Feeding repellence in Antarctic bryozoans

Abstract

The Antarctic sea star Odontaster validus and the amphipod Cheirimedon femoratus are important predators in benthic communities. Some bryozoans are part of the diet of the asteroid and represent both potential host biosubstrata and prey for this omnivorous lysianassid amphipod. In response to such ecological pressure, bryozoans are expected to develop strategies to deter potential predators, ranging from physical to chemical mechanisms. However, the chemical ecology of Antarctic bryozoans has been scarcely studied. In this study we evaluated the presence of defenses against predation in selected species of Antarctic bryozoans. The sympatric omnivorous consumers O. validus and C. femoratus were selected to perform feeding assays with 16 ether extracts (EE) and 16 butanol extracts (BE) obtained from 16 samples that belonged to 13 different bryozoan species. Most species (9) were active (12 EE and 1 BE) in sea star bioassays. Only 1 BE displayed repellence, indicating that repellents against the sea star are mainly lipophilic. Repellence toward C. femoratus was found in all species in different extracts (10 EE and 12 BE), suggesting that defenses against the amphipod might be both lipophilic and hydrophilic. Interspecific and intraspecific variability of bioactivity was occasionally detected, suggesting possible environmental inductive responses, symbiotic associations, and/or genetic variability. Multivariate analysis revealed similarities among species in relation to bioactivities of EE and/or BE. These findings support the hypothesis that, while in some cases alternative chemical or physical mechanisms may also provide protection, repellent compounds play an important role in Antarctic bryozoans as defenses against predators.

The Phylum Bryozoa: From Biology to Biomedical Potential

“…Avila and colleagues examined the chemical ecology of Antarctic bryozoans [101][102][103][104]. Extracts from 11 out of an examined 17 species were deterrent to the omnivorous sea star Odontaster validus, and 13 out of 13 were repellent to the amphipod Cheirimedon femoratus, indicating a high percentage of species with chemical defenses [101,104]. They subsequently demonstrated that while none of the extracts from the 13 bryozoan species were cytotoxic towards sea urchin embryos, they were toxic for sea urchin sperm [102].…”

“…Chemical structures of amathamides A-G (5a-5g) and β-phenylethylamine (6).Studies of ecological interactions in polar regions have provided important leads for future studies. Avila and colleagues examined the chemical ecology of Antarctic bryozoans[101][102][103][104]. Extracts from 11 out of an examined 17 species were deterrent to the omnivorous sea star Odontaster validus, and 13 out of 13 were repellent to the amphipod Cheirimedon femoratus, indicating a high percentage of species with chemical defenses[101,104].…”

The Understudied Phylum Bryozoa as a Promising Source of Anticancer Drugs

“…We previously reported intraspecific variability in a range of biological activities (e.g. feeding repellence and antibacterial) for bryozoans depending on location and/or depth, as an adaptive response to diverse abiotic and biotic factors and/or genetic or symbiotic variability [21,24]. In addition, these bryozoan species tested, together with the discovery of more than 20 new species [14,15], were collected in remote areas (Polar regions and/or deep sea environments) using advanced diving and survey technologies.…”

Ecological and Pharmacological Activities of Antarctic Marine Natural Products

“…Here, we found it interesting to analyze which depths were yielding more bioactive samples as well as whether this was correlated with the living habits of the organisms (sessile vs. vagile). Our previous studies provided information on some of these aspects for different samples and cruises [4,5,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. In this paper, the chemical defenses of the Antarctic marine organisms studied during the ECOQUIM and ACTIQUIM projects, as well as their pharmacological potential, are reviewed.…”

“…For the pharmacological activity, anticancer, anti-inflammatory, and antibacterial activities have been considered. The methodologies for each one of these assays have been previously reported elsewhere [4,5,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. It is worth mentioning that all of our assays are done at natural concentrations (the same as in the organism tested), with very few exceptions (some isolated compounds, for instance, or some particular tests), and including the corresponding controls according to each kind of assay [4,5,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”