W. N. McFarland

Bio: W. N. McFarland is an academic researcher. The author has contributed to research in topics: Stimulus modality & Receptor recycling. The author has an hindex of 1, co-authored 1 publications receiving 654 citations.

Sensory biology of aquatic animals

Abstract: This volume constitutes a series of invited chapters based on presentations given at an International Conference on the Sensory Biology of Aquatic Animals held June 24-28, 1985 at the Mote Marine Laboratory in Sarasota, Florida. The immediate purpose of the conference was to spark an exchange of ideas, concepts, and techniques among investigators concerned with the different sensory modalities employed by a wide variety of animal species in extracting information from the aquatic environment. By necessity, most investigators of sensory biology are specialists in one sensory system: different stimulus modalities require different methods of stimulus control and, generally, different animal models. Yet, it is clear that all sensory systems have principles in common, such as stimulus filtering by peripheral structures, tuning of receptor cells, signal-to-noise ratios, adaption and disadaptation, and effective dynamic range. Other features, such as hormonal and efferent neural control, circadian reorganization, and receptor recycling are known in some and not in other senses. The conference afforded an increased awareness of new discoveries in other sensory systems that has effectively inspired a fresh look by the various participants at their own area of specialization to see whether or not similar principles apply. This inspiration was found not only in theoretical issues, but equally in techniques and methods of approach. The myopy of sensory specialization was broken in one unexpected way by showing limitations of individual sense organs and their integration within each organism. For instance, studying vision, one generally chooses a visual animal as a model.

A review of fish swimming mechanics and behaviour in altered flows

Abstract: Fishes suspended in water are subject to the complex nature of three-dimensional flows. Often, these flows are the result of abiotic and biotic sources that alter otherwise uniform flows, which then have the potential to perturb the swimming motions of fishes. The goal of this review is to highlight key studies that have contributed to a mechanistic and behavioural understanding of how perturbing flows affect fish. Most of our understanding of fish behaviour in turbulence comes from observations of natural conditions in the field and laboratory studies employing controlled perturbations, such as vortices generated in the wake behind simple geometric objects. Laboratory studies have employed motion analysis, flow visualization, electromyography, respirometry and sensory deprecation techniques to evaluate the mechanisms and physiological costs of swimming in altered flows. Studies show that flows which display chaotic and wide fluctuations in velocity can repel fishes, while flows that have a component of predictability can attract fishes. The ability to maintain stability in three-dimensional flows, either actively with powered movements or passively using the posture and intrinsic compliance of the body and fins, plays a large role in whether fish seek out or avoid turbulence. Fish in schools or current-swept habitats can benefit from altered flows using two distinct though not mutually exclusive mechanisms: flow refuging (exploiting regions of reduced flow relative to the earth frame of reference) and vortex capture (harnessing the energy of environmental vortices). Integrating how the physical environment affects organismal biomechanics with the more complex issue of behavioural choice requires consideration beyond simple body motions or metabolic costs. A fundamental link between these two ways of thinking about animal behaviour is how organisms sense and process information from the environment, which determines when locomotor behaviour is initiated and modulated. New data are presented here which show that behaviour changes in altered flows when either the lateral line or vision is blocked, showing that fish rely on multi-modal sensory inputs to negotiate complex flow environments. Integrating biomechanics and sensory biology to understand how fish swim in turbulent flow at the organismal level is necessary to better address population-level questions in the fields of fisheries management and ecology.

The physics and neurobiology of magnetoreception

Abstract: Diverse animals can detect magnetic fields but little is known about how they do so. Three main hypotheses of magnetic field perception have been proposed. Electrosensitive marine fish might detect the Earth's field through electromagnetic induction, but direct evidence that induction underlies magnetoreception in such fish has not been obtained. Studies in other animals have provided evidence that is consistent with two other mechanisms: biogenic magnetite and chemical reactions that are modulated by weak magnetic fields. Despite recent advances, however, magnetoreceptors have not been identified with certainty in any animal, and the mode of transduction for the magnetic sense remains unknown.

Sound Detection and Processing by Fish: Critical Review and Major Research Questions (Part 1 of 2)

Abstract: The literature on fish hearing has increased significantly since our last critical review in 1973. The purpose of the current paper is to review the more recent literature and to identify those questions that need to be asked to develop a fuller understanding of the auditory capabilities and processing mechanisms of fishes. We conclude that while our understanding of fish hearing has increased substantially in the past years, there are still major gaps in what we know. In particular, the comparative functional literature is extremely limited, and we do not yet know whether different species, and particularly hearing specialists as compared to hearing nonspecialists, have fundamentally different auditory capabilities and mechanisms.

Fish Brains: Evolution and Anvironmental Relationships

Abstract: Fish brains and sensory organs may vary greatly between species. With an estimated total of 25 000 species, fish represent the largest radiation of vertebrates. From the agnathans to the teleosts, they span an enormous taxonomic range and occupy virtually all aquatic habitats. This diversity offers ample opportunity to relate ecology with brains and sensory systems. In a broadly comparative approach emphasizing teleosts, we surveyed ‘classical’ and more recent contributions on fish brains in search of evolutionary and ecological conditions of central nervous system diversification. By qualitatively and quantitatively comparing closely related species from different habitats, particularly cyprinids and African cichlids, we scanned for patterns of divergence. We examined convergence by comparing distantly related species from similar habitats, intertidal and deep-sea. In particular, we asked how habitats relate to the relative importance of different sensory faculties. Most fishes are predominantly visually orientated. In addition, lateral line and hearing are highly developed in epi- and mesopelagic species as well as in the Antarctic notothenoids. In bathypelagics, brain size and the lobes for vision and taste are greatly reduced. Towards shallow water and deep-sea benthic habitats, chemosenses increase in importance and vision may be reduced, particularly in turbid environments. Shallow tropical marine and freshwater reefs (African lakes) enhance visual predominance and appear to exert a considerable selection pressure towards increased size of the (non-olfactory)telencephalon. The development of cognitive skills (spatial learning, problem solving) in fish seems to be associated with visual orientation and well-structured habitats.

Sound as an Orientation Cue for the Pelagic Larvae of Reef Fishes and Decapod Crustaceans

Abstract: The pelagic life history phase of reef fishes and decapod crustaceans is complex, and the evolutionary drivers and ecological consequences of this life history strategy remain largely speculative. There is no doubt, however, that this life history phase is very significant in the demographics of reef populations. Here, we initially discuss the ecology and evolution of the pelagic life histories as a context to our review of the role of acoustics in the latter part of the pelagic phase as the larvae transit back onto a reef. Evidence is reviewed showing that larvae are actively involved in this transition. They are capable swimmers and can locate reefs from hundreds of metres if not kilometres away. Evidence also shows that sound is available as an orientation cue, and that fishes and crustaceans hear sound and orient to sound in a manner that is consistent with their use of sound to guide settlement onto reefs. Comparing particle motion sound strengths in the field (8 × 10−11 m at 5 km from a reef) with the measured behavioural and electrophysiological threshold of fishes of (3 × 10−11 m and 10 × 10−11, respectively) provides evidence that sound may be a useful orientation cue at a range of kilometres rather than hundreds of metres. These threshold levels are for adult fishes and we conclude that better data are needed for larval fishes and crustaceans at the time of settlement. Measurements of field strengths in the region of reefs and threshold levels are suitable for showing that sound could be used; however, field experiments are the only effective tool to demonstrate the actual use of underwater sound for orientation purposes. A diverse series of field experiments including light‐trap catches enhanced by replayed reef sound, in situ observations of behaviour and sound‐enhanced settlement rate on patch reefs collectively provide a compelling case that sound is used as an orientation and settlement cue for these late larval stages.