WFSC 335 Dr. DronenExam # 3 Study GuidePhylum Arthropoda- Largest assemblage of organisms (750,000 species)- Well seen in fossil record because of exoskeletons- Chitin/protein exoskeletono Must be molted for growth- Jointed appendages- Undergo determinate cleavage- most have a reduced Schizocoel- Open circulatory systemo Hemocoelo Green blood- Aquatic species have gills, terrestrial forms have a tracheal system (composed of a trachea and spiracles)- Do not have nephridia- Have coxal glands, maxillary/antennal glands, or Malpighian tubules - Separate sexes- Fertilization is internal- Eggs of most are centrolechithal and have superficial cleavage Subphylum Trilobitomorpha: trilobites- Extinct- Composed of an anterior cephalon, a middle thorax/trunk, and a posterior pygidium- All postoral segments had paired, similar appendages- So well preserved that we can see entire life cycle- Dorsal longitudinal grooves (2 that give them the "trilobed" look)- Labrum: lip-like structure in front of mouth- Biramous appendages: composed of two branches- Three larval stages (protaspis --> meraspis --> holaspis)- Rachis Subphylum Chelicerata- Cephalothorax (fused head and thorax) or prosoma and an abdomen or- opisthosoma- No antennae are present- Chelicerae- feeding appendages- Pedipalps- modified appendages depending on groupClass Merostomata- 5 or 6 pairs of abdominal appendages modified as gills- Spike-like telsonSubclass Xiphosura: horseshoe crabs- Original "king" crab Subclass Eurypterida (extinct) •C lass Arachnida- Most are terrestrial (invaded from aquatic)- Exoskeleton is waxy to reduce water loss- Respiration is by means of specially adapted book lungs or trachea- Unsegmented prosoma is covered dorsally by a solid carapaceOrder Scorpiones: scorpionsOrder Araneae: spidersOrder Opiliones: harvestmen and daddy longlegsOrder Acari: mites and ticks •C lass Acarina- Hydracarina to include only the water mites- Found in terrestrial habitats but most are found immediately around freshwater systems- Some are parasiticSubphylum Crustacea- Only large subphylum of arthropods which is primarily aquatic- Most species are marine- Five pairs of appendages- First pair of antennae/antennules- Second pair of antennae- Mandibles- First maxillae (used for food manipulation)- Second maxillae (used for food manipulation)- Labium and labrum sandwich mouth- Protopodite (appendage base) composed of Coxopodite,Basobodite- This is followed by an inner endopodite and an outer exopodite- Biramous appendages- Cuticle is usually calcified- Has tegumental glands and chromatophores- Most crustaceans are essentially crawlers although many have retained some swimming ability- Many are also known to be burrowers- Many have well developed anterior trunk appendages adapted for predation or picking up food and maxillae/mandibles for holding and biting- Others are filter feeders- The foregut may be a simple tubular esophagus or it may be enlarged, forming a stomach-like region with walls bearing opposing chitinous ridges, dentacles, or other calcareous structures- One pair of ceca has usually developed into a digestive gland or hepatopancreaso Simple hindgut opening at the anus- Most have a heart/heart-like structure- May be long and tube-like or a complex spherical vesicle- Arterial system- Respiration typically with gills- Excretory organs are paired and composed of an end sac and an excretory tubule which empties into an excretory vesicle/bladder- Ammonia is nitrogenous waste product- Excretory organs are located adjacent to antennae or second maxillary segments- Nephrocytes are commonly found in the gill axes and in bases of legs- Highly developed nervous system including eyes, statocysts, tactile receptors, and chemoreceptors- Usually two compound eyes present- May be stalked- Mostly dioecious but some are hermaphroditic- Gonads are paired, elongated organs situated dorsally in the thorax and/or abdomen- Position of gonopores varies- Copulation is typical- Males typically have specialized modifications for grasping femaleso Egg brooding is common- May be attached to certain appendages, placed in brood chambers, or retained in a sac- Earliest larval stage is naupilus larvaClass Branchiopoda- Generally small (a few mm long)- Almost exclusively freshwater- All have trunk appendages that are flattened leaf-like structureso Usually adapted for filter feeding and sometimes swimming- Exopodite and endopodite are single flattened lobe structures with setae along the margin- Coxa has a flattened epipodite which serves as gills ("gill feet")- Typically first antennae and second maxillae are reduced- Anal segment usually supports a pair of large terminal processes called cercopods- Most are filter feedersOrder Anostraca: fairy shrimp- Elongated trunk with 20 or more segments- 11 to 19 segments bear appendages- "Without carapace"- Stalked compound eyes- Swim upside downOrder Notostraca: tadpole shrimp- Shield-like carapace which covers the head and anterior half of the trunk- Second antennae are very reduced- Compound eyes or sessile- Long flexible abdomen with up to 70 pairs of appendages- Most posterior segment is the telson which supports two long caudal processes, the furcaeOrder Diplostraca: cladocera- Laterally compressed- Body is at least partially enclosed in a clam-like bivalve carapace- Only cladocerans inhabit large streams, large ponds, and lakesSuborder Conchostraca: clam shrimp- Look like a clam- Body is nearly/completely enclosed in carapace- Two valves closed by transverse adductor muscles- 10-30 trunk segments, each with a pair of appendages- Second antennae are well developed- Specialized antennae used for locomotion- Biramous- Setose- Sessile compound eyes Suborder Cladocera: water fleas- Daphnia(Genus)- Trunk is enclosed in the carapace but head is not- Posteriorly carapace forms an apical spine- Generally head projects ventrally and somewhat posteriorly, giving it a beak-like appearance- No obvious external segmentation- 5-6 trunk appendage pairs- Postabdomen (tip of trunk) is ventrally turned and support specialized claws and spines for cleaning the carapace- Swim using highly developed second antennaeClass Ostracoda- Body completely enclosed by carapace- Resemble little clams-