Opaepupu huna, Anker & Grave, 2021

Anker, Arthur & Grave, Sammy De, 2021, Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai’i, Zootaxa 4903 (1), pp. 55-70 : 59-68

publication ID	https://doi.org/ 10.11646/zootaxa.4903.1.3
publication LSID	lsid:zoobank.org:pub:3A46480B-7A61-49D8-9ED5-C0F2FF50491A
DOI	https://doi.org/10.5281/zenodo.4422699
persistent identifier	https://treatment.plazi.org/id/073A87C8-E20A-6B75-FF0C-9F9CFDA55BD3
treatment provided by	Plazi
scientific name	Opaepupu huna
status	sp. nov.

Treatment

Opaepupu huna View in CoL sp. nov.

( Figs. 1–8 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Type material. Holotype: ovigerous female (pocl 3.6 mm, cl 4.3 mm), FLMNH UF 45826 , Hawaiian Archipelago, Hawai’i, Kâne’ohe Bay , outside reef at northern side of bay, 21.504°-157.802°, outer reef slope, depth: 14 m, inside Trapezium oblongum , leg. D. Uyeno and IZ team, 28 May 2017 [fcn BKON 1492 -A] . Allotype: male (pocl 2.3 mm, cl 2.9 mm), FLMNH UF 51717 , same collection data as for the holotype [fcn BKON 1492 -B] .

Description. Small-sized palaemonid shrimp with subcylindrical, dorsoventrally somewhat flattened body; female with greatly enlarged brood chamber ( Figs. 1 View FIGURE 1 , 2C View FIGURE 2 ). Carapace smooth, glabrous, neither densely setose nor pubescent, with few erect setae ( Fig. 2B View FIGURE 2 ). Rostrum moderately developed, subtriangular in dorsal view, as long as wide (female) to 1.2 times longer than wide (male), reaching to about 0.7 of distal margin of first article of antennular peduncle, slender in lateral view; mid-dorsal carina present, non-dentate, flattening slightly posterior to level of post-orbital margin; ventral carina non-dentate; lateral carinae proximally expanded; tip slightly descendant in lateral view, with several apical and subapical setae ( Figs. 2A, B View FIGURE 2 , 6 View FIGURE 6 A–C). Supraorbital, hepatic and epigastric teeth absent ( Figs. 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Orbit well developed, infraorbital angle distinct. Antennal tooth well developed, acute ( Figs. 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Pterygostomial angle well developed, protruding, rounded, almost reaching to level of rostral tip ( Fig. 2B View FIGURE 2 ).

Thoracic sternites without strong teeth, including fourth sternite. Pleon smooth, glabrous; brood chamber of female strongly expanded laterally; posteroventral angle of first five pleura rounded, that of sixth pleonite quadrate, posteriorly unarmed ( Figs. 1 View FIGURE 1 , 2D View FIGURE 2 , 6D, E View FIGURE 6 ).

Telson broad, distally tapering, about 1.6 and 2.2 times as long as proximal width in female and male, respectively; dorsal surface with wide median depression and two pairs of submarginally inserted, stout cuspidate setae, latter noticeably stouter in male; anterior pair situated at about 0.25 and 0.18 of telson length in female and male, respectively; posterior pair situated at about 0.55 of telson length in both female and male; posterior margin slightly rounded, with two pairs of small, elongate spiniform setae and three (female) or one pair (male) of longer, submedian, sparsely plumose setae; mesial spiniform setae about 1.5 times to twice as long as lateral spiniform setae ( Figs. 2 View FIGURE 2 D–F, 6E, F).

Eye peduncle robust; cornea well developed, globular, about 0.6 times as wide as maximal peduncle width; accessory eye (nebenauge) absent ( Figs. 2A, B View FIGURE 2 , 6A View FIGURE 6 ).

Antennule robust, short; first article longest and widest, ending in subtriangular, blunt distolateral lobe, without sharp tooth; stylocerite small, distally obtusely triangular; second and third article about 0.35 times as long as visible portion of first article; lateral flagellum with short accessory ramus, comprised of single unit ( Figs. 2A, B, G View FIGURE 2 , 6A View FIGURE 6 ). Antenna with basicerite unarmed; carpocerite reaching to distal end of second article of antennular peduncle; scaphocerite well developed, broad, ovoid, reaching far beyond antennular peduncle; blade about 1.8 times as long as maximal width; distolateral tooth vestigial ( Figs. 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Epistome unarmed.

Mandible with incisor and molar processes widely separated; palp absent; incisor process well developed, with six sharp teeth; molar process distally with micro-serration and low bosses ( Fig. 3A, B View FIGURE 3 ). Maxillule with both laciniae well developed; palp bilobed distally, ventral lobe more developed, with small, acute, tooth-like ventral extension and long, simple, dorsal seta; dorsal lobe short, unadorned ( Fig. 3C View FIGURE 3 ). Maxilla with palp (endopod) well developed, not subdivided; basial endite with deep cleft; coxal endite reduced; scaphognathite well developed ( Fig. 3D View FIGURE 3 ). First maxilliped with basial and coxal endites broad, clearly separated; palp (endopod) absent [or at least reduced, not visible in lateral view]; exopod short, with well-developed caridean lobe and moderately long flagellum; epipod well developed, bilobed ( Fig. 3E View FIGURE 3 ). Second maxilliped with endopod typical for family; exopod moderately long; epipod well developed, without podobranch ( Fig. 3F View FIGURE 3 ). Third maxilliped pediform, moderately stout; lateral plate of coxa rounded; ischiomerus and basis fused into single, broad antepenultimate article; ultimate article about 0.8 times as long as penultimate article, distally tapering; exopod well developed, overreaching distal margin of antepenultimate article; arthrobranch absent ( Fig. 3G View FIGURE 3 ). Epistome with median carina; paragnaths rounded, unarmed ( Fig. 3H View FIGURE 3 ).

First pereiopods symmetrical in shape, equal in size; relatively short, stout; ischium stout, unarmed, somewhat widening distally; merus unarmed, about 6.5 times as long as maximal width; carpus slightly longer than merus, distally widening; chela about 0.75 times as long as carpus; fingers about as long as palm, non-spatulate, with entire, non-dentate cutting edges; fingertips not strongly curved, simple ( Fig. 5A, B View FIGURE 5 ).

Second pereiopods (chelipeds) of female holotype subequal in size, symmetrical, i.e. similar in shape, not particularly enlarged, moderately setose; all articles with smooth surface; ischium rectangular, about 2.5 times as long as distal width; merus rectangular, slightly longer than ischium, about 2.3 times as wide as long; carpus vase-shaped, about as long as merus; chela not swollen, smooth, without grooves or superficial sculpture; fingers about 0.7 times as long as palm; cutting edge of fingers proximally dentate, distally unarmed (pollex) or with very low tooth and broad convexity (dactylus); proximal tooth of pollex distally truncate, with minute rugosities; distal tooth of pollex subtriangular; dactylus with two subtriangular teeth, proximal much stronger than distal; fingertips strongly crossing ( Fig. 4 View FIGURE 4 A–H). Second pereiopods (chelipeds) of male paratype generally similar to those of female, somewhat stouter; fingers slightly gaping between 0.3 and 0.5 of their length; dactylus with very stout, distally truncate and rugose proximal tooth, and much smaller subtriangular distal tooth ( Fig. 7 View FIGURE 7 A–E).

Third to fifth (ambulatory) pereiopods relatively slender, generally similar in shape and size. Third pereiopod with ischium about 3.5 times as long as wide, unarmed; merus about 1.6 times as long as ischium, about 5.5 times as long as wide, unarmed; carpus more slender than merus, about 0.45 times as long as merus, about 3.5 times as long as wide, unarmed; propodus about twice as long as carpus, about 7.5 times as long as wide, distally somewhat curved, unarmed; dactylus relatively slender, about 0.3 times as long as propodus, compressed, biunguiculate; main (terminal) unguis slender, acute; corpus with single sharp subdistal tooth (= secondary or accessory unguis), latter stouter but shorter than terminal unguis and running almost parallel to it ( Fig. 5C, D View FIGURE 5 ). Fourth pereiopod (not illustrated) generally very similar to third. Fifth pereiopod generally similar to third; propodal cleaning brush absent ( Fig. 5E, F View FIGURE 5 ).

First pleopod sexually dimorphic in proportions, lacking appendix interna in both sexes; in female, endopod short, approximately 0.3 length of exopod ( Fig. 2G View FIGURE 2 ); in male, endopod about 0.53 length of exopod, fringed with stiff, slender, subspiniform setae; exopod fringed with plumose setae ( Fig. 6F View FIGURE 6 ). Second to fifth pleopods broadly similar with endopod being slightly shorter than exopod, bearing appendix interna ( Fig. 2I View FIGURE 2 ). Second pleopod of male with appendix masculina slightly shorter than appendix interna, furnished with stiff, slender, subspiniform setae on apex and subapically ( Fig. 6G View FIGURE 6 ).

Uropod with lateral lobe of protopod ending bluntly; exopod and endopod subequal, distinctly overreaching telson; exopod broadly ovoid; distolateral tooth reduced; adjacent distolateral spiniform seta minute in female, slightly larger but still small, in male; diaeresis feebly developed, unarmed, visible only in its lateral section in female, visible over its entire length in male, sinuous; endopod narrowly ovoid, without specific features ( Figs. 2D, J View FIGURE 2 , 6D, E View FIGURE 6 ).

Colour pattern. Female: Body translucent with numerous rounded to star-shaped groups of white chromatophores, especially numerous on dorsal surface of carapace and pleon, less numerous on tail fan and antennae; chelipeds and walking legs colourless, with some slight iridescence; ovaries and fresh eggs bright yellow ( Fig. 8A View FIGURE 8 ). Male: Body translucent with numerous groups of white chromatophores, mostly concentrated on dorsal surface of carapace and pleon, with some isolated white chromatophores on pleon; tail fan, antennae, chelipeds and walking legs mostly colourless, with some slight iridescence ( Fig 8B View FIGURE 8 ).

Etymology. The species name ( huna ) is derived from the Hawaiian word hűnâ, meaning secretive, hidden, in reference to the shrimps’ highly cryptic life style inside bivalves; used as a noun in apposition.

Type locality. Kâne’ohe Bay, Hawai’i Island, Hawaiian Islands .

Distribution. Presently known only from the type locality in Hawai’i.

Ecology. The single known pair of the new species was found on a reef slope, inside the mantle cavity of the bivalve Trapezium oblongum (Linnaeus, 1758) (Trapezidae) .

Remarks. See generic account.