Pinnipeds Flashcards
What defines a pinniped?
Eight defining synapomorphies e.g. Distinguishing features
What are the 8 features?
Large infraorbital foremen
Maxilla makes significant contribution to the orbital wall
Lacrimal fused or absent
Greater and lesser humeral tuberosities enlarged
Deltopectoral crest of humerus strongly developed
Short robust humerus
Digit I on hand emphasised
Digits 1 and V on foot emphasised
What is a pinniped?
Members of the order Carnivora.
3 families ( orariidae, odobenidae, phocidae)
Compromises - 28% of marine mammals
33 different species
Estimated 50 million individuals
Examples of otariidae (eared seals)
California sea lion
Galapagos fur sea
Example of odobenidae
The only species is the walrus
Phocidae
90% of all pinnipeds
The true seals or earless seals
Evolution of pinnipeds
One hypothesis suggests that pinnipeds are diphyletic ( defendant from 2 ancestral lines) with walruses and orariids sharing a recent common ancestor with bears and phocids sharing one with muskeloidea. However genetic evidence suggest it is nonsense
The evolutionary link to terrestrial mammals was unknown until puijila darwini was discovered in 2007.
Locomotion in pinnipeds
Both terrestrial and aquatic locomotion
The three distinct patterns of pinnipeds swimming are recognised yet all create thrust with the hydrofoil surface of their flippers
When swimming these hydrofoils orientated at an angle to the direction of travel, producing thrust parallel to the direction of travel and generating lift perpendicular to the direction
Locomotion in otariids
Less adapted to the aquatic lifestyle since they are primarily breed on land and hall, lamp, more frequently than phocids
They have proportionately much larger foreflippers and pectoral muscles and have the ability to turn the hind limbs forward and walk on all fours
They have extensive movements of the head and neck occurs in terrestrial locomotion
The swimming power derived from the use of flippers more than the whole body movements 
Locomotion in phocids
Swim by sideways movements of their bodies using their hind flippers, whilst foreflippersare used for steering
Hind flippers are also bound to the pelvis in such a way that they cannot bring themunder their bodies to walk on them = clumsy
Thermoregulation in pinnipeds
Blubber is the main insulating tissue
Blubber is also an energy store and used for buoyancy
Blubber is penetrated by vascular beds so heat loss can be controlled via counter current heat exchange
Lower thickness changes in response to environmental temperatures
New seal pups do not have blubber, but do have thick layers of hair and higher rates of metabolism
Osmoregulation of pinnipeds
Due to inhibiting marine environment, the animals internal fluid composition differs from the external environment
marine mammals consume water rich fish and marine invertebrates, which are composed of 70 to 80% water as well as electrolytes and nitrogen
They gain water from metabolise in food and blubber and they also lose water through evaporation, excretion and respiration
Metabolic water
1.07g of water is generated for every gram of fat oxidised
0.56g of water per gram of carbs
0.39g of water per gram of protein
Three types of vibrissae (whiskers)
Rhinal
Superciliary
Mystical
What are mystacial whiskers?
Arranged in rows on either side of of the nose
Either smooth (O family) or beaded (p family)
Embedded in the upper lip- highly innervated or vascularised
Functional significance for prey location
What are superciliary whiskers?
Located above the eyes
What are rhinal whiskers?
Located on top of the shout
Diving adaptations in pinnipeds
Before diving, pinnipeds exhale to empty the lungs of half the air before closing their nostrils and throat cartilages to protect the trachea
The lungs have airways that are reinforced with cartilaginous rings and smooth muscles, and the alveoli that can completely deflate during deep dives. Can you please can also reinflate the lungs even after complete respiratory collapse.
The heart is moderately flattened to allow the lungs to deflate this way
The middle ear contain sinuses that appear to fill with blood prevent ear squeeze
Diving adaptations- deep dives in pinnipeds
Any remaining air in their bodies is stored in the bronchioles and trachea, which prevents them from experiencing decompression sickness, oxygen, toxicity, and nitrogen narcosis
Pinnipeds of high amount of haemoglobin and myoglobin, stored in their bodies and muscles . Deep dive in species have blood volume is that represent up to 20% of their body weight.
When diving they reduce their heart rate and maintain blood flow to only the heart, brain and lungs
Pinnipeds as predators?
They have similar ‘torpedo shaped’ bodies- which are awkward on land, but graceful in water
Visual predators that also have sensitive whiskers can help them detect pray
Most are generalist and opportunistic feeders, which is dependent on the seasonal variation and pray density
They may hunt solitary or cooperatively, but they don’t have echolocation
Toothed whales (schusterman et al 2000)
Toothed whales evolved a highly advanced system of active biosonar
An echo location system is unlikely to have involved in pinnipeds, choose to the constraints imposed by the obligate amphibious functioning of the pinnipeds auditory system. As a result, these constraints, constraints have not developed highly acute, aquatic, high frequency, sound production of reception systems
However, pinnipeds have evolved enhanced visual, tactile and passive listening skills
Phocidae as predators
Deep drivers = benthic ( bottom feeders)
Females fast during lactation
Otariidae as predators
Shallow diverse with generations of 2 to 3 minutes and feed, mostly on fish in near shore waters
Females forage during lactation
Prey size depends on how they eat their foods
Small fishes under 30cm long are consumed whole underwater
Large fishes above 30 cm long are bought to the surface, shaken violently and reduced to chunks that are swallowed piece by piece
