Ceramonematidae Cobb, 1933

Leduc, Daniel, 2024, Four new free-living marine nematode species (Plectida: Ceramonematidae) and two new species records (Desmodorida: Desmodorinae) from Rangitāhua / Kermadec Islands, Aotearoa / New Zealand, European Journal of Taxonomy 970, pp. 138-174 : 141-142

Family Ceramonematidae Cobb, 1933

Dasynemellidae De Coninck, 1965: 627–628 .

Diagnosis (emended from Holovachov (2014))

Cuticle coarsely annulated along entire body, except for smooth cephalic capsule and terminal cone of tail; cuticle of some species may appear pink or purple upon regular fixation (without using dye). Each annule divided into plates by eight longitudinal crests/ ridges extending from cephalic capsule to posterior body part, dividing entire body into eight sectors. Epicristae of each annule overlap parts of adjacent annules. Zygapophyses probably present in all species, but often visible only under SEM. Annules unequal in width, often wider dorsally than ventrally; annule width increases gradually from first postcephalic annule to annule located somewhat posterior to pharyngo-intestinal junction; annules increase in width posterior towards midbody region; posterior to ⅔ of body length, annule width gradually decreases again, with narrowest annule located near anal / cloacal opening or on tail; narrowest adanal or caudal annule followed posteriorly by one much wider annule and then by caudal annules in which width gradually decreases toward terminal cone; last annule before terminal cone most narrow. Intracuticular vacuoles absent or present; in some species body annules may display external ornamentations on surface. Lateral alae absent. Body pores present at least on cephalic capsule and on terminal cone. Epidermal glands absent. Somatic sensilla absent, except for caudal setae in males. Labial region in shape of cephalic capsule; lip pairs fused into three lobes or all lips fused completely. Cephalic capsule cylindrical, with rounded or blunt apical part, often with protruding perioral cylinder and peripheral cuticular ridges. Inner labial sensilla indistinct. Outer labial sensilla setiform or papilliform. Cephalic sensilla setiform; their bases located on outer surface of the lips, anterior to amphid. Subcephalic and cervical sensilla, ocelli and deirids absent. Amphids located at middle of cephalic capsule; amphidial aperture usually shorter and narrower than immediately underlying amphidial fovea, often dissimilar in shape and size between sexes. Shape of amphidial aperture varies from unispiral to loop-shaped and hook-shaped with asymmetrical branches. Secretory-excretory system present; renette cell elongate, located opposite to ventral side of cardia and anterior part of intestine. Excretory ampulla present, located at level of isthmus. Cuticularized excretory duct very short, opens to exterior somewhat posterior to nerve ring level. Oral opening triangular or rounded. Buccal cavity funnel-shaped: cheilostom usually as cylindrical or funnel-shaped anterior-most part, not cuticularised; gymnostom short and not cuticularised; stegostom closed, linear, its muscular lining continuous with that of corpus. Pharyngeal tubes absent. Pharynx subdivided by breaks in muscular tissue into anterior corpus and posterior postcorpus; corpus uniformly cylindrical, muscular, with evenly distributed myofilaments; postcorpus glandular and consisting of anterior narrower isthmus and pear-shaped basal swelling; dorsal sector of basal bulb often enlarged to accommodate dorsal pharyngeal gland; pharyngeal lumen uniform in thickness along entire pharynx length; valves absent. Dorsal and two subventral gland orifices penetrate pharyngeal lumen at base of stoma. Dorsal gland nucleus is visible in anterior part of basal swelling. Cardia conoid, glandular, surrounded by intestinal tissue. Female reproductive system didelphic-amphidelphic with equally developed branches, ovaries reflexed antidromously. Spermatheca usually absent. Vulva equatorial, transverse. Vagina straight or sigmoid; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae and epiptygmata absent. Male reproductive system diorchic, anterior testis outstretched, posterior one reflexed. Spicules symmetrical, arcuate; gubernaculum present. Copulatory apparatus composed of single midventral precloacal sensillum, located on precloacal cuticular plate. Setae in caudal region of males arranged in subventral and subdorsal rows along tail. Three caudal glands present, their nuclei incaudal. Spinneret functional.

Remarks

The family was reviewed by Tchesunov & Miljutina (2002), who provided identification keys to all ceramonematid genera and species. The only subsequent species descriptions for the family were provided by Holovachov et al. (2008a, 2008b). We emended the diagnosis to account for the presence of spermatheca in Metadasynemoides taihua sp. nov.