Antomicron quindecimpapillatus, Holovachov, Oleksandr, 2012

Holovachov, Oleksandr, 2012, Swedish Plectida (Nematoda). Part 2. The genus Antomicron Cobb, 1920, Zootaxa 3380, pp. 39-54 : 40-41

Antomicron quindecimpapillatus sp. n.

( Fig. 1 ; Table 1 )

Type material. Holotype male (slide # 8356), as well as one female and two male paratypes (slide # 8357) each deposited in the type collection of the Department of Invertebrate Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Type locality. Soft mud from 44 m deep, Gullmarn Fjord near Fiskebackskil, Sweden (N 58° 15' 37'', E 11° 27' 43''), 11 August 2011, legit O. Holovachov (one female and three males).

Etymology. The specific epithet refers to the number of supplements (fifteen = quindecim) in male.

Description. Adult. Body tapering anteriorly in pharyngeal region and posteriorly on tail; straight or ventrally curved upon fixation, more strongly curved ventrad in posterior part in males. Maximum body diameter at vulva in female; male body more cylindrical. Cuticle annulated; annuli 2.7–3.2 µm wide at mid-body, without ornamentation. Lateral field present, consists of single alae (two incisures), 2.3–2.8 µm wide at mid-body; originating at level of procorpus and extending posteriorly to middle of tail. Crystalloids absent. Prominent body pores in sublateral position at both sides of lateral field present, arising from oval lateral epidermal gland cells; six-seven pairs of body pores are present along pharyngeal region, and one at level of cardia; numerous body pores scattered over rest of the body. Somatic sensilla absent in female, present in male (see below). Labial region bluntly rounded, continuous with body contour, lips fused. Anteriormost body annule, which demarcates labial region, located at level of posterior third of amphid. Inner and outer labial sensilla indistinct. Cephalic sensilla setiform, equal to 35–40% of labial region diameter. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea elongate doughnut-shaped, 1.6–2.1 times as long as it is wide, with elongate ovoid central elevation. Nerve ring surrounding pharynx at level of anterior part of isthmus. Hemizonid not seen. Secretory-excretory system present; renette cell large, located opposite to ventral side of cardia and anterior part of intestine, extends anteriorly along ventral side of pharynx and forms an excretory ampulla just posterior to nerve ring level. Excretory canal weakly cuticularised, extends from excretory ampulla for a short distance anteriorly and opens to the exterior via a pore just posterior to nerve ring. Buccal cavity uniformly tubular: cheilostom and gymnostom short, undifferentiated; stegostom tubular, with uniformly thickened lumen. Pharynx muscular, cylindrical anteriorly, with distinct oval basal bulb; valvular apparatus absent. Anterior cylindrical part of pharynx subdivided by breaks in muscular pharyngeal tissue into cylindrical procorpus, cylindrical metacorpus and narrow isthmus. Pharyngeal glands and their orifices indistinct. Cardia cylindrical, its posterior part embedded in intestine. Tail almost similar in shape in both sexes (shorter and more curved ventrad in male), elongate-conoid, gradually narrowing proximally. Unstriated tail tip swollen. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Female. Sensilla associated with epidermal glands absent. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 118 µm long (equal to 8.3% of total body length), located on left-hand side of intestine, posterior genital branch 134 µm long (equal to 9.4% of total body length), located on right-hand side of intestine. Oviduct a narrow tube. Two offset, oval, sack-like spermathecae located on each (right and left) side of each (anterior and posterior) gonoduct. Spermathecae filled with oval spermatozoa. Uterus a wide tube composed of large cells. Vagina straight, 0.3 times vulval body diameters long; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae with small drop-shaped sclerotizations. Epiptygmata and sensitive structures around vulva (advulval sensilla) absent. Rectum 1.9 anal body diameters long; surrounded by three gland-like cells at intestine-rectum junction.

Male. Two long setiform sensilla associated with epidermal glands present, emerging through body pores: anterior pair at level of metacorpus and posterior pair at level of basal bulb. Reproductive system diorchic; anterior testis outstretched; posterior one reflexed. Spicules paired, symmetrical, with arcuate subcylindrical shaft and ovoid manubrium. Gubernaculum plate-like, with long dorsal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip and 15 midventral tubular supplements extending for 730–749 µm from cloaca towards anterior end; alveolar supplements absent. Posteriormost tubular supplement 42–49 µm anterior to cloaca, anterior to spicules. Sublateral precloacal and caudal sensilla present: two (one pair) precloacal setae at level of spicules and eight (four pairs) caudal setae arranged in two subventral and two subdorsal pairs. One pair of small papilliform sensilla is located just posterior to the second pair of subventral caudal setae.

Diagnosis. Antomicron quindecimpapillatus sp. n. is particularly characterised by the 1.4–1.5 mm long body; elongate doughnut-shaped amphid; straight vagina with drop-shaped sclerotizations; female without sensilla in pharyngeal region and without supplements; male with two pairs of setiform sensilla in pharyngeal region, 15 tubular and no alveolar supplements, one pair of precloacal and four pairs of caudal setae, 26–29.5 µm long spicules.

Relationships. The new species differs from all other members of the genus Antomicron by its long body (1390–1459 µm vs. less than 1100 µm) and number of tubular supplements in males (15 vs. 2–10). Further differences between all species of the genus Antomicron are summarized in Table 3.

De Coninck, 1965 (all measurements are in µm, except for the ratios a, b, c, c', V, T, EP and NR).

Figures

FIGURE 1. Antomicron quindecimpapillatus sp. n., holotype male (A – C) and paratype female (D – E). A: Anterior end, surface view; B: Pharyngeal region, median section; C: Male posterior region; D: Female tail; E: Female reproductive system (only posterior part is shown). Scale bar: A – E = 20 µm.