Lissoporcellana flagellicola, Osawa, Masayuki & Fujita, Yoshihisa, 2005

Osawa, Masayuki & Fujita, Yoshihisa, 2005, A new species of Lissoporcellana (Crustacea: Decapoda: Anomura: Porcellanidae) from Okinawa, southwestern Japan, Zootaxa 1038, pp. 53-63 : 54-62

Lissoporcellana flagellicola n. sp. ( Figs. 1–4)

[new Japanese name: Muchiyagi­kakure­kanidamashi]

Type material. HOLOTYPE: CMNH­ZC 1818, male (CL 6.8 mm), off Red Beach, Kin (Kin Bay), Okinawa­jima Island, Ryukyu Islands, 12 m, associated with an unidentified species of Ellisellidae , 18 January 2005, SCUBA diving, coll. Y. Fujita. PARATYPE: CMNH­ZC 1819, 1 female (CL 7.6 mm), same data as holotype.

Diagnosis. Carapace slightly longer than broad. Rostrum trilobate anteriorly; median lobe distinctly exceeding and broader than laterals, divided into 2 sub­lobes by U­shaped median notch on anterior margin, anterior margin of each sublobe with 2 or 3 spines; lateral lobes broadly subtriangular with lateral margin curved mesially, anterior margin with 3 – 5 spines. Branchial margins slightly convex, with 3 – 5 spines on median part. Basal article of antennular peduncle with 2 subequal­sized spines mesially on anterior surface. Cheliped carpi with 3 (larger cheliped) or 3 – 6 (smaller cheliped) acute small teeth on nearly straight dorsoflexor margin, dorso­extensor margin unarmed entirely; chelae each with row of small spines and sparse short setae on distal 0.5 – 0.7 of thin extensor margin, proximal flexor part with fringe of dense soft setae extending onto cutting edge; fixed finger of smaller cheliped not bifurcate distally. Ambulatory carpi each with small, acute or blunt spine distally; propodi each with 4 slender corneous spines on flexor margin; dactyli each terminating in stout claw, with 3 corneous spines on flexor margin, proximal 2 spines much smaller than distal.

Description. Carapace ( Fig. 1 A, B) weakly or moderately convex dorsally, approximately 1.1 times as long as broad excluding branchial spines, broadest on median branchial margin. Rostrum ( Fig. 1 A, B, D) broad, horizontal, produced well beyond eyes, trilobate anteriorly; median lobe distinctly exceeding and 2.0 – 2.5 times as broad as laterals, shallowly concave on midline, divided into 2 sub­lobes by U­shaped anterior notch bearing minute denticles and short setae, anterior margin of each sublobe with 2 or 3 spines and short setae; lateral lobes broadly subtriangular with lateral margin curved mesially, anterior margin with 3 – 5 spines; dorsal surface with numerous, very short, faint, transverse striae. Orbits ( Fig. 1 H) moderately deep; supra­orbital margin slightly convex, unarmed; outer orbital angle produced into acute, strong spine; inner orbital margin with 2 – 4 small spines. Protogastric ridges weakly demarcated. Gastric region with numerous, short, faint, transverse striae. Hepatic margins each with strong spine. Cervical grooves weakly demarcated anteriorly. Branchial margins slightly convex, without distinct longitudinal ridge; anterior margin minutely denticulate or tuberculate, unarmed or with 1 small spine at anterior corner; median margin with 3 – 5 spines; posterior margin and adjacent region with short oblique rugae. Cardiac regions very weakly striate. Striae on dorsal surface with minute setae on anterior margins.

Pterygostomial flaps ( Fig. 1 B) with longitudinal rugae, shallowly concave on anterior part; anterior margin subtriangular with narrowly rounded apex ( Fig. 1 C); anterior dorsal margin with row of small tubercles and 2 – 4 small spines posteriorly.

Third thoracic sternite ( Fig. 1 E) depressed medially, trilobate anteriorly; median lobe very broad, weakly convex on anterior margin, with row of setae; lateral lobes narrow, distinctly exceeding median lobe, with rounded apex. Fourth thoracic sternite with transverse ridges interrupted medially and bearing sparse setae; anterior margin strongly concave.

Telson ( Fig. 1 F) composed of 7 plates; proximolateral plates much smaller than others; distal plates broad, terminal margins broadly rounded.

Ocular peduncle ( Fig. 1 A, H) large, short, with few transverse striae on proximal part of dorsal surface; dorsal extension onto cornea low, broadly rounded.

Basal article of antennular peduncle ( Fig. 1 G) with transverse ridge of setae on lateromedian ventral surface; lateral margin with row of setae; anterior lateral part slightly concave, with transverse rugae; anterior surface armed with 2 subequal­sized spines mesially, lateral spine slightly larger than mesial.

Antennal peduncle ( Fig. 1 H, I) moderately short; first article immobile, following 3 articles mobile. First article largest, strongly produced forward in lateral view, broadly in contact with anterior margin of carapace, acutely pointed anteriorly, with longitudinal ridge along ventral margin. Second article with small spine at anterior distal corner, posterior distal corner with minute spinule or unarmed. Third article moderately elongate; anterior margin with small protuberances, distal corners apparently unarmed. Fourth article small, unarmed. Dorsal and ventral surfaces of second to fourth articles slightly rugose.

Third maxilliped ( Fig. 1 J) with coxa bearing subtriangular projection on distoflexor margin; ventromesial margin with roundly subtriangular projection slightly directed ventrally, distomedian projection incompletely articulated. Basis articulating with ischium, rounded subtriangular. Ischium broad, ovate, transversely rugose on ventral surface, with longitudinal ridge along extensor margin; anterior extensor corner strongly produced, with narrowly rounded apex. Merus with laminate, broad, rounded, subrectangular lobe on ventroflexor margin; ventral surface moderately rugose. Carpus with subtriangular projection on median part of flexor margin and longitudinal ridges on extensor surface. Propodus slender, somewhat tapering distally, with rugae along extensor margin. Dactylus small, subtriangular. Merus to dactylus with long setae on flexor margin (not illustrated). Exopod with proximal article armed with large or small spine at distomesial margin and 1 or 2 small, blunt or acute spines on anterior margin; distal article laminate, robust, reaching midlength of merus, with distal flagellum, proximal part inflated, distal part slender.

Chelipeds ( Fig. 2 A–G) subcylindrical, moderately unequal in size, not showing distinct sexual dimorphism. Larger cheliped ( Fig. 2 A–D) with ischium crenulate, armed with small spine on mesial margin. Merus short; dorsal surface transversely rugose, submedian transverse ridge indistinct, rounded; dorsoflexor margin crenulate, distally with roundly subrectangular lobe bearing small spine; dorsodistal margin unarmed; ventral surface transversely rugose, distal flexor margin with 3–5 slender spines. Carpus 1.6–1.8 times as long as broad, not broadened distally; dorsal surface with numerous, delicate, transverse rugae; dorso­extensor margin rounded, unarmed entirely; dorsoflexor margin nearly straight, slightly crenulate, with 3 acute small teeth; dorsodistal margin with rounded subtriangular lobe on flexor part; ventral surface with delicate transverse rugae, flexor margin slightly crenulate, with small spine on distal half. Chela moderately narrow, elongate, 2.2–2.5 times as long as carpus, 3.1–3.8 times as long as high, lying on extensor side, with dactylus opening at oblique angle; extensor margin thin, weakly concave at base of fixed finger, with row of small spines on distal 0.5–0.7 and sparse short setae; fingers crossed distally. Palm inflated dorsoventrally, covered with delicate, short, oblique rugae, no distinct median longitudinal ridge; dorsoflexor margin with longitudinal rugose ridge; ventral surface obliquely rugose. Fixed finger with slightly curved distal claw; dorsal surface with scattered very short rugae and small pits; dorsodistal flexor margin with broad subtriangular projection extending onto dactylus; cutting edge with broad, low tooth medially and row of small rounded teeth proximally and distally; ventral surface with short oblique rugae, proximal flexor part with fringe of dense soft setae extending onto cutting edge. Dactylus approximately 0.4 of chela length, with moderately curved distal claw; dorsal surface with very short rugae and small pits, shallow sulcus present along flexor margin, flexor surface rugose; cutting edge with broad tooth proximally and row of small, rounded teeth on distal 0.7; ventral surface with few small pits, proximal part adjacent to cutting edge with fringe of soft setae. Transverse and oblique rugae on articles with short thin setae on anterior margins.

Smaller cheliped ( Fig. 2 E–G) generally similar to larger; carpus with dorsoflexor margin armed with 3 – 6 acute teeth and some smaller teeth; chela narrower than that of larger; fixed finger not bifurcate distally; dactylus opening at strong oblique angle, approximately 0.5 of chela length; cutting edges lacking large teeth.

Ambulatory legs ( Fig. 3 A–E) relatively short, with sparse short setae on meri and carpi and scattered tufts of short and long setae on propodi and dactyli. Meri elongate, decreasing in length posteriorly; extensor margin unarmed but slightly crenulate; lateral surface with transverse rugae, distoflexor margin with subtriangular (first leg) or rounded (second and third legs) lobe, lobe of second leg more strongly produced than that of third; mesial surface without decalcified part, distoflexor margin unarmed. Carpi with longitudinal and oblique rugae on lateral surface; extensor margin slightly crenulate, with small, acute or blunt spine distally. Propodi 1.8 –2.0 times as long as dactyli, 3.6–4.2 times as long as high; lateral surface with short, oblique rugae; extensor margin slightly crenulate but unarmed; flexor margin with 4 slender corneous spines, distal pair subequal in size. Dactyli each terminating in moderately or strongly curved, stout claw; flexor margin with 3 corneous spines, proximal 2 spines much smaller than distal, proximal­most spine very small, distal spine with enlarged, produced base, somewhat smaller than terminal claw.

Fifth pereopods slender, chelate; propodus with approximately 10 hooked setae and numerous short simple setae.

Male with pair of developed pleopods modified as gonopods on second abdominal segment ( Fig. 2 H, I); protopod naked; endopod spoon­shaped, elongate oval, with numerous marginal setae except for proximal part; exopod small, ovate, naked; pleopods on third to fifth abdominal segments reduced to inconspicuous, low rudiments each with small pore. Female with paired pleopods on third to fifth abdominal segments; third pair smaller than others, fourth and fifth pairs well developed.

Coloration in life. See Fig. 4 A–C. Carapace, abdomen, and chelipeds with irregular, brownish red marks on white ground color. Carapace also with dark red marks on hepatic regions. Palm and fixed fingers of chelipeds with yellow tinge; dactyli bluish purple on flexor surface. Ambulatory legs pale red or brownish red; propodi pale or dark bluish purple; dactyli and distal parts of propodi yellow.

Habitat. See Fig. 4 C. The new species was found on an unidentified species of unbranched sea whip (Octocorallia, Alcyonacea , Ellisellidae ). In addition to the two specimens described here, several small individuals were on the same host (not collected).

Etymology. The specific name is a combination of the Latin, flagellum (whip) and colo (to inhabit), in reference to the habitat of the new species on the sea whip.

Remarks. Lissoporcellana flagellicola , new species, appears close to L. quadrilobata in having the median lobe of the rostrum with a distinct median notch on the anterior margin, lateral lobes of the rostrum with small spines on the mesial margin, branchial margins each armed with at least three spines, and carpi of the chelipeds being unarmed on the dorso­extensor margin. However, the new species is distinguished from L. quadrilobata in having a less elongated carapace (in L. flagellicola , 1.1 times as long as broad, whereas 1.2 times in L. quadrilobata , Fig. 3 F), lateral lobes of the rostrum being broadly subtriangular (in L. quadrilobata , narrowly subtriangular, Fig. 3 F), and dactyli of the ambulatory legs each with a stout terminal claw (in L. quadrilobata , a slender terminal claw, Fig. 3 G). The coloration in life is also different in the two species. The carapace of L.

flagellicola has irregular, brownish red marks on the white ground color, whereas that of L. quadrilobata is known to possess narrow, longitudinal and oblique, red lines, or to be entirely milky white without marks (see Kato & Okuno 2001: 92, unnumbered fig.; Kawamoto & Okuno 2003: 99, unnumbered fig.).

The strong denticulation on the anterior margin of the rostrum and unarmed dorsoextensor margin of the carpi of chelipeds are also shared by L. pectinata Haig, 1981 , but the armature of the antennular peduncle and ambulatory legs immediately differentiates L.

flagellicola from L. pectinata . The basal article of the antennular peduncle has two mesial spines on the anterior surface in L. flagellicola , whereas it is said to be armed with three spines but illustrated to possess four spines in L. pectinata (see Haig 1981: fig. 3 B). The propodi of the ambulatory legs are armed with four corneous spines including the distal paired spines on the flexor margin in L. flagellicola , but they usually have a row of eight or nine spines in L. pectinata . The ambulatory dactyli possess three corneous spines on the flexor margin in L. flagellicola , while they are armed with six spines in L. pectinata .

Two other species of Lissoporcellana , L. quadrilobata and L. spinuligera (Dana, 1853) , are hitherto known from the Ryukyu Islands ( Nakasone & Miyake 1968, Kawamoto & Okuno 2003). Lissoporcellana nakasonei ( Miyake, 1978) has also been recently collected from the Ryukyu Islands (Imazuni, Kume­jima Island, Ryukyu Islands, 21 m, associated with Dendronephthya sp., 15 November 2002, coll. T. Kawamoto, 1 female CL 2.1 mm, CMNH­ZC 1168). These three species are known to be associated with invertebrates different from the host of L. flagellicola . Lissoporcellana quadrilobata and L. nakasonei are recorded to live on the alcyonacean octocorals such as Chironephthya , Dendronephthya , or Solenocaulon (Ng & Goh 1996, Osawa 1998, Kato & Okuno 2001), whereas L. spinuligera inhabits sponges such as Sigmadocia ( Morton, 1988) or scleractinian corals and alcyonacean octocorals such as Pavona , Pocillopora , and Solenocaulon ( Nakasone et al. 1986, Ng & Goh 1996). Research using SCUBA equipment should result in the discovery of further undescribed or rarely recorded porcellanids in the Ryukyu Islands as well as in other Indo­west Pacific shallow­waters.