Toxicity of the purple mucus of the polychaete Halla parthenopeia (Oenonidae) revealed by a battery of ecotoxicological bioassays

Mucus secretions play a number of functions related to polychaete physiology and ecology. Under stress conditions, the polychaete Halla parthenopeia (Oenonidae) produces a purple mucus after mechanical stimulation, whose function is still unknown. Here, we assessed the toxicity of this purple mucus by means of both acute toxicity bioassays on the polychaete Dinophilus gyrociliatus and commercial ecotoxicological kits (Microtox\uae, Rotoxkit\uae and Artoxkit\uae). Palatability was also tested with the fish Oryzias melastigma. After emitting purple mucus, H. parthenopeia quickly moves away and starts releasing transparent mucus. Acute toxicity bioassays showed that the mucus was harmless (transparent), or lethal even when diluted about 1000 times (purple). Purple mucus was toxic at different concentrations, the LC50 ranging from 0.7-0.3 g l\u20131 for D. gyrociliatus to 76 g l\u20131 for Artemia franciscana (Artoxkit\uae). Freeze-dried brine shrimp coated with transparent or purple muci were both consumed by O. melastigma. We hypothesized that the purple mucus is involved in the chemical defence of H. parthenopeia against competitors and parasites, and that its colour and toxicity are due to hallachrome, a 1,2-anthraquinone found in the skin of H. parthenopeia

Metabolic rate thermal plasticity in the marine annelid Ophryotrocha labronica across two successive generations

Marine ectotherms have evolved a range of physiological strategies to cope with temperature changes that persist across generations. For example, metabolic rates are expected to increase following an acute exposure to temperature, with potential detrimental impacts for fitness. However, they may be downregulated in the following generation if offspring experience the thermal conditions of their parents, with a resulting decrease in maintenance costs and fitness maximization. Yet, trans-generational studies on metabolic rates are few in marine ectotherms, thus limiting our ability to accurately predict longer-term implications of ocean warming on organisms' performance, metabolic rates being the fundamental pacemaker for all biological processes. This is particularly true for small-size organisms, for which the determination of individual metabolic rates has been historically challenging, and for many groups of marine invertebrates, such as annelids, which are under-represented in physiological investigations. Here, we exposed the subtidal annelid Ophryotrocha labronica (body length: ~4 mm) to a thermal gradient (21, 24, 26, 29°C) and measured, for the first time in this species, the temperature dependence of metabolic rates across two generations. We found that metabolic rates were positively related to temperature, but this relationship did not differ between generations. Our study provides additional evidence for the diversity of temperature-associated physiological responses of marine ectotherms and offers a number of methodological recommendations for unveiling the mechanisms underpinning the observed trans-generational responses of metabolic rates in marine annelid species. -- Keywords : Acclimation ; annelids ; ectotherms ; oceanwarming ; oxygen uptake rates ; trans-generational effects

Plastic adjustments of biparental care behavior across embryonic development under elevated temperature in a marine ectotherm

Phenotypic plasticity in parental care investment allows organisms to promptly respond to rapid environmental changes by potentially benefiting offspring survival and thus parental fitness. To date, a knowledge gap exists on whether plasticity in parental care behaviors can mediate responses to climate change in marine ectotherms. Here, we assessed the plasticity of parental care investment under elevated temperatures in a gonochoric marine annelid with biparental care, Ophryotrocha labronica, and investigated its role in maintaining the reproductive success of this species in a warming ocean. We measured the time individuals spent carrying out parental care activities across three phases of embryonic development, as well as the hatching success of the offspring as a proxy for reproductive success, at control (24℃) and elevated (27℃) temperature conditions. Under elevated temperature, we observed: (a) a significant decrease in total parental care activity, underpinned by a decreased in male and simultaneous parental care activity, in the late stage of embryonic development; and (b) a reduction in hatching success that was however not significantly related to changes in parental care activity levels. These findings, along with the observed unaltered somatic growth of parents and decreased brood size, suggest that potential cost-benefit trade-offs between offspring survival (i.e., immediate fitness) and parents' somatic condition (i.e., longer-term fitness potential) may occur under ongoing ocean warming. Finally, our results suggest that plasticity in parental care behavior is a mechanism able to partially mitigate the negative effects of temperature-dependent impacts. -- Keywords : Behavioral plasticity ; Brood size ; Global warming ; Hatching success ; Invertebrates ; Parental investment

Life-history traits display strong associations to genome size in annelids

Genome size, known also as the C-value, has been proposed as an important determinant of life-history variation in numerous animal taxa. We assessed the relationships between genome size and fitness-related life-history traits in six species of interstitial marine annelids of the genus Ophryotrocha. Life-history traits and genome size data obtained from 18 additional annelid species were included in our analyses to have a broader phylogenetic scope. Unexpectedly, genome sizes assessed here by flow cytometry in four Ophryotrocha species were three times larger than previously reported values obtained using Feulgen densitometry. This has implications for the hypothesis that harsh interstitial habitats select for small genomes in meiofaunal annelids. Within the genus Ophryotrocha, significant and positive relationships were found between genome size and nucleus size, and between genome size, age at first egg mass deposition, body size and lifespan. These relationships held up in the broader phylogenetic comparison. Our study provides evidence for the important role played by genome size in the evolution of life-history traits in annelids. -- Keywords : C-value ; Flow cytometry ; Ophryotrocha ; Body size ; Developmental rate ; Lifespan

Can trans-generational experiments be used to enhance species resilience to ocean warming and acidification?

Human-assisted, trans-generational exposure to ocean warming and acidification has been proposed as a conservation and/or restoration tool to produce resilient offspring. To improve our understanding of the need for and the efficacy of this approach, we characterized life-history and physiological responses in offspring of the marine polychaete Ophryotrocha labronica exposed to predicted ocean warming (OW: + 3 degrees C), ocean acidification (OA: pH -0.5) and their combination (OWA: + 3 degrees C, pH -0.5), following the exposure of their parents to either control conditions (within-generational exposure) or the same conditions (trans-generational exposure). Trans-generational exposure to OW fully alleviated the negative effects of within-generational exposure to OW on fecundity and egg volume and was accompanied by increased metabolic activity. While within-generational exposure to OA reduced juvenile growth rates and egg volume, trans-generational exposure alleviated the former but could not restore the latter. Surprisingly, exposure to OWA had no negative impacts within-or trans-generationally. Our results highlight the potential for trans-generational laboratory experiments in producing offspring that are resilient to OW and OA. However, trans-generational exposure does not always appear to improve traits and therefore may not be a universally useful tool for all species in the face of global change

Extensive gene rearrangements in the mitogenomes of congeneric annelid species and insights on the evolutionary history of the genus Ophryotrocha

Background Annelids are one the most speciose and ecologically diverse groups of metazoans. Although a significant effort has been recently invested in sequencing genomes of a wide array of metazoans, many orders and families within the phylum Annelida are still represented by a single specimen of a single species. The genus of interstitial annelids Ophryotrocha (Dorvilleidae, Errantia, Annelida) is among these neglected groups, despite its extensive use as model organism in numerous studies on the evolution of life history, physiological and ecological traits. To compensate for the paucity of genomic information in this genus, we here obtained novel complete mitochondrial genomes of six Ophryotrocha species using next generation sequencing. In addition, we investigated the evolution of the reproductive mode in the Ophryotrocha genus using a phylogeny based on two mitochondrial markers (COXI and 16S rDNA) and one nuclear fragment (Histone H3). Results Surprisingly, gene order was not conserved among the six Ophryotrocha species investigated, and varied greatly as compared to those found in other annelid species within the class Errantia. The mitogenome phylogeny for the six Ophryotrocha species displayed a separation of gonochoric and hermaphroditic species. However, this separation was not observed in the phylogeny based on the COX1, 16S rDNA, and H3 genes. Parsimony and Bayesian ancestral trait reconstruction indicated that gonochorism was the most parsimonious ancestral reproductive mode in Ophryotrocha spp. Conclusions Our results highlight the remarkably high level of gene order variation among congeneric species, even in annelids. This encourages the need for additional mitogenome sequencing of annelid taxa in order to properly understand its mtDNA evolution, high biodiversity and phylogenetic relationships. -- Keywords : Molecular phylogeny ; Dorvilleidae ; Mitogenome ; Next generation sequencing ; Model species ; Reproductive mode

Sessualità e fitness nel genere Ophryotrocha (Polychaeta): confronto tra specie gonocoriche ed ermafrodite.

In this study the relationship between life-history, sexuality and fitness of three species of Ophryotrocha (Polychaeta, Dorvilleidae) with three different sexual strategies (gonochorism, simultaneous hermaphroditism and protandrous hermaphroditism) has been analyzed. Survivorship and fecundity data were collected weekly and used to define the relative contribution of these two ecological parameters to differences in the population growth rate. Results indicate that gonochorism is the most advantageous condition for fitness and demographic growth

Gonochorism vs. hermaphroditism: relationship between life history and fitness in three species of Ophryotrocha (Polychaeta : Dorvilleidae) with different forms of sexuality

The relationships between life history, fitness and sexuality, together with their ecological and evolutionary significance, has been analysed comparing the main life-history traits and demography in three closely related species belonging to the genus Ophryotrocha. The species are: the gonochoristic O. labronica, the simultaneous hermaphrodite O. diadema and the protandrous hermaphrodite O. puerilis. 2. Survivorship and reproductive data were collected weekly and were used to construct life tables and population projection matrices for each species and compare life-history characteristics. Elasticity, life-table response and decomposition analyses were performed to examine the relative contribution of fecundity and survivorship to differences in lambda between species. 3. The gonochoristic and hermaphroditic species differ in all the main life-history parameters and also in demographic characteristics. In particular the value of lambda, used commonly to express fitness, is markedly higher in the gonochoristic species while in terms of fitness simultaneous and sequential hermaphroditism are very similar. In the genus Ophryotrocha gonochorism currently represents the most widespread condition, being characteristic of the majority of the known species in the genus. 4. Given the demographic advantage ensured by gonochorism, it remains be understood why some species have retained simultaneous hermaphroditism and one has evolved a sequential type hermaphroditism; the most probable hypothesis is correlated with the density of the species in natural habitats

Plasticità trans-generazionale della tolleranza termica nel polichete Ophryotrocha labronica (Annelida: Dorvilleidae)

Il fenotipo e l’ambiente materno sono noti essere importanti fattori in grado di influenzare il fenotipo dei discendenti. Tuttavia, poco si sa del loro ruolo nell’influenzare la tolleranza termica della prole. Abbiamo utilizzato il polichete marino Ophryotrocha labronica (Annelida: Dorvilleidae) per 1) studiare l’effetto che la temperatura ambientale materna ha sulle risposte di tolleranza termica dei discendenti, 2) stabilire se questo effetto è mantenuto anche nella fase adulta dei discendenti, e 3) valutare il ruolo dello stadio di sviluppo pre-zigotico dei discendenti nel definire il risultato dell’effetto materno. Abbiamo misurato i limiti di tolleranza termica superiori e inferiori di individui adulti acclimatati a 18 °C o 30 °C, le cui madri erano state fatte crescere a 24 °C e, al raggiungimento della maturità sessuale, erano state esposte a 18 °C o 30 °C sia ad uno stadio precoce che uno tardivo dell’oogenesi. Quando la temperatura materna e quella della prole differiva e l’esposizione da 24 °C a 18 °C o 30 °C avveniva ad uno stadio precoce dell’oogenesi, venivano prodotti discendenti più resistenti sia al freddo che al caldo, suggerendo l’esistenza di un effetto materno di tipo “anticipatorio” innescato dal segnale termico sperimentato dalle madri. Al contrario, quando le madri sperimentavano la variazione termica in una fase più tardiva dell’oogenesi, la tolleranza termica dei discendenti si riduceva (rispetto a quanto osservato quando temperatura materna e della prole si eguagliavano). L’esistenza di limiti nella trasmissione del segnale materno nel corso dello sviluppo pre-zigotico potrebbe spiegare quest’ultimo risultato. Infine, l’influenza materna è stata mantenuta fino allo stadio adulto dei discendenti. Per la prima volta in una specie marina, abbiamo dimostrato l’esistenza di plasticità trans-generazionale nella tolleranza termica. I nostri risultati sono importanti per migliorare la comprensione delle strategie evolute dalle specie in ambienti termicamente fluttuanti e sono utili nel definire le risposte degli organismi nei confronti dell’inasprimento delle variazioni termiche in conseguenza ai cambiamenti climatici