Rachel Ball - Academia.edu (original) (raw)

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Vinod K K

INDIAN AGRICULTURAL RESEARCH INSTITUTE, NEW DELHI, INDIA

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Papers by Rachel Ball

Environmental Biology of Fishes

Batoid fishes are among the most endangered marine vertebrates, yet conservation efforts have bee... more Batoid fishes are among the most endangered marine vertebrates, yet conservation efforts have been confounded by incomplete taxonomy. Evidence suggest that the critically endangered ‘common skate’ actually represents two species: the flapper skate (Dipturus intermedius) and the blue skate (Dipturus batis). However, knowledge of the geographic range of these two nominal species is limited. Here, DNA sequencing is used to distinguish these species, allowing their spatial distributions to be clarified. These records were also used as the basis for species distribution modelling, providing the first broad scale models for each species across the Northeast Atlantic. Samples were obtained from Iceland, the UK (specifically Shetland), the North Sea and the Azores. Results suggest that D. batis was commonly distributed in the Western Approaches and Celtic Sea, extending out to Rockall and Iceland. D. intermedius generally appears to be less abundant, but was most frequent around northern Sc...

Conservation Genetics, 2016

Skates and rays constitute the most speciose group of chondrichthyan fishes, yet are characterise... more Skates and rays constitute the most speciose group of chondrichthyan fishes, yet are characterised by remarkable levels of morphological and ecological conservatism. They can be challenging to identify, which makes monitoring species compositions for fisheries management purposes problematic. Owing to their slow growth and low fecundity, skates are vulnerable to exploitation and species exhibiting endemism or limited ranges are considered to be the most at risk. The Madeira skate Raja maderensis is endemic and classified as ‘Data Deficient’ by the IUCN, yet its taxonomic distinctiveness from the morphologically similar and more wide-ranging thornback ray Raja clavata is unresolved. This study evaluated the sequence divergence of both the variable control region and cytochrome oxidase I ‘DNA barcode’ gene of the mitochondrial genome to elucidate the genetic differentiation of specimens identified as R. maderensis and R. clavata collected across much of their geographic ranges. Geneti...

Journal of Avian Biology, 2015

Developmental Neurobiology, 2015

Predator avoidance is fundamental for survival and it can be particularly challenging for prey an... more Predator avoidance is fundamental for survival and it can be particularly challenging for prey animals if physical movement away from a predatory threat is restricted. Many sharks and rays begin life within an egg capsule that is attached to the sea bed. This sedentary life stage is especially vulnerable as the ventilatory activity of embryos creates cues that increase the risk of detection by predators. The embryos can reduce this risk by mediating their ventilation activity if they detect the presence of a predator using their acute electrosense. We tested the behavioural responses of three different age groups (1/3 developed, 2/3 developed and near hatching) of embryonic thornback rays Raja clavata to the presence of potential predators using predator-type electric field stimuli to determine how early in embryonic life predator elicited behavioural responses can occur. Egg capsules were exposed to continuous or intermittent stimuli in order to assess varying predator-type encounter scenarios on the ventilatory behaviour for the different developmental stages. All embryos reacted with a 'freeze response' following initial electric field exposure, ceasing ventilatory behaviour in response to predator presence, demonstrating innate functionality at the earliest possible stage in ontogeny. This ability coincides with the onset of egg ventilatory behaviour and may represent a sophisticated means to enhance survival. A continuous application of stimuli over time revealed that embryos can adapt their behaviour and resume normal activity, whereas when presented intermittently, the E-field resulted in a significant reduction in overall ventilatory activity across all ages. Recovery from stimuli was significantly quicker in older embryos, indicative of the delicate trade-off between avoiding predation and adequate respiration.

Choice Reviews Online, 2015

Journal of Fish Biology, 2013

Environmental Biology of Fishes

Batoid fishes are among the most endangered marine vertebrates, yet conservation efforts have bee... more Batoid fishes are among the most endangered marine vertebrates, yet conservation efforts have been confounded by incomplete taxonomy. Evidence suggest that the critically endangered ‘common skate’ actually represents two species: the flapper skate (Dipturus intermedius) and the blue skate (Dipturus batis). However, knowledge of the geographic range of these two nominal species is limited. Here, DNA sequencing is used to distinguish these species, allowing their spatial distributions to be clarified. These records were also used as the basis for species distribution modelling, providing the first broad scale models for each species across the Northeast Atlantic. Samples were obtained from Iceland, the UK (specifically Shetland), the North Sea and the Azores. Results suggest that D. batis was commonly distributed in the Western Approaches and Celtic Sea, extending out to Rockall and Iceland. D. intermedius generally appears to be less abundant, but was most frequent around northern Sc...

Conservation Genetics, 2016

Skates and rays constitute the most speciose group of chondrichthyan fishes, yet are characterise... more Skates and rays constitute the most speciose group of chondrichthyan fishes, yet are characterised by remarkable levels of morphological and ecological conservatism. They can be challenging to identify, which makes monitoring species compositions for fisheries management purposes problematic. Owing to their slow growth and low fecundity, skates are vulnerable to exploitation and species exhibiting endemism or limited ranges are considered to be the most at risk. The Madeira skate Raja maderensis is endemic and classified as ‘Data Deficient’ by the IUCN, yet its taxonomic distinctiveness from the morphologically similar and more wide-ranging thornback ray Raja clavata is unresolved. This study evaluated the sequence divergence of both the variable control region and cytochrome oxidase I ‘DNA barcode’ gene of the mitochondrial genome to elucidate the genetic differentiation of specimens identified as R. maderensis and R. clavata collected across much of their geographic ranges. Geneti...

Journal of Avian Biology, 2015

Developmental Neurobiology, 2015

Predator avoidance is fundamental for survival and it can be particularly challenging for prey an... more Predator avoidance is fundamental for survival and it can be particularly challenging for prey animals if physical movement away from a predatory threat is restricted. Many sharks and rays begin life within an egg capsule that is attached to the sea bed. This sedentary life stage is especially vulnerable as the ventilatory activity of embryos creates cues that increase the risk of detection by predators. The embryos can reduce this risk by mediating their ventilation activity if they detect the presence of a predator using their acute electrosense. We tested the behavioural responses of three different age groups (1/3 developed, 2/3 developed and near hatching) of embryonic thornback rays Raja clavata to the presence of potential predators using predator-type electric field stimuli to determine how early in embryonic life predator elicited behavioural responses can occur. Egg capsules were exposed to continuous or intermittent stimuli in order to assess varying predator-type encounter scenarios on the ventilatory behaviour for the different developmental stages. All embryos reacted with a 'freeze response' following initial electric field exposure, ceasing ventilatory behaviour in response to predator presence, demonstrating innate functionality at the earliest possible stage in ontogeny. This ability coincides with the onset of egg ventilatory behaviour and may represent a sophisticated means to enhance survival. A continuous application of stimuli over time revealed that embryos can adapt their behaviour and resume normal activity, whereas when presented intermittently, the E-field resulted in a significant reduction in overall ventilatory activity across all ages. Recovery from stimuli was significantly quicker in older embryos, indicative of the delicate trade-off between avoiding predation and adequate respiration.

Choice Reviews Online, 2015

Journal of Fish Biology, 2013

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