Croconema fortis, Larrazábal-Filho, Alexandre L., Silva, Maria Cristina Da & Esteves, André M., 2015

Larrazábal-Filho, Alexandre L., Silva, Maria Cristina Da & Esteves, André M., 2015, Four new species of free-living marine nematodes of the family Desmodoridae (Nematoda: Desmodorida) and a redescription of Desmodora nini (Inglis, 1963) from the continental shelf off northeastern Brazil, Zootaxa 4021 (1), pp. 63-92 : 75-76

Croconema fortis sp. n.

(measurements in Table 4 , Figs 8 , 9 , 10 ).

Type material: Holotype Male adult MNRJ 346 (03°30’00”S, 038°15’00”W) collected in June 2009, in the Potiguar Basin, between 30 and 35 m deep. Sediment: coarse bioclastic sand.

Paratype female: Adult MNRJ 347 (03°15’00”S, 038°45’00”W) from the Potiguar Basin, between 30 and 35 m deep. Sediment: coarse lithoclastic sand.

Other paratypes: 2 females (181 and 182 LMZOO-UFPE), 7 males (176-180 LMZOO-UFPE) and 5 J1 (183 LMZOO-UFPE) collected on same date as holotype.

Etymology. Species name refers to the large robust body, from L. fortis , strong.

Description. Holotype male ( Figs 8 , 10 ) Body long and cylindrical, yellowish brown in colour, with strong cephalic capsule and conical tail. Cuticle strongly annulated except on cephalic capsule and non-annulated tail end. Somatic setae arranged in six longitudinal rows, alternating long and short setae. Head wide in diameter, with long cephalic capsule. Fovea amphidialis loop-shaped. One large dorsal tooth and two subventral teeth, one circle of denticles (parallel to teeth) and six lips with 12 folds. Anterior sensilla arrangement: six inner labial, six outer setae, four cephalic setae positioned at midlevel of fovea amphidialis, and two circles of six subcephalic setae below fovea amphidialis. Pharynx with terminal bulb, with sclerotized lumen divided into distinct regions. Nerve ring not observed. Ventral gland and secretory-excretory pore not observed. Cardia inserted in intestine. Two small pre-cloacal supplements, first more sclerotized than second, placed 4.5 µm apart. Reproductive system with outstretched testis. Long, thin spicules with rounded capitulum. Gubernaculum composed of two parts: laminar which is thin and distally curved and a dorso-caudal apophysis. Spinneret visible. In addition to the somatic setae along the body, this species has two subventral rows of thick spine-like setae that arise proximally in the second pre-cloacal supplement and extend posterior to the cloaca ( Fig. 10 E). Short conical tail, distal portion without annulation, and three terminal papillae.

Female ( Figs 8 , 9 ) Similar to male, except that fovea amphidialis is 58% smaller. Reproductive system with paired opposite and reflexed ovaries. Vulva as transverse slit. Vagina vera short, vagina uterina with sphincter muscle. Egg found in oviduct ( Fig. 9 D). Short conical tail.

Juveniles 16 juveniles found, all in the first stage of development. Identical to adults except for size and in having visible nerve ring and absence of lateral row of setae (pre-cloacal region) ( Fig. 10 ).

Diagnosis and relationships. The main characters of Croconema fortis sp. n. are: buccal cavity with large dorsal tooth and two subventral teeth. Long cephalic capsule. Two circles of six subcephalic setae below the fovea amphidialis. Two small pre-cloacal supplements and two subventral rows of thick setae.

Croconema fortis sp. n. is similar to Croconema mammillatum Steiner & Hoeppli, 1926 and Croconema stateni Allgén, 1928 , in having denticles in the oral cavity. However, it differs from C. mammillatum in the absence of a mammillate apparatus, and from C. mawsonae Inglis, 1968 in the presence of subventral spines on the tail. Croconema fortis sp. n. is also similar to C. cinctum Cobb, 1920 ; C. floriani Verschelde et al. 2006 ; C. mediterraneum Wieser, 1954 ; C. sphaericum ( Kreis 1928) and C. stateni Allgén, 1928 with respect to the presence of copulatory spines as precloacal supplements. Of these species, the most similar is C. stateni , as redescribed by Pastor de Ward (1988). Despite the similarities, the specimens studied here are considered a new species, due to the presence of only two circles of subcephalic setae ( C. stateni = 3 circles); spicules with a rounded capitulum (hookshaped in C. stateni ); gubernaculum formed of two parts: a narrow and distally curved laminar, and a dorsal-caudal apophysis (apophysis absent in C. stateni ); and finally, C. fortis sp. n. has much smaller subventral ornaments on the non-annulated tail end.

Figures

FIGURE 8. Croconema fortis sp. n. Holotype MNRJ 346 and Paratype female MNRJ 347 A and B: overview (male and female, respectively). C: somatic setae. D: tail region (female). E: dorsal tooth. F: posterior region (spicules and pre-cloacal supplements). G: dorsal tooth (cephalic region of female). H: fovea amphidialis (cephalic region of male). I: vulva opening.

FIGURE 9. Croconema fortis sp. n. Paratype female MNRJ 347 - A: overview. B: head region. C: anterior region. D: ovary and vulva opening. E: tail region.

FIGURE 10. Croconema fortis sp. n. Holotype MNRJ 346 - A: overview. B and D: head region. C: anterior region. E: posterior region and pre-cloacal supplements. F: copulatory apparatus. Paratype Juvenile I – H: overview and G: head region.