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Terms in this set (145)

Arthropods grow by molting, in which the exoskeleton is periodically shed. The unprotected and vulnerable arthropod body then undergoes a period of rapid growth, forming a new cuticle or exoskeleton. The exoskeleton poses a special problem for growth. Step by step process.
Non arthropods growth is linear/exponential; continual gradual growth until maximal genetic size is reached.
Arthropod cuticle is the major part of integument and exoskeleton that is highly protective without sacrificing flexibility or mobility. It is the muscular support and acts as a protective shield as the insect develops but not cellular, cannot grow and offers little scope for maintenance, or increasing in size. The process of molting fixes this.
Procuticle is covered with a thin, waxy, water-resistant out layer containing no chitin. Made up of an outer exocuticle (before molting) - any major in which major thickening, armoring and biomineralization occurs, and the inner endocuticle (after molting) - a laminated structure of layers of interwoven fibrous chitin and protein molecules.
Epicuticle is the outer layer and is much thinner than the procuticle.
Molting or ecdysis is the periodical shedding of the external part of the cuticle. Old procuticle separates from epidermis which secretes a new epicuticle, new exocuticle is secreted as molting fluid dissolve the old endocuticle, at ecdysis, the old cuticles are discarded, and in postechdysis, new cuticle is stretched and unfolded, and endocuticle is secreted.
-Subphylum Trilobitomorpha (Trilobita) - Bodies were divided into three sections (three lobes) as well as a head and body; 17,000 known species
-Subphylum Chelicerata - include horseshoe crabs, and arachnids such as scorpions, spiders, mites, and ticks. 1st pair of appendeges modified to form chelicerae; pair of pedipalps and four pairs of legs; no antennae; no mandibles; have segmented bodies with jointed limbs; all covered in a cuticle made of chitin and proteins; all major feeding strategies such as predation, parasitism, herbivory, scavenging, and eating decaying organic matter. 77,000
-Subphylum Myriapoda - all uniramous, one pair of antennae and mandibles, one or two pairs of maxillae (lower lip); simple eyes; breath through spiracles that connect to a tracheal system; long tubular hear that extends through much of the body, few blood vessels; produce packet of sperm in mating; contain millipedes and centipedes; 13,000 species.
-Subphylum crustacea - mostly aquatic with gills; biramous modified appendages; 2 antennae, 1 pair of mandibles, and 2 pair of maxillae; free living aquatic animals while some are terrestrial (woodlice), parasitic (fish lice, tongue worms), and sessile (barnacles). 3 body regions, each having a pair of appendages; thoracic segment bear legs; main body cavity is open circulatory system, where blood is pumped into the haemocoel by a heart near the dorsum. Include crabs, lobster, crayfish, shrimp, krill, and barnacles. 67,000 species.
-Subphylum Hexapoda - Insects; head of 6 fused segments; 3 pair of legs jointed; separate sexes; metamorphosis; largest number species of arthropod. Very abundant in terrestrial environments; body divided into anterior head, thorax, and posterior abdomen; head is composed of presegmental acron that usually bears eyes, followed by 6 segments, all closely fused, with appendages. Mouth is between the 4th and 5th segment and covered by projection on the 6th called a labrum. Thorax is composed of 3 segments and the abdomen consists of 11 segments in all true insects.
The open circulatory system of the crayfish has no veins. Two arteries leave the heart, the abdominal aorta (toward the posterior) and the anterior dorsal aorta (toward the anterior). The open circulatory system is common to molluscs and arthropods. Open circulatory systems (evolved in crustaceans, insects, mollusks and other invertebrates) pump blood into a hemocoel with the blood diffusing back to the circulatory system between cells. Blood is pumped by a heart into the body cavities, where tissues are surrounded by the blood.
Crayfish respire through the exoskeleton and through the gills which are around its legs. As the crayfish walks, the surface area of the gills spread so the water can pass through in order for the crayfish to breath.
The antennal and maxillary glands primarily regulate ionic balance. The total balance of salts and water is also controlled in part by the gut, which can absorb both. The antennal gland also has been shown to reabsorb glucose. Most crustaceans excrete the end product of nitrogen metabolism, in the form of ammonia, through the gills. Some of the more terrestrial forms produce urea or uric acid, which are far less toxic than ammonia. Urea and uric acid may be stored in special large cells near the bases of the legs or excreted without the loss of much water. Both have the same basic structure: an end sac and a convoluted duct that may expand into a bladder before opening to the outside.
Antennal and maxillary glands are the excretory filaments in Crustacean. These primarily regulate ionic balance. These are tubular structure of the base of either the maxillae or antennea. These have end sacs called labyrinths which connect to the dorsal bladder via excretory tubes. Hydrostatic pressure forces excrement to move through the labyrinth down the excretory tubules to the bladder. The antennal and maxillary glands also reabsorb nutrients and organic materials.
Crayfish rely upon the tactile input from its second antennae to detect topographical changes in the environment and that such topographical changes can be retained for at least 24 hours.
Through saclike statocyst on the basal segment of each first antenna. These bear sensory setae that serve as statoliths along with grains of sand; animal changes position, so does grain of sand, which stimulate the brain; and the animal adjusts accordingly
A nauplius is the free swimming microscopic first larval stage of many crustaceans, having an unsegmented body; three pairs of appendages and a single median eye.
Direct and indirect development are terms that describe different processes of animal development. Animal development begins with a fertilized egg. The difference between direct and indirect development lies chiefly in the progression through the juvenile phase of life. The path from conception to a sexually mature adult creature is very different in these two processes. Direct development refers to the process of development in which an animal is born in a smaller version of its adult form. There is no major transition in the form of the animal from infancy to maturity. Animals who experience direct development (Reptiles, birds and mammals) may have a large amount of yolk in order to nourish the young, or the young may be fed directly by the mother's body. Both these methods of nourishing the young require a great deal of energy from the mother. Therefore, the number of offspring must necessarily be small. With indirect development (echinoderms, amphibians and insects undergo indirect development: butterflies, dragonflies, frogs), an animal's birth form is very different from the adult form. The embryo hatches from the egg in a larval form. The larva undergoes a drastic metamorphosis in order to achieve its adult stage. Animals that undergo indirect development lay numerous eggs. Because the eggs are small, they have relatively little yolk. Due to the small amount of yolk, the larva develops and hatches rapidly.
Insect respiration is accomplished without lungs. Instead, the insect respiratory system uses a system of internal tubes and sacs through which gases either diffuse or are actively pumped, delivering oxygen directly to tissues that need it via their trachea (element 8 in numbered diagram). Since oxygen is delivered directly, the circulatory system is not used to carry oxygen, and is therefore greatly reduced. The insect circulatory system has no veins or arteries, and instead consists of little more than a single, perforated dorsal tube which pulses peristaltically. Toward the thorax, the dorsal tube (element 14) divides into chambers and acts like the insect's heart. The opposite end of the dorsal tube is like the aorta of the insect circulating the hemolymph, arthropods' fluid analog of blood, inside the body cavity. Air is taken in through openings on the sides of the abdomen called spiracles. Gas exchange patterns in insects can range from continuous and diffusive ventilation, to discontinuous gas exchange. During continuous gas exchange, oxygen is taken in and carbon dioxide is released in a continuous cycle. In discontinuous gas exchange, however, the insect takes in oxygen while it is active and small amounts of carbon dioxide are released when the insect is at rest. Diffusive ventilation is simply a form of continuous gas exchange that occurs by diffusion rather than physically taking in the oxygen. Some species of insect that are submerged also have adaptations to aid in respiration. As larvae, many insects have gills that can extract oxygen dissolved in water, while others need to rise to the water surface to replenish air supplies which may be held or trapped in special structures.
1. Stomatodeum (foregut): This region stores, grinds and transports food to the next region. Included in this are the buccal cavity, the pharynx, the oesophagus, the crop (stores food), and proventriculus or gizzard (grinds food). Salivary secretions from the labial glands dilute the ingested food. In mosquitoes (Diptera), which are blood-feeding insects, anticoagulants and blood thinners are also released here.
2. Mesenteron (midgut): Digestive enzymes in this region are produced and secreted into the lumen and here nutrients are absorbed into the insect's body. Food is enveloped by this part of the gut as it arrives from the foregut by the peritrophic membrane which is a mucopolysaccharide layer secreted from the midgut's epithelial cells. It is thought that this membrane prevents food pathogens from contacting the epithelium and attacking the insects' body. It also acts as a filter allowing small molecules through, but preventing large molecules and particles of food from reaching the midgut cells. After the large substances are broken down into smaller ones, digestion and consequent nutrient absorption takes place at the surface the epithelium. Microscopic projections from the mid-gut wall, called microvilli, increase surface area and allow for maximum absorption of nutrients.
3. Proctodeum (hindgut): This is divided into three sections; the anterior is the ileum, the middle portion, the colon, and the wider, posterior section is the rectum. This extends from the pyloric valve which is located between the mid and the hindgut to the anus. Here absorption of water, salts and other beneficial substances take place before excretion. Like other animals, the removal of toxic metabolic waste requires water. However, for very small animals like insects, water conservation is a priority. Because of this, blind-ended ducts called Malpighian tubules come into play. These ducts emerge as evaginations at the anterior end of the hindgut and are the main organs of osmoregulation and excretion. These extract the waste products from the haemolymph, in which all the internal organs are bathed). These tubules continually produce the insect's uric acid, which is transported to the hindgut, where important salts and water are re-absorbed by both the hindgut and rectum. Excrement is then voided as insoluble and non-toxic uric acid granules. Excretion and osmoregulation in insects are not orchestrated by the Malpighian tubules alone, but require a joint function of the ileum and/or rectum.
In hemimetabolous insects, immature stages are called nymphs. Development proceeds in repeated stages of growth and ecdysis (moulting); these stages are called instars. The juvenile forms closely resemble adults', but are smaller and lack adult features such as wings and genitalia. This process is known as "partial" or "incomplete" metamorphosis. The differences between nymphs in different instars are small, often just differences in body proportions and the number of segments, although external wing buds will form in later instars; incomplete metamorphosis (i.e the 3 stage or Hemimetabolous ones) have no pupa and their wings, in those insects that have wings, develop on the outside of their body. What hatches out of the egg looks, in most cases, like a wingless miniature version of the adult insect. Some good common examples are Cockroaches, Grasshoppers, Crickets, Stick Insects and True Bugs (Shield bugs, Squash bugs, Stink bugs etc.)
In holometabolous insects, immature stages are called larvae, and differ markedly from adults. Insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa, or chrysalis, and finally emerge as adults. This process is called "complete" metamorphosis. It is theorized that the pupal stage is the evolutionary compaction of all the nymphal stages of their hemimetabolous ancestors, while the larval stage is an extended, mobile form of the developing embryo; complete metamorphosis and a 4 stage life cycle (i.e the Holometabolous ones) do have a pupa and their wings develop inside their bodies and are therefore not seen at all until the adult insect emerges. The young of holometabolous insects, properly called 'larva' seldom look anything like the adult forms of the insect at all. Some well known examples are True Flies (Diptera) and their maggots, Butterflies (Lepidoptera) and their caterpillars, Dobsonflies (Neuroptera)and their hellgrammites and Beetles (Coleoptera) and their grubs
Repellency- A foul smell or a bad taste is often enough to discourage a potential predator. Stink bugs have specialized exocrine glands located in the thorax or abdomen that produce foul-smelling hydrocarbons. These chemicals accumulate in a small reservoir and are released onto the body surface only as needed. The larvae of certain swallowtail butterflies have eversible glands, called osmeteria, located just behind the head. When a caterpillar is disturbed, it rears up, everts the osmeteria to release a repellent volatile, and waves its body back and forth to ward off intruders.
Crypsis -Insects that blend in with their surroundings often manage to escape detection by predators and parasites. This tactic, called cryptic coloration, involves not only matching the colors of the background but also disrupting the outline of the body, eliminating reflective highlights from smooth body surfaces, and avoiding sudden movements that might betray location. Obviously, this tactic loses much of its effectiveness if an insect moves from one type of habitat to another. Well-camouflaged insects usually stay close to home or make only short trips and return quickly to the shelter of their protective cover. Many ground-dwelling grasshoppers and katydids have colors of mottled gray and brown that help them "disappear" against a background of dried leaves or gravel. Closely related species that live in foliage are usually a shade of green that matches the surrounding leaves. The larvae of some lacewings improve their camouflage by attaching bits of moss or lichen from their environment onto the dorsal side of their body.
Mimicry -If a distinctive visual appearance is sufficient to protect an unpalatable insect from predation, then it stands to reason that other insects might also avoid predation by adopting a similar appearance. This ploy, essentially a form of "false advertising". Viceroy butterflies (mostly palatable to birds) are largely protected from predation because they resemble monarch butterflies (very distasteful). Batesian mimicry is usually a successful strategy as long as the model and mimic are found in the same location, the mimic's population size is smaller than that of the model, and predators associate the model's appearance with an unpleasant effect.
Aggression - some insects fight off predation
Touch- Some insects can't see very well, and some live in dark places, so they need a method of communication that doesn't depend on sight. When an ant is 'following a leader,' it uses its antennae to tap the leader's legs so the lead ant knows that its follower is keeping up with it. Other bugs send vibrations through the plant they are on to warn each other of approaching danger. Smell - Insects have an incredible sense of smell. To communicate by smell within a species, insects release chemicals called pheromones. These special chemicals do many things, including marking trails and attracting mates. An ant who finds a food source leaves a pheromone trail as it heads back to the colony. As other ants come across the trail they follow it to the food source and leave another layer of pheromone on their way back. This makes the trail stronger and attracts even more ants. Sometimes pheromones are released into the air, and insects smell them with their antennae. Other times they are released onto something in which case the insect can taste the chemical with its feet. Sound -Insects can make lots of sounds. Many times, these sounds are higher than human ears can hear. Insects can hear them with sensitive membranes called tymbals located on their abdomen or legs. Bugs like crickets and grasshoppers make sound by rubbing one part of the body (like a leg) against another (maybe a wing). This is called stridulation. Some insects, including cicadas, can make a very loud sound by vibrating a membrane on their body (their tymbal). A hollow part of their body cavity acts as a resonance chamber to amplify the sound. Some of them use these spiracles to make sounds. The Madagascar Hissing Cockroach pushes air out of its spiracles very fast to make a hissing sound. Bees and mosquitoes buzz when they fly because their wings vibrate fast enough to produce a sound. Sight -Insects have compound eyes, made up of thousands of tiny lenses. These lenses don't allow them to see very clearly, but they do make them highly sensitive to light and movement. Insects communicate visually in a passive way by their colorings and markings. After eating the poisonous Monarch butterfly, for example, predators avoid its orange and black coloring. The Viceroy butterfly looks almost identical to a Monarch, so predators avoid it too, even though it is safe to eat. Some moths have a different way of scaring off predators - they have marks on their wings that look like big eyes, threatening would-be attackers.
Caste is a subset of individuals within a colony of social animals that is specialized in the function it performs and distinguished by anatomical or morphological differences from other subsets. The queen is the only bee without which the rest of the colony cannot survive. Only one queen lives in a given hive. She is the largest bee in the colony, with a long and graceful body. She is the only female with fully developed ovaries. The queen's two primary purposes are to produce chemical scents that help regulate the unity of the colony and to lay eggs. The majority of the hive's population consists of worker bees. Worker bees are all female. Workers are smaller than the queen, their abdomens are shorter, and on their hind legs they possess pollen baskets, which are used to tote pollen back from the field. Like the queen, the worker bee has a stinger. It has a barb on the end. The barb causes the stinger, venom sack, and a large part of the bee's gut to remain in a human victim. The only male bee in the colony, drones make up a relatively small percentage of the hive's total population. He is larger and stouter than a worker bee. But his shape is in fact more like a barrel. The drone's eyes are huge and seem to cover his entire head. He doesn't forage for food from flowers, and he has no pollen baskets. He doesn't help with the building of comb, because he has no wax-producing glands. He has no stinger. An organ inside the queen called the "spermatheca" is the receptacle for the sperm. The queen will mate with several drones during her nuptial flight. -Each termite lives in a nest or colony with hundreds, thousands, or even millions of its brothers and sisters. The worker caste is the largest group. It consists entirely of immatures, both males and females. These soft-bodied, wingless individuals clean, maintain, and repair the nest, gather food and water, care for the young, and construct new tunnels and galleries as the colony grows. These juveniles all have the genetic capacity to undergo additional molts and become soldiers or reproductives, but most will spend their entire lives as workers. -Members of the soldier caste are larger in size but fewer in number than the workers. They are also wingless, but they have large heads with powerful jaws. Their job is to guard the nest site and protect it from attacks by ants or other invaders. The soldiers are unable to care for themselves so they must be fed and groomed by the workers. -The reproductive caste always includes a king and a queen who are the parents of the termite family and founders of the colony. These are the only adult insects in the colony. The queen lays large numbers of eggs which develop into more workers and soldiers as the family grows. The termite's caste system is regulated by pheromones. The king and queen each produce special pheromones that circulate throughout the colony and inhibit workers of the same sex from molting into reproductive adults. A death in the royal family results in a lower concentration of the corresponding pheromone and, subsequently, one or more workers will molt into replacement reproductives.
Chewing- insects have two mandibles, one on each side of the head. The mandibles are positioned between the labrum and maxillae. They are typically the largest mouthparts of chewing insects, being used to masticate (cut, tear, crush, chew) food items. They open outwards (to the sides of the head) and come together medially. Often used for defense as well. -Situated beneath the mandibles, paired maxillae manipulate food during mastication. At the outer margin, the galea is a cupped or scoop-like structure, which sits over the outer edge of the labium. They also have palps, which are used to sense the characteristics of potential foods. The labium is the floor of the mouth. With the maxillae, it assists manipulation of food during mastication The hypopharynx is a somewhat globular structure, arising from the base of the labium. It assists swallowing.
Siphoning - deals only with sucking insects, not those that pierce prior to sucking. The typical example is the moths and butterflies. Some moths have no mouthparts at all. All but a few adult Lepidoptera lack mandibles with the remaining mouthparts forming an elongated sucking tube, the proboscis. The proboscis is a long tube that is formed by heavily modified maxillae, specifically the galea.
Piercing and sucking -A number of insect orders have mouthparts that pierce food items to enable sucking of internal fluids. Some are herbivorous, like aphids and leafhoppers, while others are insectivorous, like assassin bugs and mosquitoes (females only).Paired mandibles and maxillae are present, together forming the stylet, which is used to pierce an animal's skin. During piercing, the labium remains outside the food item's skin, folding away from the stylet. Saliva containing anticoagulants, is injected into the food item and blood sucked out, each through different tubes.
Sponging -The housefly is the typical sponging insect. The labium gives the description, being articulate and possessing at its end a sponge-like labellum. Paired mandibles and maxillae are present, but much reduced and non-functional. The labium forms a proboscis which is used to channel liquid food to the esophagus. The housefly is able to eat solid food by secreting saliva and dabbing it over the food item. As the saliva dissolves the food, the solution is then drawn up into the mouth as a liquid. The labellum's surface is covered by minute food channels, formed by the interlocking elongate hypopharynx and epipharynx, which form a tube leading to the oesophagus. The food channel draws liquid and liquified food to the oesophagus by capillary action.
Tracheae open to the outside through small holes called spiracles. The spiracles can act as muscular valves in some insects. The network of tracheae equalized pressure throughout the system.
Gas exchange occurs at the cellular level; no need for respiratory pigment because the tracheoles that carry fresh air come in direct contact with almost every cell.
The circulatory system functions in oxygen transport in some aquatic immature insects; hemolymph consists of plasma and amebocytes for lymphatic system and immune/cellular house keeping. Body parts are bathed in hemolymph.
Insects have a unique respiratory system that is separated from the circulatory system. This respiratory system is composed of slender tracheae that enter the hemocoel from spiracles. Insects have an open circulatory system meaning that blood and interstitial fluids move freely throughout the hemocoel, not in vessels that reconnect to the heart. This system typically causes organisms to have bursts of movement followed by oxygen deprovation. Insects counter this by the means of a separate tracheal system in which oxygen flows in through the spiracles into slender tracheal tubes. These tracheal tubes function like air ducts in a house, starting from being relatively large, and becoming more slender as they spread throughout the hemocoel. This eventually leads to capillary like endings called tracheal end cells which are fluid filled cells at the end of the trachea. These transport oxygen directly to the surrounding tissue, thus providing a constant flow of oxygen to the tissue. This allows insects to have incredibly high endurance for example houseflies are able to beat their wings non stop 24/7 and turn upside down and beat their wings until they starve to death.
-Eurypterids - extinct; giant water scorpions; 3m in lenth; spike like telson, large crushing claws; lived in marshy habitats; crawled on land for short distances
-Xiphosura aka Horseshoe crabs - unsegmented carapace; long point telson; book gills; hinged between cephalothorax and abdomen; crustaceans; did well 400 mya as organisms began to move on land (Debonian); gestation of eggs is in a tidal cycle; move in on highest tide of the month, plant eggs in sand and cover them, then ride back out; 28 days later, the babies hatch and release into the water; what comes out of the egg is called a trilobite larva; over time grows and feeds; successful strategy; only 4 or 5 species compared to so many, years ago. Limulus (Atlantic horse shoe crab) are successful due to sandbar stability.
-Pycnogonida - Sea spiders can get very large (70inches); sort of live like the tick like existence except life on Cnidarians, clams and starfish as well; stick proboscis in the organism and feed; overall in most organisms in the world the parents do not usually protect the eggs but females are primary or evolved; seahorse and sea spiders males are the primary role in reproduction; females live for multiple years; females release all of her eggs at one time; males with as many mates as they can; males glue the eggs on the arms or ovitures and carry them; sometimes 15-20 egg masses; larval stage is...; sea spiders have an epistostoma abdomen which is smaller than land spiders which have a larger abdomen that carries most of the organs.
The males need to be stealthy, strong, and quick; typically seen as food to females, sex then eaten; males dance by grabbing on to her claws; stinger isn't as quick as most think, plant front legs and then swing the stinger over the head; male grabs females claws and retreat, female pushes forward, male deposits sperm mass on ground and tries to line up the spermatophore with the female, male thrusts forward forcing the female to crack the sperm mass hoping the sperm fertilize the female, male runs away; when fertilized the babies climb on the mothers back, if fall off moms do not recognize the baby as their own anymore and may eat it.
Scorpions have their own special mating ritual in which the male will use his pinchers to grab the female's pinchers and pull her along in what can only be classified as a "courtship dance". In some species the male will even sting the female, however, this does not cause her any harm. During this "dance" the male will drag the female along the ground until he has found a good spot to lay his seeds (usually on a twig or rock). After the male has lain his seeds, he will then drag the female through them and she will secrete them into her body through an opening in her abdomen.
The eggs will stay within the female for several months to a year depending upon species. The young are born live and fall into the mother's legs which she especially folds up for this occasion, creating a sort of basket and means for them to climb up to her back. A female Scorpion carries her babies (usually 25-35) on her back for 10 to 15 days before they go off on their own and are fully independent.