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Marine Invertebrates SOES1007 > Arthropods > Flashcards

Arthropods Flashcards

0
Q

What are Phylum Tardigrada?

A

The water bears. Found in temporary moist or wet habitats. Terrestrial & freshwater, some marine.
All suctorial feeders, plants and small animals. Some are gut parasites of molluscs & echinoderms.
400spp, 0.05-1.2mm

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1
Q

What are the Ecdysozoa?

A

All animals that shed their exoskeleton.
3 (Tardigrade 4) layer organic cuticle.
Lack locomotory cilia
Embryo has no spiral cleavage - superficial cleavage (yolky egg)

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2
Q

What is a Tun in reference to the tardigrades?

A

The resistant stage where they can survive wide temp changes (-272 to 15012 degrees C).
Can also encyst or produce encysted eggs that can survive 60+ years.

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3
Q

What are the general features of Tardigrades?

A

Unsegmented bodies. 4 pairs of unjointed claw bearing legs.
Straight through gut, buccal stylets to pierce prey. Muscular pumping pharynx.
Chitinous cuticle. moults to grow.
Some excrete by malphighian tubes into gut.
Nervous system: paired ventral nerve cords & ganglia & ‘brain’.
Single sex, sometimes parthenogenetic, single gonad, direct development.

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4
Q

What is the Phylum Onychophora (velvet worms)?

A

Thought to be an intermediate between annelids and arthropods - now more likely related to early arthropods.
70 spp, up to 15cm, all terrestrial in humid habitats.

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5
Q

How do the velvet worms (onychophora) hunt?

A

They are mainly nocturnal predators, capture active prey by spraying strings of mucus-like substance up to 0.5m from oral papillae, hardening immediately. Also used in defence. Some spp shown to live and hunt in small groups.

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6
Q

What are the general features of the velvet worms (onychophora)?

A

Worm-like, segmented w/ short unjointed fleshy legs, each of which are hollow with a clawed terminal pad.
Straight through gut w/ no digestive diverticula.
Open blood system, tubular dorsal heart, but no blood vessels. Haemocoel and hydrostatic skeleton.
V. thin chitinous cuticle, moulted to grow.
Body wall w/ circular and oblique muscles.
Excretion: pairs of sac-like glands in segments, anterior sacs salivary glands posterior sacs gonoducts.
Cuticule water-permeable.

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7
Q

What are the features of the velvet worms (onychophora)? (PT II)

A

Gaseous exchange via tracheal system, many spiracles per segment.
Nervous system: brain + pair of separated ventral nerve cords, linked in segments but no segmental ganglia.
One pair of sensory antennae on head and simple eye at base of antenna.
Gonochoristic, paired gonads, internal fertilisation, live young, direct development.
Feeding - one pair of ripping mouthparts derived from first pair of appendages.

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8
Q

What are the general Arthropod characteristics?

A

Bilaterally symmetrical & metamerically segmented.
Outer cuticle & body divided into tagmata. Exoskeleton hard and inflexible. Growth by moulting (Ecdysis)/metamorphosis.
Flexible, jointed appendages w/ fast acting muscles attached to inside of cuticle.
Well developed neuro-hormonal system, dorsal brain/ganglia around gut. Well developed sensory system.
Complete digestion system, body cavity mostly hemocoel.
Open circulatory system.
Usually separate sexes.

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9
Q

What are the sub-phyla of the Arthropoda?

A

Sub-Phylum Unirama (Hexapoda & Myriapoda)
Sub-Phylum Chelicerata
Sub-Phylum Crustacea.

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10
Q

What is contained within sub-phylum Myriapoda?

A

Chilopoda - centipedes.
Diplopoda - millipedes.
Pauropoda - (insect-like myriapods).

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11
Q

What are the characteristics of sub-phylum Myriapoda?

A

Exclusively terrestrial, though a few spp found commonly in the intertidal.
Generally insect-like -> elongate bodies, so many segments. No thorax/abdomen separation.
Most segments with a pair of uniramous walking legs.

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12
Q

What are the two classes of Myriapods?

A

Chilopoda (centipedes).

Diplopoda (millipedes).

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13
Q

What are the general characteristics of the Chilopoda?

A

Centipedes are all carnivores. The first pair of legs form large prey-catching ‘fangs’ w/ poison glands. Each somite has a pair of jointed legs.

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14
Q

What are the general characteristics of diplopoda?

A

Millipedes are all detritivores and appear to have 2 pairs of limbs per segment.

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15
Q

What is sub-phylum insecta?

A

The insects. The most successful arthropod group.

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16
Q

What are the main adaptions of sub-phylum hexapoda?

A

Main adaptions include wings, though they may be primitively wingless or secondarily lost. They also have a waterproof cuticle.

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17
Q

What are the two types of flight muscles in hexapods?

A

Direct - attached to the wing.

Indirect - bring about changes in body shape to move the wings.

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18
Q

What are the characteristics of the hexapod’s body?

A

There are 3 regions:
The head: Acron + 3 or 4 segments (w/ appendages, single pair of antennae)
Thorax: 3 segments (w/ appendages) +1-2 pairs of wings.
Abdomen: 11 segments, usually w/o appendages.
Appendages all UNIRAMOUS.

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19
Q

What is contained within the head appendages of the hexapods?

A

Acron - first part of head, not counted as somite. No appendages.
1 pair of antennae.
1 pair of mandibles.
1(2) pairs of maxillae.
Eyes - Lateral Ocelli (simple eyes), compound eyes and median ocelli.

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20
Q

What are the other characteristics of hexapods?

A

Usually gonochoristic w/ internal fertilisation, gonopores on last abdominal segment.
Often distinct larval stage.
Gas exchange: branched tracheal tubes opening via spiracles.

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21
Q

What are is the digestive system of hexapods like?

A

The foregut contains mouth & salivary glands, oesophagus & crop/gizzard.
Midgut contains stomach and gastric caeca - digestion/absorption.
Hindgut - intestine/rectum/anus - water resorption.

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22
Q

What are the two different types of growth in hexapods?

A

88% of insects have Holometabulous metamorphosis w/ separation of growth - larva differentiation -> pupa reproduction -> adult.
12% have Hemimetabolous (gradual) metamorphosis. Young are called nymphs.

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23
Q

What are the marine hexapods?

A

Halobates spp - marine or sea skaters.
Lipura - flightless insect common in rockpools.
Midge and mosquito larvae in saline lagoons and among seaweed.
Coelopa frigida - seaweed fly.

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24
Q

What is sub-phylum chlicerata?

A

Arachnida - spiders, scorpions, pseudoscorpions, ticks and mites.
Merostomata - horseshoe crabs.
Pycnogona - sea spiders.

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25
Q

What are the characteristics of the Chelicerata?

A

The body is divided into 2 regions - PROSOMA formed by acron & 6 appendage-bearing segments.
OPISTHOSOMA without limbs (some groups w/ high modified appendages).
Appendages uniramous, no antennae or mouthparts.
Prosoma contains 1 pair of chelicerae, 1 pair of pedipalps & 4 walking legs.
Eyes medial and lateral ocelli (only compound in one group)
Excretion by coxal glands or malpighian tubules - mainly guanine.

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26
Q

How do the Chelicerata reproduce?

A

Gonochoristic internal fertilisation, eggs hatch as mini adults.

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27
Q

What is the gas exchange of chelicerates like?

A

Gas exchange by opisthosomal appendages - external ‘book gills’ in marine forms, or by internal ‘gill books’ in terrestrial forms.
Blood system uses haemocyanin.

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28
Q

What are the characteristics of the Arachnida and what is contained in that group?

A 
The spiders, scorpions, pseudoscorpions, ticks and mites. Mainly terrestrial (many marine mites e.g. Acarini) & successful - 62000 spp.
Simple eyes only, non-chelate legs. Mainly predatory, injected poison, silk/webs (spiders & some mites)
Some mites (Acarini) parasitic or feed on plants & detritus.
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29
Q

What are the Merostomata?

A

Horseshoe crabs.

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30
Q

What are the characteristics of the Merostomata?

A

Thick, unsegmented horseshoe carapace covering prosoma. Small hinged opisthosoma + caudal spine. Opisthosoma with flat plate-like swimming limbs.
Fertilisation external w/ precopula. Eggs laid in substrate, hatch as segmented larvae.
Carnivore using ‘Gnathobases’ - worms/small molluscs.

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31
Q

What is the morphology of the Horseshoe crab?

A

2 compound and 2 simple eyes. The head has 6 segments with 1 pair of chelicerae and 5 pairs of walking legs. The abdomen has 6 segments with the appendages fused in a median line.

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32
Q

What are the Pycnogona/Pycnogonida?

A

The sea spiders. There are around 1000spp.

33
Q

What is the phylogeny of the Pycnogona?

A

Recent DNA studies show that pycnogonids are not closely related to other chelicerates. They are best considered as an early branch from the arthropod lineage.

34
Q

What are the characteristics of the Pycnogonida?

A

ALL marine, mainly benthic. Usually small but largest leg span 75cm.
Most species 4 pairs walking legs, some spp 5/6.
Males carry eggs on ovigers, additional legs btween pedipalp & legs.

35
Q

What is the name of the distinctive larva of the Pycnogonida?

A

Protonymphon.

36
Q

What are the feeding & excretion systems of Pycnogonida like?

A

They feed on sponges & cnidarians using suctorial proboscis.

Excretory & respiratory systems absent - use diffusion.

37
Q

What is the sub-phylum Crustacea?

A

About 38k known spp, of which 84% marine, 13% terrestrial & 3% terrestrial.
Includes crabs, lobsters, crayfish, barnacles, krill, woodlice.
Size range: <1mm-4m.

38
Q

What are Crustaceans so successful?

A

They have a great plasticity in body size & form. Structural plasticity allows them to swim, crawl, bore, fix to rock, graze, filter feed, deposit feed, carnivorous, herbivorous, detritivorous & parasitize.
Wide range of benthic/pelagic niches utilised.

39
Q

What are the characteristics of the segments of Crustaceans?

A

Head composed of: Acron + 2 pairs of antennae, 1 pair of mandibles, 2 pairs of Maxillae.
No. body segments and body division varies, but usually consistent within classes.

40
Q

What is the name of the last body segment of the crustaceans?

A

The telson.

41
Q

What are the appendages in the crustaceans?

A

They are basically biramous (dividing to form two branches.)

42
Q

What are the two parts of a biramous leg?

A

The endopod and the exopod.

43
Q

What is the crustacean gut & feeding like?

A

Straight through gut with a pair of digestive diverticula, where food absorption & digestion occur. For those not feeding on fine particles there is a grinding ‘mill’ in the foregut.
Excretion by antennal or maxillary glands - ammonia.

44
Q

What is the grinding ‘mill’ in the foregut of a crustacean?

A

Mill has chitinous ridges/teeth for mastication and setae for straining food before it passes into the pyloric stomach.

45
Q

What are the reproductive systems of crustaceans like?

A

Gonochoristic, occasionally hermaphroditic, usually internal fertilisation.

46
Q

What is the basic crustacean larval form?

A

The Nauplius larva.

47
Q

What are the other crustacean larval forms?

A

There are a wide variety of larval forms, often several per species. Larva hatching from eggs attain the adult form by a sequence of moults/metamorphoses, sometimes dramatic.

48
Q

What is the sequence of larval developments that crustaceans typically go through?

A

Zoea -> Decapod.

49
Q

What is a Zoea larval stage?

A

The first hatch stage of crustaceans. All divisions of the body are obvious, the abdomen is relatively more advanced than the thorax.
Locomotion by thoracic biramous limbs.
Each moult produces increased segment number, change in limb structure etc.

50
Q

What is the Decapod larval stage?

A

After the Zoea - collectively the past larval stage although larval stages have a number of names associated w/ particular families.

51
Q

How do crustaceans grow?

A

Growth through repetitive moulting - ecdysis. Some decapods have a terminal intermoult - anecdysis.

52
Q

What are the Crustacean classes?

A 
Cephalocarida
Branchiura
Remipedia
Mystacocarida 
Branchiopoda
Copepoda
Cirripedia
Ostracoda
Malacostraca
53
Q

What is Class Remipedia?

A

Cave shrimps. 10-20 spp, primitive, found in marine caves.

54
Q

What are the characteristics of class Remipedia?

A

Biramous head appendages - antennae and antennules.
Biramous trunk appendages directed laterally (15-42 segments.)
No carapace, trunk un-regionalised. Raptorial - hermaphrodites.

55
Q

What is Class Branchiopoda?

A

Brine shrimps, water fleas, etc.

56
Q

What are the characteristics of class Branchiopoda?

A

Carapace, when present, often variable in form. Body has variable no. of distinct segments. Telson w/ rami.
Paired compound eyes usually present, antennules reduced or absent.
Thoracic limbs usually uniform.

57
Q

What is class Copepoda?

A

The dominant marine plankton (also freshwater) and dominant crustacea in marine sediments, 8.4k spp.

58
Q

What are the characteristics of class Copepoda?

A

Generally small (<2mm - 2cm).
Body divided into: Head + Thorax (6 segments) - Cephalothorax & Abdomen (5 segments, no appendages), no carapace.
Attennules/antennae generally well developed.
Compound eyes absent.
Naupilius & Copepodite larvae.

59
Q

What are the characteristics of parasitic copepods?

A

They lead to immune suppression and are a cosmetic issue for fish famers. They’re ecto-parasitic - attach to the gills & soft tissue.

60
Q

What is Class Ostracoda?

A

The mussel shrimps. A group of small (1-2mm) shrimps in which the body is enclosed in a pair of calcareous valves. 13k extant species, 70k described in fossil record.

61
Q

What are the characteristics of class Ostracoda?

A

No gill structures - gas exchange takes place through branchial plates located on mandible, maxilla or the 5/6 limb. They tend to be zooplankton or benthic.

62
Q

What is class Cirripedia?

A

The barnacles.

63
Q

What are the characteristics of class Cirripedia?

A

Modified sessile adult body form, effectively headless & w/o abdomen. Either attached directly to substratum or by tough stalk. Body enclosed by calcareous plates that allow feathery legs (cirri) to extend to filter feed. One group modified as parasites.
Compound eye absent in adults.

64
Q

How do class Cirripedia reproduce?

A

Usually hermaphroditic, w/ nauplius larvae, cyprid stage, before final metamorphosis.

65
Q

What is Rhizocephala?

A

A parasitic barnacle. It tends to settle on male crabs.

66
Q

How does Rhizocephala affect the crabs it settles on?

A

In crabs, it effectively castrates them and extends a network of tubes throughout the body, focusing on the digestive system. It then uses the crab as a conduit for its own reproduction and food gathering.

67
Q

What is Class Malacostraca?

A

One of the largest groups of crustacea w/ 23k spp. Lobster, crabs, etc.
6 major groups, of which PERACARIDA & EUCARIDA account for most of the spp.

68
Q

What are the general characteristics of class Malacostraca?

A

Body form fairly constant with 6 segments forming the head, 8 thoracic segments and 6 abdominal segments.

69
Q

What is superorder Pericarida?

A 
Amphipoda - sand hoppers
Isopoda - woodlice, slaters etc
Mysidacea - opossum shrimps.
Tanaidacea
(Spelaeogriphacea - cave shrimp)
70
Q

What are the characteristics of superorder Peracarida?

A

No carapace, or when present leaves at least 4 thoracic segments free.
First thoracic segment fused w/ head. Eyes sessile or pedunculate.
Oostegites on base of limb. In females form an external Marsupium beneath thorax, where eggs develop.
Direct development within egg, hatch in brood pouch.

71
Q

How can Amphipoda (sand hoppers) be identified?

A

Their bodies are laterally flattened.

72
Q

How can Isopods (woodlice etc) be identified?

A

Their bodies are dorsoventrally flattened.

73
Q

What is order Eucarida?

A

Two main superorders:
Euphausiacea (Krill) (More like KRILL ME haha)
Decapoda (Crabs, Lobsters, Prawns, Shrimps, etc)

74
Q

What are the main morphological features of Superorder Euphausiacea - Krill?

A

Carapace is fused with the cephalopthorax.
Stalked eyes.
Since series of gills attached to base of thoracic limbs, not completely covered by carapace.
No statocyst.
7 thoracic limbs, covered in hairs which trap particles as it swims through water.

75
Q

What are the main ecological features of superorder Euphausiacea - Krill?

A

Global distribution
Basically herbivorous filter-feeders, but also omnivorous feeders.
Swarming - significant component of ecosystem, particularly at high latitudes.

76
Q

What is super order decapoda?

A

Crabs, shrimps, etc.

77
Q

What are the two groups of decapods?

A

Natant decapods - swimming.

Reptant decapods - crawling.

78
Q

What are the main morphological features of decapods?

A

3 thoracic segments fused with head, with these appendages forming additional mouthparts - maxillipeds.
Carapace present. Usually more than 1 series of gills - base of limbs and thoracic segments.
Eggs usually brooded attached to pleopods, rarely hatch as nauplii.

79
Q

What are infraorders caridea and penaeidea?

A

The shrimps and prawns.

80
Q

What are the characteristics of infraorders caridea and penaeidea?

A

Prominant saw-tooth rostrum.
First 3 pairs of thoracic limbs are maxillipedes (pincers)
Usually more than one series of gills on thoracic limbs.
They are natant w/ well developed swimming pleopods on abdomen.
Well developed, stalked compound eye.
Caridean - pleura or 2nd abdominal segment overlaps others.

Marine Invertebrates SOES1007 (8 decks)

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