Atrophia glacialis (Sars G. O. 1900)

Lubbockia glacialis Sars, 1900

Lubbockia glacialis Sars, 1900:114–118, pl. 33: figs. 1–15.

MATERIAL STUDIED (Tables 1, 2).—NE PACIFIC: 6 females, 1.58–1.71 mm ( = 1.63 mm), NP 6 et al., USNM 168513–168515; 1 juvenile, stage V, 1.20 mm, NP 4; 1 juvenile, stage IV, 1.03 mm, NP 27.

DISTRIBUTION.—Arctic Ocean (Sars, 1900; Grice, 1962; Johnson, 1963; Minoda, 1967; Heron and English, in prep.) and the North Pacific Ocean (Tables 1, 2; Minoda, 1971). Hardy and Gunther (1935) reported L. glacialis from the Antarctic, but with some doubt.

Lubbockia species

STAGE V.—Seven specimens, 1.37–1.44 mm, ( = 1.40 mm) from the northeast Pacific (Tables 1, 2). Body proportions (Figure 17a) and appendages are similar to those in L. minuta and L. glacialis. Areas of dense refractile points on fourth and fifth urosomal segments separate this species from the others. These specimens were larger than the juveniles of L. minuta and L. glacialis from the northeast Pacific, but were approximately the same size as L. glacialis juveniles from the Arctic Ocean (Heron and English, in prep.).

STAGE IV.—A specimen (1.14 mm) (Table 2) was compared with similar size specimens of Arctic L. glacialis, and each urosomal segment of this undescribed species appeared more robust and wider in relation to the length (Figure 17b).

Lubbockia glacialis Sars, 1900

Lubbockia glacialis Sars, 1900, pp. 114–118, pl. 33: figs. 1–15.

MATERIAL STUDIED.—1 male from sample 3; body length 2.21 mm.

MALE.—Body (Figure 20) elongate, similar to Sars’ (1900) description of female, except male urosome longer than prosome. Rostrum a small, rounded protrusion between bases of 1st antennae, not delimited ventrally from tergum of cephalosome. Prosome with greatest depth at junction of first 2 segments.

Urosome 6-segmented, each segment with smooth posterior margins. Fifth and anal segments with lateral margins slightly concave.

Caudal rami about same length as genital segment. All caudal setae, except 2 on left ramus, were missing from specimen.

First antenna (Figure 21a) with 4 distinct segments. Faint line suggesting coalescence on proximal third of segment III corresponds to segmentation between segments III and IV of female. Fourth segment of male 1st antenna corresponds to segments V, VI, and VII of female. Armature may be incomplete on this damaged specimen: segment I–3; II–2, 1 esthete; III–1, 2 esthetes; IV–7, 1 esthete. Segment IV also with a few spinules. Longest esthete, on segment III, almost twice the length of 1st antenna.

Second antenna (Figure 21b) subprehensile, 3-segmented. Basal segment unarmed; 1 seta on short 2nd segment. Distal segment with terminal grouping of 7 setae, 1 three times the length of the remaining 6, 1 of which is plumose. Inner surface of 3rd segment with patches of hairs and 1 small spine near base of long seta; 2 setae on outer margin.

Mandible and first maxilla reduced to vestiges, represented only by the bases; each with undefined margins.

Second maxilla (Figure 21c) with 2 terminal spines, 1 nude and 1 with unilateral row of hairs; 1 seta on lateral margin. Slightly sinuate spine, with unilateral patches of hairs, on small lobe protruding subapically. Segmentation as illustrated by Sars (1900, pl. 33, fig. 7) for this appendage could not be discerned on the IPHC male.

Maxilliped (Figure 21d) 3-segmented; 2nd segment with spine and graduated row of coarse spinules on medial margin, followed by row of rugose striations. The recurved claw tapers to slight distal expansion.

Legs 1, 3, and 4 with trimerous rami, as described by Sars (1900) for female; leg 2 missing from IPHC specimen. Armature of legs 1 and 3 similar to Sars’ description for female, except the hyaline flange of spines finely serrate rather than smooth. Right leg 4 abnormal; differed by having 3 instead of 2 spines on lateral margin of 3rd exopod.

Leg 5 (see Figure 20a) similar to female, free segment elongate, extending two-fifths the length of genital segment; armature consists of 2 lanceolate setae, terminal seta about three times the length of lateral seta.

Leg 6 (Figure 21e) probably represented by small triangular sclerotized ridge on ventrolateral posterior margin of genital segment, bearing 1 setule.

DISTRIBUTION.—Sars (1900) recorded “some few” female L. glacialis from the Norwegian North Polar Expedition. He described a female measuring 2.45 mm. Olson (1949) recorded 1 female, 1.30 mm, from 0–800 m off the Oregon coast, but his description and illustrations suggest the specimen was L. minuta Wolfenden. Grice (1962) listed 1 specimen, and Johnson (1963) listed 1 specimen in each of 2 samples from the high North Polar Basin.