Topic
Phronima
About: Phronima is a research topic. Over the lifetime, 33 publications have been published within this topic receiving 468 citations.
Papers
TL;DR: The diets of 5 large predatory mesopelagic fishes (Alepisaurus ferox (longnosed lancetfish), Gempylus serpens (snake mackerel), Lepidocybium flavobrunneum (Smith's escolar), and Lampris spp. as discussed by the authors were examined from the central North Pacific Ocean (around Hawaii) for the first time.
Abstract: The diets of 5 large predatory mesopelagic fishes—Alepisaurus ferox (longnosed lancetfish), Gempylus serpens (snake mackerel), Lepidocybium flavobrunneum (Smith's escolar), and Lampris spp. (big-eye and small-eye opah, or moonfish)—from the central North Pacific Ocean (around Hawaii) were examined (n = 430, all species combined), most for the first time. Recent analysis of fishery data has shown that many of these species have been undergoing decadal increases in abundance, suggesting system-wide changes. A. ferox diet was numerically dominated by hyperiid amphipods from 3 genera (Phrosina, Phronima, Platyscelus; 37%N), pelagic polychaete worms, mesopelagic fishes (including young A. ferox size classes), and cephalopods. G. serpens fed primarily on epipelagic fishes (exocoetids, molids) and ommastrephid squids. Diets of the 2 Lampris species were the most similar to one another, consisting of large numbers and frequent occurrences of the onychoteuthid squid Walvisteuthis youngorum and a diverse assemblage of epipelagic and mesopelagic fishes. More than 90% of the L. flavobruneum stomachs were without food items; small numbers of prey identified included the ommastrephid squid Sthenoteuthis oualaniensis, aristeid shrimps, and unidentified fishes. The diet descriptions support the idea that these predatory fishes carve out unique ecological niches in the pelagic envi- ronment by exploiting unique components of micronekton communities across epipelagic and mesopelagic depth zones. Adult size classes of tunas and billfishes occupying a shared vertical habitat do not appear to compete for prey resources to any great extent, perhaps allowing for suc- cessful partitioning of limited prey resources within an oligotrophic gyre ecosystem.
75 citations
TL;DR: The medial eyes of Phronima appear to be a solution to the problem of remaining inconspicuous to predators while still maintaining sensitivity and resolution.
Abstract: Pelagic amphipods belonging to the genus Phronima have four compound eyes; two lateral eyes and two large transparent medial eyes which comprise the entire top of the head. The eyes are structurally similar but the crystalline cones of the medial eyes are more than twenty times as long as those of the lateral eyes, reaching 5 mm in a large animal. The dioptric system of each ommatidium consists of an unfaceted cornea, a layer of hypodermal cells, two rudimentary cone cells, two cells which surround and form the crystalline cone, and the cone itself. The cone and its surrounding cells penetrate the layer of accessory pigment cells which surrounds the retina. The fused rhabdom is formed by the five retinula cells but is separated from them by an extracellular palisade which is crossed by bridges. The retinula cell nuclei lie proximal to the basement membrane. Further proximally the bundle of retinula cell axons is crossed by a second basement membrane, which surrounds each axon with a collar. Medial and lateral eyes on each side of the head share a common lamina. The medial eyes of Phronima appear to be a solution to the problem of remaining inconspicuous to predators while still maintaining sensitivity and resolution.
56 citations
Journal Article•
TL;DR: The diets of 5 large predatory mesopelagic fishes—Alepisaurus ferox (longnosed lancetfish), Gempylus serpens (snake mackerel), Lepidocybium flavobrunneum (Smith's escolar), and Lampris spp. (big-eye and small-eye opah, or moonfish)—from the central North Pacific Ocean were examined, most for the first time.
Abstract: The diets of 5 large predatory mesopelagic fishes—Alepisaurus ferox (longnosed lancetfish), Gempylus serpens (snake mackerel), Lepidocybium flavobrunneum (Smith’s escolar), and Lampris spp. (big-eye and small-eye opah, or moonfish)—from the central North Pacific Ocean (around Hawaii) were examined (n = 430, all species combined), most for the first time. Recent analysis of fishery data has shown that many of these species have been undergoing decadal increases in abundance, suggesting system-wide changes. A. ferox diet was numerically dominated by hyperiid amphipods from 3 genera (Phrosina, Phronima, Platyscelus; 37%N), pelagic polychaete worms, mesopelagic fishes (including young A. ferox size classes), and cephalopods. G. serpens fed primarily on epipelagic fishes (exocoetids, molids) and ommastrephid squids. Diets of the 2 Lampris species were the most similar to one another, consisting of large numbers and frequent occurrences of the onychoteuthid squid Walvisteuthis youngorum and a diverse assemblage of epipelagic and mesopelagic fishes. More than 90% of the L. flavobruneum stomachs were without food items; small numbers of prey identified included the ommastrephid squid Sthenoteuthis oualaniensis, aristeid shrimps, and unidentified fishes. The diet descriptions support the idea that these predatory fishes carve out unique ecological niches in the pelagic environment by exploiting unique components of micronekton communities across epipelagic and mesopelagic depth zones. Adult size classes of tunas and billfishes occupying a shared vertical habitat do not appear to compete for prey resources to any great extent, perhaps allowing for successful partitioning of limited prey resources within an oligotrophic gyre ecosystem.
43 citations
TL;DR: Video recordings were made of the behaviour of hyperiid amphipods and other mid-water crustaceans in a tank lit from above with a dim VDU screen and from behind with infra-red light, finding three kinds of visual behaviour seen consistently.
Abstract: Video recordings were made of the behaviour of hyperiid amphipods and other mid-water crustaceans in a tank lit from above with a dim VDU screen, and from behind with infra-red light. Computer-generated stimuli could be moved across the VDU screen. Amphipods swam at speeds up to 19 body lengths per second. Some (Brachyscelus, Phrosina) consistently swam inverted, rolling from side to side. Others (Platyscelus, Parapronoe) spent periods of time rotating in the water with the dorsal acute zone of the eye pointing upwards. Both behaviours are interpreted as forms of visual scanning. Different species were active at different light levels, Phronima preferring the dimmest illumination. Three kinds of visual behaviour were seen consistently. The animals dropped from the surface as a dark square passed above them; they tracked other individuals (Hyperiids) or, in the case of Euphausiids, the stimuli on thescreen above; and they occasionally swam towards each other and collided, apparently deliberately.
24 citations
TL;DR: To determine if the natural temperature gradient experienced by P. sedentaria results in a thermal stress response, individuals were initially exposed to their night time temperatures and subsequently subjected to temperatures within and above the range they typically experience.
Abstract: The hyperiid amphipod Phronima sedentaria experiences a temperature change of 15 °C during diel migration in the Eastern Tropical North Pacific (ETNP) from 8-10 °C at depth to 25-27 °C at night in the surface waters. The aim of this study was to determine if the natural temperature gradient experienced by P. sedentaria results in a thermal stress response. Individuals were initially exposed to their night time temperatures (23 °C) and subsequently subjected to temperatures within and above the range they typically experience. In the Eastern Tropical North Pacific P. sedentaria tolerates its normal night-time temperature (~23 °C), but only for the duration of its stay there (~9 h). Longer exposures (24 h) result in elevated heat shock protein (hsp) expression. 29 °C results in hsp expression, increased lactate production and 50% mortality at all exposure durations. This represents an upper critical temperature. Understanding the adaptations of pelagic amphipods to their current environment will help predict the physiological impacts of global warming for amphipods and their predators.
21 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2020 | 4 |
| 2019 | 1 |
| 2017 | 1 |
| 2016 | 1 |
| 2015 | 3 |
| 2014 | 1 |