benthic invertebrates, nekton Flashcards
some Cetacea, Pinnipeds & Sirenia
state roles of benthic invertebrates in ecosystem functioning
- 2° production
- nutrient recycling
- habitat structure
- grazing
- predation
the taxonomic group ‘Phylum Cnidaria’
2 body forms:
- medusae (jellyfish like)
- polypoid (anemone like)
^have radial symmetry & are diploblastic
diploblastic animals
have body derived from only 2 embryonic cell layers:
- ectoderm
- endoderm
… but no mesoderm
state and describe cnidarians key feature
nematocysts
- large organelles produced from Golgi apparatus
- … as secretory product within a specialized cell (nematocyte / cnidocyte)
- nematocysts: used for prey capture and defense and locomotion
cold water corals: Lophelia pertusa
- these reefs provide habitat for variety of species and living and dead coral skeletons provide biodiversity hot spot on edge of continental shelf
- lives between 80-3000m deep
- found in west scotland and ireland
- damaged by fishing and v delicate & grows slowly => long time for them to recover
sea pens: Anthozoa
each sea pen is a colony of polyps (cnidarians with polypoid shape)
marine invertebrates
- porifera -> sponges
- cnidaria -> jellyfish, anemones, corals
- ctenopora -> comb jellies
- polychaeta -> bristle worms (annelida)
- mollusca -> polyplacophora, bivalves, gastropods
- echinodermata -> starfish, brittle stars, sea urchins, sea cucumbers
- crustacea -> decapods, seed shrimp, krill, isopods, barnacles, copepods
- hemichordata -> balanoglossus, saccoglossus
hemichordata
2 body plans:
- large, solitary acorn worms -> class Enteropneusta
- filter-feeding colonies of the class Pterobranchia.
nutrient recycling
- way in which elements are continuously being broken down and/or exchanged…
- … for reuse between the living and non-living components of an ecosystem
grazing
method of feeding
where herbivore feeds on low-growing plants such as grasses or other multicellular organisms (eg. algae)
nekton
organisms that can move independently of currents
importance of nekton
- nektonic fish of critical importance to world food supply
- large nekton can profoundly influence marine communities
- important in harvests (current and historical)
epipelagic countershading
- most epipelagic organisms have ‘countershading’
- they’re bicoloured: dark on top, silvery on bottom
- allows organisms to blend into darker water below and lighted surface above when other organisms look down or up at it
eg. tuna
holoepipelagic organisms
- spend entire lives in epipelagic zone
- often lay eggs and have epipelagic larval life
- eg. shark, tuna, ocean sunfish
meroepipelagic zones
- spend part of lives in epipelagic zone
- visit this region to find prey
- spawn in inshore / freshwater regions
- eg. herring, salmon
photophores
- organs used by fish and invert. to produce light by chemical reaction / through bioluminescence
- most fish that use photophores live in deep sea where light is limited
morphological features of nekton in mesopelagic zone
- rarely exceeds 10cm long
- good teeth and large mouth
- large, light sensitive, black eyes
- has photophores
morphological features of nekton in abyssopelagic zone
- “species-specific pattern of photophores”
- small flabby, soft, **nearly transparent flesh **supported by weak bones
- oversized mouth
cephalopods
- 2 sub-classes: Nautiloidea & Coleoidea
- coleoidea…
-> superorder: Decapodiformes (squid & cuttlefish)
-> superorder: Octopodiformes (octopus & vampire squid) - semelparous -> breeding only once in a lifetime (squid, cuttlefishes & octopuses)
- iteroparous -> multiple reproductive cycles over lifetime (nautiluses)
chondrichthyes
fish
skeletons that are mainly made of cartilage
2 sub-classes:
-
elasmobranchii (sharks, rays, skates, and
sawfish) - holocephali (chimaeras)
osteichthyes
fish
“bony fish” -> skeletons mainly made of bone tissue
2 sub-classes:
-
sarcopterygii (lobe-finned fish)
eg. coelacanths & lung fish -
actinopterygii (ray-finned fish)
eg. goldfish & ocean sunfish
pinnipeds
seals
cetaceans
includes whales, dolphins & porpoises
cetaceans key characteristics
- fully aquatic lifestyle
- streamlined body shape
- often large size
- exclusively carnivorous diet
sirenia and their characteristics
sirenia is an order
sea cows
- fully aquatic, herbivorous mammals
- inhabit swamps, rivers, estuaries, marine wetlands & coastal marine waters
2 distinct families:
-
Dugongidae -> 1 sp: dugong
-> SE Asia, Australia & East Africa -
Trichechidae -> inc all manatees
-> 3 sp
-> Amazon, West Indian &West African
compare and contrast dugong and manatees
dugong:
- short flippers
- whale-like tail (fluke)
- fusiform body
manatee:
- long & flexible flippers
- spatulate tail (fluke)
- rough skin + algae
- barrel shaped
cold-blooded vs. warm-blooded fish
cold blooded = poikilothermic (most fish are):
- bodies same temp as env
- not fast swimmers
warm blooded = homeothermic:
- found in warmer env
- helps them capture prey
adaptations of deep-water nekton
like in finding nemo
- mainly fish that consume detritus / each other
- lack of abundant food
- bioluminescence – photophores
- large, sensitive eyes
- large sharp teeth
- expandable bodies
- hinged jaws
- counterillumination
counterillumination
- active camouflage seen in marine animals eg. firefly squid & midshipman fish
- producing light to match their backgrounds in both brightness & wavelength
what are the predictable env for nekton
LIFE HISTORY - how they live
- iteroparous -> producing offspring more than once during its lifetime
- long-lived (longevity)
- delayed maturity
- low-reproductive rates
- migratory
life history
series of changes undergone by organism during its lifetime
examples of nekton’s longevity
-
Osteichthyes:
e.g. orange roughy -> ~150 yrs -
Chondrichthyes:
(oldest known vertebrate): greenland shark -> ~400 yrs
-> based on radio-carbon dating eye lenses
marine reptiles
- ectothermic (cold-blooded)
- covered with scales
- breathe air with lungs
- have specialised salt glands -> excrete excess salt taken in from seawater
marine mammals
- land-dwelling ancestors
- warm-blooded
- breathe air
- hair/fur
- have kids young
- mammary glands for milk
major marine mammal orders
- Carnivora -> pinnipeds, sea otters, polar bears
- Sirenia -> manatee, dugong
- Cetacea -> whales
order Carnivora
- prominent canine teeth
what it includes:
- sea otters
- polar bears
- pinnipeds
– Walruses – Seals
– Sea lions – Fur seals
seals vs. sea lions & fur seals
- seals lack prominent ear flaps
- seals: smaller front flippers
- seals: fore flipper claws
- diff hip structures
- diff locomotion strategies
order Sirenia
- herbivores
what it includes:
- manatees
– coastal areas of tropical Atlantic Ocean - dugongs
– coastal areas of Indian and w. Pacific Oceans
order Cetacea
Whales, dolphins, porpoises
- elongated skull
- blowholes on top of skull
- few hairs
- fluke – horizontal tail fin for propulsion
Cetacea adaptations
- adaptations to ↑ swimming speed
- adaptations for deep diving
- use oxygen efficiently
- muscles insensitive to buildup of CO₂
- collapsible lungs
Suborder Odontoceti (toothed)
of order Cetacea
- dolphins, porpoises, killer whale, sperm whale
-
echolocation to determine distance and direction to objects
-> determine shape, size of objects
dolphins vs porpoises
Dolphins:
- larger, more streamlined shape
- longer rostrum (beak)
- falcate dorsal fin (hooked)
- pointy teeth like killer whales (orca)
Porpoises:
- smaller, more stout body shape
- blunt snout
- triangular, smaller dorsal fin
- blunt or flat teeth
echolocation
- toothed whales send sound through water
- sound is reflected, returned to animal, and interpreted
- evolved inner ear structure may help toothed whales pick up sounds
- ↑ marine noise pollution may affect cetacean echolocation
- good vision of marine mammals limited by ocean conditions
- mammals emit clicks of diff pitches
-> low freq – great distance
-> high freq – closer range - dolphins can detect schools of fish at more than 100m
Suborder Mysticeti (moustached whales) of order Cetacea
- baleen whales
- blue, fin, humpback, gray, right whales
- fibrous plates of baleen sieve prey items
- vocalized sounds for various purposes
gray whale migration
- 22,000 km annual migration from coastal Arctic Ocean to Baja California & Mexico
- feeding grounds in Arctic (summer) -> near Alaska
- breeding & birthing grounds in tropical eastern Pacific (winter) -> near Mexico
Nekton life-histories consequences
- scale of movement requires global efforts “conserving a moving target”
- over-exploitation and longevity:
-> orange roughy collapsed stock - bycatch impacts e.g. albatross
causes of nekton life-histories
FOOD
- selection for large size – takes time to grow
- resources patchy
- travelling long distances is necessary
- may take yrs to learn how to find food
- selection will favour slow turnover rates
