Parvilucifera

Parvilucifera is a genus of marine alveolates that behave as endoparasites of dinoflagellates. It was described in 1999 by biologists Fredrik Norén and Øjvind Moestrup, who identified the genus among collections of Dinophysis dinoflagellates off the coast of Sweden. Initially mistaken for products of sexual reproduction, the round bodies found within these collections were eventually recognized as sporangia, spherical structures that generate zoospores of a parasitic protist. This organism was later identified as P. infectans, the type species. The examination of this organism and its close genetic relationship to Perkinsus led to the creation of the Perkinsozoa phylum within the Alveolata group.

The complex life cycle of Parvilucifera consists of biflagellated zoospores that infect a variety of dinoflagellate species, become intracellular feeders or trophonts, and finally develop into sporangia that generate more zoospores. Parvilucifera species could help control dinoflagellate harmful algal blooms.

The name of this genus derives from Latin parvus 'small' and lucidus 'shining', referring to the small refractile appearance of the organisms.

The genus was first described by biologists Fredrik Norén and Øjvind Moestrup in 1999. It was isolated off the west coast of Sweden. The discovery was made through collections of Dinophysis dinoflagellates from the coast, which contained round bodies assumed to be products of sexual reproduction. After preservation in the refrigerator for two weeks, the dinoflagellates had all died but the round bodies remained. These were further investigated, and later found to be sporangia of a parasitic protist, later described as Parvilucifera infectans.

Initially, it was assumed that the observed zooids would grow into dinoflagellate cells, and there was much debate that sporangia did not arise from parasites. However, similar observations of the round bodies were made with plankton material from the same Swedish coast, which led to further investigation. Through combined examination of light and electron microscopy, alongside DNA sequencing of the emerging sporangia from the zooids, the organism displayed similarities with Perkinsus, a protist belonging to the Alveolata group (containing dinoflagellates, ciliates, apicomplexans and others). The mysterious zooids differed from dinoflagellates and apicomplexans in the ultrastructure of their flagellum, which led to the creation of a separate new phylum, Perkinsozoa, encompassing Perkinsus and the new genus Parvilucifera.

Following the discovery of P. infectans, the next species to be discovered was P. sinerae, the closest relative to P. infectans. Then followed the discovery of P. prorocentri (today Snorkelia prorocentri), P. rostrata, P. corolla and finally P. multicavata.

Parvilucifera is a genus of Alveolata, a diverse clade of eukaryotic microbes (protists) within the SAR supergroup. In particular, it belongs to the Perkinsozoa, a clade closely related to dinoflagellates according to molecular phylogenetics. For decades, this genus has been classified within the order Rastrimonadida as part of the Perkinsea class, without assignment to any family-rank taxon. In 2017, a new family Parviluciferaceae was created to accommodate Parvilucifera and two additional perkinsozoan genera: Dinovorax and Snorkelia.

As of 2020, there are four valid species in this genus. Two species, P. infectans and P. sinerae, have long been considered different species, but were later revealed to be the same through a set of genetic, morphological and ultrastructural data. One species, P. prorocentri, was formerly placed in this genus, but was later transferred to a new genus Snorkelia. Species are differentiated from each other through genetic distance and morphology. For instance, P. multicavata differs from the type species P. infectans by a higher number of apertures in their sporangia, although smaller in diameter. P. rostrata differs by the shape and size of the ornamentations covering the sporangium wall. Lastly, P. corolla is distinguished from others by the radial disposition of the zoospores within the maturing sporangium, among other traits such as the tear-drop shape of the zoospores themselves.