This study focused on the attachment strategy, cell structure and the host-parasite interactions of the protococcidian Eleutheroschizon duboscqi, parasitising the polychaete Scoloplos armiger. The…

Gregarines are a notably understudied but widespread group of protists that colonise aquatic and terrestrial invertebrates. This limited understanding…

The paper focuses on a new species of gregarines—Licinophilus depressus n. gen. sp. n., which was found in Licinus depressus (Paykull, 1790) (Coleoptera, Carabidae). The individuals of L. depressus ground beetle were collected on the bank of the Dnipro River, Ukraine and examined for the presence of gregarines in the guts. In the parasites discovered in the midguts, we measured the morphological parameters and their ratios, analyzing how they change in relation to the age of the specimens. According to our measurements, the species turned out to be incomparable to any of the ones described in the scientific literature. Because the gregarine specimens formed syzygies at late stages, were observed to have monogenous life cycle and a septum between the protomerite and deutomerite at all stages of development, and also rudimentary epimerite, they were classified to the Septatorina suborder, Stenophoricae superfamily, Stenophoridae family, and distinguished into a new genus due to the fluctuating septum between the protomerite and deutomerite.With age, the width of the segments does not change, while the gregarine increases in size due to significant elongation of the deutomerite. The most varying parameters of this species of gregarines were the deutomerite length (DL), the deutomerite length axis (DLA), and the total length of gregarine (TL) for which the coefficient of variation exceeded 30%. All the studied morphometric indices, except for the ratio of the deutomerite length to the deutomerite width (DL/DW), exhibited weak association with the age and sizes of gregarines. The indices such as the ratios of the epimerite length to the length of the protomerite-epimerite complex (EL/PECL), the protomerite length to the protomerite-epimerite complex (PL/PECL), the epimerite length to the epimerite width (EL/EW), the protomerite length to the protomerite width (PL/PW), the protomerite width to the septum width (PW/SW), the deutomerite width to the protomerite width (DW/PW), the nucleus length to nucleus width (NL/NW), and also DLA remained constant in this gregarine during growth, and therefore they can be used as constant diagnostic features.