Family NOLELLIDAE Harmer, 1915

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Family NOLELLIDAE Harmer, 1915

Compiler and date details

July 2001 - Dr Philip Bock

Nolellidae Harmer, S.F. 1915. The Polyzoa of the Siboga Expedition. Part 1. Entoprocta, Ctenostomata and Cyclostomata. Siboga-Expéditie Report 28A: 1-180 [52].

Introduction

The family Nolellidae was introduced by Harmer (1915) for Nolella stipata, a species originally described from Britain. The family is characterized by its very elongated zooids which are connected proximally by very thin zooidal extensions. However, some species assigned to Nolella exhibit peristomial budding, like Victorella. In contrast to Victorella, the embryos in Nolella are often numerous and are brooded in the coelomic cavity, usually congregating at the distal end of the fertile zooid. When mature, the larvae push out the body wall until it fractures and they are released (Harmer 1915). However, Ström (1977) has suggested that the embryos are brooded in an evagination of the body wall, as in Sundanella.

Nolella, the type genus, includes Cylindroecium, and many of the records of species assigned to both these genera, with the specific names stipata, gigantea and dilatata were regarded by Harmer (1915) as all belonging to N. stipata. However, Hayward (1985) regarded N. dilatata as distinct. Australian records of Nolella originate with Kirkpatrick's (1888) survey of species from Port Phillip, Victoria. He recorded 'Cylindroecium papuense' growing on species of Amathia. Nolella papuensis was first described from the south coast of New Guinea by Busk (1886) and later redescribed from the same region by Harmer (1915), who noted that he was not sure if the species N. stipata, N. gigantea, N. papuensis and N. dilatata were synonymous. Harmer described the brooding zooids of N. papuensis. Kirkpatrick (1888) also described in detail another species he called 'Cylindroecium altum' from Port Phillip. This had zooids 4.6 mm long, which, unlike those of N. papuensis, were budded peristomially. He reported that colonies were attached by rhizoids, and that the cuticle was covered with silt particles. Hastings (1932) reported Nolella alta from the Great Barrier Reef, and from Amoy, southern China, and noted that the zooids had 10 tentacles. Marcus (1938) figured candelabriform colonies produced by repeated peristomial budding, very like those of Kirkpatrick, from Brazil. The zooids had a maximum length of 9 mm, very like those of Aethozoon (see below), and an order of magnitude longer than those of other bryozoans. Marcus also noted the congregation of numerous embryos at the distal end of zooids. N. alta thus combines a budding pattern similar to that of Victorella with a brooding system otherwise found in Nolella. The similarity of N. alta to Anguinella was also noted by Marcus. D'Hondt (1986) described several new species of Nolella from New Caledonia.

The genus Anguinella is traditionally assigned to the Nolellidae, but could equally be placed in the Victorellidae, as colonies are formed almost entirely by peristomial budding.

The type, and only species of Anguinella, A. palmata, was first described by van Beneden (1845) and included by Hincks (1880) in his British Marine Polyzoa. It has since been described in detail by Prenant & Bobin (1956) and by Hayward (1985). A. palmata has large colonies up to 20 cms high, forming fleshy tufts with many branches. The cuticle is covered by adherent fine silt grains, and colonies are greyish to greenish-brown, and are often mistaken for algae, particularly Codium. The opacity of the exterior covering makes individual zooids difficult to distinguish. Each autozooid in the central 'stem' buds secondary and tertiary zooids peristomially. The zooids are up to 1,5 mm long, and curve inwards towards the main branch. Zooids have 10-11 tentacles. Kenozooidal rhizoids develop from the walls of the more proximal zooids and help to anchor the colony, which often becomes covered by epizoic species. A. palmata has been reported from temperate to warm waters, sometimes those of lowered salinity, from all over the world (Hayward 1985). Colonies are capable of withstanding considerable turbulence (Cook, 1985), and one population, at least, had a species-specific cleaning nudibranch associate. A. palmata was reported from New South Wales by Allen (1953), and was included as part of the New Zealand fouling fauna by Gordon & Mawatari (1992). Although, A. palmata has been recorded so often, it may be even more common but not recognized as a bryozoan. The similarity to Nolella alta (see above) is striking, although the zooids are far shorter.

The method of brooding is unknown.

Diagnosis

Colony encrusting to semi-erect, adhering by kenozooidal rhizoids. Zooids often fleshy, very elongated, cuticle covered by sand grains, separated for most of their length, connected proximally by thin extensions or budded peristomially. Embryos numerous, probably brooded in an invagination of distal body wall.