Sea Snakes Flashcards
(16 cards)
What are the challenges to reinvading the marine environment?
Respiration (rely on air)
Locomotion (dense and viscous)
Thermoregulation (high thermal conductivity)
Osmoregulation (hyperosmotic environment)
What are the two types of sea snakes and what are their characteristics?
Hydrophids: true sea snake, viviparous, fully marine
Laticaudids: sea kraits, semi-terrestrial, oviparous
What are the characteristics of the yellow-bellied sea snake:
- Widely distributed
- Pelagic (passive swimmers)
- Highly venomous
- Typically solitary (slicks of 000’s occasionally)
- Occasionally beach cast
What are the characteristics of the flat-tailed sea krait?
- Niue
- Forages on coral reefs (nook and cranny feeders supported by morphology)
- Lays eggs in intertidal zones (sea caves away from terrestrial predators)
- Docile
- Vulnerable IUCN status
What is the diversity and distribution of sea snakes?
- Only found in Indian and pacific oceans
- Limited to tropical regions
- Limited to surface waters
How do sea snakes avoid thermal regulation challenges of sea water?
- By living in warm regions and in the surface waters (ectotherms that rely on ambient water temps)
What characteristics do sea snakes have to overcome locomotory challenges in water?
- Lateral undulations of body (series of s-shaped curves where the water provides resistance to push them forward)
- Small streamlined head
- Laterally flattened tail
- Reduction of ventral scales (hydrophids)
- Shed skin every 4-6 weeks to reduce fouling
- Valvular nostrils (modified scales that can open and close - adapted for diving)
How are sea snakes able to dive routinely for 30 minutes and up to 2 hours?
They are capable of respiring cutaneously. This is facilitated by low partial pressure of O2 in their arterial blood. They have a network of arteries in their heads to provide enough oxygen to the brain when diving.
What are the alternative hypotheses as to why sea snakes can dive for so long that are wrong?
Anaerobic respiration: no evidence of lactic acid build up; can dive straight after surfacing
Greater O2 concentration in the blood, greater blood volume: marginally better compared to land snakes
Lower metabolism: not much difference compared to land snakes
How do sea snakes deal with osmoregulatory challenges?
They excrete salt through their posterior sublingual gland as they are always ingesting salty prey. They have the largest excretion of salt of all reptiles (alongside marine iguanas)
What are the characteristics of venom in sea snakes?
Evolved 200 mya
Ability to subdue prey
Venom glands are modified salivary glands
Venom is expensive (complex mix of proteins): species that don’t need it lose it (e.g., sea kraits)
Venom is predominantly high in neurotoxins (inhibits action potentials of fish stopping them from respiring)
What type of fangs do sea snakes have?
Proteroglyphous: short, hollow fangs in front of the mouth that are fixed (compared to flexible solenoglyphous fangs)
- Most sea snakes are not dangerous, they withhold venom and give off a warning bite
What are the main impacts on sea snakes?
Habitat loss/modification
Harvesting: meat, skin, traditional medicine
Bycatch: northern Australia prawn industry - trawling = non-selective
Why are sea snakes at risk of threats?
- Low reproductive output: breed every 1-2 years; mature in 1-5 yrs; small brood sizes (< 10)
- Limited distribution and high philopatry
What are some ways to reduce threats on sea snakes?
Bycatch reduction: TEDS = 5% reduction and improves survival; BRDs = up to 80% reduction
MPAs: GBR Marine Park: restriction on fishing; protection of corals; levies on tourists to fund research
What is the anatomy of sea snakes?
Paired organs scattered around the body cavity
Reduced left lung
Elongated right lung: saccular (avascular), bronchial, tracheal
