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Biosc 41 Announcements 10/15 Quick Platyhelminthes Review

v What type of symmetry do animals in Phylum v Quiz today- Phyla Platyhelminthes and Mollusca Platyhelminthes have? v v Lecture- Phylum Arthropoda Digestive system: mouth only (protostomes) v How does gas exchange take place? v Lab- Phylum Arthropoda v What are protonephridia for? v What is the class of free-living flatworms? An v Mon’s lecture will finish any arthropod info we don’t get to example? today, have arthropod quiz, and do an exam review activity v What are the classes of parasitic flatworms? Example? v Mon’s lab will finish arthropod lab material (+ crayfish dissection)

Quick Mollusca Review Quick Mollusca Review v Features and structures universal amongst molluscs: v Four major classes: § Mantle- secretes shell in shelled molluscs; sometimes § Class Polyplacophora- Chitons portions of mantle form siphon(s) § Class Gastropoda- snails, nudibranchs, slugs § Foot- contains sensory cells; adapted in various ways in § Life cycle includes trochophore & veliger larvae different classes § Veliger stage involves torsion § Visceral mass- internal organs consistent between classes, but arranged in different orientations § Class Bivalvia- clams, oysters, mussels § Life cycle includes trochophore & veliger larvae § Circulatory system includes heart and is open in all but cephalopods (which have a closed circulatory system) § Class Cephalopoda- squid, octopus, cuttlefish, nautilus § Nervous system includes nerve cords and centralized brain tissue § Mantle has been modified to include a siphon for locomotion § Digestive system includes radula, well-developed digestive gland, and “complete gut” § Foot has been modified into tentacles § Heart and kidneys function as excretory system § Closed circulation and complex brain

Quick Mollusca Review Quiz 5

v What is a possible adverse effect of suspension feeding? 1. What is the class of free-living flatworms? And an example?

v Molluscs are the animal group with the largest number of 2. What are the two classes of parasitic flatworms? And an recent extinctions example of each?

v What features distinguish bivalves from brachiopods (Phylum 3. Identify 3 of the 4 major classes of Phylum Mollusca Brachiopoda)?

4. What are three features distinguishing bivalve molluscs from brachiopods (Phylum Brachiopoda)?

5. What is a possible adverse effect of suspension feeding?

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More Relationships…

An Introduction to the Invertebrates, Arthropods, Part One

Reference: Chapter 33

"Don't accept the chauvinistic tradition that labels our era the age of mammals. This is the age of arthropods. They outnumber us by any criterion – by species, by individuals, by prospects for evolutionary continuation." Stephen Jay Gould, 1988

Arthropod = “jointed leg” Arthropod Origins

v Eumetazoan protostome, bilateral symmetry, triploblastic, v The arthropod body plan consists of a segmented coelomate (mostly) body, hard exoskeleton, and jointed appendages v Defining characteristics v This body plan dates to the Cambrian explosion § Segmented body (535–525 million years ago) § Some segments are fused by tagmosis into tagmata v Early arthropods show little variation from segment § Exoskeleton made of chitin to segment § Secreted by epidermis § Molting (Ecdysis à Ecdysozoa) § Exoskeleton shed regularly during life or only during larval development § No cilia in larvae or adults v Most successful in terms of diversity and sheer numbers § >1,000,000 species!

Phylum Arthropoda – general body plan Tagmosis allows for specialization & diversity

v Body divided into segments (somites) v Diversity of body form possible because of specialization of § Regionally fused into specialized groups by tagmosis (i.e., segments, regions and appendages 5 segments form head) v Tagmosis = segments grouped together § Internal cavity à hemocoel (not coelom!) § Specialized for particular functions for greater efficiency v Head, thorax and abdomen are tagmata § No internal segmentation (no septa – contrast w/annelids) § Regions specialized for performing different tasks v Each body segment has a pair of jointed appendages

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Exoskeleton Structure The Arthropod Cuticle 1 4 v Cuticle forms well-developed exoskeleton made up of plates (sclerites) § Growth by ecdysis (hormone-induced molting) v Epidermis is a single layer of epithelial cells that secrete the cuticle in layers § Outer layer = epicuticle, with water-repellant hydrophobic layers § Inner layer = procuticle, protein & chitin § Procuticle is hardened by 1. Sclerotization = cross-linking of proteins into 3D matrix 2. Mineralization (in crustaceans) = depositing calcium carbonate in procuticle (i.e., crab shell)

Molting The pros and cons of the arthropod exoskeleton

v Stages between molts are termed instars v Pros § This is when actual tissue growth occurs, although there’s no size 1. Provides protection; hard covering over muscles & viscera increase until after the molt 2. Facilitates osmoregulation in terrestrial environment (less § Usually applies to immature stages water loss through epidermis) v Frequency of molting is under hormonal control (ecdysone) 3. No need for hydrostatic skeleton, so body plan could v Cuticle is weakened enzymatically, then animal crawls out diversify v After molting, animal sucks in air/water to inflate new 4. Better leverage than endoskeleton (or no skeleton) for cuticle which then hardens moving muscles attached to limbs v Cons 1. Growth must proceed through a series of molts 2. Chitin exoskeleton is heavy – constraint on size

Arthropod circulation Arthropod Respiration

v Open circulatory system v Varies between groups but usually by gills in aquatic habitats § Hemolymph moves through hemocoel, and has and a tracheal system in terrestrial arthropods amebocytes, pigments, and sometimes clotting factors § The tracheal system is composed of tubes that distribute § Muscular heart required since rigid exoskeleton prevents air throughout the body body movements from moving hemolymph § Some arthropods have a specialized lung-like structure called a book lung or book gill § Special chamber with platelike structures § Enhanced surface area facilitates rapid exchange of

CO2 and O2 § Diffusion of gases across thin areas of the cuticle also contributes to respiration

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Arthropod Osmoregulation and Waste Excretion Arthropod Nervous System

v Reuptake of salts and nutrients v “Brain” is 2-3 ganglia with v Antennal and maxillary glands in crustaceans specific functions § Produce urine; ammonia also excreted from gills v Ganglionated ventral nerve cord v Malpighian tubules in arachnids and insects v Sense organs (sensilla) protrude out of cuticle § Blind tubes extend into hemocoel and empty into gut v Membranous drums (“ears”) § Produce uric acid which is passed through the anus v § Solid matter may also be passed through the anus Chemoreceptors with thin cuticle

Arthropod Vision Arthropod Digestive System

v Complete, with regional specialization • Simple ocelli • Complex lensed ocelli § Foregut - food intake, transport, storage, mechanical • Compound eyes made of ommatidia digestion (jaws, pharynx, gizzard) § Midgut - extracellular digestion, nutrient uptake (cecae, digestive gland, hepatopancreas) § Hindgut - excretion of undigested material, water reabsorption

Arthropod Locomotion Arthropod locomotion

v Striated muscle v Jointed appendages (limbs) + specialized muscles to move the limb pieces (podites) § Exoskeleton used as attachment point for muscles § Extrinsic muscles connect to body wall v Muscles anchor on inside of cuticle § Intrinsic muscles are contained entirely inside the limb § Connect into the jointed appendages on each segment v Ancestral condition, found in crustaceans, is to have biramous limbs (each limb has 2 branches)

Uniramous (1 branch) Biramous - insects - crustaceans

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Diversity of Arthropod legs Arthropod Taxonomy

Seven Subphyla: 1. Trilobites (extinct since Paleozoic) 2. Onychophora (velvet worms) 3. Tartigrada (water bears) 4. Crustacea (crabs, lobsters, shrimp) 5. Chelicerata (spiders, horseshoe crabs, pycnogonids) 6. Myriapoda (centipedes, millipedes) 7. Hexapoda (Insects)

Subphylum Trilobitomorpha (Extinct) Subphylum Onychophora 2 8 v Onychophora – “nail bearers” or “velvet worms” § 1-3 cm Cephalon v Transitional group within the Ecdysozoa – possess some features not characteristic of arthropods Thorax § Pseudocoelomate § Soft cuticle – no exoskeleton! Pygidium § No jointed appendages § Legs are hollow – “stub legs” v Found in litter layer & decaying logs § Prey on small worms, arthropods Most common group of fossil arthropods - Once abundant in oceans - Disappeared by Paleozoic (345 million yr ago)

Subphylum Tartigrada Subphylum Crustacea

v Most occur in marine and freshwater environments v “Water bears” or “moss piglets” v External Features: § About 0.5 mm § Distinguishing feature: only arthropods with 2 pairs of § Terrestrial and aquatic habitats antennae v true extremophiles: can survive § Body of 3 tagmata: head, thorax, abdomen § Wide temperature extremes (-80C to >100C) § Cephalic shield or carapace present to protect dorsum § Ionizing radiation § Mandibles, modified limbs, act as jaws; 2 pairs of § Outer space! (for a while) antennae v Capable of anhydrobiosis § Limbs are biramous (2 forks) § Able to desiccate to <3% water and § “Gills” are actually legs modified for gas exchange stay that way for >10 years

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Subphylum Crustacea Generalized Crustacean Body Plan

Marine arthropods video (~10 min): http://shapeoflife.org/video/phyla/marine-arthropods- successful-design Biramous leg

Subphylum Crustacea- Internal Features Subphylum Crustacea – Internal Features v Hemocoel v Respiratory System § Major body cavity; filled with hemolymph § Very small crustaceans conduct gas exchange across thin § Coelom restricted to compartment around gonads areas of the cuticle v Muscular System § Larger crustaceans have gills § Striated muscles form a large part of the body § Capable of fast, strong movement

Subphylum Crustacea – Internal Features Subphylum Crustacea – Internal Features v Circulatory system Excretory System

§ Open - no system of veins to separate blood from v Nitrogenous wastes (mostly interstitial fluid ammonia) excreted across thin areas of cuticle in the § Hemolymph exits heart through arteries and passes through gills hemocoel and gills to return to the heart via sinuses v Antennal or Maxillary Gland § Hemolymph may be (“green glands”) colorless, reddish, or v Excrete urine bluish v Function is to regulate ionic § Contains ameboid cells and osmotic composition of that may help prevent body fluids clotting

§ Hemocyanin and/or hemoglobin are respiratory pigments

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Subphylum Crustacea – Internal Features Subphylum Crustacea – Internal Features

Digestive System Nervous and Sensory Systems v Complete gut § Fused ganglia form brain v Stomach often consists of more than one chamber § Double ventral nerve cord has a pair of ganglia for each v Gastric stomach – includes “gastric mill” for grinding somite (segment) v Pyloric stomach § Tactile hairs on the body § Chemical sensing of taste and smell occurs in hairs on antennae and mouth § Statocysts controls balance § Compound eyes; often on stalks

Subphylum Crustacea – Reproduction & Life Cycles Classes of Subphylum Crustacea v Diverse reproductive modes v Branchiopoda & Ostracoda § Barnacles are hermaphrodites, but cross-fertilize v § Some ostracods reproduce parthenogenetically (eggs don’t require Maxillopoda (Copepods, Barnacles) fertilization) v Malacostraca (Isopods, Decapods [Crab, shrimp, § Most crustaceans brood their eggs lobsters]) v Most common life cycle involves metamorphosis

§ Egg hatches into nauplius larva, which molt and goes through several instars

§ Segments and appendages are added in successive molts

Classes of Subphylum Crustacea - Branchiopoda & Ostracoda Class Maxillopoda v Small, aquatic or marine crustaceans v Subclass Copepoda § § Important in food Copepods form important links in webs aquatic food webs § Many have a bivalve v Subclass Cirripedia carapace that § Barnacles are a group of mostly encloses the body sessile crustaceans § Example – Daphnia § But start life as a motile, (Class Branchiopoda) nauplius larva § They have a cuticle that is hardened into a shell § Hermaphroditic – one of the few arthropods that are

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Class Malacostraca (shrimp, lobsters, crabs, isopods) Class Malacostraca – Order Isopoda (“same feet”) v Largest class of crustacean – and most diverse v Terrestrial, marine and freshwater species § Over 20,000 species worldwide § Terrestrial species are the only crustacean to have § Ecologically and commercially important become fully terrestrial (“pill bugs”) § Restricted to moist environments § Marine species include a few bizarre parasites of fish- and very large species!

Class Malacostraca – Order Decapoda (“10 feet”) Class Malacostraca – Order Stomatopoda v Crabs, shrimp, lobsters v Mantis Shrimp v One or more pairs of § Voracious predators walking legs modified to § Some species are ambush form pincers (chelae) hunters and snag prey with v Many species have bright raptorial limbs coloration and/or § Others have forelimbs camouflage modified into clubs that carry a powerful concussive force

Subphylum Chelicerata Class Pycnogonida: Sea spiders ~ 65,000 spp.

v Body of 2 tagmata: cephalothorax + abdomen v Marine, intertidal to abyssal depths; worldwide distribution v 1st pair of appendages = chelicerae (look like fangs) § About 1,000 species v No antennae v Benthic, live on seaweeds or other invertebrates st v Gas exchange by book gills, book lungs or tracheae v Sucking proboscis on 1 head segment used to feed on soft- v Separate sexes bodied invertebrates v Classes: v Males: brood eggs on ovigers, special leg appendages § Pycnogonida (sea spiders) v Females: hollow legs filled with eggs § Merostomata (horseshoe crabs) § Arachnida (spiders)

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Class Merostomata: Horseshoe crabs Class Arachnida: Scorpions, spiders, mites, ticks

v Arachnids have an abdomen and a cephalothorax, v Inhabit shallow marine which has six pairs of appendages: the chelicerae, waters the pedipalps, and four pairs of walking legs v Burrow just under sand surface, prey on buried v Gas exchange by trachaea or book lungs animals like bivalves v No compound eyes but have ocelli (often multiple) v Small chelicerae v v Limited distribution: Many spiders produce silk, a liquid protein, from Limulus polyphemus specialized abdominal glands restricted to east coast of North America v Distinctive telson, or tail spine

Figure 33.33 Subphylum Myriopoda = “lots of legs”

Stomach Intestine v Myriapods are terrestrial, and have jaw-like mandibles Heart Brain v Classes: Digestive gland § Diplopoda (millipedes)- have two legs per segment on Eyes each side; slow but powerful

Ovary Poison gland

§ Anus Chilopoda (centipedes)- have one leg per segment on Book lung each side; fast but not as powerful Spinnerets Gonopore Chelicera Pedipalp (exit for eggs) Sperm Silk gland receptacle

Class Diplopoda - Millipedes Class Chilopoda - Centipedes

v Eat decaying leaves and plant matter v Carnivores v Have many legs, with two pairs per trunk segment v One pair of legs per trunk segment v Non-venomous, but some can secrete noxious chemicals v Most are venomous

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Figure 33.35 Subphylum Hexapoda = 6 legs- Insects and relatives Abdomen Thorax Head Compound eye v More species than all other forms of life combined § Live in almost every terrestrial habitat and in fresh water Antennae § Internal anatomy includes several complex organ systems v Insects diversified several times § Following the evolution of flight Heart Dorsal artery Crop Cerebral § Adaptation to feeding on gymnosperms Anus ganglion § Expansion of angiosperms v Insect and plant diversity declined during the Vagina Cretaceous extinction, but has been increasing in Malpighian the 65 million years since tubules Ovary Tracheal tubes Nerve cords Mouthparts

Insect Success: the power of flight Insect Development

v Flight is one key to the great success of insects v Many insects undergo metamorphosis during their v An animal that can fly can escape predators, find development food, and disperse to new habitats much faster than v Incomplete (hemimetabolous) metamorphosis organisms that can only crawl § Young are called nymphs § Resemble adults but smaller and go through a series of molts until they reach full size v Complete (holometabolous) metamorphosis § Larval stages known by such names as maggot, grub, or caterpillar § Larval stage looks entirely different from adult stage § Usually involves some sort of pupation

Insect Development Figure 33.37

Hemimetabolous - insects hatch looking much like adults. Nymphs gradually attain adult form.

Holometabolous - young very different from adults (a) Larva (caterpillar) (b) Pupa Pupal stage metamorhosis into adult (c) Later-stage pupa (d) Emerging adult

(e) Adult

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Insect Life Habit Summary of Terrestrial Arthropods

v Most insects have separate sexes and reproduce sexually § Individuals find and recognize members of their own species by bright colors, sound, or odors v Insects may be predators, herbivores, microbivores, parasites § Insect parasites that prey on other insects are referred to parasitoids, because they kill their host v Some insects are beneficial as pollinators, while others are harmful as carriers of diseases, or pests of crops v Ants, bees and termites have evolved eusociality § Decentralised, self-organized colony with division of labor and physical differences between castes Terrestrial arthropods video (~14 min): http://shapeoflife.org/video/phyla/terrestrial-arthropods- v Insects are classified into more than 30 orders conquerors

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