Biology subjects

Garbaras, A.

Publications and source records attributed to Garbaras, A..

3 recordsLinked to original sources

bioRxiv2023

Invasion is accompanied by dietary contraction in Ponto-Caspian amphipods

A species expansion beyond the native range is often assumed to be associated with an increased dietary niche breadth. However, empirical evidence remains limited due to a scarcity of studies comparing both the parental and invaded ranges. Here, we test the trophic niche expansion hypothesis by examining stable isotopes and functional morphology across native (NW Black Sea) and invaded (SE Baltic Sea) ranges of two amphipods, Dikerogammarus villosus and Pontogammarus robustoides, originating from the Ponto-Caspian region - a major source of species invading Holarctic inland waters. Stable isotopes revealed that both species underwent a twofold contraction of the dietary niche with a shift towards decreased carnivory in the invaded range. This dietary shift was morphologically mirrored by an overall reduction of prey grasping appendages, antennae, and mouthpart palps. The magnitude of dietary and morphological change was greater in D. villosus. Our findings indicate that previous experimental reports of aggressive predation in D. villosus reflect opportunistic foraging and align with local stable isotope studies which generally indicate a low trophic position. We conclude that Ponto-Caspian species can undergo rapid, if non-intuitive, changes in both diet and functional morphology outside the native range, likely contributing to their invasive potential.

ecology↗

bioRxiv2019

Increase in stable isotope ratios driven by metabolic alterations in amphipods exposed to the beta-blocker propranolol

Anthropogenic pressures, such as contaminant exposure, may affect stable isotope ratios in biota. These changes are driven by alterations in the nutrient allocation and metabolic pathways induced by specific stressors. In a controlled microcosm study with the amphipod Gammarus spp., we studied effects of the {beta}-blocker propranolol on stable isotope signatures ({delta}15N and {delta}13C), elemental composition (%C and %N), and growth (protein content and body size) as well as biomarkers of oxidative status (antioxidant capacity, ORAC; lipid peroxidation, TBARS) and neurological activity (acetylcholinesterase, AChE). Based on the known effects of propranolol exposure on cellular functions, i.e., its mode of action (MOA), we expected to observe a lower scope for growth, accompanied by a decrease in protein deposition, oxidative processes and AChE inhibition, with a resulting increase in the isotopic signatures. The observed responses supported most of these predictions. In particular, %N was positively affected by propranolol, whereas both protein allocation and body size declined. Moreover, both ORAC and TBARS levels decreased with increasing propranolol concentration, with the decrease being more pronounced for TBARS, which indicates the prevalence of the antioxidative processes. These changes resulted in a significant increase of the {delta}15N and {delta}13C values in the propranolol-exposed animals compared to the control. These findings suggest that MOA of {beta}-blockers may be used to predict sublethal effects in nontarget species, including inhibited AChE activity, improved oxidative balance, and elevated stable isotope ratios. The latter also indicates that metabolism-driven responses to environmental contaminants can alter stable isotope signatures, which should be taken into account when interpreting trophic interactions in the food webs.

ecology↗

bioRxiv2018

Is there a BMAA transfer in the pelagic and benthic food webs in the Baltic Sea?

The evidence regarding BMAA occurrence in the Baltic Sea is contradictory, with benthic sources appearing to be more important than pelagic ones. The latter is counterintuitive considering that pelagic primary producers, such as diatoms, dinoflagellates, and cyanobacteria, are the only plausible source of this compound in the food webs. To elucidate BMAA distribution in trophic pathways, we analyzed BMAA in the pelagic and benthic food webs sampled in summer 2010 in the Northern Baltic Proper. As potential BMAA sources, phytoplankton communities in early and late summer were used. As pelagic consumers, zooplankton, mysids and zooplanktivorous fish (herring) were used, whereas benthic invertebrates (amphipods, priapulids, polychaetes, and clams) and benthivorous fish (perch and flounder) represented the benthic food chain. To establish the trophic structure of the system, the stable isotope ({delta}13C and {delta}15N) composition of its components was determined. Contrary to the reported ubiquitous occurrence of BMAA in the Baltic food webs, only phytoplankton and lower consumers (zooplankton and mysids) of the pelagic food chain tested positive. Given that our analytical approaches were adequate, we conclude that no measurable levels of this compound occurred in the benthic invertebrates and any of the tested fish species in the study area. These findings indicate that widely assumed presence and transfer of BMAA to the top consumers in the food webs of the Baltic Sea and, possibly, other systems remain an open question. More controlled experiments and field observations are needed to understand the transfer and possible transformation of BMAA in the food web under various environmental settings.

ecology↗