Reproductive plasticity in freshwater invader: from long-term sperm storage to parthenogenesis

Factors influencing accumulation of Zn, Cu, and Ca in the tissues of spiny-cheek crayfish (Faxonius limosus, Rafinesque, 1817)

Both physicochemical and biological factors affect the degree of metal accumulation in crayfish tissues. The content of metals and correlations between the metal concentrations in different tissues and the total length of crayfish is suitable indicators of contamination of the aquatic environment. The aim of the study was to analyse the effect of age and sex of crayfish on the degree of accumulation of Ca, Cu, and Zn in the muscle and exoskeleton. A total of 100 individuals of the spiny-cheek crayfish (Faxonius limosus, Rafinesque, 1817) were caught from Głowińsk reservoir (Poland) in October 2019 using fyke nets. Metal concentrations were determined in freeze-dried samples of the abdominal muscle, exoskeleton, bottom sediment, and water using atomic absorption spectroscopy (AAS). Here, we show that the highest concentrations of Zn were found in the muscle of 4-year-old females, Cu in 3-year-old males, and Ca in 4-year-old males. Sex was a significant factor affecting the content of Ca in the muscle and Zn in the exoskeleton. Age was a significant factor affecting the content of Zn, Cu, and Ca in the muscle and Zn and Cu in the exoskeleton. The bioconcentration factor (BCF) of Zn and Cu in the muscle and exoskeleton of spiny-cheek crayfish was much higher from water than from sediments, unlike Ca. Furthermore, we found significant correlation for muscle between Zn and total length in 3-year-old females and 4-year-old males and between Cu and TL in 3-year-old males. Analysing the recommended daily intake (RDI) for the investigated minerals confirmed that the consumption of 100 g of spiny-cheek crayfish muscle could meet daily requirement for Zn up to 27.5%, for Ca in 12.4%, and over 100% for Cu. The conducted analyses confirmed that the consumption of crayfish meat was safe for the health of potential consumers in terms of the analysed metal content.

Invasive Crayfish Faxonius limosus: Meat Safety, Nutritional Quality and Sensory Profile

The aim of the present study was to evaluate the safety parameters, nutritional value and sensory profile of the meat from spiny-cheek crayfish (Faxonius limosus), captured from the Danube River in Serbia. To achieve this, we determined their microbiological safety, chemical composition, minerals and heavy metals, fatty acid and amino acid profile, as well as a sensory profile of the meat. The obtained results showed that the meat from crayfish was microbiologically safe. Crayfish meat has a high nutritional quality, high protein content (18.12%) and a total of 17 detected amino acids, of which essential amino acids constituted 6.96 g/100 g sample. Additionally, the crayfish meat was characterized by high levels of essential polyunsaturated fatty acids (PUFA), particularly n-3 PUFA, at an optimal ratio of n-3/n-6 and with low values of atherogenic and thrombogenic indices. Predominant macrominerals in the meat are K, followed by Na, Ca, P and Mg, whereas the content of microminerals was in the following order: Zn > Cu > Fe > Mn. The concentrations of accumulated toxic metals (Cd, Pb, As and Hg) did not exceed the maximum allowed levels. Sensory analysis confirmed that the meat from spiny-cheek crayfish has the potential to become a new food source of essential nutrients.

Insights into Environmental Drivers on the Reproductive Cycle of Diopatra neapolitana (Polychaeta: Onuphidae)

The reproductive cycle of Diopatra neapolitana was studied over two years in Redondela (NW Spain), considering both the monthly evolution of the percentage of individuals with oocytes and the variation of the mean oocyte size. Moreover, since three other species of Diopatra have recently been documented in regions geographically close to NW Spain, we first confirmed the identity of this species by carrying out a morphological identification of a representative number of the specimens collected. Our data showed a discontinuous reproductive season, with a period of proliferation and maturation of oocytes from January to September and asynchronous spawning events between July and October. Then, a resting period in the months of November and December was observed. We also explored the influence of some relevant environmental factors (namely, water temperature, photoperiod, salinity, primary production and upwelling index) on the observed reproductive cycle. The results suggest that water temperature is one of the most important drivers of the reproductive cycle for this species. Particularly, in Ría de Vigo, the reproductive cycle seems to be influenced by upwelling events of deep cold water that occur frequently between March and September, and that could act as a spawning-inducing switch.

Functional traits explain crayfish invasive success in the Netherlands

Biological invasions by nonindigenous species can have negative effects on economies and ecosystems. To limit this impact, current research on biological invasions uses functional traits to facilitate a mechanistic understanding of theoretical and applied questions. Here we aimed to assess the role of functional traits in the progression of crayfish species through different stages of invasion and determine the traits associated with invasive success. A dataset of thirteen functional traits of 15 species currently occurring or available for sale in the Netherlands was evaluated. Six of these crayfish appeared invasive. Important traits distinguishing successful from unsuccessful invaders were a temperate climate in the native range, a medium to high egg count and producing more than one egg clutch per year. The most successful invaders had different functional trait combinations: Procambarus clarkii has a higher reproductive output, can migrate over longer distances and possesses a higher aggression level; Faxonius limosus is adapted to a colder climate, can reproduce parthenogetically and has broader environmental tolerances. Using a suit of functional traits to analyse invasive potential can help risk management and prevention. For example, based on our data Procambarus virginalis is predicted to become the next successful invasive crayfish in the Netherlands.

The crayfish model (Orconectes rusticus), epigenetics and drug addiction research

Fundamental signs of epigenetic effects are variations in the expression of genes or phenotypic traits among isogenic mates. Therefore, genetically identical animals are in high demand for epigenetic research. There are many genetically identical animals, including natural parthenogens and inbred laboratory lineages or clones. However, most parthenogenetic animal taxa are very small in combined epigenetic and drug addiction research. Orconectes rusticus has a unique phylogenetic position, with 2-3 years of life span, which undergoes metamorphosis that creates developmental stages with distinctly different morphologies, unique lifestyles, and broad behavioral traits, even among isogenic mates reared in the same environment offer novel inroads for epigenetics studies. Moreover, the establishment of crayfish as a novel system for drug addiction with evidence of an automated, operant self-administration and conditioned-reward, withdrawal, reinstatement of the conditioned drug-induced reward sets the stage to investigate epigenetic mechanisms of drug addiction. We discuss behavioral, pharmacological and molecular findings from laboratory studies that document a broad spectrum of molecular and, behavioral evidence including potential hypotheses that can be tested with the crayfish model for epigenetic study in drug addiction research.

Fertility of Spiny-Cheek Crayfish (Orconectes limosus Raf.) from the Vistula Lagoon

The aim of this study was to examine fertility of spiny-cheek crayfish harvested in the first half of April from the Vistula Lagoon and to compare it with that of the crayfish from freshwater habitats. The sample consisted of 47 sexually mature females shortly before they were ready to lay eggs. After determining the absolute fertility (number of eggs per ovary), the relative fertility was calculated (number of eggs per 1 g of body weight). Absolute and relative fertility of spiny-cheek crayfish females with total body length 8.1-11.6 cm was 535 and 17 eggs, respectively. Absolute and relative fertility was correlated with total body length and weight. Along with the increase in these parameters, the absolute fertility increased and the relative fertility decreased. A comparison of absolute and relative fertility of spiny-cheek crayfish from the Vistula Lagoon with the representatives of this species from freshwater habitats such as the Brda River and the Lake Dgał Wielki, showed no significant differences.

Plasticity in fecundity highlights the females' importance in the spiny-cheek crayfish invasion mechanism

Invasion is one of the most consequential phenomena affecting the distribution of native species. Few in number of species, European crayfish are losing the competition with introduced North American crayfish. The spiny-cheek crayfish, Orconectes limosus, is an outstanding example, successfully competing against the native narrow-clawed crayfish, Astacus leptodactylus. For four years, we collected data regarding crayfish occurrences, their relative abundance, and the structure of populations in the ongoing colonisation process of O. limosus in the lower Danube. The mature females of both invasive and indigenous crayfish species were analysed with respect to biometry and production of oocytes in relation to the dynamics of invasion. The interspecific comparisons showed no significant differences regarding body size, with an average of approximately 102 mm total length and 31 g wet weight for both species. However, the fecundity of the indigenous species was found to be constant throughout the investigated area, whereas the number of eggs produced by the invasive females was significantly increased at the active front of the invasion. The maximum number of ovarian eggs found was 887 and 1156 in the indigenous species and the invasive species, respectively. We propose the scenario that the invasive species, which carries the deadly crayfish plague, creates an ecological advantage by reducing the populations of indigenous crayfish. Subsequently, the invasive females opportunistically use the available resources to enhance their fecundity, resulting in the acute growth of populations. However, the long-term competitiveness and colonisation success of O. limosus still remain in question.

Evidence for multiple paternity in two species of Orconectes crayfish

Multiple mating is expected to be common in organisms that produce large clutches as a mechanism by which sexual reproduction can enrich genetic variation. For freshwater crayfish, observation of multiple mating suggests the potential for high rates of multiple paternity, but genetic confirmation is largely lacking from natural populations. We studied paternity within wild-caught broods of two crayfish species in the genus Orconectes (Sanborn’s crayfish (Orconectes sanbornii (Faxon, 1884)) and the Allegheny crayfish (Orconectes obscurus (Hagen, 1870))). Although females have been observed mating with multiple males, this is the first genetic confirmation of multiple paternity in broods of these two species. Berried females were collected in the field and maintained in aquaria until their eggs hatched. We amplified and genotyped extracted DNA from maternal and hatchling tissue for several microsatellite loci. For both species, paternity reconstruction (GERUD 2.0) yielded 2–3 sires per brood and no single paternity clutches. We discuss these results from natural populations in light of the body of work on reproductive ecology of decapod crustaceans and in the context of changes in life history following the transition from marine to freshwater habitats.

Plasticity-mediated persistence in new and changing environments

Baldwin's synthesis of the Organicist position, first published in 1896 and elaborated in 1902, sought to rescue environmentally induced phenotypes from disrepute by showing their Darwinian significance. Of particular interest to Baldwin was plasticity's mediating role during environmental change or colonization—plastic individuals were more likely to successfully survive and reproduce in new environments than were nonplastic individuals. Once a population of plastic individuals had become established, plasticity could further mediate the future course of evolution. The evidence for plasticity-mediated persistence (PMP) is reviewed here with a particular focus on evolutionary rescue experiments, studies on invasive success, and the role of learning in survival. Many PMP studies are methodologically limited, showing that preexistent plasticity has utility in new environments (soft PMP) rather than directly demonstrating that plasticity is responsible for persistence (hard PMP). An ideal PMP study would be able to demonstrate that (1) plasticity preexisted environmental change, (2) plasticity was fortuitously beneficial in the new environment, (3) plasticity was responsible for individual persistence in the new environment, and (4) plasticity was responsible for population persistence in succeeding generations. Although PMP is not ubiquitous, Baldwin's hypotheses have been largely vindicated in theoretical and empirical studies, but much work remains.