Trileptium Cobb, 1933

De Souza, João V. & Maria, Tatiana F., 2023, Taxonomic review of Thoracostomopsidae (Nematoda, Enoplida): state of the art, list of valid species and dichotomous keys, Zootaxa 5361 (4), pp. 463-496 : 488-489

Genus Trileptium Cobb, 1933

Syn. Trilepta Cobb, 1920

The type species previously named Trileptium guttata Cobb, 1920 was firstly described as Trilepta , but as this genus name was already pre-ocuppied, it was re-named ( Cobb, 1933). Thirty years later, Trilepta subterranea Gerlach, 1952 was described, this species differs from T. guttatum by the presence of a precloacal supplement in the last species. Species names were readequated to Trileptium guttatum ( Cobb, 1920) Cobb, 1933 and Trileptium subterraneum ( Gerlach, 1952) Cobb, 1933 to comply with the rules of Latin grammar ( Gerlach & Riemann, 1974). Gerlach (1955) and Gerlach (1956b) contributed to increase the richness of the genus by describing Trileptium salvadoriense Gerlach, 1955 and Trileptium stylum Gerlach, 1956b from El Salvador and Santos-Brazil, respectively. The first dichotomous key was developed by Wieser (1959) including all the former described species and Trileptium iacobinum Wieser, 1959 using the male sexual apparatus as a differential character. Later, five species were added to the genus Trileptium ayum Inglis, 1964 ; Trileptium longisetosum Inglis, 1966 ; Trileptium parisetum Warwick & Platt, 1973; Trileptium otti Jensen & Gerlach, 1976 and Trileptium americanum Keppner, 1987b . The first three species are very similar, but they differ by the number and distribution of cephalic setae and the male copulatory apparatus. In the beginning of the tweenty-first century, two other species ( Trileptium australis Nicholas, 2007 and Trileptium ribeirensis Vilas Boas, Silva, Alves, Castro & Pinheiro-Junior, 2016 ) were described from southeastern Australia and Brazil, respectively. The taxonomic key developed by Nicholas (2007) was updated by Vilas Boas et al. (2016) by adding its new species. Here, we provide a graphical design to the dichotomous key of Vilas Boas et al. (2016).

Diagnosis from Vilas Boas et al. (2016): Cuticle may be smooth or slightly striated. Three small lips, one dorsal and two ventrosublateral. 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. Ventrosublateral teeth may be located at the same level or more anterior to the dorsal tooth. Underdeveloped mandibles may or may not be present. The genus has variable shapes and arrangements of spicules and gubernaculums. A precloacal supplement may be present or absent.

Number of valid species: 12

1. Trileptium americanum Keppner, 1987b (Florida, USA)

2. Trileptium australis Nicholas, 2007 (South Eastern Australia)

3. Trileptium ayum Inglis, 1964 ( South Africa)

4. Trileptium guttatum ( Cobb, 1920) Cobb, 1933 (Massachusetts, USA)— type species

5. Trileptium iacobinum Wieser, 1959 (Washington, USA)

6. Trileptium longisetosum Inglis, 1966 ( South Africa)

7. Trileptium otti Jensen & Gerlach, 1976 (Tucker’s Town, Bermuda)

8. Trileptium parisetum Warwick & Platt, 1973 (Firemore Beach, Scottish)

9. Trileptium ribeirensis Vilas-Boas, Silva, Alves, Castro & Pinheiro-Junior, 2016 (Bahia, Brazil)

10. Trileptium salvadoriense Gerlach, 1955 ( El Salvador)

11. Trileptium stylum Gerlach, 1956b (Rio de Janeiro, Brazil)

12. Trileptium subterraneum ( Gerlach, 1952) Cobb, 1933 (Meditarranean)