Animal & Structure Exam #2

Phylum Arthropoda

• Account for 80% of all animal species

• 1.2–10 million different species!

• Beetles: 300,000–400,000 sp. Butterflies: 110,000–120,000 sp. Flies: 90,000–150,000 sp. Ants, bees, wasps: 100,000–125,000 sp. Arachnids: 100,000 sp. Crustaceans: 67,000 sp.

Exoskeleton, segmented bodies and repeated appendages, jointed appendages, efficient respiration, highly developed sensory organs, efficient and novel waste removal system

What are the six important characteristics of Arthropoda?

Phylum Arthropoda

What Phylum has these type of appendages:

• appendages were originally biramous, meaning they were forked

• Each appendage had two parts: exopod and endopod

• Most extant species have uniramous appendages

• Crustaceans have biramous

exoskeleton

All arthropods have a hard _____.

What structure does this describe:

• The epidermis secretes the hard cuticle (i.e. exoskeleton) in three layers

• Endocuticle: mostly layers of chitin (a longchain polysaccharide) and proteins

• Exocuticle: biomineralized, hardened with calcium carbonate (marine)

• Epicuticle: softer, contains lipids

• Contains sensory bristles called setae

• The epidermis secretes the hard cuticle (i.e. exoskeleton) in three layers

provides protection for body, places for muscle attachment

What are the advantages of the exoskeleton?

prevents growth

What are the disadvantages of the exoskeleton?

ecdysis

What does this describe:

• solves the problem of preventing growth by motling the exoskeleton and grow a new one

• During molting, the epidermis releases enzymes that digest the endocuticle and thus detach the old cuticle

• The epidermis then secretes a new epicuticle and exocuticle

• The animal takes in air or water to swell the body, which cracks the old cuticle

• Next, the animal leaves the old cuticle and is soft bodied

• The animal stretches the new cuticle and hardens the exocuticle by adding minerals (or the cuticle dries in air)

• Last, the animal secretes a new endocuticle

how ecdysis occurs

What does this describe:

• The epidermis secretes digestive enzymes which dissolve the Endocuticle

• This creates a separation between the animals Epidermis and the cuticle

• The epidermis begins secreting a new Epicuticle and Exocuticle

• The animal wriggles out of the old exoskeleton, leaving it behind

• The epidermis begins secreting a new Epicuticle and Exocuticle

• The animal wriggles out of the old exoskeleton, leaving it behind

• Lastly, after swelling the body with water or air, the animal secretes a new Endocuticle

Cambrian explosion

What does this describe:

• Starting about 542 MYA and lasted for 20–25 MY, most animal phyla first evolved • A period of rapid evolutionary change

• No single hypothesis for why this happened when it happened

• Perhaps due to increases in air O2

• Earth developed an ozone layer, allowed life on land • Arms race of predators and prey

• By 540 MYA, O2 levels had risen to ~10% of modern day

• Complex, active animals require lots of O2!

subphylum trilobita

What subphylum is this:

• trilobites

• Among the most successful animal groups

• Three lobed body (tri-lob-ite)

• Emerged during the Cambrian Explosion and went extinct 250 MYA

• 17,000 described species from fossils

• Filled many niches: predators, scavengers, filter feeders

• Precursor to the modern arthropods

  • Had a hard exoskeleton

  • Had compound eyes with good vision

  • Had jointed, articulated appendage

  • Had paired antennae

• Went extinct along with 95% of all marine life during the mass Permian extinction

• Cause of the extinction event is not known (potentially an asteroid impact?)

• Although all trilobites are extinct, they were dominant for longer than mammals have existed!

Subphylum Chelicerata

What subphylum is this:

• chelicerates

• includes Merostomata (horseshow crabs) and arachnida (spiders, scorpions, ticks)

• Six pairs of cephalothoracic appendages

  • 1 pair of chelicerae

  • 1 pair of pedipalps

  • 4 pairs of walking legs

  • Appendages are uniramous (unforked)

Class Merostomata

What class is this:

• In sunbphylum chelicerata

• horseshoe crabs

• Only 4 extant species (but 100s in the fossil record)

• Essentially unchanged from fossils

• Only chelicerates with compound eyes

• Obtain oxygen with book gills, have tons of surface area for obtaining O2 from water

• Feed on worms and mollusks, which they grind up using the gnathobases on each walking leg

Class Arachnida

What class is this:

• part of subphylum Chelicerata

• spiders, scorpions, ticks

• The vast majority of chelicerate species, more than 100,000 described

• All are predators

• Have basic chelicerate morphology, but appendages are highly modified in different groups

Order Araneae

What order is described:

• true spiders

• a part of class Arachnida and subphylum Chelicerata

• Chelicerae are modified into fangs which inject digestive enzymes into prey

• No chewing mouthparts needed, food is already digested

• Pedipalps use for manipulating prey or for reproduction

• Breathe with book lungs

• Connection between cephalothorax and abdomen is constricted

• Generally have 8 simple eyes with lens, rods, retina

• Mostly just see movement

• Multiple eyes provides a range of vision for around the body

• Vision is not the main sensory modality

• Body covered in sensory setae, primary method of sensation is vibration

• Most spiders spin webs in order to catch prey (primarily flying insects)

• Some species hunt prey actively (jumping spiders, fishing spiders)

• Spiders have very elaborate mating rituals

• Males are often much smaller than females

• Can involve dancing, vibrational communication, even cannibalism (females often eat males before/during/after mating

• Females lay egg sacks containing hundreds of young

Order Opiliones

What order is this:

• harvestmen

• a part of class Arachnida and subphylum Chelicerata

• Also known as “daddy long legs”

• More than 6,000 described specie

• Abdomen is segmented (different from spiders)

• As opposed to spiders, have a broad connection between cephalothorax and abdomen • Have two simple eyes

• Chelicerae are tiny pinchers, like in the horseshoe crab

• Males have elaborate reproductive strategies

Order Scorpionida

What order is this:

• true scorpions

• a part of class Arachnida and subphylum Chelicerata

• All predacious; short cephalothorax, long segmented abdomen • Pedipalps modified into claws for grasping prey

• Chelicerae modified for ripping prey apart

• Telson (tail segment of abdomen) modified to contain venom gland and stinger

• Females have extended parental care

• Give live birth to small numbers of young, have extended care

• Babies ride around on mom until at least their first molt

Order Amblypygi

What order is this:

• tailless whip scorpions

• a part of class Arachnida and subphylum Chelicerata

• Found in the tropics primarily

• Pedipalps modified into huge claws for grabbing prey

• First set of walking legs not used for walking, modified as sensory feelers

• Probe the environment with long sensory legs as they move around

Subphylum Myriapoda

What subphylum is this:

• Centipedes and Millipedes

• About 13,000 species, entirely terrestrial

• Similarities with Chelicerata • Two tagmata: head and trunk

• Appendages are uniramous (unforked)

• Differences from Chelicerata

• Have antennae

• Have spiracles that bring in air to tracheae

• Have mandibles and maxillae for manipulating food and chewing (not chelicerae)

• Mandibles are for chewing

• Two classes

  • Class Diplopoda: Millipedes

  • Class Chilopoda: Centipedes

class diplopoda

What class is this:

• subphylum myriapoda

• Millipedes

• Entirely herbivorous/scavenger group

• Two pair of legs per segment

• Generally slow moving

• Prefer moist, dark habitats

• Coil in a defensive posture

• Have rudimentary pseudocompound eyes

Class Chilopoda

What class is this:

• subphylum myriapoda

• Centipedes

• Entirely predatory group

• Have large, venomous jaws (maxillipeds) modified from first pair of legs (Chilo: “lip”, -poda: “feet/legs”)

• Single pair of legs per segment

• Generally fast moving, active hunters

• Final legs modified for tactile sensation

• Antennae primarily sense vibrations

• Most have sets of simple eyes, but some species have true compound eyes

Subphylum Crustacea

What subphylum is this:

• Crustaceans

• 67,000 described species

• Very economically important food source for humans (crab, lobster, shrimp, etc)

• Most are free-living marine species

• many freshwater and few terrestrial

• some sessile or parasitic

• many feed on detritus, are scavengers

• The only group of extant arthropods with biramous appendages (e.g., Trilobites had biramous appendages)

• Each appendage had two parts: exopod and endopod

• Most extant species have uniramous appendages

• Crustaceans often have lots of appendages that are highly modified for different uses

• Ancestrally biramous appendages still seen in swimmerets

• Two sets of antennae (one short, one long)

• Mandibles for feeding

• Two pairs of maxillae near mouth for feeding

• Three pairs of maxillipeds for handling food

• First walking legs (cheliped) generally modified for defense, has a large chela (claw)

• Cheliped: captures food (and defense)

• Maxillipeds: hold and crush food

• Mandibles and maxillae: shred food and place it in mouth

• cephalothorax and abdomen, same division as chelicerates

• In many, cephalothorax is covered in a solid carapace

• In crabs, the abdomen is tucked under body

Subphylum Crustacea

What subphylum has this respiration:

• Aquatic species (which is most crustaceans) breathe via gills

• Gills are generally attached to walking legs which allows gills to be moved in the water

• Important: Gills can only obtain O2 if water is passing over them!

Subphylum Crustacea

What subphylum has this excretion:

• Excretory organs are paired glands located in the head

• Waste products are mostly ammonia (easy to make if you are in water)

Subphylum Crustacea

What subphylum has this nervous system, devlopment, and reproduction:

• Have a simple brain

• Have a pair of ventral nerve cords

• Have a ganglion (where a bunch of nerves come together) in each segment

• Most decapods (shrimps, crabs, etc.) brood their eggs, providing parental care

• Most crustaceans are dioecious, except barnacles which are hermaphroditesLobsters and crayfish hold them on the swimmerets

Subphylum Crustacea

What subphylum is this:

• Maxillopoda : Barnacles, Copepods

• Malacostraca : Crabs, shrimp, lobster, krill, mantis shrimp

Class Maxillopoda

What class is this:

• subphylum crustacea

• Barnacles, Copepods

• Copepods are the dominant members of freshwater and marine zooplankton

• Copepods are very important as a food source for larger organisms – they fill a similar niche to rotifers

• Occur in nearly every aquatic habitat on earth

• Barnacles are sessile and use their modified legs (cirri) for feeding

• Cirri are biramous

• Cirri sweep plankton to the mouth for feeding (yet another sessile filter feeder!)

• Barnacles are hermaphrodites but avoid self-fertilization

• Can release sperm freely into the water (broadcast spawning)

• Can also inseminate other individuals directly

Class Malacostraca

What class is this:

• subphylum crustacea

• Crabs, shrimp, lobster, krill, mantis shrimp

• Largest and most diverse group, at least 40,000 extant species

• At least 16 extant orders (we will discuss 1)

• Order Decapoda: crabs, shrimp, lobster

Order Decapoda

What order is this:

• subphylum crsutacea, class malacostraca

• Crabs, shrimp, lobster

• ~15,000 species

• “Deca-”: 10, “-poda”: foot, refers to 5 pairs of walking legs

• Follow basic ancestral body plan of all crustaceans

• Many crabs can breathe air, but gills must still remain moist

Phylum Arthropoda

What phylum excretes waste like this:

• All metabolic processes produce nitrogenous waste, but you can make different types of wast

• Ammonia (NH3) is energetically easy to produce but is highly toxic to cells and cannot be concentrated in tissue

• Uric acid (C5H4N4O3) and urea (CO(NH2)2) are less toxic, but more complex and energetically difficult to make

• Type of waste depends on where you live

• Aquatic ONES (horseshoe crabs, copepods, crustaceans) make ammonia because they have access to unlimited water to dilute it and wash it away

• Terrestrial ONES (arachnids, millipedes, centipedes, insects) have Malpighian tubules to create urea or uric acid

Malpighian tubules

What does this describe:

• are slender tubes that shoot off of the end of the midgut

• Nitrogenous wastes and electrolytes (salts and minerals) are actively transported from the hemolymph into the tubules

• These products dump into the hindgut where urea or uric acid precipitates out and water is reabsorbed

• Excreted with feces as a semi-solid waste

Subphylum Hexapoda

What subphylum is this:

• 2 Classes

  • Entognatha : Collembola and other wingless critters

  • Insecta : Insects!

• Not just insects

• 3 tagmata: head, thorax, abdomen

• Uniramous appendages

• Hard exoskeleton made by cross-linking proteins (as opposed to adding calcium carbonate like in marine arthropods)

Class Entognatha

What class is this:

• subphylum hexapoda

• Wingless

• Mouthparts retracted within the head

• Wingless hexapods

• Ento-: within, -gnatha: jaw (mouthparts are pulled back inside head)

• About 4,500 total species, most are Collembola (aka springtails)

• Commonly found in soil and leaf litter; up to 100,000 ind/m2 of soil

• Very important for soil nutrient cycling

Class Insecta

What class is this:

• subphylum hexapoda

• insects

• ~1,000,000 named species, potentially as many as 10,000,000 species exist

• Most insects (88%) have an ecologically and morphologically unique larval stage (holometabolous development)

• Most fly (at least at some point during life)

• Recall that insects have 3 tagmata: Head, Thorax, and Abdomen

• Thorax further divided into three parts: pro-, meso-, and metathorax

• Each of the thoracic segments has one pair of legs

• Two sets of wings: on mesothorax (forewing) and metathorax (hindwing)

• Have compound eyes

• Made up of 1000s of individual hexagonal light perceiving units called ommatidia

• Generally adapted to bright or dim light

• Compound eyes have no ability to focus, likely see the world as if it were pixelated

• Many arthropods can see colors that we cannot, because they can see in UV

Class Insecta

What class has these feeding and digestion patterns:

• Most insects are designed for chewing

• The mandibles, maxillae, labium, palps and labrum all work together to chew food

• Many species have mouthparts adapted for certain functions • Mosquitos pierce and suck

• Butterflies have a long retractable tongue/proboscis

• Flies sponge up food

• A relatively simple digestive tract

• Foregut: mouth, esophagus, crop, proventriculus

• Midgut: stomach, gastric ceca

• Hindgut: intestines, rectum, anus

Class Insecta

What class has this type of development:

• Hemimetabolous development (Incomplete metamorphosis)

  • More ancestral form Go through several nymph stages en route to adult Larvae are like adults but lack wing

• Holometabolous development (Complete metamorphosis)

  • Evolved once Go through distinct larval stage, pupates, then is adult Larva is ecologically distinct

  • Extremely successful

  • Separates the niches of the larvae and adults, resulting in no competition and increased specialization

  • Egg hatches into a larva, which forms a pupa

  • Adult (imago) is the only stage with wings and sexual maturity

Class Insecta

What class has this respiration:

• No lungs; The trunk of the insect has spiracles which connect to tracheae, tubes which pipe air into body

• Because air is distributed through body by tracheae, no need for oxygen carrying molecules

• System works well for small animals, but not large ones (why most insects are small)

Class Insecta

What class has these wing features/flight:

• Wings are a thin membrane of chitin

• Wings contains thicker veins of chitin which strengthen them

• Wing vein patterns are generally identical within species but vary across species

• Insects fly in one of two ways: direct or indirect

• Muscles attach to inside of exoskeleton, provides tremendous strength

  • Paleoptera- Direct flight

  • Neoptera- Indirect flight

Paleoptera

What type of insect has these features (a part of class insecta)?

• direct flight

• Odonata and Ephemeroptera are only insects with direct flight

• Two sets of muscles alternate to move wings up and down on a fulcrum

• Central flight muscles contract to draw wings up

• central flight muscles contract to draw wings up

• Lateral flight muscles connected outside of hinge, contract to draw wings down

• Different muscles control each pair of wings (forewings and hindwings)

• Allows tremendous maneuverability due to independent movement of wings

• cannot fold wings

Neoptera

What type of insect has these features (a part of class insecta)?

• indirect flight → folding wings

• All other flying insects have indirect flight

• Muscles attached to thorax, not the wings

• One set of muscles contracts the thorax dorsoventrally to move wings up

• All other flying insects have indirect flight

• Muscles attached to thorax, not the wings

• Longitudinal muscles contract to expand thorax, pushing wings down

• Because wings beat with movement of the thorax, wings always beat together

• Muscle contraction not directly phase related to nerve impulses; muscles fire more rapidly than nerves

• “Modern” insects have wings that can fold behind them, over the abdomen

Class Insecta

What class has these communication/sensory system:

• Different senses are important on land compared to water

• Light is transmitted much better

• Sound is transmitted well at short ranges

• Chemical communication somewhat less important

• Vision is very important (compound eyes)

• Lots of species use bright coloration to warn predators or communicate with mates

• Other important senses: vibrational, auditory, and chemical (pheromones)

• Like other arthropods, insects have setae for sensing environmental vibrations

• Auditory signals are important for males to signal to females

• Males often make sounds by rubbing wings or abdominal segments together (stridulation)

• Grasshoppers, Crickets and Katydids (Orthoptera) have ridged wings modified for rubbing

• Cicadas have the loudest call of any insect, use an organ called the tymbal

• Contract abdominal segments to vibrate

Order Hymenoptera

What order is this:

• Class Insecta, Phylum Hexapoda

• Ants, bees, wasps

• Colonies generally consist of a queen (or several) and her daughters (workers)

• Queens suppress reproductive activity in the colony with pheromones

• Males produced rarely and only to create new colonies

• Ants lack wings except for reproductive males and females (alates)

• Why colonies—> Kin Selection (aka Inclusive Fitness)

  • Haplodiploid sex determination: eggs that are fertilized (diploid) become female, unfertilized eggs (haploid) become male

  • Daughters share, on average, 75% of genes with sisters

  • Your fitness is determined by propagating your genes, which can be done via your relatives

Order Odonata

What order is this:

• Class Insecta, Phylum Hexapoda

• Dragonflies and damselflies Labium

• Predacious hunters as both larvae and adults

• Larvae (nymphs) are aquatic

• Nymphs have a prehensile labium for grabbing prey

• Predacious hunters as both larvae and adults

• Larvae (nymphs) are aquatic

• Nymphs have a prehensile labium for grabbing prey

• Excellent fossil record of dragonflies from ~300 MYA

• Early dragonflies had wing span over 2 feet!

Order Ephemeroptera

What order is this:

• Mayflies

• Class Insecta, Phylum Hexapoda

• Spend almost entire life as aquatic nymphs

• Emerge into flying subadult, emerge again into sexually mature final adult (unique amongst insects)

• All mayflies in a given population emerge at the same time, potentially only every few years

Order Hemiptera

What order is this:

• True bugs

• Class Insecta, Phylum Hexapoda

• Includes many familiar species, such as cicadas, aphids, and giant water bugs

• Hemimetabolous development: nymphs look like little adults

• All have a long proboscis to suck fluid from plants or animal prey

• Includes many familiar species, such as cicadas, aphids, and giant water bugs

• All have a long proboscis to suck fluid from plants or animal prey

Order Coleoptera

What order is this:

• Class Insecta, Phylum Hexapoda

• beetles

• Forewings are hard coverings (elytra) over hindwings, which are used for flying

• Forewings are hard coverings (elytra) over hindwings, which are used for flying

• Larvae are often much larger than the adult form, have a unique hardened head while rest of body is soft

Order Diptera

What order is this:

• Class Insecta, Phylum Hexapoda

• Flies, mosquitos, gnats

• Hindwings are very reduced (halteres) and are used for stability, allows hovering

• Probably the insect with the most interactions with humans (mostly as pests)

Order Lepidoptera

What order is this:

• Class Insecta, Phylum Hexapoda

• Butterflies, moths

• Have the largest wings of any insect

• Larvae are often brightly colored and distasteful

• Coloration is made by scales covering wings

• Can migrate 1000s of miles each year

fate of the blastopore and all have a true coelom

What is the main difference between protostomes and deuterostomes?

Phylum Hemichordata

What phylum is this:

• hemichordates

• ~120 species in total

• Class Enteropneusta: Acorn worms

• Class Pterobranchia: Pterobranchs

• Name translates as “half-chordates” — Why?

• Have two main similarities with Chordates

• 1. Have gill slits in the pharynx, called pharyngeal gill slits

• 2. Some species have a hollow neural tube, similar to the dorsal hollow nerve cord of chordates

• But they are clearly related to Echinoderms!

• Develop a tornaria larvae, very similar to a type of echinoderm larva (called a bipinnaria)

• Swim with ring of cilia on base of larva (kind of like a trochophore)

Class Enteropneusta

What class is this:

• phylum Hemichordata

• acorn worms

• 90 described species

• 3 part body: proboscis, collar, and trunk

• Proboscis acts to open/close mouth

• Cilia on proboscis move food particles in to mouth when open

• Water goes out through gill slits after food particles removed

• Most species live in U-shaped burrows, solitary

• Leave big casts of feces at one end of the burrow

Class Pterobranchia

What class is this:

• phylum Hemichordata

• Pterobranchs

• Only 30 described species, very small (mm)

• Similar 3-part body plan to acorn worms

• Most live colonially, in tubes they secrete

• Has a crown of ciliated tentacles • Use tentacles to collect food from the water column

Phylum Echinodermata

What phylum is this:

• echinoderms

• 7000 extant species

• Entirely marine animals

• Very old lineage: fossil evidence from the Cambrian period (542–488 mya)

• Extant adults are commonly pentaradial (5-way radial symmetry), but many are not

• Radial symmetry evolved secondarily

• Thought to have evolved from bilateral ancestors: hence why part of Bilateria

• Based on larval forms

• Radial symmetry evolved secondarily

• Thought to have evolved from bilateral ancestors: hence why part of Bilateria

• Various shapes in different classes, but larvae are all bilaterally symmetrical

Phylum Echinodermata

What phylum has this external morphology:

• Divided into oral and aboral sides

• Body is made up of several key components:

  • Ossicles: calcareous plates under epidermis

  • Collagen: holds everything together

  • Spines: project from epidermis

  • Pedicellariae: little pincers on surface

• By varying the various amounts of these you get the different main types of echinoderms!

• Have five ambulacral areas, each with a concentration of tube feet (podia)

• Ambulacral areas generally on oral side

• Madreporite is a valve, regulating water in and out of the water-vascular system

• Water-vascular system: a hydraulic system of tubes and tube feet, used for feeding, locomotion, respiration and excretion

• The WVS is a coelom, but differs from the somatocoel

• Somatocoel: True coelom containing organs (intestines, digestive organs, gonads)

• Thus, two distinct body cavities!

• Generally rough and spiny, but can be smooth in species where spines are reduced

• Pedicellariae are tiny pincers around spines called (used to remove parasites)

• Ossicles are hard plates that are embedded in a matrix of collagen

• Make the body hard yet flexible

• Respiration varies in different classes

• No central brain; nerve ring coordinates movement

• Sensory organs: tentacles in sea stars and urchins, light sensitive eyespots in some

• No circulatory system

• Excretion and respiration are generally handled by the water-vascular system

• Feeding differs in different classes

• Distinct sexes, but generally not sexually dimorphic

• External fertilization: eggs and sperm released freely into open water

• Release of gametes often synchronized with lunar cycle or other cues (like corals)

Phylum Echinodermata

What phylum has this water-vascular system:

• Water enters via madreporite to stone canal to ring canal, then out to radial canals

• radial canals provide water to ampullae, which are the tops of the tube feet

• Changing water pressure inside the WVS moves tube feet, allows locomotion

Class Asteroidea

What class is this:

• phylum echinodermata

• Sea stars

• ~1500 species of sea stars (aka starfish)

• Commonly found from intertidal zone to the abyss (more than 6000 m deep!)

• Typically have all characters of echinoderms: 5 arms, madreporite, tube feet, etc.

• Can regenerate limbs if broken off (some species have autotomy, can intentionally discard a limb if needed)

• Sea stars respirate by pushing part of the lining of the coelom through the body wall into the surrounding water (papulae)

• Two stomachs: Cardiac stomach and Pyloric stomach

• Cardiac stomach: everted during feeding, begins digestion outside body

• Pyloric stomach: connects consumed food to the pyloric cecae in arms

• Pyloric cecae in arms achieves the same purpose as an intestine

• Provides lots of surface area for digestion and nutrient absorption

• Generally consume molluscs, crustaceans, smaller sea stars, etc.

• Have an anus, but large undigestible parts are spit back out the mouth

• Despite being slow moving, can be extremely invasive

• e.g., Crown of Thorns sea star is devastating to coral reefs when overpopulated

Class Ophiuroidea

What class is this:

• phylum echinodermata

• Brittle stars and Basket stars

• Brittle stars: Most diverse and abundant group of echinoderms (> 2000 species)

• Basket stars: < 200 species

• Found from intertidal zone to the abyss

• Very different from Asteroidea

• Differences from Asteroidea

  • Generally feed on small food particles

  • No pedicellariae

    • Arms covered in ossicles and moveable spines

    • Five hard plates for a mouth

    • No organs in their arms

    • Madreporite on oral side

• May not look like echinoderms at first… • But the “fans” are just branches off the five legs

Class Echinoidea

What class is this:

• phylum echinodermata

• ~950 extant species

• Sea urchins are called “regular”, have standard pentaradial symmetry

• Sand dollars, sea biscuits, and heart urchins are “irregular” because they have secondarily evolved bilateral symmetry

• Ossicles are fused to form a hard exoskeleton called a test

• Ambulacral grooves extended all the way to surround the anus

• “Oral side” thus covers the entire body Aboral side is just the area around the anus

• No arms, entire body covered in tube feet and moveable spines

• Can have several types of pedicellariae, some with venom

• Sea urchins use tube feet and spines to move

• Mouthparts called Aristotle’s Lantern

• Sea urchins graze primarily algae and other organic material

• Sand dollars filter particles

• Have huge reproductive organs, a delicacy to many (Uni in sushi terms)

• In some places, urchins have become overpopulated and are problematic

• In California, purple sea urchins are destroying kelp forests key to other animals

Class Holothuroidea

What class is this:

• phylum echinodermata

• Sea cucumbers, sea pig

• ~1700 extant species

• Body elongated, ossicles greatly reduced so that body is soft and leathery • No spines or pedicellariae

• Have 5 rows of tube feet, but usually only 3 are well developed (on the “ventral” side)

• Can move via muscular body contractions

• Madreporite is inside the pharynx

• Respire and excrete through the respiratory tree, connected to the cloaca

• Cloaca pumps water in and out, allow gas exchange from body cavity to sea water

• Tentacles around mouth are modified tube feet, used for feeding

• Most are scavengers, feed on decaying matter on sea floor

• Some species have more elaborate tentacles for filter feeding via mucus on tentacles

• For defense from predators, some tropical species can discharge very sticky Cuvierian tubules from anus

• Tubules are part of the respiratory tree and can be regenerated

• Many other species can eviscerate themselves for defense

• They can detach and shoot out their tentacles and some of their internal organs, which they can also regenerate

• Scotoplanus globosa, a walking sea cucumber that lives in the abyss (deeper than 1000 m)

1. Notochord 2. Dorsal hollow nerve cord 3. Pharyngeal gill slits 4. Postanal tail 5. Endostyle

Whate are the five characters of all chordates?

Notochord

What does this describe:

• Flexible, rodlike structure running along body

• First part of endoskeleton to form

• Allows muscle attachment, needed for locomotion

• Replaced with vertebrae in jawed vertebrates

Dorsal hollow nerve cord

What does this describe:

• Hollow cord produced by infolding of ectoderm on dorsal side

• May not stay hollow throughout life

• Brain = enlarged anterior end

• In vertebrates, the nerve cord & brain are protected by vertebrae and cranium

Pharyngeal gill slits

What does this describe:

• Openings that lead from the throat (pharynx) to outside the body

• Formed by ectoderm and endoderm coming together in the pharynx, forming a hole

• In amniotes, pouches form (not slits) so the pharynx isn’t open to the outside world

• Openings that lead from the throat (pharynx) to outside the body

• In tetrapods, which don’t have gills as adults, the pharyngeal pouches give rise to a variety of structures

• e.g., Eustachian tube, middle ear cavity, tonsils and parathyroid glands

• Thus, evolution has repurposed gill arches after the loss of gillsFormed by ectoderm and endoderm coming together in the pharynx, forming a hole

Post-anal tail

What does this describe:

• Aids in swimming, along with muscles and notochord

• Provided motility for larval tunicates and lancelets to swim

• Efficiency increased in fishes

• Tail present in humans as coccyx bone

Endostyle

What does this describe:

• Recently recognized as common to all chordates

• Originally secreted mucus for filter feeding, as well as iodinated proteins

• The thyroid gland is derived from the endostyle (a homologous structure)

• Secretes thyroid hormone

Phylum Chordata

What phylum is this:

• Two subphyla:

  • Cephalochordata (Lancelets)

  • Tunicata (Tunicates) – Note that your book uses an outdated and taxonomically incorrect name (Urochorda)

Subphylum Cephalochordata

What subphylum is this:

• phylum Chordata

• Lancelets (formerly Amphioxus)

• 32 known species in 3 genera

• Small, up to 7cm long

• Look sort of like a small fish, but lack fins

• Globally distributed in shallow coastal waters

• Buries body in sand w/ head sticking out

• No complex sense organs (e.g. eyes)

• Sister group to rest of chordates

• Once thought of as the “ancestral vertebrate”, but now considered related to the ancestor

• Lancelets have the five distinctive characteristics of chordates in simple form

• Ciliated tentacles on mouth pull water into buccal cavity and pharynx

• Food is trapped in mucus secreted by the endostyle on the pharyngeal bars

• Closed circulatory system for moving nutrients, but no heart and no blood (fluid moved via cilia)

• Respiration occurs through skin, no specified organs, no hemoglobin

• Rudimentary brain

• Dieocious, reproduction occurs by releasing gametes freely into water column

Subphylum Tunicata

What subphylum is this:

• phylum Chordata

• >2300 extant species

• Formerly called Urochordata

• Globally distributed, primarily in shallow water

• 3 morphologically distinct classes

• Class Ascidiacea: Sea squirts

• Class Thaliacea: Salps and Pyrosomes

• Class Appendicularia: Larvaceans

• Adults are highly simplified filter feeders

• Covered with hard or semi-hard “tunic” made of cellulose

• Most are sessile, some can swim

• Can be colonial or solitary

• Pump water body through to feed (like sponges and bivalves!)

• Larvae do not feed, only search for place to settle

• Adults are highly simplified, but larvae have all characters of a chordate

Class Ascidiacea

What class is this:

• subphylum tunicata, phylum chordata

• sea squirts

• ~2000 species

• Sessile filter feeders (like sponges)

• Incurrent and excurrent siphon (like bivalves)

• Water sucked in via incurrent siphon and out via excurrent siphon

• Water is forced through pharyngeal slits and food particles are captured by mucus secreted by endostyle

• Simple nervous system: no “brain”, just a single nerve ganglion

• Most are hermaphrodites

• Sperm are released via excurrent siphon into the water column, taken in by the incurrent siphon of neighbors

• Have three different growth forms

• Colonial individuals are zooids, cannot survive without other members of the colony (similar to colonial cnidarians and others)

Class Thaliacea

What class is this:

• subphylum tunicata, phylum chordata

• Salps

• Free-floating pelagic tunicates

• Incurrent and excurrent siphons oriented anterior to posterior, allows water flow to be used for feeding and locomotion • Can be several meters long

• Important planktonic filter feeders

• Includes Pyrosomes, which form huge tubes

Class Appendicularia

What class is this:

• subphylum tunicata, phylum chordata

• Larvaceans

• Free-floating pelagic tunicates

• Small, generally < 1 cm long

• Paedomorphic: Retain larval characteristics into adulthood

• Construct a protein and cellulose “house” around body

• The house is mucous and serves as a filter, concentrating food particles from water

• Houses are discarded and rebuilt when they become clogged

• Discarded houses create “marine snow”, important for bringing nutrients to the deep ocean

Conodonts

What is this animal:

• Tiny fossilized teeth first discovered in 1856

• Remained a mystery; no bodies known until 1983

• Only 11 bodies have ever been found, very soft tissue

• Resemble lancelets, but probably closer to Vertebrata

Subphlyum Vertebrata

What phylum is this:

• major advances

• Endoskeleton of cartilage and bone

  • Basal vertebrates: notochord/vertebrae composed of cartilage (e.g., jawless fishes, sharks, rays)

  • Bony fishes & tetrapods: endoskeleton of true bone

  • Bone is stronger, greater muscle attachment

• Muscular pharynx

  • The pharynx initially evolved to catch food passively via filter feeding (e.g., tunicates)

  • In vertebrates, the pharynx becomes muscular

  • Usage for respiration evolved later on

  • The pharynx initially evolved to catch food passively via filter feeding (e.g., tunicates)

  • In tetrapods, gills slits are closed and are pouches

  • Pharyngeal pouches are source of jaw bones, ear bones, glands

Superclass Cyclostomata

What subclass is this:

• jawless fishes

• Only 108 extant species in two classes

• Class Myxini: hagfishes (70 sp.)

• Class Petromyzontida: lampreys (38 sp.)

• Although quite different, two groups united by the lack of a bony jaw

• The group Agnatha (“without” + “jaw”) also includes extinct jawless fishes

• Both hagfishes and lampreys:

  • Lack jaws

  • Lack scales

  • Have cartilaginous skeletons

  • Have round mouths with rasping teeth

Class Myxini

What class is this:

• subphylum cyclostomata

• Hagfishes

• Entirely marine, scavengers

• Live on the floor of the ocean, often very deep

• Relatively little known about reproduction

• Feed by using keratinized teeth to rasp a hole in the body of dead animals

• Produce absurd amounts of slime from small pores along side of body

Class Petromyzontida

What class is this:

• subphylum cyclostomata

• Lampreys

• 38 known species; about half are parasitic

• Of parasitic species, 1/2 live in freshwater and 1/2 are anadromous (they migrate from sea to rivers for breeding)

• Feed via oral disc with keratinized teeth

• Non-parasitic species do not feed and live in freshwater (live entire life as larvae and adults only breed and then die)

• All lampreys breed in freshwater streams

• Males build nests to attract females; use mouth to attach to a rock and thrash body to excavate nest

• Females are extremely fecund!

• Lay 200,000–300,000 eggs

• Females and males die after breeding

• After hatching, larvae float downstream and settle in calm pools of streams or lakes

• Larvae are called ammocoetes

• Spend at 4–8 years as larvae (most of life)

• Ammocoetes filter feed in the sand (much like lancelets)

• Larvae are called ammocoetes

• Spend at 4–8 years as larvae (most of life)

• Ammocoetes filter feed in the sand

• After metamorphosis, migrate to adult habitat (lakes or ocean)

Ostracoderms

What is this:

• Early vertebrates covered with bony dermal armor, later modified to be scales in fish

• Paraphyletic grouping, includes multiple different lineages present from ~500–350 MYA

• awless (like Cyclostomata)

• Assumed to be filter feeders

• Major innovation: First group to have pectoral fins (precursor to tetrapod arms!)

• Major innovation: first group to repurpose the pharynx for respiration!

Placoderms

What is this:

• Major innovation: Some of the first jawed fishes with heads covered with bony armor (rest of skeleton cartilaginous)

• Major innovation: First pelvic fins

• Apex predators, very large