A new species of Trileptium ( Nematoda : Thoracostomopsidae ) from Bahia , Brazil

A new species of a free-living marine nematode found in Brazil is described: Trileptium ribeirensis sp. nov. The type material is deposited in the Nematoda collection of the Museu de História Natural da Bahia, located at the Universidade Federal da Bahia. Trileptium includes eleven valid species of nematodes that have teeth and jaws positioned forward. The species was collected with the help of corers (3.5 cm in diameter and 30 cm long) on a sandy beach in Bahia. This species is distinguished from its congeners based on a combination of characters of the male (cuticle, buccal cavity, supplement and gubernaculum). An updated taxonomic key to the genus is presented.

ZOOLOGIA 33(1): e20150043 | DOI: 10.1590/S1984-4689zool-20150043 2 / 10 as recreational and construction of habitations and commercial facilities.It consists of a low-energy wave coastline (less than 0.5 m height), dispersed to a distant part of the coast, and with the absence of rip currents (SiLVa et al. 2010).
The beach sediment is characterized by quartz grains and fragments of carbonate skeletons of marine organisms', and mostly medium-sized sand grains (ViLaS BoaS & BittenCourt 1992).The lack of fine fraction is due to turbulence, which conveys the material up to 0.25 mm in diameter.The slope ranges from 5 to 10 degrees, and the width varies from 20 m to 35 m at low tide (SiLVa et al. 2010).
Nematode sampling was conducted in February, 2009, during a dry period with low spring tide.Samples were taken using corers of 3.5 cm in diameter and 30 cm long, divided into three strata: 0-10, 10-20, and 20-30 cm related to sediment depth.They were traced in three transects perpendicular to the waterline in the intertidal zone, with three points representing upper, middle and lower regions.Samples were fixed in saline buffered formalin (10%) and rinsed by hand in elutriation sieves with 0.5 mm and 0.045 mm.Nematodes were diaphanized using glycerol-ethanol solutions, according to the de GriSSe (1969) protocol, and arranged on slides, following the method by CoBB (1917).
The description and drawings of the animals were performed under an Olympus optical microscope (CX31), with attached drawing tube.The morphometry was performed using images taken by camera model QImaging Go-3, using the Q Capture software.All measurements are expressed in micrometers (µm).Images were imported into the Image-Pro Insight software for analysis.Photographs of the animals were taken under an Olympus microscope (BX53) with DIC.
Animals are deposited in the Nematode collection of the Museum of Zoology, a unit of the Museu de História Natural da Bahia (MHNBA), located at the Universidade Federal da Bahia.The institution is recognized by the Brazilian Ministry of Environment.

TAXONOMY
Phylum Nematoda Potts, 1932Order Enoplida Filipjev, 1929Suborder Enoplina Chitwood & Chitwood, 1937Enoploidea Dujardin, 1845Thoracostomopsidae Filipjev, 1927(adapted from Lorenzen 1994, SmoL & CoomanS 2006, niChoLaS 2007) Diagnosis.Presence of three prominent lips.Setiform inner labial setae (papilliform only in Fenestrolaimus), whereas the outer labial and cephalic setae are robust and long.Cephalic organs are usually present, situated frontally or ventrofrontally in relation to the lateral cephalic setae exhibiting a variable form.Non-spiral and small amphidial fovea located posterior to the cephalic capsule are most likely absent.The inner layer of the cuticle forms a cephalic capsule, and the pharyngeal muscles are attached to it.Conical buccal cavity is tapered with three jaws and three conical teeth associated with the base of the jaws (one dorsal and two ventrosublateral) or a long eversible spear in Thoracostomopsinae members.Only dorsolateral orthometanemes with a robust scapulus occur but without caudal filament.The endings of the epidermal glands are particularly well differentiated.Female reproductive system is didelphic-amphidelfic, with antidromously reflexed ovaries.Caudal glands can be found in the pre-caudal region.
Diagnosis.Cuticle may be smooth or slightly striated.Three small lips, one dorsal and two subventral.The cephalic setae are arranged in three circles: six inner labial, six outer labial and four cephalic.Males also have a circle with subcephalic setae.The buccal cavity consists of one or three teeth, with similar sizes, well developed and positioned near the opening of the cavity.Subventral teeth may be located at the same level or more anterior to the dorsal tooth.Underdeveloped jaws may or may not be present.The genus has variable shapes and arrangements of spicules and gubernaculums.A pre-cloacal supplement may be present or absent.
Figs. 2-17, Table 1 urn:lsid:zoobank.org:act:1047B3EC-5851-43A7-96D5-37D49CAF6FB0 Diagnosis.Slightly striated cuticle, visible in the anterior region and through the tail.Three lips.Cephalic arrangement in three rings, outer-labial setae greater than cephalic setae.Males with two pairs of sub-cephalic setae.Narrow buccal cavity with three jaws and three isometric teeth, all on the same level and across the transverse mandibular bar.Males with two opposite testis left to the intestine.Simple shaped spicules.Laminar gubernaculum with a dorsal-caudal apophysis.Tubular pre-cloacal supplement.Conical tail tapering at the terminal portion.
Type material.Holotype (male): Brazil, Bahia: Salvador (Ribeira Beach, 12°55'S, 38°30'W), 10-20 cm depth, collected with a corer, middle region, coarse sand, 45 µm sieve), 11.Description.Holotype: Slender and elongated body, particularly in the extremities (Length: 3713 µm).Slightly striated cuticle, visible in the anterior region, even after the nerve ring, and little less in the cloaca region extending through the tail.Narrow head with a sclerotized cephalic capsule.Presence of three lips.Cephalic arrangement in 6 + 6 + 4: six inner-labial thick and short setae (6 µm) and six outer-labial setae (50 µm) greater than cephalic setae (30 µm).Two pairs of sub-cephalic setae were also observed (31 µm).Somatic setae (13 µm) up to the nerve ring and absent in the rest of the body.Presence of orthometanemes, with one complete filament with 24 µm.Narrow buccal cavity with three jaws (20 µm) and three isometric teeth (13 µm), all on the same level and across the transverse mandibular bar.Pocket-shaped amphidial fovea, near the base of the cephalic capsule, which occupies 17% of the corresponding body diameter.Circular cephalic ring positioned between the inner labial setae circle and the outer labial setae circle (1 µm from the anterior end).Cylindrical pharynx with crenated contour and without a terminal bulb (742 µm).Triangular cardia inserted  Allotype: Similar to the description of the male, except for the sub cephalic setae, which are present only in males.The sub cephalic setae is a sexual dimorphism in this species.Females had a didelphic reproductive system with opposite reflected ovaries (anterior 1984 µm, and posterior 1990 µm) left to the intestine.The vulva is located 2700 µm from the anterior end, equivalent to 63% of the body length.Only non-gravid females were observed.
Etymology.The species' name honors the site where the animals were collected.This is the first description of a new species of Nematode for Ribeira Beach, Salvador, Bahia, Brazil.

DISCUSSION
The presence of sub-cephalic setae only in males indicates a type of sexual dimorphism.This dimorphism is constant in the genus, being also present in T. australis, T. longisetosum, T. otti and T. salvadoriense.
Trileptium ribeirensis sp.nov.was characterized as a new species based on the fact that males have a slightly annulated cuticle, a buccal cavity with three isometric teeth on the same level and across the transverse mandibular bar, a supplement  2), cephalic ring and amphid (3), orthometaneme (4) and teeth and jaws (5); posterior region with emphasis on the supplement ( 6) and the spicules and gubernaculum (7).Scale bars = 20 µm.and gubernaculum with dorsal-caudal apophysis that does not loop over spicules (Table 2).Following GerLaCh (1952), T. subterraneum has a gubernaculum with apophysis, similar to the new species.However, T. subterraneum does not have an annulated cuticle, and its buccal cavity contains a single onchium.Differently, T. ribeirensis sp.nov.has a slightly annulated cuticle and three isometric teeth.

Table 1 .
Males and females measurements (µm) of Trileptium ribeirensis sp.nov.(cbd) corresponding body diameter; (V%) position of vulva as a percentage of body length from the anterior end; (a) body length divided by maximum body diameter; (b) body length divided by pharyngeal length; (c) body length divided by tail length; (c') tail length divided by body width at the anus or cloacal opening.