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Gribble – Invasive Species – Part 40

Invasive Species in USA Waterways - Part 40


Limnoria quadripunctata

The Gribble is an invasive species of small marine wood-boring isopods from the Limnoriidae family. A marine crustacean. Other names include Gribble Worm. Native to a temperate-subtropical range including the Philippines and Belize.

Invasive Species Definition

The definition of an invasive species is any species that is not native to our ecosystems and cause harm when introduced to the ecosystems. Furthermore, these may include amphibians, plants, insects, fish, fungus, bacteria and more. Impacts on the environment may cause economic loss or affect human health.

While, Invasive species tend to grow and reproduce quickly and spread aggressively with the potential to cause harm on the environment, economy or even human health. Therefore, given the label “invasive”.

Description of the Gribble


The Gribble features a small, nearly cylindrical body. While, the head region (cephalon) is compressed and ovoid with lateral eyes. Furthermore, the cephalon is distinct from the thoracic region (pereion). Therefore, enabling the head to rotate freely on the abdomen.

Two antennae are present and are equally anterior with obvious scales on the first. Meanwhile, the second antennae have five segments. Meanwhile, the left mandible incisor lacks teeth. However, is forms a projecting rasp-and-file device. Reduced uropods are present with the exopod being much shorter and bearing an apical claw.

Generally, the anterior dorsal surface of the pleotelson bears four symmetrically arranged tubercles anteriorly. With the lateral and posterior edges not lined with tubercles. The adults are 3 – 4mm long and are either pink or white in color.

Biology of the Gribble

Adults and juveniles swarm occasionally and colonize new pieces of wood. Preferring rough surfaces of relatively soft wood, infected by fungi.

Distribution of the Gribble

The native range includes the Philippines and Belize. However, they have been introduced to the North East Atlantic and North East Pacific, Australia, New Zealand and Chile.

Introduction to the USA of the Gribble

Appeared in San Francisco Bay in 1873. However, only described in 1949 and often identified as Limnoria lignorum. By 1949 it was found throughout California including La Jolla, Los Angeles-Long Beach and Humboldt Bay.

Effect on the Ecosystem and Management

A wood-boring organism that damages wooden pilings and ship hulls in warm temperate to tropical marine waters around the world. However, absent in ports where salinities drop below 20 PSU. They perforate wood by burrowing tunnels especially where waves have eroded the wood slightly.

Gribbles high oxygen requirement, limits their boring to the outer regions of wood. Therefore, part of the economic cost of these organisms is the cost the ecological damage of preventive measures including the use of resistant tropical wood and chemical treatments for marinas, docks and wooden boats to prevent damage by boarers.


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