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Class Malacostraca Kate Atkinson, Ruby Berin, Niki Geller, Maddie Tanda Characteristics ● ● ● ● ● ● ● Two chambered stomach Centralized nervous system Usually eight legs (first two sometimes pinchers) Three part body (Head, thorax, and abdomen) o Usually the head consists of 5 segments o Thorax consists of 5-8 o Abdomen consists of 6 They usually have paired eyes and they are usually stalked o A stalked eye means that the eye is held away from the body, giving them a wider range of vision Appendages hanging from the abdomen called pleopods, or swimmerets o Used for swimming, brooding eggs, catching food, and (in isopods) gills Some have a carapace What makes them unique? ● The most numerous and most successful of the four major classes of Crustacea ● Their members constitute more than two-thirds of all living crustacean species ● They exhibit the greatest range of size (less than one millimetre, or 0.04 inch, to a limb spread of more than three metres, or 10 feet) and the greatest diversity of body form ● They are abundant in all permanent waters of the world ● They have developed specialized organelles sensitive to odors, sounds, vibrations, and physical contact and added more appendages to the mouthpart ● This lead to the terrestrial malacostraca to make better use of the environment around them Body Plan: External ● Hard exoskeletons, composed of chitin and calcareous material o o Carapace Soft at the joints for movement ● Jointed appendages, which are specialized in certain species for different functions o Claws, pincers, etc. Body Plan: Internal ● ● ● ● ● ● Hemocoel (blood-filled coelom) Striated muscles (with flexors/extensors) Gas exchange through thinner cuticle or gills “Open” circulatory system (no separation of blood by vessels) Excretory organs in antennae regulate composition of body fluid Supraesophageal ganglia (control eyes/antennae) and subesophageal ganglia (control mouth, appendages, etc) connect ● Molting (process of making a larger cuticle); more common in juveniles ● Ecdysis (shedding of the cuticle) Isopoda ● Can live in a wide variety of habitats, some being marine (and can live on the ocean floor), others can be terrestrial (in moist environments) ● Vary in size, ranging from 0.3 mm to 50 cm in length ● Have two pairs of antennae with one pair feeling along the ground ● Female Isopods carry eggs in a pouch called a “marsupium” ● Isopods eat fungi, decaying plant matter, plant growth, and dead animal matter ● Certain species roll into a ball to protect themselves from predators like ants, spiders, toads, and frogs ● Over 10,000 species of isopods worldwide Armadillidium vulgare: Pill bug ● ● ● ● They aren’t bugs, they are terrestrial crustaceans related to shrimp They molt 4 or 5 times in their lifetime On rare occasions you may find a bright blue or purple roly poly then it is known to be sick, but it isn’t harmful to humans Females can reproduce without a male by a process called parthenogenesis Deto echinata: Horned Isopod ● Known as a horned isopod because of the long curved 'horns’ that extend from the rear of each thoracic segment, longer in males ● Usually found with kelp and other drift algae on rocky shores ● Feeds on washed-up algae, carrion or live prey ● Eggs emerge from brood pouches as adults ● Can reach up to 30 mm in length Bathynomus giganteus: Giant Isopod ● Gigantism in the species is the result of the pressure from it’s deep sea habitat, on the sea floor ● 7 ½ to 14 inches in length as an adult ● Can survive for up to four years without food Amphipoda ● ● ● ● 9,500 species No carapace, laterally compressed bodies Have different types of legs, unlike isopods Are found in a wide variety of aquatic environments (from freshwater to that with twice the salinity of the ocean) ● No metamorphosis Talitrus Saltator: Sandhopper ● Stay buried underneath the sand during the daytime, and emerge at night in order to feed on vegetation ● Were given their name because of their ability to hop when disturbed ● One antenna is always much longer and thicker than the other Pariambus typicus ● Require water of higher salinity ● Can grow to a size of 7 mm ● Males exhibit a pair of vestigial lobes (not shown) ● Found mainly in the North Seas Hyperia galba: Big-eye Amphipod ● They live in jellyfish, just under the bell ● Live off of the jellyfish eggs ● Found in the ocean’s pelagic zone Euphausiacea ● Scientists suspect that the total weight of all the Antarctic Krill in the world is more than the total weight of all humans on earth ● The number of krill is declining, and this is due to global warming and a large krill fishing industry ● Can be found in water as deep as 2,000m ● Filter feeders that eat diatoms Euphausiacea (continued) ● Divided into two families: 1. Bentheuphausiidae: consists only of Bentheuphausia amblyops, a deep-water krill 2. Euphausiidae: Other 89 known krill species. Bioluminescent ● Range in length from 8-70mm, the largest at 14cm ● Have a hard, calcified exoskeleton with three segments: the cephalon, thorax, and abdomen ● Head has 5 segments, thorax has 8, tail has 6 (each segment with a pair of appendages) Bentheuphausia Amblyops ● Found in the southern part of the North Atlantic Ocean ● Only species in its family ● Are a deep red color with white gills ● Live in the deep sea Euphausia Superba: Antarctic Krill ● Probably the most abundant animal species on earth in terms of mass ● Can live up to 6 years ● Can gather in groups with densities reaching 10,000 krill per cubic meter ● Bioluminescent Euphausia Crystallorophias: Ice Krill ● Lives more south than any other krill species ● Have been found in water as deep as 4,000 meters ● Food source for fish, whales, and penguins Decapoda ● ● ● ● ● ● ● ● Typically have ten legs (five pairs of legs) Most species have the first pair modified as claws In front of the main pair of legs there are three appendages that are used in handling food On top of the head there are compound eyes that are located on eyestalks Most are predators or scavengers but some feed on algae and the land crabs will eat fruits and leaves Most have gills that project upward from near the base of the thoracic appendages and are enclosed within a protective gill chamber Reproductive organs are found at the dorsal part of the thorax o In males there is a single pair of testes and the sperm ducts open at the fifth pair of legs (at the base) o Females oviducts open to the exterior at the base of the third pair of legs All decapods have the ability to regenerate Stenorhynchus seticornis: Arrow Crab ● Prey on feather duster worms and bristle worms and pick through detritus but will also catch slow-moving fish ● Three to six centimeters ● They shed their exoskeleton and the new skin hardens with calcium carbonate (obtained by the water and by eating the old shell) Procambarus alleni: Blue Crayfish ● They are pretty aggressive towards each other ● They range from seven to eight inches ● They like to have lots of hiding places around them because they are boring Panulirus interruptus: California Spiny Lobster ● They do not have any claws ● To protect themselves they use the spines along their bodies ● They make loud sounds with their antennae to scare off predators ● They may shed 40 times before they reach the harvest size Hymenocera picta: Harlequin Shrimp ● They go out to hunt mainly at night because they are shy ● Usually will stay in a pair with a male and a female ● Adults eat sea urchins