Crustaceans. =shelled creatures; the insects of the sea. some crustaceans live for several decades; some molt throughout life.

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1 Crustaceans =shelled creatures; the insects of the sea ~67,000 species eg: lobsters, crayfish, shrimp, crabs, water fleas, copepods, barnacles, pill bugs, etc crustaceans are mostly aquatic, mostly marine inhabit most waters of the earth: ocean, arctic, freshwaters, high mountain creeks and lakes thermal springs, brine waters many are at the base of aquatic food chains part of zooplankton only a few are terrestrial; eg. sow bugs or pill bugs crustaceans vary in size from microscopic (<0.1 mm) to >12 eg largest (longest) is giant Japanese crab à up to 12 from end of claws to tail and a weight of 40 lbs (20 kg) eg. crayfish & freshwater shrimp largest crustaceans in freshwaters some up to 2 and weigh 9 lbs a river shrimp, Macrobrachium jamaicense, was collected from Devils River, Tx: 3 long including antennae, body was 10.5 long, 3 lbs some crustaceans live for several decades; some molt throughout life so continuous increase in size eg. Lobsters may be the longest lived Crustaceans one was collected that weighed 35 lbs was estimated to be 50 yrs old; à ~ 4 long total body only was ~2 long, claw was an additional 20 some crustaceans are quite colorful; blue, red, orange, yellow many are bioluminescent Distinguishing Characteristics of Crustacea: 1. the crustacean body is divided into a cephalothorax, abdomen and tail (telson) often have carapace extending over abdomen and gills Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, in some groups carapace forms clamshell like valves that encloses body 2. they are the only arthropods with 2 pairs of antennae 3. most with compound eyes, smaller ones only with simple eyes 4. crustaceans use jaw-like mandibles as main feeding structures; also maxillae and maxillipeds 5. abdomen usually with pairs of jointed appendages on most segments they generally have many pairs of appendages range from 3 to 50 pairs of limbs many are biramous appendages à 2 branches from base segment appendages are modified for a variety of uses sensory feeding defense walking swimming reproduction respiration Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, lots of variation in appendages between groups cephalothorax eg in decapods (crayfish, crabs, lobsters, etc): 1st 2 pair à antennae with chemoreceptors next 5 pr à feeding appendages; including mandible, maxilla and maxillipeds next 5 à walking legs including cheliped and gills abdomen next 5 à called swimmerets; used to carry eggs and as copulatory organ telson last à uropod = swim fin most crustaceans can cast off legs or pinchers to escape predators and later regrow them 6. unique larval stage in marine forms: Body Form nauplius larva most have single larval eye throughout several larval stages some retain the larval eye into adulthood and never develop compount eyes the most ancient crustaceans resembled some kind of aquatic centipede; long segmented body with similar segments and similar appendages Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

2 over time, great variety of body types arose only one small group of these primitive crustaceans remain today only 10 species in their own class Remipedia in most crustaceans today, the body is usually divided into a cephalothorax, abdomen and tail (telson) some have distinct head and thorax often have carapace extending over the sides of the animal in some groups carapace forms clamshell like valves that encloses the whole body in others the carapace covers cephalothorax but not abdomen cephalothorax feeding and sensory appendages 5 or more pairs of walking legs abdomen including chelipeds (pinchers) on 1 st pair segmentation is most apparent in the abdomen Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, abdomen usually with pairs of jointed appendages on most segments telson (tail) has its own paired appendages Movement = uropods that with the telson form a finlike tail Crustaceans generally have many pairs of appendages larger species 5 or more pairs of walking legs most appendages are biramous they branch like a wishbone ; one of the branches usually has a gill attached at its base most crustaceans can cast off legs or pinchers and regrow them voluntary (striated) muscle tissue arranged in antagonistic groups eg. flexors & extensors similar to vertebrates Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Feeding & Digestion use jaw-like mandibles as main feeding structures also maxillae and maxillipeds chelipeds (1 st walking legs) are also used to catch, tear off and put pieces of food to the mouth great variation in feeding types: 1. predators eg. crabs use large claws used to break open shells to feed eg. mantis shrimp 2. herbivores is an ambush predator, extremely carnivorous and aggressive called split thumb in Bermuda and West Indies front end looks like praying mantis has jackknife claws live in solitary burrows eyes are stalked and constantly watch for prey 3. suspension feeders eg. barnacles sit upside down in shell and use Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, legs to strain water for food 4. scavengers eg. isopods, amphipods 5. parasites eg. fish lice, tongue worms crustaceans have a well developed digestive system: cardiac stomach with gastric mill for grinding gastric mill has hardened teeth some have gastroliths in stomach to help grinde food pyloric stomach for sorting digestive gland secretes digestive enzymes Respiration in small crustacea: no special organs à exchange across body surface in larger crustacea: respiration usually by feathery gills on bases of walking legs Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

3 in some sides of carapace form gill chambers that enclose gills Circulation have an appendage called a bailer that creates a water current across gills open circulatory system no veins or capillaries fluid filled coelom = hemocoel dorsal heart in hemocoel heart has ostia (holes) to draw in hemolymph (blood) hemolymph is pumped through 2 or more arteries for distribution most crustaceans have some kind of blood pigment to better distribute oxygen to tissues hemolymph may be bluish, reddish or colorless: most: others: hemocyanin à bluish pigment with Copper hemoglobin à red pigment with Iron crustacean blood has the ability to clot Nervous System: as in other Arthropods, similar to Annelids 2 pairs of ganglia around the esophagus that supply sense organs of the cephalothorax double ventral nerve cord with a pair of ganglia in each segment along the rest of the body Sense Organs sense organs are well developed in crustaceans 1. most have compound eyes and simple eyes (ocelli) compound eye consists of many separate units called ommatidia each with cornea divided into many small squares or hexagons called facets each ommatidium behaves like a separate eye each ommatidium has a moveable pigment component that allows it to adjust to differing light intensities in daylight only light rays that strike the cornea directly reach the photoreceptor cells some: no pigments in dim light rays can activate the photoreceptors in more than one ommatidium Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, zooplanktonic crustaceans show particular sensitivity to light as they undergo daily migrations up and down the water column to stay in the best light regime for feeding yet being able to avoid visually hunting predators 2. chemoreceptors (taste) on mouthparts, 3. crustaceans uniquely have 2 pairs of antennae 4. tactile hairs and spines spread over body 5. statocysts for orientation at base of antennae saclike; opens to surface by pore take in sand grains which trigger hair cells to provide info on orientation 6. hearing: communication by sound many crustaceans make underwater noises to communicate eg. pistol crabs snap claws together producing sound like pulling a cork from a bottle eg. one species of mantis shrimp makes a vigorous rasping noise by rubbing uropods against underside of telson eg. Florida spiny crab produces sound like moist fingers rubbing against a window pane Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, some crabs have striae or ridges on inner side of chelae that they rub against tubercles on carapace some crabs have tympanic membranes on their 1 st leg segments to pick up these sound vibrations sound is used for warning, to frighten enemies, mating rituals, etc 7. Light emitting organs & communication by light many crustaceans have light emitting organs (=photophores) that use luciferase to produce light many crustaceans give off rich blue sparks of light when disturbed eg. some ostracods and a few copepods, even some freshwater decapods krill have light organs with lens and reflector to focus and intensify the light beam many pelagic crustacea flash brilliantly during mating swarms Endocrine System Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

4 hormones help to control: molting although molting (ecdysis) is hormonally controlled the cycle is triggered by environmental stimuli to nervous system eg. temperature, day length, humidity (land crustacea) or some combination molt-inhibiting hormone levels decrease molting hormone increases once molting is initiated it proceeds automatically body coloration chromatophore (pigment cells) behavior is controlled by hormones from glandcells in the base of the eyestalks heart rate blood sugar levels sexual development Excretion nitrogen wastes are excreted through skin (if no gills) or through gills & antennal glands antennal glands (or maxillary/green gland) Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, located in ventral part of the head anterior to the esophagus generally a coiled tube leading to a sac which opens at the base of the antennae or maxillae extracts N-wastes from hemolymph surrounding it and secretes it to the outside also used to regulate water & salts (K & Ca + conserved; SO 4 & Mg excreted) [no malpighian tubules] Reproduction most are separate sexed (dioecious) but a few are hermaphrodites including barnacles some have courtship rituals involving chemical, visual and auditory cues: eg. fiddler & ghost crabs male attract females during the day by waving its claws and both day & night by producing distinctive drumming sounds Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, when a female touches a male the frequency increases dramatically female can only mate after final molt some develop large apron for carrying eggs copulation: male delivers sperm packet to receptacle using modified swimmerets a few groups, mainly those living in temporary waters reproduce by parthenogenesis eg. brachiopods, ostracods, isopods and a few crayfish males are rare or unknown in some species 3 prs appendages 2 pr antennae 1 pr mandibles all function as swimming appendages at this stage from the nauplius stage often develop other distinctive larval forms for different groups of crustaceans eg. zoea larva some crabs eg. protozoea larva shrimp eg. copepodid larva - copepods later there is a more dramatic change =metamorphosis into the adult eggs are generally released into the water some retain their eggs until they hatch in brood pouches eg. Most crabs and shrimp in some crustacea such as crayfish, development is direct with no larval stage but most crustaceans produce a variety of distinctive larval forms as the animal develops many marine crustaeans begin with a characteristic larval form = nauplius larva Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

5 Classification of Crustacea The subphylum Crustacea is divided into 4 major classes (with 2 additional classes for a few rare species) Class Malacostraca (40,000 sp.) largest crustacean class, extremely diverse possibly the most diverse class in the entire animal kingdom head-thorax-abdomen, sometimes head and thorax fused into a cephalothorax appendages on all major tagmata with or without carapace eyes on stalks eg. isopods, pill bugs, amphipods, scuds, shrimp, crabs, lobster, crayfish, krill, mantis shrimp, etc Class Maxillipoda (10,000 sp.) mostly small, reduced abdomen which generally lacks appendages eg. copepods, barnacles, fish lice and tongue worms Class Branchipoda (1000 sp.) eg. water fleas, fairy shrimp, tadpole shrimp, brine shrimp) Class Ostracoda (13,000 sp. (70,000 fossil sp.)) also, small, body flattened side to side and protected by bivalvelike calcareous shell eg. seed shrimp Class Remipedia (17 sp.) very primitive characteristics à resembles a centipede in general body form but with biramous legs very poorly known à all known species are from underwater caves Class Cephalocarida (12 sp.) occur along the coasts of the United States, in the West Indies and Japan 2-3 mm long live in bottom sediment from intertidal zone to 300 m also thought to be very primitive gills on many appendages, including some mouthparts most have compound eyes and carapace; in some the carapace is made of 2 valves that completely enclose the animal Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Crustacea occupy every possible kind of habitat in the ocean and freshwaters. most crustaceans live in the ocean and are one of the pillars of the global marine ecosystems of the 40,000 or so species of crustaceans, about 4000 of these are found in freshwaters. Most Crustacean, both marine and freshwater inhabit benthic and planktonic habitats Benthic Crustaceans most crustaceans are benthic organisms; they live on, in, or near the bottom sediment of both marine and freshwater habitats benthic marine crustaceans include mainly the larger species benthic crustaceans play an important role in decomposing dead or decaying animals, algae and plants crustaceans feed a vast number of other animals in oceans and in freshwaters their numerous symbioses help to control populations of other animals without crustaceans, animal populations in aquatic ecosystems would collapse eg. especially the larger crustaceans; shrimp, lobsters and crabs eg. crabs use large claws used to break open shells to feed eg. fiddler crab uses largest claw for social interactions only uses small claw for scavenging food from sand the females brood eggs or brood young in a ventral brood chamber (=marsupium) on freshwater sediments the larger crustaceans are mainly crayfish and shrimp there are even a few freshwater crabs many eat plant life on the floors of lakes, ponds and streams eg. isopods generally much smaller, <.5 (except for one group of deep water isopods that grow more than a foot long) isopods are mainly scavengers mainly found crawling on the substrate or under rocks and submerged plants seldom found in open water Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

6 common in both marine and small freshwater lakes and streams some crustaceans construct tubes in sediment, wood and rock eg. boring isopods can destroy wooden pilings in less than 2 yrs some isopods can tunnel through limestone rock some have been known to burrow through the insulation of undersea cables shorting them out a few cave adapted forms occur in subterranean waters eg. amphipods (side-swimmers or scuds) much more common and diverse in marine benthos than in freshwaters shrimp-like appearance: strongly compressed laterally but no carapace generally much more active at night than during daytime amphipods are voracious feeders omnivorous scavengers; feed on all kinds of plant and animal matter a few are parasites like decapods, the females brood eggs and young in a ventral brood chamber (=marsupium) eg. Ostracoda (=seed shrimp) much more common in freshwater habitats much smaller mainly benthic animals that inhabit all types of substrates in standing and running water a few actively swim just above the substrate generally use their antennae to move enclosed in bivalve carapace that completely covers the entire animal their shells are so strong that they fossilize well ostracods are the oldest known crustacean group in the fossil record marine species are especially important to paleontolotists in dating sediment (65,000 fossil species vs 13,000 living species) generally feed on bacteria, fungi, algae and detritus ostracods have the largest sperm in the animal kingdom in both relative and absolute terms. Ostracod sperm can be up to ten times the length of the male's body! Some male ostracodes need a special organ (Zenker's organ) to aid in sperm transport. ostracods lay their eggs on sediment or aquatic vegetation the eggs can hatch immediately or years later Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, viable eggs have been collected from dried ponds and revived after 20 years some marine crustaceans are sessile (=attached) eg. Barnacles (=Cirripedia) sessile: secrete shell of several calcium plates in which they live common in intertidal areas when tide goes out they can close their shells every time a wave comes in they extend their legs to filter the water considered a kind of mollusk until 1830 but once they were discovered to produce a nauplius larva it was clear they were a kind of crustacean there are 2 main kinds of barnacles: some with stalk = goose barnacles some without = acorn barnacles eggs hatch into motile, nauplius larvae then a cypris larva after swimming a short time the larva secretes a strong polysaccharide cement from its antennae and attaches to the substrate à the strongest adhesive known adults secrete chemicals that attract the larvae to settle near them to facilitate reproduction the carapace develops into a mantle that secretes calcareous plates legs develop in feathery cirri for filtering water animal sits up-side-down in shell and extends legs to filter feed almost all are hermaphrodites yet they cross fertilize with internal fertilization a few species are dioecious with the dwarf males attached to the female they don t feed and die after inseminating the female barnacles are preyed on especially by starfish and snails Planktonic Crustaceans many smaller crustacea are part of the plankton in both marine and freshwaters = zooplankton larger planktonic crustaceans are the primary herbivores feeding on the phytoplankton (algae and bacteria) small planktonic crustaceans such as copepods, ostracods and krill are essential links between producers and larger consumers in aquatic food webs krill and copepods are extremely abundant in the worlds oceans Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

7 these planktonic crustacea may be the animals with the greatest biomass on the planet depending on these zooplankton are a diverse community of predators including other crustaceans, squid, fish, and whales eg. Copepods copepods are one of the most abundant and diverse groups of crustacean over 12,000 species (some believe this to be about 15% of total species out there) may be the most abundant aquatic animals on the planet copepods are abundant in both marine and freshwater environments but much more abundant and diverse in the ocean most common as plankton but many species also occur on or in the sediment as benthic organisms small, slender, clearly segmented body large pair of antennae used for movement feathery legs to filter food feed in a variety of ways: scraping food from hard surfaces, filtering articles from the water, seizing and biting prey extremely important food source for marine fish Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, majority of the diet of commercial fish is copepods some freshwater forms are important vectors for diseases such as guinea worm eg. Krill (Euphasids) small shrimp-like animals extremely abundant in marine plankton often occur in swarms up to 30,000 individuals/m 3 a major part of the diet of whales, seals, penguins and cephalopods among others eg. whales eat 2-3 tons of krill per meal large numbers of crustacean larvae along with fish larvae making up a significant portion of the biomass of the open ocean (=microzooplankton) are a significant source of fish food in marine ecosystems eg. Water Fleas (=Cladocerans) cladocera are especially abundant in permanent freshwater ponds & lakes, among marginal vegetation à important part of freshwater zooplankton much less common in the ocean body is enclosed within a bivalve shell called a carapace that covers the thorax and the abdomen but not the head Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, many cladocerans show a dramatic change in body shape over the year = cyclomorphosis large eyes looks like a single eye but is actually 2 compound eyes that are fused together very large antennae that are used for locomotion inside the carapace are 5 or 6 pairs of feet used to filter the water for food most cladocera are filter feeders and eat algae, protozoa and bacteria they also eat aquatic plants a few are predators on microscopic animals most cladocera reproduce sexually by fertilization of egg with sperm, and parthenogenetically use parthenogenesis for most of the year switch to regular sexual reproduction under adverse conditions female carries her eggs around in a brood pouch enclosed in carapace eggs hatch and young swim free direct development eggs play a key role in dispersal to new habitats resistant to freezing and drying the eggs of some have remained viable for up to 300 years Temporary or Highly Saline Waters certain specialized crustaceans are the dominant animals in highly saline or alkaline environments or in temporary waters such as playas most crustaceans inhabiting these temporary habitats are from the Class Branchiopoda breath through their feet à feathery gills at base of walking legs the branchipoda generally inhabit temporary pools, ponds and playas and are generally completely absent from permanent bodies of water feed mainly on algae, bacteria, protists and microscopic animals they typically appear in the spring and disappear in late summer or autumn as habitat dries to survive most produce very drought resistant eggs that can survive dried or frozen for years in lake beds the eggs of most hatch into nauplius larvae eg. fairy shrimp, tadpole shrimp, clam shrimp eg Fairy Shrimp live in vernal pools and hypersaline lakes worldwide including pools in deserts, ice covered mountain lakes and Antarctica common, especially during the cool months of year, but seldom seen unless pursued Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

8 fairy shrimp are most easily distinguished from all other similar crustaceans in that they swim upside down. not usually found in ponds that contain fish one of few crustacean groups with distinct head stalked compound eyes no carapace some grow up to an inch long 11 pairs of swimming legs use legs to swim upside down graceful movements, often transparent feed by filtering algae, bacteria, protozoans etc from the water or by scraping algae from surfaces Important food source for many birds and fish Many species of fairy shrimp compete intensely for mates. Since mating usually occurs just after the female moults, males often grasp her and are towed around while waiting for her to moult. Some females have a chain of these attached males, including some which have died while waiting includes: brine shrimp (Artemia) only animals that flourish in the Great Salt Lake of Utah and other hypersaline environments today they are cultured extensively as fish food eggs sold as novelties; sea monkeys Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, eg. Tadpole Shrimp (Triops sp.) resembles a baby horseshoe crab considered a living fossil this genus has remained essentially unchanged for the last 70 M years (time of the dinosaurs) large shield-like carapace covering most of the body look somewhat like tiny horseshoe crabs the name Triops refers to it s 3 eyes at end of abdomen are two long filamentous extensions omnivorous: they eat anything organic includng their siblings (they are cannibalistic) usually found in vernal pools, worldwide, scratching at the sediment or straining the water for food several of their activities have human benefits: they eat culex mosquito larvae which transmits west Nile virus used in Japan to eat weeds in rice paddies their presence in the Western US usually indicates the presence of endangered spadefoot toads the eggs are also sold to raise as pets called aquasaurs or trigons or just triops eg. Clam Shrimp (Conchostraca) laterally compressed Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, enclosed within a carapace of 2 valves to resemble a small clam they extend their second antennae out of the carapace to swim they feed on detritus or plankton by drawing water into the carapace most reproduce sexually some reproduce by parthenogenesis Terrestrial Crustaceans while the vast majority of crustaceans are aquatic, some groups are semiaquatic or terrestrial eg. land crabs burrow above tide line into the water table can survive days out of water eg. pill bugs & sow bugs (isopods) isopods are the only group of crustaceans with truly terrestrial representatives have very delicate gill-like respiratory organs that must be kept moist found in damp places under stones and logs able to roll up for protection (=rolly pollys) young develop in brood pouch some salt water relatives are found along coasts and live in seaweed, along rocks and algae Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, some bore into wood causing destruction of pilings and warves eg. beach fleas or sand hoppers (amphipods) Symbioses some are almost terrestrial; found crawling around on piers and jetties many examples have already been cited a. numerous commensal relationships with other invertebrates eg. many bivalves harbor commensal crabs within their shells eg. crabs and shrimp also live inside sponges, worm tubes, etc eg. some barnacles in symbiosis with humpbacks and other whales stick on skin; esp head, flippers and flukes appear to cause little damage except for some species that seem to burrow into the skin but don t seem to cause serious inflammation feed on scraps produced by whale feeding b. mutualistic interactions eg. decorator crabs attach sponges, anemones, etc to their shells for camoflage eg. cleaner shrimp remove skin parasites from fish Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

9 set up cleaning stations along the reefs that fish know to visit remove parasites, dead skin and other debris some cleaner shrimp even enter the mouths of fish to clean gills c. a very diverse variety of crustaceans have become parasitic eg. Fish Lice (Branchiura, eg. Argulus) one of the simplest and most common forms of crustacean parasites are the fish lice parasites on marine and freshwater fish cling tightly to fish with a set of antennae modified into larg barbed suckers have flattened bodies, compound eyes and maxillae modified into suckers to attach to the sides of fish mouth borne on a long proboscis used to suck blood and mucus from their host after feeding on host the parasite detaches and drifts downstream many species can tolerate both fresh and salt waters eg. some isopod parasites mainly ectoparasites eg. Gnathiidae: are similar to ticks in that they attach and gorge on blood then they develop into a nonparasitic stage until they are ready to feed again they repeat this cycle several times during their lives eg. tongue biter: enter host as males through gills and change gender as they mature eg. copepods she attaches herself to fish s tongue and sucks blood fishes tongue disappears and the parasite becomes the functioning tongue of the fish almost half of all copepod species are either parasitic or commensal with other organisms there is a hugh diversity of shapes and lifestyles Parasitic copepods often cling to the outside of their hosts others invade the gills, nostrils or mouth of their host eg. Acrothoracica eg. Dryodora: attaches to the rectum of fish and develop into pustule looking sacs eg. Anchorworms (eg. Lernaeocera): some species embed themselves on the eyes of sharks and feed on the vitreuous jelly inside. eg. Trebius: ectoparasite on the embryo of angelsharks (inside mom) related to copepods and barnacles parasitize corals and echinoderms Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, eg. Tongue Worms (Pentastomida) parasites that live in the respiratory tract of vertebrates, usually reptiles in the tropics also some fish, bird and mammals (including humans) so unlike other crustaceans that until recently they were classified in their own phylum, pentastomida wormlike; 2-13 cm long; >70 sp, 4 fossil genera 4 clawlike appendages at anterior end mouth with protuberance no resp, circ or excretory organs their life cycle involves 2 hosts eg. Tantulocarida the intermediate host is vertebrate prey of final host the larvae live in it s blood crustaceans that parasitize other crustaceans among the smallest arthropods can be less than 0.1 mm long female cypris larva attaches to a crab and injects a mass of eggs these cells migrate to intestine of host and develop rootlike growths that permeate the hosts body develops an extensive system of branches extending into every appendage a saclike growth appears under the crabs abdomen where eggs and sperm form (Sacculina is a hermaphrodite) the crabs metabolism is completely altered: the cells of the parasite multiply and differentiate into a reproductive form which produce an egg mass in the female hosts apron if crab is a male: the host protects, ventilates and grooms the egg mass as if it were her own body assumes shape of a female reduced length of some segments broadening of abdomen testes reduced or converted to ovaries à both male and female resemble mature female bearing eggs: physically and behaviorally eg. Sacculina probably the most bizzare of all parasitic animals Sacculina is a highly modified barnacle that has become a parasite of crabs Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

10 Economic Importance of Crustaceans many are at the base of aquatic food chains part of zooplankton 1. as food eg. crab, lobster, crayfish, shrimp more than 10 million tons of crustaceans are harvested for food each year (2007) à mostly shrimp, crab, lobsters and prawns the heyday of lobster fishing was in the 1890 s: 1892 yield was 24 M lbs of lobster; 25 pounders were common 80% of all crustaceans are harvested in Asia, mainly China some crab are harvested by breaking off claws and throwing rest back blue crab are held captive until they molt, the viscera are removed and they are sold as soft-shelled crab Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, crayfish (crawfish) are commonly eaten in the southern US and in other countries Louisiana produces 70-90% of all commercial crayfish, most of it from aquaculture recent (2007) annual harvest of ~55,000 tons Krill are now being harvested for human consumption around the Antarctic can harvest 12 tons/hour but they are difficult to process goose barnacles are popular food on the coasts of Spain, Portugal and parts of N. Africa France is developing a goose barnacle fishery to export them 292 tons/yr worldwide (2011) In Libya are many brine lakes from which large quantities of brine shrimp (Artemia) are harvested collected in nets and sun dried until they form a foul-smelling black paste then eaten native Americans used to harvest them from the Great Salt Lake Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, bait 3. pets Aquaculture of freshwater crustaceans now accounts for 2.4 million tons of seafood eaten/ year (2011) mainly shrimp and crabs a similar amount was cultured in brackish water aquaculture some are allergic to seafood mainly an allergy to tropomyosin a muscle protein but a few other proteins may also cause allergies crayfish are commonly sold and used as bait either live or only the tail meat sometimes causes problems with bioinvasions crayfish are kept as pets in freshwater aquaria land crabs are often sold in pet stores also brine shrimp and tadpole shrimp Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, many crustaceans are serious pests a. cause crop destruction eg. rice crabs in China and India eat rice; burrows may drain rice fields destroying crops eg. crayfish destroy young cotton plants b. boring & fouling organisms borers destroy warves & docks and wooden hulled boats undermine sea walls and bore into stone destroy underwater cables adhere to ships reduce efficiency and increase hull decay eg. barnacles 5. some act as intermediate hosts for human parasites eg. Guinea worm larva is in copepods; swallowed in contaminated water grow in lymphatic system up to 3 long female produces blister like lesions on lower extremeties to lay eggs in water eg. fish tapeworm Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,

11 larva in Cyclops and Diaptomus eaten by fish humans eat uncooked fish eg. Cladocera are easily cultured and used to study behavior, evolution, speciation and animal ecology 6. Some Crustaceans are used for dissections in biology classes eg. crayfish 7. Real and imagined medicinal uses: many crustaceans have been used as remedies since antiquity cures based on crustaceans were described in medical texts from the 1 st century AD eg. ashes from freshwater crabs used to treat rabid dogs eg. decapod gastroliths rich in calcium used to treat e xcessive stomach acid eg. the hard parts, flesh, and juices had diuretic properties and were used to treat urinary and gynecological problems eg. during the 16 th century crabs were thought to cure TB and cancers eg. even today up to 20 species of crustaceans are used medicinally in Latin America used as remedies for asthma, bronchitis, epilepsy, and hemorrhages 8. Several Crustacea are used as experimental models in research: Animals: Arthropoda - Crustacea; Ziser Lecture Notes,, Animals: Arthropoda - Crustacea; Ziser Lecture Notes,,