Tanzanapseudes levis, Stępień, Anna & Błażewicz-Paszkowycz, Magdalena, 2009

Stępień, Anna & Błażewicz-Paszkowycz, Magdalena, 2009, Two new species of the genus Tanzanapseudes Băcescu, 1975 (Tanaidacea: Apseudomorpha: Tanzanapseudidae) from mid-west Australia, Zootaxa 2283, pp. 40-50 : 47-50

Tanzanapseudes levis n. sp.

( Figures 4–5 )

Material examined: Holotype, female with brood pouch ( WAM C4278, partially dissected on slides C42781), NIN 9, Edge of Lagoon, 21°51.399' S 114°00.152' E, coral rubble, depth 4– 5 m.

Etymology: levis , latin for smooth. The name refers to the smooth anterolateral process and distal processes of pleotelson. Those processes are spinose in the others members of the genus Tanzanapseudes .

Diagnosis: Pereonites without setae or spines dorsally. Anterolateral processes on side of rostrum and distal processes on telson smooth. Antennule article 1 setose distally. Chela slender, more than three times as long as wide; cheliped carpus distal margin smooth.

Description: Female with brood pouch (holotype): Body ( Fig. 4 ) 1.95 mm long, 1.4 times as long as wide. Cephalothorax 35% of body length, with four spinose lateral processes and pair of smooth anterolateral processes. Rostrum apparently broken off. Eyes with pigment. Pereonites without ornamentation dorsally; each pereonite with one spinose lateral processes on each side. Pleon 15% of body length, the pleonites and pleotelson fully fused, with three pairs of spinose lateral processes and one pair of smooth distal processes.

Antennule ( Fig. 5 A) basal article three times as long as wide, with three teeth on inner and two on outer margin and numerous pinnate setae distally; article 2 little longer than wide, with one simple and three pinnate setae distally, article 3 about twice as long as wide; accessory flagellum one-articled, with one simple and three pinnate setae distally; main flagellum twice as long as accessory flagellum, of one-article resulting from fusion of three articles (indicated by two broken setae at one-third length and two simple setae and one aesthetasc at two-thirds length); flagellum tipped by three simple and two pinnate setae and one aesthetasc.

Cheliped ( Fig. 5 B): basis twice as long as wide, with minute spines dorsally and two pinnate setae distoventrally; merus 0.9 times as long as wide, with long, plumose seta on ventral margin; carpus about twice as long as wide, with four plumose setae on ventral margin and two short setae dorsally; chela slender and 1.2 times as long as carpus, with short seta at middle and near dactylus insertion; fixed finger with numerous setae along inner, ventral and distal margins, inner margin with small blunt and irregular denticles; dactylus inner margin serrated. Exopod absent.

Pereopod 1 ( Fig. 5 C) basis about 1.5 times as long as wide, with one seta ventrally; ischium with one seta; merus twice as long as carpus, with one seta distoventrally and two short setae distodorsally; carpus with two setae ventrally and three setae distodorsally; propodus 3.5 times as long as wide, with four (on right) or three (on left) spiniform setae ventrally and one simple and one pinnate seta dorsally and two short plumose setae distodorsally; dactylus with two small setae on dorsal margin; unguis subequal in length to dactylus. Exopod three-articled (not drawn), terminal article with four plumose setae.

Pereopod 2 ( Fig. 5 D) similar to pereopod 1, but propodus with three spiniform setae ventrally and dactylus with one seta dorsally.

Pereopod 3 ( Fig. 5 E) similar to pereopod 2.

Pereopod 6 ( Fig. 5 F) similar to pereopod 3; but merus and carpus with one simple seta distodorsally, propodus with four plumose setae distodorsally, dactylus with two setae dorsally.

Uropod ( Fig. 4 ). Endopod broken; exopod two-articled.

Distribution: The species is known only from the type locality—Ningaloo, mid-western Australia from 2–3 m depth.

Remarks: Tanzanapseudes levis n. sp. is the only member of the genus in which the processes on each side of the rostrum and on the telson are simple.

Discussion: Băcescu (1975) remarked that species of Tanzanapseudes are difficult for determination as ‘they are completely covered by mud and detritus’. Attempts to brush off this material usually cause the lateral processes and the dorsal ornamentation of the pereonites to break off. This feature of dorsal ornamentation seems to be consistent within the species and a reliable character for distinguishing between the species. The most ornamented species is T. polynesiensis bearing usually more than 6 minute spines on each pereonite and four setae on the fourth pereonite. Tanzanapseudes elegans has four rows of tubercles running from the carapace to the last pereonite. Roman (1976) has not defined those structures, but because a seta arises from three of them, it can be assumed that they are the basal ‘articulation’ of a broken seta. A clear pattern of spines and setae on the pereonites is observed in T. nieli (pereonites 1–3 with two pair of minute spines, pereonites 4–5 with a pair of minute spines, pereonites 3–5 with a pair simple setae; see Fig. 1 ). The remaining species have the simplest ornamentations, T. longiseta and T. langi bearing a pair of long or short setae (respectively), while T. levis lacks any dorsal ornamentation.

Other taxonomically useful characters include: the proportion of the antennule first article (long and slender in T. elegans ) and the character of the processes on the sides of the rostrum (short in T. polynesiensis and smooth in T. levis ). The distal processes on the pleotelson are usually spinose but in the case of T nieli and T. langi they are smooth along the outer margin; in T. levis both margins of those processes are smooth.

A character that should be treated with caution is the number of spiniform setae on the propodus of the pereopods. In T. levis the left and right pereopod 1 bear a varying (three or four) number of spiniform setae.

Similar variation was observed in the last three pairs of pereopods of juvenile and premature specimens of T. nieli .

Figures

FIGURE 1. Tanzanapseudes nieli n. sp., neuter, body dorsally. Scale bar equals 0.1 mm.

FIGURE 4. Tanzanapseudes levis n. sp., female, holotype, body dorsally. Scale bar equals 0.1 mm.

FIGURE 5. Tanzanapseudes levis n. sp., female, holotype A) antennule; B) cheliped; C) pereopod 1; D) pereopod 2; E) pereopod 3; F) pereopod 6. Scale bars equal 0.1 mm.