Austrotanais rileyi, Edgar, 2008

Edgar, Graham J., 2008, Shallow water Tanaidae (Crustacea: Tanaidacea) of Australia, Zootaxa 1836 (1), pp. 1-92 : 12-17

publication ID 10.11646/zootaxa.1836.1.1


persistent identifier

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scientific name

Austrotanais rileyi

n. sp.

Austrotanais rileyi n. sp.

( Figs 4–6 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Material examined. Holotype. Ovigerous female ( NMV J56133 View Materials ), 8.0 mm, Governor Island, Bicheno , Tasmania (41°53’S 148°17’E), 10 m depth, kelp ( Lessonia corrugata ) holdfast, 20 May 1993. GoogleMaps

Paratypes. 8 juveniles ( NMV J56134 View Materials ), holotype location .

Other material. Male, Rottnest Island, WA (32°01’S 115°33’E), 1 m depth, macroalgal washings, 21 Jan 1996.

Diagnosis. With characters of genus. Antennule article 1 about twice as long as wide; left mandible with lacinia mobilis greatly reduced and peg-like; right mandible with lacinia mobilis reduced to large thorn; pereopod coxa with two setae but lacking pronounced anterior bulge.

Description. FEMALE

Body ( Fig. 4 View FIGURE 4 ). Large, body length to 8.5 mm; preserved specimens with red-brown mottled pigmentation extending most prominently on cephalothorax, pereonites 2–6, pleonite 3–5 and pleotelson.

Cephalothorax rounded and narrowing anteriorly in dorsal view, length slightly less than width, one-fifth body length.

Pereon occupies about half total length; pereonites with setae on anterio-dorsal and lateral margins; pereonite 1 length about one-fifth width; pereonites 2 and 3 similar, almost twice length of pereonite 1; pereonites 4-6 similar, about 1.3 length of pereonite 3.

Pleonites together about one-fifth of body length; pleonites 1 and 2 similar, with dense row of setae extending prominently around lateral and dorsal surfaces; pleonite 3 half length of pleonite 2; pleonites 4 and 5 with similar length to pleonite 3 but about 78% width, with lateral and dorsal simple setae.

Pleotelson about length of pleonites 4 and 5 together; posterior margin with medial projection, surmounted by pair of short setae central between pair of longer setae, single long seta with several small associated setae dorso-lateral to medial projection.

Antennule ( Fig. 4 View FIGURE 4 ). Article 1 about twice as long as wide, with three small pappose setae about one-third distance along margin, one or two large pappose setae and numerous long simple setae distally; article 2 about one-third length of article 1, with about eight setae distally; article 3 about three-quarters length of article 2, with prominent pappose seta distally; article 4 greatly reduced and cap-shaped, with numerous long setae and eight aesthetascs.

Antenna ( Fig. 4 View FIGURE 4 ). Article 1 as long as wide, lacking setae; article 2 about 1.5 times length of article 1, as long as wide, with several distal setae; article 3 two-thirds length of article 2, with distal seta; article 4 1.5 times length of article 3, with about four long simple setae and pappose seta; article 5 slightly shorter than article 4, with about three simple setae and three pappose setae distally; article 6 length similar to width, with several long setae; seventh article reduced to small terminal cap with numerous long setae.

Mouthparts ( Fig. 5 View FIGURE 5 ). Labrum carpeted by fine setae, particularly near distal margin.

Left mandible with lacinia mobilis greatly reduced and peg-like, pars incisiva smooth and acute, pars molaris broad and corrugated; right mandible with lacinia mobilis reduced to large thorn with adjacent denticulate seta, pars incisiva smooth and acute, pars molaris broad and corrugated.

Labium with inner and outer lobes covered by fine setae near distal margins, inner lobe extending past distal margin of outer lobe; outer lobe with small pointed terminal process and with very fine spines projecting from proximal lateral margins.

Maxillule endite with eight large terminal spiniform setae and cluster of fine terminal setules on outer margin near base of spines; palp with about nine long terminal simple setae.

Maxilliped coxa and basis not joined medially; basis with four or five long setae distally near articulation with palp and three or four long setae along distal outer margin; endite with setulose fringe, two small spiniform setae and two simple setae about twice length of adjacent spiniform setae in medio-distal corner; palp with four articles, article 1 as long as wide with fine setae distally on outer margin, article 2 similar length to article 1 with large denticulate seta distal on outer margin, two rows of about six very long setae extending distally from midway along inner margin, article 3 slightly shorter than article 2 and fringed with two rows of about seven long setae along inner margin, article 4 with similar length to article 3 and half width, with one or two long setae distally on outer margin, and two adjacent rows of about six setae distally on inner margin.

Epignath fringed by fine setules and with terminal circumplumose seta.

Cheliped ( Fig. 4 View FIGURE 4 ). Basis length similar to width, with two setae on lateral surface and about three small setae near distal ventral margin; merus triangular with about four setae three-quarters distance along ventral margin and two long setae lateral; carpus similar in length to basis, with about ten distal ventral setae, six distal dorsal setae, and single small seta midway along dorsal margin; propodus similar in length to carpus, with large terminal spiniform seta, five or six setae midway along ventral margin, about eleven setae along dorsal margin of fixed finger and four setae near articulation with dactylus; dactylus with row of very short setae along ventral margin, unguis short and solid, about one sixth total length of dactylus.

Pereopod 1 ( Fig. 6 View FIGURE 6 ). Coxa with two slight ventral spurs and two setae; basis length about four times width; merus about one-quarter length of basis; carpus about 1.4 length of merus; propodus length of merus and carpus together, with row of about nine setae near distal ventral margin, pappose seta and simple seta three-quarters distance along dorsal margin; unguis half length of dactylus.

Pereopods 2 and 3 ( Fig. 6 View FIGURE 6 ). Similar, basis length about 2.5 times width, slightly less than length of merus, carpus and propodus together; merus two-fifths length of basis, with two to four setae midway along ventral margin, two to four short spiniform setae and four simple setae ventro-distally, two simple setae dorso-distally; carpus length similar to merus, rows of about seven and eleven spiniform setae extending in increasing size either side of ventral margin with spine at dorso-distal corner largest; propodus slightly shorter than carpus and half width, two simple setae and long denticulate setae distally; unguis about one-third length of dactylus.

Pereopods 4 and 5 ( Fig. 6 View FIGURE 6 ). Similar; basis length double width; merus with three or four ventro-distal spiniform setae; carpus with two rows of about seven spiniform setae adjacent to distal margin; propodus similar in length to carpus, three-quarters width, with two long simple setae and two or three pappose setae distally; unguis merged into claw-like dactylus, with lateral comb-like rows of about eight flattened setae.

Pereopod 6 ( Fig. 6 View FIGURE 6 ). Basis length about 2.5 times width; merus with two to four spiniform setae threequarters distance along ventral margin; carpus with two adjacent rows of about eight spiniform setae; propodus with distal comb-like row of about 14 flattened denticulate setae and dorso-distal group of about eight longer denticulate setae and two very long simple setae; dactylus with lateral comb-like row of about eight flattened setae.

Pleopods 1–3 ( Fig. 6 View FIGURE 6 ). Similar; basal article with about 16 long plumose setae along outer margin and two to four small plumose seta on inner margin; exopod with numerous long plumose setae along outer margin, very fine setae along inner margin; endopod with about 18 plumose setae along inner margin and numerous plumose setae along outer margin, terminal circumplumose seta with fine setae adjacent.

Uropod ( Fig. 6 View FIGURE 6 ). Four articles; basal article length 1.2 times width, three setae two-thirds distance towards distal margin and about five long setae distally; article 2 slightly shorter than articles 2 and 3 together, distal setae shorter than setae on articles 2 and 3.

MALE. Similar to female.

Etymology. Named after Sean Riley, in recognition to his contribution to marine conservation in Tasmania.

Distribution. Rottnest Island, WA, to eastern Tasmania. 1–10 m depth.

Remarks. This tanaid occurs around the southern Australian coast in seaweed holdfasts. It is recognisable without dissection by the presence of five pleonites plus dorsal fringe of setae across pleonites 1 and 2, and the obvious contrast between the conspicuous red-brown stippling across most of the dorsal surface and paler shading of pereonite 1 and pleonites 1 and 2. In size, body coloration and general appearance, it resembles Tanais pongo of southwestern Australia ( Bamber, 2005), but differs in characters of the genus, most notably including presence of pleonite 5 and uropod with four articles, and presence of four or five rather than one long distal setae on the maxilliped basis.


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