Unionicola (Myanmaratax) savadiensis Chapurina, Vidrine, Kondakov, Vikhrev & Bolotov, 2022

ChatterjeeK, Tapas, KhanK, Ajaz Ali Ahmed, SinghK, Ravail, VidrineK, Malcolm, ZawalK, Andrzej & PešićK, Vladimir, 2023, First record of Unionicola (Myanmaratax) savadiensis from India, with remarks on parasite-host relationship in unionicolid mites (Acari, Unionicolidae), Acarologia 63 (4), pp. 1094-1101 : 1097-1100

Unionicola (Myanmaratax) savadiensis Chapurina, Vidrine, Kondakov, Vikhrev & Bolotov, 2022

Figure 3A-D

Material examined — Jammu and Kashmir: CC Vial 1, Gou Manhasan, a tributary of River Chenab, 32.7232°N, 74.7334 °E, from the gills of C. cashmiriensis , 2♀ ; CC Vial 2,

Locality Coordinates Host Voucher Code BOLD /GenBank id % Match Match Process id Match Species

Gou Manhasan 32.7232° N, 74.7334° E Corbicula cashmiriensis CCDB-44301-A04 HYDAL 004-23 99.65 GBMNF 57322-22 Lamellidens corrianus Gou Manhasan 32.7232° N, 74.7334° E Corbicula cashmiriensis CCDB-44301-A05 HYDAL 005-23 99.67 GBMNF 57322-22 Lamellidens corrianus Gou Manhasan 32.7232° N, 74.7334° E Lamellidens marginalis CCDB-44301- A07 HYDAL 007-23/ OQ801389 99.54 GBMND 37031- 21 Unionicola savadiensis Gajansoo Marh 32.7651° N, 74.7150° E Lamellidens marginalis CCDB-44301- A08 HYDAL 008- 23 99.67 GBMNF 57322-22 Lamellidens corrianus Gajansoo Marh 32.7651° N, 74.7150° E Lamellidens marginalis CCDB-44301- A10 HYDAL 010-23/ OQ801388 99.53 GBMND 37031- 21 Unionicola savadiensis Gou Manhasan 32.7232° N, 74.7334° E Lamellidens corrianus CCDB-44301- B02 HYDAL 014-23/ OQ801387 99.54 GBMND 37031- 21 Unionicola savadiensis ibid., from the gills of C. cashmiriensis , 1♂, dissected and slide mounted ( RMNH); CC Vial

3, ibid., from the gills of C. cashmiriensis , 2♀ ; LMM Vial 1, Gou Manhasan, a tributary of River Chenab, 32.7232°N, 74.7334°E, from the gills of L. marginalis , 2 ♂ (1 ♂ sequenced, Tab. 1); LMM Vial 2, Gajansoo Marh, a tributary of River Chenab, 32.7651°N, 74.7150°E, from the gills of L. marginalis , 4 ♂, 1♀ (1 ♂ sequenced, Tab. 1), 1 ♂ dissected and slide mounted ( RMNH); LCM Vial 1: Gajansoo Marh, a tributary of River Chenab, 32.7651°N, 74.7150°E, from the gills of L. corrianus , 1♂, 3♀ ; LCM Vial 2, Gou Manhasan, a tributary of River Chenab, 32.7232°N, 74.7334°E, from the gills of L. corrianus , 2♂, 2♀ (1♀ sequenced, Tab. 1).

Remarks — Unionicola (M.) savadiensis was originally described from the Indaw Lake in Myanmar. The holotype was collected from the gills of the freshwater mussel, L. savadiensis (Nevill, 1877) , and the paratypes from the gills of the type host species and of L. generosus (Gould, 1847) . Chapurina et al. (2022a) assigned U. savadiensis to the newly described subgenus Myanmaratax Chapurina et al. 2022 , which, in addition to U. (M.) savadiensis , includes three more mussel-associated gill mites, i.e., U. (M.) brandti Vidrine, 1985 , U. (M.) generosa , and U. (M.) trapezidens Chapurina, Vidrine, Kondakov, Vikhrev & Bolotov, 2022 . Members of this subgenus use freshwater mussel ( Bivalvia: Unionidae ) species of the genera Lamellidens and Trapezidens in Western Indochina as well as Contradens and Ensidens in the Sundal and Subregion ( Chapurina et al. 2022a) as the primary hosts.

The collected specimens from Jammu and Kashmir match the original description U of. (M.) savadiensis in regard to shapes of coxal plates and genital fields (Fig. 3A, C), palps (Fig. 3B) and terminal segments of the fourth legs (Fig. 3D).

and Egypt (Abdel-Garber et al. 2018)—these were apparently compromised as mussels, including Corbicula and infected unionoid mussels, were held in the same container for transport and probably resulted in vagrancy among these mites. Vagrancy is common when mussels of different species hosting different mites are held together under stress ( Edwards and Vidrine 2013a). We suspect that this also accounts for our current observation in India. We showed that all DNA sequences of mussels, which were amplified instead of mite DNA, belong to L. corrianus , also from Gou Manhasan (where C. cashmiriensis is listed as a “host”) and from the Gajansoo Marh (where L. marginalis is listed as a “host”). Therefore, we can speculate that the members of U. savadiensis in all three localities parasitize L. corrianus , but occasionally can occur also on two other species (without feeding on them), and their presence on the latter species should be treated as vagrant associations. This is confirmed by the observation that mites were found on the surface of gill in L. marginalis and C. cashmiriensis , while mites were found in deeper layers of the gill in L. corrianus .

Secondly, in addition to discussion of coevolution, the adaptations to new hosts, i.e. ‘host-switching’ ( Cichy et al. 2016), must be taken into account. Such a situation may occur in the case of Unionicola ypsilophora (Bonz, 1783) , which inhabits invasive Sinanodonta woodiana (Lea, 1834) in Poland ( Cichy et al. 2016). Unlike ‘vagrancy’ — where mites move from one species of mussel to another species, ‘host-switching’ (also known as ‘Association by Colonization’ in studies of coevolution and cophylogeny) is an uncommon phenomenon, at least in the literature. However, some mite interactions can only be explained by incidences of ‘host-switching,’ with the best examples being the occurrences of unionicolid mites in freshwater snails. These snail mites are apparently derived from mussel mites, and this is evident in the morphological and molecular studies by Wu et al. (2009, 2012) in Chinese mussel and snail mites (see also Edwards and Vidrine 2013a). In this study, we do not suggest that ‘host-switching’ has or may be occurring among our Indian findings, but we do want to note that it was considered.