Studies on woloszynskioid dinoflagellates III: on the ultrastructure and phylogeny of Borghiella dodgei gen. et sp. nov., a cold-water species from Lake Tovel, N. Italy, and on B. tenuissima comb. nov. (syn. Woloszynskia tenuissima)

Abstract

Ø. Moestrup, G. Hansen and N. Daugbjerg. 2008. Studies on woloszynskioid dinoflagellates III: on the ultrastructure and phylogeny of Borghiella dodgei gen. et sp. nov., a cold-water species from Lake Tovel, N. Italy, and on B. tenuissima comb. nov. (syn. Woloszynskia tenuissima). Phycologia 47: 54–78. DOI: 10.2216/07-32.1

Using ultrastructure and nuclear-encoded large subunit (LSU) rDNA sequences, the woloszynskioid dinoflagellates have been shown recently to form a polyphyletic assemblage. The first group comprises the family Tovelliaceae, with the genera Tovellia and Jadwigia. The present manuscript describes the second group, comprising Borghiella dodgei gen. et sp. nov. from the Italian Alps. The new genus differs in a number of ultrastructural features, of which the most important are the structure of the eyespot (type B sensu Moestrup & Daugbjerg) and the structure of the apical part of the cell. The resting cyst is smooth, in contrast to the cysts of other woloszynskioids such as Tovellia and some species of Woloszynskia. The new species has been previously confused with Tovellia sanguinea, which was responsible for colouring the water of Lake Tovel, in the Italian Alps, blood-red up to 1964. However, B. dodgei may form brown, never truly red blooms as in the case of T. sanguinea. The transverse flagellum of Borghiella carries, in addition to thin hairs found also in other dinoflagellates, a row of shorter, thicker hairs resembling the curly hairs on the homologous, anterior flagellum of the perkinsid Parvilucifera but apparently not observed in any other dinoflagellates. Woloszynskia tenuissima, a well-known cold-water dinoflagellate, has been re-examined using material isolated from Greenland. Based on partial LSU rDNA sequencing it is shown to be related to B. dodgei (sequence divergence only 1.1%) and is transferred to this genus as B. tenuissima comb. nov. We agree with the observations of von Stosch that the cysts of this species are spherical and smooth, in contrast to what was mentioned in the original description by Wołoszyńska.

Key Words::

• Freshwater
• Dinoflagellates
• Ultrastructure
• Taxonomy
• Phylogeny

ACKNOWLEDGMENTS

We thank Paul Silva and António Calado for comments on nomenclature, David Mann for preparing the Latin diagnoses, Niels Henry Larsen for experimenting to obtain dense cultures of B. dodgei sp. nov., and Henrik Levinsen for the sample from Greenland and information about the collecting site. Charlotte Hansen is thanked for help with sequencing. ND and ØM were supported by a grant from the Danish Science Research Foundation (No. 21-02-0539), ØM further from the Villum Kann Rasmussen Foundation and GH by a grant from the Carlsberg Foundation. This project was supported financially by the SALTO Project-Province Trento (Italy).