Penicillus Lamarck, 1813

Lectotype species: Penicillus capitatus Lamarck

Original publication: Lamarck, [J.B.P.A.] de (1813). Sur les polypiers empâtés. Annales du Muséum d'Histoire Naturelle, Paris 20: 294-312, 370-386, 432-458.

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Type designated in: Kützing, F.T. (1841). Ueber die "Polypieres calcifères" des Lamouroux. In: Zu der öffentlichen Prüfung sämmtlicher Classen der Realschule zu Nordhausen ... 1841. (Fischer, K.C.F. Eds), pp. [3]-34. Nordhausen: Realschule.

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Description: Thallus calcified, erect to about 15 cm., consisting of 1) globulose, subglobulose to pyriform capitulum (brush) of numerous, loose siphons, 2) stalk to about 10 cm. long, and 3) large bulbous holdfast of fine siphons with adhering sand. Capitulum may appear to sit atop stalk, or taper into it. Growth is determinate, with little to no further development of brush once it matures. Siphon walls are composed principally of b-1,3 xylan rather than cellulose. Capitulum is produced by successive di- (tri)-chotomies of siphons occurring in different planes; in one species capitular siphons are regularly constricted. In the stalk longitudinally oriented siphons delimit, by development of radial branches, a core of medullary siphons and a simple cortex. Genus heteroplastic, hence chloroplasts with and without starch, and amyloplasts are present. Concentric lamellar systems (dome-shaped bodies) occur in plastids, and nuclei have microbodies associated with them. Biomineralization occurs by deposition of aragonitic calcium carbonate in sheath surrounding siphons of stalk and capitulum. In P. capitatus, % CaCO3 dry weight per sample ranges from ca. 7.5 in a small young thallus to 47-56 in mature ones. Asexual reproduction is by production of new thalli at ends of siphonous outgrowths from holdfast. In aquaria, new Penicillus capitatus Lamarck thalli develop in about 6 days; turnover times are about 1.5-2 months. Sexual reproduction is by biflagellated gametes released from apices of relatively unspecialized gametangia with onset of light regime. Gametangia are uncalcified extensions of capitular siphons, and appear as a distinctive fuzz or halo fringing capitulum. Septa appear to be absent, based on 2 sets of observations. Genus holocarpic, i.e. contents of siphons released into gametangia during their formation, with thallus dying after sexual reproduction. The complete life cycle has not been followed, but includes development, under certain conditions, of an espera phase composed of erect, loose, dichotomously branched fine siphons or at times of a basal mat of aggregated siphons, and relatively delicate branching rhizoids. In the northern part of the Mediterranean the espera phase is reported present throughout the year, whereas the capitular form appears at the end of the summer. Espera phases also occur in the Caribbean, and in culture. The epithet espera formerly was assigned to Espera mediterranea, now a synonym for P. mediterraneus.

Information contributed by: L. Hillis. The most recent alteration to this page was made on 2022-02-28 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Gender: This genus name is currently treated as masculine.

Comments: Geographical distribution is tropical to somewhat subtropical, with vertical range to at least -30m. The genus forms extensive meadows in many sandy, relatively shallow regions of the Caribbean where it achieves its greatest species diversity, and is an important contributor of carbonate muds to reef environments. A budget based on low densities of Penicillus calculated that it contributed between 3-25 g carbonate m-2 yr-1 to the muds of south Florida. The genus also occurs in the Mediterranean and Indo-Pacific

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 28 February 2022. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 27 March 2023

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