Penicillus (algae)

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Penicillus
Shaving brush algae (Penicillus capitatus)

Shaving brush algae ( Penicillus capitatus )

Systematics
without rank: Chloroplastida
Department : Chlorophyta
without rank: Chlorophyceae
Order : Bryopsidales
Family : Udoteaceae
Genre : Penicillus
Scientific name
Penicillus
Lam.

Penicillus is a genus of green algae from the class Chlorophyceae . Together with other organisms, they belong to the important group of calcareous algae , whichcontributeto the formation of calcareous biogenic sediments through the production of carbonates.

features

Penicillus dumetosus , the "shaving brush alga"

The calcified, upright thallus reaches a length of 15 centimeters. It consists of three zones. In the ground is an onion-shaped, root-like holding organ made of numerous finely branched threads. At the top, this goes over into a stem region about 10 centimeters long. The cell threads of the stem are predominantly oriented lengthways and interwoven, they form a bark-like outer zone through lateral branches. The stem can, depending on the environmental conditions, especially the flow, be cylindrical or flattened. Depending on the type, it merges abruptly or gradually into a brush-shaped crown (capitulum) made of thin threads, which is created when the threads of the stalk region are often forked (dichotomous), rarely also in three parts, creating an irregular, bush-like structure arises, which can be spherical, hemispherical or pear-shaped in outline. The bark of the stem and the siphons of the capitulum are calcified on the outside, this calcareous shell consists of aragonite . In mature specimens of Penicillus capitatus , about half of the thallus (47 to 56 percent) consists of calcium carbonate. In a survey in Harrington Sound, Bermuda, the species produced around 30 grams of calcium carbonate per square meter of seabed per year. It thus contributes to the formation of reefs in coral reefs.

As typical for the order of the Bryopsidales (syn .: Caulerpales), the thallus of Penicillus is not divided into individual cells, it is in the form of a single, undivided, multinucleated giant cell. This organization, known as " coenocytic ", is only abandoned in the production of gametes. If the organism is injured, it protects itself against the otherwise threatened loss of large amounts of cytoplasm by closing the wound with a gelatinous plug within seconds. The mechanical strength against stress is in the same order of magnitude as that of algae with multi-cell siphons. The cell wall of Penicillus does not contain any cellulose, it consists mainly of xylan . Depending on the zone, the plastids are formed as green chloroplasts or, especially in the subterranean parts, as white-colored amyloplasts (heteroplastic).

Multiplication and life cycle

The reproduction of penicillus occurs predominantly asexually (vegetatively). The individuals push forward runners known as rhizoids within the substrate, which grow upwards at some distance from the mother organism and form a new individual. According to observations in the aquarium, Penicillus capitatus can develop such a daughter organism every 6 days. The lifespan of the individual above-ground thalli is only about 1.5 to 2 months. Sexual reproduction begins with morphologically inconspicuous gametangia at the tips of branches of the capitulum, but they are noticeable in terms of color on the organism as whitish tips of the branches. The species is often separated from the sexes, individual individuals form exclusively either male microgametes or female macrogametes. The release of the gametes is presumably synchronized by environmental factors, but the trigger has not yet been identified. The male microgametes carry two flagella, the approximately 100 micrometer large female macrogametes have numerous small, similar flagella (stephanokont), which are attached to a ribbon-like tail region. After fertilization, the flagella are reabsorbed. The life cycle has not yet been followed in detail. According to previous observations, at least under certain environmental conditions, mat-like individuals consisting of branched threads develop, which only later differentiate into typical shapes. This form was mistakenly described in the Mediterranean, where it occurs frequently, as a species of its own genus, Espera mediterranea Decaisne. Under unfavorable environmental conditions, the species can remain in this Espera stage and thus reproduce, this applies to large parts of the Mediterranean. The mother organism dies after the production of gametes, the dead thallus decomposes very quickly, within 12 hours.

Distribution and ecology

The species of the genus are distributed in shallow coastal waters of tropical and subtropical seas, where they can form extensive underwater meadows on soft substrates. They occur in a water depth of up to 30 meters. They occur in corresponding latitudes almost worldwide, both in the Atlantic (including the Mediterranean) and in the Indo-Pacific. The species composition is different: three species occur in the Indo-Pacific, the rest in the Atlantic waters. The center of distribution, with most species, is the Caribbean . The most common and widespread species is Penicillus capitatus .

Like almost all bryopsidales, penicillus species are protected from phytophagous species by secondary plant substances from the class of sesquiterpenes and diterpenes , in addition to the calcified shell; the ingredients are often unstable when isolated and therefore difficult to research. The screw Elysia clarcki ( sacoglossa ) is, however, capable Penicillus and the related genus halimeda graze and to allow their chloroplasts intact. These so-called kleptoplastids not only color the snail green, but also contribute directly to its diet through continued assimilation.

The richly branched crown of Penicillus species offers numerous small crustaceans from the Amphipoda , Harpacticoida and Tanaidacea a small habitat protected from numerous predators.

Phylogeny and Systematics

The genus Penicillus comprises, depending on the opinion, about 10 to 12 valid species. According to phylogenomic investigations, the morphologically defined genera Penicillus , Udotea and Rhipocephalus are paraphyletic against each other .

species

Web links

Commons : Penicillus  - collection of images, videos and audio files

Scientific databases

Individual evidence

  1. ↑ a b c Penicillus . MD Guiry in Guiry, MD & Guiry, GM 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.
  2. ^ Gerold Wefer (1980): Carbonate production by algae Halimeda, Penicillus and Padina. Nature 285: 323-324. doi: 10.1038 / 285323a0
  3. ↑ Robert DeWreede (2006): Biomechanical Properties of Coenocytic Algae (Chlorophyta, Caulerpales). ScienceAsia 32 Supplement 1: 57-62. doi: 10.2306 / scienceasia1513-1874.2006.32 (s1) .057
  4. ^ EI Friedmann & WC Roth (1977): Development of the siphonous green alga Penicillus and the Espera state. Botanical Journal of the Linnean Society, 74: 189-214.
  5. ↑ Kenneth E. Clifton & Lisa M. Clifton (1999): The pheonology of sexual reproduction by green algae (Bryopsidales) on Caribbean coreal reefs. Journal of Phycology 35 (1): 24-34. doi: 10.1046 / j.1529-8817.1999.3510024.x
  6. ^ Mark E. Hay & William Fenical (1988): Marine plant-herbivore interactions: the ecology of chemical defense. Annual Review of Ecology and Systematics 19: 111-145.
  7. ^ Nicholas E. Curtis, Steven E. Massey, Sidney K. Pierce (2006): The symbiotic chloroplasts in the sacoglossan Elysia clarki are from several algal species. Invertebrate Biology 125 (4): 336-345. doi: 10.1111 / j.1744-7410.2006.00065.x (open access)
  8. ^ Allan W. Stoner (1985): Penicillus capitatus: an algal island for macrocrustaceans. Marine Ecology Progress Series 26: 279-287.
  9. ^ Wiebe HCF Kooistra (2006): Molecular phylogenies of Udoteaceae (Bryopsidales, Chlorophyta) reveal nonmonophyly for Udotea, Penicillus and Chlorodesmis. Phycologia 41 (5): 453-462. doi: 10.2216 / i0031-8884-41-5-453.1
  10. ↑ Heroen Verbruggen, Matt Ashworth, Steven T. LoDuca, Caroline Vlaeminck, Ellen Cocquyt, Thomas Sauvage, Frederick W. Zechman, Diane S. Littler, Mark M. Littler, Frederik Leliaert, Olivier De Clerck (2009): A multi-locus time-calibrated phylogeny of the siphonous green algae. Molecular Phylogenetics and Evolution 50: 642-653. doi: 10.1016 / j.ympev.2008.12.018