Morphological, molecular, and chromosomal identification of dwarf haploid parthenosporophytes of Tauya basicrassa (Phaeophyceae, Laminariales) from the Sea of Okhotsk

Morphological, molecular and chromosomal studies were carried out on Tauya basicrassa, an endemic kelp species distributed on the northern continental coast of the Sea of Okhotsk in Russia. The sporophytes of T basicrassa grow up to 3-6 m long, 1.8-2.2 m wide, and 6.5-7 kg wet weight. The thallus has a blade with very thick narrow basal portion and thinner and much broader upper portion, which usually splits into 3 bullated lobes. A dwarf laminariacean alga, which did not show any morphological similarity to the other species of the order Laminariales, was found from the same locality. The blade of this alga is thin and soft, reached 26-34 cm long and 6-6.5 cm wide and had 4 longitudinal rows of bullations that covered the entire blade. Molecular analysis showed that the dwarf alga has 100% sequence identity in plastid-encoded RuBisCo spacer, mitochondrial cytochrome c oxidase subunit 1 and nuclear-encoded rDNA genes with normal sporophytes of T basicrassa, indicating that they are different life forms of the same species. Fluorescent DAPI staining showed that the nucleus in the normal sporophyte was 50-65% larger than those of the dwarf ones. Chromosome count using acetocarmine staining showed n = ca. 20 for the normal sporophytes of T basicrassa and n = ca. 10 for the dwarf one. These results suggest that the dwarf thallus is a haploid parthenosporophyte of T. basicrassa, which developed in nature. This is the first evidence of parthenosporophytes of the laminariacean algae occurring naturally in the field.