invertebrates in the pelagic zone

Question 1

provide some characteristics of zooplankton

Answer 1

• protozoa
• size range from 100um to a few metres
• usually capable of some sort of swimming

Question 2

what percentage of the gelatinous body of gelatinous zooplankton is water

Answer 2

95% or higher

Question 3

give some examples of gelatinous zooplankton

Answer 3

1) salps
2) comb jellies
3) true jellyfishes
4) box jellyfishes
5) hydromedusae
6) siphonophores

Question 4

why are blooms of gelatinous zooplankton common

Answer 4

most gelata taxa have an asexual reproductive mode as well as a sexual one allowing them to respond rapidly to pulses in food

Question 5

compare the movement of plankton at the surface and below it

Answer 5

surface - drifting in currents driven by winds
below - drift in currents but able to swim weakly and move vertically in the water

Question 6

what is meant by diel vertical migration

Answer 6

one of the largest migrations in terms of biomass on the planet
occurs where animals in deep water during the day move to shallower waters at night

Question 7

why does DVM occur when it is energetically expensive

Answer 7

the predator evasion hypothesis - better unfed than dead

Question 8

what species are the most abundant metazoans in the oceans

Answer 8

copepods

Question 9

outline the development of calanoid copepods

Answer 9

normally around 12 developmental stages each seperated by a moult
6 nauplius stages
6 copeodite stages
sexually mature adult stage is the last

Question 10

what are the different stages of calanoid copepod development

Answer 10

6 nauplius stages
6 copepodite stages
sexually mature adult is the last stage

Question 11

what are pteropods

Answer 11

shelled and shelless plantonic molluscs with a modifed foot into a pair of wings
suspension feeders
trap particles in mucous covered parapodia

Question 12

what are the different names for shelled vs shelless pteropods

Answer 12

shelled= thecosomata
unshelled= gymnosomata

Question 13

give some examples of why a vast majority of planktonic larvae die

Answer 13

• swept into inhospitable habitats
• eaten by predators
• starvation

Question 14

what is the difference between photopositive and photonegative

Answer 14

+ =near the surface
- = close to the bottom

Question 15

outline larvae distribution in the water colomn

Answer 15

larvae go through one or more stages of photopositive or negative behaviour and show behavioural depth changes to take advantages of local currents and tides

Question 16

outline some characteristics of invertebrate nekton (active swimmers)

Answer 16

• able to move more independently of water currents
• most nektonic animals are fish
• nektonic marine invertebrates are mostly crustaceans and cephalopods

Question 17

what is meant by wasp-waist systems

Answer 17

systems dominated by mid trophic-level species that is thought to exert top-down control on its food and bottom-up control on its predators

Question 18

what are euphausiacea

Answer 18

= krill
generally a few cm long
all marine
exposed gills ventilated by throacic appendages

Question 19

what are the two subclasses of cephalopods

Answer 19

1) nautiloidea = pelagic with external, chambered shell for buoyancy
2) coleoidea

Question 20

what are coleoidea

Answer 20

subclass of cephalodpod = cuttlefish
- 8 arms
- 2 tentacles
mostly benthic
neritic (coastal)

Question 21

what are octopoda

Answer 21

8 armeds
internal shell which is considerable reduced or absent
incirrata- shell absent (benthic)#
cirrata - shell reduced

Question 22

outline some characteristics of the humboldt (jumbo) squid

Answer 22

up to 2.5 m in length
shoals of over 1000 animals
depths of 200-700 m
mainly feeds on micronekton
evidence of cooperative hunting