Antomicron pellucidum Cobb, 1920

Holovachov, Oleksandr, 2012, Swedish Plectida (Nematoda). Part 2. The genus Antomicron Cobb, 1920, Zootaxa 3380, pp. 39-54 : 46-48

Antomicron pellucidum Cobb, 1920

( Fig. 3 ; Table 1 )

Material examined. One male (slide USNM 1110790) from the collection of the Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, USA. Female specimen was also available from the same locality but was not preserved well enough to prove useful.

Habitat and locality. Bottom sediment 300 yards off shore at Turkey Point, Florida, Gulf of Mexico (one male).

Description. Male. Body tapering anteriorly in pharyngeal region and posteriorly on tail; ventrally curved upon fixation, more strongly curved ventrad in posterior part. Cuticle annulated; annuli 2.7 µm wide at mid-body, without ornamentation. Lateral field present, consists of single alae (two incisures), 2.3 µm wide at mid-body; originating five annules posterior to amphid base, midway between first and second body pores and extending posteriorly, its posterior end cannot be seen on tail. Crystalloids absent. Prominent body pores in sublateral position at both sides of lateral field present, arising from oval lateral epidermal gland cells; 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. Sensilla associated with epidermal glands present, emerging through third pair of body pores. Labial region bluntly rounded, continuous with body contour, lips fused. Anteriormost body annule, which demarcates labial region, located at level of anterior third of amphid. Inner sensilla indistinct. Outer labial sensilla small papilliform, located on anterior surface of lips. Cephalic sensilla setiform, equal to 45% of labial region diameter. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea doughnut-shaped, 1.4 times as long as it is wide, with oval central elevation. Nerve ring surrounding pharynx at level of anterior part of isthmus. Hemizonid not seen. Secretoryexcretory system and excretory pore not found. Buccal cavity uniformly tubular: cheilostom short funnel-shaped, undifferentiated; gymnostom short, with small bacilliform gymnorhabdia; 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 somewhat expanded procorpus, cylindrical metacorpus and cylindrical isthmus. Pharyngeal glands and their orifices indistinct. Cardia short conoid, embedded in intestine. Reproductive system diorchic; anterior testis outstretched; posterior one reflexed. Spicules paired, symmetrical, with arcuate subcylindrical shaft and oval manubrium. Gubernaculum plate-like, with long dorsal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip and six midventral tubular supplements extending for 291 µm from cloaca towards anterior end; alveolar supplements absent. Posteriormost tubular supplement 81 µm anterior to cloaca, anterior to spicules. Sublateral precloacal and caudal sensilla present: two (one pair) precloacal setae at level of spicules and several caudal setae, of which only two can be clearly seen. Tail elongate-conoid, gradually narrowing proximally. Unstriated tail tip swollen. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Diagnosis (supplemented with literature data). Antomicron pellucidum is particularly characterised by the 1.0– 1.1 mm long body; doughnut-shaped amphid; female without supplements; male with one pair of sensilla in pharyngeal region, 6–8-eight tubular and no alveolar supplements, one pair of precloacal and several pairs of caudal setae, 34 µm long spicules.

Remarks. Current specimen agrees well with the type specimen in general morphology, measurements and shape of amphids, the only difference being the number of tubular supplements (6 vs. 8 in the original description). Unfortunately, the original description of this species is insufficiently illustrated to allow any further comparison.

Figures

FIGURE 3. Antomicron pellucidum Cobb, 1920, male. A: Pharyngeal region, median section; B: Anterior end, surface view; C: Posterior region. Scale bar: A – C = 20 µm.