Life cycle of Ectocarpus siliculosus. Both Ectocarpus sexual and asexual life cycles are displayed. Gametes (right side) released from WT male gametophytes . The life history of Ectocarpus fasciculatus var. refractus (Kiitz.) Ardis. from Roscoff , France, has been studied in culture. This species proved to be the sporophytic. the sexual pheromones and infection of Ectocarpus by viruses. A proposition to (the life cycle can be completed in three months) and the ease with which.
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In this article we will discuss about Ectocarpus. After reading this article you will learn about: Classification of Ectocarpus 2. Occurrence of Ectocarpus 3. Smith classified Phaeophyceae into 12 classes which were grouped in three subclass on the basis of their life cycles: Ectocarpus is word-wide in distribution particulary in colder seas and Polar Regions.
Ectocarpus is very common on sea shore of Atlantic Ocean. Ectocarpus is found attached on sea rocks. Some species of Ectocarpus are epiphytic e. In India Ectocaupus is represented by about species. The ectocrapus body is mostly typically heterotrichous and differentiated into a creeping or prostrates system and b projecting an erect system. In some species one of the two systems may be reduced. In epiphytic forms the prostrate system is well developed and the erect system is reduced.
In many species of Ectocarpus, the thallus is sparingly to profusely branched, the cells are uniseriate, joined end to end in a row.
Lire some species, the older portions of the main branches are corticated by a layer of descending rhizoidal branches. In many species the terminal portion of a branch may end in a colourless hair with a basal meristem Fig. The cells are generally rectangular, uninucleate and the nucleus is placed in the region of the central vacuole, suspended by protoplasmic threads.
The cell contains a few parietal band shaped chromatophores with irregular branches E. Fucosan vesicles or granules are present in large number along with pyrenoid like bodies in the cell.
Ectocarpus – Wikipedia
The reserve food material is in form of laminarin and mannitol. The cell wall is differentiated into two layers, the inner firm layer is made of cellulose and the outer gelatinous layer contains alginic acid. The growth in the prostrate system is apical and in the erect system it is diffuse and intercalary.
In intercalary or trichothallic growth meristem is located at the base of a hair E. The growth is apical in E. The asexual reproduction takes places with the help of biflagellate zoospores. These zoospores are produced in unilocular and plurilocular sporangia Fig. These two types of zoosporangia may be produced on the same plant or on different plants.
The unilocular zoosporangia form haploid zoospores and the plurilocular sprogania form diploid zoospores. The unilocular sporangia develop singly on tips of small branchlets.
The terminal cell of the branchlet gradually increases in size and becomes ellipsoidal. This cell functions as sporangial initial Fig. The nucleus of sporangial cell first divides by meiotic division followed by many equational divisions. This results in formation of haploid nuclei Fig. The nuclear divisions are not followed by wall formation and the sporangium remains unilocular Fig.
Ectocarpsu nucleus of the sporganiuin gets surrounded by protoplast segment and ultimately transforms into zoospores Fig. Each zoospore is pyriform, uninucleate with two laterally inserted unequal flagella. The anterior flagellum is longer, pantonematic and directed forward while the posterior is shorter, acronematic and directed backward Fig.
The zoospores discharge en-masse in gelatinous matrix through a terminal pore in sporangium. The zoospores after being discharged remain in spherical mass at ectocaepus apex of sporangium. The zoospores remain inactive for seconds then become free and swim in water. They remain motile for about 30 minutes. These zoospores are haploid, they withdraw flagella and attach to the substratum by their anterior ends. The zoospores germinate within hours to produce a new Ectocarpus plant which is similar liff sporophytic plant in structure Fig.
These plants are called gametophytic plants as on maturity they bear plurilocular gametangia. According to KnightSchussing and Kothbaouerrarely the zoospores released from unilocular sporangia, show pairing and fusion but the fate of such zygotes is not known.
Like unilocular sporangia, the plurilocular sporangia also develop from the terminal cells of the branchlets of diploid sporophytic ilfe. The cell which functions as liife initial Fig. It repeatedly undergoes transverse divisions to form a row of cells Fig. Then vertical divisions start in all the cells starting with the median cells of the row. Many transverse and vertical divisions result in formation of cubical cells arranged in transverse tiers Fig.
The cells are arranged in regular rows. This multicellular structure is called plurilocular sporangium. The protoplast of each diploid uninucleate cell of the sporangium is transformed into a single biflagellate zoospore Fig.
The zoospores of plurilocular and unilocular sporangia are identical in structure but zoospores of plurilocular sporangia are diploid and zoospores of lfie sporangia are haploid. The mature zoospores are liberated from the sporangium through apical or lateral pores. The zoospores remain motile for hours and then germinate into diploid thallus which later on bears unilocular and plurilocular sporangia.
These diploid zoospores multiply only sporophytic plants and they do not play any role in alternation of generation. The formation of unilocular and plurilocular sporangia is affected by environmental conditions like temperature and salinity of water.
The sexual reproduction may be isogamous, anisogamous or oogamous. Most of the Ectocarpus species are anisogamous.
Quick Notes on Ectocarpus (With Diagram) | Algae
The gametes are biflagellate, motile and are produced in plurilocular gametangia borne on haploid or unisexual plants. The plurilocular gametangia and plurilocular sporangia are similar in structure and development. The plurilocular gametangia are either sessile or stalked and vary in shape from ovate to siliquose.
The plurilocular gametangia develop singly from the terminal cell of the lateral branchlets. The gametangial initial divides transversely to form a row of cells. Further divisions are transverse and vertical in these cells to make hundreds of cubical cells arranged in transverse layers. The protoplast of each cubical cell in gametangium metamorphosis into single biflagellate pyriform gamete. The gametes are liberated ectocarpua water through terminal or lateral pore in gametangium.
Hence the reproduction is isogamous but physiologically anisogamous.
The fertilization occurs between gametes from separate plants. These gametes are morphologically identical but one is less active, becomes passive after a short period and behaves as female gamete. The more active gametes are considered male. The active male gametes cluster around female gamete and cling themselves by their anterior flagellum.
It is lire as clump formation. In this clump formation Fig. The gametes fuse to form a diploid zygote. In other species of Ectocarpus gametes from same plant can fuse to form a zygote showing isogamous reproduction. The smaller gametes are produced in micro-gametangia and the larger are produced in bigger mega-gametangia.
The micro-and macrogametes after liberation fuse and form zygote, Fig. The largest mega-gametangia represent oogonia and the smallest micro-gametangia represent antheridia Fig.
The egg and antherozoids produced by the mature mega-gametangia and micro-gametangia fuse to form zygospore. The medium sized meso-gametangia give rise to medium size gametes. They do not fuse but develop new plant parthenogenetically. In isogamous species fctocarpus fusing gametes are morphologically and physiologically similar.
The two gametes of same gametangium or from two different gametangium of same thallus fuse to from zygospore. In physiologically anisogamous species, gametes from two filaments of different strains fuse.
The female gamete after liberation secretes a volatile sexual attractant sirenine. A large number of male gametes are attracted and cluster around female gamete to make clump formation Fig.
After sometime one ectocatpus gamete fuses egg to make zygospore and other gametes detach themselves from female gamete. The zygospore germinates after days. Its diploid nucleus divides mitotically to make diploid Ectocarpus plant. The sexual thalli of Ectocarpus are haploid. The haploid ectocatpus bear plurilocular gametangia. The isogametes or anisogametes fuse to form diploid zygospore.
The diploid nucleus of zygospore divides mitotically during germination. This forms diploid, sporophylic plants. The diploid plants bear both unilocular and plurilocular sporangia. The zoospores formed in plurilocular sporangia are diploid and give rise to diploid sporophytic plants on germination. The zoospores formed in unilocular sporangia cycoe haploid and on germination form haploid gametophytic thalli.