Marine chemical ecology: chemical signals and cues structure marine populations, communities, and ecosystems.
TL;DR: How chemical cues regulate critical aspects of the behavior of marine organisms from bacteria to phytoplankton to benthic invertebrates and water column fishes is reviewed.
Abstract: Chemical cues constitute much of the language of life in the sea. Our understanding of biotic interactions and their effects on marine ecosystems will advance more rapidly if this language is studied and understood. Here, I review how chemical cues regulate critical aspects of the behavior of marine organisms from bacteria to phytoplankton to benthic invertebrates and water column fishes. These chemically mediated interactions strongly affect population structure, community organization, and ecosystem function. Chemical cues determine foraging strategies, feeding choices, commensal associations, selection of mates and habitats, competitive interactions, and transfer of energy and nutrients within and among ecosystems. In numerous cases, the indirect effects of chemical signals on behavior have as much or more effect on community structure and function as the direct effects of consumers and pathogens. Chemical cues are critical for understanding marine systems, but their omnipresence and impact are inadequ...
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TL;DR: In this article , the authors investigate factors that influence asexual reproduction in the burrowing sea anemone Nematostella vectensis, which can propagate asexually by transverse fission of the body column.
Abstract: Cnidarians exhibit incredible reproductive diversity, with most capable of sexual and asexual reproduction. Here, we investigate factors that influence asexual reproduction in the burrowing sea anemone Nematostella vectensis, which can propagate asexually by transverse fission of the body column. By altering culture conditions, we demonstrate that the presence of a burrowing substrate strongly promotes transverse fission. In addition, we show that animal size does not affect fission rates, and that the plane of fission is fixed along the oral–aboral axis of the polyp. Homeobox transcription factors and components of the TGFβ, Notch, and FGF signalling pathways are differentially expressed in polyps undergoing physal pinching suggesting they are important regulators of transverse fission. Gene ontology analyses further suggest that during transverse fission the cell cycle is suppressed, and that cell adhesion and patterning mechanisms are downregulated to promote separation of the body column. Finally, we demonstrate that the rate of asexual reproduction is sensitive to population density. Collectively, these experiments provide a foundation for mechanistic studies of asexual reproduction in Nematostella, with implications for understanding the reproductive and regenerative biology of other cnidarian species.
2 citations
27 Sep 2012
TL;DR: How different species of phytoplankton cope with different threats from pelagic grazers is shown, where diatoms are shown to use chain length plasticity as a defence against copepods.
Abstract: Phytoplankton are the most important primary producers in the world’s oceans, yet little is known of how they avoid the constant threats from the pelagic grazers. From land it is well known that plants defend themselves by having thorns or producing compounds unpalatable to grazers. This thesis shows how different species of phytoplankton cope with different threats from pelagic grazers. In paper I the focus was on the dinoflagellate Alexandrium minutum, a producer of the highly potent neurotoxins paralytic shellfish toxins (PST). These toxins can cause mass mortalities in marine mammals and can be deadly to humans, who ingest the toxins via filter feeders that accumulate the toxins from algae in their diet. The suggested purpose of these toxins is to act as a defence against zooplankton grazers, like copepods. It has been shown that A. minutum is able to sense water borne cues from the copepods and respond by an increase in PST production. The results of paper I show that not only is A. minutum able to sense copepods, it can also recognize different species and respond by either increasing PST production or not. Cues from one of the copepod species tested, Centropages typicus, resulted in a more than 20 fold increase in PST, whereas another copepod, Pseudocalanus sp., did not have any effect on the PST content. It seems likely that A. minutum can recognize copepods that have the same distribution area as itself, these species would be the most significant grazers on A. minutum and a defence against them would benefit the alga. This strengthens the suggested role of PST as a grazer deterrent. Another group of substances that have been suggested to act as defence against grazers are the polyunsaturated aldehydes (PUA) produced by some phytoplankton, among others, diatoms. The role of PUA has been debated and various effects have been shown for a number of organisms. PUA has been shown to have negative effect on the reproduction of copepods, but results are contradictory. In paper II we investigate another possible defencive effect of PUA, as a structuring agent on the microbial community of bacteria and viruses. Bacteria can infect diatoms or compete for nutrients, and viral infections can terminate phytoplankton blooms. Compounds that affect these organisms can be of great benefit for the producing organism. The results in paper II show that PUA have no effect on either bacteria or viruses, and further questions the role of these compounds. Perhaps the most interesting findings in this thesis are the ones presented in paper III and IV, where diatoms are shown to use chain length plasticity as a defence against copepods. Previously, different factor such as nutrient uptake and flotation has been suggested to be the driving force behind chain formation, but chain formation as a defence has been suggested before. Here I present further support for this. The diatoms responded to cues from copepods by reducing their chain length, and thereby size, with reduced grazing as a result. Reducing chains to single cells would make the diatom Skeletonema marinoi to small for copepods to handle, while larger species like Thalassiosira rotula would still be large enough to be caught. But by reducing chain length the diatoms also reduce the encounter rate with grazers, and thus larger species like T. rotula can escape grazing. Lower grazing rates were also observed on single cells than longer chains. All diatoms did not respond to grazer cues in the same way, Chaetoceros affinis did not reduce chain length when subjected to copepods. C. affinis has long spines that may act a as a defence which could be the reason why it does not reduce its size. I suggest that chain length plasticity may be an evolutionarily adopted trait in chain forming diatoms and that size-selective predation may have played a key role in the evolution of chain formation and chain length plasticity in diatoms.
2 citations
Cites background from "Marine chemical ecology: chemical s..."
...Understanding the role of chemical cues is of great importance in order to explain the structure and function of marine systems (Hay 2009)....
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...Chemical cues determine if an organism feed on, mate with, flee from or fight with another organism (Hay 2009)....
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TL;DR: In this paper , the authors focus on how algal traits shape complementarity in feeding for a diverse suite of large herbivorous fishes on a coral reef in the wider Caribbean and find significant niche diversification in feeding both among and within genera with the three major genera having unique feeding patterns on different suites of algae.
2 citations
01 Jan 2016
TL;DR: This study identifies the optimal algal feeding diet for culturing the larvae of Siphonaria australis to competence in laboratory conditions, with a focus on algal composition and quantity and determines the cue required to induce settlement and metamorphosis.
Abstract: Laboratory rearing studies on the larvae of benthic marine invertebrates are important in providing information on the development of marine species, particularly those with complex life history cycles. Intertidal gastropods of the genus Siphonaria have been well studied in aspects of their physiology, behaviour, ecology, and reproduction. However, to our current knowledge, there are no cases on the successful laboratory rearing, from hatching through to metamorphosis, of larvae within this genus. Siphonariids are a primitive family of basommatophoran limpets in which the majority produce encapsulated embryos that hatch into feeding, planktonic veliger larvae. For such larvae, the quality and quantity of phytoplankton food can strongly affect larval growth, survival, and the ability to settle and metamorphose successfully. The primary aim of this study was to identify the optimal algal feeding diet for culturing the larvae of Siphonaria australis to competence in laboratory conditions, with a focus on algal composition and quantity. Once having defined the preferred feeding conditions, a secondary aim was to successfully culture larvae through to metamorphosis, by identifying the required settlement cue(s). First, I exposed newly hatched larvae to diets of three different algal compositions (all at a high concentration of 20,000 cells/mL): two unialgal diets of Isochrysis galbana and Pavlova lutheri, and a mixed diet consisting of a 1:1 ratio of both species. The results revealed that, although they grew in all diets, S. australis larvae exhibited highest growth and survival when fed the unialgal I.galbana diet. In a second experiment, I exposed newly hatched larvae to three different food concentrations of the unialgal I. galbana diet; low (1,000 cells/mL), medium (10,000 cells/mL) and high (20,000 cells/mL). Larval growth and survival were highest when fed a high food concentration, with development and survival severely reduced in low food treatments. At the end of this experiment it was discovered that once larvae grew to ~350µm in length, at an age of approximately one month post-hatching, they began to demonstrate signs of competence and growth rates plateaued. Finally, I exposed newly hatched larvae to optimum feeding conditions in an attempt to achieve larval settlement using different potential cues. Once larvae began to show signs of competence, they were exposed to five settlement cues: (1) live adults in filtered seawater (FSW), (2) adult-conditioned FSW, (3) rocks in adult-conditioned FSW, (4) rocks in regular FSW, and (5) crustose coralline algae-covered rocks in FSW. Larvae only successfully metamorphosed (i.e. exhibited loss of the larval velum) in treatments containing live adults. In total, my results provide a successful method in culturing Siphonaria australis larvae in laboratory conditions, as well as determines the cue required to induce settlement and metamorphosis. Not only can this method aid in providing more information on the development of this species, but it may also be applied to other members in this genus as well, and further our knowledge on the overall biology of Siphonariid limpets.
2 citations
TL;DR: Size of the cymatiid, Gutturnium muricinum, is a significant factor influencing mortality of cultured Akoya pearl oysters and growth was not influenced by predator size, and various management strategies are discussed, and further research avenues identified.
Abstract: ABSTRACT Gastropods of the family Cymatiidae are a major predator of cultured pearl oysters, causing significant mortality in ocean culture systems. Improved knowledge of factors influencing cymatiid predation on pearl oysters is required to develop effective management strategies for these predators. This study determined whether size of the cymatiid, Gutturnium muricinum, is a significant factor influencing mortality of cultured Akoya pearl oysters (Pinctada fucata), and whether predation by this cymatiid on bivalve species in an ocean culture system is nonrandom. A single G. muricinum was capable of causing significant mortality in pearl oyster stock after a 6-wk culture period, with morality influenced by predator size. Oysters housed with a large (shell length: 55.0 ± 3.3 mm) G. muricinum experienced significantly greater mortality (23.3 ± 6.3%) than those in nets with a small (shell length: 37.8 ± 2.1 mm) individual (11.1 ± 0.6%). The presence of G. muricinum also had a significant impact on pearl oyster growth, but growth was not influenced by predator size. When presented with both Akoya pearl oysters and Hyotissa hyotis as potential prey items, cymatiid predation was nonrandom. Cymatiids preferentially preyed upon H. hyotis, that experienced 45.5 ± 12.4% mortality after 6 wk of ocean culture whereas, in the same nets, none of the Akoya pearl oysters were killed. Based on these results, various management strategies are discussed, and further research avenues identified.
2 citations
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Journal Article•
839 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...…to chemical cues from specific hosts, or corals that settle in response to chemical traits of specific crustose coralline algae, or of soft-substrate animals that recruit to or avoid sands treated with specific chemical cues or extracts (e.g., Pawlik 1992, Krug & Manzi 1999, Hadfield & Paul 2001)....
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...In aquatic systems, chemical cues determine feeding, habitat, and mating choices (e.g., Hay & Fenical 1988, 1996; Pawlik 1992; Breithaupt & Thiel 2008)....
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...…stimulating feeding once prey have been contacted; compounds responsible for attraction from a distance have rarely been investigated for adult specialist consumers [compounds that cue larval settlement have been investigated; see Pawlik (1992), Krug & Manzi (1999), and Hadfield & Paul (2001)]....
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TL;DR: It is concluded that the best way to protect salt marshes and the services they provide is through the integrated approach of ecosystem-based management.
Abstract: Salt marshes are among the most abundant, fertile, and accessible coastal habitats on earth, and they provide more ecosystem services to coastal populations than any other environment. Since the Middle Ages, humans have manipulated salt marshes at a grand scale, altering species composition, distribution, and ecosystem function. Here, we review historic and contemporary human activities in marsh ecosystems—exploitation of plant products; conversion to farmland, salt works, and urban land; introduction of non-native species; alteration of coastal hydrology; and metal and nutrient pollution. Unexpectedly, diverse types of impacts can have a similar consequence, turning salt marsh food webs upside down, dramatically increasing top down control. Of the various impacts, invasive species, runaway consumer effects, and sea level rise represent the greatest threats to salt marsh ecosystems. We conclude that the best way to protect salt marshes and the services they provide is through the integrated approach of ecosystem-based management.
770 citations
TL;DR: Although numerous seaweed characteristics can deter some herbivores, the effects of morphology and chemistry have been studied most thoroughly and these types of seaweeds may be considered herbivore tolerant.
Abstract: Herbivory has a profound effect on seaweeds in both temperate and tropical communities (11, 17, 21, 33, 43, 47, 80, 124). This is especially true on coral reefs where 60-97% (11, 42) of the total seaweed production may be removed by herbivores. To persist in marine communities, seaweeds must escape, deter, or tolerate herbivory. The ecological and evolutionary importance of spatial and temporal escapes has been extensively studied for seaweeds and adequately reviewed in the recent literature (33, 45, 47, 71, 80). The ability of seaweeds to tolerate herbivory has received limited attention. On coral reefs, rapidly growing filamentous algae are heavily grazed, but the algae quickly replace these losses and appear to be dependent upon herbivores to prevent their habitat from being overgrown by larger but less herbivoretolerant species (11, 71). Additionally, several seaweeds have spores or vegetative portions that can withstand gut passage; in some cases this significantly increases the growth rates of the newly settled spores (6, 122). These types of seaweeds may be considered herbivore tolerant. Although numerous seaweed characteristics can deter some herbivores, the effects of morphology and chemistry have been studied most thoroughly. The
722 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...In aquatic systems, chemical cues determine feeding, habitat, and mating choices (e.g., Hay & Fenical 1988, 1996; Pawlik 1992; Breithaupt & Thiel 2008)....
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...…on the plants they consume and that are especially susceptible to predation suggest that feeding preferences are commonly driven by the need to colonize hosts that provide escapes from consumers rather than by the direct food value of those hosts (see also Hay & Fenical 1988, 1996; Hay 1992, 1996)....
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...In the past 20 years, the review of selected aspects of marine chemical ecology has become a growth industry (e.g., Hay & Fenical 1988, 1996; Paul 1992; Hay 1996; McClintock & Baker 2001; Paul et al. 2007; Pohnert et al. 2007; Amsler 2008), with numerous reviews focusing on specific groups…...
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TL;DR: The contention that furanones, at the concentrations produced by the alga, can control bacterial colonization of surfaces by specifically interfering with AHL-mediated gene expression at the level of the LuxR protein is supported.
Abstract: Summary: Acylated homoserine lactone (AHL)-mediated gene expression controls phenotypes involved in colonization, often specifically of higher organisms, in both marine and terrestrial environments. The marine red alga Delisea pulchra produces halogenated furanones which resemble AHLs structurally and show inhibitory activity at ecologically realistic concentrations in AHL bioassays. Evidence is presented that halogenated furanones displace tritiated OHHL [N-3- (oxohexanoy1)-L-homoserine lactone] from Escherichia coli cells overproducing LuxR with potencies corresponding to their respective inhibitory activities in an AHL-regulated bioluminescence assay, indicating that this is the mechanism by which furanones inhibit AHL-dependent phenotypes. Alternative mechanisms for this phenomenon are also addressed. General metabolic disruption was assessed with two-dimensional PAGE, revealing limited non- AHL-related effects. A direct chemical interaction between the algal compounds and AHLs, as monitored by 1H NMR spectroscopy, was shown not to occur in vitro. These results support the contention that furanones, at the concentrations produced by the alga, can control bacterial colonization of surfaces by specifically interfering with AHL-mediated gene expression at the level of the LuxR protein.
612 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...This inhibition occurs because halogenated furanones interfere with the bacteria’s signal-based regulatory systems that control surface motility, exoenzyme production, and biofilm formation/stability (Manefield et al. 1999, 2002; Rasmussen et al. 2000; McDougald et al. 2001)....
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TL;DR: This review concludes that relatively unstudied, ontogenetic shifts in concentrations and types of defenses occur in marine species, and patterns of larval chemical defenses appear to provide insights into the evolution of complex life cycles and of differing modes of development among marine invertebrates.
607 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...…on the plants they consume and that are especially susceptible to predation suggest that feeding preferences are commonly driven by the need to colonize hosts that provide escapes from consumers rather than by the direct food value of those hosts (see also Hay & Fenical 1988, 1996; Hay 1992, 1996)....
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...In other instances the larvae are chemically defended, but the adults are not and appear instead to rely more on physical/structural defenses (Lindquist & Hay 1996)....
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...…past 20 years, the review of selected aspects of marine chemical ecology has become a growth industry (e.g., Hay & Fenical 1988, 1996; Paul 1992; Hay 1996; McClintock & Baker 2001; Paul et al. 2007; Pohnert et al. 2007; Amsler 2008), with numerous reviews focusing on specific groups (seaweeds…...
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...Once larvae or embryos are released from brooding adults, they can be at considerable risk of predation in the plankton, but even more so as they recruit to the benthos where both fish and invertebrate predators are commonly concentrated (Lindquist & Hay 1996)....
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...…of resistance to host chemical defenses, selective consumption of those hosts, being cued to feed by the specific host chemicals that deter other consumers, and sequestration by the specialist of its host’s chemical defenses, thus becoming immune to many of its own enemies (Hay 1992, 1996)....
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