Morphological and molecular characteristics of Geocenamus longus and the first report of G. brevidens from a karst cave (Nematoda: Merliniidae Siddiqi, 1971) Author Rybarczyk-Mydłowska, Katarzyna 0000-0001-6180-0392 katarzynar @ miiz. waw. pl; https: // orcid. org / 0000 - 0001 - 6180 - 0392 katarzynar@miiz.waw.pl Author Sikora, Grzegorz 0000-0002-4693-3848 gsikora @ miiz. waw. pl; https: // orcid. org / 0000 - 0002 - 4693 - 3848 gsikora@miiz.waw.pl Author Kubicz, Magdalena 0000-0002-9098-3797 mkubicz @ miiz. waw. pl; https: // orcid. org / 0000 - 0002 - 9098 - 3797 mkubicz@miiz.waw.pl text Zootaxa 2022 2022-05-11 5134 3 383 398 journal article 55573 10.11646/zootaxa.5134.3.3 0b65e67e-8475-4faf-9a56-b8011648963b 1175-5326 6538167 1BB4C248-772C-4A84-9161-2740E884F060 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. 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. 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 .