Praunus Flexuosus Research Articles

Seasonality of caridean decapod and mysid distribution and movements within the Severn Estuary and Bristol Channel

Mysids and caridean decapods are a significant proportion of the biomass within the Bristol Channel and Severn Estuary and key members of the marine food web in this estuarine system. Annual patterns of abundance at Hinkley Point Power Station of the mysids Praunus flexuosus, Schistomysis spiritus, Noemysis integer, Mesopodopsis slabberi and Gastrosaccus spinifer and of the carideans Pasiphaea sivado, Palaemon serratus, Pandalus montagui, Crangon crangon and C. allmani are examined. Using population age structures and sex ratios, the patterns of seasonal migration and recruitment are discussed.

Seasonality of caridean decapod and mysid distribution and movements within the Severn Estuary and Bristol Channel

Mysids and caridean decapods are a significant proportion of the biomass within the Bristol Channel and Severn Estuary and key members of the marine food web in this estuarine system. Annual patterns of abundance at Hinkley Point Power Station of the mysids Praunus flexuosus, Schistomysis spiritus, Noemysis integer, Mesopodopsis slabberi and Gastrosaccus spinifer and of the carideans Pasiphaea sivado, Palaemon serratus, Pandalus montagui, Crangon crangon and C. allmani are examined. Using population age structures and sex ratios, the patterns of seasonal migration and recruitment are discussed.

Toxicity of rotenone to some potential predators on marine fish larvae — An experimental study

Toxicity of rotenone to some potential predators on marine fish larvae was tested experimentally. Degradation of rotenone in seawater was 0·57% h −1 at 50 lux and 10°C. The content of active rotenone in the commercial solution was, on average, 79% of the expected value, probably caused by age degradation of the product. Fifty per cent mortality of the gobid Gobiusculus flavescens Fabricius occurred after 36, 16 and 5 h in 0·10, 0·25 and 0·50 ppm rotenone solutions, respectively. Fifty per cent mortality of the mysid Praunus flexuosus (O. F. Müller) occurred after 27 h in 5·0 ppm solution. Of the tested species, the carid shrimp Leander squilla L. had the highest tolerance to rotenone, and 10 ppm was necessary to kill all specimens within 48 h. Fifty per cent mortality was registered within 19 h at 10 ppm. The results are primarily compared with studies on limnetic species due to lack of data on marine organisms.

Locomotor activity patterns of nineteen fish and five crustacean species from the Baltic Sea

Activity patterns of some common Baltic fish species and macrocrustaceans have been investigated in natural light/dark conditions — in most cases for periods of at least one full year. The fauna of the northern Baltic proper consists of species of both marine and freshwater origin, with both types represented in the study. The different patterns found are discussed in relation to light period, light intensity and to the structure and function of the eyes. The following species were considered nocturnal: Idothea baltica, Mesidothea entomon, Gammarus oceanicus, Palaemon adspersus, Anguilla anguilla, Spinachia spinachia, Pholis gunnellus, Zoarces viviparus, Scopthalmus maximus, and Platichtys flesus. These species were considered diurnal: Clupea harengus, Scardinius erythrophthalmus, Gasterosteus aculeatus, Perca fluviatilis, Gobius niger, Taurulus bubalis, and Cyclopterus lumpus. The next three species showed a crepuscular pattern of activity: Praunus flexuosus, Esox lucius and Gymnocephalus cernus. Four species were considered to show inversions of the activity patterns: Pungitius pungitius, Pomatoschistus minutus, Myoxocephalus scorpius and M. quadricornis.

The toxicity of chromium, nickel and zinc: effects of salinity and temperature, and the osmoregulatory consequences in the mysid Praunus flexuosus

The effect of salinity (4.5–27ℵ) and temperature (5 and 15°C) on the acute toxicity of chromium, nickel and zinc to the mysid crustacean Praunus flexuosus (Müller) has been investigated, at time intervals up to 300 h. Increased metal concentration led to reduced median survival time. Increased temperature, and salinities above or below the isosmotic point, led to reduced median survival times at a given metal concentration and reduced median lethal concentrations of metals. The effect of salinity on metal toxicity has been clearly linked to disruption of the normal pattern of hyper/hypoosmoregulation. The death of animals in chromium or zinc solutions may be related to a progressive decrease in the ability of the animals to osmoregulate, with the rate of osmotic decline related to the median survival time, or the loss of osmoregulatory ability may be a secondary effect of metal poisoning and dying. Nickel was found to be less toxic than either chromium or zinc and to have less effect on osmoregulation.

Records and life history of Praunus flexuosus (Crustacea: Mysidacea) in Icelandic waters

Since its fust record in Icelandic waters in 1970, Praunus flexuosus has been found to be very common in the littoral zone of the Atlantic water at the south-west coast of Iceland. It seems possible that P. flexuosus has only recently been introduced into Icelandic waters. The life history of P. flexuosus has been followed in Skerjafjord, near Reykjavik, in 1985–1986. The animals have a one-year life span. The females, some of which appear to produce three broods, breed mainly during June–August. Breeding females ranged in length from 18.7 to 25.7 mm and the largest brood was 72 eggs. The incubation time at c. 11°C was estimated to be ∼25 days. The daily growth rate of juveniles was estimated to be 0.16 mm in July–August and 0.05–0.07 mm in September–October. No growth occurred during the winter months of October–March.

DISTRIBUTION AND ECOLOGY OF MYSIDS IN CAPE COD BAY, MASSACHUSETTS

Seven species of mysids (Neomysis americana, Erythrops erythropthalma, Mysis stenolepis, Mysis mixta, Heteromysis formosa, Praunus flexuosus, and Meterythrops robusta) were collected from Cape Cod Bay, Massachusetts. The general ecology of the first four species is described in terms of several classificatory schemes proposed for worldwide mysid distributions.Organismal relationships to geographic, seasonal, bathymetric, bottom water temperature, and sediment characteristics are examined. Four species occurred year-round with the following seasonal peaks in abundance: N. americana (February, April, December), E. erythropthalma (January, March, December), M. mixta (March and July), M. stenolepis (January and August). Based on bathymetric and sedimentary relationships the species tend to occur in pairs. Neomysis americana and M. stenolepis were primarily collected in shallow water (10-29 m) and from sand and clayey-silt. Erythrops erythropthalma and M. mixta occurred in deeper water (20-39 m) and on clayey-...

Effect of salinity acclimation on osmoregulation inCrangon crangonandPraunus flexuosus

Abstract The effect of acclimation to low or high salinity on the osmoregulatory abilities of Crangon crangon L. (Crustacea, Natantia) from two habitats (Aberdour, Scotland and Oresund, Denmark) and Praunus flexuosus (Muller) (Crustacea, Mysidacea) from Oresund, Denmark has been investigated. The effect of salinity acclimation on the salinity tolerance of Crangon was also examined. Animals acclimated for a long time to low salinity in the laboratory, or from low salinity habitats, were found to have enhanced hyperosmotic regulation when exposed to low salinities. Animals acclimated for a long time to high salinity in the laboratory, or from a high salinity habitat, were found to have enhanced hypo-osmotic regulation when exposed to high salinities. Acclimation to low salinity also extended the survival time in low salinities, and high salinity acclimation extended the survival time in high salinities. It is shown that the difference in the osmoregulatory abilities of populations from different habitats ar...

THE HEART ULTRASTRUCTURE OF PRAUNUS FLEXUOSUS (MULLER) AND MYSIS RELICTA (LOVEN) (CRUSTACEA, MYSIDACEA)

ABSTRACT The hearts of Praunus flexuosus and Mysis relicta have single layered myocardia and single layered epicardia. The epicardia of the two mysids are identical. The myofibers are polarized in M. relicta only. There are no variations in the membrane systems. T tubules are mainly found at the H level; those at the Z level are less conspicuous. Couplings, internal and peripheral, are located at the H level. The sarcoplasmic reticulum is well-developed and continuous over the Z band. Nerve terminals are described.

The measurement of glutamate dehydrogenase activity in Praunus flexuosus and its role in the regulation of ammonium excretion

Abstract 1. 1. A strong correlation (r2 = 0.916) was found between glutamate dehydrogenase (GDH) activity and ammonium excretion in Praunus flexuosus suggesting a key regulatory role for this enzyme. 2. 2. The high level of GDH activity found in this mysid was sufficient to account for all the ammonium excreted. 3. 3. Activator-inhibitor studies imply that GDH may regulate energy production and growth, in addition to ammonium excretion. 4. 4. The GDH assay presented here appears useful as a technique for quantifying zooplankton ammonium excretion impacts in the world oceans.

Some effects of salinity and temperature on the osmotic and ionic regulation ofPraunus flexuosus(Crustacea, Mysidacea) from Isefjord

Abstract The salinity tolerance, osmotic regulation and ionic regulation of the mysid crustacean, Praunus flexuosus, collected at the Isefjord, Denmark, has been investigated over a range of salinities, and at temperatures from 5 to 20 °c for both winter and summer animals. Survival at low salinities was enhanced when the animals were kept at low temperatures, and this enhancement was especially pronounced in animals collected in winter. A clear pattern of hyper/hypo-osmotic regulation was found, but no effect of season or temperature on the osmotic concentration was observed. The blood concentration of Isefjord animals was significantly lower at any given salinity than that of previously srudied animals from Loch Etive, Scotland. This reduction is considered to be due to long-term acclimation, and the findings are compared with other crustacea where studies have been made on distinct populations. The blood concentrations of sodium, potassium, calcium, magnesium and chloride were determined at three salin...

Seasonal Changes in Density, Composition and Reproductive Biology of Crustacean Populations in the Severn Estuary

Changes in the abundance and composition of crustacean populations in the plankton of the Severn Estuary (England) were followed for 25 consecutive months (1973-1975). The collections were made primarily near shore from the cooling intake of the Oldbury nuclear power station. Neomysis integer overwintered at comparatively low densities with all specimens measuring more than 5 mm in length. Inshore swarms of this species were detected early in the summer and most females carried either eggs or embryos. Praunus flexuosus invariably occurred less frequently than N. integer. During the summer, inshore aggregations of adults were probably formed and, although large numbers of berried females were observed at this time, the release of young possibly never occurred in the Oldbury region. Eurytemora affinis was observed only during periods of low salinity in winter with maximum reproductive activity taking place in December. The highest density of Eurydice pulchra occurred early in the summer due to the recruitment of young while, at other times, this species remained comparatively rare. The same pattern was observed in Gammarus salinus but since only a few females carried eggs at any one time reproduction must take place outside of the study area. Crangon crangon maintained greatest numbers during the summer and fall, being almost absent during part of the winter. The growth rate, size at maturity and period of reproductive activity of this species differed from earlier accounts on Severn populations.

The fine structure of the compound eyes of mysids (crustacea: mysidacea).

The ultrastructure of the compound eyes of five species of mysids (Crustacea: Mysidacea), Praunus flexuosus, Siriella norvegica, Mysidopsis gibbosa, Neomysis integer and Erythrops serrata, is described. The ommatidia are constructed on a common plan, but there are considerable differences in detail. Common features include the arrangement of the cornea, crystalline cone and the basement membrane. The number of retinular cells differ: in Neomysis and Erythrops there are seven, whereas in the other species there are eight, the eighth cell forming a distal rhabdom, which consequently is lacking in the ommatidia of Neomysis and Erythrops. Another difference is the epirhabdom, which is lacking in Erythrops, but present in the other species. The epirhabdom is an extracellular structure, probably serving as a dioptric element. The pigment arrangement is similar in the first four species. The pigment shield consists of the distal pigment, distal reflecting pigment, proximal pigment (in the retinular cells) and the proximal reflecting pigment. The distal and proximal pigments are dark screening pigments. In addition to these, there are basal red pigment cells, which are mainly located below the basement membrane. In Erythrops there are three kinds of pigment cells: distal pigment cells, distal reflecting pigment cells and basal red pigment cells. Besides the basal red pigment cells, the distal pigment cells contain red pigment granules.

The proximate and fatty acid composition of some estuarine crustaceans

The lipid content of Crangon crangon, Gammarus salinus, Neomysis integer, Praunus flexuosus and Orchestia gammarella collected from the reservoir of the Oldbury power station on the Severn Estuary ranged from 25 to 33% of the dry weight over the course of one year while the corresponding values for ash averaged 15–24%. Water accounted for 75–80% of the wet weight except in the case of O. gammarella (70%). The unusually high lipid values were probably connected with the highly favourable environmental conditions in the reservoir while both the size and reproductive condition of the animals were also important in determining the size of the lipid store. Phospholipids accounted for as much as 33% of the total lipid in C. crangon and for as little as 24% in N. integer and P. flexuosus. The predominant fatty acids in both the neutral and phospholipids of all species were 16:0, 18:1, 20:5 and 22:6.

The Mechanism of Statocyst Operation in the Mysid Shrimp Praunus Flexuosus

ABSTRACT Analysis of the compensatory eyestalk responses of mysid shrimps before and after the removal of one statocyst has revealed, in the light of statocyst anatomy, that the two statocysts co-operate in their action at all angles of body tilt.Many features of statocyst operation in mysids are shared by decapod crustaceans, but an important difference exists between the geometries of the two statocyst systems. The consequences of this difference highlight the structural constraints on systems of statolithic gravity receptors for which shear magnitude is the adequate stimulus.

The Optokinetic Responses of the Mysid Shrimp Praunus Flexuosus

ABSTRACT The optokinetic responses of the mysid shrimp Praunus flexuosus in the horizontal and vertical-transverse planes have been studied. The horizontal optokinetic nystagmus is fragmented, and eyestalk following speed is a function of stimulus speed. The vertical optokinetic response is not a nystagmus, but involves maintained eyestalk, deviations. These deviations, and eyestalk following speed are both functions of stimulus speed. The velocity gain (eye speed/slip speed) of the responses in both dimensions has a constant value between drum speed z°/sec and 40°/sec, which suggests that they subserve a simple rheotactic function. The vertical optokinetic response is modulated by statocyst input, and possible mechanisms underlying this effect are discussed.

The Control of Eyestalk Movements in the Mysid Shrimp Praunus Flexuosus

ABSTRACT The compensatory eyestalk movements of intact and statocystless mysid shrimps Praunus flexuosus have been measured under a variety of light conditions. The results indicate that the statocyst organs in the urppods are the major gravity receptors, and that they are both necessary and sufficient to produce sinusoidal compensatory eyestalk movements. The addition of visual cues (vertical light beam, optokinetic stimuli) modifies the eyestalk response to some extent, but does not alter its general form. When the statocysts are removed, however, light stimuli become important orientational cues, and the eyestalks perform a tracking response which is considered to be the experimental counterpart of the dorsal light reaction of the free-swimming animal.

The embryonic development of the avoidance reflex of Neomysis americana and Praunus flexuosus (Crustacea: Mysidacea)

The embryonic antecedents of the avoidance reflex of both Praunus flexuosus and Neomysis americana appear to be spontaneous before they become reflexive. The spontaneous flinches of the naupliar embryo appear to become the twitches of the post-naupliar embryo, which in turn become the avoidance reflexes of the juvenile. The post-naupliar twitches are also apparently spontaneous at first, but they occur increasingly often in response to tactile stimulation as post-naupliar development progresses. Though each embryonic moult results in a sudden emergence of greater complexity of embryonic activity there is gradual elaboration of the activity between such moults.

Some Effects of Salinity on the Mysid Praunus Flexuosus

The population dynamics of the mysid crustacean Praunus flexuosus have been studied at Ardmaddy Bay, Loch Etive. A salinity tolerance range of 2–33‰ has been demonstrated, over which the body tissues experience the range 11–28‰. Comparison is made between the osmoregulatory capacity of Praunus flexuosus and the closely related Neomysis integer.

The Biology of Praunus Flexuosus and P. Neglectus [Crustacea, Mysidacea

The biology of Praunus flexuosus (Müller) is closely similar to that of P. neglectus (G. O. Sars). In both species the over-wintering population matures and breeds in the early spring and summer to produce a spring generation of young which are evident in the population in May or June. The members of the over-wintering population die off in July or August. Some members of the spring generation become sexually mature and breed in the early autumn. The progeny of this autumn breeding, along with the bulk of the spring generation, form the over-wintering population. These species are omnivorous feeding on animal and plant debris and also preying on small crustaceans, very frequently harpacticid copepods. The maximum brood size found in P. flexuosus was 63 and in P. neglectus was 81. The biology of the populations on the west coast of Scotland is briefly compared with that of populations in Port Erin, Isle of Man, in Norway and at Roscoff.