Odontonia bagginsi, Gier, Werner de & Fransen, Charles H. J. M., 2018

Gier, Werner de & Fransen, Charles H. J. M., 2018, Odontoniaplurellicola sp. n. and Odontoniabagginsi sp. n., two new ascidian-associated shrimp from Ternate and Tidore, Indonesia, with a phylogenetic reconstruction of the genus (Crustacea, Decapoda, Palaemonidae), ZooKeys 765, pp. 123-160 : 123

Odontonia bagginsi sp. n. Figs 8, 9, 10, 11, 12, 13, 14, 15E, 16A, 17A

Material examined.

(i) Indo-West Pacific: Indonesia. -1 ovigerous female (holotype) PoCL 3.4 mm (MZB Cru 4733, ex RMNH.CRUS.D.53559), N of Desa Rum, Tidore, Ternate, Indonesia, 0°44'35.8"N 127°23'6.3"E, 27 m depth, scuba diving, reef consisting primarily of boulders and soft corals; 4-11-2009; in solitary ascidian (Asc. 67), leg. A. Gittenberger, photo TER.17.0136-39.

Diagnosis. Rostrum as long as antennular peduncle, with strong distoventral tooth. Pterygostomial angle broadly rounded, produced. Basal segment of antennular peduncle with strong, acute medioventral tooth. Distolateral tooth of scaphocerite robust, 0.4 length of lamina. Dactylus of ambulatory pereiopods with blunt accessory tooth, perpendicular to flexor margin; flexor margin of corpus with strong, acute forward directed proximal tooth and two small denticles between this tooth and accessory tooth; unguis without terminal scales. Telson with two pairs of medium sized (0.13 of telson length) submarginal dorsal spines at 0.15 and 0.48 of telson length.

Description. Body (Figs 8, 15E) subcylindrical, depressed. Carapace smooth. Rostrum well developed, 0.38 of post-orbital carapace length, without dorsal teeth, as long as antennular peduncle, reaching distal margin of scaphocerite, approximately 2.6 times longer than diameter of hemispherical cornea, with broad shallow indistinct dorsal carina, with acute lateral carinae, with straight ventral carina; with strong distal ventral tooth just extending beyond apex, with few distal setae, bluntly acute in dorsal view, broadened at base. Inferior orbital angle not produced, straight. Antennal spine reduced to blunt protruding process, not separated by notch from inferior orbital angle. Pterygostomial angle of carapace strongly produced, rounded.

Abdomen smooth, sixth segment 1.3 times longer than fifth, 1.4 times wider than long, posterolateral angle blunt, slightly produced, posteroventral angle blunt, not produced; pleura of first five segments broadly rounded.

Telson (Fig. 10 A–B) 1.8 times as long as sixth abdominal segment, 2.0 times longer than proximal width; lateral margins almost straight, slightly convex; posterior border without median process; two pairs of medium-sized submarginal dorsal spines at 0.15 and 0.48 of telson length; distal and proximal pair of dorsal spines of equal length, 0.13 of telson length; posterior margin with three pairs of spines, lateral spines small, submarginal, 0.06 times telson length; submedian spines slightly longer than intermediate spines, lateral spines 0.20 of submedian and intermediate spines; both intermediate and submedian spines 0.7 of dorsal spine length, but more slender.

Eyestalk short, about as long as broad, as broad as diameter of hemispherical cornea.

Antennula (Fig. 9 A–B) with peduncle and flagella short. Basal segment as long as proximal width, with acute produced distolateral tooth just falling short of distal margin of intermediate segment, anterior margin not developed, oblique; medioventral tooth strongly developed, acute, submarginal, situated halfway basal segment; stylocerite short, reaching proximal third of basal segment, distally bluntly acute, lateral margin with few plumose setae. Intermediate segment short, broader than long, medial margin with single long distal plumose seta. Distal segment broader than long, upper flagellum short, biramous, with four fused segments; short free ramus one-segmented; longer free ramus with five segments. Lower flagellum with six or seven segments.

Antenna (Fig. 9 A–B) with basicerite short, laterally unarmed, with large gland tubercle medially; ischiocerite and merocerite normal; carpocerite extending just beyond distal end of distolateral tooth of scaphocerite, rather slender, 4.2 times longer than distal width; flagellum short, slender, about as long as postorbital carapace length; scaphocerite with lamina about twice as long as wide, anterior margin small, rounded, lateral margin broadly convex; distolateral tooth robust, 0.4 length of lamina (incl. distolateral tooth) reaching beyond lamina, curved medially; incision between distolateral tooth and lamina deep.

Epistome anteriorly broadly rounded; labrum normal, oval.

Paragnath well developed, alae with broad transverse more or less rectangular distal lobes, and small rounded more or less triangular ventromesial lobes; corpus very short, with shallow median excavation, bordered laterally by non-setose, small, oblique, carinae.

Second thoracic sternite with anterior margin broadly rounded; without median process forming round tubercle.

Third thoracic sternite with indistinct shallow lateral carinae.

Fourth thoracic sternite with developed, bluntly triangular medial plate without median notch.

Fifth thoracic sternite with well-developed lateral plates with medial broadened deep slit, posteromedial to second pereiopod coxae.

Sixth to eight thoracic sternites unarmed, broadening posteriorly.

Mandible (Fig. 10C) with incisor process with five terminal teeth of which larger distalmost is bifid, without ventromedial denticle; molar process robust, with several blunt teeth, some fringed with setal brushed.

Maxillula (Fig. 10D) with upper lacinia broad, rectangular with about 30 spines in two rows in distal half, with many simple setae along entire median margin; lower lacinia slender, acutely pointed upward, with many serrate and simple setae; palp present, but lost in dissection.

Maxilla (Fig. 11A) with basal endite well developed, bilobed, distal lobe broad with about 11 short simple distal setae of unequal length, proximal lobe small with 3 distal setae; coxal endite obsolete, median margin convex, without setae; scaphognathite large, 2.5 times longer than wide; palp simple, longer than basal endite, not expanding proximally, with row of about 4 plumose setae along proximolateral margin.

First maxilliped (Fig. 11B) with coxal and basal endite partly fused, broad; basal endite fringed with dense cover of, long simple and finely serrulate setae along median and distal margins; coxal endite convex, feebly demarcated from basal endite, with few simple setae medially; exopod well developed, flagellum with 6 plumose setae distally; caridean lobe rather small, narrow; epipod bilobate, lobes rounded; palp simple, rather short, non-setose.

Second maxilliped (Fig. 11C) with endopod short, compact; dactylar segment 2.6 times times longer than broad, fringed with short, coarsely serrulate, spiniform, and longer curled, finely serrulate setae medially; propodal segment with row of robust spines and few simple setae along expanded distomedian margin; one seta in distal part of ventrolateral margin; carpal segment short, broader than long, unarmed; meral segment without setae, ischial and basal segments almost completely fused, with few short setae, basal part produced medially; exopod long, with 12 long plumose setae in distal part; coxal segment medially produced, with few simple setae, with proximally expanded epipod laterally.

Third maxilliped (Fig. 11D) short; with ischiomerus distinct from basis, 3.2 times as long as broad, not tapered distally, somewhat flattened, with row of long simple setae along median margin, lateral margin with few simple setae; basal segment medially convex with long simple setae on medial margin; exopod well developed, reaching just halfway penultimate segment, with about 16 long plumose setae in distal part; coxal segment with small median process, with large lateral plate with few short setae; without arthrobranch; penultimate segment 2.0 times longer than broad, somewhat flattened, with many finely serrulate setae ventromedially; ultimate segment slightly shorter than penultimate segment, more slender, with groups of long coarsely serrulate setae ventromedially and distally.

First pereiopod (Fig. 12A) stout, exceeding carpocerite with chela and carpus, chela 3.2 times longer than deep, subcylindrical, slightly compressed; fingers as long as palm, stout, with lateral entire cutting edges, with groups of many serrulate setae, tips slightly hooked, suture of unguis distinct; carpo-propodal brush present, serrulate setae in distal part of carpus, and proximal part of palm; carpus 1.2 length of chela, 3.9 times longer than distal width, tapering proximally, unarmed, with simple setae medially and laterally; merus as long as carpus, 4.0 times longer than central width, somewhat bowed, with simple setae medially, short sparse setae dorsally; ischium 0.5 times merus length, slightly expanded medially, with few simple setae medially; basis slightly smaller than ischium, with few simple setae medially; coxa with small ventral lobe with few short simple setae.

Second pereiopods (Fig. 12 B–C) similar in form, unequal in length. Major right chela 1.8 times postorbital carapace length, palm smooth, compressed, without carinae, with few scattered simple short setae; fingers with few simple setae in distal part; dactylus 0.5 of palm length, 3.3 times longer than deep, with large broad flattened tooth with row denticles at almost halfway of cutting edge, distal part of cutting edge entire, tip strongly hooked; fixed finger 1.9 times as long as deep, with broad flattened tooth in proximal part, separated by shallow notch from acute triangular tooth at about distal third of cutting edge, distal part of cutting edge entire, straight, tip strongly hooked; carpus 0.4 of palm length, about as long as distal width, strongly tapering proximally; merus 1.4 times as long as carpus, 1.2 times longer than central width, distomedially excavate; ischium much shorter than merus, tapering proximally, with slightly protruded distomedial angle; basis and coxa without special features. Minor left cheliped with chela 1.2 times postorbital carapace length, dactylus slightly longer in relation to palm than in major chela; palm less swollen than in major chela.

Ambulatory pereiopods short, stout. Dactylus of third pereiopod (Figs 13A, 14 A–B, 16A, 17A) with corpus compressed, 1.8 times longer than proximal width, accessory tooth terminal, blunt, perpendicular to flexor margin, flexor margin with one large acute forward directed tooth at proximal third, with two small denticles in between proximal tooth and accessory tooth, with few simple setae at distolateral surface, with row of simple short setae along flexor margin; unguis longer than accessory tooth, acute, 0.43 of corpus length, without terminal scales, with faint proximal transverse grooves; propodus stout, compressed, 4.0 times length of dactylus, 4.0 times longer than deep, with minute lateral distoventral spine, and distal ventral spine, with many long simple setae on lateral margin; carpus 0.7 of propodus length, unarmed; merus 1.3 times propodus length, 3.7 times longer than central depth, unarmed; ischium 0.7 of merus length, slightly tapering proximally; basis and coxa without special features. Fourth and fifth (Fig. 13B) pereiopods similar.

First pleopod with endopod almost half as long as exopod, with plumose setae laterally and distally, with long simple setae distomedially.

Uropods, with short unarmed protopodite; exopod broad, 2.2 times longer than central width, lateral margin feebly convex, without distolateral tooth, with minute spinule distolaterally; endopod exceeding exopod, about as long as telson, 2.8 times longer than wide.

Ovigerous female with about 100 eggs of 0.05 mm in diameter.

Colour in life

(Fig. 15E). Body and chelipeds generally semitransparent, with small red chromatophores and scattered larger white spots. Carapace with larger white chromatophores at base of rostrum and scattered in a bilaterally symmetrical pattern. Eyestalks reddish with some big dorsal white spots, cornea with white spots as well. Antennular peduncle and scaphocerite reddish. Ambulatory pereiopods translucent with white chromatophores at joints. Abdomen reddish with many small white chromatophores and large white spots dorsally and laterally at fixed distances. Tailfan with red and white chromatophores. Eggs dark red.

Host.

Solitary ascidian (A. Gittenberger Asc. 67).

Distribution.

Only known from its type locality at Tidore, Indonesia.

Etymology.

The species is named " bagginsi ", inspired by the famous Hobbit family name “Baggins” featured in the "The Hobbit" and "The Lord of the Rings" books. The fictional characters called “Hobbits” possess hairy feet comparable to this species.

Remarks.

The species bears resemblance to O. sibogae in its morphological characters. It differs in having a strongly developed ventral tooth on the rostrum; a strongly produced pterygostomial margin of the carapace; two pairs of dorsal spines on the telson and a broad upper lacinia of the maxillula. In addition, the pereiopods bear some notable differences: the segments of the first pereiopods are stouter and the cutting edge of the major cheliped bears a broad flattened tooth. The dactyli of the ambulatory pereiopods bear two denticles on the flexor margin. The unguis is devoid of distal scales. Most characteristic is the dense cover of simple setae on the propodi of the ambulatory pereiopods. Life colour patterns of the new species is similar to that of O. sibogae (see Levitt & Shenkar 2018: fig. 2B) with scattered white chromatophores of various sizes scattered over body and appendages. The new species has a reddish overall appearance while O. sibogae is paler.