Pristionchus undetermined

Ragsdale, Erik J., Kanzaki, Natsumi, Röseler, Waltraud, Herrmann, Matthias & Sommer, Ralf J., 2013, Three new species of Pristionchus (Nematoda: Diplogastridae) show morphological divergence through evolutionary intermediates of a novel feeding-structure polymorphism, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 168 (4), pp. 671-698 : 690-692

PRISTIONCHUS FUKUSHIMAE SP. NOV.

Description

Measurements: See Table 3.

Adults: Species gonochoristic (i.e. dioecious), with males and females.

Stenostomatous form: Metastegostom bearing: right subventral ridge of variable shape and armature, having a conspicuous triangular denticle, being rounded, or with two or three rounded to pointed denticles ( Fig. 10B–D ); two or three blunt or weakly pointed left subventral denticles apparently projecting from a common cuticular plate ( Fig. 10A ).

Eurystomatous form: Cheilostom divided into six distinct per- and interradial plates, some plates incompletely split into two longitudinal strips, for half to two-thirds length of plate, division of plate often asymmetrical, incisions between strips sometimes

All measurements are in Mm, and are presented as mean ± SD (range).

difficult to observe by LM ( Fig. 4 L), resulting in between six and 12 strips in total ( Figs 4J, L, 10E, F ). Anterior end of each strip rounded and elongated to stick out from stomatal opening and form a small flap ( Fig. 10E, G ), i.e. constituting between six and 12 flaps in total, although plates that are not split sometimes end in two flaps. Metastegostom bearing: a large and strongly sclerotized claw-like dorsal tooth ( Figs 4K, 10E, F ); a large, claw-like or pointed right subventral tooth ( Fig. 10F ); in the left subventral sector, a ridge of large denticles of varying shape, size, and number, i.e. between six and eight, arising from a split cuticular plate, sometimes with one or two adventitious denticles ( Fig. 10E ).

Male: Oval manubrium at anterior end of spicule ( Fig. 11G ). Gubernaculum conspicuous, about 40% spicule length, narrow anteriorly such that dorsal wall is recurved, and that dorsal and ventral walls separate at a <15° angle at posterior end ( Fig. 11G ). In lateral view, anterior half of gubernaculum with two serial curves separated by anteriorly directed process, and with a short, shallow, concave terminal curvature less than one fourth of gubernaculum length, and with a proximal curvature about half of gubernaculum length; posterior half forming a tubelike process enveloping spicules ( Fig. 11G ). Nine pairs of genital papillae and a pair of phasmids present and arranged as <P1 (P2d, P3, C), P4, P5d, Ph, (P6, P7, P8), P9d> [= <v1 (v2d, v3, C), v4, ad, Ph (5, v6, v7), pd> in the nomenclature of Sudhaus & Fürst von Lieven, 2003] ( Fig. 11E, F ). Positions of P1 papillae located one cloacal body diameter posterior to cloacal slit, P2d at same level or slightly anterior to P3, P2d and P3 closer to P4 than to P1, or P2 equidistant between P1 and P4, P4 one-half of cloacal body diameter posterior to C, and equidistant between P2d and P5d, P5d equidistant between P4 and P6, Ph clearly anterior to P6 and equidistant between P5d and P6, P6–P8 linearly arranged, and P9d slightly posterior to or overlapping P7–P8 ( Fig. 11E, F ).

Differential diagnosis: Pristionchus fukushimae sp. nov. is diagnosed from all other species of Pristionchus and Diplogastridae , except P. hoplostomus sp. nov., a eurystomatous form with cheilostomatal plates variably and incompletely split versus being completely divided into six or 12 plates. It is further distinguished from all other species of Pristionchus except P. triformis sp. nov. and P. hoplostomus sp. nov. by an anteriorly serrated versus smooth stegostomatal ring in the eurystomatous form, and by a finely serrated versus smooth anterior gymnostomatal ring of the eurystomatous form. It is distinguished from all other Pristionchus species except P. triformis sp. nov. and P. hoplostomus sp. nov. by a serrated versus smooth anterior gymnostomatal ring in the eurystomatous form. It is further distinguished from P. hoplostomus sp. nov. by the absence versus presence of a distinct, additional left subventral plate with multiple denticles. Pristionchus fukushimae sp. nov. is separated from P. hoplostomus sp. nov. by reproductive isolation, namely the inability to produce viable hybrid F 1 offspring. It is further distinguished from P. hoplostomus sp. nov. by: male papilla P4 being closer to P2d than to P5d versus equidistant between P2d and P5d; the anterior curvature of gubernaculum being deeply concave versus shallow; the proximal curvature of gubernaculum being one-half versus one-third of gubernaculum length. It is tentatively also distinguished from P. triformis sp. nov. by P2d slightly anterior to or overlapping versus clearly overlapping P3, and by P5d being closer to Ph than to P4 versus equidistant between P4 and Ph. Pristionchus fukushimae sp. nov. is distinguished from all other species by its unique SSU rRNA sequence, an 830-bp fragment of which differs from the phylogenetically close species P. triformis sp. nov. and P. hoplostomus sp. nov. by ten and five nucleotides, respectively. Finally, P. fukushimae sp. nov. is distinguished from P. triformis sp. nov. by a gonochoristic versus hermaphroditic mode of reproduction.

Type host (carrier) and locality: The culture from which the type specimens were obtained was originally isolated from the body of an adult Lucanus maculifemoratus collected by N. Kanzaki and M. Herrmann in a forest in Tadami, Fukushima Prefecture, Japan, in June 2012 .

Type material and strain: Holotype stenostomatous male, two paratype stenostomatous males, and three paratype six-plated eurystomatous females are deposited in the UCRNC, CA, USA. Two paratypes each of stenostomatous males and eurystomatous females are deposited in the Swedish Natural History Museum , Stockholm, Sweden. Two paratypes each of stenostomatous males and eurystomatous females are deposited in the Natural History Museum , Karlsruhe, Germany. The type strain is available under culture code RS5595.

Etymology: The species epithet is the Latin genitive of the feminized place-name ‘Fukushima’, and refers to the type locality of the species.

Figures

Figure 10. Stomatal region of adult females of Pristionchus fukushimae sp. nov. A, stenostomatous form, left lateral view, showing two variants of left subventral ridge (below, left) and one variant of dorsal tooth (below, right). B, stenostomatous form, right lateral view, showing dorsal tooth (below, left) and right subventral denticle (below, right). C, D, variants of stenostomatous form, right lateral view, showing dorsal tooth (below, left) and right subventral ridge (below, right). E, eurystomatous form, left lateral view, showing variant of left subventral denticles (below, left) and dorsal tooth (below, right). F, eurystomatous form, right lateral view, showing dorsal tooth (below, left) and right subventral tooth (below, right). G, detail of individual cheilostomatal plate dissected from body of eurystomatous form, showing inner view (top, left), view through section (top, right), and ventral view (below).

Figure 11. Adults of Pristionchus fukushimae sp. nov. A–D, female; E–G, male. A, anterior gonad branch, left lateral view. B, vulva, ventral view. C, anus, ventral view. D, tail region, left lateral view. E, tail region, left lateral view. F, tail region, ventral view. G, gubernaculum and spicule, right lateral view.