Apicomplexa

– Human and animal diseases caused by representatives of the phylum Apicomplexa represent a major world health problem with a considerable impact on the global economy. The apicomplexans exhibit specific adaptations, evolved under distinct evolutionary pressures, for invading and surviving within their hosts.

It is generally accepted that ancestral Apicomplexa parasitised marine annelids and their radiation and adaptation to a parasitic lifestyle took place before the era of vertebrates. In contrast to human pathogens, the early-emerging Apicomplexa, which are restricted to invertebrates, remain poorly understood despite their enormous diversity. Basal lineages, however, appear to be important in the comprehension of evolutionary pathways and phylogenetic relations within the Apicomplexa.

Although some ancestral features have led to a reputation for being 'primitive', they often exhibit novel and sophisticated lifestyle adaptations. Our aim is to improve our understanding of the survival and parasitic strategies of Apicomplexa occurring in different environments. In doing so, we focus on the early-emerging lineages, including the lower coccidia, gregarines and cryptosporidia.

Fig. 1. Protococcidian Eleutheroschizon duboscqi. Scanning electron microscopy. / Photo: Andrea Valigurová

Fig. 2. Macrogamont of protococcidian Eleutheroschizon duboscqi. Transmission electron microscopy. / Photo: Andrea Valigurová

Fig. 3. Gamonts of blastogregarine Siedleckia nematoides attached to the host intestine. Confocal laser scanning microscopy – immunofluorescence. / Photo: Andrea Valigurová

Fig. 4. Eugregarine Lecudina tuzetae attached to the host intestine. Scanning electron microscopy. / Photo: Andrea Valigurová

Fig. 5. Eugregarine Lecudina tuzetae, a view of the apical end. Scanning electron microscopy. / Photo: Andrei Diakin