BIOL1263 Lecture 6 Echinodermata and Arthropoda I crustaceans 2024.pdf

BIOL1263 Living Organisms II 6. Echinodermata; Jointed exoskeleton and legs: Arthropoda Phylum Echinodermata: Deuterostomes; all marine; water vascular system, tube feet, pedicellariae; pentaradial. Classes Echinoidea (urchins); Crinoidea (crinoids); Holothuroidea (sea cucumbers);...

BIOL1263 Living Organisms II 6. Echinodermata; Jointed exoskeleton and legs: Arthropoda Phylum Echinodermata: Deuterostomes; all marine; water vascular system, tube feet, pedicellariae; pentaradial. Classes Echinoidea (urchins); Crinoidea (crinoids); Holothuroidea (sea cucumbers); Asteroidea (starfish); Ophiuroidea (brittle stars); plus many extinct. Arthropods: Jointed exoskeleton and appendages - advantages of a hard shell and fast and precise movements; complex muscular system Hard cuticle with chitin Fusion of segments (tagmosis) into body regions, specialisation of appendages Open circulation of haemolymph through haemocoel Simple and compound eyes Complete digestive system Respiration by body surface Bilateral symmetry Dorsal brain connected to ventral ganglia Growth with ecdysis (moulting) 1 Phylum Echinodermata - convergent with molluscs Scraping mouthparts for feeding on algae – Aristotle’s lantern https://twitter.com/StantonBelford/status/1314920230465003522 Hard calcareous shell or test – made of small plates or spicules Deuterostomes See video on myelearning 2 3  Phylum Echinodermata – basic structure Larva T.S. arm Water vascular system (blue) 4 Echinoderm features Tube feet – locomotion Pedicellariae – defence 5 Class Echinoidea – sea urchins Tripneustes ventricosus - West Indian sea egg Grazing herbivore https://www.inaturalist.org /observations/31703022 Dendraster excentricus Sand dollar Detritus feeder 6 7 Class Crinoidea – crinoids – normally sessile Sea lilies Deep sea stalked crinoids Feather star https://www.inaturalist.or Unstalked crinoid g/observations/73186792 https://www.youtube.com/watch?v=rRej1VKDgcE8 9 Class Holothuroidea – Sea Cucumbers Actinopyga agassizi West Indian sea cucumber Aboral surface - anus Oral surface – mouth Mouth Anus Deep sea holothurian “sea pig” 10 https://www.inaturalist.org/observations/13079575 11 Class Asteroidea - Starfish Oreaster reticulatus West Indian Sea Star Starfish extruding stomach https://www.inaturalist.org/observations/9861980 Pisaster sp. eating clam – pulling valves apart with tube feet 12 13 Class Ophiuroidea – Brittle stars Organs in central disk, unlike in starfish https://www.inaturalist.or g/observations/9891811 14 15 Arthropoda Ectydozoan Protostomes Ancestral forms with similar biramous (two-branched) appendages on each segment Evolved in the sea; the most basic living group is the crustaceans, with planktonic nauplius larvae and cuticle with calcium carbonate Crustaceans are paraphyletic; Classes Malacostraca (crabs and woodlice), Maxillopoda (barnacles), Branchiopoda (water fleas) 16  Ecdysozoan phylogeny Phylum Arthropoda; 1.5 million described insect species; may be 10 or 30 million Phylum Onychophora – velvet worms – precursor? Macroperipatus torquatus – endemic to Trinidad https://www.inaturalist.org/observations/22685804 Flexible cuticle 18 19 Ancient onychophoran – Aysheaia sp. From the Burgess Shale (mid-Cambrian marine sediments, 508 mya; many soft-bodied fossils) Columnar legs or lobopods, and a pair of antennae 20  Modern onychophoran – specialised terrestrial predator Lobopods, antennae, oral papillae Live birth Spraying sticky secretion from oral papillae 21 Phylum Arthropoda – exoskeleton of body and legs Hard cuticle with chitin, a modified polysaccharide including nitrogen (glucosamine units), also in fungal cell walls. Segmental muscles inside body and legs. Separate control for complex movements. 22 Cuticle structure Biomineralisation 23 Ecdysis (moulting) in arthropods 24 Photo Dr Alex Wild https://twitter.com/Myrmecos/status/1355923535823331331 25 General anatomy of an arthropod 26 Haemocoel in arthropod and mollusc Haemolymph is pumped by the heart along vessels, then flows through the haemocoel. Re-enters heart by pores (ostia) in arthropods, and vessels (veins) in molluscs. Both phyla have the copper- based respiratory pigment haemocyanin (cf haemoglobin in vertebrates). 27  Simple eye Arthropod eyes Compound eye – ommatidia 28  Arthropod chemical and touch senses Insect antenna types Mechanoreceptors 29 Phylum Arthropoda – taxa (subphyla) and main classes Crustaceans Class Branchiopoda Water fleas Class Malacostraca Shrimps, crabs, woodlice Class Maxillopoda Barnacles Chelicerates Class Arachnida Spiders, scorpions, mites, ticks Class Merostomata Horseshoe crabs Myriapods Class Chilopoda Centipedes Class Diplopoda Millipedes Hexapods Class Entognatha Springtails Class Insecta Insects 30 Tagmosis in arthropods Tagma (pl. tagmata) = a region of the body, formed by fusion of segments. red = antennae black = mouthparts purple = claws green = walking legs orange = swimmerets Diagrammatic – segment numbers vary 31 Body plan of a shrimp Biramous appendage 32 Crustacean larvae Nauplius larva of a barnacle Zoea larva of a crab Little competition with adult forms 33 Class Malacostraca, Order Decapoda – lobsters and shrimps Panulirus argus Stenopus hispidus Caribbean spiny lobster Red-banded coral shrimp Antennae defensive Cleaner symbiosis Human food source 34  Class Malacostraca, Order Decapoda – crabs Cardisoma guanhumi - Blue land crab Important fishery https://www.inaturalist.org/observations/9142260 Abdomen Gecarcoidea natalis Christmas Island crab https://www.youtube.com /watch?v=gR02_MFpOYY 35  Class Malacostraca, Order Isopoda – woodlice Oniscus sp. Woodlouse, pillbug or sowbug Terrestrial, dorso-ventrally flattened Armadillidium sp. with juveniles Female carrying eggs https://www.inaturalist.org/observations/91584767 36 37 38 Class Branchiopoda (closer to Hexapods?) – brine shrimps Multiple similar legs, swimming and filter feeding Lack carapace Artemia salina Hypersaline water Fish food Toxicity tests Radiation tests in space 39 Class Branchiopoda – water fleas Swim with enlarged biramous second antenna Daphnia sp. Freshwater Fish food Pollution indicator 40 Class Maxillopoda – barnacles Luis Agassiz: “A barnacle is nothing more than a shrimp-like animal standing on its head in a limestone house kicking food into its mouth” 41 Class Maxillopoda – barnacles Chthamalus proteus Caribbean barnacle Can slow ship speeds by 30-40% Lepas sp. – Goose barnacle Myth of the barnacle goose 42