Draconema fluminensis, Venekey & Lage & Genevois, 2005

Venekey, Virág, Lage, Luciana Monteiro & Genevois, Verônica Da Fonsêca-, 2005, Draconema brasiliensis and Draconema fluminensis (Chromadorida, Draconematidae): two new species of free living nematodes from a rocky shore affected by upwelling on the Brazilian coast, Zootaxa 1090 (1), pp. 51-64 : 58-64

Draconema fluminensis sp.n. ( Figs 4A–E , 5A–E )

Holotype: male, slide UGMD 104089 in RUG . Allotype: female, slide UGMD 104090 in RUG . Paratypes: 6 males, slides 15–20NM and 2 females, slides 21–22NM in LMZOO­ UFPE .

Type locality: Pedra Vermelha, Arraial do Cabo­RJ, Brazil.

Habitat and distribution: marine intertidal phytal environment on granite rocky shore formation

Etymology: named after Rio de Janeiro state. In Portuguese who is born in Rio de Janeiro State is denominated: “fluminense”.

Measurements

Holotype male: L= 1185 m; CAT=12; t= 102 m; CATat= 25 m; CATpt= 29 m; ABD= 41 m; tmr= 42 m; Ph= 115 m; Wapr= 2 µm, SlAT1= 56 m; SvAT1= 47 m; SlATL= 45 m; SvATL= 32 m; spic= 80 m; gub= 44 m; b = 9,3; c = 8,5.

Allotype female: L= 1312 m; CAT=12; t= 140 m; CATat= 26 m; CATpt= 28 m; ABD= 31 m; tmr= 49 m; Ph= 127 m; Wapr= 2 µm, SlAT1= 58 m; SvAT1= 50 m; SlATL= 45 m; SvATL= 34 m; V %=52; b=10,3; c=9,4.

Paratype males (n=6): L= 943–1057 m; CAT=12; t= 114–153 m; CATat= 20–26 m; CATpt= 26–31 m; ABD= 38–50 mm; tmr= 43–45 m; Ph= 102–140 m; Wapr= 2 µm, SlAT1= 54–59 m; SvAT1= 42–48 m; SlATL= 44–48 m; SvATL= 29–36 m; spic= 76–85 m; gub= 31–41 m; b=7,4–9,1; c = 6,7–11,6.

Paratype females (n=2): L= 980–1287 m; CAT=12; t= 89–115 m; CATat= 27 m; CATpt= 29–31 m; ABD= 31–38 m; tmr= 49–50 m; Ph= 127–140 m; Wapr= 2 µm, SlAT1= 49–53 m; SvAT1= 47–48 m; SlATL= 40–45 m; SvATL= 33–34 m; V %=55– 64; b=7,7–9,2; c=8,5–14,5.

Description

Males

Body small and typically shaped as in other Draconema specie s with swollen pharyngeal region ( Fig 4A ). The first 15–16 post­rostral annules are prominently enlarged and present subcuticular markings. Cuticle with annulations extending from the nonannulated cephalic region (helmet) to the caudal region where the non­annulated portion presents minute punctuations. Somatic setae with variable lengths present along the body arranged in 8 longitudinal rows, 2 subdorsal, 4 sub­lateral and 2 subventral.

Swollen pharyngeal region 10–14% of total body length ( Fig 4B ) and slightly more rounded than in Draconema brasiliensis n.sp (relation between length and width: 1.7). Amphids large, loop­shaped, with the ventral arm often longer than the dorsal arm, positioned slightly dorsal on the non­annulated part of the helmet.

Six lips can be visualized at the anterior portion of the helmet. Each lip has one associated sensory setae 9–11 m long. Helmet length varying from 27 to 34 m long.

Twelve cephalic adhesion tubes (CAT), paired and in two transverse rows on the dorsal side of the helmet. Anteriorly positioned CAT shorter than those more posteriorly. In holotype the pair most anterior has 25 m long while the most posterior has 29 m long.

The buccal cavity is minute and without teeth. Pharynx with swollen anterior corpus and posterior bulb (dumbbell­shaped) separated by a constricted region encircled by the nerve ring (posterior bulb longer than anterior corpus). Pharyngeal glands not observed. Intestine larger anteriorly, becoming narrow posteriorly and having differentiated rectum. Secretory­excretory gland not observed.

All posterior adhesion tubes anteriorly to cloaca ( Fig 4D ), 9 sublateral and 16–17 subventral PATs at each side of the body. Both PATs become shorter from anterior to posterior part of the body. The sublateral PATs are always longer than the equivalent positioned subventral ones (i.e. first sub­lateral PAT 56 m long, first sub­ventral PAT 47 m long in holotype).

The reproduction system is composed by one outstretched testis directed anteriorly and situated at the left side of intestine. Cephalated spicules, equals in size and shape, varying from 76 to 85 m long (1.7–2.0 in relation to ABD) ( Fig 4C ). Gubernaculum 31– 44 m long, corpus parallel to the spicules and with a lateral wing. Four pairs of anal setae, 2 subventral and 2 sublateral, 10 – 14 m long. Two are anterior and two are posterior to the anus.

Tail 2,5 anal diameters long in holotype (in paratypes is 2.8–3.7). Non­annulated part of the tail 29–41% of tail length. Seven pairs of setae on the non­annulated punctuated tail region ( Fig 4E ), position measured from last complete tail annule to tail tip; 4 subdorsal pairs; 1 long pair just posterior to last complete tail annule (40–58 m long), 1 short pair just posterior to long pair, 1 short pair about 40% and 1 short pair about 60%; 2 subventral pairs, 1 short pair about 50% and 1 short pair about 60%; 1 lateral short pair about 75%. Caudal glands are extended to the pre­caudal region.

Females

Similar to males in most morphological aspects ( Fig 5A ). The amphids are conspicuously inverted “U” shaped. Swollen pharyngeal region 10–13% of total body length ( Fig 5B ). Helmet length 31 to 38 m long. Reproductive system didelphicamphidelphic with antidromously reflexed ovaries, both at the left side of the intestine ( Fig 5C ). Vulva, a transverse slit and protruded, lying between 52–64% of body length ( Fig 5D ). Two pairs of paravulvar setae, 1 anterior and 1 posterior to the vulva (anterior 8,6 m long and posterior 8.5– 10 m long). Vagina sclerotized. All PATs between the vulva and anus, intermingled with somatic setae ( Fig 5E ). One row of 14 sublateral and one of 18–19 subventral adhesion tubes at each side of the body. Anal body diameter usually smaller than in males, 31– 38 m. Position and number of setae on non­annulated tail region as in males. The length of the long pair just posterior to last complete tail annule is 48 m. Caudal glands extending anteriorly to the anus as in males.

Differential diagnosis of D. brasiliensis and D. fluminensis with related species.

Based on the revision published by Allen and Noffsinger (1978) and the description of D. japonicum made by Kito (1976 and 1979), the principal morphometrical features of the 7 species of genus Draconema and those of Arraial do Cabo can be seen in the table 01.

Considering the morphometrical features, the species of the genus Draconema are similar in many measures nevertheless the number of subventral and sublateral PATs, pairs of setae on non­annulated tail region and the length of tail, spicules and gobernaculum can be useful characters to distinguish the species within the genus.

The new species found at Arraial do Cabo are the first species between the Draconema genus with more than 14 post­rostral enlarged annules (15–16 in both new species). Before this recording D. antarcticum was the species with more number of enlarged annules (9–14).

Using the identification key present in the revision of Allen and Noffsinger (1978) we found that the most closely related species to D. brasiliensis and D. fluminensis is D. cephalatum . Both new species, apart from the number of enlarged annules mentioned before, can be diferenciated from the last one also by the length of the gobernaculum which is longer in the Brazilian species. This feature is also remarkable comparing with the other species within the genus. Other differences comparing D. cephalatum and D. brasiliensis are the longest tail of the second one and the number of pairs of setae on nonannulated tail region in females (6 to D. brasiliensis and 5 to D. cephalatum ).

The other species described in the present work, D. fluminensis , presents 7 pairs of setae on the non­annulated region of the tail. Such fact is observed for the first time within Draconema genus. Until this record a maximum of 6 pairs was known to males of D. cephalatum , D. japonicum , D. ophicephalum and females of D. chilense .

The species D. japonicum is absent from the identification key proposed by Allen and Noffsinger (1978) as was described only posteriorly by Kito (1976). This species was found until the moment only in Japan and can be distinguished from the Brazilian species by the number of post­rostral enlarged annules (8–12 in D. japonicum , 15–16 in D. braziliensis and D. fluminensis ), length of gobernaculum (21–23 m in D. japonicum , 34– 44 m in D. braziliensis and 31–44 m in D. fluminensis ) and the absence of paravulvar setae on females.

Comparing D. brasiliensis and D. fluminensis the main differences are the length of males ( D. fluminensis is always shorter than D. brasiliensis ); the swollen pharyngeal region, which is more rounded in D. fluminensis (relation between length and width is 2.0 in D. brasiliensis and 1.7 in D. fluminensis ); the width of enlarged post­rostrum annules (3 m in D. brasiliensis and 2 m in D. fluminensis ) and the number of pairs of setae on the non­annulated region of tail (6 in D. brasiliensis and 7 in D. fluminensis ).

m.

Due to the morphological and morphometrical features the two species found at the

Brazilian coast could not be considered as any of the known Draconema species dispite some similarities. Furthermore, on the rocky shores prospected, only the two species were found within Draconematidae , different from other similar works (i.e. Decraemer, 1982; Decraemer & Gourbault, 1986).

The present data alowed to emend the diagnosis of the genus Draconema in relation to the number of post­rostral enlarged annules and pairs of setae on the non­annulated region of the tail.

Figures

FIGURE 4. Male holotype of Draconema fluminensis sp.n. —A. Whole body, B. Pharyngeal region, C. Cloacal region with copulatory apparatus, D. Posterior body region with posterior adhesion tubes, E. Non­annulated punctuated tail region.

FIGURE 5. Female allotype of Draconema fluminensis sp.n. — A. Whole body, B. Pharyngeal region, C. Mid­body region with reproductive system, D. Vulva region, E. Posterior adhesion tubes.