Parapalus, Loof and Zullini, 2000

Peña-Santiago, Reyes, Liébanas, Gracia & Ahmad, Wasim, 2014, Taxonomy of the genus Oriverutus Siddiqi, 1971 (Nematoda: Dorylaimida: Nordiidae), Journal of Natural History 48 (21), pp. 1253-1278 : 1266

Parapalus

When proposing this genus, with Parapalus arboricola from Costa Rica as its only and type species, Loof and Zullini (2000) classified it under Qudsianematidae , Paraxonchiinae due to its neck strongly tapering forwards, the lip region becoming (p. 609) “less than 25% of body diam. at base of pharynx”. Parapalus was not compared with Oriverutus and its closest genera. The taxonomy of paraxonchiid taxa suffered some changes during the next decade (cf. Baniyamuddin et al. 2010), but the concept and status of Parapalus remained invariable. The re-examination of type material of Parapalus arboricola has revealed ( Figure 10 ) that the general morphology of this taxon resembles in many aspects to that of Oriverutus (lip region visible expanded, odontostyle longer than lip region, conical tail with a weak dorsal concavity), but also confirmed that the neck region strongly tapers towards the anterior end, with very narrow lip region ( Figure 10A–C ), a remarkable feature indeed. Besides, lips are separated but probably not lobelike ( Figure 10D–F ), odontostyle is relatively robust, and the pharyngo-intestinal junction lacks gland cells but the cardia is distinctly asymmetrical ( Figure 10G ), all these features being unusual but not unknown in Oriverutus species. Parapalus arboricola might represent an extreme case within the potential variability of the genus Oriverutus , but, taking into account that the strong tapering of the neck region is a relevant qualitative apomorphic state, not described in Oriverutus , Parapalus is accepted as a valid genus, provisionally distinguishable from Oriverutus .

Figures

Figure 10. Parapalus arboricola Loof and Zullini, 2000 (light microscopy). (A–C) Neck region of female, male and J4, respectively; (D) J4, anterior region in median, lateral view; (E) Male, anterior region in median, lateral view; (F) Male, lip region and amphid fovea in submedian, lateral view; (H) Vagina; (I) Male, spicules and caudal region. Scale bars: A–C = 100 µm; D–F, H = 5 µm; G = 10 µm; I = 20 µm.