Description
Summary:International audience Results and discussion. Molecular analysis of two independent markers revealed eight monophyletic species-level lineages. Surprisingly, Leucosolenia complicata was found only in the NorthEast Atlantic, where it shows stable diagnostic morphological traits: tri-and tetractines with unpaired actines commonly longer than paired ones and the presence of both lanceolate diactines and small trichoxeas. In contrast, in the White sea Leucosolenia diversity is represented by a complex of three pseudo-cryptic species, which differ in external features, cytology, skeleton arrangement and spicule morphology. Leucosolenia sp. 1 is characterized by lanceolate diactines and T-shaped tri-and tetractines with unpaired actines commonly shorter than paired ones. Leucosolenia sp. 2 possess smooth and spined trichoxeas, which form prominent spicular crown around oscula and cover cormus tubes, making them hispid. In addition its tri-and tetractines are thin, many of them are abnormal. Tetractines are rare, presented only in oscular rim. Leucosolenia sp. 3 is easily distinguished by voluminous spherical cormus with one or several long oscular tubes, presence of lanceolate diactines and T-or V-shaped tri-and tetractines, some of which are abnormal. In addition, we found peculiar type of mesohyl cells with specific inclusions, occurring in large number. Leucosolenia sp. 1 and Leucosolenia sp. 2 are most common species in the White sea. In the upper intertidal zone they usually occurred sympatrically, while deeper waters are inhabited mostly by Leucosolenia sp. 1. Leucosolenia sp. 3 is also found in deep waters, but restricted to a single locality near Krestovye islands, which have specific fauna.