Typtonomenaeus formosanus Marin & Chan, 2013, sp. nov.

Typtonomenaeus formosanus sp. nov.

(Figs. 1–6)

Material examined: Holotype, non-ovigerous mature female (pcl. 3.2 mm, tl. 10.0 mm) (NTOU M 00948) and allotype male (pcl. 2.5 mm, tl. 9.0 mm) (NTOU M 00948)— Taiwan, Keelung, small bay near Badouzih, 5–6 meters depth, inside brown sponge, coll. I. Marin & R.-Y. Lee, 0 7 July 2010.

Description. Medium-sized pontoniine shrimp with swollen, smooth, subcylindrical body (Fig. 1). Carapace (Figs. 1, 2 f) swollen, smooth, with well marked sharp antennal tooth, without dorsal carina; rostrum (Fig. 2 a, b) well developed, reaching to distal margin of basal antennular segment, slightly curved upward, broad, dorsally armed with 3 teeth, ventrally unarmed, with slightly developed lateral carina (Fig. 2 a).

Abdominal somites smooth, unarmed (Fig. 1); tergites non-carinate, not posteriorly produced, without anteromedian dorsal lobe on the first segment; pleura of somites I – III posteroventrally rounded; two last somites small, with feebly developed pleura (Fig. 1); posterior and posteroventral margins of the sixth abdominal somite sharply produced posteriorly (Fig. 2 d). Telson (Fig. 2 d) stout, smooth, about 1.5 times as long as wide proximally, greatly tapering distally, with two pairs of small stout dorsal spines, each about 0.08 of telson length, inserted at about 0.2 and 0.7 telson length respectively; posterior margin straight, with 3 pairs of spines, including one pair of short lateral spines, one pair of long intermediate spines and one pair of long spines equal to intermediate spines.

Eyes (Fig. 2 a, b) large, swollen, stout; cornea rounded, pigmented; eyestalk stout, swollen, cylindrical, about as long as wide.

Antennula and antenna slightly reduced. Antennular peduncle (Fig. 2 e) stout, basal peduncular segment robust, about 1.5 times longer than proximal width, without ventromedial tooth, distolateral angle with acute triangular tooth; stylocerite stout, bluntly rounded distally, reaching almost to midlenght of basal segment; second and third segments stout, unarmed, about 1.5 times shorter than wide; proximal fused portion of lateral (=upper) antennular flagellum with at least 8 segments, accessory ramus with 7–8 segments, medial flagellum filiform.

Antenna (Fig. 2 f) stout; basicerite stout, about 1.5 times wider than long, with distolateral margin unarmed; carpocerite slender, overreaching scaphocerite, about 3 times as long as wide; scaphocerite reduced, ear-shaped, with small but well marked distolateral tooth, lamella rounded distally.

Mandible (Fig. 3 a) well developed, without palp; molar process well-developed, relatively slender, with several small distal teeth; incisor process slender, tapering distally, with 4 small triangular teeth distally. Maxillula (Fig. 3 b) with well-developed, bilobed palp, dorsal lobe blunt, ventral lobe with a small curved spinule; dorsal lacinia broad, bluntly expanded distally, distal and medial margins covered with several bunches of long simple setae; ventral lacinia slender, not reaching the distal margin of dorsal lacinia, with several bunches of long simple setae distoventrally and marginally. Maxilla (Fig. 3 c) normal, with simple tapering palp; endites obsolete; basal endite deeply bilobed, furnished with elongated stiff setae; coxal endite obsolete; scaphognathite broad, furnished with short plumose setae. Maxilliped I (Fig. 3 d) normal; epipod rectangular, with distinct lateral notch; exopod slender, with expanded caridean lobe bearing plumose marginal setae; basal and coxal endites completely fused, excavate, furnished with long simple setae distally; palp slender, tapering distally, without distal setae. Maxilliped II (Fig. 3 e) with relatively robust segments; epipod small, oval, elongate; exopod slender overreaching propodal segment, with long plumose setae distally; distolateral margin of propodus straight, dorsal margin convex, furnished with slender setae; dactylus about 3 times as long as broad, with straight distal margin, with numerous medium stout spines and numerous simple spines along distal margin. Maxilliped III (Fig. 3 f) stout, with small arthrobranch; epipod stout, bluntly rounded; exopod slender, overreaching distal margin of antepenultimate segment; antepenultimate segment stout, about 3 times as long as wide; penultimate segment about 5 times as long as wide, with straight lateral margin; ultimate (distal) segment slender, about half length of penultimate segment, about 4 times as long as wide, tapering distally, with numerous tufts of long setae along distolateral margin, with several long setae distally; exopod slender, overreaching the distal margin of antepenultimate segment.

Thoracic sternites unarmed.

Pereiopod I (Fig. 4 a) relatively slender, smooth, segments unarmed; coxa with small rounded distoventral lobe; basis about 1.5 times as long as wide; ischium about 3.5 times as long as wide; merus slender, about 8 times as long as wide, with straight margins; carpus long and slender, widening distally, slightly longer than merus, about twice as long as chela, about 8 times longer than maximal width; palm (Fig. 4 b) about 2.5 times longer than wide, subcylindrical in cross-section; fingers stout, triangular in shape, shovel-like, tapering distally, about 1.5 times as long as proximal width, with simple tips and straight cutting edges.

Pereiopods II unequal in size and slightly dissimilar in shape (Fig. 1). Major pereiopod II (Figs. 4 c, 5 a, b) with smooth unarmed segments including palm; coxa rectangular, as long as wide; basis rectangular, as long as wide; ischium about 2.5 times as long as maximum width, with straight margins, inner margin armed with a double row of small sharp teeth; merus stout, about twice as long as maximal width, with straight margins, inner margin armed with double row of small sharp teeth; carpus stout, swollen, distally excavated, about as long as maximal width, distal margin not overlapping proximal part of propodus; palm convex dorsally, ventral part subcylindrical in a cross-section, not tapering, smooth, finely tuberculate distodorsally, distodorsal margin truncate, forming rectangular distodorsal angle (Fig. 5 c–e); fixed finger (pollex) (Fig. 5 c–e) robust, triangular in shape, tapering distally and slightly curved, smooth, with a well marked deep dorsal depression (“fossa”) distally open; dactylus (Fig. 5 d) about 1.5 times longer than pollex, about twice longer than wide, smooth, opposable margin forming a well marked plunger, distoventral angle armed with a convex finger nail-like apex. Minor pereiopod II (Figs. 4 d, 5 f) morphologically similar to major, but smaller in size; with smooth unarmed segments; coxa rectangular, as long as wide; basis rectangular, as long as wide; ischium about 2.5 times as long as maximum width, with straight margins, inner margin armed with double row of small sharp teeth; merus stout, about twice as long as maximum width, with straight margins, inner margin armed with double row of small sharp teeth; carpus stout, swollen, distally excavated, widening distally, about as long as maximal width, distal margin not overlapping proximal propodus; palm convex dorsally, ventral part subcylindrical in cross-section, not tapering, smooth, finely granulated distodorsally, distodorsal margin truncated, forming rectangular distodorsal angle (Fig. 5 g–i); fixed finger (pollex) (Fig. 5 g–i) robust, triangular in shape, tapering distally and slightly curved, smooth, with well marked deep dorsal depression (“fossa”) open in its proximal part; dactylus (Fig. 5 i) about 1.5 times longer than pollex, about twice as long as wide, smooth, ventral margin with a reduced plunger, distoventral angle armed with convex nail-like apex.

Pereiopod III (Fig. 4 e) relatively stout, smooth; basis rectangular, about as long as wide; ischium about 1.5 times longer than wide; ischium about 2.5 times as long as wide; merus about 3 times as long as wide, with straight margins; carpus stout, about 3 times as long as wide, widening distally, slightly shorter than merus and 1.5 times as long as propodus, with bluntly projecting distodorsal margin slightly overlapping carpo-propodal articulation; propodus about 6 times as long as wide, tapering slightly distally, with straight margins with 5 small spines along ventral margin and a pair of more robust spines at distoventral angle (Fig. 4 f); dactylus (Fig. 4 f) stout, about 1.6 times as long as wide, biunguiculate, with ventral margin serrated, main unguis smooth, curved and sharp; accessory unguis triangular, sharp, about twice shorter than main unguis. Pereiopod IV (Fig. 4 g) and pereiopod V (Fig. 4 h) generally similar to pereiopod III; segments of pereiopod V (Fig. 4 h) covered with simple setae dorsally and ventrally; ventral margin of propodus unarmed.

Pleopods normal, covered with small setae, without specific differentiating features. Uropods (Fig. 2 d) stout, not exceeding telson; lateral margin of uropodal exopod straight, with sharply produced distolateral angle and small curved distolateral spine; diaeresis simple.

Male smaller than female; morphology generally similar to female holotype. Pleopod II with well developed appendix interna and appendix masculina (Fig. 6 f); appendix masculina shorter than appendix interna, with 4 long lateral simple setae and 1 long distal setae.

Measurements. Ovigerous female has pcl. 3.2 mm, tbl. 10.0 mm; male has pcl. 2.5 mm, tbl. 9.0 mm.

Coloration. General appearance of the body and appendages orange semi-transparent (Fig. 7); without any ornament, spots or dots.

Etymology. The species is named after its type locality, Formosa Island (Taiwan).

Host. Shrimps were collected from an unidentified shallow water brown sponginous sponge (Porifera: Demospongiae) growing in a small rock cave at the depth of 5–6 meters.

Distribution. The species presently known only from the type locality, northern Taiwan.