Hexabathynella schrieveri, Cho & Schminke, 2006

Cho, Joo-Lae & Schminke, Horst Kurt, 2006, A phylogenetic review of the genus Hexabathynella Schminke, 1972 (Crustacea, Malacostraca, Bathynellacea): with a description of four new species, Zoological Journal of the Linnean Society 147 (1), pp. 71-96 : 79-83

HEXABATHYNELLA SCHRIEVERI SP. NOV.

Diagnosis: Parabathynellid of small size (1.10– 1.20 mm). Antennal organ slightly protruded and bearing two setae of different lengths, but of similar shape. Pleopod absent. Pleotelson without setae. Uropodal exopod bearing two setae. Inner seta of them is serrate in its medial part.

Holotype ♀ Brazil, Sand interstitial of Jola de San Martin, Cataratas do Iguaçu , Paraná. Pit 40 cm, temperature 21°C, coll. 18 September 1968 by W. Noodt, coll. Museu de Zoologia , Universidade de Sao Paulo, Brazil ( MZUSP 16481 ) . Allotype ♂ ( MZUSP 16482 ), same locality data as for holotype . Paratype one ♂ ( MZUSP 16483 ) and one ♀ ( MZUSP 16484 ), same locality data as for holotype .

Etymology: The species is named after Dr G. Schriever (Hohenwestedt, Germany), who has worked on abyssal interstitial copepods.

Description of the female (holotype): Body length 1.1 mm, approximately 11 times as long as wide. Head as long as length of one to three segments, 40% longer than width.

Antennule ( Fig. 7A ) six-segmented. First segment with one seta on inner distal margin, one simple dorsal seta, and one lateral, dorsal and ventromedial plumose seta. Second segment with one group of four plumose setae and one simple seta on inner distal margin. Third segment with one simple seta on inner distal margin, three lateral setae and one ventral seta. Peduncle on third segment fused with fourth segment at midpoint, 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 two aesthetascs and one simple dorsal seta, and with one lateral aesthetasc. Sixth segment with four terminal setae and three subterminal aesthetascs.

Antenna ( Fig. 7B ) five-segmented, 40% as long as antennule, setal formula: 0/0+0/0+0/1+1/3(1).

Labrum ( Fig. 7C ) flat, with eight main teeth, flanked by one smaller tooth on each side.

Mandible ( Fig. 7E ) with incisor process of four teeth. Tooth of ventral edge triangular. Spine row consisting of five spines. Palp of one segment with one apical seta being three times as long as segment.

Maxillule ( Fig. 7F ) two-segmented. Proximal segment with four setae on inner distal margin. Distal segment with three terminal claws, two claws on inner edge, and three simple setae on outer distal margin.

Maxilla ( Fig. 7G ) three-segmented, setal formula 2-4-13.

Thoracopods I–IV ( Figs 7H–J , 8A–C ) increasing in length, and bearing one basal seta and one epipodite. Exopod of thoracopods I one-segmented, with one terminal seta. Exopod of thoracopod II–VI twosegmented, with two setae on proximal segment, and with one terminal seta on distal segment. Endopod of thoracopods I–VI four-segmented, setal formulae: thoracopod I 1+0/1+1/1+0/3(1), thoracopods II–VI 0+0/0+1/0+1/1(0).

Thoracopod VIII ( Fig. 7M ) tiny and sharply pointed.

Pleopods absent.

Uropod ( Fig. 8D–F ) bearing six to seven spines on inner distal margin of sympod. Distal spine 1.5 times as long as proximal spines. Endopod 50% as long as sympod, drawn out distally in slightly curved spur, with three setae at base of spur. Exopod ( Fig. 8F ) as long as endopod, with two terminal setae. Inner seta one third as long as, but thicker than, outer one, and with serrate medial part.

Pleotelson without setae. Anal operculum projected, triangular.

Furcal rami ( Fig. 8D, E ) as long as wide, with three spines and two dorsal setae.

Description of the male (allotype): The male differs from the female only in body length, second antennular segment and thoracopod VIII. Body length 1.05 mm, approximately 12 times as long as wide.

Second antennular segment with a group of four plumose setae and antennal organ on inner distal margin. Antennal organ ( Fig. 7D ) represented by a slight protrusion bearing two setae of similar form. Dorsal seta two-thirds as long as ventral one. Both setae subdivided at base and with sharply pointed, feathered distal parts.

Thoracopod VIII ( Fig. 7K, L ) massive. Penial region three-lobed. Middle lobe with three teeth. Inner lobe with seven teeth in circular arrangement. Epipodite absent. Basis with seta at base of endopod. Inner margin of basipod drawn out into a chitinous projection. Exopod bottle-shaped, bearing two tiny setae on neck. Endopod as long as basipod, bearing two terminal setae of similar size.

Figures

Figure 7. Hexabathynella schrieveri sp. nov. A, right antennule ♀ (dorsal). B, right antenna ♀ (dorsal). C, labrum (ventral). D, antennal organ of right antennule ♂ (ventral). E, left mandible ♀ (dorsal). F, right maxillule ♀ (dorsal). G, left maxilla ♀ (dorsal). H, left thoracopod I ♀ (frontal). I, left thoracopod II ♀ (frontal). J, left thoracopod III ♀ (frontal). K, right thoracopod VIII ♂ (frontal). L, right thoracopod VIII ♂ (ventral). M, thoracopod VIII ♀ (outer lateral). Scale bar = 0.05 mm. The figures are based on the holotype (♀) and the allotype (♂).

Figure 8. Hexabathynella schrieveri sp. nov. A, right thoracopod IV ♀ (frontal). B, right thoracopod V ♀ (frontal). C, right thoracopod VI ♀ (frontal). D, pleotelson, furcal rami, and uropod ♀ (outer lateral). E, pleotelson, furcal rami, and uropod ♀ (dorsal). F, uropodal exopod ♀ (dorsal). Scale bar = 0.05 mm. The figures are based on the holotype (♀) and the allotype (♂).