Polkepsilonema
Polkepsilonema Verschelde & Vincx, 1993 (ref. ID; 883 original paper)
ref. ID; 883
Diagnosis
The genus differs from all other Epsilonematid genera by its large number of subcephalic setae. Polkepsilonema gen. n. resembles Pternepsilonema gen. n. but can be distinguished from it by the location of subcephalic setae (at posterior edge in Pternepsilonema) and by shape of ambulatory setae (bent setae with single distal tip in Polkepsilonema, straight setae with double tip in Pternepsilonema); Polykepsilonema is more robust then Pternepsilonema. (ref. ID; 883)
Description
Body epsilon-shaped. In males, maximum body diameter 1.5 to 1.6 times the minimum body diameter; in females, twice. Ambulatory setae apparently in seven rows: external subventral row on each side of body with a field of ambulatory setae in between. Ambulatory setae slender, bisinuous, with slightly bent distal tip. Head capsule with four cephalic and fourteen to eighteen subcephalic setae; eight to ten of them situated on anterior half of rostrum, in front of fovea amphidialis. Large amphids may show sexual dimorphism. (ref. ID; 883)
Etymology
This genus has been named in honour of Prof. Dr. P. Polk, coordinator of the Kenyan-Belgian project in Marine Sciences. (ref. ID; 883)
- Polkepsilonema mombasae Verschelde & Vincx, 1993 (ref. ID; 883 original paper)
Polkepsilonema mombasae Verschelde & Vincx, 1993 (ref. ID; 883 original paper)
Diagnosis
Polkepsilonema mombasae sp. n. is characterized by its heavily cuticularized and broad body annules, each with a row of large vacuoles and ridges, and by large dorsal thorns in region of ventral body curvature. Males characterized by their open loop-shaped amphid, two types of ambulatory setae and by heavy copulatory and precloacal thorns. Females show a conspicuous vulva, dorsally bent posterior ovary and ventrally bent anterior ovary with extending yolk. (ref. ID; 883)
Descriptions
Type species. (ref. ID; 883)
Male: Body epsilon-shaped; 112 to 122 broad annules with thick cuticle, ornamented with a row of large vacuoles, with ridges in between. Body annules of pharyngeal region 4-5 µm broad, 2.5 µm between dorsal and ventral curvature, 4 µm behind ventral curvature and 4.5 µm at tail Inversion in direction of body annules, located ventrally in dorsal (i.e. anterior) curvature and dorsally in the ventral (i.e. posterior) curvature; exact location difficult to see. Somatic setae in five longitudinal rows. Ambulatory setae apparently in seven longitudinal rows; SEM-pictures, however, reveal that ambulatory setae are arranged in two external subventral rows with a field of setae in between. Setae of external rows shaped differently of those in between; They look like firm supporting setae, but are considered to be ambulatory setae because of the slightly bent basis and distally bent tips; setae of internal rows (field) slim and bent twice (bisinuous), once at basis and a second time in the middle; they also have a distally bent tip. Four pairs of short, slender supporting setae. Seven (pairs of) heavy copulatory thorns, ventrally between posterior ambulatory setae; usually in closely apposed pairs, but first and last few can be single. Subventrally, next to large copulatory thorns. Three (sometimes four or six) single, ventral, large precloacal a thorns. Subventrally situated to these, three to five pairs of small thorns. Three pairs of paracloacal setae. Cloacal cuticle hardly rising (1 µm) above surrounding body annules (tiny anal tube). Tail with two subventral, and one subdorsal pair of somatic setae. One pair of lateral somatic setae on non-annulated tail-tip. From dorsally to subdorsally in region of posterior (ventral) body curvature, a large number of heavy thorns of different sizes (max. 13 µm). Ventral field of hairlike spines, extending from annule 20 to first ambulatory setae. Head capsule (i.e. rostrum) heavily cuticularized; four cephalic and fourteen to eighteen (mostly sixteen) subcephalic setae, eight of the latter in front of amphid on anterior half of rostrum. Subdorsally shifted, conspicuous amphid with open loop-shaped, wide fovea amphidialis; one or two pairs of subcephalic setae located between two ends of loop. Buccal cavity with distinct dorsal tooth and slightly smaller ventral tooth. Pharynx with muscular endbulb. Nerve ring situated anterior to the endbulb. Cardia unclear. Testis extending to anterior body curvature, at the right of intestine. Vas deferens broad. Spicules arcuate, short; capitulum club-shaped; broad velum. Gubernaculum slim, inconspicuous. Tail with six annules. Tailtip with three times three pores. (ref. ID; 883)
Female: Body, annules, ornamentation and pattern of somatic setae similar to males. Body annules posterior to ventral curvature, more slender (3 µm) than in males. Slim ambulatory setae in seven apparent rows (setae of external rows equally built as those of internal field), bisinuous with distally bent tip. Five to seven pairs of firm, hollow supporting setae of which one or two pairs situated in front of vulva. No para-anal seta. Typical dorsal thorns (measuring up to 16 µm in length) in region of ventral curvature. Ventral field of hairlike spines located from pharyngeal region to last ambulatory setae. Head capsule with four cephalic and mostly sixteen subcephalic setae, of which eight situated anterior to amphid. Spiral amphid, subdorsally shifted. Buccal cavity with distinct dorsal and smaller ventral tooth. Vulva situated just behind last ambulatory setae. Vagina short and bipartite: Typical vagina vera and muscular vagina uterina. Reproductive system didelphic, amphidelphic with bent ovaries. Posterior ovary bent dorsally; anterior ovary bent ventrally reaching vagina vera with its tip; yolk extending to ventral body curvature giving the impression that anterior ovary is straight. Tail with five annules; non-annulated tailtip heavily cuticularized. Tailtip with crown of seven possibly eight or nine, pores. (ref. ID; 883)
Juveniles: Body-shape, ornamentation of annules, digestive system similar to female; annules slimmer, somatic setae in five longitudinal rows.
- Second juvenile stage. Ambulatory setae in four longitudinal rows: two on each side off body in close apposite pairs, giving the impression of one row of setae on each side. External rows with seven, internal rows with two ambulatory setae. Two pairs of board supporting setae located on fifth and eighteenth annule behind annule carrying last ambulatory setae; first pair measures 16 µm; they have straight tips. Inconspicuous subventral spines located from ninth annule in front of, to fourth annule behind dorsal curvature, no ventral ones. A number of inconspicuous thorns (max. 4 µm long) located subdorsally in region of ventral curvature. Head capsule with four cephalic and four subcephalic setae; spiral amphid, subdorsally shifted; buccal cavity with large dorsal and small ventral tooth. Tail with eight annules; non-annulated tailtip slender (length 2.3 x width) compared to other juveniles stages (length 1.7 x width) and adults. (ref. ID; 883)
- Third juvenile stage. Four subventral rows of ambulatory setae; setae of external rows (eleven setae, 0.8 µm wide at their base) bent once, setae of internal rows (seven setae, 0.4 µm wide at their base) bent twice. Two pairs of broad supporting setae with straight tips, located on ninth and twenty third annule (i.e. fourth annule in front of anus) behind last seta ambulatoria. Ventral to subventral field of inconspicuous spines in region of dorsal curvature. Dorsal to subdorsal field of thorns (max. 6 µm long) extending from thirteenth annule in front of, to twelfth annule behind ventral curvature. Head capsule with four cephalic and eight subcephalic setae; spiral amphid dorsally shifted; buccal cavity with large dorsal and small ventral tooth. Tail with seven annules; non-annulated tailtip broader (length 1.7 x width) than in second juvenile stage. (ref. ID; 883)
- Four juvenile stage. Setae ambulatoriae with large distally bent tips, in four longitudinal rows; external rows with eleven setae (1.7 µm broad at base), bent once; internal rows with seven setae (0.9 µm broad at base), bent twice. Three pairs of broad supporting setae; first two pairs with distally bent tips, located at fourth and eleventh (or seventh) annule behind last seta ambulatoria; third pair with straight tip, located on fourth annule in front of anus, i.e. thirteenth (or eighteenth) annule behind second pair. Ventral to subventral field of spines extending from fifteenth annule in front of dorsal curvature to ambulatory setae. Dorsal to subdorsal field of short thrones (max. 6 µm) extending fourteen annules in front of to eighteen annules behind ventral curvature. Head capsule with four cephalic and ten subcephalic setae; spiral amphid. Tail with seven annules; caudal glands extending dorsally above rectum. (ref. ID; 883)
Etymology
Named after Mombasa (Kenya) where the Kenyan Marine and Fishery Research Institute is situated. (ref. ID; 883)