Scytosiphonaceae Family of Brown Algae

Oyster Thief, Colpomenia sinuosa. A representative of the Scytosiphonaceae Family of Brown Algae.

Phylogeny: Brown Algae of the Scytosiphonaceae Family look like plants but are in the Kingdom Chromista. Chromists are photosynthesizing organisms that used to be known as Protista. This diverse kingdom includes brown algae, diatoms, mildew, and malarial parasites. The Scytosiphonaceae Family is in the subkingdom Harosa, the infrakingdom Heterokonta, and the phylum Ochrophyta. Ochraphytes are multicellular brown-pigmented algae, characterized by their flagella and chloroplast structure. Further, the Scytosiphonaceae Family is in the class Phaeophyceae, the subclass Fucophycidae, and the order Ectocarpales. The Scytosiphonaceae Family is one twelve families in this order. The Scytosiphonaceae Family contains two tribes, twenty-four genera and around sixty species. The name Scytosiphonaceae comes from the Greek words meaning “leather tube or pipe”. This refers to the leathery hollow shape of many of these algae.

Morphology: Scytosiphon Algae have a complex, heteromorphic life history alternating between visible erect gametophytes and microscopic prostrate, filamentous sporophytes. In their erect form their thalli (main body) are very diverse. The thallus may be tubular without branches (Scytosiphon), have leaf-like blades(Endarachne) , have a globular sack-like structure, be net-like, or form a wrinkled mat (Colpomenia, Hydroclathrus) . It may be hollow or solid. They have a pigmented outer membrane and an inner layer of transparent medullary cells. Algae in this family are distinguished by cells containing a single cup-shaped chloroplast with one pyrenoid (microcompartment within the chloroplast). Some of the more elongate species in this family can reach 33 cm (13 inches) in length.

Habitat and Distribution: Scytosiphon Algae are generally found attached to hard substrates or other algae. They can live in wave-swept areas and protected waters. They are found from the intertidal zone to depths of 40 m (131 feet), though most are found in shallow sunlit waters conducive to photosynthesis. Scytosiphon Algae have a global distribution from polar to tropical seas. Unfortunately, the distribution of  species from this family in Mexican waters is poorly documented. At least six species from this family are found in Mexican waters but the actual number may be much higher.

Reproduction: Scytosiphon Algae  reproduction alternates between an asexual sporophyte generation and a sexual gametophyte generation. Adult sporophytes reproduce asexually through the production of spores, which produce gametophytes.  Gametophytes are microscopic and produce either male (sperm) or female (eggs) gametes. The gametophytes release their gametes into the water, where  fertilization occurs and forms a zygote. The zygote grows into a juvenile sporophyte. The sporophyte matures and completes the cycle.

Ecosystem Roles: Scytosiphon Algae use chlorophyll A and C to conduct photosynthesis to create food (amino acids, fats, sugars) from sunlight, water and carbon dioxide. Photosynthesis also provides the oxygen to fill the thallus in hollow species. Scytosiphon Algae are prey for generalist herbivores such as sea urchins, fish, and sea stars. They provide shelter and structure for various species of crustaceans, fish, mollusks, and other invertebrates.