#brown algae

Southern bull kelp (Durvillaea sp.) in Antarctica

Sex determination is a cornerstone of biology, yet many mysteries remain about how sex chromosomes evolve, especially outside familiar mammal and bird systems. Unlike mammals, where sex is set at fertilization by XX/XY chromosomes, brown algae determine sex during spore formation based on U (female) or V (male) sex chromosomes. Despite their importance, the rise, evolution, and demise of U/V sex chromosomes have remained an enigma. This new research, published in Nature Ecology & Evolution, demonstrates that these specialized sex chromosomes arose between 450 and 224 million years ago. A key finding is the identification of a pivotal male-determining gene, MIN, as well as six other core sex-linked genes, which have astonishingly remained almost unchanged across these vast evolutionary timescales.

Lichen-shaped, but in a rock pool. Looks like Pseudoralfsia verrucosa, a kind of brown seaweed with a crustose growth habit.

First described as Fucus retroflexus by French naturalist Jacques Labillardière in 1807. It became the type species of the genus Cystophora in 1848, when it was renamed by Swedish botanist, phycologist, and taxonomist J.G. Agardh in 1848. 'retroflexa' refers to the way the lateral branches of the fronds are bent backwards.

A brown algae found on NZ and Australian coastlines, but preferring more sheltered reefs than other Cystophora species.