Gunenotophorus spinipes Schellenberg 1922

Gunenotophorus spinipes Schellenberg, 1922

(Figs. 97, 98)

Material examined. 1 ♀ (dissected) from Cnemidocarpa nordenskjoldi (Michaelsen, 1898), Tierra del Fuego, Argentina.

Supplementary description of female. Body (Fig. 97A) not strongly expanded, comprising cephalosome, metasome, and urosome. Bodylength 4.67 mm. Dorsal shield of cephalosome extended ventrally. Metasome unsegmented with convex dorsal margin and traces of 2 suture lines anteriorly on dorsal surface. Urosome (Fig. 97B) 6-segmented, but proximal articulations indistinct between fifth pedigerous and genital somites, and between genital and first abdominal somites. Articulation between third abdominal and anal somites also incomplete. Anal somite expanded posteroventrally into pair of bulbous processes (Fig. 97 B–D). Caudal rami tapering, slightly curved outwards in distal part; 1.8 times longer than wide (250×140 μm), slightly shorter than anal somite (255×345 μm); armed with 3 small spines and 1 seta.

Rostrum (Fig. 97E) triangular with blunt apex. Antennule (Fig. 97F) indistinctly 7-segmented; armature formula 2, 13?, 3, 1, 2, 2+aesthetasc, and 7+aesthetasc; first and second segments greatly expanded; second segment with traces of 3 possible partial articulations along posterior side; all setae short and naked. Antenna (Fig. 97G) stout, 4-segmented; proximal 3 segments (coxa, basis, and first endopodal segment) unarmed; compound distal endopodal segment 1.44 times longer than wide (62×43 μm), armed with 1 medial and 2 distal setae plus terminal claw 46 μm long.

Labrum (Fig. 97H) tapering strongly towards weak, blunt distal lobe; ornamented with numerous setules on ventral surface. Mandible (Fig. 97I) with 5 teethand 1 small proximal seta on gnathobase of coxa plus 1 small spinule located between proximal second and third teeth; basis with 1 setaon distal medial margin; exopod unsegmented, armed with 4 equal setae and 1 smaller outer seta; endopod with 1 and 5 setaeon first and second segments, respectively, outermost seta on second segment much smaller than other 4. Paragnath (Fig. 97J) as simple lobe densely covered with setules on medial surface. Maxillule (Fig. 97K) with 9 setaeon arthrite (but third proximal seta rudimentary), 1 on coxal endite, 2 on epipodite, 4 on exopod, and 4 on baseoendopod. Maxilla (Fig. 98A) 3-segmented; syncoxa with 8 setae arranged as 3, 2, and 3; basis with short, robust claw plus 2 unequal setae; endopod unsegmented, small, armed distally with 4 smallsetae. Maxilliped (Fig. 98B) unsegmented, armed with 7 setae (5 medial and 2 apical).

Legs 1–4 (Fig. 98 C–H) without inner seta on coxa. Outer seta on basis of leg 1 thickened in proximal half and thin distally. Outer seta absent on basis of legs 2–4. Exopod of leg 1 broader and slightly longer than endopod. Innerdistalspineonbasisofleg 1 small, smooth, shorter than firstendopodal segment. Leg 2 pair asymmetrical: left leg 2 endopod 3-segmented (Fig. 98D) but right leg 2 endopod unsegmented and armed with 1, 3, 1 setae (Fig. 98F); exopod more than twice as long as endopod; endopod (Fig. 98E) of left leg 2 ornamented with 3 rings of setules distally on third segment. Legs 3 and 4 displaced laterally (Fig. 97A), each with 3-segmented exopod and endopod (leg 3 endopod damaged); third exopodal segment directed laterally, slightly curved in leg 3 and straight in leg 4; endopods of legs 3 and 4 rudimentary. Armature formula for legs 1–4 as follows:

[table omitted]

Male. Unknown.

Remarks. Schellenberg (1922) described this species as an associate of Alloeocarpa incrustans (Herdman, 1886) (as A. emilionis Michaelsen) and Polyzoa opuntia Lesson, 1830 (as P. coccinea (Cunningham)) from the Strait of Magellan. Schellenberg (1922) highlighted the diagnostic features of G. spinipes which serve to differentiate it from G. globularis, as follows: endopod of maxilla with 4 setae; third exopodal segment of leg 2 with 5 inner setae and these setae are short (about equal to only half the width of the segment); endopod of leg 2 about half as long as exopod, with first and second segments each bearing an inner distal seta. These features are exhibited by our single specimen found in association with Cnemidocarpa nordenskjoldi collected off Tierra del Fuego, which appears to constitute a new host record. Comparison with Schellenberg’s original description indicates that the unsegmented endopod of leg 2 on the right side of our female is an abnormal condition.