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Animal Diversity > 6. Mollucs, Annelids and Nematodes > Flashcards

6. Mollucs, Annelids and Nematodes Flashcards

1
Q

Give some examples of molluscs. 4

A
  1. Snails 2. Bivalves 3. Nudibranchs 4. Cuttlefish
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2
Q

Define paraphyletic. 1

A
  1. Descended from common ancestor but not including all descended groups eg. fish
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3
Q

Give and overview of the supposed ancestral mollusc. 8

A
  1. Has a shell, although some molluscs don’t have shells 2. Ventral nerve cord goes around oesophagus, not stomach 3. muscular foot 4. visceral mass in center - flow through gut 5. has coelum 6. mouth with radula 7. mantle - dorsal wall which covers organs 8. Gills
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4
Q

What is a mollusc? 7

A
  1. Bilaterian 2. Body divided into head, foot and visceral mass 3. Covered by fleshy mantle 4. mantle typically secretes hard shell 5. Contains true body cavity/coelom 6. Typically have radula for feeding, but reduced in some groups 7. Aquatic or terrestrial
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5
Q

What feeding strategies do different mollusc types use? 10

A
  1. Gastropods eg. slugs and snails 2. include grazers 3. browsers 4. predators 5. Bivalves are filter feeders 6. Cephalopods 7. scavengers and predators 8. fast and intelligent 9. can be hghly visual 10. able to manipulate objects
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6
Q

Describe gastropods. 6

A
  1. Enlarged foot for locomotion 2. Visceral mass covered by shell for most forms 3. Some slugs have very thin shells inside them 4. Shell develops as a spiral in slugs, snails and marine snails due to torsion of body, which secretes shell 5. Sea slugs, order Oposthobranchia, do not undergo torsion during development 6. There are marine, freshwater and terrestrial species
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7
Q

Describe gastropod feeding apparatus. 6

A
  1. Radula is attached to cartilage, and rasps and sucks out insides of other animals.
  2. Supported by odontophore and can move along it
  3. Worn down teeth at front end are continuously replaced from the back
  4. Odontophore movement controlled by buccal muscles
  5. Buccal mass consists of protractor and retractor muscles
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8
Q

What radula adaptations do some molluscs have? 3

A
  1. Conus has a harpoon like radula, up to 2m long
  2. Squid and octopi have chitinous beaks and tounge like radula
  3. Bivalves have lost their radula and are now filter feeders
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9
Q

What shells to cephalopods have? 3

A
  1. Nautilus floats and has a calcium septum so shell can fill with air
  2. squid have shell on the inside
  3. Octopi have no shells
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10
Q

What are the differences between nautilus and ammonite? 4

A
  1. Modern nautilus look very like ammonites - 200-65 m years old
  2. Ammonites have more ridges, nautilus is smoother
  3. Nautilus is the only thing similar to ammonites still extant
  4. Ammonite extinction may be due to change in ocean pH
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11
Q

Describe cephalopods. 5

A
  1. Well developed eyes
  2. Shell chambered eg. nautilus, involved in bouancy eg. cuttlefish, reduced or absent
  3. Single foot has developed into tentacles
  4. Active predators
  5. Marine only, no freshwater
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12
Q

Describe octopus reproduction. 4

A
  1. Male inserts hectocotylus - mating arm - into female siphon
  2. spermatophore released
  3. contains sperm and sometimes food/protein as an incentive to mate
  4. Internal fertilisation
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13
Q

Describe the reproduction of the Pholidoteuthis adami squid. 4

A
  1. 1400m down, Gulf of Mexico
  2. Male sits upside down and backwards on top of female
  3. Terminal organ extends from funnel and released spermatophores
  4. Spermatangia burrow into dorsal mantle tissue of female
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14
Q

Describe nudibranchs, with special attention to Bullock’s nudibranch. 6

A
  1. Bullock’s nudibranch
  2. Australian
  3. 3-4cm long
  4. 30m deep
  5. Spiral egg case
  6. Some nudibranchs lay eggs on tunicate prey
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15
Q

What are sacoglossans? 5

A
  1. a clade of non-nudibranch sea slugs
  2. exhbit kleptoplasy - use chloroplasts for themselves
  3. This is done by a variety of mechanisms
  4. Have genes to take photosynthetic energy - rare
  5. Keep plasmids alive through horizontal gene transfer
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16
Q

Give some examples of annelids. 4

A
  1. All are lophotrochozoans
  2. Earthworms
  3. Leeches
  4. Polychaetes
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17
Q

Describe external annelid morphology. 8

A
  1. Segmented
  2. Segments divided externally by annuli (rings) and internally by septa (partitions)
  3. Secretes collagen cuticles like nematodes
  4. New segments are added from in front of the pygidium
  5. Growth may be determinate to fixed number of segments eg. leeches or not.
  6. Segmernts are repeated and contain mostly same organs eg. muscles, setae, limbs
  7. Segments allow development of specialised limbs and other organs
  8. Diversity is extensive
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18
Q

Define pygidium. 1

A
  1. final segment of annelid, incl anus
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19
Q

Define setae. 1

A
  1. Stiff bristles/hairs found on annelids
20
Q

Describe the internal morphology of annelids. 7

A
  1. Divided into segments called matemeres, each is an organ-and-fluid-filled box
  2. Internal repetition of organs in each segment
  3. Some organs are continuous along length, passing through septa
  4. Gut travels down through longitudinal muscle in centre
  5. Hydrostatic skeleton - water pressure changes inside causing movement
  6. Circular muscles lengthen segment
  7. Longitudinal muscles shorten segment
21
Q

Describe earthworms, AKA oligochaetes. 9

A
  1. Extremely common
  2. Terrestrial and frshwater, and a few marine
  3. Present on all contintents except Antarctica
  4. Canadian worms are all European importa- could not live there previously due to glaciers
  5. most are detritivores, a few are predators
  6. some are commensals
  7. mm-m in length, big range
  8. some are blue as no Hb, use other transporters
  9. Migrate very slowly
22
Q

Describe oligochaete morphology. 7

A
  1. A few small setae
  2. Rounded tube shape
  3. Head and tail pointed with no bvious sensory structure
  4. Septa
  5. Citellum contains specialised glands used in cocoon formation
  6. Citellum - non segmented bulge with thickened wall
  7. Have eye patches that can see light
23
Q

Describe oligochaete reproduction. 5

A
  1. Hermaphrodites but cross fertilise, don’t self fertilise
  2. Worms come together, meet at citellum and cocoon forms
  3. Fertilisation occurs in cocoon, which moves off worm containing eggs
  4. Can reproduce asexually by division
  5. Extensive regeneration
24
Q

Describe the nervous sytem, respiration, circulatory system and feeding habits of polychaetes. 9

A
  1. Doughnut brain jouns ventral nerve cord
  2. No dorsal nerve cord
  3. Respire through body wall, but big polychaetes can have gills
  4. Multiple hearts which contract for circulation
  5. Those without Hb may be green/clear
  6. Modified digestive tracts in front segments
  7. Mobile polychaetes can evert pharynx
  8. Sedentary polychaetes have a variety of structures
  9. Leeches use symbiotic bacteria to digest blood
25
Q

Describe leeches/hirudiniea. 6

A
  1. Quite common
  2. Marine, freshwater and terrestrial
  3. Predators or blood feeders in all habitats
  4. Some parasitic
  5. mm up to 45cm
  6. Medical uses
26
Q

Describe hirudinea morphology. 7

A
  1. No setae
  2. Dorso-ventrally flattened
  3. Movement in same dumension - undulate
  4. Posterior and anterior suckers
  5. Additional transverse muscles
  6. Loss of septa - segmented on outside only
  7. Coelom filled with cells to use only small spaces
27
Q

Descriibe hirudinea reproduction. 6

A

1, self-fertilising hermaphrodites

  1. Have a citellum and can produce a cocoon, but some species don’t
  2. Some species do it by hypodermic insemination
  3. They produce dart-shaped spermatophores
  4. Fire these into each other
28
Q

What are polychaetes? 6

A
  1. Have many bristles
  2. Are common - 10s of 1000s per m2 of intertidal mud/reef
  3. Marine, with about 50 freshwater species
  4. Live between intertidal zone and deep sea vents
  5. Incl predators, detritovores and filter feeders
  6. mm to ms big
29
Q

Describe polychaete reproduction. 7

A
  1. Usually dioecious
  2. asexual by budding or fission
  3. extensive regeneration, even from a single segment
  4. usually external fertilisation
  5. Some species release eggs and sperm into water column
  6. SOme produce attached individuals that contain only gonads
  7. some transform into a reproductive form - epitoke
30
Q

What is the difference between epitokes and atokes? 4

A
  1. Epitokes are usually filled with gonads and have no guts
  2. they have good eyes, swim well and orient themselves to the moon at the surface
  3. when they all arrive at the surface, they explode, releasing eggs and sperm
  4. The other part of the polychaete, the atoke, is safely at rest at the bottom, producing more epitoke clones
31
Q

Is segmentation homologous? 5

A
  1. Segmentation is found in various groups incl annelids, arthropods and chordates
  2. until about 10yrs ago, it was thought segmentation evolved sevral times into these groups
  3. Similar mechanisms seem to be involved, raising new questions
  4. Similar mechanisms do not mean polyphyly can be ruled out
  5. may be convergent evolution
32
Q

What are nematodes? 8

A
  1. Ecdysozoa
  2. Round/thread worms
  3. Marine - beached to seep dea trenches
  4. Freshwater - frozen lakes to hot springs
  5. Terrestrial - tropics to arctic
  6. on or in plants/animals - often parasitic. Human infection rates up to 85%
  7. almost always live in water or on a water film
  8. Extremely abundant - 1m species estimated
33
Q

Describe external nematode morphology. 9

A
  1. long and thin with pointy ends, usually
  2. unsegmented
  3. cuticle
  4. Made of collagen
  5. complex with 3 layers
  6. can be ornamented eg. setae involved in movement
  7. may have caudal gland for attachment
  8. epidermis may be syncytial
  9. locomotion not wiggle like, whip like
34
Q

Describe internal nematode morphology. 7

A
  1. Tube within a tube
  2. Body divided into quarters in cross-section
  3. muscles go around outside along with cuticle - just below it
  4. body cavity is liquid filled, allowing movement
  5. Simple set of organisms
  6. no circular muscles
  7. fewer setae than earthworms
35
Q

Describe the nematode nervous system.6

A
  1. doughnut brain
  2. muscles directly connected to nerve cords
  3. Labia have innervated papillae - fleshy projections
  4. specialised sensillae called amphids for mechanoreception and chemoreception
  5. May have pigment spots or ocelli
36
Q

Describe the nematode body. 3

A
  1. Gas exchange through body wall
  2. No circulatory system
  3. Get is one cell thick tube, food pumped by oesoophagus
37
Q

How do nematodes reproduce? 3

A
  1. most species diecious, or hermaphroditic, or hermaphroditic with males eg. c. elegans
  2. spermatozoa lack flagella, therefore crawl.
  3. mating by close contact - mate inserts spicules
38
Q

What are the Nematomorpha? 5

A
  1. Look like nematodes but not
  2. all parastic
  3. 300 species
  4. Unlike nematodes, have terminal cloaca
  5. No evidence that they manipulate host to go near water, may just induce erratic behaviour.
39
Q

Intelligent life without bones. M. Gross. Current Biology. 2015.

Describe cephalopod evolution. 3

A
  1. 2 spot octopus (O. bimaculoides), first cephalopod to have genome sequenced
  2. Cephalopods became distinct from other molluscs about 530m yr ago
  3. have good eyesight, are sharp moving and intelligent - unexpected in vertebrates
40
Q

Intelligent life without bones. M. Gross. Current Biology. 2015.

Describe the cephalopod eye and brain. 5

A
  1. Sophisticated camera eyes
  2. No blind spot as in mammals
  3. Doughnut brain and decentralised nervous system
  4. Greater information processing capacity than other molluscs
  5. No whole genome duplication, but many transposons
41
Q

Intelligent life without bones. M. Gross. Current Biology. 2015.

Describe cephalopod intelligence and behaviour. 3

A
  1. Camoflage by changing size of pigmented skin cells
  2. can pretend to be plants, 2 legged or burst away, leaving ink cloud, to hide from predators
  3. Trick prey by frightening them into tentacles
42
Q

Molluscs. Haszprunar and Wanninger. Current Biology. 2012.

How are molluscs important to humans? 4

A
  1. Many gastropods are intermediate hosts for pathogenic trematodes
  2. conotoxins of cone shells screened for non-addictive painkillers
  3. Land snails used as conservation indicators
43
Q

Animal diversity. Hickman et al. 2012.

Describe the form and function of mollluscs. 4

A
  1. Head-foot portion for feeding, cephalic sensory organs and locomotor organs
  2. visceral mass for digestive, circulatory, respiratory and reproducitve organs
  3. Mantle surface - gas exchange and mantle cavity often contains gills or a lung
  4. shells have 3 layers - outer periostratum (boring protection), middle of calcium carbonate prisms and inner nacre - caco3 sheets
44
Q

Animal diversity. Hickman et al. 2012.

Describe the class Gastropoda. 6

A
  1. Usually slow with heavy shells
  2. Largest mollusc group/class
  3. Some have an operculum - proteinaceous place used to close up shell when animal is inside.
  4. Mostly univavle
  5. Torsion means fouling (waste going over gills) should be possible, but removal of right gill usually prevents this
  6. Some have a gill, some use skin, some terrestrials have lung formed from mantle wall
45
Q

Animal diversity. Hickman et al. 2012.

Describe the class Bivavla. 4

A
  1. sedentary suspension feeders
  2. No head/radula, little cephalisation
  3. gills
  4. muscular foot moves between valves, fills with blood and anchhors, muscles contract, foot shortens and pulled forward
46
Q

Animal diversity. Hickman et al. 2012.

Describe the Polychaeta. 4

A
  1. Mostly marine
  2. Live in small gaps or burrows, a few are pelagic
  3. Very specialised sensory organa
  4. No permanent sex ogans and external fertilisation
47
Q

Animal diversity. Hickman et al. 2012.

Describe the Oligochaeta. 3

A
  1. Each segment has 4 pairs setae
  2. Anchor to prevent tripping
  3. Some are aquatic - freshwater or marine

Animal Diversity (13 decks)

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