Aponema martinezi, Miljutin & Miljutina, 2009

Miljutin, Dmitry M. & Miljutina, Maria A., 2009, Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species *, Zootaxa 2096 (1), pp. 137-172 : 140-145

Aponema martinezi sp. n.

( Figs 2–4 , Table 2)

Type material: Collection number MNHN-BN490 . Holotype: one male . Paratype: one female .

Locality: Tables 1, 2.

Etymology: In honor of Dr. Prof. Pedro Martínez Arbizu (German Centre for Marine Biodiversity Research (DZMB), Wilhelmshaven, Germany).

Measurements: Table 2.

Description of male: Very small nematode. Body cylindrical, with slightly narrowed anterior end and conical tail. Cuticle annulated along whole body except cephalic capsule. Cuticular annuli strongly pronounced, each about 1 µm width. Cuticle thickness approximately 0.3 µm at level of cephalic capsule and approximately 1 µm at rest body. Somatic setae not found. Sensilla of cephalic end arranged in 2 rings spaced far apart: 6 very short (0.4 µm) outer labial setae at level of cephalic tip and 4 submedian cephalic setae (0.6 µm) near posterior border of cephalic capsule. Amphid monospiral, round, with fine but distinct sclerotized margins, approximately 1/2 of c.b.d. in its diameter. There are 10 cuticular annules between anterior rim of amphid and cephalic capsule. Buccal cavity narrow, distinguished from rest, posterior pharynx by its thicker cuticular walls of its internal lumen. One small dorsal sclerotized tooth visible at its medium part. Pharynx cylindrical but possessnig a well-developed terminal oval bulb approximately 75% of c.b.d. in its width. Single pair of plasmatic inclusions visible on optical transversal section at level of middle of pharyngeal bulb. Nerve ring at a distance 2/3–3/4 of pharyngeal length from anterior end. Cellular body of renetta located at level of beginning of intestine. Cardia large, triangular, approximately 1/2 of c.b.d. in its width. Reproductive system monorchic, with single outstretched testis lying to the left of intestine. Testis gradually widening to vas deferens without forming morphologically distinct border. Large nuclei of spermatids visible in latter. Spicules long and thin, curved, with feebly marked knob at its distal end. Gubernaculum in shape of a curved, thin rod. Distal end of gubernaculum directed anteriorly, and possessing a long, curved apophysis of similar thickness, distal end of which being directed dorsally. Supplementary organs not visible. Whole reproductive system occupies approximately 45% of total body length. Tail conical. Three cellular bodies of caudal glands located close to anus. Outlet of caudal glands visible in caudal tip.

Female: Females very similar to males in most parameters, however amphids being smaller (44% of c.b.d.). Reproductive system very short, didelphic, amphidelphic, with outstretched ovaries. Whole reproductive system occupying approximately 30% of total body length. Posterior branch of reproductive system 2.5 times longer than anterior one. There are no morphologically distinct borders between ovaries, oviducts and uterus. Most of uterus also located in posterior branch. One big, long oocyte (35 x 9 µm) visible in uterus. One oval spermatozoon 13 x 6 µm in size situated in uterus opposite vulva. Intestine pushed to dorsal side by short anterior ovary, whereas longer posterior one lying to the left of intestine. Every ovary containing one mature elongated oocyte. No vulvar glands seen.

Abundance: The density of this species did not exceed 1 ind/ 10cm 2 and relative abundance within the nematode community was about 1% at the stations where it was found.

Differential diagnosis: There are 7 valid species of Aponema at present ( Kovalyev & Miljutina 2008). A. martinezi sp. n. differs from most Aponema species by possessing non-set-off head and amphids located quite a far from the non-annulated cephalic capsule (there are 10 cuticular annules between anterior rim of amphid and cephalic capsule). Only two species possess these features: A. minutissima Kovalyov et Miljutina, 2008 and A. nanum ( Blome, 1982) (see Kovalyev & Miljutina 2008). The new species also bears the cephalic sensilla of two rings of about the same length, like A. minutissima , and their total body length are similar (260–270 µm in A. martinezi sp. n. vs. 209–424 µm A. minutissima ). However, A. martinezi sp. n. differs from these two species by possessing a gubernaculum with apophysis, whereas apophyses have been not detected in A. minutissima and A. nanum .

Figures

FIGURE 2. Aponema martinezi sp. n., male, holotype. A, total view; B, posterior end; C, anterior end. Scale bars: A = 50 µm; B, C = 20 µm.

FIGURE 3. Aponema martinezi sp. n., male, holotype, light micrographs. A, anterior end; B, beginning of testis (marked by arrow); C, anal region, optical section at level of distal part of spicule; D, anal region, optical section at level of gubernaculum. Scale bars: A, B = 20 µm; C, D = 10 µm.

FIGURE 4. Aponema martinezi sp. n., female, paratype. A, total view; B, anterior end. Scale bars: A = 50 µm; В = 20 µm.