120 research outputs found
The functional ecology of fish predation on coral reefs
No full textMichalis Mihalitsis studied fish predation on coral reefs. Fish predators feed in fundamentally different ways. The main predators on reefs are completely different from the ones previously considered, suggesting the need for a paradigm shift in this field. His results have significant implications for how we understand reef function
The role of fishes as food: A functional perspective on predator–prey interactions
No full textEvery animal dies. In nature, mortality usually occurs due to predation by other animals. One of the fundamental consequences of mortality is the transfer of energy and nutrients from one organism (prey) to another (predator). On coral reefs, these key interactions and processes, that are essential for ecosystem functioning, are primarily mediated by fishes; up to 53% of fishes on coral reefs can be regarded as piscivorous. To date, piscivory on coral reefs has been primarily studied with regard to the species piscivores feed on, and how piscivores control populations. Consequently, understanding prey selectivity by piscivorous fishes has been a major goal. However, prey functional traits may also be important in understanding these ‘energy transactions’, especially in complex ecosystems such as coral reefs. Our goal, therefore, was to quantify—at a community level—functional traits of prey that have been shown to influence predator–prey interactions. We found that, on average, deep-bodied, social fishes occupy higher positions in the water column, whereas solitary species are usually elongate and more closely associated with the benthos. On closer examination, we found that solitary species have a size-dependent relationship, with substratum associations shifting to water column associations, at approximately 50 mm body length. Our results reveal three distinct prey functional groups: cryptobenthic substratum dwellers, solitary epibenthics and social fishes. These groups display significant differences in their morphologies and behaviours. Furthermore, based on a meta-analysis of published mortality rates of small-bodied (<100 mm TL) reef fishes, we show that the three groups display different mortality rates, possibly due to differential exposure to, and potential to be captured by, different predator types. Although fishes are widely available on coral reefs, they may not be equally available as prey to all piscivore types. Prey are not simply victims; they are capable of influencing potential predation through functional traits. A free Plain Language Summary can be found within the Supporting Information of this article
A functional evaluation of feeding in the surgeonfish Ctenochaetus striatus: the role of soft tissues
No full textCtenochaetus striatus is one of the most abundant surgeonfishes on Indo-Pacific coral reefs, yet the functional role and feeding ecology of this species remain unclear. This species is reported to possess a rigid structure in its palate that is used for scraping, but some authors have reported that this element is comprised of soft tissue. To resolve the nature and role of this structure in the feeding ecology of C. striatus we examined evidence from anatomical observations, scanning electron microscopy, histology, X-ray micro-computed tomography scanning, highspeed video and field observations. We found that C. striatus from the Great Barrier Reef possess a retention plate (RP) on their palates immediately posterior to the premaxillary teeth which is soft, covered in a thin veneer of keratin with a papillate surface. This RP appears to be used during feeding, but does not appear to be responsible for the removal of material, which is achieved primarily by a fast closure of the lower jaw. We infer that the RP acts primarily as a 'dustpan', in a 'dustpan and brush' feeding mechanism, to facilitate the collection of particulate material from algal turfs
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No full text(a) Current and (b) suggested models of body size vs. mortality relationships. While the overall mortality remains the same between the current and suggested model (area below curves), the shape of the suggested distribution (i.e., flattening the curve), results in different survivorship curves (c, d). These differences in survivorship curves may allow for a higher number of reproducing individuals and provide a potential explanation for limited individual gamete output, resulting in high overall contribution to the larval pool near coral reefs (Brandl and colleagues [20]). Fish silhouettes redrawn from (Mihalitsis and colleagues [36]). (DOCX)</p
Raw data for manuscript: Feeding kinematics of a surgeonfish reveal novel functions and relationships to reef substrata
No full textFeeding kinematics of a surgeonfish reveal novel functions and relationships to reef substratahttps://doi.org/10.5061/dryad.6t1g1jx59Datasets contain raw x and y coordinates of all bites analysed, and for each landmark throughout the sequences. Furthermore, the values used to compare kinematics from videos, to our biomechanical model, as well as the equivalent algal lengths (Figure 4) are also found here.Description of the data and file structureEach excel file (except for the ones containing comparative or algal length data) represents a single bite. ID is the unique name of each bite. X and Y are the raw x and y coordinates, whereas x_mm and y_mm are the scaled coordinates relative to the distance of the camera to the algae in each video sequence. Slice is the timesamp in ms that each landmark was placed in, when analysig in ImageJ. Time is the same Slice, except for t=0 is assigned as when the jaws of the fish begin to close. This was done to make all bites temporally comparable to each other.The 'rotations_raw' and 'morphology' files contain the data for Figures 4 and 5. In the 'rotations_raw' file Suction represents the pressence of suction in the bite sequences, Phase 2 shows whether there was a Phase 2 present in each sequence. Duration_total is the total duration of each bite in ms. jaw_open1_time is the duration in ms for the first jaw opening whne the fish approaches the algae to take a bite. Jaw_open2_time is the duration in ms of the second jaw oening, when the fish has detached the algae and re-opens its mouth to ingest the detached algae. Benthos_lj_min is the minimum distance the jaw reaches to the benthos (line defined by landmarks HG). Algae_l_mm is the length of the algae targeted for each sequence. Dist_L_stretch is the amount of motion by landmark L (i.e., cranial rotation) observed in the videos, dist_EI_stretch is the motion between landmarks E and I observed in the videos, and dist_IO_stretch is the motion between landmarks I and O observed in the videos. The next 3 columns are the same as the previous, but what was predicted from our model, when considering the anatomy of each specimen that performed the bites (see file 'morphology').For the 'morphology' file, the ID column is the independent ID of each specimen (see ID name of raw x,y coordinate files as well). SL is the Standard length of each specimen. All other columns represent distances (mm) between landmarks measured on the specimens upon dissections.Code/SoftwareThe 'A_leuc_analysis.R' file contains the code used to make the kinematic profiles (e.g., Figure 1-3).The 'rotations.R' file contains the code used to make the plots and analyses (i.e., statistical models) for Figures 4 and 5.</p
Functional groups in piscivorous fishes
No full textAbstract Piscivory is a key ecological function in aquatic ecosystems, mediating energy flow within trophic networks. However, our understanding of the nature of piscivory is limited; we currently lack an empirical assessment of the dynamics of prey capture and how this differs between piscivores. We therefore conducted aquarium‐based performance experiments, to test the feeding abilities of 19 piscivorous fish species. We quantified their feeding morphology, striking, capturing, and processing behavior. We identify two major functional groups: grabbers and engulfers. Grabbers are characterized by horizontal, long‐distance strikes, capturing their prey tailfirst and subsequently processing their prey using their oral jaw teeth. Engulfers strike from short distances, from high angles above or below their prey, engulfing their prey and swallowing their prey whole. Based on a meta‐analysis of 2,209 published in situ predator–prey relationships in marine and freshwater aquatic environments, we show resource partitioning between grabbers and engulfers. Our results provide a functional classification for piscivorous fishes delineating patterns, which transcend habitats, that may help explain size structures in fish communities
Functional implications of dentition-based morphotypes in piscivorous fishes
No full textTeeth are crucial in elucidating the life history of vertebrates. However, most studies of teeth have focused on mammals. In heterodont mammals, tooth function is based on tooth shape and position along the jaw. However, the vast majority of vertebrates are homodont, and tooth function might not be based on the same principles (in homodonts, tooth shape is broadly similar along the jaw). We provide a quantitative framework and establish dentition-based morphotypes for piscivorous fishes. We then assess how these morphotypes relate to key functional feeding traits. We identified three broad morphotypes: edentulate, villiform and macrodont, with edentulate and villiform species displaying considerable functional overlap; macrodont species are more distinct. When analysing macrodonts exclusively, we found a major axis of variation between 'front-fanged' and 'back-fanged' species. The functional interpretations of this axis suggest that tooth-based functional decoupling could exist, even in homodont vertebrates, where teeth have similar shapes. This diversity is based not only on tooth shape but also solely on the position along the jaw
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Feeding kinematics of a surgeonfish reveal novel functions and relationships to reef substrata.
No full textBiting to obtain attached benthic prey characterizes a large number of fish species on coral reefs, and is a feeding mode that contributes to important ecosystem functions. We use high-speed video to reveal the mechanisms used by a surgeonfish, Acanthurus leucosternon, to detach algae. After gripping algae in its jaws, the species pulls it by ventrally rotating both the head and the closed jaws, in a novel use of the intra-mandibular joint. These motions remain in the plane of the fish, reducing the use of a lateral head flick to detach the algae. The novel ability to bite and pull algae off the substrate without bending the body laterally minimizes exposure to high water flows, and may be an adaptation to feeding in challenging reef habitats such as the crest and flat. Therefore, our results could potentially represent a key milestone in the evolutionary history of coral reef trophodynamics
Feeding kinematics of a surgeonfish reveal novel functions and relationships to reef substrata.
No full textAuthor Correction: RNAs coordinate nuclear envelope assembly and DNA replication through ELYS recruitment to chromatin
No full textIn the original version of this Article, the affiliation details for Antoine Aze, Michalis Fragkos, Stéphane Bocquet, Julien Cau and Marcel Méchali incorrectly omitted ‘CNRS and the University of Montpellier’. This has now been corrected in both the PDF and HTML versions of the Article.</jats:p
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