Acetabularia acetabulum is a species of green alga in the family Polyphysaceae. It is found in the Mediterranean Sea at a depth of one to two metres.[2]
This alga adheres to the substrate with rhizoids (root-like processes), and these are the only part of the alga present in the winter. The thallus consists of a single cell, and in the spring a slender stem develops from the holdfast, growing vertically to a length of about 5 cm (2 in). Growth is interrupted at intervals while a whorl of hairs develop which encircle the stem, branching dichotomously. As the stem lengthens and more whorls grow, the lower hairs drop off leaving behind a circular scar. When the stem is fully developed, a disc-shaped cap up to 1.2 cm (0.5 in) wide grows at the tip, the whole frond resembling a pale green parasol; further whorls of hairs grow from the upper surface of the cap.[3][4]
Before cap expansion, the organism consists of a single cell with a single nucleus, located at the base of the stem.[3] As the cap expands, the nucleus divides once by meiosis after which it divides multiple times by mitosis, producing thousands of haploid "secondary" nuclei. These migrate up the stem into the cap, each becoming enclosed in a gametangium containing the nucleus and a small amount of cytoplasm. Inside the gametangium, the nucleus undergoes further repeated mitotic division, so that by the end of summer, when the cap disintegrates, thousands of "tertiary" nuclei are released into the sea as gametes from each gametangial ray. Fertilisation occurs in the open water, and the zygotes settle on the seabed.[3]
This alga is unicellular, each frond being formed from a single large cell containing several million chloroplasts.[5] These are in constant motion: in the daytime, they move to expose to themselves to the maximum degree possible to the light and the stems appear uniformly dark green, while at night they aggregate into clusters and the stem becomes pale green. This effect can be demonstrated by shining a ray of blue light on a stem in the dark and extinguishing it some time later, forming a transient green band.[5]
This alga has been used as a model organism in developmental biology, being useful for this purpose because of the enormous size of its single cell with its single nucleus, and its complex cell structure and development.[3]
The main storage polysaccharide of Acetabularia acetabulum is starch as granules within the chloroplast's stroma.[2]
Predators of Acetabularia acetabulum include the sea slug Elysia timida.[2]
Acetabularia acetabulum is a species of green alga in the family Polyphysaceae. It is found in the Mediterranean Sea at a depth of one to two metres.
Acetabularia acetabulum, l'acétabulaire de Méditerranée ou ombrelle de mer[1], est une espèce d'algues vertes de la famille des Polyphysaceae.
Comme toutes les acétabulaires cette algue verte est en fait composée d'une seule cellule et n'est donc visible que lorsqu'elle produit son chapeau (voir "Cycle de vie" plus bas), c'est-à-dire en été ou à la fin du printemps. Elle est fixée au substrat par des rhizoïdes, près desquels se situe le noyau de la cellule.
Lors de la reproduction, la cellule produit un pédicule pouvant atteindre 50 mm de hauteur puis un chapeau en forme de disque concave de 5 à 12 mm de diamètre[1]. Ce chapeau, à bords lisses, comportant de fines stries rayonnant à partir du centre, est vert pâle, vert bleuté ou presque blanc.
Le zygote s'implante sur le substrat rocheux grâce à des rhizoïdes. Afin de produire des gamètes, il produit d'abord un pédicule qui, lorsque sa croissance est maximale (pour cette espèce, une cinquantaine de millimètres), forme un chapeau en forme de disque constitué en fait de poches contenant des gamétocystes. À maturité, les poches s'ouvrent et les gamétocystes sont libérés. Puis les gamétocystes s'ouvrent à leur tour, libérant les gamètes. La fécondation a lieu dans l'eau libre et forme un nouveau zygote.
C'est une algue essentiellement méditerranéenne qui préfère les substrats rocheux et les zones calmes, peu battues par les vagues. Elle aime la lumière et vit à faible profondeur (généralement entre 2 et 5 m de profondeur, ou davantage si les eaux sont limpides[1]), mais ne supporte guère d’être émergée.
Selon AlgaeBase (29 avr. 2013)[2] :
Acetabularia acetabulum, l'acétabulaire de Méditerranée ou ombrelle de mer, est une espèce d'algues vertes de la famille des Polyphysaceae.
Jadranski klobučić (Acetabularia acetabulum), vrsta zelene alge (Chlorophyta) iz porodice Polyphysaceae koja je zbog svojih vidljivo izraženih radijalnih rebara na bijelom klobuku nalik gljivi ili kišobranu i dobila naziv jadranski klobučić ili jadranski kišobrančić[1]. Tipična je vrsta roda Acetabularia.
Jadranski klobuk se sastoji od tri dijela, rizoid koji nalikuje na skup kratkih korijena, duge peteljke i klobučića na vrhu.
Peteljka je dužine 8-10 cm visine a kada dosegne svoju punu veličinu počinje stvarati klobučić promjera do 10 mm. koji nakon kalcifikacije postaje bjelkast ili svijetlozelen. razlog tomu je taj da alga sadrži vapnenac (kalcijev karbonat)
Klobučići se razvijaju u kasno proljeće a u njemu se razvijaju gamete koje se krajem ljeta oslobađaju u moru. Muške i ženske gamete nalaze se u moru spajaju u nove stanice i padaju na dno gdje se pričvršćujuuz kamenu podlogu; peteljka opstaje tijekom cijele godine.
Cijela je alga jedna stanica zbog čega je čest predmet eksperimenata Genetičara.[2]
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Jadranski klobučić (Acetabularia acetabulum), vrsta zelene alge (Chlorophyta) iz porodice Polyphysaceae koja je zbog svojih vidljivo izraženih radijalnih rebara na bijelom klobuku nalik gljivi ili kišobranu i dobila naziv jadranski klobučić ili jadranski kišobrančić. Tipična je vrsta roda Acetabularia.
삿갓말(Acetabularia acetabulum)[1]은 열대 및 아열대의 산호초 해역에 살고 있는 아름다운 조류로, 그 모양은 마치 우산을 펴놓은 듯하다. 몸길이는 4-6cm로, 우산 부분은 생식 기관이며 이 안에 암·수배우자가 들어 있다. 어린 몸체는 단세포인 봉상체로 밑부분에 큰 복상핵 하나가 있다. 우산 모양이 만들어질 때 핵분열이 일어나서 다수의 핵이 생기며, 다시 생식 세포가 생길 때의 감수 분열 결과 단상의 핵을 가진 암·수배우자가 만들어진다. 그 후 헤엄쳐 나온 암·수배우자는 접합자를 만들고, 접합자는 발아하여 모체와 같은 모양으로 자라게 된다.
삿갓말의 무리에는 몇 가지 종류가 있는데, 대부분은 열대 및 아열대의 바다에 살고 있다. 특히, 최근에는 접붙이기에 의한 유전 실험이나 생리 실험 재료로 이 같은 삿갓말들이 많이 이용된다.
