Planktivorous fish positively select Daphnia bearing advanced embryos

2020 ◽  
Vol 71 (4) ◽  
pp. 505 ◽  
Author(s):  
Jana Zemanová ◽  
Michal Šorf ◽  
Josef Hejzlar ◽  
Vanda Šorfová ◽  
Jaroslav Vrba
Keyword(s):  
Body Length ◽  
Life History Traits ◽  
Developmental Stages ◽  
Fish Predation ◽  
Lower Proportion ◽  
Planktivorous Fish ◽  
Top Down ◽  
Selective Elimination ◽  
Fish Predators ◽  
Food Conditions

The top-down effect of fish predation on reproduction success of Daphnia females was investigated in an outdoor mesocosm experiment with natural (oligotrophic) food conditions. The planktivorous fish, sunbleak (Leucaspius delineatus, 4.9 individuals m–3) was introduced into a half of mesocosms after the first sampling of zooplankton to compare daphnid life-history traits with and without fish predators. Our results showed selective fish predation on the daphnid females with advanced developmental stages of embryos. The Daphnia populations exposed to fish exhibited a lower proportion of females with advanced embryos over those with earlier embryonal stages. Fish predators obviously were attracted to more visible females bearing larger embryos, with well-developed pigmented eyes. Simultaneously, we found a smaller daphnid body length in the mesocosms with fish than in those that were fishless. However, the daphnid clutch size did not reflect their body-length pattern and, surprisingly, decreased regardless of fish presence or absence since the first sampling day, probably owing to deterioration of food quality (mean seston carbon:phosphorus ratio ~238). Nevertheless, this selective elimination of the females with advanced embryos, together with the overall decrease in daphnid fitness, can strengthen the deceleration of its population growth under fish predation.

scholarly journals Fish predation on corals promotes the dispersal of coral symbionts

2020 ◽  
Author(s):  
Carsten G.B. Grupstra ◽  
Kristen M. Rabbitt ◽  
Lauren I. Howe-Kerr ◽  
Adrienne M.S. Correa
Keyword(s):  
Direct Contact ◽  
Fish Predation ◽  
Top Down ◽  
Fish Predators ◽  
Positive Effect ◽  
Symbiont Acquisition

AbstractPredators drive top-down effects that shape prey communities, but the role of predators in dispersing prey microbiomes is rarely examined. We tested whether coral-eating (corallivorous) fish disperse the single-celled dinoflagellate symbionts (family Symbiodiniaceae) of their prey. Our findings demonstrate that: (1) coral-eating fish egest feces containing live Symbiodiniaceae at densities up to seven orders of magnitude higher than other environmental reservoirs such as sediments and water; (2) Symbiodiniaceae communities in the feces of most corallivores are compositionally similar to those in corals; (3) some obligate corallivore species release over 100 million Symbiodiniaceae cells per 100 m2 per day; and (4) after being egested, corallivore feces often come in direct contact with coral colonies (potential hosts for Symbiodiniaceae). These findings suggest that fish predators can play an important role in symbiont acquisition by corals; such predators may have a previously unrecognized, indirect positive effect on prey health.

scholarly journals Seasonal maturation of Glypthelmins vitellinophilum (Trematoda: Digenea) in Lysapsus limellus (Anura: Pseudidae) from an Argentinian subtropical permanent pond

2006 ◽  
Vol 66 (1a) ◽  
pp. 85-93 ◽  
Author(s):  
M. I. Hamann
Keyword(s):  
Body Length ◽  
Developmental Stages ◽  
Small Body ◽  
Stage Iv ◽  
The Body ◽  
Climatic Fluctuations ◽  
Parasite Stage ◽  
Permanent Pond ◽  
Body Sizes ◽  
The Relationship

From December 1995 to November 2000, the seasonal maturation of Glypthelmins vitellinophilum Dobbin, 1958, in its definitive host, the frog Lysapsus limellus Cope, 1862, was studied in a subtropical permanent pond in northeastern Argentina. The objectives of this study were: 1) to determine the infrapopulation dynamics of the parasite, analyzing the seasonal maturation cycle throughout the years; and 2) to examine the relationship between the intensity of trematode infection in different developmental stages (recruitment, growth and maturation) and the host's body length. Of a total of 1,400 frogs examined over 60 months (5 years), 38% were found to be infected with G. vitellinophilum, and the intensity of infection was 1-15 trematodes per frog. Specimens of G. vitellinophilum were present in L. limellus throughout the years, but did not show a pronounced seasonal maturation cycle. Possible reasons for these findings are discussed with reference to climatic fluctuations and biotic factors. The infective period of the parasite (stage I) occurred in summer, autumn and spring, coinciding with the time each frog cohort appeared. These infections were found principally in small body sizes (classes 1 and 2) of L. limellus. Juvenile and nongravid specimens of worms (stage II and III) were found in frogs of different body sizes throughout the period of investigation. Gravid specimens of the parasite (stage IV) were generally recorded in autumn, winter and spring, mainly in the bodies of larger frogs. The body length of Trematodes in stages I and IV was significantly and positively correlated with that of the frogs.

Brain size evolution in anurans: a review

2019 ◽  
Vol 69 (3) ◽  
pp. 265-279 ◽  
Author(s):  
Chun Lan Mai ◽  
Wen Bo Liao
Keyword(s):  
Sexual Selection ◽  
Life History ◽  
Life History Traits ◽  
Developmental Stages ◽  
Brain Size ◽  
Ecological Factors ◽  
Brain Regions ◽  
Sperm Length ◽  
Testis Size ◽  
Size Evolution

Abstract Selection pressure is an important force in shaping the evolution of vertebrate brain size among populations within species as well as between species. The evolution of brain size is tightly linked to natural and sexual selection, and life-history traits. In particular, increased environmental stress, intensity of sexual selection, and slower life history usually result in enlarged brains. However, although previous studies have addressed the causes of brain size evolution, no systematic reviews have been conducted to explain brain size in anurans. Here, we review whether brain size evolution supports the cognitive buffer hypothesis (CBH), the expensive tissue hypothesis (ETH), or the developmental cost hypothesis (DCH) by analyzing the intraspecific and/or interspecific patterns in brain size and brain regions (i.e., olfactory nerves, olfactory bulbs, telencephalon, optic tectum, and cerebellum) associated with ecological factors (habitat, diet and predator risk), sexual selection intensity, life-history traits (age at sexual maturity, mean age, longevity, clutch size and egg size, testis size and sperm length), and other energetic organs. Our findings suggest that brain size evolution in anurans supports the CBH, ETH or DCH. We also suggest future directions for studying the relationships between brain size evolution and crypsis (i.e., ordinary mucous glands in the skin), and food alteration in different developmental stages.

Fish predation effects on body length of planktonic cladocerans and copepods in Chilean lakes

Crustaceana ◽  
2015 ◽  
Vol 88 (10-11) ◽  
pp. 1193-1199 ◽  
Author(s):  
Patricio De los Ríos-Escalante
Keyword(s):  
Body Length ◽  
Zooplankton Community ◽  
Fish Predation ◽  
Total Body Length ◽  
Calanoid Copepods ◽  
Main Prey ◽  
Species Numbers ◽  
Zooplankton Size ◽  
Predation Effects ◽  
Total Body

The zooplankton assemblages in Chilean lakes are characterized by their markedly low species numbers and dominance of calanoid copepods. Nevertheless, the effects of zooplanktivorous fish predation on zooplankton size in these communities have not yet been studied in detail. The aim of the present study was to analyse the total length in the main groups of zooplanktonic crustaceans in Chilean lakes: Copepoda: Calanoida, and Cladocera: Daphniidae, as well as “small cladocerans” (specifically the families Bosminidae and Chydoridae). The results revealed that in the presence of fish, total body length decreased significantly for calanoid copepods, whereas for other groups that presence has no significant effect. In sites with fishes, daphniids are significantly larger in comparison with the other groups of the zooplankton community, whereas in sites without fishes calanoids are significant larger in comparison with those other groups. These results would indicate that calanoids would be the main prey for zooplanktivorous fishes in Chilean lakes. Similar results have been reported for Argentinean Patagonian lakes.

scholarly journals Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes

2013 ◽  
Vol 71 (2) ◽  
pp. 406-416 ◽  
Author(s):  
T. O. M. Reilly ◽  
H. M. Fraser ◽  
R. J. Fryer ◽  
J. Clarke ◽  
S. P. R. Greenstreet
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Levels ◽  
Top Down ◽  
Bottom Up ◽  
Control Processes ◽  
Top Predators ◽  
Environmental Status ◽  
Fish Predators ◽  
Firth Of Forth

Abstract Reilly, T. O. M., Fraser, H. M., Fryer, R. J., Clarke, J., and Greenstreet, S. P. R. 2014. Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes. – ICES Journal of Marine Science, 71: 406–416. Proposed indicators for the Marine Strategy Framework Directive (MSFD) food webs Descriptor focus on structural elements of food webs, and in particular on the abundance and productivity of top predators. However, the inferences that can be drawn from such indicators depend on whether or not the predators are “bottom-up limited” by the availability of their prey. Many seabird populations appear to be “bottom-up limited” so that variation in their reproductive success and/or abundance reflects changes in lower trophic levels. Here we find that gadoid fish predators off the Firth of Forth, southeast Scotland, do not appear to be “bottom-up limited” by the biomass of their main prey, 0-group sandeels; gadoid biomass and feeding performance was independent of sandeel biomass. Variability in food web indicators based on these gadoid predators seems to impart little insight into underlying processes occurring at lower trophic levels in the local food web. The implications of this in terms of how the currently proposed MSFD food web indicators should be used and interpreted are considered, and the ramifications in terms of setting targets representing good environmental status for both fish and seabird communities are discussed.

scholarly journals A review of bottom-up vs. top-down control of sponges on Caribbean fore-reefs: what’s old, what’s new, and future directions

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4343 ◽  
Author(s):  
Joseph R. Pawlik ◽  
Tse-Lynn Loh ◽  
Steven E. McMurray
Keyword(s):  
Community Structure ◽  
Past Research ◽  
Fish Predation ◽  
Sponge Species ◽  
Top Down ◽  
Bottom Up ◽  
Fore Reef ◽  
The Past ◽  
The Impact ◽  
Hawksbill Turtles

Interest in the ecology of sponges on coral reefs has grown in recent years with mounting evidence that sponges are becoming dominant members of reef communities, particularly in the Caribbean. New estimates of water column processing by sponge pumping activities combined with discoveries related to carbon and nutrient cycling have led to novel hypotheses about the role of sponges in reef ecosystem function. Among these developments, a debate has emerged about the relative effects of bottom-up (food availability) and top-down (predation) control on the community of sponges on Caribbean fore-reefs. In this review, we evaluate the impact of the latest findings on the debate, as well as provide new insights based on older citations. Recent studies that employed different research methods have demonstrated that dissolved organic carbon (DOC) and detritus are the principal sources of food for a growing list of sponge species, challenging the idea that the relative availability of living picoplankton is the sole proxy for sponge growth or abundance. New reports have confirmed earlier findings that reef macroalgae release labile DOC available for sponge nutrition. Evidence for top-down control of sponge community structure by fish predation is further supported by gut content studies and historical population estimates of hawksbill turtles, which likely had a much greater impact on relative sponge abundances on Caribbean reefs of the past. Implicit to investigations designed to address the bottom-up vs. top-down debate are appropriate studies of Caribbean fore-reef environments, where benthic communities are relatively homogeneous and terrestrial influences and abiotic effects are minimized. One recent study designed to test both aspects of the debate did so using experiments conducted entirely in shallow lagoonal habitats dominated by mangroves and seagrass beds. The top-down results from this study are reinterpreted as supporting past research demonstrating predator preferences for sponge species that are abundant in these lagoonal habitats, but grazed away in fore-reef habitats. We conclude that sponge communities on Caribbean fore-reefs of the past and present are largely structured by predation, and offer new directions for research, such as determining the environmental conditions under which sponges may be food-limited (e.g., deep sea, lagoonal habitats) and monitoring changes in sponge community structure as populations of hawksbill turtles rebound.

scholarly journals Echoes of the hunt? An inter-continental comparison of patterns of growth and determinants of size of brown bears in Canada and Sweden.

2022 ◽  
Author(s):  
Andreas Zedrosser ◽  
Marc CAttet ◽  
Jon Swenson ◽  
Gordon Stenhouse
Keyword(s):  
Population Density ◽  
Body Length ◽  
Life Histories ◽  
Life History Traits ◽  
Reproductive Investment ◽  
Negative Effects ◽  
Brown Bears ◽  
Positive Effects ◽  
The Past ◽  
The Difference

Comparing life history traits among populations that have been separated genetically for several hundred thousand years, but live in similar habitats on different continents, may help us understand how ecological and anthropomorphic factors shape life histories. We compared patterns of growth in body length and mass, and the influence of population density, habitat quality (NDVI), and reproduction on age-specific length and mass of male and female brown bears between Alberta, Canada, and Sweden. We found that Swedish females were significantly smaller in both length and mass than Alberta females. Swedish females also reached primiparity earlier and at a smaller mass and length. However, there were no continental differences in the patterns of growth in males. We found strong positive effects of NDVI, but only weak negative effects of population density on female mass and length in both areas. Generally, especially mass of Alberta females was more strongly affected by NDVI and density than for Swedish females. Reproduction had stronger negative effects on female mass in Alberta than in Sweden. We found no effects of NDVI and population density on male mass and body length in both areas. The larger variation in female growth and size between the areas, in contrast to males, may be related to differences in female reproductive investment due to differences in population trends, i.e., earlier reproduction in increasing populations or populations below carrying capacity, or to different selection pressures in the past, potentially due to human persecution. Swedish females exhibited characteristics typical of increasing populations, whereas Alberta females exhibited characteristics typical of stable or decreasing populations. The difference in reproduction investment means that Swedish bears can be harvested at higher rates, whereas Alberta bears must be managed more conservatively.

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