Maldivea complexa, Federica & Maria, 2019

Federica, Semprucci & Maria, Balsamo, 2019, A new species of Maldivea Gerlach, 1962 (Nematoda, Oxystominidae) from Felidhoo atoll (Maldives, Indian Ocean) and an emended diagnosis of the sub-family and genus, Ecologica Montenegrina 20, pp. 1-9 : 3-6

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 ).

Figures

Figure 1. Type localities of Maldivea xarifae and M. complexa n. sp.

Figure 2. Drawing of the total body of the male of Maldivea complexa n. sp. Scale bar: 100 µm.

Figure 3. Drawings of the male of Maldivea complexa n. sp. A) Detail of the anterior end of the male. B) Detail of the amphideal fovea of the male. C) Detail of the copulatory apparatus and caudal region. Scale bar: A: 10 µm, B: 50 µm.

Figure 4. Light micrographs of the male of Maldivea complexa n. sp. A,B) Detail of the buccal cavity, C) Detail of amphideal fovea, D) Copulatory apparatus, E) Precloacal sub-ventral pairs of short and stout setae close to the cloacal opening, F) Detail of the precloacal sub-ventral pairs of short and stout setae in the elevation of the cuticle, G) Details of the post-cloacal setae and tail tip. Scale bars: A-B: 5 µm, C,E: 10 µm; D, F,G: 20 µm.

Tables

Table 1. Measurements of the male of Maldivea complexa n. sp. (absolute numbers in µm).

Character	male
total L	4655
hd	11
length of labial sensilla	2
length of anterior cephalic sensilla	3
length of posterior cephalic sensilla	6
cbd at level of posterior cephalic setae	15
distance from anterior edge to cephalic setae	13
distance from anterior edge to base of buccal cavity	7
distance from anterior to anterior edge of amphid	15
diameter of amphid	6
cbd at widest part of amphid	16
distance from anterior edge to nerve ring	502
cbd at nerve ring	40
distance from anterior edge to base of oesophagus	1166
cbd at base of oesophagus	53
length of cardia	20
mbd	60
distance from anterior to anus	4491
abd	54
length of spicules measured along the arc	84
length of gubernaculum	50
length of tail	164
a	78
b	4
c	28
c'	3
s'	1.6