Maldivea complexa n. sp.

Figs. 2-4; Table 1

Etymology: The species name refers to the complexity of the gubernaculum.

Material studied: one male collected by Giuseppe Baldelli on May 2005 and mounted on glycerin slide. The studied specimen is held in the author’s collection at the Department of Biomolecular Sciences (DiSB), University of Urbino, Italy .

Locality: Indian Sea, Maldivian Archipelago, Felidhoo atoll (3° 33.600’ N – 73° 29.859’ E). Samples were collected at a depth of 1.50 m in coarse sands (Fig. 1).

Description of the male: Body very long (L = 4654 µm, a = 78) and thin from the anterior end to the nerve ring region (Fig. 2). Cuticle smooth over the entire body. Six inner labial sensilla, six outer labial sensilla 3 µm long and four cephalic sensilla 6 µm long. Somatic setae about 5 µm long along the pharynx region, shorter in the remaining part of the body (~3 µm long). Anterior end truncate, buccal cavity cup-shaped and surrounded by the pharynx. Buccal wall characterized by 6 folds that are completely cuticularized (Fig. 3a, 4a,b). Distance from anterior edge to base of buccal cavity 7 µm. Amphidial aperture as a large transverse slit. Fovea large and pocket-shaped, located just after the cephalic sensilla at 15 µm from the anterior end (Fig. 3a, 4c). Diameter of the amphidial fovea 6 µm, i.e. ~36% of the cbd. Pharynx cylindro-conical very long (1166 µm long, b = 4) widening slightly as from the nerve ring region to the posterior end where the musculature appeared more developed than in the first region (Fig. 2). Nerve ring at ~ 23-43% of the PL. Cardia well-developed (~20 µm long) and embedded in the intestine. No metanemes observed.

Only anterior male gonad observed, situated ventrally to the intestine (Fig. 2). Spicules equal, strongly cuticularized and arcuate (84 µm long, i.e. 1.6 abd) (Fig. 3c, 4d). Gubernaculum without apophysis. It consists of two pieces: a wing lateral to the distal part of the spicule and a dorsal part with a complex structure of stripes (Fig. 2b, 3d). Gubernaculum lateral wing envelops the spicule for about the 60% of its length. In the precloacal region, a longer pair of setae (~7 µm long) at about 11 µm from the cloacal opening and two sub-ventral pairs of short and stout setae (~4 and 5 µm long, respectively) at about 23 and 40 µm from cloaca (Fig. 3c, 4e,f). At about 123 µm from the cloacal opening towards the anterior end, a sub-ventral pair of very short and stout setae (~3 µm long) located in an elevation of the cuticle (Fig. 3c, 4f). Five setae arranged in two sub-ventral rows in the post-cloacal region at about 58 µm from the cloaca (Fig. 3c, 4g). The first three pairs of setae are 8 µm long and the last two are shorter and stouter (~4 µm long). Tail short, 164 µm long corresponding to 29 of the ratio c and 3 of c’. Caudal glands observed. Terminal pore and canal well developed (Fig. 3c). Subterminal seta observed.

Remarks: M. complexa n.sp. is very similar to M. xarifae in the general morphology, but differs in a and c de Man ratios which are lower in the new specimens compared to those of M. xarifae (a= 78 vs. 90-106; c = 29 vs. 34-39). Also the spicule length appears greater in the new species than in the type species (84 µm long vs. 60 µm) along with the s’ ratio (1.6 vs. 1.2). However, the most evident difference between M. complexa n.sp. and M. xarifae is the more complex structure of the gubernaculum in M. complexa in which it consists of two pieces: one is a sort of long wing in the ventral part of the spicule and the other, more complex, is characterized by several curved stripes enveloping the dorsal side of the spicule distal part (Fig. 3b).