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Lévi, 1952

Species Overview

Rotuloplocamia octoradiata Lévi (1952) is a very thin reddish orange crust on calcareous objects and stones. It has tiny birotule microscleres (microscopic examination). It has a relatively smooth, dense surface and in this differs somewhat from the host of red and orange crusts of the Microcionidae. It is a a southern species, originally described from West Africa but also recorded from the Atlantic coast of North Spain.

Taxonomic Description

Colour: Yellow-orange or reddish orange.
Shape, size, surface and consistency: Extremely thin, encrusting the undersurface of stones or insides of dead shells, not easily detached; several square cm in lateral expansion. Surface optically smooth, slightly hispid. Consistency firm.
Spicules: Megascleres: Ectosomal tornotes in the form of styles or subtylotes (subtylostyles with mucronate pointed end), smooth: 130-220 x 4-5 µm; large styles with strongly rugose heads and smooth curved shafts: 360-740 x 13-20 µm; short, echinating acanthostyles, with heavily rugose heads and lightly spined shafts: 120-275 x 9-16 µm; dumbell-type acanthostrongyles with swollen and rugose heads and only a few spined on the shaft: 40-120 x 8-12 µm.
Microscleres: Birotulates with 8 teeth on each umbrella: 5-12 µm.
Skeleton: (Rotuloplocamia skeleton) The acanthostrongyles form a basal, somewhat obscured isotropic reticulation. Upon it large acanthostyles are standing singly and erect, surrounded by groups of shorter acanthostyles. The ectosomal tornotes occur in dense bundles perpendicula and paratangential near the surface forming a more or less dense crust.
Ecology: Cryptic habitats in shallow water down to 30 m.
Distribution: West Africa, Atlantic coast of Spain.
Etymology: The name refers to the birotulates with 8 teeth.
Type specimen information: The type is inthe Muséum National d'Histoire Naturelle, Paris.

Remarks

There are a few discrepancies between Lévi’s (1952) and ZMA material from the Cape Verde Islands on the one hand, and the North Spain material described as Plocamiancora spec. by Solórzano et al. (1991) in the shape of the tornotes and the size of the large styles. However, the tornotes are variable in shape in the West African specimens, so these differences are considered infraspecific variation.
The species has the plocamiid skeletal structure considered by past authors as a synapomorphy (shared character) for a separate family Plocamiidae. However, the diverse spiculation of the various plocamiid forms has caused their current assignment to several unrelated Myxillina families, as well as to some Microcionidae families. The genus Rotuloplocamia is considered valid despite its monotypical status because it differs from other birotule-bearing Myxillina genera in the possession of dumbell-type acanthostrongyles forming the isotropic basal skeleton.
Source: Lévi, 1952.

Rotuloplocamia octoradiata