Date of Award
2025
Degree Type
Thesis
Degree Name
Master of Science in Biological and Environmental Sciences (MSBES)
Department
Biological Sciences
First Advisor
Jacqueline F. Webb
Abstract
The mechanosensory lateral line system of fishes senses water flows and is comprised of two types of flow sensors (neuromast organs). Neuromasts found within in bony canals on the head or in tubed scales on the trunk (canal neuromasts, CNs) have been the subject of intensive study, but far less is known about those neuromasts that occur on the skin (superficial neuromasts, SNs). The number and distribution of SNs was described in 30 species of tetras (small fishes in the Neotropical freshwater families Acestrorhamphidae and Characidae [Order: Characiformes]) and three characiform outgroups using vital fluorescent staining and scanning electron microscopy. Fifteen morphological characters describing SN abundance and arrangements on the head, trunk, and caudal fin (tail) were defined. Fluorescent staining revealed variation in the number and distribution of SNs, and SEM revealed the size, shape, and directional sensitivity (hair cell orientation) of individual neuromasts. The range in the total number of SNs (head, trunk, and tail) was 288 (in Aphyocharax rathbuni) to 5506 (in Gymnocorymbus ternetzi), which represents one of the highest numbers of SNs known among teleost fishes. On the head, SNs were found in simple, indistinct, or diffuse lines (= three character states) and in several clusters. On the trunk, vertical lines of SNs were found on all scales of the body, however they were rare on the tubed lateral line scales. On the caudal fin, dozens to hundreds of SNs were present in between 4 and 18 lines that are found between the fin rays of the caudal fin. Variation in number and arrangement of SNs on the head, trunk and caudal fin was identified among species, genera, subfamilies and families; however, an examination of the presence/absence/state of characters among taxa did not reveal distinct phylogenetic trends. These attractive, often colorful, diminutive fishes are popular in the aquarium (pet) trade, but little is known about their sensory ecology. The behavioral and ecological significance of superficial neuromast proliferations with variation among taxa remains subject to speculation. Nevertheless, the discovery of superficial neuromast proliferations in tetras and their relatives draws attention to the potential importance of flow sensing in the lives of these fishes.
Recommended Citation
Hampton, Maxwell, "SUPERFICIAL NEUROMASTS IN THE MECHANOSENSORY LATERAL LINE SYSTEM IN NEOTROPICAL FRESHWATER FISHES OF THE FAMILIES ACESTRORHAMPHIDAE AND CHARACIDAE (ORDER: CHARACIFORMES)" (2025). Open Access Master's Theses. Paper 2637.
https://digitalcommons.uri.edu/theses/2637