Geocenamus longus (Wu, 1969) Tarjan, 1973

Rybarczyk-Mydłowska, Katarzyna, Sikora, Grzegorz & Kubicz, Magdalena, 2022, Morphological and molecular characteristics of Geocenamus longus and the first report of G. brevidens from a karst cave (Nematoda: Merliniidae Siddiqi, 1971), Zootaxa 5134 (3), pp. 383-398 : 386-388

Characteristics of Geocenamus longus

Systematics

Geocenamus longus ( Wu, 1969) Tarjan, 1973

= Tylenchorhynchus longus Wu, 1969

= Merlinius longus ( Wu, 1969) Sturhan, 1981

= Scutylenchus longus ( Wu, 1969) Skwiercz, 1984

= Pathotylenchus longus ( Wu, 1969) Eroshenko & Volkova, 1987

= Geocenamus longus ( Wu, 1969) Brzeski, 1991

= Scutylenchus longus ( Wu, 1969) Sturhan, 2011

= Geocenamus longus ( Wu, 1969) Sturhan, 2012

Description. Figures 1 and 2 . Measurements see Tables 1–3 .

Female. Body straight to slightly bent ventrally when relaxed. Cuticle consists of two layers, tessellated with longitudinal striae at mid-body.Annuli 2.5–3.5 µm wide, flattened, striae shallow, irregular longitudinal striae divide the annuli into small blocks. Lateral field of adults with six lines, weakly crenated. Lateral field of juveniles with four lines only. Inner incisures sometimes not seen but lateral field crossed by short irregular transverse and oblique striae. Head offset by constriction, with 6–8 (mostly 7) annuli. Labial disc conspicuous. Cephalic framework weakly developed, not refractive. Labial annules divided into six segments by longitudinal striae. Stylet long and slender, cone longer than shaft, basal knobs relatively small, well developed. Deirids absent. Nerve ring slightly behind median bulb. Hemizonid near to excretory pore. Glandular pharyngeal basal bulb elongated, cylindrical. Vulva transverse with double epiptygma sunken into a distinct cavity, vagina swollen near vulva. Ovaries outstretched, paired. Spermatheca, round, well developed, filled with sperm cells. Phasmid situated at mid-tail. Tail tapering evenly to an irregularly striated terminus, bearing 23–35 annuli.

Male. Male slightly smaller than female. Bursa crenate, reaching to tail terminus. Spicule slightly bent.

Gubernaculum thickened.

Molecular characterization. 18S, 28S rDNA and mtCOI sequences were successfully sequenced from five independent G. longus individuals (four females and one juvenile). No intraspecific variation was observed within those sequences. Representative sequence fragments were deposited in GenBank under the following accession numbers: OM 618608 (18S rDNA), OM 618606 (28S rDNA) and OM 615893 (mtCOI). This study delivers the first molecular characterization of G. longus .

Figures

FIGURE 1. Light microscopy images of Geocenamus longus, female. A) Entire body; B) Pharyngeal region; C) Pharyngeal region with a visible hemizonid near to the excretory pore; D) Anterior end of the body, the structure of the cuticle; E) Anterior end of the body with a visible long stylet; F) Vulval region with a visible filled spermatheca; G–I&M) Vulval region; J–K) Tail region with a visible anus; L) Tail region with a visible phasmid. Scale: A) 50 µm; B–M) 10 µm.

FIGURE 2. Light microscopy images of Geocenamus longus, male. A) Entire body; B) Anterior end of the body with visible long stylet; C) Pharyngeal region; D) Lateral field; E) Posterior region with visible testis; F–G) Tail region with visible spicules; H–I) Tail region with a visible bursa. Scale: A) 50 µm; B–I) 10 µm.