Invertebrates

Sleep in invertebrate

by Stefania Piscopo

open access

Regulatory effects of mussel (Aulacomya maoriana Iredale 1915) larval settlement by neuroactive compounds, amino acids and bacterial biofilms

by Tim Young

Published in 'Aquaculture' Volumes 322–323, 21 December 2011, Pages 158–168

Larval settlement responses of the ribbed mussel, Aulacomya maoriana Iredale 1915, were investigated after exposure to... more Larval settlement responses of the ribbed mussel, Aulacomya maoriana Iredale 1915, were investigated after exposure to various chemicals and mono-species bacteria. Identification of settlement inductive compounds assists in the elucidation of intermediary biochemical mechanisms involved in the neuronal control of settlement behaviour downstream from primary cue reception. Neuroactive compounds and amino acids (potassium ions, GABA, acetylcholine, l-Phenylalanine, l-Tyrosine, dopamine, epinephrine, l-Tryptophan, and 5-HTP) and planktonic bacteria, biofilms and biofilm exudates of Macrococcus sp. AMGM1, Bacillus sp. AMGB1, and Pseudoalteromonas sp. AMGP1 were tested for their abilities to induce larval settlement. Toxicity effects of each treatment also were simultaneously identified by recording larval mortalities. Results indicate that all chemicals used induced larvae to settle, with acetylcholine being the most effective (~ 24% at 10−6 M compared to < 2% in control assays). Toxicities of treatment compounds were low at optimal settlement inducing concentrations, except for l-Tryptophan (~ 32%) and GABA (~ 59%). Our data suggest that catecholamines (and their precursors) play an important role in the biochemical mechanisms of settlement for A. maoriana. While serotonin precursors did induce low levels of larval settlement at some concentrations, high toxicity responses to 5-HTP at 10−5 M, combined with complete settlement inhibition indicate that the mechanism of action may be more complex than can be elucidated in this study. Larval settlement responses to bacterial treatments were low for planktonic and biofilm phases across all three strains, and settlement inhibition was observed when larvae were exposed to biofilm exudates of all bacterial strains. Comparisons of A. maoriana responses to other endemic and worldwide distributed mussel species are provided as a means to highlight potential evolutionary differences in chemoreception mechanisms.

Can ecological stoichiometry help explain patterns of biological invasions?

by Angélica L. González

Oikos 119: 779–790, 2010

Several mechanisms for biological invasions have been proposed, yet to date there is no common framework that can... more Several mechanisms for biological invasions have been proposed, yet to date there is no common framework that can broadly explain patterns of invasion success among ecosystems with different resource availabilities. Ecological stoichiometry (ES) is the study of the balance of energy and elements in ecological interactions. This framework uses a multi-nutrient approach to mass-balance models, linking the biochemical composition of organisms to their growth and reproduction, which consequently influences ecosystem structure and functioning. We proposed a conceptual model that integrates hypotheses of biological invasions within a framework structured by fundamental principles of ES. We then performed meta-analyses to compare the growth and production performances of native and invasive organisms under low- and high-nutrient conditions in terrestrial and aquatic ecosystems. Growth and production rates of invasive organisms (plants and invertebrates) under both low- and high-nutrient availability were generally larger than those of natives. Nevertheless, native plants outperformed invasives in aquatic ecosystems under low-nutrient conditions. We suggest several distinct stoichiometry-based mechanisms to explain invasion success in low- versus high-nutrient conditions; low-nutrient conditions: higher resource-use efficiency (RUE; C:nutrient ratios), threshold elemental ratios (TERs), and trait plasticity (e.g. ability of an organism to change its nutrient requirements in response to varying nutrient environmental supply); high- nutrient conditions: higher growth rates and reproductive output related to lower tissue C:nutrient ratios, and increased trait plasticity. Interactions of mechanisms may also yield synergistic effects, whereby nutrient enrichment and enemy release have a disproportionate effect on invasion success. To that end, ES provides a framework that can help explain how chemical elements and energy constrain key physiological and ecological processes, which can ultimately determine the success of invasive organisms.

Exploring patterns and mechanisms of interspecific and intraspecific variation in body elemental composition of desert consumers

by Angélica L. González

Oikos 120: 1247–1255, 2011

Key processes such as trophic interactions and nutrient cycling are often influenced by the element content of organ-... more Key processes such as trophic interactions and nutrient cycling are often influenced by the element content of organ- isms. Previous analyses have led to some preliminary understanding of the relative importance of evolutionary and ecological factors determining animal stoichiometry. However, to date, the patterns and underlying mechanisms of consumer stoichiometry at interspecific and intraspecific levels within natural ecosystems remain poorly investigated. Here, we examine the association between phylogeny, trophic level, body size, and ontogeny and the elemental com- position of 22 arthropod as well as two lizard species from the coastal zone of the Atacama Desert in Chile. We found that, in general, whole-body P content was more variable than body N content both among and within species. Body P content showed a significant phylogenetic signal; however, phylogeny explained only 4% of the variation in body P content across arthropod species. We also found a significant association between trophic level and the element content of arthropods, with carnivores having 15% greater N and 70% greater P contents than herbivores. Elemental scaling relationships across species were only significant for body P content, and even the P content scaling relationship was not significant after controlling for phylogeny. P content did decrease significantly with body size within most arthropod species, which may reflect the size dependence of RNA content in invertebrates. In contrast, larger lizards had higher P contents and lower N:P ratios than smaller lizards, which may be explained by size-associated differences in bone and scale investments. Our results suggests that structural differences in material allocation, trophic level and phylogeny can all contribute to variation in the stoichiometry of desert consumers, and they indicate that the elemental composition of animals can be useful information for identifying broad-scale linkages between nutrient cycling and trophic interactions in terrestrial food webs.

Ophiuroidea (Echinodermata) do Miocénico da Lagoa de Albufeira (Portugal)

by Bruno Pereira

Pesented at the VII EJIP

The aim of this work was to reclassify ophiuroid material found on the Miocene from Lagoa de Albufeira, in Portugal.... more The aim of this work was to reclassify ophiuroid material found on the Miocene from Lagoa de Albufeira, in Portugal. This material was initially described in 2006, but just a few was known. By comparing it modern ophiuroids, more was parts were classify. Modern studies on taphonomy of this animals permit to understand how the paleoenvironment was.

Evolution of a Novel Developmental Trajectory: Fission is Distinct From Regeneration In the Annelid Pristina Leidyi

by Eduardo Zattara