Electrosensory-driven feeding behaviours of the Port Jackson shark (Heterodontus portusjacksoni) and western shovelnose ray (Aptychotrema vincentiana)

2016 ◽  
Vol 67 (2) ◽  
pp. 187 ◽  
Author(s):  
R. M. Kempster ◽  
C. A. Egeberg ◽  
N. S. Hart ◽  
S. P. Collin
Keyword(s):  
Electric Fields ◽  
Interspecific Variation ◽  
Electrosensory System ◽  
Field Gradients ◽  
Highly Sensitive ◽  
Elasmobranch Species ◽  
Elasmobranch Fishes ◽  
Species Specific ◽  
Port Jackson ◽  
Abundance And Distribution

Elasmobranch fishes (sharks, skates and rays) possess a highly sensitive electrosensory system that enables them to detect weak electric fields, such as those produced by potential prey organisms. Despite several comparative anatomical studies, the functional significance of interspecific variation in electrosensory system morphology remains poorly understood. In the present study, we directly tested the electrosensitivity of two benthic elasmobranchs that share a similar habitat and feed on similarly sized prey items (Port Jackson sharks, Heterodontus portusjacksoni, and western shovelnose rays, Aptychotrema vincentiana), but differ significantly in their electrosensory system morphology. Aptychotrema vincentiana possesses almost five times the number of electrosensory pores of H. portusjacksoni (~1190 and ~239 respectively), yet both species are able to initiate feeding responses to electric-field gradients below 1 nV cm–1, similar to other elasmobranch species tested. However, A. vincentiana showed a greater ability to resolve the specific location of electrosensory stimuli, because H. portusjacksoni would more often overshoot the target and have to turn around to locate it. These results suggested that differences in abundance and distribution of electrosensory pores have little to no effect on the absolute electrical sensitivity in elasmobranchs, and instead, may reflect species-specific differences in the spatial resolution and directionality of electroreception.

scholarly journals Electroreception in the obligate freshwater stingray, Potamotrygon motoro

2015 ◽  
Vol 66 (11) ◽  
pp. 1027 ◽  
Author(s):  
Lindsay L. Harris ◽  
Christine N. Bedore ◽  
Stephen M. Kajiura
Keyword(s):  
Electric Fields ◽  
Sensory System ◽  
Voltage Gradient ◽  
Single Family ◽  
Potential Prey ◽  
Freshwater Environment ◽  
Electrosensory System ◽  
High Impedance ◽  
Morphological Adaptations ◽  
Elasmobranch Fishes

Elasmobranch fishes use electroreception to detect electric fields in the environment, particularly minute bioelectric fields of potential prey. A single family of obligate freshwater stingrays, Potamotrygonidae, endemic to the Amazon River, demonstrates morphological adaptations of their electrosensory system due to characteristics of a high impedance freshwater environment. Little work has investigated whether the reduced morphology translates to reduced sensitivity because of the electrical properties of freshwater, or because of a marine-tuned sensory system attempting to function in freshwater. The objective of the present study was to measure electric potential from prey of Potamotrygon motoro and replicate the measurements in a behavioural assay to quantify P. motoro electrosensitivity. Median orientation distance to prey-simulating electric fields was 2.73cm, and the median voltage gradient detected was 0.20mVcm–1. This sensitivity is greatly reduced compared with marine batoids. A euryhaline species with marine-type ampullary morphology was previously tested in freshwater and demonstrated reduced sensitivity compared with when it was tested in seawater (0.2μVcm–1 v. 0.6nVcm–1). When the data were adjusted with a modified ideal dipole equation, sensitivity was comparable to P. motoro. This suggests that the conductivity of the medium, more so than ampullary morphology, dictates the sensitivity of elasmobranch electroreception.

Investigating the species-specific association between anuran calling phenology and air temperature

2021 ◽  
Author(s):  
Samantha Wong
Keyword(s):  
Climate Change ◽  
Air Temperature ◽  
Management Strategies ◽  
Temporal Trends ◽  
Interspecific Variation ◽  
Northern Ontario ◽  
Anuran Species ◽  
Calling Behaviour ◽  
Survival And Development ◽  
Species Specific

Climate change has been associated in phenological shifts for a variety of taxa. Amphibians, specifically the order Anura (frogs and toads), are considered particularly vulnerable due to their sensitivity to anthropogenic and environmental change. Previous research has documented shifts in the timing of anuran breeding that can be attributed, in part, to climate change, with potential implications for reproduction, survival, and development. This study aims to investigate how air temperature is associated with anuran calling phenology. I will examine the temporal trends in spring and summer air temperature in a lake in northern Ontario, Canada. and quantify seasonal patterns of calling anuran species using acoustic monitoring over a four-month period. I predict that there will be interspecific variation in peak calling associated with air temperature. Additionally, I expect to find asymmetrical association between air temperature and anuran species’ calling behaviour – wherein prolonged breeding species will have a larger optimal temperature range for calling compared to explosive breeding species. The findings of this research will aid in future conservation and provide insight for management strategies of anurans in Canada in response to anticipated climate warming.

scholarly journals Relationships between water transparency and abundance of Cynodontidae species in the Bananal floodplain, Mato Grosso, Brazil

2009 ◽  
Vol 7 (2) ◽  
pp. 251-256 ◽  
Author(s):  
Cesar Enrique de Melo ◽  
Jane Dilvana Lima ◽  
Eliete Francisca da Silva
Keyword(s):  
Fish Assemblages ◽  
Water Transparency ◽  
Predatory Fish ◽  
Mato Grosso ◽  
Central Brazil ◽  
Fish Group ◽  
Species Specific ◽  
Abundance And Distribution ◽  
Number Of Individuals ◽  
Habitat Affinities

The Cerrado in the Central Brazil is currently one of the most threatened ecosystems in the world. As a result, the aquatic habitats in this biome also undergo great impacts. Alterations related to land-use change increase sediment loadings in rivers, streams and lakes, resulting in sedimentation and decrease in water transparency. Water transparency determines underwater visibility conditions, and as a consequence fish assemblages respond to spatial and temporal changes in this variable. This work aimed to examine the influence of transparency on the abundance and distribution of Cynodontidae species, a visually oriented predatory fish group. Fish sampling was conducted in 15 sites located between Mortes and Araguaia rivers in the Bananal floodplain, Mato Grosso State. Regression analysis between relative abundance of Cynodontidae (in number of individuals and biomass) and water transparency showed a positive and highly significant correlation, indicating that this group shows species-specific habitat affinities for clearer waters. These results suggest that the increase in water turbidity in this region can affect the patterns of abundance and distribution of the Cynodontidae species, as well as other visually oriented fishes.

Tapeworm discovery in elasmobranch fishes: quantifying patterns and identifying their correlates

2020 ◽  
Vol 71 (1) ◽  
pp. 78 ◽  
Author(s):  
Haseeb S. Randhawa ◽  
Robert Poulin
Keyword(s):  
Host Species ◽  
Time Lag ◽  
Mixed Effects ◽  
Mixed Effects Models ◽  
Linear Mixed Effects Models ◽  
Linear Mixed Effects ◽  
Factors Influencing ◽  
Elasmobranch Species ◽  
Elasmobranch Fishes ◽  
Latitudinal Range

Most parasites from known host species are yet to be discovered and described, let alone those from host species not yet known to science. Here, we use tapeworms of elasmobranchs to identify factors influencing their discovery and explaining the time lag between the descriptions of elasmobranch hosts and their respective tapeworm parasites. The dataset included 918 tapeworm species from 290 elasmobranch species. Data were analysed using linear mixed-effects models. Our findings indicated that we are currently in the midst of the greatest rate of discovery for tapeworms exploiting elasmobranchs. We identified tapeworm size, year of discovery of the type host, host latitudinal range and type locality of the parasite influencing most on the probability of discovery of tapeworms from elasmobranchs and the average time lag between descriptions of elasmobranchs and their tapeworms. The time lag between descriptions is decreasing progressively, but, at current rates and number of taxonomic experts, it will take two centuries to clear the backlog of undescribed tapeworms from known elasmobranch species. Given that the number of new elasmobranch species described each year is on the rise, we need to re-assess funding strategies to save elasmobranchs (and, thus, their tapeworm parasites) before they go extinct.

scholarly journals Metagenomic Shotgun Analyses Reveal Complex Patterns of Intra- and Interspecific Variation in the Intestinal Microbiomes of Codfishes

2020 ◽  
Vol 86 (6) ◽  
Author(s):  
Even Sannes Riiser ◽  
Thomas H. A. Haverkamp ◽  
Srinidhi Varadharajan ◽  
Ørnulf Borgan ◽  
Kjetill S. Jakobsen ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Interspecific Variation ◽  
Shotgun Sequencing ◽  
Intestinal Microbiome ◽  
Ecological Niches ◽  
Content Type ◽  
Evolutionary Trajectories ◽  
Species Specific

ABSTRACT The relative importance of host-specific selection or environmental factors in determining the composition of the intestinal microbiome in wild vertebrates remains poorly understood. Here, we used metagenomic shotgun sequencing of individual specimens to compare the levels of intra- and interspecific variation of intestinal microbiome communities in two ecotypes (NEAC and NCC) of Atlantic cod (Gadus morhua) that have distinct behavior and habitats and three Gadidae species that occupy a range of ecological niches. Interestingly, we found significantly diverged microbiomes among the two Atlantic cod ecotypes. Interspecific patterns of variation are more variable, with significantly diverged communities for most species’ comparisons, apart from the comparison between coastal cod (NCC) and Norway pout (Trisopterus esmarkii), whose community compositions are not significantly diverged. The absence of consistent species-specific microbiomes suggests that external environmental factors, such as temperature, diet, or a combination thereof, comprise major drivers of the intestinal community composition of codfishes. IMPORTANCE The composition of the intestinal microbial community associated with teleost fish is influenced by a diversity of factors, ranging from internal factors (such as host-specific selection) to external factors (such as niche occupation). These factors are often difficult to separate, as differences in niche occupation (e.g., diet, temperature, or salinity) may correlate with distinct evolutionary trajectories. Here, we investigate four gadoid species with contrasting levels of evolutionary separation and niche occupation. Using metagenomic shotgun sequencing, we observed distinct microbiomes among two Atlantic cod (Gadus morhua) ecotypes (NEAC and NCC) with distinct behavior and habitats. In contrast, interspecific patterns of variation were more variable. For instance, we did not observe interspecific differentiation between the microbiomes of coastal cod (NCC) and Norway pout (Trisopterus esmarkii), whose lineages underwent evolutionary separation over 20 million years ago. The observed pattern of microbiome variation in these gadoid species is therefore most parsimoniously explained by differences in niche occupation.

Atomic origins of molecular polarizabilities

1996 ◽  
Vol 74 (6) ◽  
pp. 1131-1138 ◽  
Author(s):  
Keith E. Laidig
Keyword(s):  
Carbon Monoxide ◽  
Spatial Distribution ◽  
Quantum Mechanics ◽  
Key Words ◽  
Electric Fields ◽  
Polarizability Tensor ◽  
Electronic Charge ◽  
Field Gradients ◽  
Carbon Sulfide ◽  
Molecular Polarizabilities

We demonstrate that the multipole polarizability tensors of a molecule are expressible as a sum of atomic contributions, each of which is based upon the change in the spatial distribution of electronic charge within each atom resulting from the application of electric fields and field gradients. The use of the spatially defined atoms of subsystem quantum mechanics correctly partitions molecular polarizabilities into physically meaningful atomic contributions. It is shown that the origin of any molecular polarizability tensor may be understood from an investigation of these contributions and the general expressions for the summation of atomic components to yield molecular polarizabilities are presented. Their use is demonstrated by the construction and investigation of the axial components of the dipole–dipole dipole–quadrupole, and quadrupole–quadrupole polarizability tensors of carbon monoxide and carbon sulfide. Key words: atomic polarizabilities, atoms-in-molecules, molecular polarizabilities.

scholarly journals Detection and processing of electromagnetic and near–field acoustic signals in elasmobranch fishes

2000 ◽  
Vol 355 (1401) ◽  
pp. 1135-1141 ◽  
Author(s):  
Ad. J. Kalmijn
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Cell Membranes ◽  
Near Field ◽  
Feedback Mechanism ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field ◽  
Positive Feedback Mechanism ◽  
Elasmobranch Fishes ◽  
Physical Features

The acoustic near field of quietly moving underwater objects and the bio–electric field of aquatic animals exhibit great similarity, as both are predominantly governed by Laplace's equation. The acoustic and electrical sensory modalities thus may, in directing fishes to their prey, employ analogous processing algorithms, suggesting a common evolutionary design, founded on the salient physical features shared by the respective stimulus fields. Sharks and rays are capable of orientating to the earth's magnetic field and, hence, have a magnetic sense. The electromagnetic theory of orientation offers strong arguments for the animals using the electric fields induced by ocean currents and by their own motions in the earth's magnetic field. In the animal's frame of reference, in which the sense organs are at rest, the classical concept of motional electricity must be interpreted in relativistic terms. In the ampullae of Lorenzini, weak electric fields cause the ciliated apical receptor–cell membranes to produce graded, negative receptor currents opposite in direction to the fields applied. The observed currents form part of a positive–feedback mechanism, supporting the generation of receptor potentials much larger than the input signal. Acting across the basal cell membranes, the receptor potentials control the process of synaptic transmission.

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