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Written by Elizabeth Hawkins for the Southern Cross University Biology & Conservation of Marine Mammals Unit 2013

Adaptation

Anatomy

Muscular system Anatomical system that allows animal to move

Specifically adapted to the marine environment

E.g. Blowhole: muscular flap that provides airtight seal

Myoglobin – oxygen-binding protein stores oxygen

Skeletal System Light & ‘spongy’ bones

Have forelimbs

Remnant hind limbs

Collapsible rib cages

Respiratory System Cetaceans exchange 85-90% of air

in one breathe (humans 15%)

More red blood cells than human

Oxygen rich blood (high levels of oxygen in muscles)

Muscles can function anaerobically

Can tolerate high levels of CO2 & can continue to dive with no oxygen

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Circulatory System Heat Exchange System (Thermoregulation)– keeping

warm in a cold sea

- Arteries in the extremities; dorsal fin, pec fins & tail flukes

- Countercurrent heat exchange maintains body heat

- Heart rate slows during a dive to lower metabolism

Diving Adaptation

Digestive System Three chambered digestive system

Fore stomach begins digestion of food

Major digestion takes place in second (main) stomach

Pyloric stomach final digestion before transferred into the intestinal system

Renal System The kidneys of dolphins are specially designed to filter

the high levels of salt

Multiple renules in kidneys that act as a separate kidneys and filer the salt

Cetaceans stay hydrated from the food they eat

Reproductive System

•Internal reproductive organs •Large testes •Unique feeding behaviours

The Brain Large brain mammals

Brain – body size ratio (encephalization quotient (EQ)) is one of largest in animal kingdom (next to humans)

Large cerebellum

Cerebral hemisphere have larger surface area & nerve cells than humans

Brain atlas: https://www.msu.edu/~brains/brains/dolphin/movies/tcor80.mov

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Fewer fibres (corpus callosum) between hemispheres - likely linked to semi-hemisphereical sleep patterns

Vestibulocochlear nerve and acoustic regions of brain larger than terrestrial animals

Large portion of brain dedicated to acoustic reception & information processing

video

How & Why Cetaceans Die?

Necropsy Assessment & insight into cause of death

Record relevant observations from internal and external assessments

Management Implications

Safety Personal & public safety are

primary considerations

Zoonotic organisms

Protective equipment (gloves, glasses, bandage wounds, face masks etc.)

Chemical handling

Disposal of carcass

Presence of bystanders

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Procedure History of animal – field assessment

Transport/storage

Necropsy

Document everything

Animal History (field information) Field assessment

Date & time of stranding

Location

Environmental conditions

Species identification

Behaviour before & during

Single or mass stranding

Time of death

Level of decomposition (fresh, moderate, advanced, mummified)

Euthanized or natural death

External scarring/lesions

Parasites

Debris/ entanglement

Record of trauma

Mode of carcass storage prior to necropsy

Morphometrics Allows for understanding of species age estimation, growth

rate, reproductive status & disease processes

Body measurements (in cm) - e.g. Length, girth, dorsal length etc.

Age estimation

Teeth – worn, missing

Teeth count upper & lower jaw & obtain sample

Sex determination

Female

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Male

Eyes – discolouration, injuries, discharge

Blow hole – description, discharge etc.

Lactation

Measure lesions & scars

Sample parasites

Photographically record all features

Dolphin pox Lamprey bites

Necropsy Procedure Dissections & Incisions

Initial incisions – pectoral fin/shoulder blade – anus

Blubber thickness (measure mm), colour & texture

Muscle – colour & volume

Remove rib cage & systematically assess

Assessment of internal organs – trauma, tumours, haemorrhaging/trauma, parasites & cysts

Lungs – colour, ‘sponginess’, presence of fluid ect.

Heart

Diaphragm

Stomachs - look for contents & degree of digestion & volume of fluids

Fore Stomach

Main Stomach

Pyloric Stomach

Liver – colour & texture

Kidney – colour & texture

Spleen

Intestines – colour & contents

Reproductive Organs – look for abnormalities & pregnancy

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Stomach

Liver

Intestines

Ventral

Dorsal

Kidney

Pyloric Stomach

Intestines

Adrenal

Sampling Sampling methods should ensure that differential

diagnosis can be considered

Labels must be clear & systematic

Samples of: Blood (immediately after death only)

Blubber

Muscles

Teeth

Organs – Lungs, liver, kidney, heart

Parasites, tumours, cysts

Other samples of interest e.g. Fluid excretions, milk etc.

Brain – fresh carcass only

Specimen Collection & Storing Sample Storing Check

Teeth Ageing Freeze

Skin Genetics 70% ethanol or 10% DSMO or salt or freeze

Toxicology: Blubber, liver, muscle, kidney

Contaminants Freeze samples in foil & place in zip-lock bag

Swabs

For fluid or unusual discharge

Freeze

Histopathology: Lung, liver, kidneys, heart

10mm slices; 10% buffered formalin

Blood Chill (obtained at time of death only)

Parasites Identification 10% formalin or 70% ethanol

Stomach Contents

Identification 70% ethanol or freeze

How to assess cause of death Human interaction

Field Observations

Necropsy assessment

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Causes of death Natural

Illness, disease, viruses

Fungal & bacterial infestations

Predatory attach

Malnutrition/starvation

Congenital defects

Trauma

Dehydration & sunburn

Prenatal/neonatal mortalities

Old age

Human Related/Induced

Toxins & Pollutants

Fishing Interactions

Ship/boat Strike

Sonar Exposure

Quality of food (habituation to human food sources)

Gun shot wounds

Stab wounds/ knife cuts

Gas embolism?

Entanglement

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Management Implications Management of human-related causes

Monitoring of population health

Conservation initiatives

Useful References Dolphin Anatomy & Pathology: http://shutterbug.ucsc.edu/dolphin

**Pugliares, K. R., Bogomolni, A., Herzig, S. M. et al. (2007) Marine Mammal Necropsy: An introductory guide for stranding responders and field biologists, Technical Report, Woods Hole Oceanographic Institute, USA

https://www.msu.edu/~brains/brains/dolphin/labeled.html

All in the Mind – Radio National “diving into dolphin heads: science, rights & ethics’ (available online)_