Aegialoalaimus bratteni Holovachov

Holovachov, Oleksandr, 2015, Description of Aegialoalaimusbratteni sp. n. from Skagerrak and a review of the genus (Aegialoalaimidae, Nematoda incertae sedis), Biodiversity Data Journal 3, pp. 5738-5738 : 5738

Aegialoalaimus bratteni Holovachov sp. n.

Materials

Type status: Holotype. Location: waterBody: Skagerrak; country: Sweden; verbatimDepth: 352-374 m; verbatimLatitude: N 58° 19' 15.6'' -20.9''; verbatimLongitude: E 10° 29' 33.5'' -34.0''; Identification: identifiedBy: O. Holovachov; Event: year: 2012; month: October; day: 10; habitat: soft bottom; Record Level: datasetID: SMNH Type– 8763; institutionCode: Department of Zoology, Swedish Museum of Natural History; collectionCode: invertebrate type collection

Type status: Paratype. Location: waterBody: Skagerrak; country: Sweden; verbatimDepth: 352-374 m; verbatimLatitude: N 58° 19' 15.6'' -20.9''; verbatimLongitude: E 10° 29' 33.5'' -34.0''; Identification: identifiedBy: O. Holovachov; Event: year: 2012; month: October; day: 10; habitat: soft bottom; Record Level: datasetID: SMNH Type– 8763; institutionCode: Department of Zoology, Swedish Museum of Natural History; collectionCode: invertebrate type collection

Type status: Other material. Location: waterBody: Skagerrak; country: Sweden; verbatimDepth: 232-240 m; verbatimLatitude: N 58° 27' 36.7'' -43.3''; verbatimLongitude: E 10° 32' 52.0'' -59.4''; Identification: identifiedBy: O. Holovachov; Event: year: 2012; month: October; day: 12; habitat: soft bottom; Record Level: datasetID: #147072; institutionCode: Department of Zoology, Swedish Museum of Natural History; collectionCode: general invertebrate collection

Description

Measurements. Male holotype: L=1754 µm, a=38.1, b=9.6, c=15.4, c´ =2.9, T=62.8%. Male paratype: L=1733 µm, a=35.4, b=9.2; c=13.8, c´ =3.1, T=54.9%. Additional male: L=1492 µm, a=?, b=8.6, c=13.0, c´ =2.6, T=53.8%.

Male. (Fig. 1) Body slender, cylindrical over most of its length, tapering anteriorly in the anterior half of pharyngeal region and posteriorly on tail; usually straight or weakly ventrally curved upon fixation; maximum body diameter is 46-49 µm. Cuticle weakly annulated externally, but with distinct transverse striation of inner layers; annules are 1 µm wide, without external ornamentation. Lateral field absent. Crystalloids absent. Body pores and epidermal glands absent. Somatic sensilla present, small papilliform in shape, most distinct along the tail. Labial region rounded, continuous with the body contour, 12.5-13.0 µm wide; lips fused. Inner labial sensilla indistinct. Outer labial sensill pore-like, their nerve endings are distinct. Cephalic sensilla small papilliform, 0.5-1.0 µm long; their bases are located 5-6 µm from the anterior body end. Subcephalic and cervical sensilla absent. Amphidial fovea circular, 10.0-10.5 µm in diameter, with distinct sclerotized margin; its anterior end is located posterior to cephalic sensilla bases, 14-16 µm from the anterior body end. Ocelli absent.

Pharyngeal region is 174-189 m long. Nerve ring surrounds the pharynx at 55.0-58.2% of its length. Hemizonid located at the level with the nerve ring. Secretory-excretory system present; renette cell located on ventral and ventrosublateral sides of the body along the posterior part of pharynx; it extends anteriorly and forms small excretory ampulla just posterior to the nerve ring level. Excretory canal absent, excretory ampulla opens to the exterior on ventral side of the body, at the level with the nerve ring, at 52.9-66.6% of the pharyngeal region length.

Oral opening terminal. Buccal cavity is weakly developed; cheilostom is a narrow tube 3-5 µm long; pharyngostom is indistinguishable from the sclerotized lumen of the pharynx. Pharynx divided into two sections: anterior tubular part and posterior (basal) bulb. Tubular part of the pharynx is 138-151 µm long and 3-4 µm wide; it is surrounded by thin sheath of tissue. Basal bulb is strongly muscularized; 30-33 µm long and 24-28 m wide. Nucleus of the dorsal pharyngeal gland is visible in the middle of the dorsal sector of the basal bulb. Subventral pharyngeal glands indistinct. Pharyngeal gland orifices indistinct. Cardia is 15-18 µm long, its posterior part is embedded in the intestine.

Reproductive system is diorchic, both anterior and posterior testes are outstretched anteriad. Spicules are 20-29 µm long, paired and symmetrical, straight in shape; with conoid shaft and small funnel-shaped manubrium. Gubernaculum absent. Supplements absent. Tail is 114-126 µm long, conoid to subcylindrical in shape, straight or weakly curved ventrad; with bluntly rounded terminus. Caudal glands present, they open to the exterior through common spinneret. Caudal gland nuclei are incaudal.

Female. Not found.

Diagnosis

Aegialoalaimus bratteni sp. n. is particularly characterized by 1.5-1.8 mm long body, short papilliform cephalic sensilla, excretory pore opening just posterior to the nerve ring level, straight spicules, supplements and gubernaculum absent.

Taxon discussion

The new species can be differentiated from:

Aegialoalaimus elegans (as described by de Man 1907, Schuurmans Stekhoven 1931, Boucher and Helléouët 1977, Jensen 1978b, Bresslau and Schuurmans-Stekhoven 1940, Tchesunov 1990) in having longer body (1.5-1.8 mm in A. bratteni sp. n. vs 0.8-1.3 mm in A. elegans ), shape and size of spicules (straight and 22-29 µm long in A. bratteni sp. n. vs arcuate and 34 µm long in A. elegans ), absence of precloacal supplements (vs seven-eight in A. elegans ), absence of gubernaculum (vs present in A. elegans );

A. setosa (as described by Bouwman 1981, Holovachov 2014) in having shorter tail ( c´ =2.6-3.1 in A. bratteni sp. n. vs c´ =4.2 in A. setosa ), shorter cephalic sensilla (0.5-1.0 µm in A. bratteni sp. n. vs 9 µm in A. setosa ), shape and size of spicules (straight and 22-29 µm long in A. bratteni sp. n. vs arcuate and 40-45 µm long in A. setosa ), absence of precloacal supplements (vs eight in A. setosa ), absence of gubernaculum (vs present in A. setosa );

A. leptosoma (as described by Gagarin 2012) in having longer body (1.5-1.8 mm in A. bratteni sp. n. vs 0.5-0.7 mm in A. leptosoma ) and other measurements, shape of spicules (straight in A. bratteni sp. n. vs arcuate in A. leptosoma ), absence of precloacal supplements (vs three-five in A. leptosoma ), absence of gubernaculum (vs present in A. leptosoma ).

Further characters separating all species of the genus are listed in Table 1.