Amphiroa beauvoisii

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Plantae · Phylum: Rhodophyta · Class: Florideophyceae · Order: Corallinales · Family: Lithophyllaceae · Genus: Amphiroa.

Accepted name: Amphiroa beauvoisii · Authority: J.V.Lamouroux, 1816 · Taxonomic status: accepted · AphiaID: 145097.

Synonyms and superseded combinations recorded for this taxon: Amphiroa algeriensis Kützing, 1857; Amphiroa belvisii J.V.Lamouroux, 1824; Amphiroa complanata Kützing, 1843; Amphiroa drouetii E.Y.Dawson, 1953; Amphiroa dubia Kützing, 1858; Amphiroa franciscana var. robusta E.Y.Dawson, 1953; Amphiroa linearis Kützing, 1858; Amphiroa mexicana W.R.Taylor, 1945; Amphiroa parthenopea Zanardini, 1874; Amphiroa peninsularis W.R.Taylor, 1945; Amphiroa polysona Montagne, 1849; Amphiroa polyzona Montagne, 1846; Amphiroa pustulata Martens, 1836; Amphiroa zonata Yendo, 1902.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=145097 (CC BY 4.0). Accessed 2026-09-23.

Biology and life history (SeaLifeBase)

Measured values published by SeaLifeBase for Amphiroa beauvoisii. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Habitat zone: sessile.

SeaLifeBase notes: In shallow waters on hard substrates (Ref. 83908). Subtidal (>10m) (Ref. 116144).

Source: SeaLifeBase species summary (SpecCode 112301) — https://www.sealifebase.se/summary/Amphiroa-beauvoisii.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.

Distribution and occurrence records (GBIF)

2,099 georeferenced occurrence records for Amphiroa beauvoisii are published through GBIF from 41 countries or marine areas. The map above plots 195 distinct locations from a sample of 2,099 records, omitting 124 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: United States of America (650); Mexico (618); Spain (221); Brazil (122); Japan (113).

The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.

Source: GBIF Occurrence Search (taxonKey 5276511) — https://www.gbif.org/occurrence/search?taxon_key=5276511&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=145097 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-23.

Description and natural history (Wikipedia)

Plants of Amphiroa beauvoisii grow on the surface of rocks, attached on their undersides by a calcified and crustose base. From this base, erect axes grow up to 85 mm long. The axes are made up of alternating segments of calcified sections called intergenicula and non-calcified sections called genicula. They branch out in a fan-like plane which is about 30 mm tall, usually split into two distinct branches, but rarely split into three or four.

The branches usually grow from the sections of intergenicula. These intergenicula are usually flat, but can be slightly more circular near the base. They are normally about the same width regardless of where they are on the organism, and measure 3-6.5 mm long, 1-3.5 mm wide, and 300-400 mm thick. However, they are sometimes wider towards their ends than at the base. In the core of the organism, there are filaments which consist of one to four arched rows of larger cells which are 45–85 micrometers (μm) long. These rows alternate with a single row of shorter cells which is 6–40 μm long. In the periphery, these filaments are not arranged in rows.thumb|Fig. 1 shows a portion of the branches, without the base, of A. beauvoisii, under the synonym A. peninsularis.

The genicula typically are found where the branches split, or within 2 mm of the split in the outward direction. The filaments associated with the genicula remain calcified, even though the genicula themselves are not. This leads to these calcified filaments eventually cracking and falling off the organism, though they sometimes leave calcified spurs around the genicula. Mature sections of genicula are made up of at least five rows of thick-walled cells. The transition from genicula to intergenicula occurs within these rows of cells, transitioning from one to the next between layers.

The conceptacles, which contain the reproductive sporangia, are made up of a single pore. They are found scattered across the surface of the periphery of the intergenicula, protruding above the rest of the surface. Each conceptacle is 220–330 μm wide and protrudes 85–140 μm above the surface. They are surrounded by a rick of block-like cells, which sometimes eventually shrink, leading to a moat-like depression around the raised conceptacle. There are several types of sporangia found within the conceptacle. The tetrasporangia are formed around a central column of long sterile cells, and are found in conceptacles with more or less flat floors. They are found in groups of four per conceptacle, separated into their own zones. The carposporangial conceptacles have a warty surface and are more oblong, and the carposporangia themselves have superficial gonimoblast filaments.

When viewed under a scanning electron microscope, the outlines of cells on the surface of the intergenicula are clear. They consist of calcified ridges 3–9 μm wide which split to form two narrower ridges at the middle lamella. There are concavities 5–14 μm wide on the surface layer of the thallus which are covered in cup-like formations that are calcified, lip-like openings. On the flanks of the apices of the branches there are ridges which surround the apices or make arched lines across the flat side of the compressed branches. These ridges sometimes take the form of simple bands or randomly organized raised cells, while in other places they are made up of complexly overlapping layers of cells. They are harder to see the further away from the point of attachment they are, and on older intergenicula they disappear completely.

Amphiroa beauvoisii is very similar in appearance to several other species in the genus Amphiroa, including A. anceps, A. gracilis, and A. klochkovana. It can be differentiated from A. gracilis and A. klochkovana by its intergenicula, which are almost all compressed or flat, and its genicula, which do not include decalcified cells from the peripheral region. It differs from A. anceps in its pore canals, in that the top of its canals are surrounded by a ring of large cells, while those of A. anceps are not.

Jean Vincent Lamouroux provided the original description for Amphiroa beauvoisii in 1816, when he described it in his book Histoire des Polypiers Coralligènes Flexibles, Vulgairement Nommés Zoophytes. He gave the specific epithet "beauvoisii" to honor Palisot de Beauvois, an 18th-century French entomologist and biologist.thumb|217x217px|Figs. 5 and 6 show specimens of A. beauvoisii from the type collection under the synonym A. drouetii.

The holotype of the species was collected from a type locality called the "Côtes du Portugal" (the coast of Portugal) by an unknown collector and was donated to the Lamouroux herbarium by de Beauvois, where it remains as of 2013. The holotype specimen consists of part of a single branched axis with calcified intergenicula and uncalcified genicula, as well as eight fragmentary parts of the same specimen, some of which have genicula.

While Amphiroa beauvoisii does not have any homotypic synonyms, or officially invalid nomenclature, it does have several illegitimate names. Some of these are simply superfluous, while others are misapplied to A. beauvoisii. In 1824, Lamoroux introduced the named Amphiroa belvisii; however, he discussed A. beauvoisii as a synonym in his description, thus making A. belvisii an illegitimate and superfluous name.

Several specimens of A. beauvoisii have been incorrectly described as representing other species of Amphiroa. At several times, it was misidentified as A. anceps, which were included in records of the species as recently as 1993. William Henry Harvey reported A. beauvoisii as occurring in New South Wales, but these reports were based on misidentified specimens which were actually A. ephedraea.

A list of heterotypic synonyms according to Adele Harvey et al.

Later studies revealed A. exilis to be a distinct species from A. beauvoisii, with consistent characteristics being observed between the syntype and other Australian specimens of A. exilis. While its own species, A. exilis is still very closely related in appearance to A. beauvoisii.

Amphiroa beauvoisii is one of the most widely distributed species in the genus Amphiroa, found primarily in tropical and subtropical climates. It has been recorded from the Mediterranean, the Indian Ocean, the Gulf of California, the Caribbean, and the South African coast. More recently, in 2009, it was found in temperate waters along the southwest, south, and southeast Australian coasts. However, it is possible that some of the individuals collected from the southwest coast were actually misidentified A. anceps specimens.

Source: Wikipedia: Amphiroa beauvoisii — https://en.wikipedia.org/wiki/Amphiroa_beauvoisii (CC BY-SA 4.0). Accessed 2026-09-23.

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