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Heterosiphonia crispella var. laxa (Børgesen) M.J.Wynne

Reference
Cryptog.Algol. 6:87 (1985)
Conservation Code
Not threatened
Naturalised Status
Native to Western Australia
Name Status
Current

Scientific Description

Habit and structure. Thallus to 5 mm tall, with erect axes becoming decumbent and attached by pigmented monosiphonous multicellular filaments with digitate ends. Primary axes polysiphonous, ecorticate, with 4 pericentral cells, these slightly offset in successive segments; branching distichous, with pseudolaterals arising every 2 segments. Polysiphonous segments to 110 μm diam. and 140–180 μm long. Pseudolateral branches monosiphonous except for a basal polysiphonous segment, dichotomously divided every 2 cells, the cells 18–25 μm diam.

Reproduction. Tetrasporangial stichidia arising as one branch of a pseudolateral, with a 1- or 2-celled stalk; axial cells with 4 fertile periaxial cells, each bearing a spherical tetrahedrally divided tetrasporangium 35–40 μm diam., and 2 cover cells that divide transversely to cover the sporangium; periaxial cells and sporangia rotated 45° in successive segments. Fertile region of stichidia becoming elongate, 600–650 μm long and 75–90 μm diam., with sporangia developing acropetally and shed from the proximal region. Other reproductive structures not observed.

Distribution. Widespread in tropical seas.

Habitat. Epiphytic and epilithic in the subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 435–437 (2018)]