Family LIMNORIIDAE White, 1850

Limnoria indica

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Family LIMNORIIDAE White, 1850

Compiler and date details

Gary C.B. Poore, Laurie J. Cookson & Helen M. Lew Ton

Introduction

The Limnoriidae are a cosmopolitan family of marine borers from intertidal to shelf depths at salinities of more than 25 parts per thousand. Species of Paralimnoria are wood borers, those of Limnoria are either wood or algal borers, and those of Lynseia are from sea-grasses. Mature specimens are between 2 and 8.5 mm long. Limnoria species are found boring in the holdfasts of algae of the genera Macrocystis, Egregia, Laminaria, Postelsia, Eisenia (Menzies 1957), Ecklonia, Durvillaea, Lessonia, Corallina and other red algae. One species has been found in the rhizomes of the sea-grass Posidonia whereas another species, which probably does not bore, was washed from clumps of the alga Hormosira and the serpulid polychaete Galeolaria. Lynseia is an endemic genus of three species which mines the leaves of sea-grasses Heterozostera and Posidonia.

The wood borers are of major economic importance (Oliver 1962) and the most-studied species is L. tripunctata Menzies. Normally devoid of gut-inhabiting bacteria, this species can seriously attack creosote-treated softwood piling after aquiring certain bacteria in the gut (Zachary et al. 1983). L. tripunctata produces its own cellulase to utilize wood as food. Before Limnoria can bore into hardwoods the wood surface must be pre-softened by micro-organisms. Limnoria are usually found in pairs in burrows, with the female at the blind end of the tunnel (Eltringham & Hockley 1961). They can block off the burrow with the circular shield formed by the pleotelson and fifth pleonite. Limnoriids produce between 2 and 35 eggs (Menzies 1954). After the larvae emerge they bore tunnels which radiate from the parents' tunnel. Adults disperse to attack fresh timber (Eltringham & Hockley 1961). The amphipods Chelura and Corophium are often found in the disused portion of Limnoria burrows, and certain copepods and ostracods are found on the pleotelson, pleopods, or in the brood pouch.

Cookson's (1991) review of the Australasian species surpassed that of Menzies (1957). Both authors discussed the history of the family and defined the genera and species then known. Subgenera of Limnoria (Limnoria and Phycolimnoria) have been widely used, but Cookson's work has shown than the wood-boring Limnoria and algal-boring Phycolimnoria are not monophyletic groups. Several species of intermediate nature are known and subgenera are not used in this Catalogue. Bruce (1988) included the unusual genus Hadromastax in the family, but this is now placed in a family of its own. The family Lynseiidae Poore, 1987 was described on the basis of one species, but with the discovery of two more species of Lynseia its separation from Limnoriidae can no longer be justified (Cookson & Poore 1994).

Diagnosis

Body semicircular in cross-section, elongate, 3–15 times as long as wide. Head more or less spherical, freely articulating with pereonite 1. Anterior margin of pereonite 1 directed upwardly or level with body, overlapping head posteriorly. Pleonites 1–5 free. Pleotelson with lateral crests. Antennae 1 contiguous, usually with scale. Antennae 2 lateral or ventrolateral to antenna 1. Eyes lateral. Frontal lamina absent. Clypeus transversely elongated, reaching lateral margin of antenna 2 articulation. Labrum circular. Mandible with palp 3-articulate or reduced to seta; incisors acute; lacinia mobilis small; spine row present; molar process absent. Maxilliped narrow; epipod present; endite long. Pereopods ambulatory; carpus of pereopods 6 and 7 and often of others with distal comb-seta. Pereopod 1 propodus with two comb-setae posterodistally. Pereopod 7 longer than other pereopods. Pleopods flabelliferan. Uropod ventrolateral; rami terminal, oval or circular in cross-section; exopod shorter than endopod, often with corneous apex.