Conceptacle

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Conceptacle of Fucus Fucus conceptacle.tif
Conceptacle of Fucus
Cystocarp of Amphiplexia hymenocladioides Amphiplexia hymenocladioides.png
Cystocarp of Amphiplexia hymenocladioides

Conceptacles are specialized cavities of marine and freshwater algae that contain the reproductive organs. They are situated in the receptacle and open by a small ostiole. [1] Conceptacles are present in Corallinaceae, [2] and Hildenbrandiales, as well as the brown Fucales. In the Fucales there is no haploid phase in the reproductive cycle and therefore no alternation of generations. [3] The thallus is a sporophyte. [4] The diploid plants produce male (antheridia) and female (oogonia) gametangia by meiosis. The gametes are released into the surrounding water; after fusion, the zygote settles and begins growth. [5]

Contents

Two taxa, the corallines and Hildenbrandiaceae, bear conceptacles, although the striking difference between their formation indicates that the conceptacles are not homologous. [6] Similar structures also exist: cryptostomata are similar to conceptacles but differ having only hairs and are sterile; [5] caecostomata, are found only in Fucus distichus , in these the ostiole becomes blocked during development. [1]

Morphology

Conceptacles can measure from 40–150 μm in diameter in some Hildenbrandiales. [7] Some conceptacles are pits within the thallus, whereas others form raised domes protruding above it. [8] Conceptacles open to the environment via one or many pores, depending on the species and the type of conceptacle. [8]

Components

This is a central pillar constituting central calcified cells covered by cellular debris. [8] These sterile cells rise up from the conceptacle floor to form a peak. [9]

Some conceptacles form by the centripetal expansion of a hole near the thallus surface; in such cases, a roof forms by nearby filaments arching over and establishing themselves as short (often 1–9 cells long) [10] [11] filaments that cover the chamber, leaving a central pore through which the spores can escape. [12] If these filaments are vicarious they may produce a beak-like opening. [13]

In asexual conceptacles, the spores tend to be large, and so are squeezed in, filling the conceptacle chamber "like orange segments". [8]

Types of conceptacle

There are a range of different conceptacles, classified according to the nature of the spores that they contain; some species may possess as many as four distinct types. For example, Lithophyllum incrustans bears asexual, male, female and cystocarpic (strictly, a type of female) conceptacles, discussed below. [8]

These develop where weakly calcified cells break down to produce a cavity. In L. incrustans, Their columella is central and obvious (see above); it is accentuated by the spores (which may be bispores, tetraspores, etc.), which squeeze against the columella and conceptacle walls. [8] Asexual conceptacles may be uniporate or multiporate. [8]

These lack a columella. [8] L. incrustans has distinct male and female plants; the two conceptacle types never co-occur on the same thallus. [8] Male conceptacles tend not to sit as deep within the thallus as female conceptacles; their size is similar although their shape tends to differ. [8] Cells within circular regions within the perithallus lengthen to form sexual conceptacles, [8] leaving long, wefty cells around the walls of the conceptacle. [14] In the male conceptacles of Austrolithon, marginal filaments grow more quickly, bending in over the top of the conceptacle cavity and eventually setting up as distinct filaments that form the conceptacle roof. [12]

These are not associated with tissue demineralization; rather, they start to form at the centre (as a female conceptacle) and develop radially. [8] Being mature female conceptacles, these too lack a columella. [8]

Development

In most coralline algae, a cluster of reproductive cells forms in the middle layer of the alga, and is engulfed by the surrounding tissue, which grows up and over the reproductive cells to form a roof and a uniporate conceptacle. Caps may subsequently develop to protect the opening. [13] However the conceptacle may originate at any depth within the thallus, at the surface layer or at the basal perithallus. [8]

Four different modes of asexual conceptacle formation exist. In Corallina and Bossiella,

In the coralline Bossiella , the conceptacle instead forms in the outer layer. A thickening forms, which separates the outer epithallium from the underlying cortex; this thickening and the overlying epithallium will end up being the cap of the conceptacle, and the underlying cells will develop to become reproductive initials. [13] Once the cap is formed, the filamentous cells underneath begin to degrade. The tissue around the edge of the cap grows more quickly. This combination produces a chamber beneath the cap. [13]

Evolutionary history

Conceptacles appear in the fossil record at least as early as the Silurian. Similar structures have been noted in Prototaxites , which would imply that this giant land organism was not a simple fungus (as most paleontologists assume today) but a lichen. [15]

Related Research Articles

<span class="mw-page-title-main">Coralline algae</span> Order of algae (Corallinales)

Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of red, but some species can be purple, yellow, blue, white, or gray-green. Coralline algae play an important role in the ecology of coral reefs. Sea urchins, parrot fish, and limpets and chitons feed on coralline algae. In the temperate Mediterranean Sea, coralline algae are the main builders of a typical algal reef, the Coralligène ("coralligenous"). Many are typically encrusting and rock-like, found in marine waters all over the world. Only one species lives in freshwater. Unattached specimens may form relatively smooth compact balls to warty or fruticose thalli.

<span class="mw-page-title-main">Crustose</span>

Crustose is a habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. Crustose adheres very closely to the substrates at all points. Crustose is found on rocks and tree bark. Some species of marine algae of the Rhodophyta, in particular members of the order Corallinales, family Corallinaceae, subfamily Melobesioideae with cell walls containing calcium carbonate grow to great depths in the intertidal zone, forming crusts on various substrates. The substrate can be rocks throughout the intertidal zone, or, as in the case of the Corallinales, reef-building corals, and other living organisms including plants, such as mangroves and animals such as shelled molluscs. The coralline red algae are major members of coral reef communities, cementing the corals together with their crusts. Among the brown algae, the order Ralfsiales comprises two families of crustose algae.

The history of phycology is the history of the scientific study of algae. Human interest in plants as food goes back into the origins of the species, and knowledge of algae can be traced back more than two thousand years. However, only in the last three hundred years has that knowledge evolved into a rapidly developing science.

<i>Polysiphonia</i> Genus of algae

Polysiphonia is a genus of filamentous red algae with about 19 species on the coasts of the British Isles and about 200 species worldwide, including Crete in Greece, Antarctica and Greenland. Its members are known by a number of common names. It is in the order Ceramiales and family Rhodomelaceae.

In algal anatomy, a pit connection is a hole in the septum between two algal cells, and is found only in the red algae − specifically, all orders except the Porphyridiales and haploid Bangiales. They are often stoppered with proteinaceous "pit plugs". By contrast, many fungi contain septal pores − an unrelated phenomenon.

Phymatolithon is a genus of non geniculate coralline red algae, known from the UK, and Australia. It is encrusting, flat, and unbranched; it has tetrasporangia and bisporangia borne in multiporate conceptacles. Some of its cells bear small holes in the middle; this distinctive thallus texture is termed a "Leptophytum-type" thallus surface, and has been posited as a taxonomically informative character. It periodically sloughs off its epithallus, reducing its overgrowth by algae by as much as 50% compared to bare rock.

Trichocyte in algae are cells which grow on the outside of the thallus, from which hairs grow. In algae, trichocytes grow principally over the summer; their growth is mediated by water temperature and day length.

Bossiella is a genus of coralline algae with 5 recognised species. It reproduces via conceptacles; individual thalli only produce conceptacles of a single sex.

<span class="mw-page-title-main">Red algae</span> Division of archaeplastids

Red algae, or Rhodophyta, are one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority of species (6,793) are found in the Florideophyceae (class), and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats but relatively rare in freshwaters. Approximately 5% of red algae species occur in freshwater environments, with greater concentrations found in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, there are no terrestrial species, which may be due to an evolutionary bottleneck in which the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity.

<i>Lithophyllum</i> Genus of algae

Lithophyllum is a genus of thalloid red algae belonging to the family Corallinaceae.

<i>Hildenbrandia</i> Genus of algae

Hildenbrandia is a genus of thalloid red alga comprising about 26 species. The slow-growing, non-mineralized thalli take a crustose form. Hildenbrandia reproduces by means of conceptacles and produces tetraspores.

Archaeolithophyllum is a genus of conceptacle-bearing red alga that falls in the coralline stem group. It somewhat resembles Lithophyllum.

The epithallium or epithallus is the outer layer of a crustose coralline alga, which in some species is periodically shed to prevent organisms from attaching to and overgrowing the alga.

<i>Amphiroa</i> Genus of algae

Amphiroa is a genus of thalloid red algae under the family Corallinaceae.

<i>Jania</i> (alga) Genus of algae

Jania is a genus of red macroalgae with hard, calcareous, branching skeletons in the family Corallinaceae.

<i>Spongites yendoi</i> Species of alga

Spongites yendoi is a species of crustose red seaweed with a hard, calcareous skeleton in the family Corallinaceae. It is found on the lower shore as part of a diverse community in the southeastern Atlantic Ocean and the Indo-Pacific Ocean.

<i>Lithophyllum orbiculatum</i> Species of alga

Lithophyllum orbiculatum is a species of thalloid coralline algae, which are a red algae whose cell walls contain calcareous deposits.

<i>Hildenbrandia rubra</i> Species of alga

Hildenbrandia rubra is a marine species of thalloid red alga. It forms thin reddish crusts on rocks and pebbles in the intertidal zone and the shallow subtidal zone. It is a common species with a cosmopolitan distribution, and is able to tolerate a wide range of conditions.

Crustaphytum is a genus of red alga first discovered in Taoyuan algal reefs by Taiwanese scientists. The epithet “crusta” refers to crustose thallus and “phytum” refers to plant. Belonging to the family Hapalidiaceae in the order Hapalidiales, Crustaphytum is one kind of crustose coralline algae.

<i>Amphiroa beauvoisii</i> Species of thalloid red algae

Amphiroa beauvoisii is a species of thalloid red algae in the Corallinaceae family. It is widely distributed across the world, and can be found attached to rocks in intertidal areas. Individual organisms consist of a base of calcified material, tissue in the shape of branching fan-like planes growing out of it. It exhibits a wide range of morphologies based on where it is found, as well as different reproductive behaviors based on season and location.

References

  1. 1 2 Boney, A.D. (1969). A Biology of Marine Algae. Hutchinson Educational Ltd, London
  2. ↑ Irvine, L.M. and Chamberlain, Y.M. (1994). Seaweeds of the British Isles. Volume 1, Part 2B. Natural History Museum, London. ISBN   0-11-310016-7
  3. ↑ Fritsch, F.E. (1945). The Structure and Reproduction of the Algae. Vol 2. Cambridge University Press, Cambridge
  4. ↑ Smith, G.M. (1938). Cryptogamic Botany. Algae and Fungi. Second edition, Volume 1, McGraw-Hill Bok Company, Inc.
  5. 1 2 Flecher, R.L. (1987). Seaweeds of the British Isles. Volume 3, Part 1. British Museum (Natural History), London. ISBN   0-565-00992-3
  6. ↑ Pueschel, C. M.; Cole, K. M. (1982). "Rhodophycean Pit Plugs: an Ultrastructural Survey with Taxonomic Implications". American Journal of Botany. 69 (5): 703–720. doi:10.2307/2442960. JSTOR   2442960.
  7. ↑ Sherwood, A. R.; Sheath, R. G. (2003). "Systematics of the Hildenbrandiales (Rhodophyta): Gene Sequence and Morphometric Analyses of Global Collections". Journal of Phycology. 39 (2): 409–422. doi:10.1046/j.1529-8817.2003.01050.x. S2CID   86786840.
  8. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Edyvean, R. G. J.; Moss, B. L. (1984). "Conceptacle Development in Lithophyllum incrustans Philippi (Rhodophyta, Corallinaceae)". Botanica Marina. 27 (9): 391–400. doi:10.1515/botm.1984.27.9.391. S2CID   85190968.
  9. ↑ Johansen, H. W. (1968). "Reproduction of the Articulated Coralline Amphiroa Ephedraea". Journal of Phycology. 4 (4): 319–328. doi:10.1111/j.1529-8817.1968.tb04702.x. PMID   27068206. S2CID   24515929.
  10. ↑ Wilks, K.; Woelkerling, W. (1994). "An account of southern Australian species of Phymatolithon (Corallinaceae, Rhodophyta) with comments on Leptophytum". Australian Systematic Botany. 7 (3): 183. doi:10.1071/SB9940183.
  11. ↑ Townsend, Roberta A.; Huisman, John M. (2004). "= Epulo multipedes gen. et sp. nov. (Corallinaceae, Rhodophyta), a coralline parasite from Australia" (PDF). Phycologia. 43 (3): 288–295. doi:10.2216/i0031-8884-43-3-288.1. S2CID   48323629.
  12. 1 2 Harvey, A. S.; Woelkerling, W. J. (1995). "An account of Austrolithon intumescens gen. Et sp. Nov. And Boreolithon van-heurckii (Heydrich) gen. Et comb. Nov. (Austrolithoideae subfam. Nov., Corallinaceae, Rhodophyta)". Phycologia. 34 (5): 362–382. doi:10.2216/i0031-8884-34-5-362.1.
  13. 1 2 3 4 Johansen, H. W. (1973). "Ontogeny of Sexual Conceptacles in a Species of Bossiella (Corallinaceae)". Journal of Phycology. 9 (2): 141–148. doi:10.1111/j.0022-3646.1973.00141.x.
  14. ↑ Woelkerling, W.; Harvey, A. (1993). "An account of Southern Australian Species of Mesophyllum (Corallinaceae, Rhodophyta)". Australian Systematic Botany. 6 (6): 571. doi:10.1071/SB9930571.
  15. ↑ Schopf, J. M. (1978). "Foerstia and recent interpretations of early, vascular land plants". Lethaia. 11 (2): 139–143. doi:10.1111/j.1502-3931.1978.tb01298.x.

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