Lithodes formosae, Ahyong, Shane T. & Chan, Tin-Yam, 2010

Ahyong, Shane T. & Chan, Tin-Yam, 2010, Lithodes formosae, a new species of king crab from Taiwan (Crustacea: Decapoda: Lithodidae), Zootaxa 2332, pp. 61-68 : 62-67

publication ID	https://doi.org/ 10.5281/zenodo.275486
DOI	https://doi.org/10.5281/zenodo.3510878
persistent identifier	https://treatment.plazi.org/id/03828796-FFC3-C27F-3595-FEB2FB76F977
treatment provided by	Plazi
scientific name	Lithodes formosae
status	sp. nov.

Treatment

Lithodes formosae View in CoL sp. nov.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Lithodes View in CoL sp. — Macpherson & Chan, 2008: 47 View Cited Treatment –48.

Type material. NTOU A01090, ovigerous female holotype (cl 78.4 mm, pcl 55.9 mm, cw 54.7 mm), off Dasi, Ilan County, northeastern Taiwan, commercial trawl, 500–600 m, coll. T. Y. Chan, 6 June 1998.

Diagnosis. Carapace dorsal surface with long, slender spines; gastric region with 4 upright spines, anterior pair longer than half length of hepatic spine, posterior pair half length of hepatic spine; cardiac and intestinal regions each with 2 long upright spines; branchial surface with 2 long upright spines. Branchial margins with 2 primary, laterodorsally directed spines positioned at a level between pereopods 2 and 3, and between pereopods 3 and 4, respectively (anterior spine 1/3 length of hepatic spine, posterior spine 1/6 length of hepatic spine); margin between posterior primary branchial spine and intestinal spine with 5 protrusions of which 2 or 3 are developed as short spines. Adult rostrum shorter than half pcl; proximal half strongly upraised by about 45°. Abdominal somite 2 comprising 3 separate plates in adults. Antennal peduncle segment 2 with slender outer spine reaching midlength of segment 4. Chelipeds unequal; palms generally smooth, with low tubercles on dorsal surface. Ambulatory legs spinose; surface between major spines smooth or with very few, scattered spines. Merus about as long as pcl, length less than 7 times height. Propodus length 11–12 times height. Dactylus half length of propodus; flexor margin with 6 or 7 minute, widely spaced corneous spines.

Description of female holotype. Carapace: Pyriform, about as long as wide; regions indicated; dorsal surface armed with long, slender spines and scattered, widely separated granules. Hepatic spine longest of carapace spines (0.4 pcl), directed anterolaterally. Gastric region convex, with 2 pairs of long, upright spines, anterior pair longer than half length of hepatic spine, posterior pair half length of hepatic spine. Cardiac region and intestinal regions each with pair of long upright spines, as long as anterior gastric spines. Branchial surface with 2 long upright spines: 1 spine at level of pereopod 3 coxa (almost as long as hepatic spine); 1 spine at level of pereopod 4 coxa (slightly longer than anterior gastric spines), without conical tubercle at base of posterior spine. Branchial margins with 2 primary, laterodorsally directed spines positioned at a level between pereopods 2 and 3, and between pereopods 3 and 4, respectively (anterior spine 1/3 length of hepatic spine, posterior spine 1/6 length of hepatic spine); with 2 low tubercles anterior to first primary branchial spine, and 2 low tubercles between primary branchial spines; margin between posterior primary branchial spine and intestinal spine with 5 protrusions of which 2 or 3 are developed as short spines. Pterygostomian region granulate or tuberculate, with small, anterior, submarginal granule.

Rostrum and orbit: Rostrum 0.4 pcl, comprising proximal and distal portions; proximal portion dorsally angled by about 45°, with pair of divergent dorsal spines reaching to midlength of distal portion of rostrum; distal portion subhorizontal, distally bifurcate for half length, forming pair of divergent spines; basal subrostral spine elongate, extending anteriorly beyond apices of outer orbital spine. Posterior orbital margin concave; outer orbital spine directed anteriorly, slightly shorter than anterolateral spine, reaching to end of cornea.

Ocular peduncle: Longer than cornea; unarmed.

Antennule: Peduncle unarmed, reaching anteriorly beyond antennal peduncle by about 2/3 length of distal antennular peduncle segment.

Antenna: Basal segment unarmed; outer margin of segment 2 with slender spine, reaching midlength of segment 4; segment 3 unarmed; scaphocerite minute, obsolete, blunt, shorter than segment 4; segment 4 unarmed, about half length of segment 5.

Abdomen: Somite 1 with low blunt triangular teeth on posterior margin. Somite 2 rugose; composed of 3 distinct plates separated by narrow suture; median surface with pair of low submedian teeth; posterior margin with 4 low prominences; lateral margins of lateral plates irregularly dentate. Somites 3–5 with nodular median plates; surface of lateral plates pitted, irregular, rugose; marginal plates with left margin irregularly crenulate (fused with laterals), right marginals subdivided, with angular to pointed apices. Somite 6 longer than wide, distal margin with 2 small distal tubercles. Telson rounded, unarmed.

Chelipeds: Slightly dimorphic, unequal; spination similar. Surfaces of both chelipeds smooth or with scattered granules in addition to major spines. Coxa with tufts of setae, unarmed; ischiobasis with 3 or 4 stout ventral spines and about 6 blunt tubercles. Merus inner margin, with stout subdistal spine and 2 or 3 smaller spines or acute tubercles; ventral margin with 2 or 3 low conical spines; dorsal and lateral surface spinose, spines largest distally. Carpus with 2 or 3 short, prominent spines on dorsal and lateral surfaces. Palms generally smooth, with low tubercles on dorsal surface.

Major cheliped 1.50 pcl; upper palm length 1.76 times height; occlusal margins of fingers corneous for distal third, proximally with 3 calcareous nodules; dactylus dorsal margin broadly convex, with rows of tufts of golden setae and blunt proximal tooth, 1.17 times longer than dorsal margin of palm.

Minor cheliped 1.51 pcl; upper palm length 2.04 times height; occlusal margin corneous for distal quarter, proximally crenulate; dactylus dorsal margin broadly convex, with rows of tufts of golden setae and blunt proximal tooth, 1.41 times longer than dorsal margin of palm.

Ambulatory legs: Similar, slender, elongate; segments spinose, surface between major spines smooth or with very few, scattered spines. Pereopod 4 longest. Distal margins of coxae unarmed; surface smooth. Ischiobasis with 2 non-setose distal spines. Merus subcircular to ovate in cross section; extensor margin with 3 or 4 larger spines intervened by 1 or 2 small spines in addition to long, prominent, distal spine; distal spine directed oblique to meral axis; flexor margin with 2 rows of 4 or 5 small spines; upper surface with irregular row of 6 or 7 small spines. Carpus about half merus length; extensor margin with distal and second proximal spines longest, exceeding half carpus length; surface with scattered small spines. Propodus compressed; with 2 rows of 5–8 small spines on extensor margin and 2–4 small spines on dorsal surface; flexor margin with 6 or 7 small spines. Dactylus distally curved, rounded in cross section distally; with 4 corneous spines proximally; extensor margin with small corneous spine at midlength; flexor margin with about 6 or 7 minute, widely spaced corneous spines; apex corneous.

Pereopod 2 length 2.64 pcl. Merus 0.95 pcl; length: height ratio 6.40. Carpus 0.52 merus length. Propodus 0.86 merus length; length: height ratio 11.04. Dactylus 0.50 propodus length.

Pereopod 3 length 2.83 pcl. Merus 1.02 pcl; length: height ratio 6.85. Carpus 0.53 merus length. Propodus 0.88 merus length, length: height ratio 12.04. Dactylus 0.53 propodus length.

Pereopod 4 length 2.91 pcl. Merus 0.99 pcl; length: height ratio 6.90. Carpus 0.58 merus length. Propodus 0.94 merus length, length: height ratio 11.64. Dactylus 0.48 propodus length.

Colour in life. ( Fig. 4 View FIGURE 4 ) Body red. Cornea dark brown. Eggs orange.

Etymology. This new species is named after a former name for Taiwan (“ Formosa ”), the type locality of the species.

Remarks. Macpherson (1988) listed 15 species of Lithodes worldwide of which seven occur in the Atlantic Ocean and eight in the Indo-Pacific. Since 1988, three species of Lithodes have been described, all from the Pacific Ocean: L. megacantha Macpherson, 1991 [type locality: French Polynesia], L. paulayi Macpherson & Chan, 2008 [type locality: Guam], and L. galapagensis Hall & Thatje, 2009 [type locality: Galapagos Islands]. Lithodes formosae sp. nov. is the nineteenth known species of Lithodes and resembles other long-spined species of the genus in which the carapace and walking legs bear long spines even as early adults — L. longispina Sakai, 1971 , L. megacantha , and L. paulayi . The new species is readily distinguished from L. longispina and L. megacantha by having two dorsal branchial spines instead of one; the first primary marginal branchial spine is considerably shorter than, rather than subequal to the hepatic spine; the second primary marginal branchial spine is considerably shorter than the first, rather than subequal; and the distolateral spine of the basal antennal segment reaches the midlength rather than end of the second segment. The new species is most similar to L. paulayi in sharing two dorsal branchial carapace spines, proportionally short primary marginal branchial spines, and similar basal antennal segment ornamentation. The two species differ in the number of marginal branchial spines between the posterior primary branchial spine and intestinal spines (5 protrusions of which 2 or 3 are developed as short spines in L. formosae sp. nov.; 6–8 spines in L. paulayi ), proportional length of the rostrum and dorsal spines (markedly longer in L. paulayi ), and spination of the chelipeds (a few dorsal tubercles on the palms in L. formosae sp. nov.; dorsal spines and lateral tubercles in L. paulayi ). The rostrum of L. paulayi is about 0.8 pcl compared to 0.4 pcl in L. formosae sp. nov. Proportional spine and rostral length decreases with increasing size in lithodids, so the difference in relative rostral length between L. formosae sp. nov. and L. paulayi is all the more significant because the holotype of the former is about half the size of that of the latter. The proportional dorsal spine length in the holotype of L. formosae sp. nov. is similar to that of the much larger holotype of L. paulayi . The paratype of L. paulayi , however, is a similar size to the holotype of L. formosae sp. nov., but in the latter, the spines are less than half the proportional length as those of the former (compare Figs 1 View FIGURE 1 , 2 View FIGURE 2 with Macpherson & Chan 2008: fig. 2a–d). Comparison of partial sequences of the cytochrome oxidase subunit I gene (COI) (658 bp) from five specimens of L. longispina from Japan (GenBank accession nos AB476813 View Materials –476817) with the respective holotypes of L. formosae sp. nov. (GenBank accession no. GU289678 View Materials ) and L. paulayi (GenBank accession no. GU289677 View Materials ) corroborates the specific status of the new species. Pairwise nucleotide divergences are 6.2% between L. formosae sp. nov. and L. paulayi , 6.3–6.8% (mean 6.5%) between L. formosae sp. nov. and L. longispina , and 6.3–6.6% (mean 6.4%) between L. paulayi and L. longispina . The interspecific divergences between the three species contrasts strongly with the intraspecific divergence of 0.2–0.8% (mean 0.4%) within L. longispina .

Lithodes formosae View in CoL sp. nov. is the second species of the genus known from Taiwan, with L. turritus Ortmann, 1892 View in CoL , recorded by Wu et al. (1998) and more recently by Macpherson & Chan (2008). The new species is readily distinguished from L. turritus View in CoL (of similar size to the holotype of L. formosae View in CoL sp. nov.) by the strongly upraised proximal half of the rostrum (45° versus less than 30°); the length of the primary marginal branchial spines, which are considerably shorter than half the length of the hepatic spine, compared to twothirds to as long as the hepatic spine; and the armature of the posterior branchial margin, which bears only low tubercles or very short conical spines compared to long slender spines in L. turritus View in CoL (compare Figs 1 View FIGURE 1 , 2 View FIGURE 2 A with Ikeda 1998: pl. 66, fig. 1, Wu et al. 1998: fig. 1).