Sensory ecology Flashcards
Sensory info in marine systems?
Photic zone = visual stimuli. Light attenuates rapidly (esp red light).
Saltwater = ionised solution = conducts electrical charge.
Water = solvent = carries chemical cues.
Molecular complexity declines w/ distance = animals climb complexity ladder to find source.
Water motion + particle velocity indicates flow + turbulence (eg: sealion whiskers).
Vibrations + sound travel further than light (eg: blue whales hear ships for 1 day before reaching it).
Marine invertebrate sensors?
Visual systems: Simple light detectors (eg: scallops) to complex eyes (eg: cephalopods).
Electrosense? (eg: freshwater crayfish).
Olfactory systems: Simple (surface smells) to complex (olfactory receptor neurons).
Surface hairs detect flow: Simple (eg: cilia on coral larvae = move towards sound) to complex (eg: copepod antennae).
Accelerometers detect vibrations: Simple (eg: fused-sand statocysts in crabs) to complex (eg: nudibranch veliger statoliths).
Matched filter hypothesis?
Animal signal co-evolves w/ target sensors = sensors develop complexly to pick up signals.
Eg: Cephalopod complex eyes detect complex colour signals.
Marine vision?
Light quality varies w/ depth.
Fish eyes: Fixed pupil (change depth + focus by moving it back + forth). Lens = dense + spherical.
Sharks = muscular iris.
Rods: Low light, deep-sea.
Cones: Resolution + colour discrimination.
- Porphyropsin: Yellow/red. Shallow species.
- Rhodopsi: Blue/green. Deeper species.
- Chrysopsin: Deep blue. Deep sea species.
Marine vision examples?
Striped marlin retina: High acuity + colour recognition looking forward + up. Blue vision for dim objects looking down. Can warm eyes = visual acuity in cold water = faster (predators).
Lemon sharks: Ontogenetic shift from porphyropsin (juveniles live in mangroves) to rhodopsin (adults live on reef).
Engraulids + salmonids detect polarised light = acuity (turbid water + dawn/dusk) + orientation/long-distance navigation.
UV vision?
Lemon damselfish UV markings = individual recognition. UV signals relate to health + mating.
Juvenile trout UV vision to find Daphnia prey in murky water.
Cuttlefish + stomatopods: Polarised communication channel (eg: mantis shrimp).
Sharks: Reflective guanine crystals between sclera + retina = amplifies light at night.
Electroreception?
Evolved 500MYA. Lost + re-evolved multiple times.
Found in non-teleost fish + some teleosts,
Receptor cells derived from hair cells in acousticolateralis system.
Ampullary receptors vs tuberous receptors?
Ampullary receptors (passive detection):
- Lampreys, sharks, coelacanths, sturgeons, + some bony fish.
- Ampullae of Lorenzini = pits around nose (hair cell w/o hair). Connected to surface by conductive, gel-filled canals.
- Detect low-frequency EMFs (under 25Hz).
- Used for predator-prey detection + mate choice.
Tuberous receptors (active hunting):
- Epidermal depressions.
- Detect high-frequency EMFs (50-2000Hz).
- Not found in marine fish.
- Detects EMFs from muscle-firing of prey.
Magnetoreception?
Earth’s magnetic field modified by regional features (eg: volcanoes).
Local features (eg: minerals in seabed) = small-scale heterogeneity.
Sharks + rays = electroreception.
Stingrays can forage in lab in response to magnetic cues.
Magnetite (polarised, iron-based compound) found in tuna + salmon heads. Indirectly detects magnetic fields.
Iron content of lagenal otoliths could enable magnetoreception.
Chemoreception?
Fish have paired olfactory chambers w/ incurrent + excurrent nostrils.
Lined w/ folded epithelium. Receptor cells sensitive to amino acids, bile acid, + pheromones.
Salmon, eels, + lampreys imprint on rivers.
Clownfish imprint on natural habitat - seek anemones their embryo developed around (epigenetics?).
Male deep-sea anglerfish - enlarged olfactory organs, nerves, + lobes = search for females.
Mechanoreception?
Specialised cilia bundles w/ range of hair cell lengths = informs on signal strength.
Relative movement of kinocilium + sterocilia generates nervous impulse (greatest when moving in same direction).
Lateral line system (motion detection).
Inner ear (balance + hearing).
Lateral line system?
Detects vibrational energy (eg: currents, obstacles, prey, predators, shoalmates).
Neuromasts covered w/ gelatinous cupula.
Superficial neuromasts (slow-moving water) + canalised neuromasts (fast-moving water).
Inner ear?
3 dense otolith pairs + semi-circular canals. Organised sensory otolithic membrane.
Swimbladder coupling: Near to ear (cod) or extensions (holocentrids + clupeids) = when sound passes through fish, vibrates air in swimbladder = vibrations passed to otoliths.
Sharks sensitive to low frequencies.
Hierarchy of senses?
Eg: French grunt juveniles develop in mangroves + seagrass, then move to reef.
Acoustic cues: Reef noise determines where coast is.
Olfactory cues: Seagrass + mangrove smell locates optimal habitat for development.
Visual cues: Can locate shoalmates.
Siebeck et al (2010).
Thought UV signals had to be broad + bold because prone to scattering + low no. of UV-sensitive cones.
But Ambon damselfish have fine-detail UV facial patterns for species discrimination + possibly status.
UV = secret communication channel from predators.
Common predators (eg; wrasse) block UV transmission to enhance contrast + protect retinas from UV damage.
