Koerneria sudhausi n. sp. (Nematoda: Diplogastridae); a hermaphroditic diplogastrid with an egg shell formed by zygote and uterine components

Abstract

A new hermaphroditic species belonging to the diplogastrid taxon Koerneria is described. Although Koerneria sudhausi n. sp. displays all known apomorphies of Koerneria, it shares apomorphic characters with Mononchoides colobocercus (originally described as Diplenteron colobocercus). I assume that the apomorphic features of Koerneria exist in M. colobocercus too and were overlooked in the original description. Consequently M. colobocercus is transferred from Mononchoides to Koerneria, becoming Koerneria colobocerca n. comb. Koerneria sudhausi n. sp. and its sister species, K. colobocerca, together form the Diplenteron species group within Koerneria. Characteristic features of K. sudhausi n. sp. are the species group-specific prerectum in combination with a short but pointed tail in both sexes. In K. sudhausi n. sp. a stoma dimorphism between stenostomatous and eurystomatous morphs occurs. Eurystomatous K. sudhausi n. sp. hermaphrodites lack two denticles in the armature of the left subventral stegostomatal sector. All adults possess pore-like amphids. Although K. sudhausi n. sp. is hermaphroditic, a considerable frequency of males (up to 16.6%) occurs. In cultures of K. sudhausi n. sp. males are functional. In K. sudhausi n. sp. males, the phasmid is situated between caudal papillae v6 and v7. The formation of a secondary egg shell by a uterine shell gland is described. Koerneria sudhausi n. sp. possesses an exceptionally high number of intestine cells, an inexplicable dimorphism in egg length, and a dauer juvenile that lacks the oily substance usually found in diplogastrid dauers.

Laboratory studies on the biocontrol potential of the predatory nematode Koerneria sudhausi (Nematoda: Diplogastridae)

“…In the present study, asexual reproduction (hermaphroditism) of K. sudhausi was observed; however, sexual reproduction (amphimixis) of the nematode was also reported (Fürst von Lieven, 2008), although coupling behaviour was not observed in our study. The generation time of K. sudhausi feeding on bacteria at 25 • C was 8 days.…”

“…However, a hermaphrodite can produce more progeny if she mates with a male even after her spermatozoa have been exhausted (Fürst von Lieven, 2008). An oviposition rate of 8-10 eggs/day per female was reported in Mononchoides cultured on E. coli at 30 • C .…”

“…Another advantage of K. sudhausi is the existence of dauer juveniles (Fürst von Lieven, 2008), which are tolerant to adverse environmental conditions. This is the first report in which predatory nematodes propagated on bacteria were used to control plant-parasitic nematodes in soil.…”

“…We have isolated a species of diplogastrid predatory nematode from tomato roots infected with the root-knot nematode M. javanica and this has been described as Koerneria sudhausi, which is most closely related to D. colobocercus (= K. colobocercus) (Fürst von Lieven, 2008). In the present study, we examine the potential of this predatory nematode as a biological control agent against plant-parasitic nematodes.…”

Parasitodiplogaster species associated with Pharmacosycea figs in Panama

“…The common characters of the genus are: i) posteriorly-located phasmids; and ii) relatively short (not filiform) female tail, characters which overlap with several Koerneria species and Teratodiplogaster Kanzaki, Giblin-Davis, Davies, Ye, Cen ter & Thomas, 2009(Giblin-Davis et al, 2006Fiirst von Lieven, 2008;Kanzaki et al, 2009Kanzaki et al, , 2012. …”