Tanais cf. dulongii (Audouin, 1826)

Edgar, Graham J., 2008, Shallow water Tanaidae (Crustacea: Tanaidacea) of Australia, Zootaxa 1836 (1), pp. 1-92 : 6-12

publication ID	https://doi.org/ 10.11646/zootaxa.1836.1.1
DOI	https://doi.org/10.5281/zenodo.5127364
persistent identifier	https://treatment.plazi.org/id/676CB04D-FF97-FFF2-FF32-F995FAC4337F
treatment provided by	Felipe
scientific name	Tanais cf. dulongii (Audouin, 1826)
status

Treatment

Tanais cf. dulongii (Audouin, 1826) View in CoL

( Figs 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Material examined. Four males, two females (one ovigerous), five juveniles, (one male, two females, three juveniles deposited NMV J56621 View Materials ), Bicton, Swan Estuary, WA (3202’S 115°45’E), 1 m depth, Cystoseira trinodis washings, 10 Jan 1994 .

Diagnosis. With characters of genus. Antennule article 1 about 2.5 (female) and 3.5 (male) times longer than wide, terminal article with five to seven aesthetascs; left mandible lacinia mobilis broad and tooth-like with serrated margin; right mandible lacinia mobilis peg-like; pereopod coxa with two setae, lacking pronounced anterior bulge; pleopod basal article with seven to eleven setae on outer margin, two setae on inner margin, endopod with ten to twelve setae on inner margin; uropod with three articles.

Description. FEMALE.

Body ( Fig. 1 View FIGURE 1 ). Observed length to 5.0 mm; preserved specimens with mottled pigmentation extending from cephalothorax to pleotelson and on chelipeds, antennae, antennules; pigmentation on faded specimens most prominent on cephalothorax and posterior dorsal margin of pereonites.

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

Pereon occupies about 58% of total length; pereonites with simple setae on anterio-dorsal and lateral margins; pereonite 1 length about one-quarter width; pereonites 2–6 similar, twice length of pereonite 1.

Pleonites together one-fifth as long as body; pleonites 1 and 2 of similar length, with prominent row of plumose setae extending transversely around lateral margin to near midline; pleonite 3 similar length to pleonite 2, with lateral group of three to four large setae; pleonite 4 two-fifths length of pleonite 3, with lateral group of two to five setae; pleonite 5 absent.

Pleotelson about length of pleonites 3 and 4 together; posterior margin with two central pairs of setae, two to four long setae plus pappose seta anterior to articulation with uropod, one long seta anterio-laterally.

Antennule ( Fig. 1 View FIGURE 1 ). Article 1 about 2.5 times longer than wide, with three small pappose setae two-fifth distance along outer margin and about four simple setae and four pappose setae distally; article 2 about onethird length of article 1, with about nine setae distally; article 3 about three-quarters length of article 2, with about three setae distally; article 4 greatly reduced and cap-shaped, with about seven long simple setae and five aesthetascs.

Antenna ( Fig. 1 View FIGURE 1 ). Article 1 as long as wide, lacking setae; article 2 1.5 times length of article 1, with one small seta on outer margin and three setae distally; article 3 half length of article 2, with a single distal seta; article 4 twice length of article 3, with two simple setae and pappose seta distally; article 5 three-quarters length of article 4, with about six simple and 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. 2 View FIGURE 2 ). Labrum carpeted by setae.

Left mandible lacinia mobilis tooth-like, with an undulating outer margin and strong denticulate seta at base, pars incisiva smooth and acute, pars molaris broad and corrugated; right mandible lacinia mobilis peglike, with denticulate seta at base, pars incisiva smooth and acute, pars molaris broad and corrugated.

Labium with inner and outer lobes covered by fine setules near distal margins, outer lobe with small rounded 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; palp with two very long and four long pappose setae.

Maxilliped coxa and basis not joined medially; coxa with proximo-medial seta and a single large seta medio-distally; basis with two to four long spiniform setae on lateral margin, single seta proximo-medially, three or four very long setae near articulation with palp; endite setulose around distal margin, two small spiniform setae medio-distally and two large circumplumose setae distally; palp with four articles, article 1 as long as wide, article 2 triangular, slightly longer than article 1 with single seta distal on outer margin, three or four long setae extending distally in a row from midway along inner margin and two long setae distally, article 3 slightly smaller than article 2 and fringed with row of about nine very long setae along inner margin, article 4 similar in length to article 3 but two-thirds width, with a long seta two-third distance along outer margin, two long terminal seta, and two parallel rows of about five setae distally on inner margin.

Epignath with terminal circumplumose seta and fringed by fine setules.

Cheliped ( Fig. 1 View FIGURE 1 ). Basis longer than wide with two or three setae distally near ventral margin; merus triangular with two to four setae two-thirds distance along ventral margin; carpus similar in length to basis, longer than wide, with two to three setae distal on ventral margin, three to four setae distal adjacent to articulation with propodus, and two to four distal dorsal setae; propodus similar in length to carpus, length twice width, with large terminal spiniform seta, four setae midway along ventral margin, about eight setae along dorsal margin of fixed finger and group of three or four simple setae plus a large pappose seta near articulation with dactylus; dactylus ventral margin sinusoidal with row of very short setae, unguis short and solid, about onefifth total length of dactylus.

Pereopod 1 ( Fig. 3 View FIGURE 3 ). Coxa with two setae, lacking pronounced anterior bulge; basis width slightly less than one-third length; merus about one-third length of basis; carpus 1.5 times length of merus; propodus slightly less than length of merus and carpus together, with six setae near distal ventral margin and two setae near distal dorsal margin; unguis half length of dactylus.

Pereopods 2 and 3 ( Fig. 3 View FIGURE 3 ). Similar; basis width slightly over one-third length, length similar to merus, carpus and propodus together; merus one-third length of basis, with two short spiniform setae ventro-distally; carpus two-thirds length of merus, two parallel series of four and six serrated spiniform setae along distal margin with dorsal spine largest; propodus 1.5 times length of carpus, with plumose seta and three long simple distal setae; unguis one-third length of dactylus.

Pereopods 4 and 5 ( Fig. 3 View FIGURE 3 ). Similar; basis width about two-fifths length; merus with two or three spiniform setae two-fifths way along ventral margin; carpus with parallel rows of four or five serrated spiniform setae around distal margin; propodus 1.5 times length of merus, with one simple seta near distal ventral margin, one simple seta medio-distally, and pappose seta plus two long denticulate setae near distal dorsal margin; unguis merged into claw-like dactylus, with comb-like lateral rows of about six flattened setae on the two sides.

Pereopod 6 ( Fig. 3 View FIGURE 3 ). Basis width slightly over one-third length, length similar to merus, carpus and propodus together; merus with three spiniform setae three-quarters way along ventral margin; carpus with parallel rows of three and five spiniform setae around distal margin; propodus with distal comb-like row of six or seven flattened denticulate setae and dorso-distal group of about four longer denticulate setae and two very long simple setae; dactylus with lateral comb-like rows of about eight flattened setae.

Pleopods 1–3 ( Fig. 3 View FIGURE 3 ). Similar; basal article with seven to eleven plumose setae along outer margin and two plumose setae on inner margin; exopod with numerous plumose setae along outer margin; endopod with ten to twelve plumose setae along inner margin, short terminal circumplumose seta and numerous plumose setae along outer margin.

Uropod ( Fig. 3 View FIGURE 3 ). Three articles, basal article length slightly greater than twice width with four to six distal setae, article 2 slightly longer and narrower than basal article with six to eight simple and 2 pappose setae distally, article 3 slightly longer than half length of article 2, with numerous long terminal setae including pappose seta.

MALE. Similar to female, other than

Body ( Fig. 1 View FIGURE 1 ). Cephalothorax about 23% of body length.

Pereon about 47% of total length; pereonite 1 length about one-fifth width; pereonites 2 and 3 similar, twice length of pereonite 1; pereonites 4 and 5 similar, slightly longer than pereonite 3; pereonite 6 about fourfifths length of pereonite 5.

Antennule ( Fig. 1 View FIGURE 1 ). Article 1 about 3.5 times longer than wide.

Antenna ( Fig. 1 View FIGURE 1 ). Article 2 twice length of article 1; article 3 one-third length of article 2; article 4 three times length of article 3.

Cheliped ( Fig. 1 View FIGURE 1 ). Basis as long as wide; carpus similar in length to basis, as long as wide; propodus longer than carpus; dactylus ventral margin crescent-shaped, unguis about one eighth total length of dactylus.

Distribution. Swan Estuary, WA, 0–2 m depth; Tanais dulongii : Europe, eastern United States ( Sieg, 1980b).

Remarks. Specimens collected in the Swan estuary agree well with diagnoses and figures of Tanais dulongii by Sieg (1980b), who lists a very extensive synonymy for this species, including Tanais cavolinii . Nevertheless, because type material of T. dulongii was not examined in the current study, and also because of uncertainty associated with the possible existence of cryptic species similar in appearance to T. dulongii (Graham Bird, pers. comm.), this taxon is here conservatively regarded as Tanais cf. dulongii .

Tanais dulongii occurs widely and abundantly in Europe and North America ( Sieg, 1980b). Bamber (2005) suggested that specimens of T. dulongii previously reported from the Swan estuary by Sieg (1980b) may comprise Tanais pongo , a recently described species from the Esperance region of southwestern Western Australia. However, that species clearly differs from Swan estuary specimens in a number of characteristics, including five compared to three uropod articles and much greater reduction of mandible lacinia mobilis.

Tanais cf. dulongii is likely a non-indigenous species that has been translocated to Australia by shipping. If so, it has apparently been established in the Swan estuary since at least 1943, when T. dulongii (as T. cavolinii ) was reported as common and widespread in the estuary ( Thomson 1946). Poore et al. (2002) report T. dulongii to 200 m depth in Victoria, SA and WA; however, these records could not be confirmed and are unlikely to be correct.