ENCOUNTER FREQUENCY DOES NOT PREDICT PREDATION FREQUENCY IN TROPICAL DEAD-SHELL ASSEMBLAGES

Palaios ◽  
2015 ◽  
Vol 30 (12) ◽  
pp. 818-826 ◽  
Author(s):  
JULIETA C. MARTINELLI ◽  
MATTHEW A. KOSNIK ◽  
JOSHUA S. MADIN
Keyword(s):  
Prey Species ◽  
Size Range ◽  
Prey Size ◽  
Species Level ◽  
Soft Sediment ◽  
Ecological Communities ◽  
Drilling Predation ◽  
Drill Holes ◽  
Molluscan Assemblage ◽  
Shed Light

Abstract Predation is frequently suggested to be a key biotic process that can shape ecological communities and drive coevolution. The premise behind these hypotheses is that predators select prey to ensure maximum gain per unit effort; for example, by selecting species that are more abundant or accessible. In this study, we tested for predator selectivity in a tropical molluscan assemblage by quantifying the influence of relative abundance (encounter frequency) on predation frequencies. We collected macromollusks (> 4 mm) from 15 sites in three soft-sediment reef lagoons at One Tree Reef (southern Great Barrier Reef, Australia). Dead mollusks were counted and identified to species level (61 species, n  =  8131), and species predation frequencies were calculated as the proportion of shells with drill holes. We found that in this infauna-dominated community, levels of drilling predation were low (7.14% on average), and there was no evidence that predators selected prey based on encounter frequency. This result was consistent across prey species and lagoons. Thus, drilling predators did not specialize on more accessible prey species and were not a major cause of mortality in this modern macromollusk assemblage. Since drilling gastropods are size selective, lack of selectivity in our samples only applies to the prey size range considered. Detailed studies of prey morphological traits, as well as accounting for predator non-consumptive effects could shed light on the preferences and relevance of drilling gastropods in this soft-sediment carbonate reef assemblage.

Discerning the diets of sweep-feeding eurypterids: assessing the importance of prey size to survivorship across the Late Devonian mass extinction in a phylogenetic context

Paleobiology ◽  
2020 ◽  
pp. 1-13
Author(s):  
Emily S. Hughes ◽  
James C. Lamsdell
Keyword(s):  
Mass Extinction ◽  
Prey Species ◽  
Size Range ◽  
Prey Size ◽  
Phylogenetic Signal ◽  
Late Devonian ◽  
Evolutionary Trend ◽  
Average Spacing ◽  
Horseshoe Crabs ◽  
Mode Of Life

Abstract Eurypterids are generally considered to comprise a mixture of active nektonic to nektobenthic predators and benthic scavenger-predators exhibiting a mode of life similar to modern horseshoe crabs. However, two groups of benthic stylonurine eurypterids, the Stylonuroidea and Mycteropoidea, independently evolved modifications to the armature of their anterior appendages that have been considered adaptations toward a sweep-feeding life habit, and it has been suggested the evolution toward sweep-feeding may have permitted stylonurines to capture smaller prey species and may have been critical for the survival of mycteropoids during the Late Devonian mass extinction. There is a linear correlation between the average spacing of feeding structures and prey sizes among extant suspension feeders. Here, we extrapolate this relationship to sweep-feeding eurypterids in order to estimate the range of prey sizes that they could capture and examine prey size in a phylogenetic context to determine what role prey size played in determining survivorship during the Late Devonian. The mycteropoid Cyrtoctenus was the most specialized sweep-feeder, with comblike appendage armature capable of capturing mesoplankton out of suspension, while the majority of stylonurines possess armature corresponding to a prey size range of 1.6–52 mm, suggesting they were suited for capturing small benthic macroinvertebrates such as crustaceans, mollusks, and wormlike organisms. There is no clear phylogenetic signal to prey size distribution and no evolutionary trend toward decreasing prey sizes among Stylonurina. Rather than prey size, species survivorship during the Late Devonian was likely mediated by geographic distribution and ability to capitalize on the expanding freshwater benthos.

PATTERNS OF GASTROPOD MOLLUSK PREDATION ON BIVALVE MOLLUSKS ALONG THE UPPER TEXAS GULF COAST

2018 ◽  
Vol 70 (1) ◽  
Author(s):  
Serena J. Randolph ◽  
Alan D. Maccarone
Keyword(s):  
Shell Thickness ◽  
Prey Species ◽  
Gulf Coast ◽  
Prey Selection ◽  
Drill Hole ◽  
The United States ◽  
Hole Diameter ◽  
Bivalve Mollusks ◽  
Collection Site ◽  
Drill Holes

Abstract Predation on bivalve mollusks by gastropod mollusks is common in coastal regions of the United States; however, few previous studies have examined whether drilling gastropods exhibit prey selection. In 2016, shells with small holes drilled by as many as two gastropod predators were collected at three sites separated by 30 km along the Texas Upper Gulf Coast on the Bolivar Peninsula (29° 40′N, 94° 90′W). The likeliest predators in these waters are the southern oyster drill (Stramonita haemastoma Linnaeus 1767) and the moon snail (Neverita duplicate Say 1822). Collected shells were identified to species and measurements were taken to examine statistical relationships between predators and prey species. These measurements included drill-hole diameter, shell thickness, drill-hole completeness, number of drill attempts, and collection site. Across the three locations, 17 different species of shells with drill holes were collected; of these, we focused on the ten most abundant species (n = 277 shells). The sample showed high variation in drill-hole diameter, shell thickness, and drill-hole completeness. Both the total number of holes and mean drill-hole diameter differed significantly among prey species (ANOVA, both P < 0.0001). In addition, drill-hole diameter correlated directly with prey shell thickness (P < 0.0001). Shells whose drill holes were complete were significantly thinner than shells with incomplete holes (P < 0.0001). Mean prey shell thickness, mean drill-hole diameter, and mean number of drill holes all differed significantly by collection site (all P < 0.0001). Ecological and morphological implications related to gastropod predation on mollusks are discussed.

scholarly journals Rotational feeding in caecilians: putting a spin on the evolution of cranial design

2006 ◽  
Vol 2 (4) ◽  
pp. 485-487 ◽  
Author(s):  
G. John Measey ◽  
Anthony Herrel
Keyword(s):  
Prey Size ◽  
Evolutionary Significance ◽  
Generalist Predators ◽  
Head Width ◽  
X Ray ◽  
Video Recordings ◽  
Axis Body ◽  
Spinning Force ◽  
Shed Light

Caecilians are a poorly known group of amphibians with a highly derived skull and cranial musculature that has evolved in response to their specialized head-first burrowing lifestyle. They possess a unique jaw-closing system, which is shown to be capable of generating considerable bite forces for its head width (1.09±0.34 and 0.62±0.31 N for Schistometopum thomense and Boulengerula taitanus , respectively). However, comprehensive dietary studies indicate that there is no need for large bite forces, since most caecilians appear to be generalist predators of subterranean macrofauna. Here, we demonstrate, based on in vivo external and X-ray video recordings of animals feeding, that long-axis body rotations are used independent of prey size by these two species of caeciliid caecilians when feeding underground. Further, we show that individuals are capable of generating a substantial spinning force, which is greater than their bite force (1.35±0.26 and 1.02±0.18 N, respectively). These observations shed light on the functional and the evolutionary significance of several unique features of the cranial design in derived caecilians; spinning may allow the individuals to judge prey size and subsequently reduce oversized prey within gape limits.

scholarly journals Importance of the number emission factor of combustion-generated aerosols from nano-enabled products

2020 ◽  
Author(s):  
Tobias Hammer ◽  
Nathan Bossa ◽  
Michael Persson ◽  
Adrian Wichser ◽  
Ken Lehner ◽  
...  
Keyword(s):  
Size Range ◽  
Real Life ◽  
Polyamide 6 ◽  
Poly Lactic Acid ◽  
The Matrix ◽  
Aerosol Number Concentration ◽  
Release Data ◽  
Harmful Effects ◽  
Residual Ash ◽  
Shed Light

Abstract Accidental or open waste burning and incineration of nano-enabled products (NEPs) might lead to the release of incidental nanomaterials (NMs) into the environment resulting in harmful effects on humans. We have investigated combustion-generated NM release during accidental burning for several real-life NEPs such as paints with silica (SiO2) and spruce wood panels containing SiO2 and Fe2O3 NMs, paper with SiO2 and Fe2O3 NMs and polymeric composites with CuPhthtalocyanine NMs in poly lactic acid (PLA), polyamide 6 (PA6) and thermoplastic pol-urethane (TPU) matrices.Chemical compositions, aerosols number emission factors (nefs) and concentrations of the signature elements of the NMs of the combustion-generated aerosols were investigated. In addition, the residual ash was analyzed. The outcomes of this study shed light on how NM and matrix types influenced the properties of the released aerosols. Based on our results it was established that the combustion-generated aerosols were composed of transformed NMs with modified physical-chemical characteristics compared to the pristine NMs. In addition to the transformed NMs, there were also particles due to incomplete combustion of the matrix. Types of the pristine NMs and matrices affected the characteristics of the released aerosols. Since the hazard of the aerosols is related to the inhaled aerosol number concentration, the nef is an important parameter. Our results showed that the nefs in the size range of 5.6 to 560 nm depended strongly on the type of combusted NEP, which indicated that the NEPs could be categorized according to their potential to release aerosols in this size range when they were burnt. The generated release data facilitate the assessment of human and environmental exposure and the associated risk assessment of combustion-generated aerosols from NEPs.

Revision of the Parmelia saxatilis group in Italy based on morphological, chemical, and molecular data

Phytotaxa ◽  
2021 ◽  
Vol 512 (1) ◽  
Author(s):  
MARIA BEATRICE CASTELLANI ◽  
ELISABETTA BIANCHI ◽  
ANDREA COPPI ◽  
JURI NASCIMBENE ◽  
RENATO BENESPERI
Keyword(s):  
Genetic Diversity ◽  
Cryptic Species ◽  
Taxonomic Revision ◽  
Molecular Data ◽  
Species Level ◽  
Widespread Species ◽  
Italian Peninsula ◽  
Combined Use ◽  
Molecular Studies ◽  
Shed Light

Recent molecular studies on Parmelia revealed several new semi-cryptic and cryptic species, suggesting the existence of considerable genetic diversity within this genus that may not yet be expressed at the phenotypic level. This is the case of the two species Parmelia ernstiae and P. serrana that have been described in the P. saxatilis group from Europe and that are still poorly known in Italy. The main aim of this study is to shed light into the Italian distribution of these cryptic species on the basis of a systematic and taxonomic revision of exiccata and new specimens of the Parmelia saxatilis group collected along a biogeographical gradient through the Italian peninsula. In this revision, we combined morphological, chemical, and molecular data and evaluated their reliability for identification at the species level. Results indicate that P. saxatilis is the most widespread species and that P. ernstiae is much more widespread than previously thought. In contrast, P. serrana seems to be a rare species in Italy. Our results also indicate that the combined use of morphological and chemical data does not provide a reliable tool to discriminate the cryptic species of this group and that molecular data are thus indispensable for identification at the species level. Finally, our phylogenetic analysis supports the existence of an unrecognized diversity in parmelioid lichens that should be further investigated.

Ontogenetic niche feeding partitioning in juvenile of white sea catfish Genidens barbus in estuarine environments, southern Brazil

2008 ◽  
Vol 89 (4) ◽  
pp. 839-848 ◽  
Author(s):  
Manuel Mendoza-Carranza ◽  
João Paes Vieira
Keyword(s):  
Prey Species ◽  
White Sea ◽  
Prey Size ◽  
Age Distribution ◽  
Similarity Index ◽  
Large Fish ◽  
Southern Brazil ◽  
Predator Prey ◽  
Feeding Groups ◽  
Regression Quantile

Ontogenetic diet changes (prey species richness and size) in juveniles of white sea catfish (Genidens barbus) were tested in three southern Brazilian estuaries: Mampituba (29°12′S), Tramandaí (30°02′S), Chuí (33°44′S). Cluster analysis revealed that white sea catfish juvenile populations in the three estuaries are composed of two feeding groups. These two feeding groups are coincident with a bimodal size–age distribution of the juveniles of white sea catfish. In small catfish (5 to 10 cm TL) copepods were the most numerous prey (Chuí = 86.66%N, Tramandaí = 85.52%N and Mampituba = 52.34%N). In large catfish (10 to 20 cm TL) the most abundant and frequent prey was fish (Chuí: 73.19%N and 74.56%FO; Tramandaí: 85.92%N and 73.33%FO; Mampituba: 52.34%N and 61.54%FO). The Morisita overlap index among small and large fish was low in all estuaries; high values of Morisita's similarity index were observed among same size catfish groups. In all cases, no differences were observed among prey bio-volume curves of same size predator groups (small, F = 0.41, P = 0.65; large, F = 2.19, P = 0.11). In all estuaries, prey size increased significantly with increasing predator size. The 90th regression quantile estimated with most precision the predator–prey size relationship.

Taphonomic Bias in Analyses of Drilling Predation: Effects of Gastropod Drill Holes on Bivalve Shell Strength

Palaios ◽  
1994 ◽  
Vol 9 (4) ◽  
pp. 413 ◽  
Author(s):  
Kaustuv Roy ◽  
Daniel J. Miller ◽  
Michael Labarbera
Keyword(s):  
Drilling Predation ◽  
Predation Effects ◽  
Bivalve Shell ◽  
Drill Holes

scholarly journals Fishing destabilizes the biomass flow in the marine size spectrum

2011 ◽  
Vol 279 (1727) ◽  
pp. 284-292 ◽  
Author(s):  
M.-J. Rochet ◽  
E. Benoît
Keyword(s):  
Size Range ◽  
Prey Size ◽  
Size Spectrum ◽  
Small Fish ◽  
Marine Food Webs ◽  
Community Model ◽  
Size Diversity ◽  
Flow Oscillations ◽  
Marine Food ◽  
Fishing Impacts

Fishing impacts on marine food webs are predicted by simulations of a size spectrum community model. In this model, predation is determined by predator and prey size and abundance, and drives predator growth and prey mortality. Fishing amplifies temporal oscillations in the biomass flow. Oscillations appear at lower fishing intensity and have wider amplitude when fishing is selective (removes a narrow size range) and/or when large fish are targeted, than when fishing is more balanced (catching a larger size range) or when small fish are targeted. A novel index of size diversity is developed, and is shown to be sensitive to both fishing intensity and selectivity. To avoid unstable food web dynamics with potential harmful consequences for fisheries, limiting both fishing intensity and selectivity might be an appropriate exploitation strategy.

The Diets of Two Coexisting Species of Antechinus (Marsupialia: Dasyuridae).

1980 ◽  
Vol 7 (3) ◽  
pp. 365 ◽  
Author(s):  
S Hall
Keyword(s):  
Size Range ◽  
Prey Size ◽  
Diversity Index ◽  
Large Population ◽  
Stomach Contents ◽  
Trophic Diversity ◽  
Individual Variations ◽  
Faecal Samples ◽  
Antechinus Stuartii ◽  
Coexisting Species

An analysis of faecal samples and stomach contents of Antechinus stuartii and A. swainsonii inhabiting forest in southern Victoria revealed a large overlap in the type and size of prey items taken by these dasyurids. The frequencies of 23 prey types and 15 prey sizes in the diets of these predators were both positively correlated. Weevils (Coleoptera, Curculionidae) represented the only difference in prey types not attributed to individual variations. A. stuartii took more, and a wider size range of, weevils than did A. swainsonii; the trophic diversity index of prey types was greater for A. stuartii. The larger A. swainsonii took more prey greater than 20 mm; it took prey on the average 23% longer and 75% heavier than did A. stuartii; the trophic diversity index of prey size was greater for A. swainsonii. It is concluded that these morphologically distinct predators are exploiting the same large population of prey. They are both generalists and appear to be opportunistic feeders.

Habitats, diets, and sympatry in snakes: a study from Australia

1977 ◽  
Vol 55 (7) ◽  
pp. 1118-1128 ◽  
Author(s):  
Richard Shine
Keyword(s):  
Species Diversity ◽  
Competitive Exclusion ◽  
Prey Species ◽  
Prey Size ◽  
Empirical Work ◽  
Prey Type ◽  
Published Data ◽  
Potential Prey ◽  
Climatic Regions ◽  
Eastern Australia

Six species of elapid snakes were studied in a highlands region of eastern Australia. Major results were as follows. (1) These snakes are opportunistic feeders, relatively unselective with respect to prey type or prey size. (2) Despite this unselective feeding, over 60% of the diet (by weight) in all species consists of lizards and frogs. Published data show a preponderance of these prey types in Australian snakes as a whole, and I suggest that this is due to the scarcity of other potential prey items (especially small mammals and freshwater fish) in Australia. (3) Sympatry is less common in the elapids studied than among North American snakes in comparable climatic regions. I attribute the scarcity of sympatry among the Australian snakes to the restricted number of prey types available. This argument is supported by previous empirical work which suggests that prey species diversity determines snake species diversity. Observed prey-size differences between sympatric elapid species are consistent with the interpretation of interspecific competitive exclusion.

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