pinnipeds, turtles & basking sharks Flashcards
1
Q
basking sharks info
A
- 2nd largest fish
- max length ~1200cm
- max age ~50 yrs
- gestation 1–3.5 years -> litter size 1–6 pups
- length at birth ~150–200cm
-
passive filter-feeders
-> feeds on zooplankton (copepods, crustacean larvae, fish eggs) - aggregates seasonally in temperate continental shelf waters where there is ↑ zooplankton (oceanic & thermal fronts, headlands, islands & enclosed bays with strong tidal flow)
- known to have long seasonal migrations -> inc transoceanic & transequatorial (crossing equator) movements
2
Q
basking sharks historical threat
A
Basking sharks historically targeted by fisheries…
- for oily rich livers
->eg. Irish fishery ~took 12,360 sharks from 1947 and 1975
3
Q
basking sharks modern threats
A
- basking sharks also still caught as bycatch in nets & trawls
-> low reporting rates - can also easily become entangled in fishing nets & ropes
- v sensitive to disturbance and harassment by ppl - propeller & boat strikes remain a danger
4
Q
marine turtles info
A
- long-lived
- reptiles
- natal philopatry -> return to area the animal was born in
- site fidelity -> tendency to return to prev visited locations
- migratory, navigate
- temp-dependent sex determination
5
Q
leatherback turtle
A
- Dermochelys coriacea
- globally vulnerable 2013
- native UK fauna (animals of UK)
- eats jellyfish (& plastic)
- esophageal papillae
- pelagic throughout life
- can thermoregulate by ↓ blood flow to extremities in cold (large size helps)
- deepest diver 1000m
6
Q
hawsbill turtle
A
Eretmochelys imbricata
- globally: Critically Endangered (2008)
- hawk-like beak
- feeds on sponges on coral reefs – vulnerable to climate change
- nests across tropics but not in large numbers
- taken for tortoiseshell
7
Q
kemp’s ridley turtle
A
Lepidochelys kempii
- IUCN: Critically Endangered (2019)
- eats crabs
-
arribada nesting -> mass nesting event
-> come ashore to nest & lay eggs on beach - only nested in Gulf of Mexico
-> huge project to relocate to new areas
-> now nesting in Texas & Florida
8
Q
olive ridley turtle
A
Lepidochelys olivacea
- IUCN: Vulnerable (2008)
- eats fish and salps (type of zooplankton)
- arribada nesting
- eggs harvested legally at Ostional, Costa Rica
9
Q
loggerhead turtle
A
Caretta caretta
- IUCN Vulnerable (2015)
- eats crustacea and fish
- large head/jaw
- infaunal mining (foraging strategy)
- bycatch -> BIG issue
10
Q
flatback turtle
A
Natator Depressus
- IUCN: Data deficient
- eats jellyfish & invertebrates
- smaller clutch size (no. eggs in nest)
11
Q
green turtle
A
Chelonia mydas
- IUCN: Endangered (2004)
- feeds on seagrass & algae
- edible turtle -> most commonly eaten
12
Q
turtle reproduction
A
- mating occurs in water
- sperm stored
- oviparous -> lay eggs
- eggs are soft shelled
-> water & gasses can move across membrane & are source of Ca - eggs retained internally & all laid together as clutch
- no parental care
- produce 1000s of offspring
13
Q
turtle navigation
A
hatchlings orientate to light, slope & perpendicular to waves
- use Earth’s magnetic field
- imprint on location / sand / magnetic fields
- been shown to orientate in “offshore direction” suggest innate magnetic cues once offshore
14
Q
pinnipeds info
A
- most numerous marine mammal group (28% of marine mammal diversity)
- ~50 million worldwide
- 90% phocids (true seals)
- found in all major oceans (& some freshwater)
- all have amphibious lifestyle -> spend part of life in water, part on land
15
Q
when did pinnipeds first appear? (in N. Pacific first)
include their ancestors
A
- late oligocene age (27-25 Ma)
-
monophyletic group
-> inc organisms with common ancestor & closely related.
-> also have similar genetics - descendents from arctoid ancestors (mustelid, bear, dog)
