Novel techniques for biodiversity studies of gordiids and description of a new species of Chordodes (Gordiida, Nematomorpha) from Kenya, Africa

Abstract

We review recent advances in the use of non-adult gordiid cyst stages to locate gordiids over large geographical regions and new culturing techniques which can help overcome current difficulties in nematomorph biodiversity studies. Using these techniques, we collected a new species of gordiid as cysts in aquatic snails (Biomphalaria pfeifferi) from the Lake Victoria Basin, western Kenya, Africa and cultured them in the laboratory. We describe the adult free-living male and female worms using morphological (light and scanning electron microscopy) and molecular data as well as the life cycle, mating and oviposition behavior, egg strings, eggs, larvae, and cysts of this new species. Chordodes kenyaensis n. sp. belongs to a large group of African Chordodes in which simple areoles are smooth or superficially structured less so than "blackberry" areoles but contain filamentous projections. Present among the simple areoles are clusters of bulging areoles, crowned and circumcluster areoles along with thorn and tubercle areoles. In the laboratory, worms developed and emerged within 53-78 days from three species of laboratory-reared crickets exposed to cysts of this species. Adult male and female C. kenyaensis n. sp. initiated typical Gordian knots within hours to days of being placed together and males deposited masses of sperm on the cloacal region of females. Females began oviposition within a week of copulating and attached egg strings in a continuous zigzag pattern on small branches or air-hoses but never free in the water column. Larvae hatched within two to three weeks, and cysts developed in laboratory-reared and exposed snails within 14-24 days. Morphological characteristics of egg strings, eggs, larvae and cysts of C. kenyaensis were most similar to other gordiids in the genus Chordodes but differed morphologically from other gordiid genera for which similar information is available.

Comparative descriptions of non-adult stages of four genera of Gordiids (Phylum: Nematomorpha)

“…robustus #2 (NA), Gordius difficilis Montgomery, 1898 (NA), Neochordodes occidentalis Montgomery, 1898 (NA), Paragordius varius Leidy, 1851 (NA), and Paragordius obamai Hanelt, Bolek & Schmidt-Rhaesa, 2012 (AF). Additionally, data sets on oviposition behavior and non-adult characteristics for two additional species of hairworms including Chordodes janovyi Bolek, Schmidt-Rhaesa, Hanelt, & Richardson, 2010 (AF) and Chordodes kenyaensis Bolek, Szmygiel, Kubat, SchmidtRhaesa & Hanelt, 2013 (AF) were taken from previous publications (Bolek et al 2010;Bolek et al 2013a) and/or new material from laboratory infections (see below). We also provide new light microscopy (LM), differential interference contrast microscopy (DIC) and/or scanning electron microscopy (SEM) images for egg strings, larvae and/or cysts for these species.…”

“…At the end of their parasitic phase, gordiids manipulate the behavior of their terrestrial arthropod hosts to enter aquatic environments where adult worms emerge at the expense of the host committing suicide (Thomas et al 2002;. After emerging from their host, dioecious species form Gordian knots, mate, and females deposit egg strings as free-living forms; but females of parthenogenetic species deposit egg strings (Hanelt et al 2012;Bolek et al 2013a). Females produce up to eight million eggs during their short (2 weeks-2 months) free-living phase (Bolek & Coggins 2002;Hanelt 2009).…”

“…In contrast, cysts of gordiids were found in aquatic snails in 70% of the streams sampled from Nebraska and Oklahoma. These studies suggested that cysts are the most commonly encountered gordiid stages in nature and may be useful for sampling large geographical areas for nematomorph biodiversity studies (Hanelt et al 2001;Hanelt et al 2012;Szmygiel 2012;Bolek et al 2013a).…”

“…The lack of descriptions of non-adult stages of gordiids stems from the fact that until recently, the life-cycles for most species of gordiids were unknown. However, recent advances in our understanding of gordiid life-cycles in combination with new culturing and domestication techniques have made these life stages more accessible for morphological studies (Hanelt & Janovy 1999;2004a;2004b;Bolek & Coggins 2002;Hanelt et al 2012;Bolek et al 2010;2013a;2013b). Currently, a single comparative study exists on cyst morphology for three species of hairworms (Hanelt & Janovy 2002).…”

“…Currently, a single comparative study exists on cyst morphology for three species of hairworms (Hanelt & Janovy 2002). Using this information, Hanelt et al (2012) and Bolek et al (2013a) collected snails infected with two types of gordiid cysts from Kenya, a country for which no gordiid records existed. After exposing the appropriate group of laboratory-reared arthropods to the cysts, two new species of gordiids were discovered.…”