Metalinhomoeus de Man, 1907

Ansari, Kapuli Gani Mohamed Thameemul, Lyla, Somasundharanair & Khan, Seyd Ajmal, 2018, New distributional records of free-living marine Nematodes from Indian waters IV. Linhomids and Axanolaimids, Records of the Zoological Survey of India 118 (4) : -

Genus Metalinhomoeus de Man, 1907

2. Species Metalinhomoeus filiformis de Man, 1907

Synonym: Terschellingia filiformis de Man, 1907

: Metalinhomoeus cylindricauda Stekhoven, 1950 : Metalinhomoeus similis Allgen, 1935

Material examined: 20 males and 12 females collected from Karaikal 30-50m, 51-75m depths (20.12.2008) ; Parangipettai 30-50m, 51-75m, 76-100m 101-150m depths (19.12.2008) ; Cuddalore – SIPCOT 30-50m depth (19.12.2008) ; Chennai 30-50m, 51-75m, 101-150m, 151- 175m depths (17.12.2008) and Tammenapatanam 30- 50m, 101-150m, 151-175m depths (16.12.2008) .

Female: Not found

Feeding type: The specimen showed buccal cavity armed with small. According to the classification of buccal cavity by Wieser (1953), this species is an epigrowth feeder (2A).

Habitat: Silty sediments.

Distribution: India: Tammenapatanam. Elsewhere: England ( Warwick et al., 1998); English Channel ( Hansson, 1998); North Sea ( Gerlach and Riemann, 1974; Vincx, 1989; Hansson, 1998); Kieler Buchat, Skagerrak, Oresund and Mediterranean ( Hansson, 1998).

Remarks: The specimens examined conformed well to the earlier description of Warwick et al., (1998) except for the smaller body size. The total body length described was 3-3.4mm and tail length 3.5-4.5a.b.d. The body length of the specimen studied at present was found smaller being 2.1mm and the tail length 3.6 a.b.d. This is the first record of the species from the Indian waters.

de Man ratio: a b c Male: 93.06±1.92 10.06±0.87 8.35±1.02

(91.98-94.89) (9.12-10.86) (7.54-9.16) Female: 87.14±1.40 9.64±0.67 9.12±0.41

(85.92-88.98) (9.02-10.12) (8.78-9.76)

Description: Body length 1.5-2.2mm in male and 1.7-2.5mm in female. Maximum diameter 15-17 µm in male and 21- 28µm in female. Cuticle faintly striated. Six minute cephalic papillae. Four 12µm cephalic setae and subcephalic setae 4µm: two situates medially between cephalic and amphids. Circular amphids (7-12µm in diameter). Buccal cavity with a cuticularised base. Oesophagus relatively short, with a small posterior bulb. Tail gradually tapering (8.4-8.9a.b.d. in male and 8.2-8.6a.b.d. in female). Spicules 19-23µm slightly curved. Gubernaculum with a pair of 6-9µm dorsal apophysis. Two outstretched ovaries. Vulva present at 49- 52% of body length ( Figure 2 ).

Feeding type: The specimens showed large buccal cavity that is not armed with teeth.According to the classification of buccal cavity by Wieser (1953), this species is a nonselective deposit feeder (1B).

Habitat: Sandy sediments.

Distribution: India: Karaikal, Parangipettai, Cuddalore – SIPCOT, Chennai and Tammenapatanam. Elsewhere: Helgoland and Netherland ( Hansson, 1998); England ( Warwick et al., 1998); European waters and English Channel ( Hansson, 1998; De Smet et al., 2001); Kieler Buchat, Skagerrak, Oresund and Kattegatt ( Hansson, 1998). two per lateral, three per submedian group. Four subcephalic setae situated at level with the anterior of amphids. Somatic setae virtually absent apart from tail. Circular amphids (13-14µm) wide. Buccal cavity cup-shaped, somewhat cuticularised but apparently without any tooth-like structures. Oesophagus gradually widens towards posterior but no bulb. Tail conical with short cylindrical tip (6.7-6.9a.b.d. in male and 6.2-7.9a.b.d. in female). Spicules 69-73µm curved. Gubernaculum with apophysis. Two outstretched ovaries. Vulva present at 48- 51% of body length ( Figure 3 ).

Remarks: The specimens examined conformed well to the earlier description of Warwick et al. (1998) except for the smaller body size. The total body length described was 2.9-3.3mm and tail length 5.9a.b.d. The body length of the specimen studied at present was found smaller being 1.5-2.2mm and the tail length 8.4-8.9a.b.d. in male and in female 1.7-2.5mm body length and tail length

8.2-8.6a.b.d. This is the first record of the species from the Indian waters.

Figures

Figure 2. Metalinhomoeus filiformis de Man, 1907 a) entire female b) female head, c) female tail, d) male head, e) female tail, f) male tail.

Figure 3. Paralinhomoeus conicaudatus (Allgen, 1930) a) entire male b) male head, c) male tail, d) female head, e) female tail, f) entire female.