Fishing Spiders and Fishing Spiders and Prey DetectionPrey Detection

Genus Dolomedes Approximately 100 species world wide Large spiders that can run on the surface of water and even dive or swim under water Habitat - Littoral zones of lakes, ponds, or in pools of sluggish streams - Found with its entire body on the water anchored to

shore with only a silk thread, or resting on the surface with legs anchored on a leaf or rock near the shore

Fishing spider anchored by silk Fishing spider anchored by silk threadthread

Wind & Prey WavesWind & Prey Waves

Maximal amplitudes of prey generated waves lies in the

range 2.2 ± 0.4 µm to 80.6 ± 17.9 µm. If one compares the amplitudes of wind-generated waves with the maximum value given for prey waves, even the smallest amplitudes of wind waves are ten times greater than the maximal amplitudes given for prey waves. (Lang 1980)

Distinction of wind-generated waves from prey waves cannot depend on the amplitude of the wave signals

Amplitudes of prey verses wind generated waves

Wind & Prey WavesWind & Prey Waves- Maximum energy contact of wind produced waves lay in

the frequency region of 1.4 ± 0.56 Hz

- Upper frequency limits of the 60 dB bandwidth of wave

values of 8.2 ± 1.2 Hz

- Frequency components above 10 Hz were not found

- Prey waves are detected on the basis of their high frequency components relative to wind generated waves.

(Bleckmann and Barth 1984)

Typical power spectra of wind verses prey generated waves

Preferred waiting sites for Preferred waiting sites for DolomedesDolomedes

Dolomedes may prefer sites that are closer to the shore and foliage due to

- wind generated waves on the water surface arrive

with considerable regularity, providing a pattern

against which the irregular vibrations of prey may

stand out more readily.

- Frequency difference between wind and prey

waves is substantial. Therefore, prey waves are

scarcely masked by higher amplitude wind-generated

waves.

Water striders use species-specific water vibrations for territorial communication

Some references• Australian Museum on- line 2002

http://www.amonline.net.au/spiders/toolkit/hairy/sensing.htm

• Bleckmann, H. & F. G. Barth. 1984. Sensory ecology of a semi-aquatic spider (Dolomedes triton). II. The release of predatory behavior by water surface waves. Behav Ecol Sociobiol, 14: 303-312.

• Bleckmann, H & Rovner, J.S. 1984. Sensory ecology of a semi-aquatic spider (Dolomedes

triton). Behav Ecol Sociobiol, 14:297-301

• Gorb, S.N. & Barth, F. G. 1994. Locomotor behavior during pry-capture of a fishing spider, Dolomedes plantarius (Araneae: Araneidae): Galloping and stopping. J. Arachnol. 22, 89-93.

• Lang, H.H. 1980. Surface wave discrimination between prey and nonprey by the back swimmer Notonecta glauca L. (Hemiptera, Heteroptera). Behav Ecol Sociobiol 6: 233-246.

• Suter, R. B., Rosenberg, O., Loeb, S., Wildman, H., & Long, J. H. 1997. Locomontion on the water surface: Propulsive mechanisms of the fisher spider, dolomedes triton. Journal of Experimental Biology 200, 2523-2538.

• Suter, R. B., & Wildman, H. 1999. Locomotion on the water surface: Hydrodynamic constraints on rowing velocity require a gait change. Journal of Experimental Biology

202: 2771-2785.

• Zimmermann, M. & Spence, J. R. 1989. Prey use of the fishing spider Dolomedes triton (Pisauridae, Araneae): an important predator of the neuston community. Oecologia

80: 187-194.

Crayfish Stretch Receptors

• Fig. 4. Digging behaviour of Bathynomus doederleini. Video frames show (A) the start of digging of a burrow, (B) advancing towards the bottom, using the thoracic legs and beating swimmerets, (C) reversing direction by rolling up to leave the burrow and (D) creeping out of the burrow. This animal was 11 cm long.

Crayfish (cont)• Fig. 5. (A) Lateral view of the spatial organisation of

thoracic and abdominal stretch receptors. Segmental stretch receptors are located on the dorsal side and extend axons that run towards the central nervous system (CNS) via nerve 3 (N3). Note that, as in crayfish, the axons of the abdominal stretch receptors project to the eighth thoracic ganglion. (B) The CNS and central projection of the axon of TSR-2. The CNS is depicted dorsally, and the CNS posterior to TG3 is not drawn, and the oesophageal connectives are interrupted. Ascending and descending central projections of the axon of TSR-2 are shown (camera lucida drawing). This was revealed by electrophoretically applying Lucifer Yellow to the centrifugal cut end of N3. (C) Ventral view of the organisation of thoracic stretch receptors. Thoracic stretch receptors are located dorsally and bilaterally. Dendritic branches from the receptor cell of TSR-1 innervate the extensor muscle, while those of TSR-2 entwine with the receptor muscle-like strand, which is exaggerated in size. TSR-3 to TSR-7 have two receptor cells and a single receptor muscle. AS, abdominal segment; ASR, abdominal stretch receptor; TS, thoracic segment; TSR, thoracic stretch receptor; ROS, rostrum; Deutero, deuterocerebrum; Mx, maxillary nerve; Proto, protocerebrum; Trito, tritocerebrum; TG, thoracic ganglion.

insects

Cockroach escape behavior triggered by wind gust of predator

The roach’s own walking movements and random wind gusts create larger amplitude air movements, but the acceleration of air is never as great as that from a toad strike.

Very fine, long hairs provide exceptional sensitivity

Air-detector hairs organized to provide directional information

Fly flight: mechanoreception used as a gyrosense

Drosophila melanogaster

Calliphora vicina

Insects first organisms to develop flight around 300 million years ago - subsequently lost in some families (lice, ticks). Earliest flies appeared 225 million yrs ago; 120,000 known species alive today; members of the Diptera are distinguished by the reduction of the pair of hind wings to club-like organs called halteres.

In 1714, William Derham surgically removed the halteres and discovered their role in flight stabilization. Fraenkel & Pringle identified halteres as having a gyroscopic function in fly flight in 1938.The US military currently spends several million $ a year to fund efforts to build a “robofly” that is built using Drosophila as model.

Two main Diptera used to study the physical and neurobiological mechanisms of flight are the Calliphora vicina (blow fly) and Drosophila melanogaster (fruit fly). C. vicina lays its eggs in carrion and is often used in forensics to date the time of death of a body; D. melanogaster is the most well-known for its role in genetics, its entire genome is available online.

Sensory Inputs For Flying

• Compound eyes• Halteres (using campaniform

sensilla)• Neck sense organs• Johnston’s organ

Measuring Fly Flight ResponsesOne version of several apparati for measuring fly wingbeat characteristics during flight. In this version the fly is affixed to a rod inside a cylinder. Inside the cylinder an array of lights is usedto generate vertical stripes of light which are visual cues for the fly to orient itself.An optical wingbeat analyser detects wingbeat amplitude and frequency.

The fly is positioned as if it werehovering and allowed to use thevisual cues to maintain a fixed position relative to it. The entirearena including the cylinder is thenaccelerated by oscillation in bothpitch and roll directions and thewingbeat responses measured.The fly’s head is glued to its thorax to eliminate efferent motor signals from neck mechanoreceptors whichhave previously been shown to have feedback stimulus to visualSystem (Berthoz et al,1992).

(Dickinson, M., 1999, p. 904)

Halteres

• Halters are modified hind wings.

• Oriented at 30o from the wings.• Placed where they will not be

affected by the air turbulence of the wings.

• Numerous (>300) campaniform sensilla at the base.

• The campaniform sensilla sense differing forces on the haltere-thorax articulation as the insect pitches yaws, or rolls.

Most of the haltere mass is in the “club” at the end. One haltere is located slightly more ventrally than the other.During flight, halteres oscillate up and down on a hinged joint in anti-phase (opposite to) with the wing beats.

The motion of the haltereat the joint is detected bya field of 335 mechanoreceptorslocated at the base of the haltere. The receptors are underneath the cuticle anddetect spatial pattern of displacement.

(Hengstenberg, 1998)

During a turn, halteres act as inertial masses moving in a rotating system, much like the mass of air above the Earth following the high to low pressure gradient moving toward the equator above a rotating Earth. This rotation generates a Coriolis effect where the mass accelerates perpendicular to its apparent motion - so warm air moving south toward the equator is accelerated westward. Haltere motion is deflected either left- or right depending on the amplitude and speed of the turn.

The resultant vectors mean the halteres detect angular velocity.

What happens when the fly turns?

• The Coriolis force is detected as strain on the base of the Halteres.

• Phase shifts of the left and right halteres will determine if the body is in a roll, pitch, or yaw.

Strain at the base of the Haltere is detected by Campaniform Sensilla

• The hair is reduced to a simple dome or cupola.

• Detects deflections in the exoskeleton.

• The dome is either circular or elliptical in shape.

• Elliptical shape is directionally sensitive

• Found near joints and articulations, or bases of tactile hairs.

Flying insects have campaniform sensilla on their wings too.These detect the sheer force on the wings, wind resistance, and gravitational acceleration.

Measurements of wing stroke amplitude removing one or both halteres’ end-knobs confirm that they are necessary for maintaining equilibrium flight in pitch, roll and yaw maneuvers.

Halteres also used for wing stroke amplitude control

Note that loss of one haltere knob mostly affects wing on thesame side as it (ipsilateral).

Also note that yaw response is significantly reduced for both wings when one haltere knob is gone.

The haltere afferent neurons are directly connected to the forewing control muscles, thus these experiments show that haltere tuning determines sensitivity and direction of wingbeat response.

(Dickinson, M., 1999, p. 908)

Behaviorial experiments measuring both visual and mechanosensory feedback during flight; wingbeat amplitude response measured for mechanical and visual stimuli changed at same time.

A = mech/visual in opposite phases (180o)B = mech/visual in same phase (0o)C = 90o out of phase (halfway between A & B)

Note that combined response (column iii) is greatest for opposite phase (A) and response for C is midway between A and B, showing that the wingbeat amplitude response is a summation of the input from both visual and haltere inputs.

Haltere input and visual input are additivein wingbeat amplitude control (multimodal integration)

(Sherman & Dickinson, 2003)

Neck Sense Organs

• Detect the head posture.– The head is positioned

using visual input from the eyes.

– If the head is twisted from the body, these hair sensilla will be bent and the body will be adjusted.

Johnston’s Organ

• This sensory organ is located in the pedicle of the antenna (2nd antennal segment).

• Primary function is to sense movement of the flagellum.

• It can be used to detect gravity and flight speed.

• It can also detect courtship air vibrations made by conspecifics.

References

Berthoz, A., Graf, W., Vidal, P.P., eds. (1992) The Head-Neck Sensory Motor System. (New York: Oxford University Press).Chan, WP, Prete, F, Dickinson, MH (1998) “Visual input to the efferent control system of a fly’s ‘gyroscope’.” Science (280) 289-292.Dickinson, MH (1999) “Haltere-Mediated Equilibrium Reflexes of the Fruit Fly, Drosophila Melanogaster.” Philosophical Transactions: Biological Sciences

(354)1385, 903-916.Dickinson, MH (2005) “The Initiation and Control of Rapid Flight Maneuvers in Fruit Flies.” Integrative and Comparative Biology (45) 2, 274-281.Hengstenberg, R. (1998) “Controlling the fly’s gyroscopes.” Nature (392) 757-758.Sherman, A., Dickinson, MH (2002) “A comparison of visual and haltere-mediated equilibrium reflexes in the fruit fly Drosophila melanogaster.” The Journal of

Experimental Biology (206) 295-302.Sherman, A., Dickinson, MH (2003) “Summation of visual and mechanosensory feedback in Drosophila flight control.” The Journal of Experimental Biology

(207) 133-142.Bass, R. B., Strop, P., Barclay, M. and Rees, D. (2002). Crystal structure of Escherichia coli MscS, a voltage-modulated and mechanosensitive

channel. Science 298, 1582-1587. Bezanilla, F. and Perozo, E. (2002). Force and voltage sensors in one structure. Science 298, 1562-1563. Burns, M. D. (1973). The control of walking in Orthoptera. I. Leg movement during normal walking. J. Exp. Biol. 58,45 -58. Burrows, M. (1975). Monosynaptic connections between wing stretch receptors and flight motoneurones in the locust. J. Exp. Biol. 62,189 -219.Burrows, M. (1996). Neurobiology of an Insect Brain. Oxford, New York, Tokyo: Oxford University Press. Burrows, M. and Pflüger, H.-J. (1988). Positive feedback loops from proprioceptors involved in leg movements of the locust. J. Comp. Physiol.

A 163,425 -440. Chang, G., Spencer, R., Lee, A., Barclay, M. and Rees, C. (1998). Structure of the MscL homologue from Mycobacterium tuberculosis, a gated

mechanosensitive ion channel. Science 282, 2220-2226. Hamill, O. P. and McBride, D. W., Jr (1996a). A supramolecular complex underlying touch sensitivity. Trends Neurosci. 19, 258-261. Martinac, B. J Cell Sci 2004;117:2449-2460Martinac, B. (2001). Mechanosensitive channels in prokaryotes. Cell. Physiol. Biochem. 11, 61-76. Paramecium: a model system for the study of excitable cells

Hinrichsen RD, Schultz JE Trends in Neurosciences 11:27-33 (1988)

Perozo, E., Cortes, D. M., Sompornpisut, P., Kloda, A. and Martinac, B. (2002a). Structure of MscL in the open state and the molecular mechanism of gating in mechanosensitive channels. Nature 418, 942-948.

• Rydqvist, B. (1992). Muscle mechanoreceptors in invertebrates. In Advances in Comparative and Environmental Physiology, vol. 10, Comparative Aspects of Mechanoreceptor Systems (ed. F. Ito), pp. 233–260. Berlin: Springer-Verlag.

Cutaneous mechanoreceptors in mammalian skin

• Merkel cells: touch, pressure, slow adaptaton. 10-20 Merkel cells synapse onto one afferent. Respond to sudden displacement of skin as in stroking.

• Ruffini corpuscles: touch, pressure. Slow adaptation. Respond to steady displacement.

• Hair follicle receptors: hair displacement, rapid adaptation

• Meissner corpuscles: touch, vibration, rapid adaptation (velocity detection) (= Krause’s end bulbs in non-primate mammals)

• Paccinian corpuscles: touch, vibration, very fast adaption (acceleration detection)

A diversity of receptor types for a more complete picture of surface texture:

Adaptation rates determine sensitivity to different kinds of stimuli.

Accessory structure provides slip, so Paccinian corpuscle is effectively an acceleration detector

Merkel, Ruffini – report sustained pressure.

Merkel important for form and texture determination. High density of Merkel at fingertips (50/mm2… but dropping to 10/mm2 by age 50!)

Meissner, Paccinian – report change in pressure.

Paccinian corp. can respond up to 1000Hz, but best response is between 200 and 400 Hz. Extraordinary sensitivity of 10 nm to 200 Hz vibration!!!!

Meissner corp. a slower vibration detector: 10 – 200 Hz. Meissner responsible for sensation of objects moving across the skin, and adjustment of grip force if an object starts to slip across skin.

Superficial Deep

Uneven distribution of cutaneous mechanoreceptors on hand surface.

The combination of receptor types leads to some remarkable abilities….

High spatial and temporal resolution allow some people to read Braille at 100 characters per minute!