("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Ferenţi, et al., 2013; Giraud, et al., 2013; Karasawa, et al., 2012; Moriyama and Migita, 2004; Saska, 2008; Wright and O'Donnell, 2010), the common pillbug, is native to the edge of the Mediterranean and has been introduced to nearly all worldwide terrestrial landmasses, with particularly dense populations in temperate climates. There are significant populations throughout the United States, and it is also found in Madagascar, Australia, South Africa, and India, among many other areas. has also been extensively studied and collected in Japan, France, Canada, central Bohemia, the Czech Republic, and shorelines of western Romania.
Common pillbugs can be found under pieces of natural debris such as stones or logs in forests, and in the soil of fields, gardens, or hedgerows. Exposed large-particle soil (as found in agricultural cultivation sites or greenhouses) is more desirable than finer soils, as the former allows for increased water retention, easier burrowing, and increased relative humidity. Human domestic waste such as cardboard or old rags provide suitable habitats as well. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Karasawa, et al., 2012; Robinson, et al., 2011; Wright and O'Donnell, 2010)
Populations have been maintained successfully under stable laboratory conditions such as daily fluorescent illumination exposure ranging from six to ten hours a day, temperatures between 20 to 25°C, and combinations of damp soil and deciduous leaf litter with 100% humidity. (Beauché and Richard, 2013; Robinson, et al., 2011; Wright and O'Donnell, 2010)
Like all isopods,is oval-shaped and moderately flattened along its dorsal plane. Isopods have a cephalic shield (incompletely fused carapace) that is less durable than the fully fused carapace of other crustaceans. They have three tagmata: the head, which bears their cephalon (fused maxillipeds), the pereon (thorax), and the pleon (abdomen).
Isopod heads have unstalked eyes, unlike the compound eyes of most crustaceans, as well as one pair of antennae that bear setae. A secondary pair of smaller antennae is present but vestigial and serves no known biological purpose. The pereon is divided into seven somites (divisions), each of which has a pair of pereopods (short walking legs) protruding from it. The second through fifth ventral somite plates form the female's marsupium. Isopods primarily acquire oxygen via a thickened cuticle composed of a fibrous matrix of calcium carbonate that allows for both gas diffusion and water conservation. The pleon supports two pairs of oval-shaped respiratory structures called pleopods. They are located on the first two ventral segments of the pleon, and are hypothesized to have once been a pair of appendages. The pleopods trap air with sponge-like structures called pseudotracheae, giving them a white appearance. This is not to be confused with the white dorsal calcium carbonate plates formed during the pre-ecdysis stage of molting. The pleon also supports several tail projections, which transport water to the mouth of the isopod. Like most other crustaceans, isopods have flattened plate-like uropods (flattened appendages used for movement) and a telson (rigid structure used for backwards thrust) which are fused to form a posterior tail fan.
eggs are thin-walled and possess a yolk. After release from the oviduct, they are stored in the marsupium, a fluid-filled pouch present in reproducing females. Eggs are enclosed in both an inner vitelline membrane (composed of protein fibers and species-specific sperm receptors) and an outer chorion. The chorion is shed as a protein envelope when the egg's embryo has consumed half the original yolk. Within the embryo is a poorly understood 'dorsal organ' sensory structure common to many crustaceans. This structure is hypothesized to regulate ion and acid exchange for the developing embryo.
Egg size increases with the size of the mother. When the yolk is fully consumed, the dorsal organ atrophies and the embryo undergoes blastokinesis. After one to two days, the vitelline membrane is shed and the manca hatches. Only half of the eggs produced result in fully developed mancas. After three to four days, the mancas crawl out of the marsupium. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Wright and O'Donnell, 2010)
Mating is brief, completed within a few seconds, and synchronized with the beginning of the female's parturial molting cycle. Mating occurs as ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Bousfield and Conlan, 2013; Wright and O'Donnell, 2010; Ziegler and Suzuki, 2011)males climb onto the backs of females, bend their pleon downwards, and use their first pair of pleopods to transfer sperm to the female's ventral gonopores. Within the oviduct, the sperm are immobilized within an epicuticular envelope bundle. Bundles from each mating incident form rings within the oviduct, so that muscle cells around the oviduct can pressurize the bundles to release the immobilized spermatozoa onto oocytes that pass through these rings during oviposition. Sperm from one mating incident can be stored in this manner for an entire year for use in subsequent broods, with older sperm bundles taking precedence over more recent genetic material when broods are laid. After mating, female individuals exhibit a 'refractory period' during which further male mating attempts are rejected.
Forward movement can be initiated from weak ground vibrations or forces that reach the body. This response is considered an escape mechanism from potential predators. While moving, (Moriyama and Migita, 2004; Řezáč and Pekár, 2007)exhibits a behavior termed ‘turn alternation’, in which they invariably alternate between gradual left and right turns to move indirectly forward in a straight line until encountering an obstruction. It is hypothesized that turn alternation results from being placed in an unfamiliar environment in which potential hazards or resources are unknown. Water is a common obstruction or inhibitory structure to movement, as they cannot swim.
It has been suggested that (Robinson, et al., 2011)practices a 'priming' method of habitat selection in which juveniles leave their natal home range in search of habitats more desirable than those they were born into. If they fail to locate a more desirable habitat after a yet-undetermined time threshold, they will return to their natal habitat, presumably to decrease the survival risks involved with lengthy, long-distance movements.
This species has limited abilities of sight, smell, and touch, provided through ommatidia, esthetascs and tactile setae, respectively. Each small, non-stalked eye ofcontains a complex of ommatidia, linear structures which capture light through photoreceptors. Vision is limited to the detection of the presence or absence of light, so they generally have poor visual acuity. Esthetascs (olfactory hairs) are used to locate food and recognize other crustaceans and their sexual states. Tactile setae are used to detect objects and are found on their antennae, mouthparts, and some pleopods.
Chemical sensing, particularly how the antennae handle air-borne 'aggregate pheromone' chemicals, is likely this species' most important perceptive tool. The aggregate pheromone has many specific functions, including desiccation prevention, body growth rate acceleration, and metabolic rate reduction, but it may be used primarily as a way of locating conspecifics. The aggregate pheromone is secreted by digestive tissues, evacuated in excrement, and found in subtle traces both on the outer shell and within 'marking trails' that are produced as the individual moves through its habitat. These marking trails can be detected by the antennae of conspecifics, and allow (Beauché and Richard, 2013; Bousfield and Conlan, 2013; Moriyama, 2004; Robinson, et al., 2011)to locate one another purely through this chemical sensing technique. This pheromone also signifies the desirability of a habitat. If an individual enters a new habitat and senses the presence of aggregate pheromone in feces, molt fragments, or the marking trails, it would indicate to the individual that other members of its species are successfully surviving in that habitat. Aggregate pheromone concentration varies with humidity, but it is always highest during mating seasons. This has caused the pheromone to be hypothesized to serve as a potential mate-finding tool, or as an aid in synchronization of female molting cycles.
Terrestrial isopods like Acer platanoides (Norway maple), Salix fragilis (brittle willow), Quercus robur (English oak), and dried lime leaves (Tilia sp.). ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Le Clec’h, et al., 2013; Saska, 2008; Řezáč and Pekár, 2007)are usually detritivores, although during drought periods they adopt more scavenger-like tendencies. breaks down the decaying leaf litter of many plant species, such as
Herbivory and carnivory have also been observed. Chenopodium album (Lamb's quarters), Capsella bursa-pastoris (Shepard's purse), Stellaria media (common chickenweed), and Veronica persica (Persian speedwell). ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Le Clec’h, et al., 2013; Moriyama and Migita, 2004; Robinson, et al., 2011; Saska, 2008)can also feed on small pieces of garden roots such as carrots, as well as fruit, and laboratory colonies have been maintained on lettuce leaves. Commercial potting soil contains a high organic content, which yields another food source for . Some data suggest that almost ten percent of the pill-bug's diet comes from self-coprophagy, which recirculates microbes and nutrients that were not fully processed during original digestion. During social interactions, individual woodlice can even cannibalize weaker individuals from the same or different species if the prey is injured or caught in the middle of a molting period. has also been known to be granivorous, although seeds are likely only eaten in absence of other, more desirable food sources, such as spring and early summer when leaf litter is scarce. is known to eat the seeds of herbs such as
Food deprivation reduces growth rates, but is not as serious a threat to survival as might be assumed. In one experiment, ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Le Clec’h, et al., 2013; Saska, 2008)individuals starved of food for three months were still able to survive under laboratory conditions.
Common Starling, but few smaller predatory arthropods are able to successfully overcome them. A genus of tropical ants, Leptogenys sp., have elongated mandibles that allow them to pry apart conglobated individuals.has a variety of defenses against predation. This species has evolved heavily encrusted armor, repugnatorial glands located on the pereon which release unpleasant secretions, and conglobation. Their earthen tone coloration also provides some degree of camouflage against wood or rock substrates. These defenses are inadequate against large predators, such as birds, including the
The Dysdera genus of spiders are some of the few nocturnal, ground-dwelling predators that prey on nocturnally active woodlice such as . Woodlice remnants have been found in Dysdera silk retreats and digestive tracts. Lack of woodlice in the diet of the young Dysdera hungarica can impede growth and development. It is hypothesized that the ability of D. hungarica to prey on woodlice is due to its evolution of elongated chelicerae. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Řezáč and Pekár, 2007)
Terrestrial isopods as a whole are traditionally detritivores that feed largely on plant litter, seeds, or scavenged dung. Seed predators play a critical role in the growth of spermatophyte populations, and (Chevalier, et al., 2011; Giraud, et al., 2013; Saska, 2008)can be the dominant seed predators in systems where other seed predator groups (such as birds, ants, slugs, or crickets) are scarce or temporarily inactive.
Individuals in Japan, Madagascar, the United Kingdom, Australia, South Africa, India, and the United States have been observed to carry non-enveloped virions (viral structures or particles) of Iridovirus IIV-31 (invertebrate iridescent virus 31). Blue pillbugs, which are infected with IIV-31, have a shorter lifespan and decreased photo- and water-responsiveness than non-infected individuals. Other terrestrial isopod species have also been observed to be IIV carriers, and infection appears possible in all terrestrial isopods regardless of phylogenetic relationship. Specific methods of IIV-31 transmission remains unclear, but hypotheses range from cannibalism, coprophagy, inter-species aggression, or parasitism by nematode vectors. (Karasawa, et al., 2012)
Many arthropods commonly bear populations of Wolbachia sp., an endosymbiotic bacterium that usually reinforces the host's immune system and is passed down through generations through maternal gametes. This transmission is limited to maternal gametes due to Wolbachia sp.'s tendency to induce feminization of genetic males by forcing zygotes to develop into female adults regardless of their sex chromosome composition. Infection can also be transmitted through cannibalism of weak individuals, although this is far less common than gamete transmission. is particularly susceptible to Wolbachia sp. as the bacterium can reside inside its hemocytes. Unlike the benefits usually provided to other arthropods, presence of Wolbachia sp. in has been linked with immunodepression of hemocytes, particularly in older individuals. Since Wolbachia species have been observed to survive transition through the digestive tract of , the only defenses against infection appear to be normal lysosome activity and cell replacement. Due to the possibility of a scarcity of males, an eventual high prevalence of Wolbachia sp. could lead to extinction, but current Wolbachia sp. prevalence levels do not indicate this as an imminent threat. (Chevalier, et al., 2011; Giraud, et al., 2013; Le Clec’h, et al., 2013; Verne, et al., 2012)
Terrestrial isopods such as Photorhabdus luminescens. Upon entering an isopod host, the entomopathogenic P. luminescens rapidly distributes a toxic protein into the blood that strongly reduces concentration of isopod hemocytes. This reduction in the host's immune protection is lethal, and after injections of P. luminescens in a laboratory setting, four out of six individuals were dead after 48 hours of exposure. This rapid host decline is notable because the bacterium itself could potentially perform little or no multiplication during that time. (Sicard, et al., 2014)have a less common, but more deadly, relationship with the bacterium
Some pillbug species, Plagiorhynchus cylindraceus. Feces from the primary bird hosts of P. cylindraceus, notably Sturnus vulgaris, contain the eggs. , being coprophagic, can ingest the eggs, which hatch inside the pillbugs' digestive tract. P. cylindraceus is small, usually only 2 to 3 mm at maximum length, but large infestations can crowd internal organs. Plagiorhynchus cylindraceus infestations also render female isopods sterile, and directly alter the behavior of its host. Infected individuals leave their natural habitats and move into wide open spaces where bird predation is more likely. ("Acanthocephala (Thorny Headed Worms)", 2003; "Isopoda (Pillbugs, Slaters, and Woodlice)", 2003)among them, act as an intermediate host in the life cycle of an acanthocephalan worm species,