Locomotion 2: Cilial-based Locomotion in Marine Larvae

Locomotion 2: Cilial-based Locomotion in Marine Larvae

1. Neuronal control of Cilial Locomotion

   • Braubach et al (2006) investigated the Neuronal control of the velum in Illyanassa obsoleta and its effect on swimming activity and cilial motion
     • Velum is the structure that is used in the movement around the WC
       • Velum has a very complex neuronal structure and is a very important trait to have so understandably has high energy nput in its creation
     • Measured cilial beats using photodiodes,
       • Found two main neurotransmitters that had an effect on cililal beat frequency
         • Serotonin increased cilial beat (dose dependent)
         • Dopamine decrease cilial beat frequency
     • Swimming activity mimicked that of the Seratonin and the Dopamine effects
       • Neurotransmitters affect swimming behaviour
     • When n antagonist was added into the water neurotransmitters stopped working
       • Proves neurotransmitters work endogenously (inside the body)
   • Conzelmann et al (2011) investigated neuropeptide control in Platynereis larvae
     • Whether they inhibit or promote ciliary activity
       • Position in the WC controlled by neurotransmitters
         • this could be controlled by other factors e.g. pressures, chemicals.
       • This proves direct sensory - motorary function

2. Effects of Temperature and Viscosity

   • Podolsky & Emlet (1993) looked at the effects of temperature and viscosity on swimming speed in Sand dollar larvae
     • Tethered larvae and measured theyre swimming speed in three temperatures
       • 12 and 22 degree water and then 22 degree water with an increased viscosity to mimic that of 12 Degree water
         • This then separated the effects of viscosity from the effects of temperature
     • The higher temperature treatment showed an increased swimming speed of 40%
       • water movement was increased by 35%
       • 40% swimming speed and 55% water movement was due to the change in viscosity
       • This showed an interesting component to viscosity - have to look at all aspects

3. Cilial-based Locomotion in Encapsulated larvae: The Embryo Stir Hypothesis

   • Goldberg et al (2008), Kuang et al (2002) The Embryo Stir Bar Hypothesis
     • movement within the snail egg capsule is to stir up oxygen within the egg capsule
       • Nutrient uptake within the egg
     • there is no diffusion gradient at the edge of the egg, movement leads to gradient being formed
       • movement leads to equal distribution of deoxygenated solute
     • Testing the ESBH
       • Pulmonate Gastropods used to test ESBH
         • there is a metabolic cost to rotating so the spp show decline in rotations with aeration
       • When exposed to hypoxia, stirring increased to boost oxygen stirring
   • Gastropods neurones were destroyed to see how it affected the stir response
     • Found that rotations did not increase during hypoxia events
       • added mianserin (antagonist to serotonin)
         • this suggested serotonin was used in ESBH

4. Role of Locomotion in the Evolution of of non-feeding larval Echinoderms

   • Hoegh-Guldberg & Emlet (1997) looked at energetics of development in Lecithotrophic and planktotrophic sea urchins
     • Lecithotrophic are much larger at the start due to their maternal provisioning
       • They also move through development much quicker than Planktotrophic
     • Generally a greater investment in lecithotrophic eggs = 2% compared to 91% investment of developmental energy requirements
     • Also looked at how energy is used within the organism
       • Planktotrophic organisms tend to be metabolsing for greater lengths of time
         • energy is needed to input into moving around and feeding
           • Often as much as 50% of the energy budget with returns of 4-6% from feeding
     • No Real difference energy-wise between the two life histories.