Cervonema proberti, Leduc, 2012

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 : 14-19

Cervonema proberti sp. nov.

urn:lsid:zoobank.org:act:0635B2CB-1114-4399-A3E6-DC0F53832755

Figs 7-8 , Table 2

Etymology

This species is named after Dr. P. Keith Probert.

Material examined

Holotype

Ƌ, collected 5 Oct.2001,Chatham Rise crest (350 m water depth), 43.4333°S, 178.5000°E.Characteristics of surface sediment layer (0-5 mm): mostly fine sand (35.7%), silt/clay (33.0%), and very fine sand (23.5%); calcium carbonate content: 40.5%; total organic matter content: 4.5%; chloroplastic pigment concentration: 3359 ng /gDW sediment (NIC 84442).

Paratypes

1 Ƌ, 3 ♀♀, same data as holotype (NIC 84443).

Description

Males

Body cylindrical, tapering towards both extremities. Cuticle faintly striated, no lateral differentiation. Somatic setae short and sparse, in four dorso- and ventro-lateral longitudinal rows. Epidermal glands associated with somatic setae visible as clear, oval areas underneath cuticle ( Figs 7C , 8A ). Head set-off by constriction at level of amphids. Inner labial papillae indistinct, six outer labial setae, and four longer cephalic setae, the latter two almost at same level. Cephalic setae 1.6-2.0 times longer than outer labial setae. Amphideal fovea spiral, 5 turns, 0.5-1.0 head diameter from anterior. Small buccal cavity, cupshaped. Pharynx with rounded or oval terminal bulb. Nucleus of dorsal pharyngeal gland conspicuous. Cardia short. Nerve ring near middle of pharynx length. Secretory-excretory pore slightly posterior to nerve ring. Cellular body of ventral gland slightly posterior to cardia. Intestine wall consisting mostly of cells containing colourless granules, interspersed with clusters of clear globular inclusions ( Fig. 8B ).

Reproductive system diorchic, opposed, outstretched. Anterior testis to left of intestine, posterior testis to right of intestine. Oval-shaped sperm cells with lenticular nuclei situated peripherally ( Fig. 7D ). Two pairs of ejaculatory glands present. Spicules paired, equal, slightly arcuate, 0.7-0.9 abd long, proximal end slightly cephalated, gradually tapering towards distal end. Gubernaculum not observed. Rectal gland surrounds spicules. Eight small, tubular pre-cloacal supplements, often difficult to distinguish, one precloacal seta. Tail conico-cylindrical, with several short caudal setae and three short terminal setae. Three caudal glands and spinneret present.

Females

Similar to males, but with slightly larger maximum body diameter, amphideal fovea smaller, 4-5 turns, slightly longer tail. Reproductive system didelphic, opposed, outstretched, with anterior branch to left of intestine and posterior branch to right of intestine. Vulva slightly pre median. Granular vaginal glands present, pars proximalis vaginae surrounded by constrictor muscle.

Diagnosis and relationships

Cervonema proberti sp. nov. is characterised by body length 1043-1144 μm, amphideal fovea with 5 turns and <1 head diameter from anterior end, cephalic setae 1.6-2.0 times longer than outer labial setae, sperm cells with lenticular nuclei, 8 small pre-cloacal supplements, and tail 4.5-5.9 abd.

Cervonema proberti sp. nov. can be distinguished from most other species of the genus by the amphid <1 head diameter from anterior, compared to> 1 head diameter from anterior in most species (except C. hermani Chen & Vincx, 2000 , C. chilensis Chen & Vincx, 2000 , and C. proximamphidum Tchesunov, 2000 ). C. proberti sp. nov. can be distinguished from C. hermani , C. chilensis , and C. proximamphidum by cephalic setae conspicuously (1.6-2.0×) longer than outer labial setae (almost equal in length in C. hermani , C. chilensis , and C. proximamphidum ), and nucleated sperm cells (no nuclei in C. hermani , C. chilensis , and C. proximamphidum ). C. proberti sp. nov. is also characterised by a shorter tail than C. hermani (4.5-4.8 vs. 5.7-9.3 abd). C. proberti sp. nov. resembles Cervonema sp. B described by Barnes et al. (2012) based on one female specimen from the Korean west coast. My female specimens share several traits, including amphid close to anterior end, well-developed pharyngeal bulb with conspicuous pharyngeal gland nucleus, and cephalic setae longer than the outer labial setae. My specimens, however, have shorter body length (1183-1397 vs. 1727 μm), and greater ratio of cephalic setae length to outer labial setae length (1.6-2.0 vs. 1.3). Male specimens are required before the identity of the Korean species can be determined with certainty.

NS = not specified

1 Not noted in original description but described by Lorenzen (1981).

2 Micrograph in original description suggests presence of jointed outer labial setae, but they were not noted in the text ( Hope & Zhang 1995, fig. 19).

Discussion

A total of 17 Cervonema species (including the three new species described herein) have been described so far. Differentiating between Cervonema species can be difficult due to relatively subtle differences in morphology. A summary of key morphological features of all known Cervonema species is provided to help identification ( Table 3).

Figures

Fig. 7. Cervonema proberti sp. nov. A. Ƌ anterior body region. B. ♀ anterior region. C. ♀ tail. D. Sperm cells. E. Ƌ posterior body region, showing copulatory apparatus. Scale bar: A, B, and C = 25 μm; D = 20 μm; E = 35 μm.

Fig. 8. Cervonema proberti sp. nov. A. ♀ head, showing glands. B. Entire Ƌ. C. ♀ reproductive system. Arrows point to clear globular inclusions in intestine wall. Scale bar: A =20 μm; B and C = 65 μm.