Thoracostoma fatimae, Oliveira & Decraemer & Holovachov & Burr & Ley & Ley & Moens & Derycke, 2012

Oliveira, Daniel Apolônio Silva De, Decraemer, Wilfrida, Holovachov, Oleksander, Burr, Jay, Ley, Irma Tandingan De, Ley, Paul De, Moens, Tom & Derycke, Sofie, 2012, An integrative approach to characterize cryptic species in the Thoracostoma trachygaster Hope, 1967 complex (Nematoda: Leptosomatidae), Zoological Journal of the Linnean Society 164 (1), pp. 18-35 : 30-33

THORACOSTOMA FATIMAE SP. NOV. (CLADE I)

( FIG. 8A–D, TABLE 5)

Diagnosis: Thoracostoma fatimae sp. nov. is morphologically nearly identical to Thoracostoma trachygaster but can be distinguished from the latter by spicule length (100–123 Mm in T. fatimae sp. nov. vs. 124–173 Mm in T. trachygaster in the current study). The new species also closely resembles T. igniferum sp. nov., the second new species described in this contribution, but can be clearly differentiated by the cephalic capsule, without irregular undulations as in T. igniferum sp. nov. Thoracostoma fatimae sp. nov., although morphologically very similar to T. trachygaster , was supported as a valid taxon by molecular analyses. Phylogenetic trees based on nuclear and mitochondrial markers showed it to be genetically more closely related to T. trachygaster than to T. igniferum . The I3M11 mitochondrial cytochrome oxidase c subunit I (COI) sequences of T. fatimae are 5.7–8.2% divergent from those of T. trachygaster , and 9.0–10.1% divergent from those of T. igniferum . Nuclear internal transcribed spacer (ITS) sequence divergence ranges between 3.4–3.7% with T. trachygaster , and between 6.7–6.9% with T. igniferum . Divergence ranges of the nuclear D2D3 sequences of the 28S rDNA were small (0.7–1.0 and 0.8–1.0%, respectively).

Etymology: The new species is a homage to my mother Fátima Oliveira, who provided substantial emotional support during this study.

Specimens: Eighteen (16 males, two females).

Type material: Holotype: 3D31E10 (male). Paratypes 1D31E10 and 2D31E10 (two males), and 4D31E10 (female), along with the holotype are deposited in the Royal Belgian Institute of Natural Science ( RBINS) – Brussels, under the numbers RIT780 (holotype), RIT781-RIT783 (paratypes) . Paratypes 4D18C10 and 6D25C10 (two males) and 7D25E10 (female) are deposited in the Zoology Museum of Ghent University , under the numbers UGMD104117 – UGMD104119 . DNA material of the seven specimens is available in the Zoology Museum of Ghent University , under the numbers UGMD125000 – UGMD125006 . DNA sequences of T. fatimae specimens that were video vouchered (Derycke et al., 2010a) are available in GenBank under the accession numbers FN433782 , FN433787 , FN433788 , FN433790 , FN433799 , FN433803 – FN433806 ( COI) , FN433920 – FN433921 ( ITS), FN433908 , FN433911 (D2D3) . COI accession numbers of specimens 4D18C10, 6D25C10, 1D31E10, and 7D25E10 are FR853137 – FR853140 .

Description: Body long, largely cylindrical, neck region anteriorly tapered, tail short i.e. about one anal body width long, dorsally convex and posterior end blunt, rounded. Posterior body region ventrally curved upon fixation, more pronounced in male compared to female. Obvious eyespots present on both sides anteriorly in neck region i.e. at two to four times lip region width from anterior end. Cuticle appearing smooth but with very fine transversal striation visible in head region. In males, cuticle with rugose appearance in ventral region from cloaca extending until the anterior-most subventral setiform supplement. Lip region with six lips, anterior sensilla arranged in two crowns (pattern 6 + 10). Inner labial sensilla of the anterior-most crown papilliform and outer labial sensilla and cephalic sensilla of the posterior crown setiform (2–4 Mm long). Cervical setae arranged in six rows, with visible sensillar canal and dendritic processes between the cephalic capsule suture and eyespot. Cephalic capsule well developed, with slightly marked anterior lobes except for the ventral tropis orientated to the anterior end. Posterior border capsule divided into six lobes by narrow incisions through which pass the innervations of the anterior sensilla and amphids; incisions ending in circular fenestrae, showing some slight variation in shape. Amphidial fovea shield-shaped to circular. Buccal cavity with a short blunt dorsal tooth. Pharynx without bulbus and with nerve ring located about one third of the total pharynx length from anterior end. Cardia triangular in longitudinal optical section, projecting into intestinal lumen. Three caudal glands, extending anteriorly beyond the rectum.

Males: Reproductive system diorchic, posterior testis reflexed. Precloacal ventral body wall appearing rugose because of numerous minute protuberances extending more or less until the anterior-most setiform subventral copulatory supplements arranged in a longitudinal series. Single ventromedian copulatory supplement cyathiform and winged. Spicules, ventrally curved with mid-blade portion widened.

The individuals are indicated by the voucher code. The first individual (3D31E10) is the holotype.

Abbreviations: a, body length/body width; abd, anal body diameter; b, body length/pharynx length; c, body length/tail length; cbd, corresponding body diameter; f, female; m, male; Max., maximum; mbd, maximum body diameter; Min., minimum.

Gubernaculum with two apophyses and the crura with membrane embracing the spicule.

Female: Reproductive system didelphic, amphidelphic, with reflexed ovaries. Vulva, a transverse slit in ventral view, surrounded by a punctuated cuticle and located at 62% of total body length from anterior end.

Type locality: Holotype collected from stranded holdfasts of Macrocystis sp. in Malibu Beach , California, USA. Additional locations where specimens were collected are Ventura Beach and Torrey Pines, California, USA.

Figures

Figure 8. Morphology of Thoracostoma fatimae sp. nov. Pictures are from the holotype. A, tail region with spicules (SP), gubernaculums (GU), apophysis (AP), and ventromedian precloacal supplement (PS); B, anterior region with ocelli (ES) and nerve ring (NR); C, head region with a well-developed cephalic capsule (PCC), amphid (AM), and cephalic setae (CS); D, cephalic capsule at middle level with the ventral tropis (T).