Life cycle and ultrastructure of Adelina tenebrionis (Sporozoea: Adeleidae) from Heteronychus arator (Coleoptera: Scarabaeidae)

Protists in the Insect Rearing Industry: Benign Passengers or Potential Risk?

As the insects for food and feed industry grows, a new understanding of the industrially reared insect microbiome is needed to better comprehend the role that it plays in both maintaining insect health and generating disease. While many microbiome projects focus on bacteria, fungi or viruses, protists (including microsporidia) can also make up an important part of these assemblages. Past experiences with intensive invertebrate rearing indicate that these parasites, whilst often benign, can rapidly sweep through populations, causing extensive damage. Here, we review the diversity of microsporidia and protist species that are found in reared insect hosts and describe the current understanding of their host spectra, life cycles and the nature of their interactions with hosts. Major entomopathogenic parasite groups with the potential to infect insects currently being reared for food and feed include the Amoebozoa, Apicomplexa, Ciliates, Chlorophyta, Euglenozoa, Ichtyosporea and Microsporidia. However, key gaps exist in the understanding of how many of these entomopathogens affect host biology. In addition, for many of them, there are very limited or even no molecular data, preventing the implementation of molecular detection methods. There is now a pressing need to develop and use novel molecular tools, coupled with standard molecular diagnostic methods, to help unlock their biology and predict the effects of these poorly studied protist parasites in intensive insect rearing systems.

Characteristic Light and Electron Microscopic Features of Adelina melolonthae, a Coccidian Pathogen of the European Cockchafer, Melolontha melolontha (Coleoptera/Scarabaeidae)

PURPOSE

The aim of this study was to investigate and document the characteristic electron microscopic features of the oocyst of Adelina melolonthae, a coccidian pathogen of the European cockchafer, Melolontha melolontha (Coleoptera: Scarabaeidae).

METHODS

Larvae of M. melolontha were collected at Ordu, Turkey. Each larva was dissected in insect Ringer solution. Adeleid oocysts from the tissue that is suspected to Contain coccidian infections were examined under a light microscope (Zeiss), a scanning electron microscope (FEI Quanta 200) and transmission electron Microscope (Philips EM 208).

RESULTS

Spherical to ellipsoidal oocysts measure ca. 24-44.5 µm (mean 35.6 µm) in diameter (n = 50) and include up to twelve sporocysts. The oocyst wall has double layers; the outer layer measured 400-500 nm in thickness and the inner one 10-25 nm. Sporocysts including two sporozoites are rounded ca. 11-12.5 µm (mean 11.7 µm) in diameter. The sporocyst wall consisted of only one 70-80-nm-thick layer. The sporozoites are ellipsoidal and measured 9-11 µm length and 3-4 µm in width. Sporocysts include residual bodies.

CONCLUSION

In the present paper, the morphology and ultrastructure of the oocyst of A. melolonthae is documented for the first time and compared with other Adelina and coccidian species infecting insects. The results in this study confirm his identification and justify the classification as a separate species A. melolonthae, which differs from other Adelina species.

DESCRIPTION OF THE FIRST KLOSSIA SPECIES (APICOMPLEXA: EUCOCCIDIORIDA: ADELEORINA: ADELEIDAE) INFECTING A PULMONATE LAND SNAIL, TRIODOPSIS HOPETONENSIS (MOLLUSCA: POLYGYRIDAE), IN NORTH AMERICA

Snails identified as Triodopsis hopetonensis were collected (n = 18) from the University of Arkansas-Fayetteville campus in December 2018. Additional snails were collected in April 2019 (n = 9) and in September 2019 (n = 9). Kidney tissues were examined using light microscopy, and polysporocystic oocysts were observed. Sporulated oocysts (n = 2) measured 78 ± 3.4 μm × 76 ± 2.9 μm with an irregular oocyst residuum and contained an estimated 44-55 tetrazoic sporocysts. The sporocysts (n = 10) measured 13 ± 0.5 μm × 11 ± 1.5 μm with an indistinct, irregularly placed, sporocyst residuum and usually contained 4 sporozoites, although an octozoic variant was observed. DNA was extracted from the snail kidney tissues and used as a template for polymerase chain reaction (PCR). PCR was used to determine the infection status of the snails; 13 of 36 (36%) specimens were found to be infected with a new Klossia species, and only 3 (8%) of these infections were detected using light microscopy. The complete nuclear 18S ribosomal DNA (1,800 bp) and mitochondrial genomes (6,775 bp) were generated, and they differentiated this parasite from the type species Klossia helicina and support the description of this new Klossia species, Klossia razorbacki n. sp. This is the first Klossia species to be described from any North American snail.

First record and distribution of Adelina sp. (Coccidia: Adeleidae) in populations of the Anisoplia segetum Herbst (Coleoptera: Scarabaeidae) in Turkey

In this study, an Adelina sp. (Coccidia) infection was determined for the first time from Anisoplia segetum (Coleoptera: Scarabaeidae). The infection was observed in the gut and fat body of the host. The determined oocysts were ellipsoidal and measured 36.3 (34-38) × 30.2 (27-32) μm. The number of sporocysts per oocyst varied from 7 to 15. The dizoic sporocysts were usually subspherical, 10.2 (9-12) × 8.9 (8-10) μm. Also, some developmental stages and unsporulated oocysts were determined with electron microscopical observations. The immature microgamonts were observed in different shapes, from ovoid to spherical. And the detected oval unsporulated oocyst was measured 4.9 μm in length and 3.6 μm in width. The formation and distribution of these pathogens were also presented in A. segetum populations.

Sexual differentiation and sex determination in the Apicomplexa

Protozoan parasites of the phylum Apicomplexa have complex life cycles involving various types of asexual division that allow rapid proliferation of parasites within one or more hosts. Such replication is punctuated by obligate sexual differentiation that produces male and female gametocytes. These stages are transmissible to haematophagous vectors or are necessary ultimately to form resistant cysts that are released into the environment. This article examines the sexual differentiation of apicomplexan parasites as it relates to the timing of commitment and the mechanism of the switch from asexual proliferation to the development of male and female sexual stages.

Intraerythrocytic development of species of Hepatozoon infecting ranid frogs: evidence for convergence of life cycle characteristics among apicomplexans

Intraerythrocytic development of the adeleorin apicomplexans Hepatozoon clamatae and Hepatozoon catesbianae were investigated in the bullfrog, Rana catesbeiana, the green frog, Rana clamitans melanota, and the Northern leopard frog, Rana pipiens. Merozoites emerging from hepatic meronts penetrated erythrocytes and underwent 1-3 rounds of binary fission to produce 2-8 merozoites. Following their release from infected erythrocytes, individual merozoites entered new cells and transformed into gamonts. Although this is the first report of intraerythrocytic development for a fully described species of Hepatozoon, a phylogenetic reanalysis of 11 species of Hepatozoon, 6 species representative of the 5 other hemogregarine taxa, 2 species of dactylosomatids, and 2 species of piroplasms, indicates that asexual reproduction of parasites within blood cells of vertebrates has arisen at least 3 times in the apicomplexan lineage that includes adeleorins and piroplasms. This method of asexual development, which is also observed in species of hemospororin genera such as Plasmodium, is discussed in the context of the evolution of apicomplexan life cycles. In addition to supporting the paraphyly of the genus Hepatozoon determined in an earlier study, this phylogenetic analysis featured a monophyletic group, consisting of the sister taxa Hemolivia and Karyolysus, that was the sister group to a clade consisting of the more derived hemogregarines, the dactylosomatids, and the piroplasms.