Zeuxo mooneyi, Edgar, 2008

Edgar, Graham J., 2008, Shallow water Tanaidae (Crustacea: Tanaidacea) of Australia, Zootaxa 1836 (1), pp. 1-92 : 68-73

Zeuxo mooneyi n. sp.

( Figs 34–36 )

Material examined. Holotype. Male ( NMV J56153 ), 1.7 mm, Bowen Island Passage , Jervis Bay, NSW, (35º07’S 150º47’E), 1 m depth, macrophyte washings, 29 Sep 1999.

Paratypes. One male, one juvenile ( NMV J56154 ) . Holotype location.

Diagnosis. With characters of genus. Dorsal surface with mottled pigmentation confined to cephalothorax, with darkest coloration in mid region; antennule article 1 about three times longer than wide in males, ter- minal article with three or four aesthetascs in male; left mandible with lacinia mobilis broad and tooth-like, with a digitate outer margin, right mandible with lacinia mobilis peg-like with outer concavity; pereopod 1 coxa produced anteriorly into slight bulge with two setae; pleopod basal article with five setae on outer margin, one seta on inner margin, endopod with one seta on inner margin; uropod with four articles in mature individuals; sexually dimorphic.

Description. FEMALE unknown.

MALE. Body ( Fig. 34 ). Length to 1.7 mm; preserved specimens with mottled pigmentation on cephalothorax, very dark in middorsal region and with lighter grey shading on postero-lateral lobes.

Cephalothorax rounded and narrowing anteriorly in dorsal view, with slight lateral inflection; length similar to width and slightly more than one-fifth body length.

Pereon occupies about 53% of total length; pereonites with several setae along anterio-dorsal and lateral margins; pereonite 1 length about one-fifth width; pereonites 2 and 3 similar, almost twice length of pereonite 1; pereonites 4 and 5 similar, about 1.5 times length of pereonite 3; pereonite 6 about three-quarters length of pereonite 5.

Pleonites together slightly less than 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 as long as pleonite 3.

Pleotelson about length of pleonite 1; posterior margin with pair of short setae central between pair of long setae, two setae anterior to articulation with uropod, a long simple seta posterior on lateral margin.

Antennule ( Fig. 34 ). Total length about length of cephalothorax, with article 1 about three times longer than wide, with four setae one-third distance along article and three long simple setae distally; article 2 about one-third length of article 1, about 1.3 times longer than wide, with three setae distally; article 3 length about 1.5 times width, about two-third length of article 2, with about four simple setae distally; article 4 greatly reduced and cap-shaped, with about seven long simple setae and three or four aesthetascs.

Antenna ( Fig. 34 ). Article 1 as long as wide, lacking setae; article 2 1.5 times length of article 1, length about 1.5 times width, with two setae midway on outer margin, one seta midway on inner margin, and two distal setae; article 3 half length of article 2, lacking setae; article 4 twice length of article 3, about 1.6 times as long as wide, with two distal setae; article 5 four-fifths length of article 4, with about four setae distally; article 6 length similar to width, with about six long simple setae; article 7 reduced to small terminal cap with about eight long setae.

Mouthparts ( Fig. 35 ). Labrum with setulose fringe.

Left mandible with lacinia mobilis broad and tooth-like, with a digitate outer margin, lacking accessory seta, pars incisiva smooth with bifurcated tip, pars molaris broad and corrugated; right mandible lacinia mobilis peg-like with outer concavity, lacking accessory seta, pars incisiva smooth, 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 proximal lateral margins.

Maxillule endite with eight large terminal spiniform setae, setulose on outer margin near base of spines; palp with at least two long setae, possibly more than two but with extra setae detached on dissected specimen.

Maxilliped coxa and basis not joined medially; coxa with two proximo-medial seta; basis with very fine marginal spines, with a short distal seta; endite setulose around distal margin, with two small spiniform setae distal near medial margin, two spiniform setae medial on distal margin and two circumplumose setae near distal margin that are about one-third length of long setae on inner margin of palp; palp with four articles, article 1 as long as wide with simple seta distal on outer margin and fine marginal teeth, article 2 slightly longer than article 1 with single seta distal on outer margin, three very long setae extending distally in a row from midway along inner margin and two long distal setae, article 3 similar in length to article 2, fringed with about nine long setae along inner margin, article 4 about two-thirds length of article 3 and two-thirds 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. 34 ). Basis about as long as wide with one distal seta near ventral margin and one seta adjacent to articulation with merus; merus triangular with two setae three-quarters distance along ventral margin; carpus longer than basis, longer than wide, with two setae distal near ventral margin, and two distal dorsal setae; propodus with three setae midway along ventral margin, about six long setae extending as comb along inner margin of fixed finger to above dorsal margin of dactylus when dactylus closed, and group of three or four setae near articulation with dactylus; dactylus with row of about six very short setae along ventral margin, unguis short and solid, about one-eighth total length of dactylus.

Pereopod 1 ( Fig. 36 ). Coxa produced anteriorly into slight bulge with two 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 three distal setae and seta two-thirds distance along dorsal margin; unguis half length of dactylus.

Pereopods 2 and 3 ( Fig. 36 ). Similar; basis width one-quarter length, length slightly less than merus, carpus and propodus together; merus two-fifths length of basis, with short spiniform seta and simple seta distal on ventral margin; carpus two-thirds length of merus, with three serrated spiniform setae and simple seta near distal margin; propodus 1.5 times length of carpus; unguis half length of dactylus.

Pereopods 4 and 5 ( Fig. 36 ). Similar; basis width about one-third length; merus with a pair of large spiniform setae and simple seta distal on ventral margin; carpus with three spiniform setae and two simple setae near distal margin; propodus 1.5 times length of merus, with seta distal near 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 about six flattened setae.

Pereopod 6 ( Fig. 36 ). Basis width about one-third length; merus with a pair of large spiniform setae and simple seta distal on ventral margin and simper seta distal on dorsal margin; carpus with parallel rows of two and three spiniform setae around distal margin; propodus with distal comb-like row of about seven denticulate setae and two long simple setae and pappose seta dorso-distally; dactylus with lateral comb-like rows of about seven setae.

Pleopods 1–3 ( Fig. 36 ). Similar; basal article length similar to width, with five plumose setae along outer margin and one plumose seta on inner margin; exopod with about 25 plumose setae along outer margin; endopod with one plumose seta on inner margin, large terminal circumplumose seta and about 14 plumose setae along outer margin.

Uropod ( Fig. 36 ). Four articles; basal article with four distal setae; articles 2, 3 and 4 each about two-third length of preceding article, with five or six long distal setae.

Etymology. Named in recognition of the contributions to conservation by brothers Nick and Peter Mooney.

Distribution. Jervis Bay, NSW; 1 m depth.

Remarks. Although only males of this species are presently known, it is readily distinguished from other known Australian Zeuxo species in possessing only four uropod articles and in the distinctive shape of the mandibles. The lacinia mobilis of the left mandible is well developed while that of the right mandible is narrow with an indented tip. Setation on pereopods of this species is also relatively sparse compared to other Zeuxo species.

Zeuxo mooneyi is very close in appearance to the tropical Indo-West Pacific species Z. coralensis Sieg , with both species possessing four uropod articles, well-developed lacinia mobilis of left mandible, three or four aesthetascs on antennule, and two projecting setae on coxa of pereopod 1 (see Sieg 1980b). These two species nevertheless differ greatly in body size, with examined male Z. mooneyi reaching only 1.7 mm length compared to the 3 mm length generally attained by Z. coralensis (to 4.8 mm for exceptional animals; Sieg 1980b). The two species also differ in minor details of setation, including additional simple setae on most pereopod articles of Z. coralensis . Two other species in the Z. coralensis group— Zeuxo zorro Bamber and Zeuxo phytalensis Sieg —are discussed by Bamber (1997). Zeuxo mooneyi differs from these species in its relatively short distal seta on propodus of pereopods 2 and 3 (about half length of dactylus) and, additionally for the Hong Kong species Z. zorro , in possessing a large setose seta on the inner margin of the basal article of pleopods.

Figures

FIGURE 34. Zeuxo mooneyi n. sp. Murray Passage, NSW. Male dorsal (holotype), antennule (A1), antenna (A2), cheliped (CH), pleotelson (Plt). Scale units 0.1 mm (appendages) and 1 mm (dorsal).

FIGURE 35. Zeuxo mooneyi n. sp. Murray Passage, NSW. Labrum (L), left mandible (Mdl), right mandible (Mdr), labium (La), maxillule (Mx), maxilliped (Mxp), epignath (E). Scale units 0.1 mm.

FIGURE 36. Zeuxo mooneyi n. sp. Murray Passage, NSW. Pereopods 1–6 (P1–P6), pleopod (Pl), uropod (U). Scale units 0.1 mm.