Pristionchus occultus, Aspe & James, 2017

Aspe, Nonillon M. & James, Samuel W., 2017, Pheretima apoensis, Zoological Studies 55 (48), pp. 1-16 : 10

Pristionchus occultus n. sp.

urn:lsid:zoobank.org:act:F6ECE842-DFAE-4ECA-9B21-BDD46FBB71A2 ( Figs. 4 , 5 , Fig. 2S )

Measurements: See Table 2.

Description: Stenostomatous form. Stegostom bearing conspicuous and movable dorsal triangular or diamond-shaped tooth, three bump-like (blunt) left subventral denticles apparently projecting from a common cuticular plate, and a small, short, and pointed right subventral denticle baring from flattened-triangular plate.

Eurystomatous form: Clear species-specific characters were not observed.

Male: Nine pairs of genital papillae arranged as above, where, in many individuals, pd located at the level of or slightly posterior to v7.

Female: As described above in common characters. Clear species-specific character was not observed.

Diagnosis: Pristionchus occultus n. sp. is a cryptic species of P. pacificus , P. exspectatus and P. arcanus , i.e., the species does not show a clear species-specific morphological character to distinguish it clearly from the other species. The species is also characterized by an 830-bp fragment of the SSU rRNA gene (GenBank accession number KX113518), the sequence of which is distinct from that of all other Pristionchus species, and by a gonochoristic reproductive mode.

Type host and locality: The culture from which the type specimens were obtained was originally isolated from the body of a rose beetle grub ( Coleoptera : Cetonidae) collected at Huisun, Taiwan in August 2015.

Type material: Holotype stenostomatous male (slide accession number 31493), three paratype stenostomatous males and three paratype stenostomatous females (31494- 31499) deposited in the UCRNC, Riverside, CA, USA. Three paratype stenostomatous males and three paratype stenostomatous females (SMNK- Nema-T0125– SMNK-Nema-T0130) deposited in the Natural History Museum Karlsruhe, Germany. Three paratype stenostomatous males and three paratype stenostomatous females (SMNH- Type-8797 – SMNH-Type-8802) deposited in the Swedish Natural History Museum , Stockholm, Sweden.

Type strain culture: Available as living cultures and frozen stocks under culture code RS 5811 in the Department of Evolutionary Biology at the Max Planck Institute for Developmental Biology and can be provided to other researchers upon request.

Etymology: The species epithet, a Latin adjective denotes the formerly hidden nature of the species.

Relationships among the two new species and P. pacificus

As mentioned above, the two new species described herein and P. pacificus , P. exspectatus and P. arcanus form a species-complex. Basically, all five species are morphologically almost indistinguishable. P. pacificus is separated from all other species by its hermaphroditic mode of reproduction. P. taiwanensis could be separated from the four other species by its shape of the stenostomatous right subventral ridge. The other three species are also potentially separated from each other, e.g., the arrangement of v5-7 papillae and pd ( Kanzaki et al. 2012a). However, these characters are very small and still show some variability within each species. In addition, morphometric values show large intraspecific variation as already noted for other Pristionchus species before (e.g. Herrmann et al. 2006a; Kanzaki et al. 2012a b, 2013a b c; Kanzaki and Giblin-Davis 2015; Ragsdale et al. 2015; Susoy et al. 2015). Therefore, biological and molecular characters are necessary to separate species.

Figures

Fig. 4. Pristionchus occultus n. sp. Drawings are of live specimens (non-types) from temporary mounts. (A) Stenostomatous female, right lateral view. (B) Stenostomatous male, right lateral view. (C) Anterior end of stenostomatous male, right lateral view. (D) Stomatal region of stenostomatous female, right lateral view; below (from left to right) are dorsal tooth and right subventral denticle. (E) Stomatal region of stenostomatous female, left lateral view; below are left subventral ridge and dorsal tooth. (F) Stomatal region of stenostomatous female, ventral view; below are right subventral denticule, dorsal tooth and left subventral ridge. (G) Stomatal region of eurystomatous female, right lateral view; below are dorsal tooth and right subventral tooth. (H) Stomatal region of eurystomatous female, left lateral view; below are left subventral ridge and dorsal tooth. (I) Pharyngeal region of stenostomatous female, right lateral view. (J) Body surface showing longitudial striations and relative position of deirid and secretory pores.

Fig. 5. Pristionchus occultus n. sp., (A) Anterior gonad of female, right lateral view. (B) relative position of female postdeirid. (C) Female vulva, ventral view. (D) Female anal region, ventral view. (E) Female tail, left lateral view. (F) Male gonad, left lateral view. (G) Male tail region, ventral view. (H) Male phasmid and genital papillae v5-7 and pd, ventral view. (I) Male tail region, right lateral view. (J) Spicule and gubernaculum, right lateral view.

Fig. 2. Pristionchus taiwanensis n. sp. Drawings are of live specimens (non-types) from temporary mounts. (A) Stenostomatous male, left lateral view. (B) Stenostomatous female, right lateral view. (C) Anterior end of stenostomatous male, right lateral view. (D) Stomatal region of eurystomatous female, left lateral view; below (from left to right) are left subventral ridge and dorsal tooth. (E) Stomatal region of stenostomatous female, right lateral view: below are right subventral denticle and dorsal tooth. (F) Stomatal region of eurystomatous female, left lateral view; below are left subventral ridge and dorsal tooth. (G) Stomatal region of eurystomatous female, right lateral view; below are dorsal tooth and right subventraltooth. (H) Pharyngeal region of stenostomatous female, left lateral view. (I-J) Body surface showing longitudial striations and relative position of deirid and secretory pores.