Lacertopontonia chadi, Marin, Ivan, 2011

Marin, Ivan, 2011, Lacertopontonia chadi gen. et sp. nov., a new oyster-associated Pontonia - like pontoniine shrimp (Crustacea, Decapoda, Palaemonidae) from the Great Barrier Reef of Australia, Zootaxa 2968, pp. 57-68 : 59-67

Lacertopontonia chadi sp. nov.

( Figs. 1 –7)

Material examined. Holotype, ovigerous female (QM W33473) – Australia, GBR, Lizard Island, lagoon, Channel, st. LI10-022, 14° 41.435 S 145° 27.912 E, 14–15 meters depth, in wash-out from bivalve Lopha cristagalli growing on sea whip, coll. Chad Buxton, 28 Aug. 2010. Paratypes, 1 ovigerous females and 1 male ( RMNH) – same data and host as for holotype.

Description. Female. Medium-sized pontoniine shrimp with smooth swollen body ( Fig. 1 ). Carapace smooth, swollen, subcylindrical, without antennal and hepatic teeth, with inferior orbital angle acutely produced, turned downward (Fig. 2 b). Rostrum (Fig. 2 a–e) robust, deep, unarmed, distally rounded and turned downward, reaching midlenght of basal antennular segment, with ventral carina well developed, forming distinct keel (Fig. 2 c, e).

Abdominal somites smooth, unarmed; tergites non-carinate, not posteriorly produced; pleurae of first to third abdominal pleomeres posteroventrally rounded; three last abdominal pleomeres small bearing feebly developed pleurae ( Fig. 1 ); ventral margin of the sixth pleomere bluntly rounded. Telson (Figs. 2 f, 3 d, e) stout, dorsally smooth, about twice as long as proximal width, tapering distally, with three pairs of relatively large submarginal dorsal spines, each about 0.12 of telson length, inserted at about 0.15, 0.5 and 0.85 of the telson length, respectively (Figs. 2 f, 3 d, e); posterior margin bluntly rounded, armed with two pair of posterior spines, lateral posterior spines about half length of medial ones.

Eyes (Fig. 2 a–e) large, swollen and smooth; cornea rounded, well developed and well pigmented; eyestalk stout, swollen, cylindrical, about as long as wide.

Antennula and antennae slightly reduced (Fig. 2 a–e). Antennula (Fig. 3 a) stout, basal peduncular segment robust, about as long as its proximal width, with straight lateral margins, with well developed ventromedial tooth (Fig. 3 b) and broad sharp triangular distolateral tooth (Fig. 3 a), stylocerite stout, bluntly rounded distally, reaching the midlenght of basal segment; second antennular segment stout, about 1.5 times longer than wide; the third (distal) segment stout, unarmed, about as long as wide; lateral flagellum thick, main ramus with five separate segments, accessory ramus with two segment; medial flagellum filiform, with 8–9 segments. Antenna (Fig. 3 c) with stout basicerite, about 1.5 times wider than long, with distolateral margin unarmed; carpocerite robust, slightly overreaching scaphocerite, about five times longer than wide; scaphocerite with well developed blade, with large acute distolateral tooth separated from the blade with a deep notch (Fig. 3 c).

Epistome with blunt median carina; labrum suboval (Fig. 4 a). Mandible (Fig. 4 b) well developed, without palp; molar process well-developed, stout; incisor process slender, tapering distally, with five triangular distal teeth. Maxillula (Fig. 4 c) with well-developed stout bilobed palp, dorsal lobe blunt, ventral lobe with small curved spine; dorsal lacinia broad, expanded distally, distal margin bluntly rounded, covered with row of small stout spines and numerous simple setae; ventral lacinia slender, reaching distal margin of dorsal lacinia, with long simple setae distoventrally and marginally. Maxilla (Fig. 4 d) normal, with simple palp tapering distally; with single simple distally bluntly rounded endite furnished with styliform elongated setae along its lateral margin; coxal endite feebly developed; scaphognathite broad, furnished with short plumose setae. Maxilliped I (Fig. 4 e) normal; epipod earshaped, with distinct medial notch; exopod slender, with expanded caridean lobe; basal and coxal endites completely fused, furnished with numerous long simple setae distally; palp slender, rounded distally. Maxilliped II (Fig.

FIGURE 2. Lacertopontonia chadi gen. et sp. nov., ovigerous paratype female (a–c, f) and paratype male (d, e) (RMNH): a, b, d —front of carapace, lateral view; c, e —front of carapace, dorsal view; f —telson.

FIGURE 3. Lacertopontonia chadi gen. et sp. nov., ovigerous holotype female (d) (QM W33473) and ovigerous paratype female (a–c, e, f) (RMNH): a —antennula, dorsal view; b —antennula, lateral view; c —antenna; d —telson and uropods; e —telson; f —distolateral margin of uropodal exopod.

FIGURE 4. Lacertopontonia chadi gen. et sp. nov., ovigerous paratype female (RMNH): a —labrum; b —mandible; c —maxillula; d —maxilla; e —maxilliped I; f —maxilliped II; g —maxilliped III.

FIGURE 5. Lacertopontonia chadi gen. et sp. nov., ovigerous paratype female (RMNH): a —pereiopod I; b —chela of pereiopod I; c —pereiopod II; d, e —chela of pereiopod II; f —pereiopod III; g —dactylus of pereiopod III.

FIGURE 6. Lacertopontonia chadi gen. et sp. nov., ovigerous paratype female (b), paratype male (a, c–f) (RMNH X): a —general dorsal view of paratype male; b, c, d —fingers of major pereiopod II; e, f —fingers of minor pereiopod II.

FIGURE 7. Coloration of Lacertopontonia chadi gen. et sp. nov., holotype, ovigerous female (b, c) (QM W33473), ovigerous paratype female (a) and paratype male (d) (RMNH). Male was photographed shortly after death.

4 f) with robust segments; epipod normal, rounded; exopod slender reaching the propodal segment, with numerous long simple setae distally; distolateral margin of propodus broadly rounded, dorsal margin convex, furnished with slender setae; dactylus about three times as long as broad, with numerous medium stout spines and numerous simple setae along distal margin. Maxilliped III (Fig. 4 g) stout; with quadrate epipod, without arthrobranch; exopod slender, slightly overreaching antepenultimate segment, with numerous long simple setae distally; antepenultimate segment stout, broadened, about twice longer than wide; penultimate segment about 2.5 times as long as wide, with straight margins; ultimate segment slender, slightly shorter than penultimate segment, about twice longer than wide, tapering distally, with tufts of long setae along ventrolateral margin, with several long setae distally.

Pereiopod I (Fig. 5 a) relatively slender, with smooth, unarmed segments; coxa with well marked rounded distoventral lobe; basis about as long as wide; ischium about twice times as long as wide; merus slender, about five times as long as wide, with straight ventral and dorsal margins; carpus long and slender, widening distally, about six times as long as maximal width, slightly longer than merus, about twice as long as chela; palm (Fig. 5 b) about twice as long as wide, subcylindrical in cross-section; fingers slender, subcylindrical, about four times as long as proximal width, equal to palm, with simple tips and straight cutting edges.

Pereiopods II with smooth unarmed segments, equal in size, similar in shape in females ( Figs. 1 , 5 c, 7) and slightly unequal in size in males (Fig. 7); basis rectangular, as long as wide; ischium widening distally, about 1.7 times as long as maximum width; merus relatively stout, about twice longer than maximum width, with straight ventral and dorsal margins; carpus stout, swollen, slightly widening distally, about 1.5 times as long as maximum width; palm (Fig. 5 c–e) subcylindrical in cross-section, slightly widening proximally, about twice longer than proximal width; fingers robust, about 1.5 times shorter than palm, about three times as long as wide, fixed finger (pollex) with two triangular acute teeth in proximomedial part, movable finger with small triangular tooth on medial part in females (Figs. 5 d, e, 6 b) and with large semicircular tooth on medial part in males (Fig. 6 c–f), with acute curved simple tips.

Pereiopods III – V similar in size and shape. Pereiopod III (Fig. 5 f) with stout smooth segments; coxa and basis about as long as wide; ischium about 2.5 times as long as wide; merus about three times as long as wide, with straight ventral and dorsal margins; carpus stout, widening distally, about half of the length of merus and propodus, about 3.5 times as long as wide, with bluntly projecting distodorsal margin slightly overlapping carpo-propodal articulation; propodus relatively robust, about 4.5 times as long as wide, with straight lateral margins, ventrally unarmed, without distoventral teeth, distal part of propodus covered with numerous short simple setae; dactylus (Fig. 5 g) simple, robust, about 2.5 times as long as wide, covered with small short simple setae, unguis short robust and curved.

Pleopods smooth, normal, without specific features. Uropods stout, smooth, not exceeding telson, exopod about 0.6 of endopod length (Fig. 3 d); lateral margin of uropodal exopod straight, with bluntly rounded distolateral angle, without movable distolateral spine or fixed distolateral tooth (Fig. 3 f); with simple diaeresis.

Male. Generally similar to female but smaller in size. Pereiopods II large and slightly dissimilar, with well developed teeth on fingers (Fig. 6), larger than in females (Fig. 7 a, d). Endopod of pleopod II in males with short appendix masculine, about 1.5 times shorter than appendix interna, without specific features, covered with numerous setose setae.

Coloration. Generally semi-translucent; body and appendages creamy-whitish covered with tiny white dots; cornea of eyes bright silver; gonads and eggs orange-red (Fig. 7).

Measurements. Relatively large pontoniine shrimp species. Holotype, ovigerous female – pcl. 6.0 mm, tl. 20 mm; paratypes, ovigerous female – pcl. 5.0 mm, tl. 19 mm and male – pcl. 4.0 mm, tl. 12 mm.

Etymology. The species is named after Chad Buxton (Museum of tropical Queensland, Townsville, Australia), the collector of the type specimens of this interesting shrimp.

Host. All examined specimens of Lacertopontonia chadi sp. nov. were collected from washout of a cluster of cockscomb oyster Lopha cristagalli (Linnaeus, 1758) (Bivalvia, Ostreidae ) growing on sea whip Cirripathes sp (Anthipatharia, Anthipathidae). The cluster consisted of seven large and several small shells connected by their bases to the sea whip. Several mature specimens of pontoniine shrimp Anchistus sp. (Crustacea, Decapoda , Palaemonidae ), probably belonging to an undescribed species, were also found in the same washout.

Distribution. Presently only known from the type locality, Lizard Island, GBR, Australia.

Figures

FIGURE 1. Lacertopontonia chadi gen. et sp. nov., holotype, ovigerous female (QM W 33473), general view. Scale— 1 mm.