Amphimonhystrella boucheri, Zhai & Geng & Sun, 2022

Zhai, Hongxiu, Geng, Chunxiao & Sun, Jun, 2022, Two new species of Xyalidae (Nematoda: Monhysterida) from intertidal zone of the Bohai Sea, China, Zootaxa 5222 (2), pp. 133-144 : 139-142

Amphimonhystrella boucheri sp. nov.

( Figs. 3–4 ; Table 2 )

Type material. Three males and two females were collected from the Estuary of Daliao River. Holotype: male 1 on slide 2021 DLHK1-2 - 16 , paratypes: male 2, male 3, male 4 and female 1 successively on slides 2021 DLHK1-2 - 15 , 2021 DLHK1-2 - 23 , 2021 DLHK1-2 - 22 and 2021 DLHK1-2 - 23 .

Type locality and habitat. Intertidal muddy sediment at the Estuary of Daliao River (40°39′21″ N, 122°9′36″ E) .

Etymology. The species is named in honor of Dr. Guy Boucher, a well-known French nematologist.

Measurements. Table 2 .

Description. Holotype. Body short, cylindrical, tapering slightly towards both ends. Cuticle with fine striations, 1 µm apart. Head tapering anteriorly. Inner labial sensillae not observed; six outer labial setae, 2 µm long, situated immediately anterior to four cephalic setae of same length. Lateral fields and somatic setae absent. Amphidial fovea circular, located at the level of base of buccal cavity. Buccal cavity elongated funnel shaped, 8 µm deep, lightly cuticularised. Pharynx cylindrical, widening posteriorly but not forming true bulb. Cardia elongated, with posterior end surrounded by intestine tissue. Nerve ring situated in the middle of pharynx. Secretory-excretory system not observed. Reproductive system diorchic with two opposed, outstretched testes. Anterior testis situated to the left of intestine and posterior one situated to the right of intestine. Spicules small, strongly curved, 0.7 cloacal body diameter in length, cuticularized with cephalated proximal end and pointed distal end. Gubernaculum tubular with a small dorso-caudal apophysis. Tail conico-cylindrical with two thirds conical anterior portion and a third cylindrical posterior portion. Caudal setae absent. Tail tip swollen with two terminal setae, 5 µm long. Three caudal glands in tandem.

Females. Similar to males in morphological characteristics. Reproductive system monodelphic with outstretched anterior ovary to the left of intestine; postvulvar sac present. Vulva situated just posterior to mid-body, 58% of body length from the anterior end.

Differential diagnosis and discussion. Amphimonhystrella boucheri sp. nov. is characterized by short body (<600 µm vs.>740 µm), deep buccal cavity funnel shaped, circular amphids, conico-cylindrical tail with two thirds conical anterior portion and a third cylindrical posterior portion, males with relatively short L-shaped spicules (12 µm) and tubular gubernaculum with small apophysis.

Currently, Amphimonhystrella includes five valid species, which are A. bullacauda ; A. major ; A. megastoma ; A. parva and A. unita . Amphimonhystrella boucheri sp. nov. is close to A. unita in body size, but differs from the latter species in buccal cavity funnel shaped, not conical in latter species; amphidial fovea circular, 3 µm in diameter (versus oval and 6-7 µm in diameter); spicules 12 µm long with tapered distal end (versus spicules about 22 µm long with rounded distal end). The difference between A. boucheri sp. nov. and its congeners can be inferred from the key below.

Figures

FIGURE 3. Amphimonhystrella boucheri sp. nov. (A) anterior region of male; (B) entire view of male; (C) tail region of male; (D) spicules and gubernaculum; (E) entire view of female. Scale bars: A, D 10 µm, B, C, E 20 µm.

FIGURE 4. Amphimonhystrella boucheri sp. nov. (A) anterior end of male, showing buccal cavity; (B) anterior end of male, showing amphid; (C) tail region of male; (D) cloacal region of male, showing spicules and gubernaculum. Scale bars: A, B, D 10 µm; C 20 µm.