Post on 23-Dec-2015
33-16-05
Barb
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Teeth of radula-the hardest material
(magnetite) of biological origin
• Most mollusks have separate sexes– However, many snails are outcrossing
hermaphrodites.
• The life cycle of many marine mollusks includes a ciliated larvae, the trophophore.– This larva is also found in marine annelids
(segmented worms) and
some other lophotrochozoans.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 32.9A trochophore larva.
• The basic molluscan body plan has evolved in various ways in the eight classes of the phylum.– The four most
prominent are the Polyplacophora (chitons), Gastropoda (snails and slugs), Bivalvia (clams, oysters, and other bivalves), and Cephalopoda (squids, octopuses, and nautiluses).
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Marine; oval shapes and shells divided into eight dorsal plates.
• Muscular foot grips the rocky substrate tightly and creep.
• Grazers; use radulas to scrape and ingest algae.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 33.17
Polyplacophora - chitons
• Gastropoda - > 40,000 species; mostly marine, but also many freshwater species.– Garden snails and slugs have adapted to land.
• Distinctive characteristic - During embryonic development, gastropods undergo torsion in which the visceral mass is rotated up to 180 degrees, such that the anus and mantle cavity are above the head in adults.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 33.18
Diagrammatic Illustration of Torsion in Gastropod Molluscs
• Most gastropods are protected by single, spiraled shells into which the animals can retreat if threatened.– Other species have lost their shells entirely and may
have chemical defenses against predators (nematocysts from anemones).
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 33.19
Shell-less nudibranchs(sea slugs)
• Many gastropods have distinct heads with eyes at the tips of tentacles.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Conch
• Gastropods are among the few invertebrate groups to have successfully populated the land.
• In place of the gills found in most aquatic gastropods, the lining of the mantle cavity of terrestrial snails functions as a lung – pulmonate snails
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Class Bivalvia -- clams, oysters, mussels, and scallops.
• Bivalves have shells divided into two halves.– The two parts are hinged at the mid-dorsal line, and
powerful adductor muscles close the shell tightly to protect the animal.
– When the shell is open, the bivalve may extend its hatchet-shaped foot for digging or anchoring.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 33.20
• The mantle cavity of a bivalve contains gills that are used for feeding and gas exchange.
• Most bivalves are suspension feeders, trapping fine particles in mucus that coats the gills.– Cilia convey the
particles to the mouth.– Water flows into mantle
cavity via the incurrent siphon, passes over the gills, and exits via the excurrent siphon.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 33.21
• Cephalopods - rapid movements to dart toward their prey which they capture with several long tentacles. – Squids and octopuses use beaklike jaws to bite their
prey and then inject poison to immobilize the victim.
• A mantle covers the visceral mass; shell is reduced and internal in squids, missing in many octopi. Onlynautilus has externalshell.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 33.22
• Fast movements by a squid occur when it contracts its mantle cavity and fires a stream of water through the excurrent siphon.– By pointing the siphon in different directions, the
squid can rapidly move in different directions.
• The foot of a cephalopod (“head foot”) has been modified into the muscular siphon and parts of the tentacles and head.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Unique among mollusks, cephalopods have a closed circulatory system to facilitate the movements of gases, fuels, and wastes through the body.
• They have a well-developed nervous system with a complex brain and well-developed sense organs.– This supports learning and complex behavior.– Squid giant axon located on inside of mantel.
Innervates mantel and causes large contraction leading to forcing a jet of water through syphon.
– Giant axon used as model axon to work out the biophysics of nerve conduction. Large size electrode could be inserted directly into nerve.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Highly developed eye in cephalopods
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• All annelids (“little rings”) have segmented bodies.
• ~ 15,000 species ranging in length from less than 1 mm to 3 m for the giant Australian earthworm.
• Annelids live in the sea, most freshwater habitats, and damp soil.
6. Phylum Annelida: Annelids are segmented worms
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The phylum Annelida - three classes: Oligochaeta, Polychaeta, and Hirudinea.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Oligochaete-
E.g. earthworm Coelom is partitioned by septa, but the digestive tract, longitudinal blood vessels, and nerve cords penetrate the septa and run the animal’s length.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 33.23
• Digestive system - a pharynx, an esophagus, crop, gizzard, and intestine.
• The closed circulatory system carries blood with oxygen-carrying hemoglobin through dorsal and ventral vessels connected by segmental vessels.
• In each segment is a pair of excretory tubes, metanephridia, that remove wastes from the blood and coelomic fluid.– Wastes are discharged through exterior pores.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• A brainlike pair of cerebral ganglia lie above and in front of the pharynx.
• Earthworms are cross-fertilizing hermaphrodites.– Two earthworms exchange sperm and then separate.
• Some earthworms can also reproduce asexually by fragmentation followed by regeneration.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Polychaete - Each segment of a polychaete (“many setae”) has a pair of paddlelike or ridgelike parapodia (“almost feet”) that function in locomotion.– Each parapodium has several chitinous setae.– In many polychaetes, the
rich blood vessels in the parapodia function as gills.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 33.24b
• Most polychaetes are marine.
• Polychaetes include carnivores, scavengers, and planktivores. Many live in tubes with only the tentacles protruding from the tube.– The brightly colored
fanworms trap plankton on feathery tentacles.
– Many build tubes and
Thus called tube worms.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 33.24c
Chaetopterus
Scale Worms
• Some benthic polychaetes crawl around on the ocean bottom and are covered with large protective scales.
• Many leeches feed on other invertebrates, but some blood-sucking parasites feed by attaching temporarily to other animals, including humans.– Some parasitic species use bladelike
jaws to slit the host’s skin, while others secrete enzymes that digest a hole through the skin.
– The leech secretes hirudin, an anticoagulant, into the wound, allowing the leech to suck as much blood as it can hold.
– Medicinal use of leech.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Hirudinea - leeches.
Fig. 33.24d
Prostostomia: Ecdysozoa
Major Phyla:
1. Nematoda – round worms
2. Arthropoda – crabs, insects
spiders
• Undergo ecdysis shedding of exoskeleton.• Ecdysozoa grouping based mainly on molecular data.
Ecdysozoa - Introduction
• ~ 90,000 described species, and ~10x undescribed.• 1 mm to 1m - Ubiquitous habitats. Even in the extreme
cold soil of the Dry Valleys of Antarctica.• Many parasites, including human pathogens – elephantiasis, trichinosis, onchocerciasis (river blindness)
1. Phylum Nematoda
Scottnema lindsayae
(Antarctic soil)
Ascarislumbricoides
(human parasite)
Potato cyst nematode
Wuchereria bancrofti Wuchereria bancrofti Wuchereria bancrofti
Elephantiasis(Wuchereria
bancrofti)
Nematoda Characteristics• Cylindrical bodies, chitinous cuticle.• Complete digestive tract.• No circulatory system; use pseudocoelom fluid to
transport nutrients.• Their thrashing motion by
contraction of longitudinal muscles.
• Sexual reproduction.
Fig. 33.24d
Name the most famous nematode ? 3 shared 2002Nobel prize in medicine,
using this worm as a model system for studies in genetic regulation of organ development
and programmed cell death
Caenorhabditis elegans
+ hermaphrodite
Adult:
1090 cells
Programmed death 131 cells
959 cells
1179 cells
Programmed death 148 cells
1031 cells
At hatching: + hermaphrodite 558 cells
560 cells
The worm Noble laureatesm (2002):Sydney Brenner, H. Robert Horvitz, John E. Sulston
Berkeley MIT Sanger,UK
• ~ 1 billion billion (1018) individuals.• ~ 1 million arthropod species described ~67% of spp.• Ubiquitous habitats.• The diversity and success due to: body segmentation, a
hard exoskeleton, and jointed appendages specialization for functions.
2. Arthropoda:
Fig. 33.26
• Cuticle (exoskeleton) - protein and chitin:– thick and inflexible in some regions; protection.– thin and flexible in others; joints.– attachment points for muscles.– relatively impermeable to waterland habitats.– must molt (ecdysis) to grow danger of predation.
Arthropoda Characteristics
• Well-developed sense organs:– eyes, olfactory receptors, antennae.– cephalization; sense organs anterior.
• Open circulatory system.• Coelom much reduced.
• Respiratory system specialized for different habitat. • Aquatic species:
– External gills • Terrestrial species:
– Internal organs (book lungs in arachnids)– Tracheal system in insects.
Arthropod Respiration
(Crabs, lobsters, crayfish, shrimps)
TaditionalTaxonomy:
Phylum
Class:
Arachnida(spiders, scorpions,mites)
Diplopoda(millipedes)
Chilopoda(centipedes)
Insecta(insects)
Crustacea
Arthropoda
Trilobita(trilobites –extinct)
Chelicerata(jaw-like
chelicerae, no antennae, simple
eyes)
Alternate taxonomy:4 major lineages
Phylum:
Uniramia(jaw-like
mandibles, 1pair antennae,complex eyes)
Crustacea
Super-Phylum
Arthropoda
(jaw-like mandibles, 2 pairs antennae,
complex eyes)
• Trilobita
- Earliest arthropods.
- Cambrian (540 mya) to Permian. Extinct ~250 mya.
- Pronounced segmentation; uniform segments and
appendages
- Subsequent arthropod
evolution towards fewer, more specialized segments and appendages.
Fig. 33.27
• Chelicerata • Anterior cephalothorax, posterior abdomen.
– appendages more specialized than trilobites– most anterior appendages modified as chelicerae
(pincers or fangs).• Marine chelicerates – 4 species.
Sea spider
Horse shoe crab-living fossil
• Terrestrial chelicerates – majority in Arachnida.– Scorpions, spiders venomous predators– Ticks blood sucking parasites– Mites detritus eater; parasites of animals & plants
Fig. 33.29
scorpion mite
tick
• Arachnid characteristics
• Cephalothorax has 6 pairs of appendages. – 4 pairs of walking legs.– 1 pair pedipalps sensing or feeding.– Chelicerae usually for feeding. Glands contain
poison.– Spiders inject poison: immobilize preyspills digestive juices
on prey; sucks up liquid
meal.
Fig. 33.30x
• Spider Anatomy• book lungs - stacked plates large surface area for gas
exchange• Spider silk/web – unique prey capturing feature.
Fig. 33.30b
spider spinning cribellate net
Sticky silk
Wool-like cribellate silk
microcrystalline arrays of glycine-rich regions
beta-sheets ofalanine-rich regions