Description of Schistonchus microcarpus n. sp. (Nematoda: Aphelenchoididae), an associate of Ficus microcarpa in China

Abstract

Schistonchus microcarpus n. sp. was recovered from the syconia of Ficus microcarpa from Shenzhen and Guangzhou, Guangdong Province, China, during a survey of nematode biodiversity from 2007 to 2009. It is characterised by possessing the combined characters of a short post-uterine sac (PUS) (3-11 μm or <0.4 vulval body diam. (VBD) long), excretory pore located just posterior to the head but anterior to the conus level of the stylet, prominent amphids, three pairs of subventral papillae on the male tail (one pair adcloacal, one pair halfway between cloaca and tail terminus, and one pair near tail tip), unique recurved and sickleshaped spicules with finely rounded tip with cucullus, amoeboid sperm, and rounded male tail tip with or without mucron. Schistonchus microcarpus n. sp. is morphologically differentiated from all other described species in this genus by the possession of a spicule with a cucullus on the tip. Schistonchus microcarpus n. sp. was easily differentiated from other sequenced species by the partial small subunit rRNA gene (SSU) and D3 expansion segments of the large subunit rRNA gene (LSU). Phylogenetic analysis with partial SSU sequences suggests that S. microcarpus n. sp. is in a highly supported monophyletic clade with sequenced Schistonchus species except for S. hirtus. Based upon inferences using D3 LSU sequence data, it forms a clade with an undescribed species of Schistonchus ex F. benjamini from Australia and is part of a larger clade of Schistonchus that mostly share the character of an anteriorly placed excretory pore. Sequences of partial mtDNA COI (590 bp) from males of S. microcarpus n. sp. with and without a mucronate tail tip were identical, proving that these two morphotypes are conspecific.

Description of Schistonchus superbus n. sp. (Nematoda: Aphelenchoididae), an associate of Ficus superba in China

“…In S. microcarpus, male tail tips have two morphotypes, with or without a mucron. Molecular analysis showed that male tail dimorphism reflects intraspecies variation within S. microcarpus (Zeng et al, 2011). A similar result was also observed in S. ben-…”

Are nematodes costly to fig tree–fig wasp mutualists?

“…However, Parasitodiplogaster species have been reported to develop inside wasps and use the syconia as repositories for the dauer (dispersal stage of nematodes) juveniles (Poinar & Herre, 1991;Herre, 1996;Van Goor et al, 2018), meaning that their presence can influence the longevity of pollinating wasp, host location, and pollination efficiency, and indirectly seed production in fig trees. The biology and impact of nematodes on the fig-fig wasp mutualism remains under studied, with most studies focusing on the taxonomy, diversity, and phylogeny of nematodes (Zeng et al, 2011;Davies et al, 2015;Susoy et al, 2016;Sun et al, 2017). Figs, fig wasps, and their parasitic nematodes provide a comparative system for assessing the influence of third parties on mutualism persistence and the cost of parasitism Dunn et al, 2008a;Van Goor et al, 2018;Wang et al, 2019b).…”

“…A locally abundant monoecious Ficus species (Ficus microcarpa L.f.) and a similarly available gynodioecious species (Ficus hispida L.f.) were selected to investigate the prevalence and abundance of nematodes. Both species are native to Southwest China, F. microcarpa is pollinated by the fig wasp Eupristina verticillata Waterston (Kong et al, 2016), and the plant-parasitic nematode Ficophagus microcarpus (Zeng et al) has been found in the figs of this species (Zeng et al, 2011;Davies et al, 2015). Ficus hispida is pollinated by Ceratosolen solmsi marchali Mayr in Xishuangbanna (Peng et al, 2005).…”

Two levels of host-specificity in a fig-associatedCaenorhabditis

“…No figs aside from F. septica were contained C. sp. 34 nematodes (Table 2), despite some of these species being known to harbor multiple nematode groups [54,55]. Thus, this particular fig-associated C. sp.…”