Corresponding author: Oleksandr Holovachov (
Academic editor: Vlada Peneva
The genus
New species,
The genus
Bottom sediment samples were collected in several locations in the southern part of the Skagerrak designated as Bratten area. All samples were collected with the bottom dredge and further sieved in the lab before fixation. Nematodes were extracted from samples using a decanting and sieving method (smallest mesh sizes: 45 µm or 70 µm). Fresh water was used during sieving to induce osmotic shock in nematodes so they will detach from the substrate. Samples were immediately fixed in 4% formaldehyde. Formaldehyde-preserved specimens were transferred to pure glycerine using
Abbreviations used in the text are as follows: L = overall body length; a = body length / greatest body diameter; b = body length / pharyngeal region length; c = body length / tail length; c' = tail length / cloacal body diameter; T = length of main gonad (excluding flexures) / body length (expressed in %).
Type specimens of
Pharyngeal region is 174-189 m long. Nerve ring surrounds the pharynx at 55.0-58.2% of its length. Hemizonid located at the level with the nerve ring. Secretory-excretory system present; renette cell located on ventral and ventrosublateral sides of the body along the posterior part of pharynx; it extends anteriorly and forms small excretory ampulla just posterior to the nerve ring level. Excretory canal absent, excretory ampulla opens to the exterior on ventral side of the body, at the level with the nerve ring, at 52.9-66.6% of the pharyngeal region length.
Oral opening terminal. Buccal cavity is weakly developed; cheilostom is a narrow tube 3-5 µm long; pharyngostom is indistinguishable from the sclerotized lumen of the pharynx. Pharynx divided into two sections: anterior tubular part and posterior (basal) bulb. Tubular part of the pharynx is 138-151 µm long and 3-4 µm wide; it is surrounded by thin sheath of tissue. Basal bulb is strongly muscularized; 30-33 µm long and 24-28 m wide. Nucleus of the dorsal pharyngeal gland is visible in the middle of the dorsal sector of the basal bulb. Subventral pharyngeal glands indistinct. Pharyngeal gland orifices indistinct. Cardia is 15-18 µm long, its posterior part is embedded in the intestine.
Reproductive system is diorchic, both anterior and posterior testes are outstretched anteriad. Spicules are 20-29 µm long, paired and symmetrical, straight in shape; with conoid shaft and small funnel-shaped manubrium. Gubernaculum absent. Supplements absent. Tail is 114-126 µm long, conoid to subcylindrical in shape, straight or weakly curved ventrad; with bluntly rounded terminus. Caudal glands present, they open to the exterior through common spinneret. Caudal gland nuclei are incaudal.
The new species can be differentiated from:
Further characters separating all species of the genus are listed in Table
The only type specimen is preserved but its internal structures are poorly visible.
The original description is based on single female specimen (
The only type specimen is poorly preserved, its anterior end is dried out.
The original description is based on single female specimen (
1 | Cephalic setae long, 9 µm or equal to 1/2 of the corresponding body diameter |
|
– | Cephalic setae short, 1-6 µm long, less than 1/3 of the corresponding body diameter2 |
|
2 | Spicules straight, gubernaculum and supplements absent | |
– | Spicules arcuate, gubernaculum and supplements present |
|
3 | Male with 3-5 precloacal supplements |
|
– | Male with 7-8 precloacal supplements |
|
Cuticle smooth or finely annulated. Lateral alae absent. Epidermal glands absent. Somatic sensilla present. Labial region rounded, continuous with body contour. Inner labial sensilla indistinct. Outer labial sensilla pore-like or papilliform, located on outer surface of lips. Cephalic sensilla papilliform or setiform, located at base of labial region, anterior to amphid. Amphidial aperture circular. Subcephalic and cervical sensilla, deirid and ocelli absent. Secretory-excretory system present; renette cell located opposite to ventral side of pharynx, cardia or anterior part of intestine. Excretory ampulla present. Excretory duct very short, opens to exterior at level with cephalic setae in females and at level of nerve ring in males. Stoma small, undifferentiated. Pharynx divided into anterior long tubular section with strongly sclerotized lumen and weakly developed tissue, and strongly muscularized oval basal bulb. Cardia cylindrical or conoid, partly enveloped by intestinal tissue in its posterior part. Female reproductive system didelphic, amphidelphic, ovary branches reflexed antidromously. Spermatheca present, axial. Vulva equatorial, transverse. Vagina thick;
=
nec
=
Type material of this species could not be located in the collection of C. Allgén. Description and illustrations of this species do not provide sufficient information to be able to assign this species to any nematode genus or family (
Population of
Type material of this species could not be located in the collection of C. Allgén. Description and illustrations of this species do not provide sufficient information to be able to assign this species to any nematode genus or family (
Type material of this species could not be located in the collection of C. Allgén. Description and illustrations of this species do not provide sufficient information to be able to assign this species to any nematode genus or family (
This research was supported by a grant from the Swedish Taxonomy Initiative. Sampling in the Skagerrak was conducted using the vessel “Skagerak” and facilities of the Sven Lovén Centre for Marine Sciences in Kristineberg. "Inventering Bratten" was an interdisciplinary inventory project also financially supported by the Swedish Taxonomy Initiative.
Photomicrographs of the anterior ends of type specimens of two
Diagnostic characters of valid species of the genus
Character | |||||
---|---|---|---|---|---|
Body length (mm) | 0.8-1.3 | 0.5-0.7 | 1.4-1.8 | 0.4-0.6 | 1.5-1.8 |
Tail length (µm) | 81-102 | 54-68 | ≈130 | 45-75 | 114-126 |
c' | 3.0-5.0 | 3.1-4.0 | 5.0-6.0 | 4.2 | 2.6-3.1 |
Cephalic setae length (µm) | 1.0-6.0 | 1.5-2.0 | ≈9 | 2.0 | 0.5-1.0 |
Spicules length (µm) | 34 | 23-24 | 40-45 | 15 | 22-29 |
Supplements | 7-8 | 3-5 | 8 | ? | absent |
Excretory pore in male | nerve ring level | ? | nerve ring level | nerve ring level | nerve ring level |
Excretory pore in female | cephalic setae bases | ? | ? | ? | NA |
Spicule shape | arcuate | arcuate | arcuate with notch | arcuate with notch | straight |
Gubernaculum | present | present | present | present | absent |