Kenyanema monorchis Muthumbi et al., 1997

Leduc, Daniel, 2012, Deep-sea nematodes (Comesomatidae) from the Southwest Pacific Ocean: five new species and three new species records, European Journal of Taxonomy 24, pp. 1-42 : 36

Kenyanema monorchis Muthumbi et al., 1997

Figs 18-19 , Table 6

Material examined

3 ƋƋ and 3 ♀♀, collected 6 Apr. 2007, southern flank of Chatham Rise (1240 m water depth), 44.4864°S, 177.1407°E. Characteristics of surface sediment layer (0-5 mm): mostly silt/clay (82.9%), with very fine sand (10.2%), and fine sand (8.4%); calcium carbonate content: 38.4%; total organic matter content: 1.9%; chloroplastic pigment concentration: 3501 ng /gDW sediment (NIC 84451).

Description

Males

Body cylindrical, tapering towards anterior extremity. Cuticle with transverse rows of dots, lateral differentiation consisting of larger, irregularly-spaced dots. Eight rows of short, sparse somatic setae. Head set-off by constriction immediately posterior to cephalic setae. Inner and outer labial sensillae indistinct, four cephalic setae. Amphideal fovea spiral, 2.5 turns, located at level of cephalic setae. Buccal cavity tubular, 4 μm deep, 1 μm wide, surrounded by pharyngeal muscles. Marginal tubes beginning from base of stoma. Pharynx gradually swelling, not forming true bulb, cardia short. Nerve ring near middle of pharynx, situated anteriorly to secretory-excretory pore. Cellular body of ventral gland near level of cardia. Intestine wall with numerous small, colourless granules, and clusters of clear circular inclusions, mostly in posterior portion of intestine ( Fig. 18E ).

Reproductive system monorchic with outstretched anterior testis to left of intestine. Mature sperm cells large, oval-shaped, up to 30 μm long and 13 μm wide. Spicules paired, equal, arcuate, 1.6-1.8 abd long, with swollen proximal end and central internal cuticularisated projection (lamella) extending from proximal end over one fifth of spicule length. Gubernaculum with pair of straight caudal apophyses. Rectal gland surrounds posterior portion of spicules and gubernaculum. Two to three small tubular precloacal supplements, one pre-cloacal seta. Tail conico-cylindrical with swollen tip, several short caudal setae and three short terminal setae. Three caudal glands and spinneret.

Females

Similar to males, but with slightly greater maximum body diameter, amphideal fovea slightly smaller, 2.0-2.25 turns. Reproductive system didelphic, opposed, outstretched, with sperm distributed over uteri and with branches either to the right or left of intestine, but always on opposite sides. Vulva slightly post median.

Discussion

My specimens closely resemble the description of Kenyanema monorchis Muthumbi et al., 1997 based on specimens from the Indian Ocean (500-1112 m water depth). My specimens, however, have a smaller buccal cavity (4 vs. 8 μm deep) and are characterised by the presence of 2-3 pre-cloacal supplements. No pre-cloacal supplements were observed in the original description of this species, but may have been overlooked. This is the first record for this genus outside the type locality.

Figures

Fig. 18. Kenyanema monorchis Muthumbi et al., 1997. A. Anterior region of ♀; B: lateral surface view of Ƌ head. C. Lateral view of Ƌ head (cross-section). D. Posterior region of Ƌ showing copulatory apparatus. E. ♀ gut, posterior body region. F. ♀ tail. Scale bar = 25 μm.

Fig. 19. Kenyanema monorchis Muthumbi et al., 1997. A. Entire Ƌ. B. ♀ reproductive system. Scale bar = 100 μm.