Morphological and molecular-biological characteristics of two gregarine species (Eugregarinida: Gregarinidae) associated to Phaedon brassicae and Phyllotreta striolata (Coleoptera: Chrysomelidae)

•We find a new gregarine parasite in the population of striped flea beetle and that was grouped in eugregarine.•We also previously reported another gregarine parasite from daikon leaf beetle which coexist in cabbage field.•Two Coleopterans had their own gregarine parasite species association.•The gregarines and their coleopteran hosts have species-specific interaction via co-evolution.

A new gregarine species (Eugregarinida: Gregarinidae) was previously reported from daikon leaf beetle, Phaedon brassicae at Daegwallyeong in Korea. Here, we reported another novel gregarine species from the striped flea beetle, Phyllotreta striolata (Coleoptera: Chrysomelidae). The beetles were collected from the three locations; Pyeongchang (760 m), Hoengseong (466 m), and Inje (290 m), Gangwon province during July to September. In this paper, we present the morphological and molecular-biological characteristics of Gregarine species associated to P. brassicae and P. striolata. The size and body shape at mature trophozoite stage were the main morphological diagnostic characteristics of those species. Gregarines from P. brassicae were bigger in size (100 μm) with square shaped body while Gregarines from P. striolata were slightly smaller in size (80 μm) with egg shaped body. Based on the partial 18S rDNA sequence, this gregarine species was also grouped in eugregarine, and showed 85% homology to Gregarina sp. associated to P. brassicae. However, histological section result showed that each species had their own gregarine parasite beetle association. Species-specific parasitism was confirmed in local populations' beetles. There was positive relationship between infection rates, and the elevation of locations for gregarine related to P. striolata. Therefore, we suggested that the gregarines and their coleopteran hosts have species-specific interaction via co-evolution.

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