Processa filipes, Komai, Tomoyuki & Fujita, Yoshihisa, 2014

Komai, Tomoyuki & Fujita, Yoshihisa, 2014, New records of the caridean shrimp genus Processa Leach, 1815 (Crustacea: Decapoda: Processidae) from Japan, with descriptions of two new species, Zootaxa 3794 (2), pp. 263-278 : 268-273

Processa filipes n. sp.

[New Japanese name: Itoashi-rousoku-ebi] ( Figs. 3A , 4–6 )

Material examined. Holotype: Ohura Bay, Nago, Okinawa Island, 40–60 m, 25 June 2009, trap, coll. T. Naruse et al., 1 ovigerous female (cl 4.4 mm), RUMF-ZC-2652.

Description of female holotype. Body ( Fig. 3A ) moderately slender for genus.

Rostrum ( Fig. 4 A–C) slender, but distinctly widened at base, nearly straight, slightly falling short of distal corneal margins; apex bifid, ventral tooth distinctly longer than dorsal tooth, bifurcation partially obscured by tuft of some short setae; ventral margin faintly concave. Carapace ( Fig. 4 A, B) with suborbital angle obtuse, broadly rounded; antennal tooth conspicuous; no conspicuous concavity present just superior to antennal tooth; pterygostomial angle rounded.

Thoracic sternite 7 with relatively low transverse crest divided into 2 parts by distinct median notch. Sternite 8 ( Fig. 4 D) with peculiar transverse ridge consisting of soft cuticle, bearing row of short setae along anterior margin; no median notch present on anterior margin.

Pleon ( Fig. 3A ) smooth, almost glabrous, ventral margins of pleura lined with fine setae. Fifth pleuron ( Fig. 4 E) without posteroventral tooth. Sixth pleomere ( Fig. 4 E, F) about 1.2 times as long as fifth pleomere, with acute posteroventral tooth; posterolateral process subtruncate distally, unarmed. Sternites 1–5 unarmed.

Telson ( Fig. 4 E, G) damaged, posterior part posterior to second pair of dorsolateral spines missing; 2 pairs of dorsolateral spines present, anterior spines distinctly longer than posterior spines; dorsal surface with transverse row of short setae anterior to anterior pair of dorsolateral spine and longitudinal row of short setae in line with dorsolateral spines.

Eye ( Fig. 4 A, C) large, slightly depressed dorsoventrally, corneal width subequal to length of eyestalk and cornea combined, about 2.8 of greatest width of antennal scale.

Antennular peduncle ( Fig. 4 A, C) extending by two distal segments and 0.3 of proximal segment beyond rostrum, slightly overreaching distal margin of antennal scale, proximal segment longer than distal two segments combined; ultimate segment about half length of penultimate segment; penultimate segment about 4.7 times as long as basal width; proximal segment with ventral tooth located slightly distal to midlength. Stylocerite ( Fig. 4 H) narrowing to distally produced, rounded apex, distolateral or distomesial angles not delimited. Outer antennular flagellum with thickened proximal portion consisting of 11 or 12 articles (distal 6 articles bearing aesthetascs) and thin distal portion of 4 articles. Preserved part of inner flagellum at least 2.5 times as long as carapace.

Antennal scale ( Fig. 4 C) 7.0 times as long as wide; distolateral tooth reaching roundly truncate distal margin of blade. Basicerite ( Fig. 4 A) with distinct ventrolateral distal tooth. Carpocerite ( Fig. 4 A) reaching midlength of antennal scale.

Mouthparts typical of genus, as figured ( Fig. 5 A–E; maxilla damaged during dissection, thus not figured.). Mandible apparently without row of minute spinules on posterior margin.

Third maxilliped ( Fig. 6 A) relatively slender, overreaching antennal scale by length of ultimate segment and 0.3 of penultimate segment. Ultimate segment subequal in length to penultimate segment (= carpus), tapering to sharp, slightly upturned, spine-like apex distally; mesial surface with grooming apparatus consisting of several transverse or obliquely transverse tracts of stiff setae and some movable spines or spinules adjacent to dorsal margin. Antepenultimate segment distinctly longer than distal two segments combined; proximal 0.3 of dorsal margin shallowly excavated. Exopod reaching proximal 0.3 of antepenultimate segment.

Left first pereopod ( Fig. 6 B, C) non-chelate, slightly longer and slenderer than right, reaching slightly beyond distal margin of antennal scale by dactylus; dactylus hook-like, about 0.2 times as long as propodus; propodus tapering distally, about 5.0 times as long as greatest width, with row of prominent setae on flexor margin; carpus shorter than propodus; merus distinctly longer than propodus and carpus combined, with row of sparse short setae on ventral margin. Right first pereopod ( Fig. 6 D, E) chelate, relatively slender, reaching distal margin of antennal scale by tip of chela; chela about 4.3 times as long as wide; fingers about 0.7 length of palm; carpus subequal in length to palm; merus slightly tapering distally and proximally, distinctly longer than chela and carpus combined.

Second pereopods ( Fig. 6 F, G) symmetrical, subequal in length, reaching base of antennal carpocerite by merocarpal articulation; ischium subequal in length to merus, not divided, with distinct proximal lobe on ventral margin; merus faintly divided into 3 articles; carpus divided into 11 or 12 articles; fingers slightly longer than palm.

Third pereopod ( Fig. 6 H) elongate, thin, reaching midlength of antennal scale by mero-carpal articulation; dactylus slightly curved, simple, about 0.3 times as long as propodus, with apical setae; propodus subcylindrical, unarmed; carpus about 2.2 times as long as propodus, unarmed; merus about 20 times longer than wide, armed with 5 movable spines on lateral surface; ischium distinctly shorter than merus, with 2 movable spines on lateral surface ventrally; combined lengths of propodus and carpus distinctly longer than that of merus and ischium. Fourth pereopod missing. Fifth pereopod ( Fig. 6 J) thin, longer than third pereopod, nearly reaching midlength of antennal scale by mero-carpal articulation; dactylus slender, straight, simple, about 0.2 times as long as propodus, subequal in length to that of third pereopod, with apical setae; propodus with tufts of setae terminally, but unarmed; carpus about 1.7 times as long as propodus, unarmed; merus about 30 times as long as distal width, unarmed; ischium distinctly shorter than merus, unarmed; combined lengths of propodus and carpus much greater than that of merus and ischium; coxa with peculiar, marginally multidenticulate, membranous lobe at mesial side.

Uropods damaged.

Coloration in life. Body and appendages generally translucent. Carapace and abdomen with scattered red spots. Cornea light gray. Antennal peduncle with red tint on basicerite. Third maxilliped with distal two segments reddish; antepenultimate segment with red ring distally. Right first pereopod with red spot on palm at base of dactylus. Eggs whitish. See Fig. 3A .

Distribution. Presently known only from Okinawa Island, Ryukyu Islands, Japan, 40- 60 m.

Remarks. The present new species is referred to the P. aequimana species group on account of the unarmed fifth pleuron and subequal second pereopods ( Hayashi 1975). The species group includes the following 11 species ( Hayashi 1975; Noël 1986): P. aequimana , P. d e m a ni Hayashi, 1975, P. d i m o r p ha, P. hemphilli Manning & Chace, 1971 , P. indica Noël, 1986 , P. longirostris , P. moana Yaldwyn, 1971 , P. modica Williamson, 1979 , P. neglecta Hayashi 1975 , P. p ar v a Holthuis, 1951, and P. vicina Manning & Chace, 1971 . Processa filipes n. sp., however, appears unique in having a somewhat thickened, membranous transverse ridge on thoracic sternite 8 and the greatly elongate, thin fifth pereopod; in addition, the other pereopods seem to be also slenderer compared with the other species in the group. The presence of an antennal tooth on the carapace, the unarmed posterolateral process on the sixth pleomere and the unarmed, roundly subtriangular antennular stylocerite distinguish P. filipes n. sp. from all but P. moana of the P. aequimana species group (these characters are not known for P. moana ). Processa moana is indeed similar to P. filipes n. sp. in having unarmed propodus of the fifth pereopod ( Yaldwyn 1971; Hayashi 1975), but further differs from the new species in the longer rostrum slightly overreaching the distal corneal margins.

The holotype has a peculiar multidenticulate lobe, consisting of membranous cuticle, on the mesial side of the coxa of the fifth pereopod ( Fig. 6 M). A similar structure is seen also in P. affinis , as mentioned above. Function of this structure remains unknown.

Etymology. From the combination of the Latin filum (thread) and pes (leg), in reference to the very thin, thread-like fifth pereopod of the new species.

Figures

FIGURE 4. Processa filipes n. sp., holotype, ovigerous female (cl 4.4 mm), RUMF-ZC- 2652. A, carapace and cephalic appendages, lateral view; B, rostrum and anterior part of carapace, lateral view; C, anterior part of carapace and cephalic appendages, dorsal view (marginal setae on antennal scales omitted); D, transverse ridges on thoracic sternites 7 and 8, ventral view; E, fifth and sixth pleomeres and telson, lateral view; F, posterior margin of sixth pleomere, lateral view; G, telson, dorsal view (damaged, posterior half missing); H, stylocerite of left antennular peduncle, dorsal view (setae omitted); I, distal part of left antennal scale, dorsal view (setae omitted). Scale bars: 1 mm for A – C, E; 0.5 mm for D, F – I.

FIGURE 5. Processa filipes n. sp., holotype, ovigerous female (cl 4.4 mm), RUMF-ZC- 2652, left mouthparts. A, mandible, inner view; B, maxillule, outer view; C, first maxilliped, outer view; D, same, inner view (setae omitted); E, second maxilliped, outer view. Scale bars: 0.5 mm.

FIGURE 6. Processa filipes sp. n., female (cl 4.4 mm), RUMF-ZC- 2652. A, left third maxilliped, lateral view; B, left first pereopod, lateral view; C, same, dactylus and propodus, mesial view; D, right first pereopod, lateral view; E, same, chela, extensor view; F, left second pereopod, lateral view; G, right second pereopod, lateral view; H, left third pereopod, lateral view; I, same, dactylus, lateral view; J, left fifth pereopod, lateral view; K, same, dactylus and propodus, lateral view; L, same, dactylus, lateral view (perpendicular); M, coxa of left fifth pereopod, ventral view. Scale bars: 1 mm for A, B, D, F – H, J; 0.5 mm for C, E, I, K – M.

FIGURE 3. A, Processa filipes n. sp., holotype, ovigerous female (cl 4.4 mm), RUMF-ZC- 2652. B, Processa hayashii n. sp., holotype, female (cl 4.8 mm), RUMF-ZC- 2653. Entire animals, lateral view, showing coloration in life.