| Austrolithoideae | |
|---|---|
Scientific classification  | |
| (unranked): | Archaeplastida |
| Division: | Rhodophyta |
| Class: | Florideophyceae |
| Order: | Corallinales |
| Family: | Hapalidiaceae |
| Subfamily: | Austrolithoideae |
| Genera [1] | |
The Austrolithoideae are a subfamily of coralline algae. [1]
Live rock is rock from the ocean that has been introduced into a saltwater aquarium. Along with live sand, it confers to the closed marine system multiple benefits desired by the saltwater aquarium hobbyist. The name sometimes leads to misunderstandings, as the "live rock" itself is not actually alive, but rather is simply made from the aragonite skeletons of long dead corals, or other calcareous organisms, which in the ocean form the majority of coral reefs. When taken from the ocean it is usually encrusted with coralline algae and inhabited by a multitude of marine organisms. The many forms of micro and macroscopic marine life that live on and inside of the rock, which acts as an ideal habitat, give it the name "live rock".
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.
Coralline rock is a type of rock formed by the death of layers of coralline algae. It is visually quite bright like the algae, and is often desired as aquarium decoration. Since it is formed from the dead algae, it contains some nutrients and calcium carbonate, which has allowed it to be used in some building structures.
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.
Rhodoliths are colorful, unattached calcareous nodules, composed of crustose, benthic marine red algae that resemble coral. Rhodolith beds create biogenic habitat for diverse benthic communities. The rhodolithic growth habit has been attained by a number of unrelated coralline red algae, organisms that deposit calcium carbonate within their cell walls to form hard structures or nodules that resemble beds of coral.
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. Conceptacles are present in Corallinaceae, 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. The thallus is a sporophyte. 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.
Wataru Ishijima was a paleontologist and geologist. Ishijima was one of the most prolific researchers of fossil calcareous algae. After graduating from the Imperial Fisheries Institute in 1927, Ishijima joined the Institute of Geology and Paleontology, Faculty of Science, Tohoku Imperial University (Sendai) from 1927–1931. He then worked at the Institute of Geology, Taihoku Imperial University (Taipei) during 1942–1945 and then at the Rikkyo University (Tokyo) from 1945–1980. His doctoral dissertation was submitted to Tohoku University and was privately published by Yūhodō. He described a total of 139 taxa of fossil calcareous algae including at least 114 species of Corallinales, and he produced more than 45 publications on coralline algal taxonomy.
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.
Graticula, formerly incorrectly named Craticula, is a genus of Palaeozoic coralline alga. They form the framework of reef rocks in the Silurian of Gotland, from the Högklint, Slite and Halla groups.
The Rhodogorgonales are an order of red algae, a sister group to the corallines. They are always thalloid and calcified; their calcification is very different from the corallines, as individual calcite crystals are deposited in the cell wall of specialised cells; this suggests that the evolution of calcification may have been independent from the corallines. They have no fossil record.
The extinct Solenoporaceae have traditionally been interpreted as a group of red algae ancestral to the Corallinales.
The Sporolithaceae are one of the two extant families of coralline algae. They are differentiated from the other family, the Corallinaceae, by their formation of conceptacles with one or many pores.
The Lithophylloideae are a monophyletic subfamily of Corallinaceaen Coralline algae with uniporate conceptacles.
The Metagoniolithoideae are a monogeneric subfamily of genucilate Corallinaceaen coralline algae.
The Corallinoideae are a subfamily of coralline algae. All its genera are geniculate.
The Choreonematoideae are a monogeneric nongeniculate subfamily of Coralline algae.
Archaeolithophyllum is a genus of conceptacle-bearing red alga that falls in the coralline stem group. It somewhat resembles Lithophyllum.
Petrophyton is a genus of alga that falls in the coralline stem group.
Halysis is a genus of red alga thought to fall in the coralline stem group. It has only been recovered in thin sections, and thus is only known in two dimensions; however, an interpretation as a sheet of cells rather than a sheet of tubes or a single row of cells is the most plausible.
Palaeoaplysina is a genus of tabular, calcified fossils that are a component of many Late Palaeozoic reefs. The fossil acted as a baffle to trap sediment. Historically interpreted as a sponge or hydrozoan, recent studies are converging to its classification in the coralline stem group, placing it among the red algae.