Morphology and phylogeny of the parasitic nematode Mooleptus rabuka (Machida, Ogawa & Okiyama, 1982) (Rhabditida, Spirurina: Mooleptinae nom. nov.), with notes on taxonomy of the family Gnathostomatidae

Abstract

The nematode Mooleptus rabuka is recorded in the digestive tract of catshark Apristurus fedorovi caught at the Imperial Ridge (Pacific Ocean). Important morphological features such as the number of cephalic and caudal papillae, the position of amphids and the shape of the gubernaculum are detailed in this parasite species. According to the phylogenetic analyses based on the 18S ribosomal RNA gene sequences, M. rabuka forms a lineage, Mooleptinae nom. nov., which is close to the gnathostomatid genus Echinocephalus (maximum likelihood analysis), or else forms a polytomy with this genus and the lineages of Anguillicola + Spiroxys and Tanqua + ‘Linstowinema’ sp. (Bayesian inference analysis). Overall, our findings do not support the monophyly of the Gnathostomatidae. We elevate spiroxyines to the family status, Spiroxyidae stat. nov., and temporarily consider the Gnathostomatidae to include the following subfamilies: Ancyracanthinae Yorke & Maplestone, 1926, Gnathostomatinae Railliet, 1895 sensu lato and Mooleptinae nom. nov. The name Mooleptinae nom. nov. is suggested instead of the Metaleptinae Moravec & Nagasawa, 2000, which is based on a preoccupied generic name Metaleptus Machida, Ogawa & Okiyama, 1982.

Review of the parasitic nematodes of marine fishes from off the American continent

“…Such submissions limit checks on the accuracy of taxonomic identifications, and some likely misidentifications have been noted by some authors (see Černotíková et al ., 2011; Ailán-Choke et al ., 2019, 2020). However, despite the limited and sometimes inaccurate data, the genetic characterization of nematodes reported herein has been crucial for supporting species validity and the evaluation of their phylogenetic positions (Mejía-Madrid and Aguirre-Macedo, 2011 a , 2011 b ; Sardella et al ., 2017; Aguilar-Aguilar et al ., 2019; Sokolov and Gordeev, 2021), genetic variability (Li et al ., 2014), broad phylogenetic studies of higher taxa (Nadler and Hudspeth, 1998, 2000; Nadler et al ., 2007; Li et al ., 2018; Barton et al ., 2022), specific identification of larval forms (Palesse et al ., 2011; Haarder et al ., 2013; Roca-Geronès et al ., 2018) and even the elucidation of life cycles (May-Tec et al ., 2018). It should be mentioned that some of these works were not specifically carried out in marine waters off the American continent (Nadler and Hudspeth, 1998, 2000; Nadler et al ., 2007; Haarder et al ., 2013; Li et al ., 2014, 2018; Roca-Geronès et al ., 2018), but included nematode species that have been reported in this region.…”