Richardina parvioculata, Saito, Tomomi & Komatsu, Hironori, 2009

Saito, Tomomi & Komatsu, Hironori, 2009, Two new species of Richardina A. Milne-Edwards, 1881 (Crustacea: Decapoda: Stenopodidea: Stenopodidae), representing the first occurrences of the genus from the Pacific, Zootaxa 2154, pp. 30-46 : 39-43

Richardina parvioculata n. sp.

[new Japanese name: komanako-ryu-jin-ebi] ( Figs. 7–9 )

Type material. HOLOTYPE: NSMT-Cr 20839, ovigerous female (cl 5.4 mm), off Tosa Bay, western Japan, 32° 56.45N, 133° 30.52E (KH02-3, leg. 1, St. TA-2), 3 m ORE B.T., 517 m, 11 Sep. 2002, coll. M. Mitsuhashi. ALLOTYPE: NSMT-Cr 20840, male (cl 5.1 mm), same data as holotype.

Description of holotype female. Body slender and compressed. Integument of carapace and pleon glabrous. Rostrum ( Figure 7 A, B) slender, directed forward, tip slightly upward, reaching proximal third of antennal scale, 0.30 of cl, narrowly triangular in dorsal view; dorsal margin armed with 8 teeth, all anterior to postorbital margin; ventral margin with 1 tooth subdistally; lateral margin unarmed.

Carapace ( Figure 7 A, B) with postrostral median ridge extending to gastric region; 1 (left) or 2 (right) postrostral submedian spines relatively small, straight, directed forward; postorbital region armed with 2 stout spines directed anteriorly; orbital margin concave, inferior orbital angle rounded; antennal spine small and acuminate, marginal; anterolateral margin rounded with several minute spines; cervical groove distinct, posterior margin armed with cincture of several spines, directed anteriorly, increasing in size gradually in lateral surface, but unarmed on posterodorsal part.

Sixth thoracic sternite ( Figure 7 C) with paired narrow lobes, each lateral margin unarmed, ventral surface concave. Seventh sternite with paired, broad semicircular lobes, each distolateral angle rounded, ventral surface concave, unarmed. Eighth sternite with paired triangular plates, each distolateral angle rounded, ventral surface concave, unarmed.

Pleonal somites not sculptured; ventral margins unarmed. First pleonal somite short, divided in two sections by distinct transverse carina; anterior section with pleuron unarmed laterally, posterior section with pleuron unarmed laterally, posteroventral margin unarmed. Second somite with anterior transverse carina ending at base of pleuron. Third somite longest, posterodorsal margin somewhat posteriorly produced; pleuron unarmed laterally. Sixth somite ( Figure 7 D) armed with 1 strong lateral spine on either side. Telson ( Figure 7 D) lanceolate, proximally narrowed between widest part and basal joint, tapering distally, 2.3 times longer than broad; dorsal surface with median groove flanked by two dorsolateral carinae each provided with row of 3 or 4, rather symmetrically situated dull, rudimentary spines, inner margin with 3 or 4 dull, rudimentary small spines; lateral margins convex subproximally, armed with small spine proximally and strong spine at midlength; posterior margin convex, armed with small posterior spine, posterolateral angle armed with small posterolateral spine.

Eye ( Figure 7 A, B) well developed, cornea hemispherical, red pigmented; eyestalk armed with 4 small spines along base of cornea, laterally with several small spines, 2.8 times as long as cornea. Antennular peduncle ( Figure 7 A, B) reaching midlength of antennal scale; first segment subequal to distal two segments combined, with longitudinal, distolateral row of setae; stylocerite acute, curved; second segment armed with 1 strong dorsolateral spine; third segment with rounded distal margin; flagella slender. Antenna ( Figure 7 A, B) with stout basicerite armed with moderately large spine at distolateral angle, and with a few additional spines on ventrolateral margin; antennal scale 3.3 times longer than broad, lateral margin nearly straight, armed with 4 teeth, dorsal surface with 2 distinct longitudinal carinae; carpocerite short, reaching level of first segment of antennular peduncle, armed with 1 spine on distolateral angle.

Mouth parts similar to those of R. ohtsukai n. sp. Third maxilliped ( Figure 7 E) with endopod slender, composed of 7 segments, reaching tip of antennal scale by lengths of dactylus and half of propodus; dactylus tapering distally, lateral margins of dactylus and propodus furnished with long setae, distomesial surface with shallow depression fringed with dense grooming setae carpus unarmed; merus with distolateral and lateral rows of 2 stout spines; ischium compressed, armed with 1 dorsolateral spine and ventral row of several small spines, interspaced with pectines; basis short; coxa with short epipod; exopod with well-developed, unsegmented flagellum, distally with dense setae.

Branchial formula shown in Table 2.

First and second pereopods similar to those of R. ohtsukai n. sp. Third pereopod missing. Fourth and fifth pereopods ( Figure 7 F, G) similar, very long and slender; fourth pereopod reaching tip of antennal scale by lengths of dactylus, propodus and carpus; dactyli ( Figure 7 G) compressed laterally, about 6 times longer than wide, uniunguiculate; propodi about twice as long as dactyli, subdivided into 4 articles, ventral margin armed with several small movable spines; carpi 1.5 times as long as propodi, subdivided into 5–6 articles, ventral surfaces armed with small spine on ventrodistal angle of each article, meri 0.8 of carpal length; ischia entire, 0.6 of meral length.

Pleopods without any appendices. First pleopods uniramous, shortest. Second to fifth pleopods biramous, with basipodite shorter than exopodite, but as long as endopodite, mesial margin unarmed. Third to fifth pleopods generally similar, decreasing in size posteriorly, unarmed.

Uropod ( Figure 7 D) with protopodite stout, lateral margin terminating in acute process; exopod broad, falling slightly short of posterior margin of endopod, lateral margin nearly straight, terminating in acute tooth, with row of 8 (left) or 7 (right) acute teeth, dorsal surface with 2 smooth longitudinal carinae, unarmed; endopod tapering distally, slightly overreaching posterior margin of telson, lateral margin unarmed, dorsal surface with 2 smooth longitudinal carinae, unarmed.

Eggs very few, diameter 2.0 mm (example: ovigerous female, cl 5.4 mm, NSMT-Cr 20839).

Male allotype characteristics. Rostrum as long as that of female, 0.31 of cl; dorsal margin with 6 teeth, proximal 2 teeth posterior to orbital margin; ventral and lateral margins unarmed. Sixth thoracic sternite ( Figure 8 A) with slender, bifurcate lobes, lateral angle terminating in acute spine, mesial angle denticulate; seventh sternite with relatively broad triangular lobes directed anterolaterally, each anterolateral angle produced; eighth sternite with triangular lobes directed anterolaterally, each anterolateral angle terminating in acute spine. Pleura of first to sixth pleonal somites armed with some teeth anteroventrally and/or posteroventrally. Eye ( Figure 8 B) well developed, cornea hemispherical, red pigmented, 0.3 times as long as stalk; eyestalk armed with 4 strong spines along base of cornea, mesial and lateral margins with several strong spines. Third pereopod ( Figure 8 C, D, E) with palm 2.9 times as long as wide, dorsomesial surface armed with a few rows of several spines of various sizes or tubercles, ventrolateral surface armed with a few rows of several small spines; carpus slightly widened distally, about 5.5 times longer than wide, 0.8 of chela length, dorsal surface armed with two rows of 2–6 spines, ventral margin armed with row of 7 smaller spines; merus 0.9 of carpal length, dorsal margin armed with row of 2 spines proximally, lateral surface with a few tiny spines, ventral margin armed with row of 9 spines; ischium 0.7 of meral length, unarmed. Second to fifth pleopods armed with some teeth on ventral margins of basipodites.

Color in life ( Figure 9 ). Just as in the figure provided by Lo Bianco (1903), the color pattern of this species is quite similar to R. fredericii . Body and appendages generally pinkish transparent. Rostrum transparent. Carapace pinkish transparent with red mark on anterolateral region, and red spot on postorbital region. First to sixth pleonal somites each with red transverse band posteriorly. Eye cornea red, stalk pinkish transparent. Second maxilliped almost red. Third maxilliped with carpus, merus and ischium red. Telson and uropods generally transparent, but lateral margins and carinae red.

Etymology. The specific name is derived from the Latin, parvus (=small) and oculus (=eyed), in reference to the relatively small eye of this new species.

Distribution. So far known only from off Tosa Bay, western Japan.

Ecological notes. The present specimens were collected from the gastric cavity of hexactinellid sponges.

Remarks. Although the female specimen lacks the third pereopods, the assignment of the new species to Richardina is justified by the presence of uniunguiculate dactyli on the fourth and fifth pereopods and the lack of any spines on pleonal somites. The new species is described only from a single damaged female and a single male specimen. Assessment of diagnostic characteristics of this species will be made more precisely when more specimens become available. Richardina parvioculata n. sp. appears unique within the genus in lacking the median row of spines on the posterior margin of the cervical groove, having the large eyestalk and contrasting small-sized cornea, as well as the blunt spines on the dorsolateral carinae of the telson. The new species is most similar to the Mediterranean species R. fredericii , in the general armature of the carapace and pleonal somites, the number of cinctures of spines on the posterior margin of the cervical groove, and the number of articles of the propodi and carpi of the fourth and fifth pereopods. But the new species is easily distinguished from R. fredericii by the following characteristics: (1) the lateral teeth on the rostrum are absent in R. parvioculata , whereas there are 1–3 in R. fredericii ; (2) the length ratio of cornea and eyestalk is 1: 2.8 in R. parvioculata , against 1: 1.9 in R. fredericii ; (3) the length ratio of dactyli, propodi, carpi, meri, ischia of fourth and fifth pereopods is 1: 2: 3: 2.3: 1.5 in R. parvioculata , against the relatively longer 1: 4: 6.6: 5.2: 2.5 in R. fredericii (cf. Lo Bianco 1903; MacPherson 1978).

Figures

FIGURE 7. Richardina parvioculata n. sp., holotype female, (cl 5.4 mm), NSMT- Cr 20839. A, anterior part of carapace and eyes, lateral; B, anterior part of carapace and eyes, dorsal; C, sixth to eighth thoracic sternites, ventral; D, telson and uropod, dorsal; E, left third maxilliped, ventral; F, left fourth pereopod, lateral; G, same, dactylus, lateral. D, E, marginal setae omitted.

FIGURE 8. Richardina parvioculata n. sp., allotype male, (cl 5.1 mm), NSMT- Cr 20840. A, sixth to eighth thoracic sternites, ventral; B, left eye, dorsal; C, left third pereopod, dorsal; D, same, lateral; E, same, mesial.

FIGURE 9. Fresh specimen. Richardina parvioculata n. sp., allotype male (cl 5.1 mm), NSMT-Cr 20840. A, entire specimen, lateral view; B, same, ventral view.