Reproduction & Development Amixis Amixis by fragmentation Nemertean may aestivate within a mucous cyst. Alternating Life Cycles Obelia colonial proliferation & gonochoristic amphimixis Marine no diapause Alternating Life Cycles Hydra Clonal proliferation & gonochoristic amphimixis Note: diapause as egg (c) Alternating Life Cycles Crustacean apomixis & amphimixis Diapause as diploid embryo in ephippium Alternating Life Cycles Rotifer: apomixis & arrhenotoky Diapause as diploid egg Alternating Life Cycles Bryozoan colonial proliferation, amphimixis or autogamy, & clonal proliferation Diapause as multicellular statoblast Alternating Life Cycles Scyphozoan Aurelia sp. Clonal proliferation & gonochoristic amphimixis Marine no diapause Alternating Life Cycles Aphid: apomixis & gonochoristic amphimixis Diapause as diploid egg Parasite Life Cycles Trematode human lung fluke Gonochoristic amphimixis & Polyembryony at several stages Annelida - Epitoky Some Polychaetes produce bags of gametes for mixis either by conversion of body part or amictic budding Coordinated seasonal release Annelid Mixis Simultaneous Hermaphrodites with cross-fertilization Cocoon formation An Hermaphroditic Reproductive Tract : Pallifera sp. alb = albumin gland, at = atrium, bc = bursa copulatrix, bcp = bursa peduncle, chd = common hermaphroditic duct, fov = free oviduct, ovt = ovotestis, p = penis, spov = spermioviduct, vd = vas deferens copyright 2007 J.W. Atkinson First TEM pictures of sperm entering egg 1960s by Colwin & Colwin using the polychaete, Hydroides TEM Acrosome reaction sea urchin, Arbacia Developmental Patterns I Developmental Patterns II Developmental Patterns III Mesoderm formation Coelom formation - enterocoely Unique Development: a triclad turbellarian (some critters dont fit the patterns) Developmental Control: mosaic vs regulative Determination of cell fate occurs before differentiation Early Experimental Embryology - Dichotomy Mosaic vs Regulative early (determinate egg?) late (Indeterminate egg?) Prospective Potency = prospective fate PP> pf pf laid down in egg pf results from cell interactions elimination of cell loss of structure elimination of cell adjustment Protostome vs Deuterostome Later Experimental Work Breakdown of Dichotomy cell interactions also important localized cytoplasmic factors 4d cell gradients of determinants tissue & organism exceptions Current View: Differences in timing of events & stability of Bauplans, i.e. no longer fits the protostome/deuterostome split Octopus: Direct Development pvm = pervitelline membrane, ar = arm, est = eye stalk, mn = mantel, oc = optic lobe, y = yolk f = funnel Insect Larvae & Metamorphosis Hemimetabolous Incomplete metamorphosis Insect Larvae & Metamorphosis Holometabolous: Complete Metamorphosis Imaginal Discs Nemertea: Pallidium larva Metamorphosis Sea Urchin: Pluteus Larva Metamorphosis Urochordate: Adult Cell Turnover Hydra from stem cells Growth: control in arthropods Drosophila hox gene expression