Sub-phylum Crustaceans

How many crustacean species?

50000

Crustacean classes

Branchiopoda

Cephalocarida

Remipedia

Cirripedia

Copepoda

Malacostraca

Crustaceans in general

Eucoelomic (true coelom)

Segmentation

cephalothorax

muscular abdomen

ancestral biramous appendages

What is crustacean body wall made of?

Chitinous reinforced with calcium carbonate

Carapace

shell covering the cephalothorax

What distinguishes crustaceans from all other arthropods?

Two pairs of antennae

How many pairs of mouth part appendages do they have?

Three pairs

Reproduction of crustaceans

Gonochoristic except sessile cirripedia

Nauplius larvae

Internal transport and gas exchange

open circulatory system - haemolymph

O2 in simple solution or bound to haemoglobin or haemocyanin

gills for gas exchange

respiratory water Current generated by appendages

Crustacean vision

Median eye - larval stage orientation eye

Compound eye - two - image cruder than human eye, colour discrimination

Crustacean growth

arthropods moult - ecdysis

tissue growth continues but external dimensions is incremental

hormone controlled resorption of calcium salts and their redeposition in the new outer chitinous skeleton

Indeterminate growth vs determinate growth

Indeterminate growth - growth and ecdysis continues throughout life

determinate - once crustaceans are sexually mature they stop growing

Class Branchiopoda

Fairy shrimps - mostly freshwater

order - cladoceran = water fleas

Class Cirripedia

1200 species - 3 superorders

Acrothoracica - burrowers

Rhizocephala (parasitic)

Thoracica (acorn and stalked barnacles)

Thoracica orders

Sessilia - acorn barnacles

Pedunculata - goose barnacles

Ecology of barnacles

Sessile suspension feeders using modified cirri to generate feeding current

Important on rocky shores

Biofouling

Food source for humans in Spain - delicacy

Cirripedia reproduction

Hermaphrodites - do not usually self fertilise

6 naupliar stages and a cypris larvae (locate settlement site)

Class Copepoda

13000 species - 10 orders

Calanoida

Cyclopoida

Harnacticnida

Gelyenorad

Misophrioida

Monstrilloida

Mormonilloida

Platycopioida

Poecilostomatoida

Siphonostomatoida

Sea lice

Lepeophtheirus salmonis

most damaging to the salmon farming industry

Free-living copepods

median eye present in adults

cephalothorax contains both antennae and mouthparts

dominate zooplankton biomass - most abundant metazoans in the ocean maybe planet

Planktonic copepods

calanoids and cyclopoids

Ontogenetic vertical migration

when copepods change their position in the water column based on the life stages

Malacostracans features

30000 species

calcified exoskeleton

Head, thorax, abdomen, telson

5 segments in head, 8 in thorax and 6 in abdomen

Malacostracan physiology

highly centralised nervous system

large brain - connected to ganglia

green glands - osmoregulatory and excretory function

two chambered stomach - gastric mill

3 malacostracan sub-classes

phyllocarida - 1 living group

hoplocarida - living members only in order stomatopoda

eumalacostraca - all others (crabs, lobsters, prawns etc)

Order stomatopoda

400 species, Mantis Shrimp

monogamy in some species

spearers and clubbers

extraordinary colour vision

Eumalacostracan superorders

Syncarida - freshwater

Peracarida - Isopods and amphipods

Eucarida - crabs and shrimps

Order Isopoda

dorsoventrally flattened

4500 marine, 500 freshwater, 5000 terrestrial species

Pleopods used for gaseous exchange

Important parasites - replace the tongue in fish

Order Amphipoda

5500 species - 100 families

laterally compressed

no carapace

mostly marine detritivores/scavengers

Gammaridae

90% of all amphipods

all aquatic environments

include sand hoppers

ecologically important

epibenthic

Eucarida orders

Euphausiacea - krill

Decapoda - crabs, lobsters, shrimp

Euphausiacea

85 species all marine - make up greatest animal biomass on earth

large gills

larval stages vertically separated

photophores - bioluminescence

Order Decapoda

15000 species - crayfish, crabs, lobsters, prawns, shrimp

cephalothorax always covered by a carapace, which forms a branchial chamber, protecting the gills

five pairs of pereopods

chelipeds - claws

crustacean appendages are

biramous

gills are endopodites of the thoracic limbs

exopodite - external ramus

what respiratory pigment do decapods and stomatopods use

haemocyanin

Decapod reproduction

mating occurs after moulting

sexes attracted by pheromones

fertilisation internal in brachyurans (crabs)

most other species eggs are fertilised when laid

Malacostracan chromatophore

branched but non-contractile

morphological colour change

Long-term

Loss of formation of pigments or chromatophores

Physiological colour change

rapid change in colour caused by changes in concentration or dispersion of granules

common in UK rock pools

Prawns - Palaemon spp.

Brown shrimp - Crangon crangon

Velvet swimming crab - Necora puber

Shore crab - Carcinus maenas

Brown crab - Cancer pagurus

Porcelain crab - Porcellana platycheles

Male vs Female crustaceans

abdominal flap on crabs - wider and larger on female

female lobsters have two swimmerets males have one