Calcaridorylaimus castaneae, Nedelchev, Sevdan, Elshishka, Milka, Lazarova, Stela, Radoslavov, Georgi, Hristov, Peter & Peneva, Vlada, 2014

Nedelchev, Sevdan, Elshishka, Milka, Lazarova, Stela, Radoslavov, Georgi, Hristov, Peter & Peneva, Vlada, 2014, Calcaridorylaimus castaneae sp. n. (Nematoda, Dorylaimidae) from Bulgaria with an identification key to the species of the genus, ZooKeys 410, pp. 41-61 : 44-46

Calcaridorylaimus castaneae sp. n. Figs 2-6

Measurements.

See Table 1.

Description.

Female. Body slender, more or less curved ventrally. Cuticle ca 2 μm at anterior part of neck, 3 μm thick at midbody, 4.5-5.5 μm at postanal region; outer layer with fine transverse striae. Lateral chord ca 1/4 of body width. Three dorsal, two ventral and three lateral pores are observed in the spear area. Lip region practically not offset, lip region width ca 20% of its height. Lips partly fused, labial papilae slightly protruding. Body at proximal end of pharynx 3-4 times the width of the lip region diameter. Amphidial aperture 5-6 μm wide or about half the lip region width. Odontostyle 1.2-1.3 times the lip region diameter, aperture occupying 35-40% of its length. Odontophore simple 1.3-1.7 times odontostyle length. Guiding ring at 8.5-9 μm from anterior end. Nerve ring surrounding the pharynx at 36-39% of neck length from head end. Hemizonid and conspicuous excretory pore observed in the nerve ring region. Pharyngeal characters (five females and five males): pharynx beginning to widen at 56-60% and attaining its full width at 61-64% of neck length from anterior end. DO (for terminology see Loof and Coomans 1970) lying near the point where the pharynx attains its full width; DO–DN 8-13 μm. The two S1N lying at a small distance behind the middle of the distance DN–S 2N, the anterior one (S1N1) smaller, ca 2 μm diam; S1N2 comparatively large and distinct, 3-4 μm diam. DN nucleolus 4-4.5 μm diam.; S2N 2-3 μm diam. (DN>S1N2>S2N). Locations (%):

Cardia conoid, variable in length, microvilli visible only here. Genital system didelphic-amphidelphic, ovaries reflexed, reaching rarely the vulva level. Oviducts and ovaries very long compared to uteri. Uteri not differentiated, short, anterior 96-125 μm and posterior 95-135 μm long, in one female with no sperm inside the genital system uteri shorter, 83 μm each, sphincter between uterus and pars dilatata oviductus well developed. Sperm present in uteri and pars dilatata oviductus. Synchronous uterine eggs 1-3, measuring 72-78 × 32-44 μm. Vulva transverse. Vagina extending to 60-70% inwards: pars proximalis 9-13 μm wide, 14.5-19.5 μm long, pars refringens more or less rounded trapezoid, 10-12.5 μm wide, 4-6 μm deep; pars distalis approx. 1.5 μm (terminology following De Ley et al. 1993). Peculiar tongue-like valve present at intestine-prerectum junction. Rectum 1.3-1.5, prerectum 3-4 times anal body width long, respectively. Tail first conoid, then more or less uniformly tapering to a narrowly rounded terminus. Posterior part of tail usually slightly curved dorsally. Two pairs of caudal pores, one subventral, other subdorsal.

Male. General morphology similar to that of female, body curved ventrally in J-shape when fixed. Genital system diorchic, testes opposed, well developed. Spicules dorylaimoid, with double contour on dorsal arm, 1.3-1.6 times the corresponding body diameter long; ventral arm smaller than dorsal. A spur present dorsally before the distal tip, distinctly visible in extruded spicules. Lateral guiding pieces 9-11 μm long or ca. 23 % spicule length. In addition to adcloacal pair seven to twelve (mostly nine or ten), regularly spaced ventromedian supplements present (9 supplements in 8 specimens; 10 suppl. - in 7, and 7, 8 and 12 each in one specimen). Prerectum 4.5-7.5 times the corresponding body diameter long, extending 0.7-1.8 body widths anterior to the supplement series. Tail dorsally conoid and broadly rounded. One subdorsal and one subterminal pair of caudal pores.

Differential diagnosis and relationships.

Calcaridorylaimus castaneae sp. n. differs from all species in the genus by a combination of the following characters: long body (1.4-2.1 mm), lip region practically not offset, short odontostyle (14.5-16 μm in females and 14-16 μm in males) and short female tail (75.5-110.5 μm, c=14.7-23.6; c’=2.9– 4.4); vulva transverse, 38-46 μm long spicules with spur before its distal end. The new species is most similar to Calcaridorylaimus andrassyi from which it can be differentiated by having transverse vulva vs pore-like and shorter spicules (38-46 μm vs 52-57 μm). Further, Calcaridorylaimus castaneae differs from Calcaridorylaimus ruwenzorii by having shorter odontostyle (14.5-16 μm vs 19.5-25 μm), and tail (75.5-110.5 μm vs 160 μm, higher c (c=14.7-23.6 vs c=10) and lower c’ ( c’=2.9– 4.4 vs 7) values in females. It can be differentiated from Calcaridorylaimus arcticus , Calcaridorylaimus beatus , Calcaridorylaimus calcarifer and Calcaridorylaimus signatus by having different vulva shape (transverse vs longitudinal) and shorter spicules (38-46 μm vs 57-67 μm; 48-55 μm; 52-54 μm and 72 μm). From Calcaridorylaimus sirgeli it differs by having transverse vulva vs pore-like, higher c (c=14.7-23.6 vs c=9.7-11.3) and lower c’ ( c’=2.9– 4.4 vs c’=5.3– 6.7) values. Finally, Calcaridorylaimus castaneae differs from Calcaridorylaimus promissus and Calcaridorylaimus simillimus by having longer odontostyle (14.5-16 μm vs 13 μm and 11 μm) and shorter tail (75.5-110.5 μm vs 158-178 μm and 175 μm).

Presence of the conspicuous excretory pore observed in Calcaridorylaimus castaneae is unusual for members of Dorylaimida, however, similar structure has been mentioned only for two Longidorus species, namely Longidorus macrosoma Hooper, 1961 and Longidorus carniolensis Širca et al., 2011 ( Aboul-Eid 1969, Širca et al. 2011) and for several Mesodorylaimus species origination from Antarctica - Mesodorylaimus chipevi Nedelchev & Peneva, 2000, Mesodorylaimus antarcticus Nedelchev & Peneva, 2000, Mesodorylaimus masleni Nedelchev & Peneva, 2000, Mesodorylaimus imperator Loof, 1975 ( Nedelchev and Peneva 2000).

Type locality and plant association.

Belasitsa Mountain, south-western Bulgaria, litter from old broadleaf forest (100-140 years) dominated by Castanea sativa , mixed with Quercus daleshampii and Fagus sylvatica . Site is located in the vicinity of Belasitsa hut, 41°22'12"N, 23°11'12"E (sub-compartment 140b). Second locality: young sweet chestnut forest (30-40 years old) near Belasitsa village (sub-compartment 104g).

Type material.

Holotype and 80 paratype females and 47 males deposited in the nematode collection of the Institute of Biodiversity and Ecosystem Research, Sofia, Bulgaria. Other paratypes deposited as follows: four females and two males in the Nematode Collection of the Foodland Environment Research Agency, Sand Hutton, UK (former Rothamsted Nematode Collection); three females and three males in the USDA Nematode Collection, Beltsville, Maryland, USA; two females and two males in the Riverside Nematode Collection, University of California, Riverside, USA; four females, and four males in the Wageningen Nematode Collection (WANECO), Wageningen, the Netherlands; four females and three males in the Nematode Collection of the Zoology Museum of the Ghent University, Belgium.

Etymology.

The scientific name is derived from the generic name of dominant tree species, the sweet chestnut tree ( Castanea ) in the forest where this nematode was found.