Burst‐Swimming Performance of Larval Zebra Danios and the Effects of Diel Temperature Fluctuations

Zebra danios Danio [Brachydanio] rerio were spawned and their eggs and larvae were reared in a simulated natural thermal regime, increasing from 21 to 30°C for 7 h and decreasing to 21°C for 17 h, daily. Burst‐swimming performance was provoked by electrical stimulation of larvae (mean total length = 3.6 mm). Responses were filmed at 400 frames/s at temperature intervals of 3°C. Distance travelled in a specified time (St), maximum velocity, and maximum acceleration increased with temperature. Size‐specific maximum velocity was considerably higher than previously reported for larvae. A predictive model relating St to temperature was developed. In theory, the observed effects of temperature could have been due to changes in physiological rates or in water viscosity, but Reynolds numbers were too high for a substantial viscosity effect. The Q10 for St was 1.6, that for maximum velocity was 1.4. Results suggest that, other factors being equal, larvae are potentially more vulnerable to predation at sunrise or at other times when water temperature is low.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141859/1/tafs0143.pd

Ontogeny of visual and mechanosensory structure and function in atlantic menhaden Brevoortia tyrannus

The importance of visual, mechanoreceptive and auditory inputs to escape responses was examined in larvae of the Atlantic menhaden (Brevoortia tyrannus) presented with a simulated predatory stimulus. Ontogenetic changes in the retina, superficial neuromasts and auditory bullae were examined in concert with behavioral trials in which sensory inputs were selectively blocked. Menhaden larvae showed a decrease in cone photoreceptor density and first developed rod photoreceptors when their total length (TL) reached 8-10 mm; they began summing photoreceptive inputs at 12-14 mm TL. Inflation of the auditory bullae was complete by 15 mm TL. The proliferation of superficial neuromasts varied depending on their location, with cephalic superficial neuromasts decreasing in number beginning at 19 mm TL and numbers of trunk neuromasts continuing to increase throughout the larval period. In behavioral trials, responsiveness and the reactive distance to the approaching probe increased with increasing larva total length when all sensory inputs were available (control larvae). When visual inputs were blocked, responsiveness was lower than in control larvae, but still increased ontogenetically, while reactive distance showed no difference between control larvae and those lacking visual information. When neuromasts were ablated, ontogenetic increases in responsiveness and reactive distance were absent. Inflation of the auditory bullae had no discernible effect on behavior. The anatomical and behavioral results suggest that both vision and mechanoreception are used to trigger a response to a looming predatory stimulus and that mechanoreception, but not vision, contributes to the timing of the response. Ontogenetic improvements in performance are attributed mainly to neuromast proliferation and not to ontogenetic changes in the retina

Ontogenetic change in predicted acoustic pressure sensitivity in larval red drum (Sciaenops ocellatus)

Author Posting. © Company of Biologists, 2019. This article is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 222(16), (2019): jeb.201962, doi:10.1242/jeb.201962.Detecting acoustic pressure can improve a fish's survival and fitness through increased sensitivity to environmental sounds. Pressure detection results from interactions between the swim bladder and otoliths. In larval fishes, those interactions change rapidly as growth and development alter bladder dimensions and otolith–bladder distance. We used computed tomography imagery of lab-reared larval red drum (Sciaenops ocellatus) in a finite-element model to assess ontogenetic changes in acoustic pressure sensitivity in response to a plane wave at frequencies within the frequency range of hearing by fishes. We compared the acceleration at points on the sagitta, asteriscus and lapillus when the bladder was air filled with results from models using a water-filled bladder. For larvae of 8.5–18 mm in standard length, the air-filled bladder amplified simulated otolith motion by a factor of 54–3485 times that of a water-filled bladder at 100 Hz. Otolith–bladder distance increased with standard length, which decreased modeled amplification. The concomitant rapid increase in bladder volume partially compensated for the effect of increasing otolith–bladder distance. Calculated resonant frequency of the bladders was between 8750 and 4250 Hz, and resonant frequency decreased with increasing bladder volume. There was a relatively flat frequency dependence of these effects in the audible frequency range, but we found a small increase in amplification with increasing excitation frequency. Using idealized geometry, we found that the larval vertebrae and ribs have negligible influence on bladder motion. Our results help clarify the auditory consequences of ontogenetic changes in bladder morphology and otolith–bladder relationships during larval stages.This work was supported by the American Museum of Natural History Lerner Gray Fund for Marine Research (to A.K.S.), the Perry R. Bass Endowment at the University of Texas Marine Science Institute (to L.A.F.), and the Office of Naval Research Ocean Acoustics Program (grant number N00014-15-1-2032 to P.S.W.).2020-08-0

FishSizer: Software solution for efficiently measuring larval fish size

Length and depth of fish larvae are part of the fundamental measurements in many marine ecology studies involving early fish life history. Until now, obtaining these measurements has required intensive manual labor and the risk of inter- and intra-observer variability. We developed an open-source software solution to semi-automate the measurement process and thereby reduce both time consumption and technical variability. Using contrast-based edge detection, the software segments images of a fish larva into “larva” and “background.” Length and depth are extracted from the “larva” segmentation while taking curvature of the larva into consideration. The graphical user interface optimizes workflow and ease of usage, thereby reducing time consumption for both training and analysis. The software allows for visual verification of all measurements. A comparison of measurement methods on a set of larva images showed that this software reduces measurement time by 66%–78% relative to commonly used software. Using this software instead of the commonly used manual approach has the potential to save researchers from many hours of monotonous work. No adjustment was necessary for 89% of the images regarding length (70% for depth). Hence, the only workload on most images was the visual inspection. As the visual inspection and manual dimension extraction works in the same way as currently used software, we expect no loss in accuracy.publishedVersio

Larval development and allometric growth of the black-faced blenny Tripterygion delaisi

Larval development and allometric growth patterns of the black-faced blenny Tripterygion delaisi are described from a larval series (body length, L-B = 3.30-12.10 mm) caught by light traps at the Arrabida Marine Park, Portugal. Larvae of T. delaisi possess distinctive morphometric and meristic characteristics which can be used to identify this species from related taxa. Pigmentation is sparse but characteristic, consisting of pigmented eyes, gas bladder pigmentation in the dorsal region, anal pigmentation and a row of regularly spaced postanal ventral melanophores. This pattern is present from as early as the yolk-sac stage and persists throughout all stages with just the addition of head and caudal pigmentation during the flexion and postflexion stages, respectively. The majority of fin development (with the exception of the caudal fin), occurs in the later stages of development. Myomere counts range between 37 and 45 for all stages. Growth is allometric during larval development. When inflexion points of growth were detected, growth was found to be biphasic with the inflexion points occurring within a very narrow range of L-B (8.70-8.90 mm) close to the mean +/- S.D. (9.44 +/- 1.48 mm LB) of postflexion larvae. Considering allometric growth patterns and ontogenetic descriptions together, the first developmental phase includes the preflexion and flexion stage larvae, while the second phase characterises the postflexion larvae prior to the transition from larvae to juvenile. (C) 2017 The Fisheries Society of the British IslesMARES; Erasmus Mundus [FPA 2011-0016]; Fundacao para a Ciencia e Tecnologia (FCT) [POCTI/MAR/57934/2004, PTDC/MAR/115226/2009, PTDC/MAR-EST/4356/2012, 331/94, PEST-OE/MAR/UI0331/2011, UID/MAR/04292/2013, Multi/04326/2013]info:eu-repo/semantics/publishedVersio

State of the Art of Identification for Cyprinid Fish Larvae from Eastern North America

Morphological characteristics are known for 62 species of cyprinid larvae in 22 genera occupying waters of North America east of the Continental Divide. Currently known diagnostic characters are presented for most of these species. Species are arranged into groups according to their relative preanal length, eye shape, preanal myomere number, and ventral pigmentation. Descriptive literature is noted, as are errors in the literature. Practical considerations for making identifications, species in need of description, and characters to be investigated are discussed.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142047/1/tafs0319.pd

PERFORMANCE OF FISH LARVAE: EFFECTS OF ATRAZINE,

To my husband, Rafael Perez, to whom I owe everything, who has been with me through the “good and the bad”. To my son, Diego T. Perez, and my daughter, Cecilia A. Perez, who have always brightened my day with laughter and love. And to my parents, Alvaro Alvarez and Marie Cecilie d’Otreppe de Bouvette, who, without ever a doubt, have supported me on every decision I have made. Thank you. Acknowledgements I wish to thank my adviser Dr. Lee A. Fuiman, for his guidance, support, and encouragement. I am also grateful to the members of my committee, Dr. David P. Crews, Dr. G. Joan Holt, Dr. B. Scott Nunez and Dr. Peter Thomas for their helpful suggestions and critical review of this dissertation. Thanks to my laboratory mates; Hunter Samberson and Brie Sarkisian for their help with fish rearing; Ian McCarthy for helping with fish rearing and collection of data, and Kiersten Madden for her support and critique of this work. My special thanks to Rafael Perez, Scott Applebaum, and Ian McCarthy for discussion in the development of the research presented here. I am sincerely thankful to all my friends at the Marine Science Institute and Port Aransas for their help and support, without whom this dissertation would not have happened. v SIGNIFICANCE OF ENVIRONMENTALLY REALISTI

Escape path complexity and its context dependency in Pacific blue-eyes (Pseudomugil signifer)

The escape paths prey animals take following a predatory attack appear to be highly unpredictable - a property that has been described as ‘protean behaviour’. Here we present a method of quantifying the escape paths of individual animals using a path complexity approach. When individual fish (Pseudomugil signifer) were attacked, we found that a fish's movement path rapidly increased in complexity following the attack. This path complexity remained elevated (indicating a more unpredictable path) for a sustained period (at least 10 seconds) after the attack. The complexity of the path was context dependent; paths were more complex when attacks were made closer to the fish, suggesting that these responses are tailored to the perceived level of threat. We separated out the components of speed and turning rate changes to determine which of these components contributed to the overall increase in path complexity following an attack. We found that both speed and turning rate measures contributed similarly to an individual's path complexity in absolute terms. Overall, our work highlights the context dependent escape responses that animals use to avoid predators and also provides a method for quantifying the escape paths of animals

Exercise at Depth Alters Bradycardia and Incidence of Cardiac Anomalies in Deep-Diving Marine Mammals

Unlike their terrestrial ancestors, marine mammals routinely confront extreme physiological and physical challenges while breath-holding and pursuing prey at depth. To determine how cetaceans and pinnipeds accomplish deep-sea chases, we deployed animal-borne instruments that recorded high-resolution electrocardiograms, behaviour and flipper accelerations of bottlenose dolphins (Tursiops truncatus) and Weddell seals (Leptonychotes weddellii) diving from the surface to 4200 m. Here we report that both exercise and depth alter the bradycardia associated with the dive response, with the greatest impacts at depths inducing lung collapse. Unexpectedly, cardiac arrhythmias occurred in 473% of deep, aerobic dives, which we attribute to the interplay between sympathetic and parasympathetic drivers for exercise and diving, respectively. Such marked cardiac variability alters the common view of a stereotypic ‘dive reflex’ in diving mammals. It also suggests the persistence of ancestral terrestrial traits in cardiac function that may help explain the unique sensitivity of some deep-diving marine mammals to anthropogenic disturbances