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60-670: A gribble /ˈgɹɪbəl/ (or gribble worm ) is any of about 56 species of marine isopod from the family Limnoriidae . They are mostly pale white and small (1–4 millimetres or 0.04–0.16 inches long) crustaceans , although Limnoria stephenseni from subantarctic waters can reach 10 mm (0.4 in). The term "gribble" was originally assigned to the wood-boring species, especially the first species described from Norway by Jens Rathke in 1799, Limnoria lignorum . The Limnoriidae are now known to include seaweed and seagrass borers, as well as wood borers. Those gribbles able to bore into living marine plants are thought to have evolved from

120-490: A nauplius , which is characterized by its use of antennae for swimming. Barnacles , a highly modified crustacean, use their antennae to attach to rocks and other surfaces. The second antennae in the burrowing Hippoidea and Corystidae have setae that interlock to form a tube or "snorkel" which funnels filtered water over the gills. Some claim insects evolved from prehistoric crustaceans, and they have secondary antennae like crustaceans, but not primary antennae. Antennae are

180-407: A ball as a defense mechanism or to conserve moisture like species in the family Armadillididae , the pillbugs. There are over 10,000 identified species of isopod worldwide, with around 4,500 species found in marine environments, mostly on the seabed, 500 species in fresh water, and another 5,000 species on land. The order is divided into eleven suborders . The fossil record of isopods dates back to

240-412: A ball when threatened, a feature that has evolved independently in different groups and also in the marine sphaeromatids . Isopods have a simple gut which lacks a midgut section; instead there are caeca connected to the back of the stomach in which absorption takes place. Food is sucked into the esophagus , a process enhanced in the blood-sucking parasitic species, and passed by peristalsis into

300-419: A host plant's taste and odor. After the desired taste and odor has been identified, the female moth will deposit her eggs onto the plant. Giant swallowtail butterflies also rely on antenna sensitivity to volatile compounds to identify host plants. It was found that females are actually more responsive with their antenna sensing, most likely because they are responsible for oviposition on the correct plant. In

360-400: A pest, endangering the fish and possibly injuring the aquarium keeper. Some members of the family Cirolanidae suck the blood of fish, and others, in the family Aegidae , consume the blood, fins, tail and flesh and can kill the fish in the process. The World Marine, Freshwater and Terrestrial Isopod Crustaceans database subdivides the order into eleven suborders: Isopods first appeared in

420-402: A post-larval stage which resembles the adult except for the absence of the last pair of pereopods. The lack of a swimming phase in the life cycle is a limiting factor in isopod dispersal , and may be responsible for the high levels of endemism in the order. As adults, isopods differ from other crustaceans in that moulting occurs in two stages known as "biphasic moulting". First they shed

480-440: A raised portion of the insect's head capsule. The socket is closed off by the membrane into which the base of the scape is set. However, the antenna does not hang free on the membrane, but pivots on a rigidly sprung projection from the rim of the torulus. That projection on which the antenna pivots is called the antennifer . The whole structure enables the insect to move the antenna as a whole by applying internal muscles connected to

540-404: A salty environment such as that in which the gribble lives. Isopoda Isopoda is an order of crustaceans . Members of this group are called isopods and include both aquatic species, and terrestrial species such as woodlice . All have rigid, segmented exoskeletons , two pairs of antennae , seven pairs of jointed limbs on the thorax , and five pairs of branching appendages on

600-467: A swelling on the oviduct close to the gonopore. Fertilisation only takes place when the eggs are shed soon after a moult, at which time a connection is established between the semen receptacle and the oviduct. The eggs, which may number up to several hundred, are brooded by the female in the marsupium , a chamber formed by flat plates known as oostegites under the thorax. This is filled with water even in terrestrial species. The eggs hatch as mancae ,

660-462: A unit, in spite of being articulated. However, some funicles are complex and very mobile. For example, the Scarabaeidae have lamellate antennae that can be folded tightly for safety or spread openly for detecting odours or pheromones . The insect manages such actions by changes in blood pressure, by which it exploits elasticity in walls and membranes in the funicles, which are in effect erectile. In

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720-456: A waxy cuticle, they need to conserve water, often living in a humid environment and sheltering under stones, bark, debris or leaf litter . Desert species, like Hemilepistus reaumuri, are usually nocturnal, spending the day in a burrow and emerging at night. Moisture is achieved through food sources or by drinking, and some species can form their paired uropodal appendages into a tube and funnel water from dewdrops onto their pleopods. In many taxa,

780-457: A wood (dead plant) boring species. Gribbles bore into wood and plant material for ingestion as food. The cellulose of wood is digested, most likely with the aid of cellulases 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

840-430: Is believed to be the first instance discovered of a parasite functionally replacing a host structure in animals. In most species, the sexes are separate and there is little sexual dimorphism , but a few species are hermaphroditic and some parasitic forms show large differences between the sexes. Some Cymothoidans are protandrous hermaphrodites , starting life as males and later changing sex, and some Anthuroideans are

900-423: Is considered segmented if each of the annuli is separate from those around it and has individual muscle attachments. Flagellate antennae, on the other hand, have muscle attachments only around the base, acting as a hinge for the flagellum —a flexible string of annuli with no muscle attachment. There are several notable non-sensory uses of antennae in crustaceans. Many crustaceans have a mobile larval stage called

960-550: Is digested by enzymes secreted in the caeca. Limnoria lignorum , for example, bores into wood and additionally feeds on the mycelia of fungi attacking the timber, thus increasing the nitrogen in its diet. Land-based wood-borers mostly house symbiotic bacteria in the hindgut which aid in digesting cellulose. There are numerous adaptations to this simple gut, but these are mostly correlated with diet rather than by taxonomic group. Parasitic species are mostly external parasites of fish or crustaceans and feed on blood. The larvae of

1020-436: Is fused with the first segment of the thorax to form the cephalon . There are two pairs of unbranched antennae , the first pair being vestigial in land-dwelling species. The eyes are compound and unstalked and the mouthparts include a pair of maxillipeds and a pair of mandibles (jaws) with palps (segmented appendages with sensory functions) and lacinia mobilis (spine-like movable appendages). The seven free segments of

1080-591: Is the primary means of locomotion, and some species bore into the seabed, the ground or timber structures. Some members of the families Sphaeromatidae , Idoteidae and Munnopsidae are able to swim pretty well, and have their front three pairs of pleopods modified for this purpose, with their respiratory structures limited to the hind pleopods. Most terrestrial species are slow-moving and conceal themselves under objects or hide in crevices or under bark. The semi-terrestrial sea slaters ( Ligia spp.) can run rapidly on land and many terrestrial species can roll themselves into

1140-746: The Carboniferous period (in the Pennsylvanian epoch ), at least 300 million years ago, when isopods lived in shallow seas. The name Isopoda is derived from the Greek roots iso- (from ἴσος ísos , meaning "equal") and -pod (from ποδ- , the stem of πούς poús , meaning "foot"). Classified within the arthropods , isopods have a chitinous exoskeleton and jointed limbs. Isopods are typically flattened dorsoventrally (broader than they are deep), although many species deviate from this rule, particularly parasitic forms, and those living in

1200-473: The Coleoptera and Hymenoptera. They are important for insects like ants that follow scent trails, for bees and wasps that need to "sniff" the flowers that they visit, and for beetles such as Scarabaeidae and Curculionidae that need to fold their antennae away when they self-protectively fold up all their limbs in defensive attitudes. Because the funicle is without intrinsic muscles, it generally must move as

1260-556: The Gnathiidae family and adult cymothoidids have piercing and sucking mouthparts and clawed limbs adapted for clinging onto their hosts . In general, isopod parasites have diverse lifestyles and include Cancricepon elegans , found in the gill chambers of crabs ; Athelges tenuicaudis , attached to the abdomen of hermit crabs; Crinoniscus equitans living inside the barnacle Balanus perforatus ; cyproniscids , living inside ostracods and free-living isopods; bopyrids , living in

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1320-576: The Hexapoda , both Collembola and Diplura have antenna, but Protura do not. Antennal fibrillae play an important role in Culex pipiens mating practices. The erection of these fibrillae is considered to be the first stage in reproduction. These fibrillae serve different functions across the sexes. As antennal fibrillae are used by female C. pipiens to locate hosts to feed on, male C. pipiens utilize them to locate female mates. The three basic segments of

1380-544: The Teredinidae in the amount of destruction caused to marine timber structures such as jetties and piers. L. tripunctata is unusually tolerant of creosote , 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

1440-611: The abdomen that are used in respiration . Females brood their young in a pouch under their thorax called the marsupium . Isopods have various feeding methods: some eat dead or decaying plant and animal matter, others are grazers or filter feeders , a few are predators , and some are internal or external parasites , mostly of fish. Aquatic species mostly live on the seabed or the bottom of freshwater bodies of water , but some taxa can swim for short distance. Terrestrial forms move around by crawling and tend to be found in cool, moist places. Some species are able to roll themselves into

1500-442: The antennal lobe in the brain . From there, neurons in the antennal lobes connect to mushroom bodies that identify the odour. The sum of the electrical potentials of the antennae to a given odour can be measured using an electroantennogram . In the monarch butterfly , antennae are necessary for proper time-compensated solar compass orientation during migration. Antennal clocks exist in monarchs, and they are likely to provide

1560-907: The chelicerates and proturans , which have none, all non-crustacean arthropods have a single pair of antennae. Crustaceans bear two pairs of antennae. The pair attached to the first segment of the head are called primary antennae or antennules . This pair is generally uniramous, but is biramous in crabs and lobsters and remipedes . The pair attached to the second segment are called secondary antennae or simply antennae . The second antennae are plesiomorphically biramous, but many species later evolved uniramous pairs. The second antennae may be significantly reduced (e.g. remipedes) or apparently absent (e.g. barnacles ). The subdivisions of crustacean antennae have many names, including flagellomeres (a shared term with insects), annuli, articles, and segments. The terminal ends of crustacean antennae have two major categorizations: segmented and flagellate. An antenna

1620-573: The exoskeleton from the posterior part of their body and later shed the anterior part. The giant Antarctic isopod Glyptonotus antarcticus is an exception, and moults in a single process. The majority of crustaceans are aquatic and the isopods are one of the few groups of which some members now live on land. The only other crustaceans which include a small number of terrestrial species are amphipods (like sandhoppers ) and decapods (crabs, shrimp, etc.). Terrestrial isopods play an important role in many tropical and temperate ecosystems by aiding in

1680-515: The fossil record during the Carboniferous period of the Paleozoic some 300 million years ago. They were primitive, short-tailed members of the suborder Phreatoicidea . At that time, Phreatoicideans were marine organisms with a cosmopolitan distribution. Nowadays, the members of this formerly widespread suborder form relic populations in freshwater environments in South Africa, India and Oceania,

1740-435: The abdominal segments, starting with the sixth segment, is fused to the telson (terminal section) to form a rigid pleotelson . The first five abdominal segments each bear a pair of biramous (branching in two) pleopods ( lamellar structures which serve the function of gas exchange, and in aquatic species serve as gills and propulsion), and the last segment bears a pair of biramous uropods (posterior limbs). In males,

1800-479: The adult. Many crustaceans, for example, have free-swimming larvae that use their antennae for swimming. Antennae can also locate other group members if the insect lives in a group, like the ant . The common ancestor of all arthropods likely had one pair of uniramous (unbranched) antenna-like structures, followed by one or more pairs of biramous (having two major branches) leg-like structures, as seen in some modern crustaceans and fossil trilobites . Except for

1860-405: 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 and L. stephenseni inhabit

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1920-431: The coxae (first segments) are fused to the tergites (dorsal plates) to form epimera (side plates). In mature females, some or all of the limbs have appendages known as oostegites which fold underneath the thorax and form a brood chamber for the eggs. In males, the gonopores (genital openings) are on the ventral surface of segment eight and in the females, they are in a similar position on segment six. One or more of

1980-597: The crepuscular hawk moth ( Manduca sexta ), antennae aid in flight stabilization. Similar to halteres in Dipteran insects, the antennae transmit coriolis forces through the Johnston's organ that can then be used for corrective behavior. A series of low-light, flight stability studies in which moths with flagellae amputated near the pedicel showed significantly decreased flight stability over those with intact antennae. To determine whether there may be other antennal sensory inputs,

2040-547: The decomposition of plant material through mechanical and chemical means, and by enhancing the activity of microbes. Macro-detritivores, including terrestrial isopods, are absent from arctic and sub-arctic regions, but have the potential to expand their range with increased temperatures in high latitudes. The woodlice, suborder Oniscidea , are the most successful group of terrestrial crustaceans and show various adaptations for life on land. They are subject to evaporation, especially from their ventral area, and as they do not have

2100-423: The deep sea or in ground water habitats . Their colour may vary, from grey to white, or in some cases red, green, or brown. Isopods vary in size, ranging from some Microcerberidae species of just .3 millimetres (0.012 in) to the deep sea giant isopod Bathynomus spp. of nearly 50 cm (20 in). Giant isopods lack an obvious carapace (shell), which is reduced to a "cephalic shield" covering only

2160-409: The exact nature of what they sense and how they sense it is not the same in all groups. Functions may variously include sensing touch , air motion, heat, vibration (sound), and especially smell or taste . Antennae are sometimes modified for other purposes, such as mating, brooding, swimming, and even anchoring the arthropod to a substrate . Larval arthropods have antennae that differ from those of

2220-521: The families Ligiidae and Tylidae , commonly known as rock lice or sea slaters, are the least specialised of the woodlice for life on land. They inhabit the splash zone on rocky shores, jetties and pilings, may hide under debris washed up on the shore and can swim if immersed in water. Antenna (biology) Antennae are connected to the first one or two segments of the arthropod head. They vary widely in form but are always made of one or more jointed segments. While they are typically sensory organs ,

2280-452: The flagellum. Such groups include the Symphyla , Collembola and Diplura . In many true insects, especially the more primitive groups such as Thysanura and Blattodea , the flagellum partly or entirely consists of a flexibly connected string of small ring-shaped annuli . The annuli are not true flagellomeres, and in a given insect species the number of annuli generally is not as consistent as

2340-512: The funicle is taken to comprise the segments between the club and the pedicel. Quite commonly the funicle beyond the pedicel is quite complex in Endopterygota such as beetles, moths and Hymenoptera , and one common adaptation is the ability to fold the antenna in the middle, at the joint between the pedicel and the flagellum. This gives an effect like a "knee bend", and such an antenna is said to be geniculate . Geniculate antennae are common in

2400-450: The gill chambers or on the carapace of shrimps and crabs and causing a characteristic bulge which is even recognisable in some fossil crustaceans; and entoniscidae living inside some species of crab and shrimp. Cymothoa exigua is a parasite of the spotted rose snapper Lutjanus guttatus in the Gulf of California ; it causes the tongue of the fish to atrophy and takes its place in what

2460-545: The greatest number of species being in Tasmania . Other primitive, short-tailed suborders include Asellota , Microcerberidea , Calabozoidea and the terrestrial Oniscidea . The short-tailed isopods have a short pleotelson and terminal, stylus-like uropods and have a sedentary lifestyle on or under the sediment on the seabed. The long-tailed isopods have a long pleotelson and broad lateral uropods which can be used in swimming. They are much more active and can launch themselves off

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2520-516: The groups with more uniform antennae (for example: millipedes ), all segments are called antennomeres . Some groups have a simple or variously modified apical or subapical bristle called an arista (this may be especially well-developed in various Diptera ). Olfactory receptors on the antennae bind to free-floating molecules, such as water vapour , and odours including pheromones . The neurons that possess these receptors signal this binding by sending action potentials down their axons to

2580-524: The head. This means that the gill -like structures, which in other related groups are protected by the carapace, are instead found on specialised limbs on the abdomen. The dorsal (upper) surface of the animal is covered by a series of overlapping, articulated plates which give protection while also providing flexibility. The isopod body plan consists of a head (cephalon), a thorax (pereon) with seven segments (pereonites), and an abdomen (pleon) with six segments (pleonites), some of which may be fused. The head

2640-497: The holdfasts of Durvillaea antarctica 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 uropods and block the tunnel with their rear disc-shaped segment, the pleotelson. A number of crustaceans have evolved as commensals with Limnoriidae. Chelura are amphipods that inhabit

2700-533: The long-tailed forms may also have provided competition that helped force the short-tailed forms into refugia . The latter are now restricted to environments such as the deep sea, freshwater, groundwater and dry land. Isopods in the suborder Asellota are by far the most species-rich group of deep sea isopods. Unlike the amphipods , marine and freshwater isopods are entirely benthic . This gives them little chance to disperse to new regions and may explain why so many species are endemic to restricted ranges. Crawling

2760-407: The more severely attacked regions of gribble-attacked wood. Donsiella are tiny copepods that inhabit the brood pouch and body of Limnoriidae. It has been suggested that the enzymes used by Limnoriidae to break down wood may be useful for producing sugar from non-food biomass , such as wood or straw, in a sustainable way. This could then be used to produce alternative fuels. "Enzymes produced by

2820-421: The number of flagellomeres in most species. In many beetles and in the chalcidoid wasps , the apical flagellomeres form a club shape, called the clava . The collective term for the segments between the club and the antennal base is the funicle ; traditionally in describing beetle anatomy, the term "funicle" refers to the segments between the club and the scape . However, traditionally in working on wasps

2880-403: The presence of a special chamber under the thorax for brooding eggs. They have a cosmopolitan distribution and over 10,000 species of isopod, classified into 11 suborders, have been described worldwide. Around 4,500 species are found in marine environments, mostly on the sea floor. About 500 species are found in fresh water and another 5,000 species are the terrestrial woodlice , which form

2940-414: The primary olfactory sensors of insects and are accordingly well-equipped with a wide variety of sensilla (singular: sensillum ). Paired, mobile, and segmented, they are located between the eyes on the forehead. Embryologically, they represent the appendages of the second head segment. All insects have antennae, however they may be greatly reduced in the larval forms. Amongst the non-insect classes of

3000-477: The primary timing mechanism for sun compass orientation. In the African cotton leafworm , antennae have an important function in signaling courtship. Specifically, antennae are required for males to answer the female mating call. Although females do not require antennae for mating, a mating that resulted from a female without antennae was abnormal. In the diamondback moth , antennae serve to gather information about

3060-409: The respiratory structures on the endopods are internal, with a spiracle and pseudotrachaea, which resemble lungs. In others, the endopod is folded inside the adjoining exopod (outer branch of the pleopod). Both these arrangements help to prevent evaporation from the respiratory surfaces. Many species can roll themselves into a ball, a behaviour used in defense that also conserves moisture. Members of

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3120-406: The reverse, being protogynous hermaphrodites that are born female. Some Gnathiidans males are sessile and live with a group of females. Males have a pair of penises, which may be fused in some species. The sperm is transferred to the female by the modified second pleopod which receives it from the penis and which is then inserted into a female gonopore . The sperm is stored in a special receptacle,

3180-514: The scape. The pedicel is flexibly connected to the distal end of the scape and its movements in turn can be controlled by muscular connections between the scape and pedicel. The number of flagellomeres can vary greatly between insect species, and often is of diagnostic importance. True flagellomeres are connected by membranous linkage that permits movement, though the flagellum of "true" insects does not have any intrinsic muscles. Some other Arthropoda do however have intrinsic muscles throughout

3240-433: The seabed and swim for short distances. The more advanced long-tailed isopods are mostly endemic to the southern hemisphere and may have radiated on the ancient supercontinent of Gondwana soon after it broke away from Laurasia 200 million years ago. The short-tailed forms may have been driven from the shallow seas in which they lived by increased predatory pressure from marine fish, their main predators. The development of

3300-401: The second pair of pleopods, and sometimes also the first, are modified for use in transferring sperm . The endopods (inner branches of the pleopods) are modified into structures with thin, permeable cuticles (flexible outer coverings) which act as gills for gas exchange . In some terrestrial isopods, these resemble lungs . Isopods belong to the larger group Peracarida , which are united by

3360-912: The stomach, where the material is processed and filtered. The structure of the stomach varies, but in many species there is a dorsal groove into which indigestible material is channelled and a ventral part connected to the caeca where intracellular digestion and absorption take place. Indigestible material passes on through the hindgut and is eliminated through the anus , which is on the pleotelson. Isopods are detritivores , browsers , carnivores (including predators and scavengers ), parasites, and filter feeders , and may occupy one or more of these feeding niches. Only aquatic and marine species are known to be parasites or filter feeders. Some exhibit coprophagia and will also consume their own fecal pellets. Terrestrial species are in general herbivorous, with woodlice feeding on moss, bark, algae, fungi and decaying material. In marine isopods that feed on wood, cellulose

3420-653: The suborder Oniscidea. In the deep sea, members of the suborder Asellota predominate, to the near exclusion of all other isopods, having undergone a large adaptive radiation in that environment. The largest isopod is in the genus Bathynomus and some large species are fished commercially for human food in Mexico , Japan and Hawaii . Some isopod groups have evolved a parasitic lifestyle, particularly as external parasites of fish. They can damage or kill their hosts and can cause significant economic loss to commercial fisheries. In reef aquariums , parasitic isopods can become

3480-431: The thorax each bear a pair of unbranched pereopods (limbs). In most species these are used for locomotion and are of much the same size, morphology and orientation, giving the order its name "Isopoda", from the Greek equal foot . In a few species, the front pair are modified into gnathopods with clawed, gripping terminal segments. The pereopods are not used in respiration, as are the equivalent limbs in amphipods , but

3540-483: 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 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

3600-459: The typical insect antenna are the scape or scapus (base), the pedicel or pedicellus (stem), and finally the flagellum , which often comprises many units known as flagellomeres . The pedicel (the second segment) contains the Johnston's organ which is a collection of sensory cells. The scape is mounted in a socket in a more or less ring-shaped sclerotised region called the torulus , often

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