We study the structural and functional development and evolution of fish sensory systems. Our work is focused on the mechanosensory lateral line system, a primitive vertebrate sensory system found in all 30,000+ fishes (and larval and aquatic adult amphibians) – and thus in more than half of all vertebrate species on earth. The lateral line system detects water flows facilitating prey detection, predator avoidance, communication, and navigation (including rheotaxis). Furthermore, in contrast to the eyes, ears and noses, the system is composed of many small sense organs (neuromasts) distributed on the head and body. They are found on the skin and in hollow, pored canals within a consistent subset of skull bones, and in a canal contained in a row of lateral line scales on the body.
Thus, the lateral line system has a dual identity, as an essential sensory system that mediates critical behaviors and as a component of the skull of bony fishes. As such, the study of the system contributes to our understanding of sensory biology, evolutionary developmental biology, and development and evolution of the vertebrate skull. Furthermore, the study of the lateral line system and its role in behavior will shed light on how fishes may overcome challenges presented global change such as reduced water clarity, which would require increased dependence on non-visual sensory systems for critical behaviors such as prey detection, predator avoidance, and communication.
We have studied the lateral line system in a wide range of taxa including: flounders, greenlings, zebrafish, skates, coral reef butterflyfishes and gobies, Lake Malawi cichlids, and deep-sea (stomiiform) fishes. Each group has interesting or unique attributes that have allowed us to ask fundamental questions about patterns of lateral line evolution, developmental patterns (with an eye towards mechanisms), functional morphology, and the sensory basis forbehavior.
We use multiple methods including histology, SEM, CT/µCT, vital fluorescent imaging, and fate mapping to gain a comprehensive understanding of patterns of lateral line morphology and development. We have also used DPIV (for analysis of hydrodynamic stimuli), video analysis of behavior, and classical fish training (conditioned responses to artificial hydrodynamic stimuli) to study the sensory basis for feeding behavior under different environmental conditions.
Our work has been funded by the National Science Foundation, a NSF Graduate Research Fellowship, the Lerner Gray Fund of the American Museum of Natural History, the Marine Biological Laboratory (Woods Hole), RI NSF EPSCoR, and the University of Rhode Island.
Sensory Biology of Coral Reef Fishes
- The Role of Larval Orientation Behavior in Determining Population Connectivity – Sensory Ontogeny in a Coral Reef Goby. Late stage larvae of coral reef fishes are known to respond to olfactory, auditory, and visual cues to navigate to their settlement sites on reefs, but the morphology and development of their sensory systems are not well studied. In this collaborative project with colleagues at Boston University and University of Miami, we are using a goby (Elactinus lori) for the first integrated study of the ontogeny of multiple sensory systems and larval orientation behavior in a coral reef fish. The ultimate goal is to understand how the different sensory systems and navigation behavior contribute to settlement patterns, and thus population connectivity. Funded by NSF grant 1459546 (Ocean Sciences). See: Goby Sensory Ontogeny page.
- The Laterophysic Connection in Butterflyfishes – We described the comparative anatomy, development, and systematic significance of the laterophysic connection, a unique swim bladder-lateral line linkage in butterflyfishes in the genus Chaetodon. Tricas and Webb (2016) reviews all of this work and the behavioral and physiological work on sound production and sound reception carried out by the Tricas lab. Funded by NSF grants IBN 9603896 and IBN 0132607. See: Butterflyfish Project page.
Flow Sensing in the Deep Sea: The Lateral Line System of Stomiiform Fishes
The deep sea is a hydrodynamically quiet environment characterized by low light levels or complete darkness, which would seem to favor the evolution of the non-visual senses. Several groups of mid-water fishes are known to have specializations of the lateral line system, but little is known about the deep sea fishes in the species and ubiquitous Order Stomiiformes. The morphology of the lateral line system in stomatiiform fishes is being investigated for the first time using a range of morphological methods including histology, SEM, and µCT imaging. Funded by an NSF Graduate Research Fellowship, Lerner-Gray Fund for Marine Research Grant (ANMH, NY), and URI. (A. Marranzino, ongoing MS Thesis). See: Deep-Sea Lateral Line page.
Development and Evolution of the Mechanosensory Lateral Line System
- Phenotypic Evolution in the Lateral Line System of Cichlid Fishes. Representatives of two genera of Lake Malawi (Africa) cichlid fishes (Aulonocara [widened canals] and Tramitichromis [narrow canals]) are being used for comparative anatomical, developmental, and behavioral studies that address fundamental issues in post-embryonic lateral line development, diversification of lateral line phenotypes, and functional evolution of the lateral line system of fishes. Funded by NSF grant IOS 0843307. See: Cichlid Project page.
- Dermal Bone Remodeling and Lateral Line Canal Morphogenesis – We are interested in understanding how developmental processes contribute to patterns of lateral line canal morphogenesis, growth, and evolution of the cranial lateral line canals in bony fishes. We seek to determine: a) how lateral line canals become integrated into the dermatocranial bones in bony fishes, and b) how patterns of bone remodeling defines lateral line canal phenotypes (Johnstone, ongoing MS thesis). Funded by URI.
Lateral Line Development in Elasmobranch Fishes
We have studied the development of the lateral line canal system in the little skate, Leucoraja erinacea. In contrast to the bony fishes, the cranial lateral line canals in elasmobranch fishes are not associated with elements of the skull, but are contained in soft tissue in the dermis. In addition, the pattern of development of the lateral line system in elasmobranchs contrasts with that in bony fishes in fundamental ways. The study of this contrast will shed light on how lateral line development evolved with the divergence of the cartilaginous (elasmobranch) and bony fishes hundreds of millions of years ago. This work has been carried out at the Marine Biological Laboratory (Woods Hole) in collaboration with Dr. Andrew Gillis (Cambridge University, UK). Funded by a Laura and Arthur Colwin Endowed Summer Research Fellowship at the MBL and the University of Rhode Island. See: Skate Project page.
µCT Imaging of the Cranial Lateral Line Canal System – We are continuing to develop methods for visualizing and quantifying the morphology of the cranial lateral line canals of teleost fishes in both 2D and 3D. See: µCT Imaging Page.
Photo credit: Dr. Margot Schwalbe