Ilyarachna crozetensis Kensley 1980

“Ilyarachna crozetensis sp. nov.

Description

Cephalon with lateral flanges anteriorly rounded, laterally broadly angular; dorsal convex areas with varying number of short spines (one or two in male, four to ten in female); anterior margin concave, with faint rostral point. Pereonites 1 to 3 subequal in middorsal length. Pereonite 1 slightly narrower than 2, with rounded lateral process bearing single spine. Pereonite 2 laterally rounded, with single spine. Pereonites 3 and 4 with anterolateral flange appearing as spine in dorsal view. Pereonites 5 to 7 laterally rounded. Pereonites 1 to 4 with row of fifteen to nineteen small equidistant spines on anterior margin. Pleotelson preceded by single narrow pleonal segment, triangular, dorsally convex, apex narrowly rounded.

Antennular basal segment broadest at base with single spine at inner distal angle, two spines on somewhat produced outer distal angle; second segment half length of basal segment; third segment shorter than second; flagellum of nine articles in female, twenty-two in male. Basal antennal segment with spine on rounded lateral process. Mandibular palp basal segment slightly curved, equal in length to terminal segment, second segment just less than twice length of basal segment; third segment with two elongate terminal fringed spines; incisor rounded-truncate; lacinia obliquely truncate; ten spines in spine row; molar with three or four small distal spines and three fringed setae. Maxillipedal endite with numerous elongate simple and fringed setae plus several expanded fringed spines, seven coupling hooks; epipod broadly oval, reaching beyond second palpal segment. Pereopod 1 dactylus one-quarter length of propodus; latter tapering distally; carpus equal in length to propodus, ventral margin slightly concave, with row of simple setae; ischium with two spines on dorsal margin ; four or five spines on distal margin of basis; carpus with spinose process. Pereopod 5 dactylus equal in length to propodus, carpus expanded, broader proximally than distally. Operculum in female distally rounded, median longitudinal ridge bearing row of short spine-setae. Pleopod 1 male strongly arched, outer lobes of apex parallel, distally rounded; inner lobes considerably shorter than outer, bearing several short and long setae. Uropodal basis elongate-rectangular; single ramus present.

Material

Holotype PM. Is. 1017, 1 male TL 5,6 mm, 60/DC.248 west of Ile aux Cochons, 245-250 m.

Paratype PM. Is. 1018, 1 female damaged, 60/DC.248 west of Ile aux Cochons, 245-250 m.

Paratype PM. Is. 1018, 1 female TL 8,0 mm, 46/CP.204 between Ile de la Possession and Ile aux Cochons, 375-440 m.

Paratype SAM–A16772, 1 female TL 8,1 mm, 57/DC.241 north-west of Ile aux Cochons, 195-200 m.

Paratypes USNM 173120, 2 female TL 8,1 mm 8,4 mm, 64/DC.268 west of Ile aux Cochons, 900-930 m.

Remarks

The present species from the vicinity of the Crozet Islands is a member of the Ilyarachna antarctica-nordenstami-kermadecensis complex of species. Wolff (1962: 103) used a series of twenty-one characters in separating these species which previously had been regarded as the single species, I. antarctica VanhOffen. The present material has been examined for these twenty-one characters in an attempt to establish its distinctness. Table 1 shows the distribution of these characters amongst the four species involved.

From Table 1 it is obvious that the present species has features in common with all three described species as well as features of its own, and for these reasons, a new species is erected. More material from an even wider range of localities would help to dispel the doubt that a single widespread and variable species is involved here.

Etymology

The specific name derives from the island group in which vicinity the specimens were collected.”

(Kensley, 1980: 175-178)

Ilyarachna crozetensis là một loài chân đều trong họ Munnopsidae. Loài này được Kensley miêu tả khoa học năm 1980.