Poorea johannesi, Edgar, Graham J., 2012

Edgar, Graham J., 2012, New Leptocheliidae (Crustacea: Tanaidacea: Tanaidomorpha) from Australian seagrass and macro-algal habitats, and a redescription of the poorly-known Leptochelia ignota from Sydney Harbour, Zootaxa 3276, pp. 1-37 : 23-26

Poorea johannesi n. sp.

( Figs 12–13 )

Material examined. Holotype. Male ( NMV J62794 ), 1.8 mm, Jawbone Point, Cloudy Bay, Tasmania (29.52°S 114.99°E), 2 m depth, macroalgal washings, 13 October 1999.

Paratype. Male ( NMV J62755 ), 1.9 mm (antennule, antenna, cheliped, pereopods and pleopods dissected onto microscope slide), holotype location, 13 October 1999.

Description. MALE. Body ( Fig. 12 ). Observed length 1.8–1.9 mm; robust body, about six times longer than broad; cephalothorax subrectangular, laterally slightly convex, approximately one-sixth body length; eyes large, ovoid, about one-fifths length of cephalothorax.

Pereon three-fifths total length; pereonite-1 length about one-third width; pereonites 2 and 3 similar, about 1.5 times length of pereonite-1, length about half width; pereonites 4 and 5 similar, about 1.3 times length of pereonite- 3, length about two-thirds width; pereonite-6 equal in length to pereonite-3, length about twice width.

Pleonites 1-5 similar other than declining in width posteriorly with pleonite-5 five-sixths width of pleonite-1, together one-fifth as long as body.

Pleotelson about 1.2 times length of pleonite 5; posterior margin with medium-length central seta, paired seta posterio-laterally (one minute) and another anterio-laterally.

Antennule ( Fig. 12 ). Length one-quarter length of body, article-1 about three times longer than wide, with distal group of three or four small plumose setae and two simple setae; article-2 about half length of article-1, length about 1.5 times width; article-3 triangular, length about half article-2; articles 4–8 comprising flagellum that extends just over one-third of total antennule length, article-4 length about half article-2; article-5 with groups of five or six aesthetascs proximally and distally, article-6 with five distal aesthetascs, article-7 with about four distal aesthetascs, terminal article small, with about four distal aesthetascs.

Antenna ( Fig. 12 ). Six articles, together slightly less than half length of antennule; article-1 length similar to width, lacking setae; article-2 length two-thirds width, with three small simple setae; article-3 similar in length to article-2, with distal seta; article-4 about three times longer than article-3, with four long simple setae distally and two plumose setae; article-5 about half length of article-4, length twice width, with a plumose seta and long simple seta distally; article-6 reduced to small terminal cap, with four simple setae, the longest extending about total length of antennule.

Mouthparts reduced and fused.

Cheliped ( Fig. 12 ). Length about one-third total body length; coxal sclerite small and triangular, confluent with posterior margin of cephalothorax; basis slightly longer than wide; merus triangular with three setae; carpus about one-third length of cheliped, length 1.6 times width, group of three setae on ventral margin and single distal and proximal setae near dorsal margin; propodus with fixed finger set at right angles to main cheliped axis, length about 1.8 times width, palm similar in width to carpus, fixed finger just over half length of palm, with square apophysis one-third way and smaller rounded apophysis two-thirds way along inner margin, six distal setae, small terminal spine, inner comb-like row of about 11 setae near articulation with dactylus with outermost setae longer than other setae in series; dactylus similar in length to fixed finger, inner margin smooth with six spiniform setae; unguis small, about one-fifth of total propodus length.

Pereopod -1 ( Fig. 13 ). Basis width one-quarter length, length 1.3 times length of merus and carpus together, with two setae about one-quarter distance along dorsal margin; ischium with one small ventral seta; merus onethird length of basis, with small distal seta; carpus four-fifths length of merus with about five distal setae; propodus length similar to merus and carpus together, with three long dorso-distal setae, a single ventro-distal seta, and two smaller setae near articulation with dactylus; dactylus and unguis about equal in length, together similar in length to propodus.

Pereopods 2 and 3 ( Fig. 13 ). Similar; basis width about one-third length, length 1.5 times length of merus and carpus together, with three setae about one-third distance along dorsal margin; ischium with ventro-distal seta; merus one-third length of basis, with spiniform seta distally; carpus similar in length to merus, with two spiniform setae (one minute) and two simple setae distally; propodus twice length of carpus, with spiniform seta and three simple setae three-quarters distance to distal margin; dactylus and unguis together about half length of propodus, comb-like spiniform process at base, unguis about three-fifths length of dactylus.

Pereopods 4 and 5 ( Fig. 13 ). Similar; basis width about two-fifths length, length 1.2 times length of merus and carpus together; ischium with two ventro-distal setae; merus half length of basis, with two spiniform setae distally; carpus similar in length and width to merus, with three spiniform setae and two simple setae near distal margin; propodus 1.4 times length of carpus, width two-fifths length, with two spiniform setae three-quarters distance to distal margin and three to five distal simple setae; dactylus and unguis partially fused into claw, together two-thirds length of propodus, unguis about two-fifths length of dactylus.

Pereopod 6 ( Fig. 13 ). Similar to pereopods 4 and 5 other than narrower propodus with width one-third length.

Pleopods 1–5 ( Fig. 13 ). Basal article with seta; exopod with about 18 plumose setae on inner margin, little additional gap between proximal seta and others in series; endopod with about 12 plumose setae on inner margin, plumose seta midway along outer margin.

Uropod ( Fig. 13 ). Long and slender; basal article length 1.6 times width, with three or four distal setae; exopod with short article, about half length of endopod article-1, with four long terminal setae; endopod with six articles.

Etymology. This species is named in memory of Bob Johannes for his numerous contributions to marine science and conservation across Australia and the Pacific.

Distribution. Known only from type location at Cloudy Bay, southeastern Tasmania.

Remarks. The shape of the male cheliped propodus of Poorea johannesi n. sp. is distinctive within the Australian leptocheliid fauna, with width considerably more than half length and a large square tooth on the inner cutting edge of the fixed finger. Amongst known species, male P. johannesi can be distinguished from other Poorea species by possessing only five antennule articles (c.f. six or seven) and a square-tooth on the cutting edge of the propodus.

Figures

FIGURE 12. Poorea johannesi. Cliff Head, WA. Male dorsal (holotype), antennule (A 1), antenna (A 2), cheliped (CH), pleotelson (Plt). Scale units 0.1 mm for full appendages.

FIGURE 13. Poorea johannesi. Cliff Head, WA. Male. Pereopods 1 – 6 (P 1 – P 6), pleopod (Pl), uropod (U). Scale units 0.1 mm for full appendages.