Preliminary Investigation on the Physiology and Ecology of Luminescence in the Copepod, Metridia lucens

1. Skin glands believed to be the source of luminescence were found on the anterior portion of the head, on the last thoracic segment, and on the posterior margins of each segment of the abdomen. 2. The maximum intensity of the luminescent flash was 1.2 x 10-3 µw./cm.2 (at 18 cm.). The flash rose rapidly to peak intensity and then decayed slowly. The total duration of the flashes with peaks greater than 10-4 µw./cm.2 ranged from 3 to 50 seconds. 3. The peak of the luminescence spectrum occcurred at 482 mµ and the curve fell off to one-half the maximum value at 440 mµ and 525 mµ. 4. The ability of Metridia to luminesce on stimulation was found to be largely unaffected by prolonged laboratory culture. Starvation had little effect on the luminescence for the first three weeks and there was never any inhibition by previous light- or dark-adaptation. 5. With an increase in the strength of the electric stimulus from 0.3 amp. to 0.7 amp., the intensity of the luminescent flash was found to increase. With pulses stronger than 0.7 amp. no change in intensity was recorded but the number of successive responses to repeated stimuli was reduced. Duration of the pulse had little effect on the intensity or the number of successive responses. 6. Metridia showed a lag time of 8-10 msc. to the beginning of the luminescent response. The lag time to the peak of the luminescent response varied from 20 to 60 msc. 7. There was no spontaneous luminescence produced by groups of Metridia under conditions of constant darkness. However, the presence of certain planktonic predators, most notably Meganyctiphanes norvegica, caused a brilliant display of luminescence. The number of flashes attributable to Metridia was always greater than the number of Metridia eaten by the predator. There was little evidence that the luminescent euphausiid, Meganyctiphanes, flashed spontaneously either in the presence or absence of its prey. 8. Observations on the behavior of Metridia during and just after luminescence suggest that the flashing may be involved in an escape mechanism, but the precise effect of the light on the predator has not been determined

Dark-Season Survival Strategies of Coastal Zone Zooplankton in the Canadian Arctic

For herbivorous zooplankton, surviving the arctic winter requires that sufficient energy be stored in summer to enable ten months or more of possible starvation. Energy and materials for reproduction may also be totally derived from stored lipid and bodily protein. The predominant storage products are wax esters, often visible as translucent droplets or a fusiform inclusion in the tissues. Lipid may constitute more than 50% of dry weight at the end of summer. Reproduction is synchronized with season and environmental conditions to enable offspring to exploit the brief period of intense primary production. So far as we know, fertilization occurs only once in the copepods studied here, which make up more than 98% of the total zooplankton by numbers, and males are short lived, but in one species (Calanus hyperboreus) females may survive into a second productive season, thereby storing sufficient reserves to spawn a second time. Several plaktonic species, including larval invertebrates, start growth early by utilizing algae that develop on the under-ice surface serveral months before the pelagic phytoplankton bloom. The minimum water temperature (-1.8 C) is constant and much warmer than the atmosphere, so overwintering should be less stressful for aquatic species than for terrestrial forms. Additional adaptations used by zooplankton in winter include seeking deeper water to escape predation, reducing swimming costs by regulating buoyancy, and further lowering metabolic rates by limiting synthesis of enzymes and increasing the fraction of lipid used in respiration.Key words: copepods, zooplankton, phytoplankton, ice-algae, fast ice, lipid, overwintering, survival strategies, growth, reproduction Afin de survivre à l'hiver arctique, le zooplancton herbivore doit stocker suffisamment d'énergie en été pour faire face à 10 mois ou plus de famine potentielle. Il se peut aussi que l'énergie et les matériaux servant à la reproduction soient tirés en totalité des lipides emmagasinés et des protéines du tissu corporel. Les produits stockés les plus importants sont les esters cireux, souvent visibles sous la forme de gouttelettes translucides ou d'une inclusion fusiforme dans les tissus. Les lipides peuvent constituer plus de 50 p. cent du poids sec à la fin de l'été. La reproduction est synchronisée avec les saisons et les conditions environnementales de façon à permettre à la progéniture de profiter de la courte période de production primaire intense. Dans l'état de nos connaissances actuelles, la fertilisation a lieu une seule fois chez les copépodes qui nous intéressent, et qui constituent plus de 98 p. cent du zooplancton total sur le plan numérique. Les mâles ont une durée de vie relativement courte, mais dans l'espèce Calanus hyperboreus, les femelles peuvent vivre assez longtemps pour entrer dans une deuxième phase de reproduction, stockant ainsi suffisamment de réserves pour frayer une seconde fois. Plusieurs espèces planctoniques, y compris des invertébrés larvaires, commencent à croître de bonne heure, en utilisant les algues qui se développent sur le dessous de la glace plusieurs mois avant la prolifération du phytoplancton pélagique. La température minimale de l'eau (-1,8 °C) est constante et beaucoup plus élevée que l'atmosphère, ce qui devrait rendre la survie hiémale moins stressante pour les espèces aquatiques que pour les formes terrestres. Parmi les autres adaptations utilisées par le zooplancton en hiver, on compte la recherche d'eaux plus profondes pour échapper aux prédateurs, la réduction du coût de la natation grâce à une régulation de la flottabilité, ainsi que la réduction du taux de métabolisme par une limite de la synthèse des enzymes et l'augmentation de la portion de lipides utilisés dans la respiration.Mots clés : copépodes, zooplancton, phytoplancton, algues glaciaires, banquise côtière, lipides, survie hiémale, stratégies de survie, croissance, reproductio

Volume 15. Article 1. Oceanography of Long Island Sound, 1952–1954.

https://elischolar.library.yale.edu/bulletin_yale_bingham_oceanographic_collection/1154/thumbnail.jp

Statistics of an Unstable Barotropic Jet from a Cumulant Expansion

Low-order equal-time statistics of a barotropic flow on a rotating sphere are investigated. The flow is driven by linear relaxation toward an unstable zonal jet. For relatively short relaxation times, the flow is dominated by critical-layer waves. For sufficiently long relaxation times, the flow is turbulent. Statistics obtained from a second-order cumulant expansion are compared to those accumulated in direct numerical simulations, revealing the strengths and limitations of the expansion for different relaxation times.Comment: 23 pages, 8 figures. Version to appear in J. Atmos. Sc

Energy Flow through the Marine Ecosystem of the Lancaster Sound Region, Arctic Canada

This paper synthesizes the trophic dynamics of a Canadian arctic marine ecosystem in so far as it is known, using new data on primary production, zooplankton, the bivalve Mya truncata, and arctic cod (Boreogadus saida), as well as literature values for marine mammals and seabirds. The 98,000 sq km region has a high rate of primary production relative to other parts of arctic Canada. About 60 g C/sq. m are fixed annually, of which approximately 90% is contributed by phytoplankton, 10% by ice algae, and 1% by kelp. Phytoplankton production is twofold higher along the south coast of Cornwallis Island than elsewhere in Barrow Strait. Four copepod species, of which Pseudocalanus acuspes is the most important energetically, graze about one-third of the phytoplankton production. Bivalves maintain high biomass but low energy flow, acting as sedimenting agents. Arctic cod is a major component, with 125,000 tonnes being consumed by marine mammals and 23,000 tonnes by seabirds annually. Our hydro-acoustic estimate for mean arctic cod density, 0.0022 fish/sq. m, is probably too low, partly because we have been unable to quantify dense aggregations of schooling fish. The ecological efficiency of ringed seal is near maximum, with 5% of ringed seal ingestion going to bears and man as seal flesh. The data on total kill and prey consumption in whales and birds is incomplete because they migrate out of the Lancaster Sound region in winter. The food chain is very long, with bears occupying the fifth trophic level; this is reflected by high biomagnification factors for persistent lipophilic pollutants such as PCBs. There are major data gaps for some zooplankton and most of the benthos, as well as for winter populations and energetics. This trophic analysis is therefore incomplete and efficiencies for entire trophic levels cannot be calculated.Key words: seals, whales, seabirds, benthos, zooplankton, phytoplankton, primary production, secondary production, harvest, yieldRÉSUMÉ. Cet article résume la dynamique trophique de l’écosystème marin dans le Canada arctique dans la mesure où il est connu, en utilisant de nouvelles données sur la production primaire, le zooplancton, le bivalve Mya truncata, et la morue polaire (Boreogadus saida), ainsi que les valeurs trouvées dans la documentation sur les mammifères et les oiseaux marins. Cette région d’une superficie de 98 000 km2 possède un taux élevé de production primaire par rapport à d’autres parties du Canada arctique. Environ 60 g C.m-2 sont fixés annuellement, dont environ 90 p. cent par le phytoplancton, 10 p. cent par les algues glaciaires et 1 p. cent par les laminaires. La production de phytoplancton est deux fois plus élevée le long de la côte méridionale de l’île Cornwallis qu’ailleurs dans le détroit de Barrow. Quatre espèces de copépodes, dont la Pseudocalanus acuspes est la plus importante du point de vue énergitique, utilisent environ un tiers de la production de phytoplancton pour se nourir. Les bivalves contribuent de façonimportante à la biomasse mais peu au flux énergétique, étant des agents de sédimentation. La morue arctique est une composante importante, étant consommée au taux annuel de 1250 00 tonnes par les mammifères marins et de 23 000 tonnes par les oiseaux marins. Notre estimation hydroacoustique pour la densité moyenne de la morue arctique, 0,002 poissons.m-2, est probablement trop faible, en partie parce que nous avons été incapables de quantifier les regroupements denses des poissons se rassemblant en bancs. L’efficacité écologique du phoque annelé est proche de son maximum, 5 p. cent de l’ingestion de cet animal allant à l’ours et à l’homme sous forme de chair de phoque. Les données sur le nombre d’animaux tués et sur laconsommation de proies chez les baleines et les oiseaux sont incomplètes en raison de leur migration hivernal à  l'extérieur du détroit de Lancaster. La chaine alimentaire est très longue, les ours occupant le cinquième niveau trophique; cela se traduit par des facteurs de bioamplification élevés en ce qui concerne les polluants lipophiles persistants tels que les BPC. Il existe des lacunes dans les données pour certains éléments du zooplancton et pour la plupart du benthos, ainsi que pour les populations et l’énergétique hivernales. Cette analyse trophique est donc incomplète et il n'est pas possible de calculer l’efficacité pour l’ensemble des niveaux trophiques.Mots clés: phoques, baleines, oiseaux marins, benthos, zooplancton, phytoplancton, production primaire, production secondaire, prélèvement, rendemen

Gear-Specific Population Demographics of Channel Catfish in a Large Midwestern River

Various gear types have been used to sample populations of channel catfish Ictalurus punctatus in lotic systems. However, these gears produce different population characteristics (i.e., recruitment, growth, and mortality). We compared the population demographics of channel catfish in the Wabash River, Indiana, sampled with baited 25- and 32-mm-bar mesh hoop nets and three-phase alternating current (AC) electrofishing. Based on catch per unit effort, the relative abundance of channel catfish sampled with 32-mm hoop nets was lower than that of fish sampled with 25-mm hoop nets and AC electrofishing. Each gear type also resulted in a different length frequency, mean length increasing progressively in sampling with 25-mm hoop nets, 32-mm hoop nets, and AC electrofishing. Similarly, age-frequency distributions differed among gears. The 25-mm hoop nets biased the age structure toward younger individuals (mean age = 2.5), whereas both 32-mm hoop nets (mean age = 4.0) and AC electrofishing (mean age = 5.8) included older fish. Catch-curve analysis generated different mortality rates for the three gear types, the mortality rate being highest (50%) in fish sampled with 25-mm hoop nets. Gear-specific size and age structures led to differences in von Bertalanffy statistics among the 25-mm hoop nets and AC electrofishing, while the results for 32-mm hoop nets were uninterpretable. Because the different gears led to conflicting parameter estimates, management practices based on sampling with single gears may be contradictory. Given the differences in gear selectivity, biologists need to approach management cautiously until calibration to the true size and age structure is conducted

Movement and Habitat Selection by Invasive Asian Carps in a Large River

We evaluated the habitat use and movements of 50 adult bighead carp Hypophthalmichthys nobilis and 50 silver carp H. molitrix by means of ultrasonic telemetry during spring–summer 2004 and 2005 to gain insight into the conditions that facilitate their establishment, persistence, and dispersal in the lower Illinois River (river kilometer 0–130). Movement and habitat use were monitored with stationary receivers and boat-mounted tracking. The relative availability of four macrohabitat categories (main channel, island side channel, channel border, and connected backwater) was quantified to determine selection; discriminant function analysis was used to evaluate changes in physical characteristics within each category. A flood pulse occurred in spring through early summer of 2004 but not 2005. Movement rates (km/week) of both species were positively correlated with flow but not with temperature. Including data from stationary receivers greatly increased estimates of daily movement. During low summer flow, both species typically selected channel borders and avoided the main channel and backwaters. Both species rarely occupied depths over 4 m, regardless of abiotic conditions. Flood pulses appear to trigger dispersal, while habitat use is only specific during low summer flow. Thus, movement prevention efforts (e.g., dispersal barriers) will require particular vigilance during late-winter or spring flooding, and controlled removal (e.g., harvest) should be directed toward selected habitats during summer

The evolution of the urinary bladder as a storage organ: scent trails and selective pressure of the first land animals in a computational simulation

The function of waste control in all living organisms is one of the vital importance. Almost universally, terrestrial tetrapods have a urinary bladder with a storage function. It is well documented that many marine and aerial species do not have an organ of such a function, or have one with very depressed storage functionality. Bladder morphology indicates it has evolved from a thin-walled structure used for osmoregulatory purposes, as it is currently used in many marine animals. It is hypothesised that the storage function of the urinary bladder allows for an evolutionary selective advantage in reducing the likelihood of successful predation. Random walks simulating predator and prey movements with simplified scent trails were utilised to represent various stages of the hunt: Detection and pursuit. A final evolutionary model is proposed in order to display the advantages over inter-generational time scales and illustrates how a bladder may evolve from an osmoregulatory organ to one of the storage. Data sets were generated for each case and analysed indicating the viability of such advantages. From the highly consistent results, three distinct characteristics of having a storage function in the urinary bladder are suggested: reduced scent trail detection rate; increased prey–predator separation (upon scent trail detection); and a reduced probability of successful capture upon scent detection by the predator. Furthered by the evolutionary model indicating such characteristics are conserved and augmented over many generations, it is concluded that prey–predator interactions provide a large selective pressure in the evolution of the urinary bladder and its storage function