Zeuxo odohertyae, Edgar, 2008

Edgar, Graham J., 2008, Shallow water Tanaidae (Crustacea: Tanaidacea) of Australia, Zootaxa 1836 (1), pp. 1-92 : 63-68

Zeuxo odohertyae n. sp.

( Figs 31–33 )

Material examined. Holotype. Female ( NMV J56151 ), 4.5 mm, Georges Bay , Tas, 2 m depth, Heterozostera nigricaulis washings, John Moverley, 3 Oct 1995.

Paratype. One male ( NMV J56152 ), holotype location .

Diagnosis. With characters of genus. Dorsal surface with tan mottled pigmentation extending from cephalothorax to pleotelson; antennule article 1 about 2.8 times (female) and nearly four times (male) longer than wide, terminal article with three or four (female) and five (male) aesthetascs; left mandible with lacinia mobilis reduced, peg-like and acutely pointed, right mandible with lacinia mobilis reduced to serrated thorn; pereopod 1 coxa produced anteriorly into pronounced bulge with three to five setae; basal article with about nine setae on outer margin, one seta on inner margin, endopod with five or six setae on inner margin; uropod with seven articles in mature individuals; sexually dimorphic.

Description. FEMALE

Body ( Fig. 31 ). Length to 5 mm; preserved specimens with tan mottled pigmentation extending from cephalothorax to pleotelson and on chelipeds, pereopods, antenna and articles 1 and 3 of antennule.

Cephalothorax rounded and narrowing anteriorly in dorsal view, with slight medial concavity, slightly longer than wide, and slightly less than one-fifth body length.

Pereon occupies about 56% of total length; pereonites with several setae along anterio-dorsal and lateral margins; pereonite 1 length about one-fifth width; pereonite 2 almost twice length of pereonite 1; pereonite 3 slightly longer than pereonite 2 and five-sixths width; pereonites 4 and 5 similar, about 1.5 times length of pereonite 3; pereonite 6 slightly shorter than pereonite 5.

Pleonites together one-fifth as long as body; pleonites 1, 2 and 3 decreasing in length and width, each about four-fifths length of preceding segment; pleonites 4 and 5 similar, together slightly longer than pleonite 3.

Pleotelson length similar to pleonite 1; posterior margin with pair of short setae central between pair of long setae, three or four setae anterior to articulation with uropod, long simple seta posterior on lateral margin.

Antennule ( Fig. 31 ). Total length approximately four-fifths length of cephalothorax, with article 1 about 2.8 times longer than wide, with three pappose setae one-third distance along outer margin, one simple seta halfway along outer margin, and two or three pappose setae and about five long simple setae distally; article 2 about two-fifths length of article 1, about twice as long as wide, with about three pappose setae and about six simple setae distally; article 3 length just over twice width, about two-third length of article 2, with two or three pappose setae and about four simple setae distally; article 4 greatly reduced and cap-shaped, with about ten long simple setae and three or four aesthetascs.

Antenna ( Fig. 31 ). Article 1 as long as wide, lacking setae; article 2 twice length of article 1, length about twice width, with small setae midway on inner and outer margins and two setae distally; article 3 half length of article 2, with distal seta; article 4 twice length of article 3, with about ten long distal setae; article 5 threequarters length of article 4, with about three simple setae and two pappose setae distally; article 6 length similar to width, with about six long setae; seventh article reduced to small terminal cap with about eight long setae.

Mouthparts ( Fig. 32 ). Labrum with setulose fringe.

Left mandible with lacinia mobilis reduced, peg-like and acutely-pointed, with small thorn at base, pars incisiva smooth and acute, pars molaris broad and corrugated; right mandible with lacinia mobilis reduced to serrated thorn with spiniform seta at base, pars incisiva with three-lobed apex, pars molaris broad and corrugated.

Labium with inner lobe setulose; outer lobe setulose on distal margin, with ovate terminal process and very fine spines projecting from lateral margins.

Maxillule endite with eight large terminal spiniform setae, setulose on outer margin near base of spines; palp with eight long setae.

Maxilliped coxa and basis not joined medially; coxa with two proximo-medial setae; basis lacking fine marginal setules or spines, with two distal setae and single medial seta; endite with two small spiniform setae distal near medial margin, two longer spiniform setae medial on distal margin and two circumplumose setae near distal margin that are about half length of long simple setae on inner margin of palp; palp with four articles, article 1 as long as wide with simple seta distal on outer margin, article 2 slightly longer than article 1 with single seta distal on outer margin, about twelve very long setae extending distally in a row from midway along inner margin to outer margin, and three long distal plumose setae, article 3 considerably smaller than article 2, fringed with about ten long setae along inner margin, article 4 shorter than article 3 and about half width, with a long seta distal on outer margin, a long terminal seta, and two adjacent rows of about five setae distal on inner margin.

Epignath with terminal circumplumose seta and fringe of fine setules.

Cheliped ( Fig. 31 ). Basis longer than wide with one distal seta near ventral margin and one seta adjacent to articulation with merus; merus triangular with four setae three-quarters distance along ventral margin and three medial setae; carpus similar in length to basis, longer than wide, with three setae distal near ventral margin, three distal dorsal setae and one seta one-third distance along dorsal margin; propodus with about six setae ascending in size midway along ventral margin, about seven long setae extending as comb along inner margin of fixed finger to above dorsal dactylus margin when dactylus closed, and group of three or four setae near articulation with dactylus; dactylus with row of about twelve very short setae along ventral margin, unguis short and solid, about one-fifth total length of dactylus.

Pereopod 1 ( Fig. 33 ). Coxa produced anteriorly into pronounced bulge with three to five setae; basis length approximately five times width; merus about one-quarter length of basis; carpus 1.5 times length of merus; propodus length similar to merus and carpus together, with about five seta near distal margin, two setae two-thirds distance along dorsal margin and pappose seta two-thirds distance along ventral margin; unguis half length of dactylus.

Pereopods 2 and 3 ( Fig. 33 ). Similar; basis width one-third length, length slightly less than merus, carpus and propodus together; merus half length of basis, with one short spiniform seta and about four simple setae distal on ventral margin and one simple seta distal on dorsal margin; carpus two-thirds length of merus, about nine serrated spiniform setae along distal margin with dorsal spiniform seta largest; propodus 1.5 times length of carpus; unguis half length of dactylus.

Pereopods 4 and 5 ( Fig. 33 ). Similar; basis width about one-third length; merus with a pair of large spiniform setae and about two simple setae distal on ventral margin, about two simple setae distal on dorsal margin; carpus with two adjacent rows of five or six serrated spiniform setae around distal margin; propodus 1.5 times length of merus, with about five setae on ventral margin and pappose seta plus two long simple setae distal near dorsal margin; unguis merged into claw-like dactylus, with comb-like lateral rows of five or six flattened setae.

Pereopod 6 ( Fig. 33 ). Basis width about one-third length; merus with a pair of large spiniform setae and about two simple setae distal on ventral margin, about two simple setae distal on dorsal margin; carpus with parallel rows of five or six spiniform setae around distal margin; propodus with distal comb-like row of about 10 flattened denticulate setae and dorso-distal group of about five long denticulate setae with long simple seta and pappose seta; dactylus with lateral comb-like rows of about five setae.

Pleopods 1–3 ( Fig. 33 ). Similar; basal article length similar to width, with about nine plumose setae along outer margin and one plumose seta on inner margin; exopod with about 30 plumose setae along outer margin; endopod with five or six plumose seta on inner margin, large terminal circumplumose seta and about 22 plumose setae along outer margin.

Uropod ( Fig. 33 ). Seven articles, fewer on immature animals; basal article length about 2.5 times width, with about five distal simple setae; article 2 one-quarter length of article 1, lacking setae (apparently recently subdivided in figured specimen); article 3 similar length to article 2, with about six distal setae; articles 4, 5 and 6 similar other than diminishing in length, with about six distal setae including pappose seta; terminal article length slightly less than preceding article, with about eight long terminal simple setae and pappose seta.

MALE. Similar to female, other than

Antennule ( Fig. 31 ). Total length slightly greater than length of cephalothorax, with article 1 about four times longer than wide; article 4 with five terminal aesthetascs.

Cheliped ( Fig. 31 ). All articles proportionately wider than in female; basis and carpus length similar to width; dactylus with unguis about one-tenth total length of dactylus.

Etymology. Named in memory of Mary O’Doherty in recognition of her contribution to conservation in Tasmania.

Distribution. Southeastern Tasmania.

Remarks. Zeuxo odohertyae possesses nine setae on the outer margin of the pleopod basal article, considerably more than other known Australian species of Zeuxo , which have six or less. The species also differs from others in the combination of characters described in diagnosis. All specimens so far found have been living in seagrass beds.

Figures

FIGURE 31. Zeuxo odohertyae n. sp. Georges Bay, Tas. Female dorsal (holotype), male dorsal (paratype; pigmentation not shown), antennules (A1), antennae (A2), chelipeds (CH), pleotelson (Plt). Scale units 0.1 mm (appendages) and 1 mm (dorsal).

FIGURE 32. Zeuxo odohertyae n. sp. Georges Bay, Tas. Labrum (L), left mandible (Mdl), right mandible (Mdr), labium (La), maxillule (Mx), maxilliped (Mxp), epignath (E). Scale units 0.1 mm.

FIGURE 33. Zeuxo odohertyae n. sp. Georges Bay, Tas. Pereopods 1–6 (P1–P6), pleopod (Pl), uropod (U). Scale units 0.1 mm.