Raymunida striata, Osawa, 2012

Osawa, Masayuki, 2012, Raymunida Macpherson & Machordom, 2000 (Crustacea: Decapoda: Anomura: Munididae) from the KUMEJIMA 2009 Expedition in the Ryukyu Islands, Japan *, Zootaxa 3367, pp. 134-144 : 135-140

Raymunida striata n. sp.

( Figs. 1, 2, 4A)

Type material. Holotype: female (cl 8.2 mm), St. Trawl 45, 26° 19.907 –20.056 ʹN, 126° 43.191 -42.622 ʹE, 67.5– 76.0 m, dead coral blocks and rubble, trawl, 16 November 2009 (RUMF-ZC-1415) . Paratype: 1 male (cl 5.9 mm), same data as holotype (RUMF-ZC-1416) .

Description. Carapace ( Fig. 1A) longer than broad, cl 1.1–1.2 times carapace width; dorsal surface nearly horizontal from anterior to posterior, somewhat convex from side to side, with long transverse ridges bearing dense, short plumose setae anteriorly (some relatively long, stiff simple setae also present on posterior half of carapace in paratype, but no such setae in holotype); gastric region with row of 4 pairs of subequal-sized epigastric spines; cervical grooves distinct; one parahepatic spine, 2 branchial anterior spines, and 1 postcervical spine present on each side. Frontal margin slightly oblique, with small spine mesial to anterolateral spine; lateral orbital angle slightly produced but unarmed; infra-orbital margin produced anteriorly, with small denticles on lateral margin. Lateral margins slightly convex, each with 6 spines: 2 spines in front of and 4 spines behind anterior cervical groove; first anterolateral, situated slightly posterior to level of orbit, clearly not reaching level of sinus between rostrum and supraocular spines; second at midlength between anterolateral spine and anterior cervical groove, distinctly smaller than anterolateral spine, accompanying another small spine ventrally; 2 spines each on anterior and posterior branchial regions, decreasing in size posteriorly and bearing relatively long, stiff simple seta at each base, last spine small. Rostrum spiniform, 0.4 cl, slightly arched in lateral view; lateral margins with some short simple setae, minutely crenulate distally. Supraocular spines exceeding half length of rostrum and distal margins of corneas, subparallel, slightly directed upward or nearly horizontal in lateral view.

Pterygostomian flaps unarmed on anterior dorsal margin; lateral surface with short and long, oblique and longitudinal ridges.

Thoracic sternum ( Fig. 1B) approximately 1.2 times as long as broad, broadest on sternite 7, depressed along midline. Sternite 3 ( Fig. 1C) 3.2–3.6 times as broad as long (measured along midline); anterior margin with median notch and narrow projection at each lateral angle; lateral margins convergent posteriorly; posterior margin touching anterior margin of fourth sternite. Sternite 4, 2.8–2.9 times longer (measured along midline) and 2.1 times broader than preceding sternite, with 2 transverse long, feebly granulate striae, anterior stria interrupted medially; anterior margin concave, slightly narrower than sternite 3. Sternites 5 and 6 with pair of short or very short, oblique striae on lateral parts, respectively. Sternite 7 smooth. Transverse ridges of sternites 5–7 obtuse, feebly granulate, each with row of short plumose setae.

Abdominal somites ( Fig. 1D, E) with dense, short plumose setae on anterior margins of transverse ridges and striae; 2 long transverse ridges present on each somite, bearing some short and long, stiff simple setae, anterior and posterior ridges on somites 2–4 and anterior ridge on somite 5 uninterrupted and somewhat elevated, but posterior ridge on somite 5 and both ridges on somite 6 interrupted in median part. Somites 2 and 3 each with uninterrupted transverse stria between 2 long ridges. Somite 4 with uninterrupted or medially interrupted transverse stria between 2 long ridges. Somite 5 with short transverse stria in posterior median part. Somite 6 with flattish posteromedian margin. Telson weakly calcified on posteromedian part, indistinctly subdivided, with short scaly ridges; distal margin with broad median notch.

Eyes ( Fig. 1A, F) moderately large; corneas slightly dilated, maximum diameter approximately 0.3 length of distance between mesial bases of anterolateral spines; eyelash consisting of simple setae; relatively long, stout seta present near distal margin of rounded dorsal anterior extension of peduncle.

Basal article of antennular peduncle ( Fig. 1A, F), excluding distal spines, approximately 0.2 length of carapace excluding rostrum, only reaching proximal margin of cornea, with 2 distal spines, mesial spine distinctly shorter than lateral spine; lateral margin with 2 spines, proximal spine short, located nearly level of distal margin of article, distal spine long, overreaching tip of distolateral spine.

Antennal peduncle ( Fig. 1A, F) moderately short. Article 1 with long distomesial spine clearly overreaching distal margin of article 4 and slightly overreaching distal margin of basal article of antennular peduncle; distolateral angle rounded. Article 2 with 2 distinct distal spines, mesial spine longer than lateral spine, slightly overreaching distal margin of article 3; mesial margin unarmed. Article 3 unarmed or with very small tuberculate spine at dorsal distomesial angle; distal margin minutely denticulate. Article 4 unarmed.

Mxp3 ( Fig. 1G, H) with basis bearing 6 or 7 denticles on mesial ventral margin. Ischium armed with strong spine at distomesial angle; dorsodistal angle acutely produced, terminating in small spine; crista dentata with 28–30 denticles. Merus as long as ischium measured on ventral margin, not narrowed distally; ventral margin with 2 or 3 slender spines, proximal and distal spines subequal in size; dorsal margin with distinct spine at distal end, subdistal part unarmed (paratype) or with small spine (holotype). Carpus with slender spine on ventrodistal margin, dorsodistal angle slightly produced. Propodus and dactylus unarmed, relatively slender. Exopod overreaching distal margin of merus.

Epipods present on Mxp3 and P1–3.

P1 ( Figs. 1I, 2A) relatively slender, combined length from proximal margin of basi-ischium to tip of chela 2.8– 3.0 times cl, with numerous short, scaly ridges except on fingers; ridges anteriorly bearing short plumose setae; sparse long, stiff simple setae also present, numerous on mesial margins of merus and carpus and mesial and lateral margins of chela. Merus 0.9–1.0 length of cl, 1.7–1.8 times longer than carpus, with irregular row of spines along mesial and lateral margins on dorsal surface, mesial spines much larger; mesial face also with rows of proximally diminishing spine on midline and ventral margin; lateral face with few distal spines; lateral and ventral surfaces unarmed; ventrolateral margin terminating in strong spine. Carpus 2.5–2.8 times as longer than broad; dorsal surface with mesial and lateral rows of irregular small spines; mesial surface with irregular row of some spines dorsally along midline, distal spine strongest; ventromesial margin also with row of some spines; lateral surface with some spine dorsally; ventral surface with small spines on proximal mesial part. Chela slender, 6.3–6.6 times length of breadth measured on base of fingers. Palm slightly inflated, 0.9–1.0 length of carpus, 2.3–2.6 times longer than broad, with spine at base of dactylus and mesial and lateral rows of small spines on dorsal surface; dorsolateral margin with row of spines continuing along entire length of fixed finger; ventrolateral margin with row of small spines; mesial surface with irregular row of spines on midline; ventral surface with 2 small spines on proximal mesial part and single spine at base of dactylus. Fingers 1.5–1.7 times as long as palm, slightly arched ventrally, distally curving and crossing when closed, each ending in small corneous claw; dorsal and ventral surfaces rounded; opposable margins slightly gaping, each with row of numerous irregular-sized, small, blunt and subacute teeth. Dactylus with 3 spines on proximal 0.3 of slightly crenulate dorsomesial margin.

P2–4 ( Fig. 2B–H) somewhat compressed, with sparse long, stiff simple setae on margins; P2 and P3 subequal; combined length from proximal margin of basi-ischium to tip of dactylus 1.9–2.2 times cl, 1.1–1.2 times longer than that of P4. Ischia each with small spine near ventral angle of distolateral margin on P2 and 3, but unarmed in P4; mesial surface with small spine near dorsal angle of distal margin on P3 and 4, but unarmed on P2. Meri elongate subrectangular, successively shorter posteriorly (P3 merus 0.9 length of P2 merus, P4 merus 0.7 length of P3 merus); P2 relatively slender; P3 broadest at midlength; length-breadth ratio, 5.3–5.8 on P2, 4.2 on P3, 3.3–3.4 on P4; merus-propodus length ratio, 1.4 on P2, 1.2 on P3, 1.0 on P4; P2 merus 0.8–0.9 as long as cl; dorsal margin bearing rows of moderately long, plumose setae, 13 or 14 irregularly arranged spines present on entire margin of P2, 5 spines on distal 0.7 margin of P3, only single subdistal spine on P4; lateral surface with transverse scaly ridges bearing numerous, short plumose setae (sparse long, stiff simple setae also present on P3 and P4), row of spines present near dorsal margin on P3 (9 or 10 spines) and P4 (5 or 6 spines) but absent on P2; ventrolateral margin somewhat crenulated, distally with 3 spines on P2, 2 or 3 spines on P3 (if present, including submarginal spines), and 1 spine on P4; ventromesial margin with 1 subdistal spine on P2 but unarmed on P3 and 4. Merocarpal articulation of P4 reaching lateral end of anterior cervical groove of carapace. Carpi subequal on P2 and P4, longer on P3, 0.5–0.6 length of propodi on P2–4; dorsal margin with 4 or 5, 4, 2–4 spines on P2–4, respectively; dorsodistal angle rounded; ventrodistal margin produced, with small spine; lateral surface unarmed but with somewhat elevated longitudinal crest dorsally along midline and few oblique, ridges on ventral half. Propodi not tapering distally, longest on P3, shortest on P4; length-breadth ratio, 6.9–8.3 on P2, 7.0–7.5 on P3, 6.0–6.4 on P4; dorsal margin unarmed; lateral surface with irregular row of short ridges and some long, stiff simple setae along midline; ventral margin with 8 or 9, 6 or 7, and 5–7 slender, corneous spines including distal pair on P2–4, distolateral spine larger than distomesial spine ( Fig. 2D). Dactyli nearly straight, 0.5–0.6 length of propodi on P2– 4, with slightly curved distal claw; ventral margin with 6 or 7 (P2), 6 (P3), and 5–7 (P4) slender, proximally diminishing, corneous spines, each spine arising from low process.

P5 chela elongate, with numerous moderately long, simple setae on dorsal and ventral faces and with numerous curved, serrate setae on ventrolateral face of palm; setation similar in male and female.

Male with 2 pairs of pleopods modified as gonopods on abdominal somites 1 and 2, second pair more developed than first; pleopods on somites 3–5 flattened, spatulate, each with row of short plumose setae on lateral margin. Female with 4 pairs of elongate pleopods on abdominal somites 2–5, those on somites 3–5 well developed.

Colouration in life ( Fig. 4A). Carapace, abdomen, and P1–4 generally reddish. Carapace with small scattered, dark red marks and numerous small white marks; gastric region with narrow white bands on anterior margins of transverse ridges. Pterygostomian flap dark red, with narrow white area along dorsal margin. Abdomen with some small, dark red marks; somites 2–4 each with row of small white spots on anterior transverse ridge. P1 pale coloured on median dorsal parts of meri and carpi; palm with 1–3 white spots on proximal and distal parts of dorsal surface; fingers each with subdistal dark red ring, tips white, dorsal and ventral surfaces with some irregular, narrow white stripes. P2–4 with small white spots on dorsodistal part on merus and carpus of each P2 and P3; propodi with irregular narrow, longitudinal white marks.

Etymology. The specific name is derived from the Latin, striatus (striped), referring the characteristic narrow stripes on the P1 fingers in the new species.

Distribution. Only known from the type locality, Kume Island, Ryukyu Islands.

Habitat. The type specimens were collected from the depth of 67.5–76.0 m, with substratum of dead coral blocks and rubble.

Remarks. Macpherson & Machordom (2001) divided seven Raymunida species into two groups based on the length of the mesial spine of the antennal article 1, and mentioned that the importance of the character was supported by mitochondrial cytochrome c oxidase subunit I (COI) sequence data. The validity of the two groups of species is also generally supported by phylogenetic analyses on the species of Munida Leach, 1820 , and its related genera inferred from COI and 16S rRNA sequence data ( Machordom & Macpherson 2004). The first group of species ( R. bellior , R. confundens , R. dextralis , and R. insulata ) is characterized by the mesial spine of the antennal article 1 reaching or overreaching the distal margin of the antennular basal article; whereas the spine in the second group of species ( R. cagnetei , R. elegantissima , and R. erythrina ) never reaches the distal margin of the antennular basal article. Four additional species have been described since Macpherson & Machordom’s (2001) publication. Following their grouping of species, R. formosanus can be assigned to the first group, and R. limbata and R. vittata to the second group. Lin et al. (2004) also showed that R. formosanus is closely related to the R. confundens – R. dextralis clade in their phylogenetic tree based on the COI data. However, re-examination of the holotype of R. formosanus (male, cl 15.4 mm, deposited in the National Taiwan Ocean University) revealed that, unlike the original description of the species, the mesial spine of the antennal article 1 slightly falls short of the distal margin of the antennular basal article. In addition, since the length of the spine varies intraspecifically in R. lineata , this species cannot be definitely referred to the two groups of species by Macpherson & Machordom (2001) (see Osawa 2005). Baba (2005) also reported similar variation of the spine in R. bellior .

Considering these intraspecific variations, the armature of the antennal article 2 is presumed as another morphological character that distinguishes the two phylogenetic groups of species by Macpherson & Machordom (2001) and Lin et al. (2004). The antennal article 2 is unarmed on the mesial margin in the first group, but it usually has a distinct subdistal spine on the margin in the second group (the spine is reduced to a small low protuberance in small specimens of R. vittata , see Remarks on the species below). All three recently described three species, R. limbata , R. lineata , and R. vittata , are included in the second group, whereas R. striata n. sp. is referred to the first group based on the character of the antennal article 2.

Among the first group of species presently defined, R. striata n. sp. may be closest to R. confundens and R. dextralis . The morphological characters shared by the three species are: the presence of a small spine on the frontal margin mesial to the anterolateral spine of the carapace, the possession of numerous long simple setae on the P1, the slender chela being more than six times longer than broad, the absence of a distinct longitudinal crest on the dorsal midline of each P1 finger, and the presence of a row of relatively sparse spines on the dorsolateral margin of the P1 fixed finger. However, R. striata n. sp. is distinguished from other species of the same first group including R. confundens and R. dextralis by the abdominal somites 2 and 3 each with an uninterrupted stria between two distinct transverse ridges on the dorsal surface, the Mxp3 merus with a prominent distal spine on the extensor margin, and the mero-carpal articulation of the P4 reaching only to the lateral end of the anterior cervical groove of the carapace. In the other five species of the first group, the abdominal somites 2 and 3 have no striae on the dorsal surface, the Mxp3 merus is unarmed or possesses only a small distal tooth on the extensor margin, and the merocarpal articulation of the P4 overreaches the frontal margin of the carapace. Raymunida striata n. sp. further differs from R. confundens and R. dextralis in the presence of distinct scaly transverse ridges on the lateral surfaces of the P2–4 meri. Such distinct scaly ridges apparently absent in R. confundens and R. dextralis (see Macpherson & Machordom 2001; Lin et al. 2004). Raymunida bellior and R. insulata are separated from R. striata n. sp. by the absence of a small spine on the frontal margin mesial to the anterolateral spine of the carapace. Raymunida bellior is also distinctive in having long plumose instead of simple setae on the Pl. The stoutness of the chela and structure of the fingers of the P1 are clearly different between R. formosanus and R. striata n. sp. The chela is much more robust in R. formosanus (less than five times longer than broad) than in R. striata n. sp. (more than six times longer). The P1 fingers have a distinct longitudinal crest on each dorsal midline in R. formosanus , but such a crest is absent in R. striata n. sp.

The colour patterns in life are also different among R. confundens , R. dextralis , R. formosanus , and R. striata n. sp. The colour photograph of R. dextralis was given by Macpherson (1994: fig. 66) as that of Munida bellior before the original description of the former species. In R. confundens and R. dextralis , there is a transverse white part on the base of the rostrum and supraocular spines of the carapace, but such a distinct mark is absent in R. striata n. sp. The Pl fingers have a distinct submedian white band in R. dextralis and R. formosanus , but they bear some irregular, narrow white stripes in the new species. The P2–4 of R. confundens , R. dextralis , and R. formosanus have white transverse bands, whereas those of R. striata n. sp. lack such band pattern and possess irregular narrow, longitudinal white marks on the propodi ( Macpherson & Machordom 2001; Lin et al. 2004; present study). Miyake & Baba (1967) described the colouration of R. bellior based on the material preserved in formalin. The species has a broad V-shaped, reddish brown band on the posterior half of the carapace and reddish brown bands on the P2–4. The colour pattern is very different from that of R. striata n. sp. The colouration of R. insulata is unknown ( Macpherson & Machordom 2001).