Alcyonohippolyte tenuicarpus, Marin, Ivan, 2011

Marin, Ivan, 2011, Two new species of alcyonacean-associated shrimp genus Alcyonohippolyte Marin, Okuno & Chan, 2010 (Crustacea: Decapoda: Hippolytidae) from the Great Barrier Reef of Australia, Zootaxa 3123, pp. 49-59 : 50-54

publication ID	https://doi.org/ 10.5281/zenodo.203589
DOI	https://doi.org/10.5281/zenodo.6191268
persistent identifier	https://treatment.plazi.org/id/39568D6A-E42C-2139-C4FA-BFD9FE8DF861
treatment provided by	Plazi
scientific name	Alcyonohippolyte tenuicarpus
status	sp. nov.

Treatment

Alcyonohippolyte tenuicarpus View in CoL sp. nov.

( Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Material examined. Holotype, ovigerous female (plc. 3.2 mm, tl. 15 mm), QM W33518, GBR of Australia, Lizard Island area, Lagoon, Channel, patch reef, LI10-030, 14º41.171’S 145º27.302’E, 10 meters, on soft coral Heteroxenia sp., coll. I. Marin, 28 Aug. 2010.

Paratypes, 5 ovigerous females (pcl. 3.0, 3.0, 2.8, 2.7, 2.6 mm), 1 non-ovigerous female (pcl. 2.0 mm) (QM W33513), locality and host same to holotype.

Description. Paratype female (QM W33513). Carapace ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A–C) smooth, without setae, dorsal surface non-gibbous; with supraorbital, antennal and hepatic teeth, antennal tooth acute, situated slightly below orbital angle; hepatic tooth acute, larger and more slender than antennal, not reaching the distal margin of carapace, situated below and slightly behind the level of antennal tooth ( Fig. 2 View FIGURE 2 B, C). Rostrum long, compressed, unarmed, overreaching antennular peduncle, proximal lateral rostral lamina with sharp supraorbital tooth situated above the level of proximal orbital margin ( Fig. 2 View FIGURE 2 A). Orbit well developed, inferior orbital angle blunt, produced distally. Pterygostomial angle bluntly projected.

Abdominal somites ( Fig. 1 View FIGURE 1 ) smooth, naked and unarmed; pleurae of abdominal somites I–V rounded. Telson ( Fig. 2 View FIGURE 2 D) slender, about 5 times as long as proximal width, narrowing posteriorly, with 2 pairs of small submarginal dorsal spines at 0.4 and 0.65 of telson length; distal margin of telson armed with 3 pairs of spines including pair of short stout lateral spines.

Eyes normal, well developed, with subcylindrical eyestalk and subovate cornea; eyestalk about 1.5 times as long as wide; cornea suboval, without papilla.

Antennula ( Fig. 2 View FIGURE 2 F, G) well developed; basal segment about twice longer than wide, with small ventromedial tooth, with acute distolateral tooth which reaching the midlength of intermediate segment, inner distolateral angle covered with long setose setae; stylocerite well developed, acute, not reaching the distal margin of basal segment; intermediate segment stout, about 1.5 times longer than wide, with slightly convex inner lateral margin bearing long setose setae; distal segment stout, about as long as wide, with long setose setae along inner lateral margin; proximal part of upper antennular flagellum with 8 segments, shorter ramus with 2–3 stout segments.

Antenna ( Fig. 2 View FIGURE 2 H) normal, well developed; basicerite armed with small triangular tooth distoventrally, slightly overreaching the distal margin of the segment; carpocerite stout, about as long as wide, not reaching the midlength of scaphocerite; flagellum well developed; scaphocerite wide, greatly overreaching antennular peduncle, about twice longer than maximal width, with well developed acute distolateral tooth not reaching the distal margin of blade.

Mouthparts are characteristic for the genus. Mandible robust ( Fig. 3 View FIGURE 3 A, B), without palp; incisor process well marked, with sharp tip and 4 well-marked large sharp teeth and several small teeth; molar process robust, with stout sharp distal teeth. Maxillula ( Fig. 3 View FIGURE 3 C) normal, with well-developed palp, ventral lobe armed with long simple setae; upper lacinia wide, with convex ventral margin, flaring distally, with numerous stout setae along distoventral margin; lower lacinia more slender and short, tapering distally, covered with long simple setae. Maxilla ( Fig. 3 View FIGURE 3 D) with simple slender blunt palp; endites completely fused, armed with stiff, short stout setae as well as some elongated setose setae at distodorsal angle; scaphognathite well developed, fringed with setose setae. Maxilliped I ( Fig. 3 View FIGURE 3 E) with completely fused endites, armed with short stout setae along distal margin as well as some elongated setose setae along distodorsal angle; exopod well developed, with well-marked caridean lobe furnished with setose setae; epipod ear-shaped, bilobed distally. Maxilliped II ( Fig. 3 View FIGURE 3 F) with well-developed exopod, fringed with setose setae distally; ischium stout, with long setose setae along lateral margin; propodal segment short, length equal to dactylar segment, with convex dorsal margin furnished with long simple setae, ventral margin unarmed; dactylar segment convex, armed with numerous stout and long simple setae along distal margin; epipod well marked, distally bilobed. Maxilliped III ( Fig. 3 View FIGURE 3 G) large and stout, overreaching scaphocerite and antennular peduncle; exopod well marked, not reaching distal margin of ischiomeral segment; ischiomeral segment about 4 times as long as wide, slightly tapering distally; penultimate segment about twice longer than wide, smooth; terminal segment about 3 times as long as wide, with distal margin oblique, armed with a row of strong spines distally; arthrobranch well developed.

Pereiopod I ( Fig. 4 View FIGURE 4 A) robust, unarmed; coxa with arthrobranch; basis with small lobe distoventrally; ischium stout, about as long as wide, with long simple setae along ventral margin; merus stout, about twice longer than wide; carpus stout, shorter than merus and equal to the length of propodus, about as long as wide, flaring distally, distal margin overlapping carpo-propodal articulation, with a row of stout setose setae along distoventral margin; palm about as long as wide, subcylindrical, smooth; fingers stout, slightly longer than palm, subspatulate, about as long as wide, cutting edges armed with several large acute teeth.

Pereiopod II relatively slender, segments unarmed ( Fig. 4 View FIGURE 4 B); coxa with arthrobranch; basis with small lobe distoventrally, about as long as wide; ischium about as 3 times as long as wide, smooth; merus about 6 times as long as wide, with straight margins; carpus subdivided into 3 subsegments with ratio of about 1: 1: 1.5, proximal segment about 3.5 times as long as wide, about 1.5 times longer than medial (the 2nd) segment, medial segment about twice longer than wide, equal to the distal segment; palm subcylindrical, slightly shorter than distal carpal segment, about as long as wide, with straight smooth margins; fingers robust, equal to the length of palm, about 2.5 times as long as wide, subspatulate, cutting edges armed with several large acute teeth.

Pereiopods III–V similar, relatively slender, with unarmed segments. Pereiopod III ( Fig. 3 View FIGURE 3 C) with basis about as long as wide; ischium about 3 times longer than wide; merus about 5 times as long as wide, with straight margins, bearing large movable spine at distoventral angle; carpus about 4 times as long as maximal width, slightly flaring distally, with distodorsal margin overhanging proximal part of propodus; propodus about 8 times as long as wide, with straight and smooth margins, ventral margin unarmed, without spines at distoventral angle; dactylus slender, basal part about 1.5 times as long as maximal width, swollen, with elongated and curved main unguis, without accessory tooth.

Pleopods normal. Uropods slender, slightly exceeding telson ( Fig. 2 View FIGURE 2 d); distolateral margin of exopod without fixed tooth, with long mobile spine only ( Fig. 2 View FIGURE 2 E).

Coloration. Body coloration similar to the coloration of host soft coral: body generally brown, covered with pale white bands ( Fig. 5 View FIGURE 5 ); rostrum and dorsal surface of carapace, abdomen and telson covered with wide longitudinal dorsal and lateral white bands; wide longitudinal band situated through ventral margin of carapace and pleurae of abdominal somites I–V; the spaces between these bands covered with thinner numerous bended pale white and brown transversal stripes; maxilliped III and pereiopod I brown, ambulatory pereiopods II–V transparent; eyestalk with longitudinal white and brown stripes; scaphocerite and uropods generally pale white with large transparent spots.

Differential diagnosis. The new species can be readily separated from all congeners by a long rostrum greatly overreaching the antennular peduncle and slender carpal segments of pereiopod II; for example, segment 2 of carpus is about twice longer than wide while it is usually as long as wide in the remained species of the genus. The color pattern of the species and the host are also unique within the genus.

Host. The specimens were collected from a large colony of xeniid soft coral Heteroxenia sp. ( Alcyonacea : Alcyoniidae ). All shrimps were found attached to long soft peduncles of longer corallites with their heads turned down.

Etymology. The species is named after its slender carpal segments of pereiopod II, which is the distinctive feature of the species within the genus; tenuis [e] (Latin)—thin, slender, elongated. The species name is a noun in apposition ( tenuicarpus , -i) and does not change with the gender of the genus.

Size. The largest ovigerous female (holotype) has plc. 3.2 mm, tl. 15 mm; males of this species are presently unknown.

Distribution. The present species is known from the type locality only, Lizard Island, the Great Barrier Reef of Australia.