Thoracostoma igniferum, 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 : 33-35

THORACOSTOMA IGNIFERUM SP. NOV. (CLADE III)

( FIG. 9A–D, TABLE 6)

Diagnosis: Thoracostoma igniferum sp. nov. closely resembles T. trachygaster and T. fatimae sp. nov. but can be distinguished from both by the irregular posterior edge of the cephalic capsule and the two internal subdorsal tropis-like projections in the wall of the cephalic capsule (only visible in crosssection). DNA sequences of the mitochondrial COI gene and the nuclear ITS and D2D3 regions differ from those of T. trachygaster in 10.9–13.3, 5.2– 5.5, and 1.0–1.1%, respectively, and from those of T. fatimae in 9.0–10.9, 6.7–6.9, and 0.8–1.0%, respectively.

Etymology: The name refers to the Latin word ‘ignis’, which means fire. It refers to the irregular undulations in the posterior edge of the cephalic capsule, which resemble flames.

Specimens: Eleven (eight males, three females)

Type material: Holotype 2D24C10 (male). Paratypes 2D12C10 (female), 3D18C10 and 5D12C10 (males), and the holotype deposited in the Royal Belgian

The individuals are indicated by the voucher code. The first individual (2D24C10) 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.

Institute of Natural Science ( RBINS) – Brussels, with the accession numbers RIT784 (holotype) and RIT785-RIT787 (paratypes). Three additional paratypes (6D12C10, 3D13C10, and 5D24C10) have been deposited in the Zoology Museum of Ghent University , under the numbers UGMD104120 – UGMD104122 . DNA material of these seven specimens is available in the Zoology Museum of Ghent University , under the numbers UGMD125007 – UGMD125013 . DNA sequences of specimen 3D13C10 are available in GenBank under the accession numbers FR853134 ( COI), FR853144 ( ITS), FR853143 (D2D3).

Description: Body long, cylindrical, and ventrally curved; clearly anteriorly tapered in anterior neck region. Body cuticle smooth except for fine striations in head region and appearing wrinkled (rugose) in posterior precloacal region in male. Eyespot, laterally in anterior neck region conspicuous. Lip region divided into six lips; anterior sensilla arranged in an anterior crown of six inner labial papilla and a second crown of six outer labial and four cephalic setae (2–4 Mm long). Cervical setae arranged in six rows. Cephalic capsule well developed, anteriorly with slightly marked lobes and a clear ventral tropis projecting anteriorly. Posterior edge of the cephalic capsule with irregular undulations, more or less attenuated and divided into six lobes by narrow incisions, ending anteriorly in circular fenestrae showing slight variation in shape and leaving space for innervations of anterior sensilla and amphids. In crosssection, two short, pointed subdorsal tropis-like projections in the internal wall of the cephalic capsule visible at level of dorsal tooth. Amphidial fovea shieldshaped to circular, never completely surrounded by the cephalic capsule. Buccal cavity with a short blunt dorsal tooth. Pharynx without bulb, surrounded by nerve ring at about one third of the total pharynx length from anterior end. Cardia with triangular shape, projecting to the lumen of the intestine. Three caudal glands extending anteriorly beyond rectum.

Males: Ventral surface at cloaca level with very minute protuberances until about the most anterior subventral setiform copulatory supplements. The ventromedian copulatory supplement is cyathiform and winged. Pair of curved spicules with the median portion more dilated. Gubernaculum with duplicated apophysis and the crura with membrane embracing the spicule. Gonads diorchic with opposed testes.

Females: Vagina at 62% of the body. Intracuticular granules surrounding the transverse vagina present. Gonads amphidelphic with reflexed ovaries.

Type locality: Specimens collected from stranded holdfasts of Macrocystis sp. in Ventura Beach, California, USA .

Remark: The juveniles of both species can be easily confused with juveniles and adults of another common co-occurring nematode species Thoracostoma microlobatum (Allgén, 1947) . It is because of the fact that the cephalic capsule has several perforations in the juvenile, that tend to fuse or disappear along the development. In T. microlobatum those perforations persist until the adulthood. Hence, identifying the species based on juveniles may cause misidentifications.

Figures

Figure 9. Morphology of Thoracostoma igniferum 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 with irregular undulations of the posterior edge (PCC) and amphid (AM); D, cephalic capsule at middle level with the ventral tropis (T).