Anilocra grandmaae Aneesh, Hadfield, Smit and Kumar, 2021

Kumar, Panakkool Thamban Aneesh Helna Ameri Kottarathil Appukuttannair Biju, 2022, Simultaneous double parasitism by the parasitic cymothoids (Crustacea: Isopoda) of two genera on a single host fish Tenualosa toli from India, Nauplius (e 2022013) 30, pp. 1-8 : 5-6

Anilocra grandmaae Aneesh, Hadfield, Smit and Kumar, 2021

( Fig. 1 D )

Anilocra grandmaae Aneesh, Hadfield, Smit and Kumar, 2021: 321–328 , figs. 1 – 6.

Anilocra leptosoma [not Anilocra leptosoma Bleeker, 1857 ] —Aneesh et al., 2017: 443 – 450, figs. 1 – 4. — Amrutha et al., 2021: 95, fig. 1.

Host. Tenualosa toli and Nematalosa nasus ( Clupeidae ) ( Aneesh et al., 2019; 2021; Amrutha et al., 2021; present study).

Distribution. Kerala coast;southwest coast of India; the Bay of Bengal and Malabar coast of Kerala, India ( Aneesh et al., 2021; present study).

Remarks. The body surface attaching cymothoid An. grandmaae is recently described by Aneesh et al. (2021) based on morphological and molecular characterization.This species was originally identified as An. leptosoma by Aneesh et al. (2019) and the reexamination of the materials suggested that it may not be the original An. leptosoma of Bleeker and therefore was erected as a new species. Anilocra grandmaae , can be identified by: body less than 4.0 times as long as wide; antennula article 3 anterodistal margin expanded, 1.2–1.4 times as wide as long; pleonite 1 visible but largely concealed by pereonite 7, lateral margin posteriorly produced; pereopods 1–4 with three prominent nodules on dactylus; endopod of pleopods 3–5 with proximomedial lobe and endopod of pleopods 3–5 with multiple folds; pleotelson ovate, lateral margins converging smoothly to a caudomedial point ( Aneesh et al., 2021).

Eventhoughthesimultaneousco-occurrenceof2–5 different species of parasitic crustaceans are reported from different regions, including India, the studies on co-occurrence involving two different cymothoids were very scarce ( Daniel and Premkumar, 1967; Benz et al., 2003; Rajkumar et al., 2006; Gopalakrishnan et al., 2010; Aneesh et al., 2013; 2014; Welicky and Smit, 2018). Before this study, only two valid reports are available: a recent report by Welicky and Smit (2018) from South Africa and another from the Caribbean by Williams and Bunkley-Williams (1985).

Previously reported simultaneous multiple co-infestations involved one cymothoid isopod or cirriped and a copepod, or a maximum of four copepods or 2–5 copepods from different genera ( Aneesh et al., 2014). Interestingly, the species involved in the double, triple, or quadruple parasitism exhibit site and niche specific parasitism to avoid interspecific competition ( Aneesh et al., 2014). Similar observations were noted in the case of cymothoid co-infestations, which included one body surface and a branchial infesting species, or body surface and a buccal infesting species ( Welicky and Smit, 2018). Similarly, the two cymothoids involved in the present study also exhibit the site and niche specific parasitization with An. grandmaae attached to the body surface and Ag. malayi settled on either side of the gill chamber ( Fig. 1A ).

Parasitic cymothoids exhibit a different level of oligoxenous host specificity ( Smit et al., 2014; Aneesh et al., 2019). Most species are restricted to one, or a limited number of hosts ( Smit et al., 2014; Aneesh et al., 2019). The toli shad, T. toli is the type host for An. grandmaae and An. malayi is also reported from the same host ( Aneesh et al., 2018; 2021). The prevalence of both species confirms their specificity towards T. toli . The infestation prevalence of Ag. malayi and An. grandmaae being 13.88 % (113 out of 814) and 8.72 % (71 out of 814), respectively. The prevalence of a simultaneous co-infestation is only 1.1 % (nine out of 814).

The mechanism and the reason for simultaneous co-infestation by two cymothoid genera are still unknown. Out of the seven different localities, the simultaneous co-infestation was recorded only from three nearby localities (Azhikkal, Ayyikkara, and Ponnani) along the Malabar coast, suggesting that environmental factors may have some influence on triggering the co-occurrence. Detailed studies are needed to find out the triggering mechanisms. A better understanding of the role of environmental factors and mechanisms of host-parasite interaction among cymothoids and their hosts involved in co-infestation is warranted.

Figures

Figure 1. A, Co-infestation of external attaching Anilocra grandmaae [arrow Ag (f)] and branchial attaching Agarna malayi [arrow Am (f)] infesting an individual Tenualosa toli. B, C, Ovigerous female and male of Ag. malayi, respectively. D, Ovigerous female of An. grandmaae.