Genus – Ectocarpus
- Plant body is cosmopolitan in distribution mainly in colder areas of temperate and polar region and along Atlantic coast
- About 16 species are reported in India.
- Majority of species are lithophytes (attached on rocks.)
- Some are marine algae few are fresh water forms.
- Common Indian species of Ectocarpus are Ectocarpus arabicus, E. filife, E.enhali etc.
- Plant body is multicellular, filamentous, macroscopic, branched and heterotrichous divided into prostrate and erect system.
- Prostrate system include filamentous irregularly branched and attached to substratum.
- Erect system – It arise from prostrate system and consist of many branched which are uniseriate (single row of cells).
- Branching is lateral and tapers into series of elongated cells.
- Cells are uninucleate and possess one or many irregular band discoid chromatophores.
- Reserve food material is oil, mannitol.
Life cycle of Ectocarpus:
Reproduction: Ectocarpus reproduces both sexually and asexually.
- It take place by zoospores.
- Zoospores are biflagellate having one whiplash and other tinsel type of flagellum.
- The diploid plant body develops two type of sporangia.
- These are unilocular sporangia and plurilocular or neutral sporangia.
- The unilocular sporangia develops develop haploid zoospores and plurilocular sporangia develop diploid zoospores.
Produced by fusion of two biflagellated motile gametes produced in plurilocular gametangia in gametophytic plants. Fusion occurs between gametes from different plant (dioecious) or from same plants (monoecious).
Sexual fusion may be:
Fusing gametes are identical in size, shape, structure, activity
Fusing gametes are identical in size, shape, structure, differ in activity.
Fusing gametes are unequal in size.
- During fertilization many male gametes around the female gametes and gets entangled by anterior large flagellum. The stage is called clump formation.
- Out of many only one male gamete fuses with female gamete and remaining gametes gets destroyed.
- The uniting gamete form zygote through karyogamy and plasmogamy.
Germination of zygote:
- Zygote undergoes germination without any reduction division.
- It develops into sporophytic plant body.
- The sporophytic plant again develops unilocular and plurilocular sporangia.
Alternation of generations:
- The sexual thalli of Ectocarpus are haploid.
- They produce only plurilocular gamentangia.
- By isogamy or anisogamy gametes fuse to form diploid zygote.
- Plurilocular sporangia produce diploid zoospore which again give rise to diploid sporophytic plant body and unilocular sporangia form haploid zoospore which on germination give rise to haploid gametophytes.
- This type of life cycle is called Isomorphic Diplohaplontic.
Economic importance of Ectocarpus:
- It causes fouling of the ships.
- It is a part of food chain in ocean as it is eaten by some fish.