Biodiversity of the Coccidia (Apicomplexa: Conoidasida) in vertebrates: what we know, what we do not know, and what needs to be done

Abstract

Over the last two decades my colleagues and I have assembled the literature on a good percentage of most of the coccidians (Conoidasida) known, to date, to parasitise: Amphibia, four major lineages of Reptilia (Amphisbaenia, Chelonia, Crocodylia, Serpentes), and seven major orders in the Mammalia (Carnivora, Chiroptera, Lagomorpha, Insectivora, Marsupialia, Primates, Scandentia). These vertebrates, combined, comprise about 15,225 species; only about 899 (5.8%) of them have been surveyed for coccidia and 1,946 apicomplexan valid species names or other forms are recorded in the literature. Based on these compilations and other factors, I extrapolated that there yet may be an additional 31,381 new apicomplexans still to be discovered in just these 12 vertebrate groups. Extending the concept to all of the other extant vertebrates on Earth; i.e. lizards (6,300 spp.), rodents plus 12 minor orders of mammals (3,180 spp.), birds (10,000 spp.), and fishes (33,000 spp.) and, conservatively assuming only two unique apicomplexan species per each vertebrate host species, I extrapolate and extend my prediction that we may eventually find 135,000 new apicomplexans that still need discovery and to be described in and from those vertebrates that have not yet been examined for them! Even doubling that number is a significant underestimation in my opinion.

Hyaloklossia Labbé, 1896 (Alveolata: Apicomplexa) in frogs: Description of a new species and proposing a new subfamily to accommodate these enigmatic parasites

“…As a case in point, there are ~8120 extant species of amphibians on Earth (Frost, 2020), but only 45 amphibian species (0.5%) have been examined for apicomplexans and from them, 52 apicomplexan species and 38 other forms ( species incertae sedis , species inquirendae , etc.) have been documented in the literature ( Duszynski et al, 2007 ; Duszynski, 2021 ). Unfortunately, this demonstrates that our knowledge of apicomplexan species richness is based on very limited, non-exhaustive sampling, which does not allow estimates for species richness at any scale.…”

“…Currently, it includes four subfamilies: Sarcocystinae Poche, 1913 ( Sarcocystis, Flenkelia ), Toxoplasmatinae Biocca, 1957 ( Toxoplasma, Hammondia, Heydornia, Neospora , Besnoitia ), Cystoisosporinae Frenkel et al, 1987 ( Cystoisospora ), and Eumonosporinae Chou et al, 2021 ( Eumonospora ), along with the genera Hyaloklossia and Nephroisospora ( Frenkel et al, 1979 ; Smith, 1981 ; Sercundes et al, 2016 ; Duszynski et al, 2018 ; Chou et al, 2020 ; Chou et al, 2021 ). Hyaloklossia is a monotypic genus that is clearly distinguishable from other genera of Sarcocystidae based on its homoxenous (direct) life cycle, gametogony and sporogony in frog renal tissues, and unusual oocyst morphology ( Modrý et al, 2001 ; Duszynski et al, 2007 ; Duszynski, 2021 ). Based on these observations, Hyaloklossia is an independent lineage from other members of the Sarcocystidae ( Modrý et al, 2001 ; Šlapeta et al, 2003 ).…”

Non-Invasive Wildlife Disease Surveillance Using Real Time PCR Assays: The Case of the Endangered Galemys pyrenaicus Populations from the Central System Mountains (Extremadura, Spain)

“…Although Eimeria species were described morphologically from insectivorous mammals [ 51 ], molecular data are scarce. Cross-infection studies have shown that coccidia from one host family generally do not infect hosts from other families or orders, although some coccidia are less host specific [ 51 , 52 , 53 ]. Therefore, considering the high prevalence of Eimeria in our study, we plan on untangling the true diversity of Eimeria spp.…”

Black-spotted pond frog Pelophylax nigromaculatus as a new host for the renal coccidian genus Hyaloklossia (Alveolata: Apicomplexa)

“…For over 120 years, the genus was considered monotypic: containing only a single species, H. lieberkuehni ( Labbé, 1894 ), reported from Pelophylax spp. (Anura: Ranidae) in Europe ( Modrý et al, 2001 ; Duszynski et al, 2007 ; Duszynski, 2021 ). Recently, a second species, Hyaloklossia kasumiensis Tokiwa, Chou, Tochigi, Katayama et Duszynski, 2021 , was described from Japan in East Asia ( Tokiwa et al, 2021 ).…”