Parasaveljevia limitense, Pastor, Catalina, Russo, Virginia Lo & Villares, Gabriela, 2015

Pastor, Catalina, Russo, Virginia Lo & Villares, Gabriela, 2015, Two new species of Parasaveljevia Wieser, 1953 (Thoracostomopsidae, Nematoda) from Argentinean coasts (Chubut, Argentina), Zootaxa 3999 (4), pp. 498-510 : 503-504

Parasaveljevia limitense n. sp.

( Fig. 4 (A‒L); Fig. 5 (A‒I); Fig. 6 ; Fig. 7 B; Table 1)

Material examined. Holotype Male, CNP-NEM N° 27878. Collected in 1 of April 2006 on ‘El Límite’ beach (45º 59’ S and 67º 35’ W), during mid tide. Characteristics of surface sediment layer: mean particle size (Q2= 0.23; FF % = 0.89; SO index = 0.7; SK index = 1.2). Collector: Catalina Pastor.

Paratypes Three males, four females and one juvenile, same data as holotype mounted on slide numbers CNP- NEM N° 27803‒27805; 27887; 27920; 27940 and 27996.

Description. Holotype: Male. Large body length. Cuticle smooth. Mouth opening surrounded by one dorsal and two ventro-sublateral lips separated by deep incisions. Inner labial setae long (8 Μm long) and inserted at the base of the lip flaps; outer labial and cephalic setae situated at the posterior end of cephalic capsule. Cirri present, 6 Μm long, situated between inner and outer labial setae. Six outer labial setae, 35 Μm long. Cephalic setae with a particular configuration: setae in sublateral and subventral position 32 Μm, those in the lateral position much longer (70Μm). Amphidial fovea indistinct. Junction of end of head capsule with oesophagus not seen. Cephalic setae set in small fenestrae, in posterior margin of cephalic capsule. Cervical setae present in two circles of 6 + 10 setae (respectively, 16 and 12 Μm long). Anterior part of the oral cavity formed of three curved mandibular plates, each corpulent and bowl shaped, rectangular in lateral view and covered by rows of small denticles, ranging in size from smallest to largest from the front to the bottom of the mandible. The two ventro-sublateral mandibles have denticles in five rows with ten per row; the dorsal mandibles in five rows, with eight denticles per row. Rods of lateral mandibles rods rounded at anterior end. The ventro-sublateral mandibles with one tooth shaped oversized knife each, at their base. Dorsal mandible has an arched tooth. Pharynx with normal walls. Cardia present.

Reproductive system diorchic, testes opposed. Two spicules each 40 Μm long, arcuate with velum, proximal end with well-developed cephalisation. Gubernaculum tubular, 6 Μm in width with dorso-caudal apophysis (15 Μm long). One tubular-globular supplement (10 Μm long) situated 75 Μm in front of spicules. A postcloacal papilla present. Tail 170 Μm long (AD = 4.25), conical to cylindrical toward the distal end with swollen tip. The tip of the tail has two setae, 8 Μm long.

Female. Similar to male in general body shape. Lateral mandibles slightly smaller than in males, with only two rows of denticles. Ventro-sublateral and dorsal teeth smaller than in males ( Fig. 4 E). Reproductive system didelphic amphidelphic, ovaries reflexed. Vagina short, not thickened. Tail 166 Μm long (AD = 5.02) with two setae 8 Μm long.

The difference in lengths of the cephalic setae was checked in all the specimens found, to discard the possibility that some setae were broken during sample decantation.

Diagnosis and relationships. If following the key given by Wieser (1953), P. limitense n. sp. would be positioned near P. cirrifera Wieser, 1953 , because it has a similar tail length (AD), has cephalic sensillae inserted in the posterior third of the head capsule and different lengths of the cephalic sensillae. With respect to the characters suggested by Fadeeva et al. (2012) for the related genus Oxyonchus (cephalic capsule and denticles on mandibles), we found differences between them. Parasavaljevia limitense n. sp. has shorter mandibles (12.0 µm vs 19.5 µm width) and bears three rows of five to ten denticles of different sizes, with a small cephalic capsule (10‒12 µm vs 26 µm). It is probably adapted to eat different prey.

Parasaveljevia limitense n. sp. is characterised by having a posterior cirrus positioned between labial and cephalic setae; rectangular-arched mandibles bearing denticles in five lines of ten each, graded in size; small buccal cavity; small cephalic capsule and abundant cervical setae (6+10).

Parasaveljevia limitense n. sp. resembles P. cirrifera in the value of De Man’s b ratio, the total body length, the differential cephalic setae lengths, presence of ventral tooth, presence of cervical setae, but differs in the value of De Man’s a and c ratios, cephalic capsule length, shape of the mandibles with a greater number of denticles of different sizes, smaller size, short cirri length and posterior position behind inner labial setae, and short spicules, gubernaculum and tail.

Etymology. The specific name refers to “El Límite” beach, the area where it was found.

Figures

FIGURE 6. Figure showing main characters that differ between genera Oxyonchus and Parasaveljevia. A. In apical view of Oxyonchus and Parassaveljevia; B. In cephalic capsule (lateral view); C. In cephalic capsule (ventral view).

FIGURE 7. Pictorial key of known Parasaveljevia species (with males). A. P. cirrifera, from Wieser, 1953; B. P. limitense n. sp.; C. P. uncinoa n. sp. Scale bar: 1 = 20 µm.

FIGURE 4. P. limitense n. sp. Line drawings. A. Cirri and cephalic setae on anterior end of male holotype; B. Cirri and cephalic setae on anterior end of female paratype; C. Posterior end of female paratype; D. Ventro sublateral male mandible; E. Ventro sublateral female mandible; F. Precloacal organ; G. tail tip of male holotype; H. Head and buccal cavity of male holotype; I. Head and buccal cavity of female paratype; J. Vulva and gonadal apparatus of female paratype; K. Copulatory apparatus, spicule, gubernaculum of male holotype; L. Posterior end of male holotype. Scale bar: 1 = 20 µm; 2 = 100 µm.

FIGURE 5. P. limitense n. sp. Micrographs of slide mounted specimens. A. Entire male paratype; B. Head and buccal cavity of male holotype, ventro sublateral mandible; C. Entire female paratype; D. Head and buccal cavity of female paratype, setae; E. Head and buccal cavity of male holotype, ventral tooth; F. Head and buccal cavity of female paratype, ventro sublateral tooth; G. Mucus from male paratype spinneret; H. Head and buccal cavity of male holotype, ventro sublateral tooth; I. Copulatory apparatus, spicule, gubernaculum of male holotype. Scale bar: 1 = 20 µm.