Ultrastructural Comparison of Hepatozoon ixoxo and Hepatozoon theileri (Adeleorina: Hepatozoidae), Parasitising South African Anurans

Abstract

To date, only two haemogregarine parasite species have been described from South African anurans: Hepatozoon ixoxo, infecting toads of the genus Sclerophrys (syn. Amietophrynus); and Hepatozoon theileri, parasitising the common river frog, Amietia quecketti. Both species have been characterised using limited morphology, and molecular data from PCR amplified fragments of the 18S rRNA gene. However, no ultrastructural work has been performed thus far. The aim of this study was to add descriptive information on the two species by studying their ultrastructural morphology. Mature gamont stages, common in the peripheral blood of infected frogs, were examined by transmission electron microscopy. Results indicate that H. ixoxo and H. theileri share typical apicomplexan characteristics, but differ markedly in their external cellular structure. Hepatozoon ixoxo is an encapsulated parasite presenting a prominent cap at the truncate pole, and shows no visible modifications to the host cell membrane. In comparison, H. theileri does not present a capsule or cap, and produces marked morphological changes to its host cell. Scanning electron microscopy was performed to further examine the cytopathological effects of H. theileri, and results revealed small, knob-like protrusions on the erythrocyte surface, as well as notable distortion of the overall shape of the host cell.

Diversity ofKaryolysusandSchellackiafrom the Iberian lizardLacerta schreiberiwith sequence data from engorged ticks

“…However, morphological changes of host cells analogous to those induced by Karyolysus have been reported in Hepatozoon theileri (Laveran, 1905) from frog hosts that are grouped within the Hepatozoon clade (Fig. 2) (Netherlands et al ., 2014; Conradie et al ., 2017). Hepatozoon curvirostris (Billet, 1904) from the lacertid host Timon pater (Lataste, 1880) also causes karyolysis, but an early study of this by Billet (1904) naturally lacks molecular data.…”

“…Additionally, the hypertrophy of the host cell observed with light microscopy may look different under electron microscopy. While for Hepatozoon ixoxo Netherlands et al ., 2014, hypertrophy was confirmed, H. theileri can be observed causing extensive flattening of the host cell, with small excrescences covering the surface of the infected erythrocyte; this is not observable at the light microscopy level (Conradie et al ., 2017). According to the morphology of available blood stages, phylogenetic analysis and the distortion effect on host cells, we refer to this haemogregarine as Karyolysus cf.…”

Monophyly of the species of Hepatozoon (Adeleorina: Hepatozoidae) parasitizing (African) anurans, with the description of three new species from hyperoliid frogs in South Africa

“…sp., thus explaining the low support of this group. Furthermore, H. ixoxo and H. theileri differ considerably in morphological structure (see Conradie et al 2017 ), and if compared with the phylogenetic and morphological relationship of H. involucrum n. sp. and H. tenuis n. sp.…”

Neofoleyellides boerewors n. gen. n. sp. (Nematoda: Onchocercidae) parasitising common toads and mosquito vectors: morphology, life history, experimental transmission and host-vector interaction in situ

“…Following the methods of Conradie et al (2017), fresh blood samples obtained from a highly infected guttural toad (S1 Table, AE180124C1) were also prepared for SEM. Thin blood smears were made on glass coverslips and Whatman® qualitative filter paper placed on the smears prior to drying.…”