Desmodoridae Filipjev, 1922

Cavalcanti, Mariana Da Fonseca, Silva, Maria Cristina Da & Fonsêca-Genevois, Verônica Da, 2009, Spirodesma magdae nov. gen. nov. sp. (Nematoda: Desmodoridae) from the Brazilian deep sea (Campos Basin, Rio de Janeiro, Brazil) *, Zootaxa 2096, pp. 109-118 : 111-116

Desmodoridae Filipjev, 1922

Spiriniinae Gerlach & Murphy, 1965

Diagnosis of the subfamily Spiriniinae (after Decraemer & Smol 2006). Desmodoridae . Body cuticle finely striated. Head not demarcated as a cephalic capsule. Amphideal fovea a simple spiral, usually located far anterior on the body. Buccal cavity rather small, from minute to medium-sized, with a distinct or a minute dorsal tooth; two smaller ventrosublateral teeth may be present or absent.

List of valid genera within Spiriniinae ( Lorenzen 1994; Verschelde, Muthumbi & Vincx 1995; Vincx & Gourbault 1989):

Alaimonema Cobb, 1920

Chromaspirina Filipjev, 1918

Metachromadora Filipjev, 1918

Onyx Cobb, 1891

Papillonema Verschelde, Muthumbi & Vincx, 1995

Parallelocoilas Boucher, 1975

Perspiria Wieser & Hopper,1967

Polysigma Cobb, 1920

Pseudometachromadora Timm, 1952

Sigmophoranema Hope & Murphy, 1972

Spirinia Gerlach, 1963 (type genus)

Diagnosis of Spirodesma nov. gen. Body tapering at extremities. Body cuticle with strong transverse annulations. Amphids unispired, with circular amphideal fovea. Buccal cavity with 3 equally sized teeth. Pharynx with well-developed spherical and terminal esophageal bulb. One anterior testis lying left of intestine in male; two opposed reflexed ovaries in female. Spicules ventrally curved, capitulum not offset and velum well developed. Three tubular precloacal supplements. Conico-cylindrical tail. Three caudal glands ending in a spinneret.

Type species: Spirodesma magdae nov. gen. nov. sp.

Description. Holotype ( Figures 2 and 4): Cylindrical body, tapered towards both extremities. Cuticle with transverse annulations, less obvious in head (1 µm width) than in tail (2 µm width) region. Head not set off as distinct capsule. Anterior sensilla arrangement 6+6+4. Cephalic sensilla papilliform. Amphids unispired with circular amphideal fovea, turned ventrally, half surrounded by annulations, and 5 µm from anterior end. Subcephalic setae not present. Somatic papillae arranged symmetrically and in pairs laterally along the body. Buccal cavity with 3 equal teeth, 1 dorsal and 2 ventrosublateral. Pharynx muscular, with well-developed spherical and terminal esophageal bulb, occupying 75% of corresponding body width, its lumen wall strongly cuticularized and musculature with median protoplasmatic interruption. Nerve ring at 65% of total pharynx length from anterior end. Secretory-excretory pore not observed. Excretory gland 134 µm from anterior end. One anterior testis lying left of intestine. Spicules ventrally curved, capitulum not offset, and velum well developed. Gubernaculum without apophysis. Three tubular precloacal supplements present, anterior most papilla 33 µm distant from second papilla, and second papilla 22 µm distant from posterior most papilla; this papilla located 18 µm anterior to cloacal opening. Postcloacal setae present. Conico-cylindrical tail. Three caudal glands ending in a spinneret.

Allotype ( Figures 3 and 4): Female quite similar to male, apart from minor morphometrical differences ( Table 1) in the range of body lengths. Sexual dimorphism not observed. Two opposed reflexed ovaries present, and vulva at 42% distance from anterior end.

Paratype: Juvenile quite similar to adult, apart from minor morphological differences ( Table 1), and the type of cephalic papillae, which are setiform ( Figure 2).

Differential diagnosis: Table 2 lists the features of all genera belonging to the subfamily. The most similar genus to Spirodesma nov. gen. is Chromaspirina , but the new genus has strong characters distinct from this. Spirodesma nov. gen. and species of Chromaspirina have a rounded head, annulated cuticle, spiral amphideal fovea, and conical tail ( Muthumbi et al. 1995). However, in Chromaspirina the buccal cavity is well developed, with a large, pointed, anteriorly-directed dorsal tooth and two smaller subventral teeth, no ventral gland, and spicules with a capitulum ( Muthumbi et al. 1995); whereas Spirodesma nov. gen. has a small buccal cavity with 3 teeth (equally sized), 1 dorsal and 2 ventrosublateral, ventral gland and capitulum not offset. Furthermore, most species of Chromaspirina either do not form a bulb or have a pyriform bulb ( C. cylindrocollis Cobb, 1920 ; C. parma Ott, 1972 ; C. lunatica Gerlach, 1963 ), differing from Spirodesma nov. gen., which has a muscular pharynx with a well-developed spherical and terminal esophageal bulb.

The cuticle, the size of the 3 teeth and the unique amphids shape distinguish Spirodesma magdae nov. gen. nov. sp. as a new genus and species within Spiriniinae . The presence of these 3, similarly sized, teeth make it necessary to emend the diagnosis of Spiriniinae .

Emended diagnosis of the subfamily Spiriniinae Gerlach & Murphy, 1965

Body cuticle finely or sometimes coarsely striated. Head not demarcated as a cephalic capsule. Amphideal fovea a simple spiral, usually located far anterior on the body. Buccal cavity rather small, from minute to medium-sized, with a distinct or a minute dorsal tooth; 2 smaller ventrosublateral teeth may be present or absent; or 3 teeth of the same size.