Pontonia panamica, Marin & Anker, 2008

Marin, Ivan & Anker, Arthur, 2008, A new species of Pontonia Latreille, 1829 (Crustacea, Decapoda, Palaemonidae) associated with sea squirts (Tunicata, Ascidiacea) from the Pacific coast of Panama, Zoosystema 30 (2), pp. 501-515 : 503-512

Pontonia panamica n. sp.

( Figs 1-7 )

TYPE MATERIAL. — Holotype: Panama, Playa Venao, 10 km west of Panama City, lower rocky intertidal, silty sand with large rocks, in ascidian, Ascidia cf. interrupta , attached under rocks, close to water-line at low tide, coll. I. Marin, 18.IV.2007, 1 ovig. ♀, pcl 5.5 mm (MNHN- Na 16392). Allotype: same data as holotype, 1 ♂, pcl 7.4 mm (MNHN-Na 16393).

Paratypes: Panama, Playa Venao , 10 km west of Panama City, lower rocky intertidal, silty sand with large rocks, in ascidians, Ascidia cf. interrupta , attached under rocks, close to water-line at low tide, coll. I. Marin and A. Baeza, 20.IV.2007, 1 ovig. ♀, pcl 6.0 mm, 1 ♂, pcl 4.8 mm [dissected] (MNHN-Na 16394) ; 1 ovig. ♀, pcl 7.5 mm, 1 ♂, pcl 6.0 mm ( USNM 1103080 ) ; 1 ovig. ♀, pcl 5.2 mm, 1 ♂, pcl 4.9 mm ( OUMNH-ZC 2007-13 - 030 ) ; 1 ovig. ♀, pcl 7.6 mm, 1 ♂, pcl 5.4 mm ( OUMNH-ZC 2007-13 - 030 ) ; 1 ovig. ♀, pcl 6.7 mm, 1 ♂, pcl 5.4 mm ( USNM 1103082 ) ; 1 ovig. ♀, pcl 6.5 mm, 1 ♂, pcl 4.2 mm ( RMNH D 51824) ; 1 ovig. ♀, pcl 7.5 mm, 1 ♂, pcl 4.2 mm ( RMNH D 51825 ) ; 1 ovig. ♀, pcl 7.2 mm, 1 ♂, pcl 4.7 mm ( UP) .

ETYMOLOGY. — The new species is named after the country of the type locality, Panama.

TYPE LOCALITY. — Playa Venao, Pacific coast of Panama.

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

DESCRIPTION (based on female holotype) Large-sized pontoniine shrimp with depressed, somewhat expanded body ( Fig. 7 ). Carapace swollen, smooth, with well-developed acute antennal tooth. Rostrum ( Fig. 1 A-D) long and slender, reaching to midlength of second segment of antennular peduncle, with slightly marked lateral carina and ventral carina distally; tip ( Fig. 1 E-G) with small subdistal tooth and two long smooth setae dorsally, without distinct subdistal tooth ventrally.

Abdominal somites (pleomeres) smooth; tergites non-carinate, not posteriorly produced; pleura of first to fifth pleomere posteroventrally rounded. Telson ( Fig. 2C, G, F ) about twice as long as wide proximally, tapering distally, with two pairs of stout dorsal spines, each about 0.3 telson length, inserted at about 0.4 and 0.6 telson length, respectively; posterior margin broadly rounded, with three pairs of relatively long, slender spines, intermediate spines longest ( Fig. 2D ).

Eyes fairly large, with rounded cornea; basal portion of eyestalks exposed.

Antennules ( Fig. 2A ) with first peduncular segment about twice as long as maximum width, with small ventromesial tooth and well-defined acute distolateral tooth; lateral margin distinctly convex; stylocerite distally acute, reaching to about 0.3 of first segment; second and third segments stout, unarmed, rectangular; lateral flagellum thick, main ramus with six segments, accessory ramus with one segment; mesial flagellum filiform, with more than 30 segments. Antenna ( Fig. 2B ) with distolateral margin of basicerite unarmed; scaphocerite subrectangular, slightly exceeding antennular peduncle, twice as long as maximum width; distal margin of blade protruding, forming blunt angle; distolateral tooth well-developed, not exceeding blade; carpocerite reaching about 0.7 length of scaphocerite.

Epistome with blunt medial carina; labrum oval. Paragnath ( Fig. 3I ) well-developed, alae with large subcircular distal lobes and small ovate ventromedial lobes; corpus with medial groove bordered by parallel submedial setose carina.

Mandible ( Fig. 3A ) without palp; incisor process slender, not tapering distally, with four large stout subtriangular teeth distally and row of minute teeth along distolateral margin ( Fig. 3B ); molar process well-developed, stout. Maxillule ( Fig. 3C ) with well-developed, bilobed palp, dorsal lobe of palp proximally excavated, ventral lobe with short, distally curved seta ( Fig. 3D ); ventral lacinia significantly larger than dorsal lacinia, broadened, with simple setae distoventrally and marginally; dorsal lacinia broad, distally rounded and with serrulate spines and numerous simple setae. Maxilla ( Fig. 3E ) with well-developed, distally tapering, simple palp; basal endite simple, distally rounded, furnished with stiff, elongated setae; coxal endite well-developed, distally rounded, furnished with long simple setae; scaphognathite moderately broad. First maxilliped ( Fig. 3F ) with completely fused basal and coxal endites; palp slender, pointed distally, without distal setae; exopod with expanded caridean lobe; epipod oval. Second maxilliped ( Fig. 3G ) with slender proximal segments; distolateral margin of propodus broadly rounded, with slender setae; dactylus about three times as long as broad, with numerous spines along distal margin; exopod and epipod well-developed, latter oval-shaped; podobranch absent. Third maxilliped ( Fig. 3H ) relatively stout; coxa with rounded epipod; antepenultimate segment stout, basis and ischiomerus clearly separated by oblique suture; penultimate segment with convex mesioventral margin, about three times as long as wide; ultimate segment markedly more slender than penultimate segment, about three times as long as wide, tapering distally; exopod reaching almost midlength of penultimate segment; arthrobranch absent.

First pereiopod ( Fig. 4A ) slender, segments unarmed; basis about 1.5 times as long as wide; ischium about three times as long as wide; merus slender, about four times as long as wide, with simple setae along mesiolateral margin; carpus slender, widening distally, slightly longer than merus, six times as long as distal width; palm about twice as long as wide, subcylindrical in cross-section; fingers subcylindrical, slender, about four times as long as wide proximally, with simple tips and straight cutting edges.

Second pereiopods (chelipeds) unequal in size, subsymmetrical in shape ( Fig. 6 ). Major cheliped ( Fig. 4B ) with rectangular basis; ischium about twice as long as maximum width; merus stout, about 1.5 times as long as maximum width; carpus about 1.8 times as long as maximum width, rounded distally; palm subcylindrical, about twice as long as maximum width, fingers robust, about 2.5 times length of palm; pollex ( Fig. 4C ) robust, tapering, about 1.3 times as long as wide, with two large triangular teeth in proximal half; tip acute, curved; dactylus subcylindrical, curved, with well-marked cutting edge bearing large triangular tooth near midlength, tip acute, curved. Minor cheliped ( Fig. 4D ) with rectangular basis; ischium about three times as long as maximum width; merus stout, about twice as long as maximum width; carpus relatively slender, about 2.5 times as long as maximum width, rounded distally; palm flattened, about twice as long as wide, fingers slender, subequal to palm length; pollex ( Fig. 4E ) slender, about three times as long as wide, cutting edge well-defined, proximally with finely serrated (distal margin with about seven minute acute denticles) tooth, followed by small rounded hiatus; tip acute, curved; dactylus ( Fig. 4E ) with well-defined cutting edge bearing one medium-sized,simple tooth at about proximal 0.3 dactylus length.

Third pereiopod ( Fig. 4F ) relatively stout; basis rectangular; ischium about 2.5 as long as wide; merus about three times as long as wide; carpus about half as long as merus, about three times as long as wide, with slightly projecting distodorsal margin; propodus four times as long as wide, distally with numerous simple setae and three small distoventral spines; dactylus ( Fig.6A ) biunguiculate, about three times as long as wide, with numerous simple, proximally curved setae on distal and ventral margins; accessory unguis well-developed, simple, acute; main unguis slender, smooth, acute. Fourth and fifth pereiopods similar to third.

Pleopods without specific features. Uropods ( Fig. 2C ) exceeding telson; lateral margin of uropodal exopod with small distolateral spine but without distolateral tooth.

Male allotype smaller in size, more slender ( Fig. 7 ), with distinctly longer, more robust, more markedly unequal and asymmetrical chelipeds ( Figs 5A, C ; 7 ); major cheliped ( Fig. 5A, B ) with relatively longer palm, about 3.5 times as long as wide, with fingers about 0.4 times palm length; minor cheliped ( Fig. 5C, D ) similar to that of female; endopod of first pleopod fringed with setae along margins, including one subdistal seta ( Fig. 6D ); endopod of second pleopod ( Fig. 6B ) with well-developed appendix interna and appendix masculina, latter furnished with at least six slender setae distally and one subdistal seta ( Fig. 6C ).

VARIATION

In one female paratype, the ventral margin of the rostrum presents a minute notch subdistally, however no distinct tooth ( Fig. 1F ). The typical position of dorsal spines on the telson is illustrated in Figure 2G, F ; in one paratype ( Fig. 2C ), the posterior pair is situated slightly more posteriorly.

COLOUR PATTERN

Semitransparent, with numerous white stripes and patches arranged in complex pattern, latter more defined on abdomen, tail fan, antennules, antennae, walking legs and chelipeds, especially in males; females appearing more yellowish due to brown gonads and/or eggs ( Fig. 7 ).

SIZE

Pcl ranges from 5.2 to 7.6 mm in females, and from 4.2 to 6.0 mm in males.The female holotype and the male allotype are among the largest specimens in the type series, with a tbl of approximately 22 and 18 mm, respectively.The largest female(pcl 7.6 mm,OUMNH) has approximately 1430eggs,with an average diameter of 0.5 × 0.4 mm (measured on 10 eggs).

ECOLOGY

Playa Venao, the type locality of Pontonia panamica n. sp., is a typical tropical eastern Pacific rocky shore composed of large silt-covered rocks lying densely on silty sand mixed with smaller rocks, mud, shells, etc. The intertidal portion of this rocky shore is exposed for at least 200 m from the beach seawards during extreme low tides (January to April). All shrimps were found in the lower intertidal section, close to the water-line ( Fig. 8A ). They were dwelling inside colourless or slightly yellowish, leathery ascidians, Ascidia cf. interrupta Heller,1878 (Ascidiidae) ,attached underneath large rocks partly immerged in muddy sand ( Fig. 8C ). The ascidians were completely submerged in muddy water, with only their long siphons being occasionally visible between rocks. They filter surrounding mud-filled water as their stomachs were filled with muddy substance. Shrimps were always found as heterosexual pairs, and only inside larger hosts, i.e., with body volume more than 45-50 ml.

HOST

Ascidia interrupta is currently believed to occur on the coasts of both the eastern Pacific and western Atlantic (F. Monniot pers. comm.). However, in Bocas del Toro, Caribbean coast of Panama, A. interrupta appears to occur in aggregations on mangrove roots and has green or greenish-yellow siphons (Collin et al. 2005), whereas our individuals from Playa Venao, Pacific coast of Panama (hosts of P.panamica n. sp.), occur individually beneath intertidal rocks and have inconspicuously brownish siphons. These differences in colour and ecology may indicate presence of transisthmian cryptic taxa.

Figures

FIG. 1. — Pontonia panamica n. sp.: A, B, anterior part of carapace,dorsal view; C, D, anterior part of carapace,lateral view;E-G, distal rostrum; A, E, ♀ holotype, pcl 7.4 mm (MNHN-Na 16392); B, ♂ allotype,pcl 5.5 mm (MNHN-Na 16393); C, F, ♀ paratype, pcl 6.0 mm (MNHN-Na 16394); D, G, ♂ paratype, pcl 4.8 mm (MNHN-Na 16394). Scale bars: 1 mm.

FIG. 2. — Pontonia panamica n.sp.: A, antennule,ventral view;B, antenna,ventral view;C, telson and uropods,dorsal view;D, posterior margin of telson, dorsal view; E, distolateral margin of uropodal exopod, dorsal view; F, G, telson, dorsal view; A-E, ♀ paratype, pcl 6.0 mm (MNHN-Na 16394); F, ♂ paratype, pcl 4.8 mm (MNHN-Na 16394); G, ♀ paratype, pcl 6.0 mm (USNM 1103080). Scale bars: 1 mm.

FIG. 3. — Pontonia panamica n. sp., ♀ paratype,pcl 6.0 mm (MNHN-Na 16394): A-H, lateral view; A, mandible; B, same, distal margin of incisor process; C, maxillule;D, same, distal margin of palp; E, maxilla;F, first maxilliped; G, second maxilliped; H, third maxilliped; I, paragnath, ventral view. Scale bars: 1 mm.

FIG. 4. — Pontonia panamica n. sp., ♀ paratype, pcl 6.0 mm (MNHN-Na 16394): A, right first pereiopod, lateral view; B, left second pereiopod, major cheliped,mesial view; C, same, distal chela; D, right second pereiopod,minor cheliped,mesial view;E, same, distal chela; G, left third pereiopod, mesial view. Scale bars: 1 mm.

FIG. 5. — Pontonia panamica n. sp., ♂ paratype, pcl 4.8 mm (MNHN-Na 16394):A, left second pereiopod,major cheliped,mesial view; B, same, distal chela; C, right second pereiopod, minor cheliped, mesial view; D, same, distal chela. Scale bars: 1 mm.

FIG. 6. — Pontonia panamica n. sp.,♂ paratype,pcl 4.8 mm (MNHN-Na 16394):A, third pereiopod dactylus;B, second pleopod,lateral view; C, same, detail of appendix masculina; D, endopod of first pleopod, mesial view. Scale bars: A, D, 0.1 mm; B, 0.3 mm.

FIG. 7. — Pontonia panamica n. sp., general habitus and colour pattern: A, ♀ holotype, pcl 7.4 mm (MNHN-Na 16392); B, ♂ allotype, pcl 5.5 mm (MNHN-Na 16393).

FIG. 8. — Playa Venao,Pacific coast of Panama,type locality of Pontonia panamica n. sp.: A, general view of rocky intertidal at extreme low tide (arrow indicating exact location where specimens were collected); B, rocks close to water-line,partly immerged in sand-mud, where ascidians hosting shrimps where found; C, two solitary ascidians, Ascidia cf. interrupta Heller, 1878 (white arrows), hosts of P. panamica n. sp., attached to the lower surface of an overturned rock.