A gribble /ˈgɹɪbəl/ (or gribble worm) is any of about 56 species of marine
isopod
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...
from the family Limnoriidae. They are mostly pale white and small ( long)
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
s, although ''
Limnoria stephenseni
''Limnoria'' is a genus of isopods from the family Limnoriidae.
Species
*'' Limnoria agrostisa'' Cookson, 1991
*'' Limnoria algarum'' Menzies, 1957
*'' Limnoria andamanensis'' Rao & Ganapati, 1969
*'' Limnoria antarctica'' Pfeffer, 1887
*'' ...
'' from
subantarctic
The sub-Antarctic zone is a region in the Southern Hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° and 60° south of the Equator. The subantarctic region includes many islands ...
waters can reach .
Classification
The term "gribble" was originally assigned to the
wood-boring
The term woodboring beetle encompasses many species and families of beetles whose larval or adult forms eat and destroy wood (i.e., are xylophagous). In the woodworking industry, larval stages of some are sometimes referred to as woodworms. The t ...
species, especially the first species described from Norway by
Jens Rathke
Jens Rathke (14 November 1769 – 28 February 1855) was a Norwegian professor, scientist and zoologist. Biography
Rathke was born in Christiania (now Oslo), Norway. He was the son of Casper Elias Rathke (1729-1777) and Margaretha Madsdatter Schu ...
in 1799, ''
Limnoria lignorum
''Limnoria lignorum'', commonly known as the gribble, is a species of isopod in the family Limnoriidae. It is found in shallow water in the North Atlantic and North Pacific Ocean where it tunnels into wood and attacks and destroys submerged wood ...
''. The Limnoriidae are now known to include
seaweed
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
and
seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...
borers, as well as wood borers. Those gribbles able to bore into living marine plants are thought to have evolved from a wood (dead plant) boring species.
Ecology
Gribbles bore into wood and plant material for ingestion as food. The
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
of wood is digested, most likely with the aid of
cellulase
Cellulase (EC 3.2.1.4; systematic name 4-β-D-glucan 4-glucanohydrolase) is any of several enzymes produced chiefly by fungi, bacteria, and protozoans that catalyze cellulolysis, the decomposition of cellulose and of some related polysaccharide ...
s produced by the gribbles themselves. The most destructive species are ''Limnoria lignorum'', ''L. tripunctata'' and ''L. quadripunctata''. Due to dispersal while inhabiting wooden ships, it is uncertain where these three mentioned species originated. Limnoriidae are second only to the
Teredinidae
The shipworms are marine bivalve molluscs in the family Teredinidae: a group of saltwater clams with long, soft, naked bodies. They are notorious for boring into (and commonly eventually destroying) wood that is immersed in sea water, includin ...
in the amount of destruction caused to marine timber structures such as jetties and piers. ''L. tripunctata'' is unusually tolerant of
creosote
Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics.
Some creosote types were ...
, a preservative often used to protect timber piles, due to symbiosis with creosote-degrading bacteria. Gribbles bore the surface layers of wood, unlike the Teredinidae which attack more deeply. Their burrows are 1–2 mm diameter, may be several centimetres long, and have the burrow’s roof punctured with a series of smaller ventilation holes. Attacked wood can become spongy and friable.
Gribbles play an ecologically important role, by helping to degrade and recycle driftwood. Most seaweed boring gribbles attack
holdfasts and their activities can cause the seaweed to come adrift especially during storms. For example, ''
Limnoria segnis
''Limnoria'' is a genus of isopods from the family Limnoriidae.
Species
*'' Limnoria agrostisa'' Cookson, 1991
*'' Limnoria algarum'' Menzies, 1957
*'' Limnoria andamanensis'' Rao & Ganapati, 1969
*'' Limnoria antarctica'' Pfeffer, 1887
*'' ...
'' and ''
L. stephenseni'' inhabit the holdfasts of ''
Durvillaea antarctica
''Durvillaea antarctica'', also known as ' and ', is a large, robust species of southern bull kelp found on the coasts of Chile, southern New Zealand, and Macquarie Island.Smith, J.M.B. and Bayliss-Smith, T.P. (1998). Kelp-plucking: coastal eros ...
'' and other
southern bull-kelp and have rafted thousands of kilometres across the Southern Ocean inside of these holdfasts.
For defence, gribbles can jam themselves within their burrows using their
uropod
Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion.
Definition
Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...
s and block the tunnel with their rear disc-shaped segment, the pleotelson.
A number of crustaceans have evolved as
commensal
Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...
s with Limnoriidae. ''
Chelura'' are
amphipods
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descri ...
that inhabit the more severely attacked regions of gribble-attacked wood. ''
Donsiella'' are tiny
copepod
Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...
s that inhabit the brood pouch and body of Limnoriidae.
As a source of biofuel
It has been suggested that the enzymes used by Limnoriidae to break down wood may be useful for producing sugar from non-food
biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
, such as wood or straw, in a sustainable way. This could then be used to produce alternative fuels. "Enzymes produced by the tiny creatures are able to break down woody cellulose and turn it into energy-rich sugars meaning that gribble could convert wood and straw into liquid biofuel." One particular enzyme produced in a special organ in the body of the gribble called the
hepatopancreas
The hepatopancreas, digestive gland or midgut gland is an organ of the digestive tract of arthropods and molluscs. It provides the functions which in mammals are provided separately by the liver and pancreas, including the production of digestive ...
and secreted into its gut has recently been identified and characterized: the GH7
cellobiohydrolase, LqCel7B. This enzyme has been shown to be highly effective in a salty environment such as that in which the gribble lives.
References
Notes
Bibliography
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*
*
External links
Video of live gribbles in wood
{{Taxonbar, from=Q1940162
Isopoda
Herbivorous arthropods