Fish predation, cannibalism, and larval development in the dragonfly Epitheca cynosura

1997 ◽  
Vol 75 (5) ◽  
pp. 687-696 ◽  
Author(s):  
Debra B. Claus-Walker ◽  
Philip H. Crowley ◽  
Frank Johansson
Keyword(s):  
Laboratory Experiments ◽  
Size Variation ◽  
Fish Predation ◽  
Larval Survival ◽  
Rapid Convergence ◽  
Larval Size ◽  
Natural Systems ◽  
Behavioral Observations ◽  
Survival And Development ◽  
Mean Size

We manipulated the risk of fish predation and cannibalism in semi-field and laboratory experiments with larvae of the dragonfly Epitheca cynosura. Results of a 22-week semi-field experiment showed that larvae from different densities were indistinguishable in mean size by the end of the experiment, but that individuals from low densities were larger until week 12. Larvae from low densities varied less in size than did those from high densities. Larvae showed rapid convergence of densities in the absence of fish. Fish predation also generated rapid convergence of densities. The presence of fish initially reduced larval size variation. There was a significant trend for the presence of fish scent to increase larval survival at low larval densities over survival in the absence of fish. Behavioral observations in the laboratory supported the results of the semi-field study in that (i) dragonfly larvae reduced their activity under daytime conditions, (ii) the presence of large larvae caused small larvae to increase their hiding inside a refuge and inhibited their crawling while exposed, (iii) small larvae ate fewer prey in the presence of fish. The results of our study suggest that the interaction between intra- and inter-specific predation risk may prove to be important for survival and development of animals in natural systems.

Effects of temperature and photoperiod on larval size and survivorship of a burrowing mayfly (Ephemeroptera, Ephemeridae)

1992 ◽  
Vol 70 (2) ◽  
pp. 256-263 ◽  
Author(s):  
Lynda D. Corkum ◽  
Elizabeth C. Hanes
Keyword(s):  
Size Variation ◽  
Larval Survival ◽  
Time Intervals ◽  
Larval Size ◽  
Detroit River ◽  
Naturally Occurring ◽  
Different Temperatures ◽  
Effects Of Temperature ◽  
D 12 ◽  
Hexagenia Limbata

There is great size variation in naturally occurring and laboratory-reared populations of larvae of Hexagenia species. We investigated differences in mean larval size and survivorship of Hexagenia limbata and Hexagenia rigida reared at different temperatures (12, 17, and 22 °C) and photoperiods (24 h L, 24 h D, 12 h L: 12 h D) over two time intervals (60 and 120 d) in the laboratory. Owing to space limitations, two sets of replicates (3 replicates per set) were conducted in sequence for the 60-d trial. Larvae were hatched from eggs collected from imagoes at the Detroit River near Windsor, Ontario, and stored at 8 °C. Of the factors examined, temperature alone influenced larval size after 60 d of growth. None of the factors had any significant effect on larval survival after 60 d. Larvae from the second 60-d replicate set (hatched from eggs incubated for 75 d longer than the first set) were larger and exhibited lower survivorship than larvae in the first set. This finding suggests that larval size may not be a good indicator of larval age, especially if eggs have been exposed to low temperatures for varying periods. Temperature and its interaction with photoperiod significantly affected both size and survivorship of larvae reared for 120 d. At 22 °C, larvae reared under the 12 h L: 12 h D regime were larger than those reared under either constant light or dark conditions; no discernible trend in photoperiod was evident at the lower temperatures. Larval survivorship was lowest for treatments exhibiting conflicting environmental cues (12 °C and 24 h L, and 22 °C and 24 h D).

Capture of conspecific planktonic larvae by the suspension-feeding gastropod Crepipatella peruviana: association between adult and larval size

2021 ◽  
Vol 87 (1) ◽  
Author(s):  
G A Rivera-Figueroa ◽  
J A Büchner-Miranda ◽  
L P Salas-Yanquin ◽  
J A Montory ◽  
V M Cubillos ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Larval Mortality ◽  
Feeding Preference ◽  
The Other ◽  
Suspension Feeding ◽  
Adult Size ◽  
Free Living ◽  
Larval Size ◽  
Suspension Feeders ◽  
Planktonic Larvae

ABSTRACT Free-living, planktonic larvae can be vulnerable to capture and ingestion by adult suspension-feeders. This is particularly the case for larvae that settle gregariously in benthic environments where suspension-feeders occur at high densities. Larvae of gregarious suspension-feeding species are at particularly high risk, as adults of their own species often serve as cues for metamorphosis. We conducted laboratory experiments to assess the extent to which adults of the suspension-feeding caenogastropod Crepipatella peruviana would capture and ingest their own larvae. Experiments were conducted with adults of different sizes, with larvae of different ages and sizes, and in the presence or absence of phytoplankton. Adults captured larvae in all experiments. The presence of microalgae in the water did not influence the extent of larval capture. On average, 39% of larvae were captured during the 3-h feeding periods, regardless of adult size. However, up to 34% of the larvae that were captured on the gill were later discarded as pseudofaeces; the other 64% were ingested. The extent of capture by adults was not related to adult size, or to larval size and, thus, to larval age. Our results suggest that the filtration of congeneric larvae by adult C. peruviana is a result of accidental capture rather than a deliberate feeding preference. Such ingestion could, however, still be an important source of larval mortality, especially when the advanced larvae of this species are searching for a suitable substrate for metamorphosis.

Male-biased sex ratio in Argulus canadensis Wilson, 1916 (Crustacea: Branchiura) ectoparasitic on sticklebacks

1989 ◽  
Vol 67 (8) ◽  
pp. 2078-2080 ◽  
Author(s):  
Robert Poulin ◽  
Gerard J. FitzGerald
Keyword(s):  
Salt Marsh ◽  
Sex Ratio ◽  
Laboratory Experiments ◽  
Fish Predation ◽  
Reproductive Behaviour ◽  
Egg Deposition ◽  
Alternative Hypotheses ◽  
Biased Sex Ratio ◽  
The Difference ◽  
Fish Hosts

Females of the ectoparasitic crustacean Argulus canadensis must leave their fish hosts at least temporarily to deposit their eggs on the substrate. To test the hypothesis that this difference in reproductive behaviour between the two sexes could result in male-biased sex ratios on their stickleback hosts, we sampled sticklebacks in tide pools of a Quebec salt marsh from early July to early September 1986. During this period, fish harboured significantly more male than female A. canadensis. Laboratory experiments were done to test two alternative hypotheses offered to explain this biased sex ratio. The first hypothesis was that male A. canadensis were more successful than females in attacking their stickleback hosts; however, we found no differences in attack success on their hosts between the two parasite sexes. The second hypothesis was that sticklebacks ate more female than male A. canadensis. Although males were less vulnerable to fish predation than females, the difference was not significant. We conclude that sexual differences in reproductive behaviour, i.e., egg deposition behaviour of females, can account for the male-biased sex ratio of A. canadensis on sticklebacks.

An individual-based analysis of the variability of eggs and their newly hatched larvae of Atlantic cod (Gadus morhua) on the Scotian Shelf

1995 ◽  
Vol 52 (5) ◽  
pp. 1083-1093 ◽  
Author(s):  
Thomas J. Miller ◽  
Tomasz Herra ◽  
William C. Leggett
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Seasonal Pattern ◽  
Size Variation ◽  
Seasonal Temperature ◽  
Scotian Shelf ◽  
Larval Size ◽  
Newly Hatched Larvae ◽  
Shelf Region ◽  
Egg Diameter

We assessed the seasonal pattern of size variation in cod eggs on the Scotian Shelf region of the Northwest Atlantic during the period March 1991–May 1993. Cod eggs were present from October to May during the surveys. Spawning was not strongly bimodal. There was a dominant autumn peak, in contrast to the historically dominant spring spawning. Egg diameter varied seasonally. Seasonal temperature patterns explained 52% of the variation in egg diameter. By incubating the eggs on-board ship, we also assessed the seasonality of the standard length (SL) of larvae that hatched from these eggs. Larval SL also varied seasonally. Egg diameter and SL were significantly correlated, but the correlation was weak (r2 = 0.3). However, the strength of correlation was consistent with laboratory estimates based on individual data. The results suggest that previous estimates of the egg size – larval size correlations are inflated. Temperature exerted a significant effect on both egg diameter and larval size, and is hypothesized to be the agent responsible for the observed seasonal variation.

scholarly journals Analysis of the drainage density of experimental and modelled tidal networks

2014 ◽  
Vol 2 (1) ◽  
pp. 105-116 ◽  
Author(s):  
Z. Zhou ◽  
L. Stefanon ◽  
M. Olabarrieta ◽  
A. D'Alpaos ◽  
L. Carniello ◽  
...  
Keyword(s):  
Probability Distribution ◽  
Laboratory Experiments ◽  
Venice Lagoon ◽  
Drainage Density ◽  
Exceedance Probability ◽  
Tidal Basin ◽  
Morphological Development ◽  
Tidal Prism ◽  
Natural Systems ◽  
Exponential Trend

Abstract. Based on controlled laboratory experiments, we numerically simulate the initiation and long-term evolution of back-barrier tidal networks in micro-tidal and meso-tidal conditions. The simulated pattern formation is comparable to the morphological growth observed in the laboratory, which is characterised by relatively rapid initiation and slower adjustment towards an equilibrium state. The simulated velocity field is in agreement with natural reference systems such as the micro-tidal Venice Lagoon and the meso-tidal Wadden Sea. Special attention is given to the concept of drainage density, which is measured on the basis of the exceedance probability distribution of the unchannelled flow lengths. Model results indicate that the exceedance probability distribution is characterised by an approximately exponential trend, similar to the results of laboratory experiments and observations in natural systems. The drainage density increases greatly during the initial phase of tidal network development, while it slows down when the system approaches equilibrium. Due to the larger tidal prism, the tidal basin has a larger drainage density for the meso-tidal condition (after the same amount of time) than the micro-tidal case. In both micro-tidal and meso-tidal simulations, it is found that there is an initial rapid increase of the tidal prism which soon reaches a relatively steady value (after approximately 40 yr), while the drainage density adjusts more slowly. In agreement with the laboratory experiments, the initial bottom perturbations play an important role in determining the morphological development and hence the exceedance probability distribution of the unchannelled flow lengths. Overall, our study indicates an agreement of the geometric characteristics between the numerical and experimental tidal networks.

scholarly journals Limiting stress states in granular avalanches

1998 ◽  
Vol 26 ◽  
pp. 272-276 ◽  
Author(s):  
Y.C. Tai ◽  
J.M.N.T. Gray
Keyword(s):  
Stress State ◽  
Numerical Methods ◽  
Granular Material ◽  
Laboratory Experiments ◽  
Complex Geometry ◽  
The Other ◽  
Two Dimensional ◽  
Singular Surfaces ◽  
Rapid Convergence ◽  
Stress States

The Savage-Hutter theory for granular avalanches assumes that the granular material is in either of two limiting stress states, depending on whether the motion is convergent or divergent. At transitions between convergent and divergent regions, a jump in stress occurs, which necessarily implies that there is a jump in the avalanche velocity and/or its thickness. In this paper, a regularizaron scheme is used, which smoothly switches from one stress state to the other, and avoids the generation of such singular surfaces. The resulting algorithm is more stable than previous numerical methods but shocks can still occur during rapid convergence in the run-out zone. Results are presented from two-dimensional calculations on complex geometry which illustrate that some necking features observed in laboratory experiments can be explained by the regularized Savage-Hutter model.

Effects of Temperature and Humidity on the Rust-Red Flour Beetle, Tribolium-Castaneum (Herbst) (Coleoptera, Tenebrionidae), in Wheat-Grain

1987 ◽  
Vol 35 (1) ◽  
pp. 43 ◽  
Author(s):  
GG White
Keyword(s):  
Tribolium Castaneum ◽  
Larval Survival ◽  
Population Increase ◽  
Effect Of Temperature ◽  
Wheat Grain ◽  
Mathematical Functions ◽  
Temperature And Humidity ◽  
Survival And Development ◽  
Effects Of Temperature ◽  
Coleoptera Tenebrionidae

Rates of survival and development of the immature stages of Tribolium castaneum (Herbst) (Coleoptera : Tenebrionidae) were determined in wheat grain at constant temperatures from 20 to 37.5�C and constant relative humidities from 25 to 65%. The rates for eggs and pupae were similar to those previously published for T. castaneum in flour, but larval development was slower and mortality greater, except at low temperature and high humidity. The effect of temperature and humidity on rates of fertility and oviposition in young adults were also determined in wheat grain. The patterns of effects of temperature and humidity on oviposition were similar to those previously published for T. castaneum in flour, but the maximum observed oviposition rate was lower. Fertility was significantly reduced when densities of adults were greater than one pair per 250 g. Mathematical functions were fitted to data from the present and previous studies on age-specific survival and fecundity of adults; population growth rate statistics were calculated from life-table parameters defined by these functions. Under optimal conditions within the range of the present study (35�C, 65% RH), the innate capacity for increase rm was 0.84 per week. The limits for population increase, where rm is zero, were largely determined by.the limits for larval survival, which were approximately 35% RH, and 20-22�C at the lower limit and 40�C at the upper limit.

Effects of density and food limitation on size variation and mortality of larval Hexagenia rigida (Ephemeroptera: Ephemeridae)

1992 ◽  
Vol 70 (9) ◽  
pp. 1824-1832 ◽  
Author(s):  
Elizabeth C. Hanes ◽  
Jan J. H. Ciborowski
Keyword(s):  
Food Limitation ◽  
Larval Growth ◽  
Natural Populations ◽  
Size Variation ◽  
Food Level ◽  
Larval Size ◽  
Detroit River ◽  
Frequency Distributions ◽  
Exogenous Factors ◽  
Growth Differences

Natural populations of the burrowing mayfly belonging to the genus Hexagenia are characterized by unusually broad size-frequency distributions. Environmental features are often invoked to explain among-populations growth differences. We used a 4 × 4 factorial design to investigate differences in mean larval size and mortality of Hexagenia reared at different densities and food levels over four time intervals (30, 60, 90, and 120 d) in the laboratory. Larvae were hatched from eggs collected from imagoes at the Detroit River near Windsor, Ontario. Although neither density nor food limitation influenced larval growth at either 30 or 60 d growth, the number of days required for eggs to hatch did significantly influence larval growth at this time. At 30 d growth, larvae that hatched after 6 d incubation were significantly smaller than larvae that required an additional day to hatch (7 d). At both 30 and 60 d, larvae that hatched after 6 d incubation had lower mortality than larvae that hatched after 7 d. At 90 and 120 d growth, density and food significantly influenced larval size and mortality. Larvae reared at low density and with a high food level attained the largest size. Mortality increased under stressed conditions (high density and (or) low food level). Since endogenous features (day of hatch) can be important early in larval development (at 30 or 60 d), such features may contribute to the outcome of competitive events that occur later in development (at 90 or 120 d), when exogenous factors (density and food) become significant.

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