Lepidophthalmus natesi, Felder, Darryl L. & Robles, Rafael, 2015

Felder, Darryl L. & Robles, Rafael, 2015, Two new species of the genus Lepidophthalmus (Decapoda, Axiidea, Callianassidae) from coastal Pacific waters of Central America, Zootaxa 4020 (3), pp. 431-452 : 432-441

Lepidophthalmus natesi sp. nov.

Figures 1 a – g; 2 a–k; 3 a – j

“ Lepidophthalmus nov. sp.”—Felder et al. 2003: table 1; fig. 3 A, B; fig. 7.

Type material. Pacific coast of Colombia. Holotype: male, cl 16.7 mm ( USNM 1275006), = ULLZ 6057 tissue/ sequence voucher, Tumaco, Colombia (01°46.64'N, 78°46.30'W), bottom of partially drained commercial shrimp culture ponds, clayey to silty mud, 18 November 1995, S. F. Nates. Paratypes: 2 males, cl 11.0, 5.9 mm ( USNM 1275007), 1 female (ovigerous), cl 15.5 mm ( USNM 1275008), 39 males, cl 3.3 – 16.1 mm, 44 females (6 ovigerous), cl 3.9 – 16.6 mm ( ULLZ 6051), Tumaco, Colombia, Pacific coast (01°46.64'N, 78°46.30'W), bottom of partially drained commercial shrimp culture ponds, clayey to silty mud, 18 November 1995, S. F. Nates.

Pacific coast of Nicaragua. Paratypes: 1 male, cl 15.5 mm, 1 female, cl 12.7 mm, photographic vouchers ( ULLZ 4509), 1 male, cl 12.4 mm ( ULLZ 5174), 1 male, cl 13.2 mm, 1 pleon unsexed ( ULLZ 11809), 4 males, cl 9.7 – 14.3 mm, 4 females, cl 10.1 – 13.6 mm ( UNAM / CNCR 30003), Estero de Las Peñitas (12°21.66'N, 87°01.25'W), intertidal sand flats and clayey mudflats beside and among mangroves, 27 September 2000, D. L. Felder and R. Robles; 1 male, cl 19.2 mm ( ULLZ 5772), ephemeral opening of lower Estero Ciego (12°39.47'N, 87°22.53'W), muddy intertidal sand flats, 29 September 2000, D. L. Felder and R. Robles; 1 female, cl 12.0 mm ( ULLZ 4632), 1 female, cl 13.2 mm ( ULLZ 4633), 1 male, cl 15.6 mm ( ULLZ 4638), 1 male, cl 12.4 mm, 1 female, cl 10.0 mm ( ULLZ 10872) Estero de Las Peñitas (12°21.66'N, 87°01.25'W), sand flats and clayey mudflats among mangroves, some found with alpheid symbiont, 14 August 2001, D. L. Felder and R. Robles; 1 male, cl 16.6 mm, photographic voucher ( ULLZ 10838), 1 male, cl 10.6 mm, photographic voucher ( ULLZ 13970), 1 female, cl 17.1 mm ( ULLZ 10839), ephemeral opening of lower Estero Ciego (12°39.47'N, 87°22.53'W), muddy intertidal sand flats, 15 August 2001, D. L. Felder and R. Robles; 1 male, cl 14.9 mm, 1 female (ovigerous), cl 14.3 mm ( USNM 1275009), 1 female, cl 13.8 mm, parental for larval hatch ( ULLZ 11828), beach near Paso de Caballos (12°31.51'N, 87°12.63'W), muddy sand ephemeral back-beach tidal pond, 30 September 2000, D. L. Felder and R. Robles; 1 male, cl 14.2 mm ( ULLZ 4634), 1 male, cl 16.4 mm ( ULLZ 4635), 2 males, cl 13.8, 14.7 mm, 4 females, cl 13.2 – 14.2 mm ( ULLZ 10884), beach near Paso de Caballos (12°31.51'N, 87°12.63'W), muddy sand ephemeral back-beach tidal pond, 16 August 2001, D. L. Felder and R. Robles; 2 females (1 ovigerous), cl 12.9, 13.3 mm ( USNM 1275010), Estero Aserradores, Nicaragua, Pacific coast (12°37.35'N, 87°20.54'W) muddy sand with areas of exposed rock, 29 September 2000, D. L. Felder and R. Robles.

Diagnosis. Rostrum acute, spiniform, inclined or sloped dorsally as weak arch, flanked by rounded shoulders centered lateral to eyestalks. Flattened mesial margins of subtrapezoidal eyestalks closely opposed proximally, weakly divergent near tips, tips acute to subacute. Antennule with dorsal ramus of flagellum shorter than third article of peduncle. Antenna with third article of peduncle very sparsely setose laterally. Inferior margin of male cheliped merus dominated by strong single multidentate keel, weak evidence of parallel carina, proximal hook spatulate, terminating in multiple spines or teeth. Superior margin of merus lacking proximal notch. Propodus of male major chela with distal inferior corner forming origin of round-edged carina extending short distance vertically onto external face as subdistal margin of article. Dactyl of male major chela prehensile margin with small obliquely transverse basal molar tooth set close to weakly bilobed heavy coniform median tooth in proximal half, separated by broad deep notch from elongate narrow distal tooth, distal tooth with dentate prehensile margin declining in elevation distally. First pleonal tergite with dorsal sclerite broadening to medially centered truncate lobe posteriorly, lacking isolated posterolateral sclerotized plate in membrane to each side. Most of second pleomere ventrally leathery, lacking sclerotized medial plate. Male first pleopod terminal article slightly compressed, strongly bifurcate, deep incision between blades, subdistal blade well-developed, overreached by arching distal blade. Appendix of male second pleopod well-developed, reaching beyond narrowed distal end of endopod in mature. Second through fifth pleopods lacking acute distolateral spine on anterior of basis. Telson posterior margin distinctly trilobate. Uropodal endopod narrow, elongate subtrapezoidal, broadest distal to midlength, length more than twice breadth. GenBank accession numbers for 16S and 12S mt sequences of type materials are reported by Robles & Felder (2015: table 2).

Description. Frontal margin of carapace with acute, narrow rostral spine flanked laterally by rounded shoulders centered lateral to eyestalks ( Fig. 1 a; Fig. 4 a, c, d); rostral spine variably inclined dorsally, usually somewhat arched above eyestalks in mature specimens, extending 2/3 to full length of eyestalks in dorsal view, proximal half or less of rostral spine undercut ventrally, proximal ventral surface fully covered by fine, dense elongate setae extending above and between eyestalks. Carapace postorbital region with several paired short tufts of setae, usually 2 – 3 aligned immediately to each side of midline; dorsal oval well-defined, smooth, pair of widely separated setal punctae bearing 1 – 2 setae each well anterior to midlength; marginal suture of oval diminished at postrostral midline, strong at posterior end with sclerotized suture to bulbous cardiac region on posterior midline.

Eyestalks elongate subtrapezoidal in dorsal view, reaching at least 3/4 length of basal antennular article ( Fig. 1 a); anterolateral margin forming rounded corner of varied acuity and prominence, distal margin obliquely sloped mesially toward protruding distal tip; dorsomesial margin forming slightly elevated ridge in distal 1/3, ridge extending from acute or subacute tip of eyestalk to elevated, rounded tubercle positioned distal to mesial margin of cornea; well-defined, distinctly faceted cornea centered on dorsal surface.

Antennular peduncle longer and heavier than antennal peduncle ( Fig. 1 a); basal article dorsally invaginated to form statocyst occluded by setae, overlain by eyestalk; second and third articles with dense ventromesial and ventrolateral rows of long, distoventrally directed setae. Antennular flagellum ventral ramus similar in length and setation to third article of peduncle, setae much longer, denser than on dorsal ramus; dorsal ramus shorter than third article of peduncle, becoming heavier distally where subterminal articles broader than those of adjacent ventral ramus, there fringed with slightly elongate, dense ventral setae.

Antennal peduncle reaching at least to midlength of antennular peduncle third article; basal article dorsolateral carina arched to form lip above excretory pore, ventrally with setose rounded weak distal protuberance; second article with distal field of long setae on vertically oriented lateral boss; fourth article about equal to combined lengths of first two, slightly shorter than fifth, lateral setae sparse, limited to short oblique line of 3–5 in proximal third, small tuft in distal 1/4; fifth article narrower than others, setation limited to few long subterminal setae in single punctum. Antennal flagellum about 3.5 times length of antennular flagellum, longest of sparse setae slightly exceeding 2 flagellum articles in length.

Mandibular palp ( Fig. 1 b) large, setose, 3-segmented, third article robust, arched, elongate subovoid; gnathal lobe of mandible subquadrate, rounded corner forming angular distolateral shoulder, incisor process with welldefined corneous teeth on cutting margin, concave internal face with strong lip giving rise to molar process bearing weakly bilobed corneous tooth proximal and internal to incisor teeth; thin, rounded paragnath set against proximal convex face of molar process. First maxilla ( Fig. 1 c) endopodal palp narrow, terminal article deflected at poorly defined articulation; proximal endite with dense, close-set setation lining sinuous mesial margin, setae spiniform distally; distal endite elongate, terminally broadened with dense long setae, some rows strongly spiniform; exopodite low, rounded. Second maxilla ( Fig. 1 d) margins setose, endopod constricted to narrow terminus, first and second endites each longitudinally subdivided, exopod forming large, broad scaphognathite.

First maxilliped ( Fig. 1 e) margins setose, endopod rudimentary, overlain by distal endite; blunt terminus of proximal endite setose; distal endite ovoid, narrowed distally, proximal 2/3 of external face with densely setose longitudinal elevation; exopod incompletely divided by oblique suture on external face, transverse suture obsolete on most of internal face, obvious proximolaterally near margin before intersection of lateral incision; margin lined by long setae, more arched distal than proximal to incision, rounded at distal extreme, mesial margin with comb of close-set very long setae, external face with dense field of feathery distomesially directed setae on and distal to oblique suture; epipod large, broad, anterior end strongly tapered. Second maxilliped ( Fig. 1 f) margins of both rami heavily setose, endopodal merus and propodus arcuate, flexor margin of merus with parallel long internal and more feathery external combs of long setae, internal face produced distally to form rounded lobe onto which continues internal row of close-set, very long, marginal setae, lobe extending well over internal proximal margin of short carpus; merus length about 4 times width; propodus length exceeding 2/3 merus length, longest setae originating on extensor margin, patches on distal half of external face; dactylus digitiform, length more than 2 times breadth, rounded terminally, distal half bearing short stiff cornified setae; exopod broad, bladelike, narrowing distally, distinctly overreaching endopodal merus, arcuate, terminally rounded; bilobed epipod with short, broad basal lobe, elongate narrowly tapered distal lobe. Third maxilliped ( Fig. 1 g) with very small, terminally subacute, rudimentary exopod; endopod large, setose; endopodal ischium subrectangular, maximum diagonal length at least twice width at midlength, internal face with rudimentary unarmed to finely tuberculate arched longitudinal carina on proximal 2/3; merus short, subrhomboidal, broader than long, mesial margin distinctly arcuate; carpus subrectangular, longer than broad, internal small fields of stiff setae becoming dense transverse field in distal third; propodus large, subovoid, longer than broad, internal dense field of stiff setae on proximal third, superior margin lined by long close-set setae, dense patch of more feathery setae at distal end, externally with low, setose, angular lobe on inferior margin immediately below articulation of dactylus, demarcated from margin by offset extending from marginal incision onto external face; dactylus narrow, arcuate proximally, long setae of extensor and distal margins including a few long stiff bristles at terminus.

Branchial formula as reported for congeners (Felder & Staton 2000); endopods and epipods as previously described ( Felder & Rodrigues 1993).

Major cheliped located on either right or left side, shape and dentition sexually dimorphic. Major cheliped of male ( Fig. 2 a–c; 4 c, d, e) massive, fingers heavily armed; ischium elongate, superior margin sinuous, inferior (flexor) marginal carina armed by very small denticles on proximal 2/3 to 3/4, becoming coarser distally on elevated carina, sometimes compounded or forming one or more larger teeth at distal end of elevated carina; merus superior margin weakly depressed proximally, lacking distinct notch in proximal ¼; inferior margin forming strong single keel, arcuate over distal 2/3, proximally merging into spatulate armed proximal hook at external base of keel; weak evidence (variable) of parallel secondary carina external to keel; broad distal margin of hook terminating in typically 3 (commonly 2–6) spines or teeth (most proximal of which may be lobiform or compound); external face of article distal to hook weakly tuberculate or eroded proximally (in mature); keel denticles (typically 4–8, fewer in immature) strong in distal ¾, largest on most strongly arched midsection of article (weak in immature); carpus broad, subquadrate, superior and inferior margins keeled, divergent distally, superior and inferior margins terminated distally in acutely angular comers, inferior corner origin of weak, rounded extending short distance vertically onto external face of article; propodus broad, heavy, fixed finger length exceeding 1/2 palm length (in mature); internal face of palm proximally smooth, weakly eroded (sometimes with low tubercles) in concave inferodistal region extending onto fixed finger, finely tuberculate in depression proximal to gape; broadly rounded carina extending proximally from internal prehensile margin of fixed finger below tuberculate depression behind gape and above weakly eroded inferodistal concavity of article; external face with very weak to obsolescent oblique carina or furrow defining proximal limit of slight depression extending proximally from gape, depression very weakly but densely tuberculate (or eroded); superior propodal margin distinctly keeled on proximal 3/4, inferior marginal keel distinct full length of palm, becoming broad and obscure on fixed finger where broken by large setose punctae; fixed finger originating below subtriangular, slightly upturned, heavy tooth at proximal end of gape, separated by broad U-shaped notch from strong, distally inclining, triangular tooth originating from external prehensile margin and centered at 1/3 to 2/5 length of fixed finger; fixed finger with well-defined separation of smooth internal from armed and elevated external prehensile margin, internal margin unarmed, but forming thick rounded carina extending slightly onto palm; dactylus with hooked tip, proximal end of superior marginal carina (in mature) forming erect coniform tubercle (sometimes compound) or short, strong, longitudinally oriented elevated crest, decreasing in elevation distally, carina distally broken by large setal punctae giving dentate appearance, internal dactylar face with long, strong rounded proximal carina bearing multiple smaller setal punctae, lower internal dactylus with broadly rounded carina forming unarmed internal prehensile margin of gape; dactylus external prehensile margin (in mature) typically with 3 major heavy prehensile teeth, proximal the smallest, obliquely transverse in major axis, terminally armed with rounded microtubercles, evident with dactylus fully extended, middle tooth heavy, coniform, weakly bilobed transversely, closely shouldered to proximal tooth, sparsely tuberculate on cusps, centered near 1/3 length of finger, middle tooth separated by subquadrate to U-shaped notch from narrower elongate, ridge-like distal tooth originating near midlength of dactyl, elevated proximal prominence thickest, distally sloping prehensile edge subdivided into series of strong denticles (sometimes compound) extending almost to terminal hook.

Major cheliped of female ( Fig. 2 d, Fig. 4 a) less massive, less armed and sculpted, carpus and propodus relatively lower and more elongate than in male, opposed tips of fingers forming very symmetrical pincer and gape; merus inferior margin with proximal tooth typically terminated in 2 (variably 1–3) teeth or spines and a small proximal lobe, teeth of keel usually restricted to distal half of margin; prehensile margins on fixed finger and most of dactylus evenly armed by serration of low rounded denticles; dactylus narrow, relatively less massive proximally than fixed finger, prehensile margin sinuous; fixed finger basally broader than in males, notch at base of fixed finger a narrow U-shaped or V-shaped incision proximal to serration of prehensile margin, lacking distinct development of prehensile tooth, concave between internal and external prehensile margins; superior and inferior margins of propodus convergent distally, laterally compressed to ventral keel; tip of dactylus usually overreaching tip of fixed finger when fingers crossed, flexed fingers filling gape fully including incisional notch at base of fixed finger.

Minor cheliped of male ( Fig. 2 e; Fig. 4 c, d) weakly armed; ischium flexor margin serrate by minute denticles becoming more widely separated distally; merus mostly unarmed, inferior margin with 1 small low tubercle proximally (in mature); carpus with acute distal comers, rounded carina extending vertically short distance from corner, forming subterminal blunt edge of lower external face; fixed finger slightly narrower than dactyl, broad prehensile surface unarmed but with dense field of setal punctae over full length, distal bearing short setae, sloping proximal 2/5 with punctae bearing elongate setae producing field filling about half of gape length, punctae and tufts extending somewhat onto internal face; dactylus prehensile surface with dense cover of setal punctae bearing short setae, weak evidence of subterminal tooth as broad swelling, each finger terminating in acute to subacute cornified tip. Minor cheliped of female ( Fig. 2 f) with setation on proximal prehensile face of fixed finger shorter, less dense, less elongate than in male, external prehensile margins with fine, uniform, rounded microdentition; gape between fingers narrower than in male.

Second pereopod ( Fig. 2 g) chelate, flexor margins of merus and carpus lined with evenly spaced long setae, inferior margin of propodus with long setae proximally, grading distally to dense field of shorter, variably hooked bristles; middle 1/3 of fixed finger with patch of short stiff bristles immediately external to prehensile margin; superior margin of dactylus with transverse lines and fields of proximally long setae grading to short stiff hooked bristles distally. Third pereopod ( Fig. 2 h) merus length about 3 times width; propodus with inferodistal margin variably trilobate, middle lobe smallest, sometimes no more than small cusp of weakly lobate margin between major distal and proximal lobes, setal tufts giving margins of lobes weakly scalloped appearance, lobes demarcated by furrows on internal face, lobe distal margins with dense fringe of tufted setae concealing shorter corneous bristles, distal lobe with at least one heavier, weakly hooked, distally directed corneous tooth arising from margin, longest setae on and above proximo-inferior margin of proximal lobe, patterned tufts of lighter setae on external face of article; dactylus tear-shaped, superior margin concealed by short transverse rows of long dense setae on external face, becoming thick patch of short bristles on distal superior margin, margin internally evident as distinctly sinuous, article terminating in short, narrow, ventrolaterally directed corneous tooth, external face with fields of setae and shorter stiff bristles lining inferior margin, grading to fields and poorly defined rows of much finer setae above; mature female gonopore less than 1/3 coxa length ( Fig. 2 i). Fourth pereopod ( Fig. 2 j) weakly subchelate, inferodistal process of propodus (= fixed finger) forming subacute angular lobe, tip weakly cornified, extending distally about 1/3 length of dactylus, inferior margin of lobe with 1 or more (2 in holotype) very heavy, weakly hooked, subterminal corneous spines, margin proximally with additional lighter short bristles, obscured by dense brush of setae, setae originating from inferior margin and lower internal face strongly serrate; dactylus bearing dense cover of long setae, slightly elongate, tear-shape, superior margin arched, terminating in short ventrolaterally directed corneous tooth. Fifth pereopod ( Fig. 2 k) minutely chelate, opposable faces of fingers spooned, terminally rounded with corneous, pectinate opposing margins; propodus with dense field of long, closeset setae on internal face, fixed finger slightly deflected; dactylus terminally narrower than fixed finger, hooked form of beak-like chela obscured by dense setation on distal 2/3 of propodus and superior face of dactylus.

Pleomeres dorsally smooth. First pleonal tergite ( Fig. 4 a, c, d, f) with slightly thickened, translucent, middorsal sclerite connected anterolaterally to narrowing, posteroventrally directed anterolateral sclerites, broadening posteriorly to truncate margin, lacking both isolated posterolateral sclerotized plate and small sclerites in membranous area to each side; second tergite posterolateral lobe below suture sclerotized like remainder of tergite, lobe crossed by well-defined anterior transverse line of very fine setae, 2 shorter less defined oblique lines in posterior half; ventrolateral lobe of tergite centered near or anterior to midlength of tergite. Third to fifth tergites each encompassing a finely setose, lateral, membranous suboval area below a weak posterolateral suture, those of third and fourth tergite more posteriorly positioned than on fifth, that of fifth tergite smallest, almost circular. Sixth tergite with 2 transverse posterolateral lines of short setae anterior to posterolateral groove from which transverse and posterior sutures originate, longest line adjacent, subparallel to transverse suture; transverse suture ill-defined across most of sixth tergite ( Fig. 3 j), lacking connection to short longitudinal posterior suture; posterolateral margin of tergite marked by 3 closely parallel longitudinal lines of micropunctae bearing very fine setae; tufts of stiff setae mesial to lateral incision of transverse suture, mesial to each posterior suture, on posterolateral corners, and usually as 4 short (sometimes broken) lines or tufts of stiff setae on posterior margin.

Ventral surfaces of pleomeres generally lacking extensive armor of sclerotized plates and tubercles ( Fig. 3 a; Fig. 4 b); in male, heaviest sclerites of first pleomere forming narrow furrows converging anteromesially from base of each pleopod, furrows roughly accommodating first pleopods when fully flexed against pleon; furrows on same sclerites in female forming closed suture; second pleomere in both sexes lacking evidence of neither longitudinally furrowed or flattened median plate nor thicken small sclerites forming tubercles embedded in ventral pleonal membranes.

First pleopod of male and female uniramous, composed of 2 articles; in male, first pleopod originating from outer of 2 sclerotized ridges forming trough roughly accommodating flexed pleopod, length distinctly less than 1/2 that of second pleopod, proximal article about twice length of terminal article ( Fig. 3 b–d); terminal article deeply bifurcate, slightly compressed, concave anterior margin narrower than convex margin, convex subterminal margin bearing long setae on broad distal (terminal) blade, tip ending in pair of very small, short, thick corneous spines, subterminal blade well-developed, similarly shaped to distal but shorter and less broad, tip bearing several small thin setae; in female ( Fig. 3 e), extended length of first pleopod subequal to that of second pleopod, proximal article bearing broad setose boss near midlength, slightly shorter than terminal article, terminal article forming narrow flattened blade beyond setose lobe at midlength. Second pleopod of male and female biramous, both rami setose, appendix on endopod; in mature male ( Fig. 3 f, g), appendix (representing obscure merging of appendix interna and appendix masculina in male) large, overreaching terminal lobe of endopod, long terminal setae subequal to or exceeding appendix length, overreaching both endopod and exopod; in female ( Fig. 3 h), appendix interna small, narrow, digitiform, markedly overreached by terminus of endopod. Second through fifth pleopods with, at most, a low tubercle or tooth on anterior of basis at condylar articulation with exopod. Third to fifth pleopod pairs forming large, posteriorly cupped fans when crosslinked by hooked setae of stubby appendices internae embedded in opposed margins of triangular endopods ( Fig. 3 i).

Telson ( Fig. 3 j) broad, subrectangular, width about 1.5 times length, broadest near midlength, posterior margin distinctly trilobate; dorsally with 3 pairs of strong setal tufts, posteriormost pair submedian in posterior half of telson, 2 anterior pairs aligned longitudinally well lateral of midline, both anterior to midlength; lateral margins with pair of strong setal tufts just posterior to midlength (slightly supramarginal), smaller lateral pair in anterior half (sometimes evident only as the small marginal punctae), posterior margin with well-developed tuft on each posterolateral lobe. Uropod ( Fig. 2 o) with strong, broadly triangular, posteriorly directed flange-like tooth on protopod, positioned to overreach anterior margin of extended endopod; much smaller angular short tooth on proximal article of exopod abutting margin of extended exopod; endopod elongate, narrow, subtrapezoidal, length more than twice breadth, broadest in distal half, posteromesial margin with broken fringe of setae, tapering to rounded angular terminus bearing marginal fringe of long setae, distal end extending about as far as distal end of anterodorsal plate on flexed exopod; exopod anterodorsal plate falling well short of distal margin, posterodistal edge of plate with short, thick, spiniform setae grading to thinner, dense, elongate setae of exopod margin; distal margin of exopod with dense fringe of setation, slightly longer posteriorly.

Color. In life, color in this species ( Fig. 4 a–f) is of greatly variable intensity, with the most striking individuals showing rose-pink to lavender dorsally on all sclerotized parts, including the chelipeds. When so, dorsal pigment is usually most intense on distal articles of the antennular peduncles, immediate postorbital regions of the carapace, posterior reaches of the pleomeres, basal articles of the uropods, and lateral reaches of the telson. However, some (very young and very old) individuals may totally or almost totally lack rose-pink and instead show off white sclerotized areas and chromatophores or dispersed color of brownish yellow to olive green hues, such as are commonly found on the uropodal exopods and ventral surfaces of many specimens.

Size. Maximum observed postorbital carapace length of male 19.2 mm; of female 18.7 mm. Maximum embryonated egg length on preserved ovigerous females is about 0.8 mm for immature clutches and 0.9–1.0 mm for immediate pre-hatch.

Habitat. Obligate fossorial burrowers as adults, populations of this species favor polyhaline habitats with richly organic sediments, as appears true for most species of the genus ( Felder 2001). All specimens in natural settings of coastal Nicaragua were taken with hand-operated extraction “yabby” pumps from intertidal to shallow subtidal sediments on margins and mudflats of mangrove-lined estuaries or back-beach ephemeral ponds. However, exceptionally dense populations also occurred on the bottoms (<2 m deep) and margins of clayey to silty commercial penaeid shrimp culture ponds in Tumaco, Colombia, the type locality. As in other cases where Lepidophthalmus invades such culture ponds ( Nates & Felder 1998), these ponds were constructed on estuaries that provided optimal habitat for the members of the genus and thus populations from which larvae are recruited when ponds are filled. Burrow walls appeared to be constructed of lightly cemented clayey sand or mud, with the internal lining usually a smoother brownish surface. In all settings, sediments appeared to be richly organic, often with an identifiable detrital component. Salinities of shallow waters overlying burrows ranged from 2.0 psu in a rainswollen tidal stream of a small estuary to 45.0 psu in a shallow pond stranded among mangroves inside an ephemeral inlet. In most Nicaraguan collecting sites, this species occurred alongside the congeners L. eiseni and L. bocourti , with no detectable microhabitat separation of the three species within the habitat. Where found on mudflats near mangroves, burrows of two burrowing axianassids, Axianassa spp., occurred among those of Lepidophthalmus . Commensal alpheid shrimp of the genus Leptalpheus , as reported by Anker (2011), occurred with all of these species but were in some cases unquestionably extracted from burrows of L. natesi sp. nov.

Distribution. Eastern Pacific: Extreme southern Colombia to northwestern Nicaragua (polyhaline waters along estuary margins, mudflats of inlets, ephemeral intertidal ponds, tidal streams).

Type locality. Pacific coast of Colombia, Tumaco, bottom of partially drained commercial shrimp culture pond in mangrove estuary (01°46.64'N, 78°46.30'W).

Etymology. This species is named for our colleague Dr. Sergio F. Nates , who was for several years a participating scientist in our field and lab projects concerning biology of callianassid shrimp in Nicaragua, Costa Rica, Panama, and Colombia, and who assisted in the collection of many specimens essential to this and related papers.

Remarks. L. natesi sp. nov. reaches relatively large size and has relatively small eggs compared to some species of the genus but does not appear to reach the size extremes of larger specimens among sympatric populations of the ventrally sclerotized species L. eiseni and L. bocourti . Occurring together, these two species can look superficially very similar, to the point that some earlier authors ( Biffar 1972; Manning & Felder 1991; Sakai 1999, 2005), treated them as synonyms. Even after reestablishment of their well-supported separation (Felder 2003), the account of Sakai (2005) continued to confuse the characters that so clearly separate them. At first inspection, both of these ventrally plated species resemble L. natesi sp. nov., which is in turn readily distinguished from both of them by its lacking the ventral median sclerotized plate on the second pleomere. Lifting the second pleopods to expose the ventral surface, this large plate is subrectangular in L. eiseni or conspicuously constricted along its length in L. bocourti . Of the two plated species, L. bocourti also differs from both L. eiseni and L. natesi sp. nov. in having a uniquely reflexed ventrolateral cristate margin on the second pleuron and distinct spines developed on the anterior of the basipodites of the third through fifth pleopods (Felder 2003). Yet, despite its unique features, sequence-based phylogenetic analyses (Felder et al. 2003, Felder & Robles, 2015) position L. bocourti as a closer relative to L. natesi nov. sp. than to any other congener to which it has thus far been compared by molecular methods.

Comparative molecular analyses to date have not, however, included L. rafai Felder & Manning, 1998 , and this is the only other presently described eastern Pacific species of the genus that lacks ventral pleonal sclerites. Thus far known only from the type series of small specimens taken in western Colombia, those perhaps typifying its apparently smaller size than L. natesi sp. nov., L. rafai would not appear to be a close relative of the presently described species because of its lacking a trilobate posterior margin on the telson and having a broad uropodal endopod. In addition to these fundamental differences, it differs in many other likely more apomorphic characters, from shape of the third maxilliped merus, to the distinctly bicarinate keel of the male cheliped merus, shape of the proximal meral hook on this cheliped, and dimunitive appendix on the second male pleopod. In most of its characters, including its telson and uropods, L. rafai continues to be a candidate instead for relationship to the ventrally unsclerotized L. louisianensis or L. siriboia from the western Atlantic, as previously suggested ( Felder & Manning 1998), rather than to L. natesi sp. nov.

If accepting genetic inference that relates L. natesi sp. nov. closely to L. bocourti , it follows that presence or absence of ventral pleonal sclerites must then vary within clades of the generic phylogeny. Such plating remains a character of utility for species identification, but perhaps not always one easily applied in slightly higher classification. Other than the trilobate posterior margin of the telson and shape of the adjacent somewhat trapezoical uropodal endopods, these two species do share other characters, notably including configuration of the almost identical dorsal sclerite and surrounding posterolateral membrane on the first pleomere. In both, there is lack of an isolated large sclerite or small dispersed sclerites within the posterolateral membrane (Fig. a, c, d, f; Felder 2003: fig. 17), despite these occurring in many congeners ( Felder & Manning 1997: fig. 1 d, 7 a: Felder 2003: fig. 26; Felder & Staton 2000: 1 h). Males of these two species also share similar development of the major cheliped, from the multispinose or multidentate proximal meral hook to dentition of the fingers ( Fig. 2 a, b, 4 e; Felder 2003: fig. 13) and similar development of the second pleopodal appendices.

As in most species of the genus that range from large to small sizes in collections, there is wide variation in character development among less than fully mature specimens, as well as between average-sized mature specimens and the occasional exceptionally large individual. Submature male chelipeds may have very little of the dentition and other appendage armor developed ( Fig. 2 a–c), and secondary sex characters of the pleopods, including the appendix of the second, also vary with maturation ( Fig. 3 c, b, d, f, g). In very large males, the rostrum is sometimes directed steeply upward over the eyes, rather than gently arched, its steep inflection reflected in some depression of the carapace front that more strongly offsets it from the dorsal oval than in typical specimens. In mature females, the rostrum is alternatively sometimes barely arched or elevated and very narrowly spiniform, extending almost as far anteriorly as the eyestalks. The eyestalks themselves can vary in acuteness of the tip and angularity of the anterolateral corner, being less acute terminally and more angular anterolaterally in large males, and more acute and less angular in females. This at times makes the male eyestalks appear shorter and broader than in females.

Figures

FIGURE 1. Lepidophthalmus natesi sp. nov., holotype male, cl 16.7 mm, Tumaco, Pacific coast of Colombia (USNM 1275006): a, anterior carapace, dorsal; b, right mandible, external; c, right first maxilla, without setae, external; d, right second maxilla, without setae, external; e, right first maxilliped, external; f, right second maxilliped, external; g, right third maxilliped, external. Scale bars = 2.0 mm (a, c – f), 1.0 mm (b).

FIGURE 2. Lepidophthalmus natesi sp. nov.; a, b, e, g, h, j, k, holotype male, cl 16.7 mm, Tumaco, Pacific coast of Colombia (USNM 1275006); c, paratype male, cl 5.9 mm, Tumaco, Pacific coast of Colombia (USNM 1275007); d, f, paratype female, cl 15.5 mm, Tumaco, Pacific coast of Colombia (USNM 1275008); i, paratype ovigerous female, cl 13.8 mm, Paso de Caballos, Pacific coast of Nicaragua (ULLZ 11828): a, major (right) male cheliped, b, external; major right male cheliped, internal; c, major (left) male cheliped, external; d, major (left) female cheliped, external; e, minor (left) male cheliped, internal; f, minor (right) female cheliped, external; g, right second pereopod, external; h, right third pereopod, external; i, right third pereopod coxae and gonopores, ventral; j, right fourth pereopod, external; k, right fifth pereopod, antero-internal. Scale bars = 5.0 mm (ah, j, k), 3.5 mm (i).

FIGURE 3. Lepidophthalmus natesi sp. nov.; a, b, f, i, holotype male, cl 16.7 mm, Tumaco, Pacific coast of Colombia (USNM 1275008); c, paratype male, cl 11.0 mm, d, g, paratype male, cl 5.9 mm, Tumaco, Pacific coast of Colombia (USNM 1275007); e, h, j, paratype female, cl 15.5 mm, Tumaco, Pacific coast of Colombia (USNM 1275008): a, anterior pleomeres of male, left pleopods removed, ventral; b, right male first pleopod, lateral; c, right male first pleopod, lateral; d, right male first pleopod, lateral; e, right female first pleopod, lateral; f, right male second pleopod, posterior; g, right male second pleopod, posterior; h, right female second pleopod, posterior; i, right third pleopod, anterior; j, telson and uropods, dorsal. Scale bars = 5.0 mm (a, i, j), 2.0 mm (b), 1.0 mm (c, g), 4.0 mm (f), 0.5 mm (d), 2.0 mm (e, h).

FIGURE 4. Color patterns and habitus of Lepidophthalmus natesi sp. nov.: a, f, female paratype, lateral habitus (a) and dorsal sclerite of first pleomere (b, contrast enhanced), cl 12.7 mm, Estero de Las Peñitas, Pacific coast of Nicaragua (ULLZ 4509); b, e, male paratype, ventral with second pleopods removed (b), and external face of cheliped (e), cl 15.5 mm, Estero de Las Peñitas, Pacific coast of Nicaragua (ULLZ 4509); c, d, male paratype, lateral habitus (c) and dorsal habitus (d), cl 16.6 mm, Estero Ciego, Pacific coast of Nicaragua (ULLZ 10838).