Unesconia coibensis, Anker, 2020

Anker, Arthur, 2020, Unesconia coibensis, gen. et sp. nov., a miniature sponge-associated shrimp from a biodiversity hotspot in the tropical eastern Pacific (Decapoda: Palaemonidae), Zootaxa 4731 (1), pp. 115-133 : 119-126

publication ID	https://doi.org/ 10.11646/zootaxa.4731.1.8
publication LSID	lsid:zoobank.org:pub:7E0728D4-2F47-473A-B001-49084FDB7BA3
DOI	https://doi.org/10.5281/zenodo.5920942
persistent identifier	https://treatment.plazi.org/id/EA68F531-5C66-4B7C-E382-64F17DE478EA
treatment provided by	Plazi
scientific name	Unesconia coibensis
status	sp. nov.

Treatment

Unesconia coibensis View in CoL sp. nov.

Figs. 1–10 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10

Type material. Holotype: ovigerous female (pocl 2.0 mm, cl 3.1 mm), FLMNH UF 51926 , Panama, Pacific coast, Coiba Archipelago , Canales de Afuera (channel between Isla Afuera and Isla Afuerita), channel between small islet and northern side of Isla Afuera, 7.695249N– 81.635710W, shallow subtidal sand flat with abundance of fragmented coral rubble and living colonies of Pocillopora , depth: 1–2 m at low tide, in large piece of coral rubble, presumably associated with yellowish incrusting sponge, leg. A. Anker & P.G.P. Pachelle, 19 February 2019 [fcn PAN-99] GoogleMaps . Allotype: male (pocl 1.7 mm, cl 2.8 mm, minor second cheliped regenerating), FLMNH UF 51927 , same collection data as for the holotype [fcn PAN-100] GoogleMaps . Paratypes: 1 ovigerous female (pocl 2.1 mm, cl 3.0 mm), FLMNH UF 51928 , same collection data as for the holotype [fcn PAN-98]; 1 ovigerous female (pocl 1.7 mm, cl 2.8 mm), FLMNH UF 51929 , same collection data as for the holotype [fcn PAN-97] GoogleMaps .

Description. Small-sized pontoniine shrimp with dorsoventrally somewhat flattened body ( Fig. 1 View FIGURE 1 ). Carapace smooth, glabrous, neither setose nor pubescent ( Fig. 1 View FIGURE 1 ). Rostrum well developed; dorsal carina strong, dentate, with typically four teeth, sometimes only two teeth; ventral carina unarmed; tip reaching to at least distal margin of first article of antennular peduncle, usually to end of antennular peduncle; lateral carinae proximally expanded, each side with one strong, anteriorly pointing, simple supraorbital tooth ( Fig. 2A, B View FIGURE 2 , F–H). Orbit well developed; inferior orbital angle distinct; epigastric and hepatic teeth absent; antennal tooth strong, acute; pterygostomial angle distinctly protruding, acute or subacute ( Fig. 2A, B View FIGURE 2 , F–H).

All thoracic sternites unarmed, fourth without median process. Pleon smooth, glabrous; posteroventral margin of first four pleura rounded, that of fifth pleuron angular, that of sixth pleonite subacutely produced ( Fig. 1 View FIGURE 1 ). Telson relatively short and broad, about 1.5 times as long as maximal (proximal) width; dorsal surface with two pairs of very stout, long cuspidate setae, inserted close to lateral margin and reaching to or well beyond it, anterior pair inserted at about 0.3 length of telson, posterior pair at about 0.7 length of telson; posterior margin rounded, with three pairs of robust, elongate spiniform setae; most lateral spiniform setae about as long as dorsal cuspidate setae; intermediate spiniform setae longest, more than twice as long as lateral, slightly stouter; median spiniform setae slenderest, longer than lateral but much shorter than intermediate ( Fig. 2C, D View FIGURE 2 ).

Eye peduncles robust; cornea well developed, globular; accessory eye (Nebenauge) small ( Fig. 2A, B, G View FIGURE 2 ).

Antennule robust, stout, short, with first article longest and widest, ending in stout, simple, sharp distolateral tooth; stylocerite small, well developed, acute distally; second and third articles very short; lateral flagellum with short accessory ramus and several groups of aesthetascs ( Fig. 2A, B, G, H View FIGURE 2 ). Antenna with relatively small basicerite armed with small subacute tooth on distoventral margin; carpocerite short, not reaching distal margin of first article of antennular peduncle; scaphocerite well developed, with broad blade and strong distolateral tooth, reaching far beyond end of antennule ( Fig. 2A, B, G, H View FIGURE 2 ).

Mouthparts of non-filtering type. Mandible without palp; incisor process with at least two distal teeth; molar process with distal micro-serration and fields of short setae ( Fig. 3 View FIGURE 3 A–C). Maxillule with both laciniae fairly broad; palp bilobed distally, ventral lobe more developed, with short hook-shaped seta, dorsal lobe short, without seta ( Fig. 3D View FIGURE 3 ). Maxilla with palp (endopod) moderately broad, not subdivided; endite with deep cleft; scaphognathite fairly broad ( Fig. 3E View FIGURE 3 ). First maxilliped with palp (endopod) narrow, short, tapering distally, not subdivided; endite broad, with small notch indicating subdivision; exopod short, caridean lobe well-developed, broad; epipod moderately developed, bilobed ( Fig. 3F View FIGURE 3 ). Second maxilliped not especially modified; shape of endopod typical for family; exopod moderately long; epipod moderately developed, subquadrate, without podobranch ( Fig. 3G View FIGURE 3 ). Third maxilliped pediform, moderately stout; lateral plate of coxa broadly rounded, not protruding; antepenultimate article (ischiomerus) and basis distinct, separated from each other by narrow complete suture; antepenultimate article with rounded lateral ridge, about 4.5 times as long as wide; penultimate article somewhat shorter than antepenultimate article; ultimate article shortest, about 0.6 times length of penultimate article, tapering distally; exopod falling short of distal margin of antepenultimate article; arthrobranch apparently absent (or greatly reduced and detached during dissection) ( Fig. 3H View FIGURE 3 ). Epistome (median lip) unarmed ( Fig. 3I View FIGURE 3 ); paragnaths without remarkable features.

First pereiopods symmetrical in shape and equal in size, relatively short and stout; coxa with stout, anteriorly protruding process on anteroventral surface; ischium stout, widening distally; merus about four times as long as maximal width; carpus about 0.8 times as long as merus, depressed ventrally; chela as long as carpus; fingers noticeably shorter than palm, broadened, subspatulate (deeply excavated on cutting surfaces), fingertips strongly tridentate, with teeth sharp, fitting into corresponding hiatuses on opposing tips ( Fig. 4 View FIGURE 4 ).

Both second pereiopods (chelipeds) enlarged, robust; chelae more or less swollen, unequal in size, asymmetrical in shape, moderately setose; major chela more swollen than minor chela, with very different finger armature; sexual dimorphism of major cheliped not significant. Major cheliped with ischium very short, widening distally; merus stout, less than twice as long as maximal width, ventromesial margin with small rugosities; carpus short, cupshaped; chela moderately swollen (slightly more swollen in male), surface smooth except for minute tubercles along ventral and dorsal surfaces of palm and ventral margin of pollex; fingers about half as long as palm, cutting edges with two opposing deep fossae, one on pollex and one on dactylus ( Figs. 5 View FIGURE 5 A–D, 6, 7). Female minor cheliped with ischium, merus and carpus very similar to those of major cheliped; carpus slightly longer; chela much less swollen, slenderer, surface smooth, except for minute tubercles along ventral and dorsal surfaces of palm and near base of pollex; fingers subequal in length to palm, cutting edges unarmed; pollex shallowly excavated on each side of cutting edge ( Fig. 5E, F View FIGURE 5 ). Male minor cheliped presently unknown (regenerating in male allotype).

Third to fifth (ambulatory) pereiopods relatively slender, diminishing in robustness from third to fifth, similar in shape. Third pereiopod with ischium about three times as long as wide, unarmed; merus slightly swollen, with feebly convex margins, 4.5 times as long as maximal width, unarmed; carpus noticeably slenderer than merus, slightly less than half-length of merus, unarmed; propodus twice as long as carpus, slender, ventral margin with four small but stout spiniform setae, including terminal one at propodo-dactylar articulation; dactylus moderately stout, compressed, slightly more than 0.2 length of propodus; unguis slender, acute; corpus with one large distal tooth, stouter than unguis, almost parallel to unguis; ventral margin of corpus with two or three smaller articulated spinules (sometimes minute) ( Fig. 8 View FIGURE 8 A–C). Fourth pereiopod generally similar to third pereiopod, but noticeably slenderer; merus not swollen, with straight margins; propodus and dactylus similar to those of third pereiopod ( Fig. 8 View FIGURE 8 D–F). Fifth pereiopod slenderest; ischium almost four times as long as wide; merus not swollen, with straight margins, more than six times as long as maximal width; propodus much more slender and proportionally longer than that of third or fourth pereiopod, with two slender spiniform setae (sometimes not visible in lateral view), including terminal one at propodo-dactylar articulation; distal ventrolateral surface with four rows of serrulate setae forming propodal cleaning brush; dactylus similar to that of third pereiopod, somewhat stouter ( Fig. 8G, H View FIGURE 8 ).

Male second pleopod with well-developed appendix masculina furnished with at least six stiff setae on apex and margin opposed to endopod; appendix interna longer than appendix masculine masculina ( Fig. 8I, J View FIGURE 8 ). Uropod with lateral lobe of protopod acutely produced; exopod broadly ovoid, with small distolateral tooth; diaeresis (transverse suture) abruptly curved near its lateral end, typically with five strong spiniform setae, third (most central) spiniform seta strongest and longest, sometimes with four spiniform setae; none of spiniform setae extending to exopod’s lateral margin; endopod narrowly ovoid, without specific features (Fig; 2C, E, I).

Colour pattern. Females: body semi-translucent, pale to more intense yolk-yellow, second pereiopod chelae lemon-yellow, walking legs and tail fan transparent with yellow tinge ( Fig. 9 View FIGURE 9 , 10A, B View FIGURE 10 ). Male: body and appendages, including second pereiopod chelae semi-translucent lemon-yellow; waking legs, antennae and proximal half of palm of second pereiopod chela with conspicuous white spots ( Fig. 10C View FIGURE 10 ).

Etymology. The specific epithet refers to the Coiba Archipelago / Coiba National Park, which includes Canales de Afuera islands, its type locality; used as an adjective.

Type locality. Canales de Afuera , Coiba Archipelago, Pacific coast of Panama .

Distribution. Presently known only from the type locality on the Pacific coast of Panama.

Ecology. All specimens of Unesconia coibensis gen. et sp. nov. were extracted from a large (about 70 cm long and 50 cm wide) dead coral head ( Pocillopora damicornis ), which was partly immerged into surrounding coarse sand mixed with smaller fragments of coral rubble, in very shallow water (1–2 m at low tide). The collection site was also characterised by a noticeably stronger and colder current due to the constant water flow between a small islet and the main island of Isla Afuera. The shrimps were likely associated with a yellow incrusting sponge growing deep inside the dead coral crevices; a small fragment of this sponge preserved in ethanol was deposited in the FLMNH sponge collection for further studies (FLMNH Porifera 4384). However, it must be noted that the specimens were falling out of the broken-up dead coral head, which possibly contained other incrusting sponges. The association of U. coibensis sp. nov. with that particular yellow sponge was presumed based on its large extension inside the coral head and on the similarly yellow colouration of the shrimps.

Taxonomic remarks. See under genus.