate, flagellum long; antenna with long flagellum, distal end reaching beyond external orbital angle when stretched laterally. Ischium of third maxilliped rectangular, bearing distinct oblique submedian sulcus; merus quadrate with shallow median depression, antero-external angle convex, slightly higher than base of carpus, anterior margin concave; tip of exopod reaches midpoint of outer margin of merus, with long flagellum. Chelipeds (Figs. 5A, 6) not noticeably elongated, subequal and stronger in males; dorsal margin of merus serrated, ventral outer and inner margins armed with long
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spines of various length, dorsal margin without distinct subdistal tooth; carpus armed with strong distal sharply pointed inner angle, flattened dorso-ventrally, laterally fringed with proximal teeth; palm with minutely granulated outer surface; dorsal inner margin armed with a row of long spines, ventral margin with scattered shorter granules; fingers robust, cutting edges armed with many sharp teeth of various sizes having largest at midpoint while smaller on distal and proximal sides. Ambulatory legs (Figs. 5A, 7A) very long, slender, third leg longest, merus of third leg 1.02-1.13 times CL (mean 5 1.08, n 5 4); anterior margins of meri indistinctly serrated, without subdistal tooth or spine, posterior margins serrated on all legs, very prominent and distinct on first leg but gradually disappearing and almost indistinct on fourth leg; carpi short, with longitudinal submedian ridge on dorsal surface except for fourth leg, widened distally, outer margins indistinctly serrated; propodi armed with rows of very long spines on inner margins, outer margins only with rows of very short spines; dactyli armed with rows of strong and long spines on all margins, spines at inner margins of first to third dactyli about four times longer than those at outer margins, spines of both outer and inner margins of fourth dactyli almost equal in length. Male pleonal cavity reaching level of proximal quarter of cheliped coxae. Male pleon narrow, T-shaped; first segment very short, proximal and distal margins sinuous; second segment transversely subrectangular; third to fifth segment narrows gradually; lateral margins of third segment convex, lateral margins of fourth and fifth segments slightly concave; sixth segment rectangular, longer than broad, lateral margins concave on proximal but convex at distal end; telson subtriangular, longer than broad, lateral margin almost straight but with a slight concavity on its proximal end, rounded distally. G1 (Figs. 7B, C) relatively slender, slightly bending outward at middle, distal half almost straight; outer margin of subterminal segment slightly concave; terminal segment straight, tapering, cylindrical, slightly setose. Etymology.—Named after its type locality, Lobo Cave, used as noun in apposition. Remarks.—Sundathelphusa lobo has a suite of characters very similar to S. waray, but there are also many morphological differences between these two species. The external orbital tooth of S. lobo is more pointed and more produced anteriorly compared to S. waray (compare Figs. 2A, 3 and 5A, 6). The epibranchial tooth is distinct and separated from the external orbital tooth by a deep, triangular notch contrary to S. waray, which has the epibranchial tooth separated from the external orbital tooth by a small notch (Fig. 5A vs. 2A). The ambulatory legs of S. lobo are proportionately longer than of S. waray (e.g., length of merus of third ambulatory leg to CL, 1.02-1.13 versus 0.89-0.95). The G1 also differs between the two species: S. lobo has a slender and slightly laterally-curved G1 with a straight distal part (Fig. 7B, C) compared to S. waray which has distinctly laterally-curved G1 (Fig. 4C, D).
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DISCUSSION Habitat Description The two new species described here were collected in two freshwater caves in Samar Island, Philippines, named Langun Cave and Lobo Cave (Fig. 1). Langun Cave is located in Calbiga, Western Samar. Its entrance is at an elevation of around 150 m above sea level. Specimens of Sundathelphusa waray were found in two locations inside Langun Cave, one was in the cave’s biggest chamber (approximating a football stadium) and the other was in smaller adjacent chamber, these chambers are located ca. 200 m and 150 m from the entrance respectively and are ca. 300 m apart separated by a huge limestone body. Live specimens were collected from the shallow stream and mud holes along the subterranean rivers. A huge opening between the two chambers acts as a passageway for migrating bats and birds. These animals produce large amounts of guano on the cave floors. During the rainy season, the water in the streams is between three to five meters higher than the dry season level as evidenced by watermarks on the walls. Flooding is known to be important agent in supplying nutrients for animals in the cave (Hawes, 1939). Lobo Cave is located in Jiabong, about 20 km northwest of Langun Cave, and with an altitude of ca. 30 m above sea level. A subterranean river flows along the cave floor and drains outside the cave through one of its two entrances. Specimens of Sundathelphusa lobo were collected from a shallow stagnant pool (about two meters wide by a meter deep with muddy substrate) in a small chamber during dry season. When the water level in the stagnant pool goes up during rainy season, crabs migrate upstream into a bigger chamber with shallow water (personal observation by DEMH). Lobo Cave appears to receive less nutrients than Langun Cave because stockpiles of guano deposits, seemingly a major food source for the crabs, were not observed. Although the Langun and Lobo caves are located in the same Miocene limestone formation (unpublished geological map by Mines and Geosciences Bureau, Philippines), the two are likely to belong to separate cave systems. The two caves are over 20 km apart, with a large marine embayment in between (Fig. 1). In addition, the limestone formation forms a large anticline with a north-south axis, and the two caves were located in the east and west wings of this geologic structure respectively, between which lies thick non-calcareous clastic sediments. Therefore, there is no possibility that the two caves are connected underground. Systematic Issues The present study brings the total number of cavernicolous species of Sundathelphusa in the Philippines to nine (Table 1). The two new species described here, as well as S. hades and S. cavernicola, have been found in deeper parts of the caves, and can likely be regarded as obligate cave inhabitants. On the other hand, the following species were found in various habitats in karstic areas: S. longipes and S. boex were found both in caves and epigean rivers; S.
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Table 1. Habitat and morphological characters of cavernicolous species of Sundathelphusa from the Philippines. Characters Species
S. S. S. S. S. S. S. S. S. 1 2 3
cavernicola (Takeda) lobo, n. sp. hades Takeda and Ng waray, n. sp. sottoae Ng and Sket urichi Ng and Sket boex Ng and Sket longipes (Balss) vedeniki Ng and Sket
Habitat
cave cave cave cave cave and well cave cave and river cave and river cave and well
Cornea pigment 2
reduced reduced reduced reduced intermediate intermediate well-developed well-developed well-developed
Eyestalk1
Body pigment
Dactyli spines
Legs
very short very short very short very short short short short/long short/long short/long
absent absent absent absent slightly reduced poorly pigmented well-pigmented slightly reduced well-pigmented
long long short3 long intermediate short short short short
long long long long intermediate short short intermediate short
See also Ng, 1991b; fig. 4, Ng and Sket, 1996; and Takeda, 2001. Pigmentation very apparent in juveniles. Based upon only one, seemingly juvenile specimen.
sottoae, S. urichi and S. vedeniki from wells and caves (see also Ng and Sket, 1996). These species appear to be facultative cave dwellers. The species of Sundathelphusa in the Philippines exhibits a suite of morphological characters as a consequence of various degrees of adaptation from epigean to subterranean habitats, which include reduction of pigment in the cornea, reduction in the length of the eyestalk, absence or reduction of pigment in the integument, and elongation of legs, all of which are well-known adaptations in cave crustaceans (see Guinot, 1988; Rodriguez, 1985; Culver et al., 1995; Ng and Guinot, 2001; Naruse et al., 2005; Medı´a-Ortı´z and Hartnoll, 2006). The discovery of the two additional cavernicolous species described here further emphasizes the presence of such morphological trend in Sundathelphusa. The presence of long corneous spines on the dactyli of the new species described here is noteworthy. These structures were observed by Takeda (1983) in S. cavernicola, who suggested it as a troglomorphic character (see Christiansen, 1992). Aside from Sundathelphusa, long corneous spines are also present in the caveobligate Neostrengeria sketi Rodriguez, 1985 (Pseudothelphusidae) from Colombia. Corneous spines on the dactylus are very short in cave-facultative and epigean species. The presence of long corneous spines on the two cavernicolous species described here further emphasizes the troglomorphic nature of such structures, particularly with regards to decapod crustaceans. The utility of such a condition still remains unknown. However, modifications or developments of some organs are important features and necessary in various cave animals as part of their adaptation to cave environment (Hu¨ppop, 2000). For example, Mejı´a-Ortı´z and Hartnoll (2006) found setae on the surface of the reduced cornea of cavernicolous shrimps belonging to three different genera, whereas the epigean species of the same genera have no such modifications. They suggested that the setae in these species have either a tactile or chemosensory function. Another study shows that elongation of the antennae of cave-obligate species (troglomorphism) (Culver et al., 1995; Hu¨ppop, 2000; Ipsen, 2000) is also an important feature in coping with the extreme condition of the cave environment. Furthermore, Ng and Guinot (2001) suggested that the anchialine cave gecarcinid Discoplax
longipes Ng and Guinot, 2001 uses the long second and third ambulatory legs as feelers to cope with the dark subterranean habitats. Since the regression of optical organs may represent a tradeoff and should be compensated with progressive development of non-visual sensory organs in response to the selective pressure of the cave environment (Vandel, 1965; Culver et al., 1995; Langecker, 2000; Mejı´a-Ortı´z and Hartnoll, 2006) we here suggest that the long corneous spines on dactyli together with its long ambulatory legs function as tactile organs that give the troglobitic Sundathelphusa an advantage in totally dark cave habitats. Key to the cavernicolous species of Sundathelphusa from the Philippines 1. Eyes strongly reduced, tapering, with small trace of pigmentation . . . 2 –. Eyes normal to moderately reduced, with distinct trace of pigmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Ambulatory propodi and dactyli lined with short spines, spines on propodi especially small; carapace apple-shaped, widest on anterior two-fifths. . . . . . . . . . . . . . . . . . S. hades Takeda and Ng, 2001 [Takeda and Ng, 2001: figs. 1-3] [Mindanao] –. Ambulatory propodi and dactyli lined with long corneous spines; carapace widest on anterior quarter . . . . . . . . . . . . . . . . . . . . . . 3 3. Cheliped of both male and female with granulated ventral margins of merus and dorsal margin of manus; eye occupying about half of orbit; infraorbital margin produced anteriorly, almost on same level with external orbital angles in frontal view. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. cavernicola Takeda, 1983 [Takeda, 1983: figs. 1, 2] [Bohol] –. Cheliped of both male and female with ventral margins of merus and dorsal margin of manus serrated; eye occupying about one-third of orbit; infraorbital margin not produced anteriorly, distinctly posterior to level of external orbital angles in frontal view . . . . . . . . 4 4. External orbital tooth less pointed and less produced anteriorly; epibranchial tooth low and separated from external orbital tooth by a small notch; third ambulatory leg shorter, with merus 0.89-0.95 times CL; G1 strongly curving laterally . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. waray, n. sp. [Figs. 2-4] [Samar] –. External orbital tooth more pointed and more produced anteriorly; epibranchial tooth distinct and separated from the external orbital tooth by a deep and triangular notch; third ambulatory leg longer, with merus 1.02-1.13 times CL; G1 gently curving laterally . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. lobo, n. sp. [Figs. 5-7] [Samar] 5. Eye well developed, occupying almost entire orbit . . . . . . . . . . . 6 –. Eye somewhat reduced, occupying less than two-thirds of orbit . . . . 8 6. Ambulatory legs relatively stout, short, merus of third ambulatory leg more than 0.80 times carapace length (after Ng, 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. longipes (Balss, 1937) [Balss, 1937: figs. 15, 16] [Quezon, Luzon]
HUSANA ET AL.: NEW CAVERNICOLOUS FRESHWATER CRABS FROM PHILIPPINES
–. Ambulatory legs relatively stout, short, merus of third ambulatory leg less than 0.71 times carapace length . . . . . . . . . . . . . . . . . . . 7 7. Carapace gently convex, posterolateral margins gently convergent posteriorly. . . . . . . . . . . . . . . . . . . . S. boex Ng and Sket, 1996 [Ng and Sket, 1996: figs. 1A; 2a-f; 4a-f] [Bohol] –. Carapace distinctly convex, posterolateral margins strongly convergent posteriorly. . . . . . . . . . . S. vedeniki Ng and Sket, 1996 [Ng and Sket, 1996: figs. 1D; 3g-l; 4q, r] [Bohol] 8. Carapace with moderately convex anterolateral margin; ambulatory legs with proportionately longer and straight dactyli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. sottoae Ng and Sket, 1996 [Ng and Sket, 1996: figs. 1B; 2h-k; 4h-l] [Bohol] –. Carapace swollen dorsolaterally; ambulatory legs with proportionately shorter and more falcate dactyli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. urichi Ng and Sket, 1996 [Ng and Sket, 1996: figs. 1C; 3a-f; 4m-p] [Bohol]
ACKNOWLEDGEMENTS The first author, DEMH, is grateful to S. Kojima (Oceanographic Institute, the University of Tokyo) for the supervision of his graduate research. He is also deeply indebted to P. K. L. Ng (Department of Biological Sciences, the National University of Singapore) for sharing his expertise on crab taxonomy and especially for providing funding for his short-term visit to NUS (grant No. R-154-000-334-112). He also extends his gratitude to J. Bonifacio for assistance in cave explorations, Komatsu (National Museum of Nature and Science, Tokyo) for providing access to materials deposited in the museum, and lastly, to his wife V. P. Husana for her patience and unselfish support to his study. We also thank J. C. E. Mendoza (Department of Biological Sciences, the National University of Singapore) for his review of this paper. Lastly, we thank the two anonymous reviewers who painstakingly reviewed this manuscript and for their helpful comments and suggestions that helped improve this paper. This research was permitted by Department of Environment and Natural ResourcesProtected Area and Wild Life Bureau (DENR-PAWB), Philippines and was funded by the Sasakawa Scientific Research Grant from Japan Science Society (No. 18-805M) to DEMH, the Japanese Government (Monbukagakusho) Scholarship program to DEMH, and by grants from the Japan Society for the Promotion of Science (No. 18253007) and National Museum of Nature and Science, Tokyo to TK.
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