Hexabathynella africana Cho & Schminke 2006, SP. NOV.

HEXABATHYNELLA AFRICANA SP. NOV.

Diagnosis: Parabathynellid of small size (0.75– 0.86 mm). Antennal organ protruded and bearing claw-shaped ventral seta and simple dorsal seta. Fifth antennular segment bearing two aesthetascs. Third antennular segment sexual dimorphic: male bears one seta on inner distal margin in addition to two lateral setae and one ventral seta. Distal spine of the mandibular spine row needle-shaped. Basipodal seta absent in thoracopods II–VI. Pleotelson with two setae. Uropodal exopod drawn out inner distally into a chitinous projection, with one seta at base of the projection, one dorsal subterminal seta, and one long seta on outer distal margin.

Holotype ♀, South Africa, Olifants River, 400 m above the bridge Citrusdal, Kaapprovinsie. Pit 85 cm deep, 16 m from the shore, temperature 14°C. 25 September 1973, leg. Schminke, coll. Iziko Museums of Cape Town (A45286). Allotype ♂ (A45287), same data as for holotype. Paratypes three ♀♀ and one ♂ (A45288–A45291), same data as for holotype.

Etymology: The species name refers to Africa.

Description of the female (holotype): Body (Fig. 4A, B) length 0.86 mm, approximately 16 times as long as wide. Body length of other females (paratypes) 0.84, 0.80, 0.77 mm.

Antennule (Fig. 5A) six-segmented. First segment with one seta on inner distal margin, one simple dorsal seta, and one lateral and one ventromedial plumose seta. Second segment with one group of four plumose setae, and with one seta on inner distal margin and one ventral seta. Third segment with two lateral setae and two ventral setae. Peduncle of third segment fused with fourth segment in halfway, with three simple setae. Fourth segment with one stub seta on dorsal margin, and with three plumose setae. Fifth segment with two setae on inner margin, with one aesthetasc and one simple seta dorsally, and with one lateral aesthetasc. Sixth segment with four terminal setae and three subterminal aesthetascs.

Antenna (Fig. 5E) five-segmented, 60% as long as antennule, setal formula: 0/0+0/0+0/1+0/3(1).

Labrum (Fig. 5F) flat, with eight main teeth flanked by one smaller tooth on both lateral sides.

Mandible (Fig. 5G) with incisor process of four teeth (Fig. 5H). Tooth of ventral edge triangular. Spine row consisting of one distal tooth and four proximal spines. Distal tooth narrow, needle-shaped. Palp of one segment, with one apical seta being three times as long as palp.

Maxillule (Fig. 5I) two-segmented. Proximal segment with four setae on inner distal margin. Distal segment with three terminal claws, with two claws and one seta on inner edge and three simple setae on outer distal margin.

Maxilla (Fig. 5J) three-segmented, setal formula 2-4-13.

Thoracopods I–IV (Figs 5K–M, 6A–C) increasing in length posteriorly. Thoracopods IV–VI equal in length. Protopods of thoracopods I–VI each bearing one epipodite. Only thoracopod I (Fig. 5K) bearing one basipodal seta. Exopod of thoracopod I one-segmented, with one terminal seta. Exopod of thoracopods II–VI two-segmented, with one terminal seta on distal segment, and one dorsal and one ventral seta on proximal segment. Endopodite of thoracopods I–VI four-segmented, setal formulae: thoracopod I 1+0/0+1/0+0/2(1), thoracopods II–VI 0+0/0+1/0+0/1(0), thoracopod VIII (Fig. 6D) tiny.

First pleopod (Fig. 6F) in form of a seta.

Uropod (Fig. 6G, I) bearing three spines on inner distal margin of sympod. Distal spine 2.5 times as long as proximal spine. Endopodite approximately 50% as long as sympod, drawn out distally in slightly curved spur, with one dorsal plumose seta and two simple setae at base of spur. Exopod (Fig. 6H) as long as endopod, drawn out inner distally into a chitinous projection, with one seta at base of projection, one dorsal subterminal seta and one long seta on outer distal margin.

Pleotelson (Fig. 6G, I) with two setae at base of fucal rami. Anal operculum projected, with round tip.

Furcal rami (Fig. 6G, I, J) as long as wide, with three spines and two dorsal setae of equal length. Outer seta is plumose.

Description of the male (allotype): The male differs from the female only in body length, second antennular segment and thoracopod VIII. Body length 0.84 mm. Body length of other male (paratype) 0.74 mm.

Second antennular segment (Fig. 5B–D) with one group of four plumose setae, one ventral seta and antennal organ on inner distal margin. Antennal organ (Fig. 5C, D) represented by a protrusion bearing claw-shaped ventral seta and simple dorsal seta.

Third antennular segment (Fig. 5B) with one seta on inner distal margin in addition to two lateral setae and with one ventral seta.

Thoracopod VIII (Fig. 6E) massive. Penial region three-lobed. Middle lobe with six to seven teeth distally. Epipodite absent. Basipodite with one seta at base of endopodite. Inner margin of basipodite drawn out in a chitinous projection. Exopodite triangular, bottle-shaped, bearing two tiny spines in region of bottleneck and four distal denticles. Endopodite 1.5 times as long as basipodite, drawn out in round tip. With two setae at base of tip.