Antennule flicking

Early evidence for this idea was provided by Schmitt and Ache (1979), who found that the response to changes in odor concentration by olfactory receptor neurons in lobster antennules was enhanced if the antennule flicked. The idea that this enhanced response was due to improved water flow into the aesthetasc array was supported by Moore et al. (1991), who found that when they squirted water onto lobster antennules (to mimic flicking), the penetration into the aesthetasc array of tracer molecules carried in the water was increased. How does water flow through an aesthetasc array during a flick, and how does it depend on antennule morphology and motion ... 

Because these diverse crustaceans flick their antennules in the Re range at which the leakiness of their hair arrays is sensitive to speed, they are able to take fluid samples into their aesthetasc arrays during the rapid down stroke of a flick when the aesthetasc array is leaky. They then retain that captured water within the hair array during the slower return stroke and subsequent stationary pause of the antennule when the aesthetasc array is not leaky. During the next rapid flick down stroke, that water sample is flushed away and replaced by a new one. Therefore, antennule flicking permits these animals to take discrete samples in space and time of their odor environment. In other words, a flick is a sniff (reviewed in Koehl 2006). 

When the lateral filament of an antennule flicks, it samples a small slice of the water in a crustacean s environment. What are the patterns of odor concentrations in the water samples captured by flicking antennules as the animals move through habitats exposed to ambient water motion ... 

Goldman JA, Koehl MAR (2001) Fluid dynamic design of lobster olfactory organs High-speed kinematic analysis of antennule flicking by Panulirus argus. Chem Senses 26 385-398... 

Fig. 11.5 Antennule flicking. Antennule velocity during outward lateral flick (black diamonds) and medial return stroke (grey circles) increases with body size. Data are means standard errors. The outward stroke of the flick is faster than the return stroke of the flick...

Olfactory flicking seems to be matched to the animal s olfactory need. For instance, the tropical mantis shrimp G. falcatus becomes increasingly involved in sophisticated aggressive and reproductive encounters as it grows. It also hunts faster and more elusive prey. These complex social and foraging behavior patterns require rapid responses. Perhaps to accommodate the need for speed, antennule flicking velocity and frequency increase several fold with body size (Fig. 11.5a, Mead et al. 1999). Flicking reduces the boundary layer so that odors penetrate the array more quickly (Mead and Koehl 2000), and increases the rate at which chemical information is obtained. 

Fig. 5.2 Diagram of the spiny lobster, Panulirus argus, flicking the aesthetasc-bearing lateral filaments of its olfactory antennules. Drawing by Jorge A. Varela Ramos...

A number of researchers have suggested that when malacostracan crustaceans flick the lateral filaments of their antennules, they increase the penetration of ambient water into the spaces between aesthetascs, and thus bring odor-carrying water closer to the receptor cells in those chemosensory hairs (Snow 1973 Schmitt and Ache 1979 Atema 1985 Gleeson et al. 1993 Koehl 1995, 1996). 

Patterns of Odor Concentrations Captured by Flicking Antennules... 

The ways in which crustaceans deploy their antennules in ambient currents can affect water flow through the aesthetasc arrays. In our flume experiments with lobsters (Koehl et al. 2001), an ambient water current of 10 cm/s did not force water and odor filaments into the aesthetasc arrays on antennules held parallel to the flow direction, whereas water and odor samples did move into the arrays during flick down strokes of 6 cm/s (during a down stroke where the water flow relative to the antennule is perpendicular to the long axis of the antennule). This suggests that if... 

Mead KS, Koehl MAR (2000) Stomatopod antennule design The asymmetry, sampling efficiency, and ontogeny of olfactory flicking. J Exp Biol 203 3795-3808... 

Reidenbach MA, George NT, Koehl MAR (2008) Antennule morphology and flicking kinematics facilitate odor sampling by the spiny lobster, Panulirus argus. J Exp Biol 211 2849-2858 Sainte-Marie B (1986) Feeding and swimming of lysianassid amphipods in a shallow cold-water... 

Although there are no published studies focusing solely on the biomechanics of antennulation, work has been done on olfactory flicking in stomatopods (Mead et al. 

These data inserted into an advection-diffusion model indicate that odor molecules in filaments moving into the sensor array arrive at the surfaces of the aesthetascs within milliseconds (Stacey et al. 2003). In contrast, during the slower return stroke of the flick and during the stationary pause between flicks, water flows around rather than into the array of chemosensory hairs (Mead et al. 1999 Mead and Koehl 2000). Thus, an antennule of a mantis shrimp takes a discrete sample in time and space of its odor environment only during the flick outstroke (Mead and Koehl 2000 Stacey et al. 2003). This pattern of discrete sampling appears to be widespread among crustaceans (see Koehl, Chap. 5). 

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