Class Anostraca Fairy and brine shrimp 27 trunk segments; only anterior segments (thorax) with appendages (phyllopoda) Thorax and abdomen distinct only by presence of appendages

Class Branchiopoda Water fleas Clear separation of tagmata reduced; head and trunk Mouth simple Thoracic appendages adapted for swimming; Abdomen lacks appendages Apparent segmentation lost Body shape is different from carapace Microscope slide of Daphnia

Class Malacostraca Large group of Crustacea (>20,000 species) See intro p.625 of lecture text for key features (Fig 19-19) General theme –3 tagmata –Biramous, uniramous, biramous

Order Stomatopoda Mantis shrimp Depressed body 3 tagmata Shield-like carapace Raptorial 1 st pair thoracic appendages First antennae triramous P. 627

Order Decapoda Largest order of Malacostraca Both antennae biramous 2 tagmata (cephalothorax and abdomen) Biramous, uniramous, biramous. Modification of first periopod in many Mouthparts 6, thoracic appendanges 5 Divergence of mouthparts varies

Order Mysidacea Shrimp-like but not decapods because retain many primitive characteristics Head with 3 fused thoracic segments Carapace onlyy attached 1 st – 3 rd thoracic segments but looks like cephalothorax Tagmata not fused

O. Amphipoda Compressed body No carapace 3 tagmata 1 – 2 thoracic segments fused to head (8 thoracic segments) Gnathopods are first two pair thoracic appendages not fused to head 6 segments Ab split into two parts

O. Isopoda 3 tagmata Head and 1 st thoracic segment fused Depressed body The 7 thoracic appendages generally unspecialized (all look the same) Last Ab segment fused with telson (pleotelson) Remaining Ab segments (5) have biramous pleopods Biramous, uniramous, biramous preserved specimens

Class Copepoda Body tapers anterior to posterior Short trunk (Th + Ab) 10 or fewer segments Head includes 3 fused thoracic segments Ab 4 segments, no appendage Posterior extensions rami, not uropods as in Malacostraca 1 st antennae variabe in size, can be long On slides

Class Cirripedia

Order d