Cribronema sturhani, Boström & Holovachov, 2019

Boström, Sven & Holovachov, Oleksandr, 2019, Description of Cribronema sturhani sp. n. (Nematoda, Rhabditida, Cephalobidae) a second species of a rare genus from Cameroon, Zootaxa 4695 (2), pp. 175-181 : 176-181

Cribronema sturhani sp. n.

( Figs 1–3 , Table 1 )

Material examined. Holotype female, three paratype females and eleven paratype males on slides # SMNH-Type- 9200 - SMNH-Type-9204 deposited in the invertebrate collection of the Department of Zoology , Swedish Museum of Natural History, Stockholm, Sweden.

Locality and habitat: Cameroon, settlement Mbode, 35 km south of Kribi, virgin rainforest, three soil samples (Z546, Z547 and Z551), 26 March 1994, legit D. Sturhan.

Description. Adult. Body more or less arcuate ventrad when killed by heat. Cuticle finely annulated, annuli 1.2-1.4 µm wide at midbody. Lateral field with 3 incisures, occupying about 13-19 % of body diameter, extending posteriorly to phasmid in females and to tail terminus in males. Lip region slightly offset, carrying 6 +4 papillae and two small amphids. Six symmetrical leaf-like lips, each lip with a median rounded flap flanked by two shorter triangular-conoid flaps. Labial probolae absent. Stoma about 0.6-0.8 times lip region diameter long. Stomatal parts less well discernible. Cheilorhabdia small, rounded, in latero-median view. Pharynx cephaloboid. Pharyngeal corpus cylindrical; isthmus narrow, demarcated from corpus by a break in the musculature; bulb oval, with valves. Nerve ring at level of metacorpus. Excretory pore and hemizonid at level of metacorpus or metacorpus-isthmus junction. Deirids at level of isthmus.

Female. Reproductive system monodelphic, prodelphic, in a dextral position in relation to intestine. Ovary reflexed posteriorly at oviduct, ovary less well observed but straight posterior to vulva in one specimen. Spermatheca with globular sperm. Vulval lips variable, from sunken to slightly protruding; vagina equal to about one-fourth to one-third of vulval body diameter in length. Postvulval uterine sac equal to 1.7-1.9 vulval body diameters in length. Tail conoid with 14-16 ventral annuli; terminus with a pointed mucro about 3.5 µm long. Phasmids located at about one-fifth to two-fifths of tail length.

Male. Similar to female in most respects, except for the sexual characters. Reproductive system monorchic, dextral in position; testis reflexed ventrad anteriorly, except for one specimen with a pretzel-shaped reflexed part. Spicules paired and symmetrical, curved ventrad; with oval manubrium and subcylindrical, gradually narrowing shaft. Gubernaculum plate-like, curved ventrad in dorsal part. Genital papillae distributed as follows: one or two ventrosublateral - precloacal pairs (at 12-21 µm [8 specimens] and at 20-39 µm [2 specimens] anterior to cloacal aperture), one ventrosublateral adcloacal pair, two pairs (one ventrosublateral and one lateral) at mid-tail, and three pairs (one subventral, one lateral and one dorsosublateral) closer to tail terminus, and a single midventral on anterior cloacal lip. Tail conoid; terminus with a pointed mucro about 2-3 µm long. Phasmids located at about one-third to two-fifths of tail length.

Diagnosis. Cribronema sturhani sp. n. is characterised by a 259-287 µm long body in females and 256-291 µm in males; cuticle finely annulated; lateral field with three incisures (two wings), extending to phasmid in females and to tail tip in males; six symmetrical leaf-like lips, each lip with a median rounded flap flanked by two shorter triangular-conoid flaps; labial probolae absent; pharyngeal corpus 2.4-3.2 times isthmus length; nerve ring at level of metacorpus; excretory pore and hemizonid at metacorpus-isthmus junction; deirids at level of isthmus; spermatheca 14-26 µm long; postvulval uterine sac 1.7-1.9 times vulval body diameter long; spicules 13-15 µm long; gubernaculum 8-9 µm long.

Etymology. The species in named in honour of our friend and colleague Dr. Dieter Sturhan who provided the samples for this study and sadly passed away in 2017 ( Liškov & Vasilkov 2018).

Remarks. The new species Cribronema sturhani sp. n. agrees in many respects with C. cribrum , which is the only species in the genus and was also described from Cameroon. The new species differs from C. cribrum by the following features: a somewhat shorter tail in the females (20–22 m vs. 22–25 µm), longer, developed spermatheca and postvulval uterine sac, tail terminus in females pointed vs. harpoon-shaped, and presence vs. absence of males.

Figures

FIGURE 1. Cribronema sturhani sp. n. A–B. Female reproductive system. C–D. Pharyngeal region. E. Female tail. F. Male tail. Scale bar = 20 µm.

FIGURE 2. Cribronema sturhani sp. n. photomicrographs. A-C. Anterior end, lateral view at different focus levels. D. Lateral field and deirid (arrowhead). E. Pharyngeal region, median section. F-H. Female reproductive system. I. Lateral field at midbody level. Scale bars = 5 µm.

FIGURE 3. Cribronema sturhani sp. n. photomicrographs. A–B. Female tail. C–D. Male tail showing tail terminus. E. Male tail showing lateral field and phasmid (arrowhead). F. Spicules. G. Gubernaculum. H–I. Male posterior region showing genital papillae (arrowheads). Scale bars = 5 µm.

Tables

TABLE 1. Morphometrics (in µm) of Cribronema sturhani sp. n. from Cameroon compared with the type population of C. cribrum Siddiqi, 1993 from Cameroon (presented as mean±s.d. and (range) or only range).

Population	Cribronema sturhani sp. n.			Cribronema
				cribrum
	Holotype ♀	4 ♀♀	11 ♂♂	13 ♀♀
		(incl. holotype)
Body length	273	27 5 ± 11	278 ± 13	280 ± 10
Body diameter	15.0	(259–287) 14.6 ± 1.1	(256–291) 13.1 ± 0.8	(260–300) 15.8
Pharynx length	89	(13–16) 88.0 ± 1.0	(12.0–14.5) 87.6 ± 2.2	(14–18) 90 ± 4.2
		(87–89)	(84–91)	(84–101)
Tail length	21.5	21.3 ± 0.4	24.3 ± 1.0	22.8 ± 0.8
Anal or cloacal body diameter	9.5	(20.5–21.5) 8.9 ± 0.6	(23.0–26.5) 10.9 ± 0.5	(22–25) -
		(8.0–9.5)	(10.0–11.5)