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Determining how and how often asexual lineages emerge within sexual species is central to our understanding of sex-asex transitions and the long-term maintenance of sex. Asexuality can arise “by transmission” from an existing asexual lineage to a new one, through different types of crosses. The occurrence of these crosses, cryptic sex, variation in ploidy and recombination within asexuals greatly complicates the study of sex-asex transitions, as they preclude the use of standard phylogenetic methods and genetic distance metrics. In this study we show how to overcome these challenges by developing new approaches to investigate the origin of the various asexual lineages of the brine shrimp Artemia parthenogenetica. We use a large sample of asexuals, including all known polyploids, and their sexual relatives. We combine flow cytometry with mitochondrial and nuclear DNA data. We develop new genetic distance measures and methods to compare various scenarios describing the origin of the different lineages. We find that all diploid and polyploid A. parthenogenetica likely arose within the last 80,000 years through successive and nested hybridization events that involved backcrosses with different sexual species. All A. parthenogenetica have the same common ancestor and therefore likely carry the same asexuality gene(s) and reproduce by automixis. These findings radically change our view of sex-asex transitions in this group, and show the importance of considering asexuality “by transmission” scenarios. The methods developed are applicable to many other asexual taxa.

Previous data revealed the unexpected presence of genes encoding for long-chain polyunsaturated fatty acid (LC-PUFA) biosynthetic enzymes in transcriptomes from freshwater gammarids but not in marine species, even though closely related species were compared. This study aimed to clarify the origin and occurrence of selected LC-PUFA biosynthesis gene markers across all published gammarid transcriptomes. Through systematic searches, we confirmed the widespread occurrence of sequences from seven elongases and desaturases involved in LC-PUFA biosynthesis, in transcriptomes from freshwater gammarids but not marine species, and clarified that such occurrence is independent from the gammarid species and geographical origin. The phylogenetic analysis established that the retrieved elongase and desaturase sequences were closely related to bdelloid rotifers, confirming that multiple transcriptomes from freshwater gammarids contain contaminating rotifers’ genetic material. Using the Adineta steineri genome, we investigated the genomic location and exon–intron organization of the elongase and desaturase genes, establishing they are all genome-anchored and, importantly, identifying instances of horizontal gene transfer. Finally, we provide compelling evidence demonstrating Bdelloidea desaturases and elongases enable these organisms to perform all the reactions for de novo biosynthesis of PUFA and, from them, LC-PUFA, an advantageous trait when considering the low abundance of these essential nutrients in freshwater environments.

Artemia nauplii are widely used as live preys for feeding early life-cycle stages of marine finfish and shrimp. However, a major drawback associated to using Artemia is their deficient nutritional value for marine larvae that is primarily linked to suboptimal levels of long-chain polyunsaturated fatty acids (LC-PUFA), essential nutrients that guarantee normal growth and development of animals. While common marine hatchery procedures involve enrichment processes to address such nutritional deficiencies, the specific drivers accounting for the naturally occurring variability in LC-PUFA of Artemia are largely unknown. Biosynthesis, along diet, is one of the main factors determining the LC-PUFA profiles in animals and it depends upon the repertoire and function of fatty acyl elongases and desaturases existing in a particular species. The aim of this study was the molecular and functional characterisation of all elongase and desaturase enzymes involved in the LC-PUFA biosynthesis from Artemia franciscana, arguably the most commonly used Artemia species. Seven out of eight elongases (termed “Elo1-8”) found in A. franciscana had distinctive features of LC-PUFA biosynthesising elongases. Consistently, functional assays showed these elongases were able to elongate multiple substrates and thus enabling A. franciscana to perform all elongation reactions of the LC-PUFA biosynthetic pathways. While all seven functionally characterised elongases from A. franciscana showed activity towards multiple substrates including C18 to C22 polyunsaturated fatty acids, particularly high activity was detected for the Elovl8 orthologue (termed herein as “Elo7”). Additionally, A. franciscana was found to have three genes of the so-called “first” desaturases (“Des1-3”), and lack other key LC-PUFA biosynthesising desaturases such as methyl-end and front-end desaturases. Two desaturases have the expected ∆9 desaturase activity, whereas a third one showed ∆12 activity. Neither methyl-end nor front

Species of Artemia are regionally endemic branchiopod crustaceans composed of sexual species and parthenogenetic lineages, and represent an excellent model for studying adaptation and speciation to extreme and heterogeneous hypersaline environments. We tested hypotheses of whether populations from the Tibetan Plateau belong to A. tibetianaAbatzopoulos, Zhang & Sorgeloos,1998 and whether a population from Kazakhstan is a new species, using other Asian species of Artemia as outgroups. We conducted a multitrait phylogenetic study based on the complete mitogenome, mitochondrial (COI, 12S, 16S) and nuclear (microsatellites, ITS1) markers, and a suit of uni- and multivariate morphological traits. Our results led to the discovery of two new species, one from the Tibetan Plateau (Haiyan Lake) in China (Artemia sorgeloosin. sp.) and a second from Kazakhstan (Artemia amatin. sp.). Our analysis demonstrate that A. tibetiana and A. amatin. sp. are monophyletic, whereas A. sorgeloosin. sp., and A. tibetiana are polyphyletic. Evolutionary relationships based on mitochondrial and nSSR markers suggest that A. tibetiana may have arisen from a past hybridization event of a maternal ancestor of A. tibetiana with A. sorgeloosin. sp. or its ancestor. We present the complete mitogenome of A. tibetiana, A. amatin. sp., and A. sorgeloosin. sp. We also provide a novel taxonomic identification key based on morphology, emphasizing the phenotype as a necessary component of the species concept.

Previous data revealed the unexpected presence of genes encoding for long-chain polyunsaturated fatty acid (LC-PUFA) biosynthetic enzymes in transcriptomes from freshwater gammarids but not in marine species, even though closely related species were compared. This study aimed to clarify the origin and occurrence of selected LC-PUFA biosynthesis gene markers across all published gammarid transcriptomes. Through systematic searches, we confirmed the widespread occurrence of sequences from seven elongases and desaturases involved in LC-PUFA biosynthesis, in transcriptomes from freshwater gammarids but not marine species, and clarified that such occurrence is independent from the gammarid species and geographical origin. The phylogenetic analysis established that the retrieved elongase and desaturase sequences were closely related to bdelloid rotifers, confirming that multiple transcriptomes from freshwater gammarids contain contaminating rotifers' genetic material. Using the Adineta steineri genome, we investigated the genomic location and exon–intron organization of the elongase and desaturase genes, establishing they are all genome-anchored and, importantly, identifying instances of horizontal gene transfer. Finally, we provide compelling evidence demonstrating Bdelloidea desaturases and elongases enable these organisms to perform all the reactions for de novo biosynthesis of PUFA and, from them, LC-PUFA, an advantageous trait when considering the low abundance of these essential nutrients in freshwater environments.

The fatty acyl elongases Elovl4 are pivotal components in the biosynthesis of very long-chain polyunsaturated fatty acids (VLC-PUFA) from long-chain polyunsaturated fatty acids (LC-PUFA). Thus, nutritional regulation of Elovl4, as well as other elongase and desaturase genes involved in LC-PUFA biosynthesis (e.g., Elovl5, Fads2) has been proposed as a strategy to enhance endogenous production of LC-PUFA and VLC-PUFA under intensive farming conditions. This study aimed at investigating the nutritional regulation of genes involved in the biosynthesis of VLC-PUFA (elovl4 isoforms a and b) and LC-PUFA (fads2, elovl5) in Sparus aurata and Solea senegalensis post-larvae fed three inert micro-diets with graded concentrations of dietary LC-PUFA by using different combinations of fish oil and soya oil. The effect of dietary LC-PUFA on survival, growth and fatty acid composition was also examined. The results denoted that, while no effects were observed in survival, fish fed the diet with the highest LC-PUFA content during 30 d showed a higher total length and wet weight. Gene expression results showed that fads2, elovl5, elovl4a and elovl4b can be regulated by dietary LC-PUFA content. Remarkably, our results denoted a differential elovl4 nutritional regulation associated to each species. The head is the body part studied with the highest elovl4 transcripts in both fish species.

Very long‐chain fatty acids (VLC‐FA) play critical roles in neural tissues during early development of vertebrates. However, studies on VLC‐FA in fish are scarce. Biosynthesis of VLC‐FA is mediated by elongation of very long‐chain fatty acid 4 (Elovl4) proteins and, consequently, the complement and activity of these enzymes determines the capacity that a given species has for satisfying its physiological demands, in particular for the correct development of neurophysiological functions. The present study aimed to characterize and localize the expression of elovl4 genes from Sparus aurata and Solea senegalensis, as well as to determine the function of their encoded proteins. Results confirmed that both fish possess two distinct elovl4 genes named elovl4a and elovl4b. Functional assays demonstrated that both Elovl4 isoforms had the capability to elongate long‐chain (C20‐24), both saturated (SFA) and polyunsaturated (PUFA), fatty acid precursors to VLC‐FA. In spite of their overlapping activity, Elovl4a was more active in VLC‐SFA elongation, while Elovl4b had a preponderant elongation activity towards n‐3 PUFA substrates, particularly in S. aurata, being additionally the only isoform capable of elongating docosahexaenoic acid (DHA). A preferential expression of elovl4 genes was measured in neural tissues, being elovl4a and elovl4b mRNAs mostly found in brain and eyes, respectively. Importantly, these findings contribute to a better understanding of the VLC‐FA biosynthetic pathway and their physiological role in marine teleosts, specially during early development, when these compounds accumulate in rapidly forming neural tissues

The genus Artemia Leach, 1819 is a cosmopolitan halophilic crustacean, consisting of bisexual species and obligate parthenogenetic populations. Asia is rich in Artemia biodiversity. More than 530 Artemia sites have been recorded from this area and more than 20 species/subspecies/variety names have been used for them. There exist various problems in the nomenclature, identification, and phylogenetic status of Artemia native to Asia, which are discussed in this paper.

Long-chain polyunsaturated fatty acids (LC-PUFA) have been extensively studied in aquaculture due to their importance for survival and development in teleosts. However, very long-chain polyunsaturated fatty acids (VLC-PUFA) have been practically unexplored within the aquaculture scenario. VLC-PUFA, although always present in small amounts, can be pivotal for the correct development and function of tissues such as retina, brain and gonads of vertebrates including fish. This study aimed at determining the temporal expression patterns of genes involved in the biosynthesis of VLC-PUFA (elovl4a, elovl4b) and their precursors, LC-PUFA, (fads2, elovl5) during the early ontogeny of Solea senegalensis and Sparus aurata. Furthermore, we investigated the nutritional regulation of these genes in early life-cycle stages of fish fed low and high LC-PUFA diets consisting of non-enriched and enriched live preys (Brachionus plicatilis and Artemia franciscana), respectively. The effect of dietary LC-PUFA on growth and fatty acid composition was also examined. The results obtained during early development reveal that all genes studied are expressed before the hatching stage. There is a consistency between the timing at which retinogenesis occurs in both species and an increase of the expression of the two elovl4 responsible for the synthesis of VLC-PUFA. The results obtained in nutritional assays for both species suggest that the expression of the two isoforms of elovl4 (isoform a in early larvae, and b in late larvae) can be regulated positively according to the dietary content of LC-PUFA in early stages, which could activate the VLC-PUFA biosynthesis even during short-term feeding periods (seven days). The body part analysis in late larvae of both species revealed that both isoforms of elovl4 are expressed preferentially in the head. This can be associated to their highest presence in the neural and visual tissues.

Very long-chain (>C24) polyunsaturated fatty acids (VLC-PUFA), although present in small amounts, play important roles for the correct development and functionality of neural tissues, especially during early development of vertebrates [1]. However, studies on VLC-PUFA in fish are scarce. Their biosynthesis, mediated by elongation of very long-chain fatty acid 4 (Elovl4) proteins, is substrate-dependent. So, shorter fatty acid precursors, i. e. long-chain (C20-24) polyunsaturated fatty acids (LC-PUFA), are required. These nutrients are mostly incorporated by the diet and their bioavailability can determine the capacity of Elovl4 for satisfying the physiological VLC-PUFA demands in marine fish [2]. Thus, nutritional regulation of Elovl4, as well as other elongase and desaturase genes involved in LC-PUFA biosynthesis (Elovl5, Fads2) has been proposed as a strategy to enhance endogenous production of LC-PUFA and VLC-PUFA in fish farming [2]. This study aimed at investigating the nutritional regulation of genes involved in the biosynthesis of VLC-PUFA (elovl4a, elovl4b) and LC-PUFA (fads2, elovl5) in early life-cycle stages (larvae and post-larvae) of Sparus aurata and Solea senegalensis fed diets adapted to each development stage, live prey for larvae and microdiets for post-larvae, with a variable content in VLC-PUFA precursors, i.e. LC-PUFA. The results denoted that fads2, elovl5, elovl4a and elovl4b genes can be regulated by dietary LC-PUFA content. It is important to highlight that elovl4a and elovl4b genes, strongly expressed in neural tissues of both fish species, were differently regulated according to the species-specific VLC-PUFA putative needs associated with each early life-stage and the LC-PUFA dietary availability. These results can help to elucidate the molecular mechanism controlling the VLC-PUFA biosynthesis and their species-specific requirements along of the marine fish development. Thus, this study opens the possibility to incorporate successfully alt

The fast and remarkable growth of global aquaculture in recent years has created new challenges, such as guaranteeing a sustainable supply of raw materials used for aquafeed formulation. Gammarids are low-trophic crustaceans with an increasing interest in aquaculture due to their high nutritional profiles and their capacity to grow under high-density conditions. Moreover, gammarids have the ability to thrive on a wide range of sidestreams while accumulating relatively high levels of long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA). In the present study, juveniles of the marine gammarid Gammarus locusta were cultured at four different temperatures (5°C, 10°C, 15°C, and 20°C) for 21 days and fed three diets, including the seaweed Fucus sp. as control, and carrot leaves and coconut flesh representing two agri-food industry sidestreams. Our results indicate that both the survival and biomass of G. locusta were highly affected by diet, with coconut showing the lowest growth performance. The temperature had no effect on biomass, although high temperature (20°C) resulted in a decrease in survival. The effects of temperature on the gammarid fatty acids were not evident, with diet being the main modulator of the profiles. Furthermore, the results also reveal that the Fucus sp. diet was associated with relatively high percentages of n-3 and n-6 LC-PUFA. Interestingly, essential LC-PUFA such as eicosapentaenoic (20:5n-3, EPA) and docosahexaenoic (22:6n-3, DHA) acids were detected in gammarids fed on either Fucus sp. or any of the sidestreams irrespectively of their presence in the diets. These results suggest an ability of G. locusta for LC-PUFA biosynthesis (trophic upgrading) and/or retention, making this species a promising candidate for the production of high-value ingredients for aquafeeds.

[EN]: Certain marine invertebrates have some capacity to synthesize long-chain polyunsaturated fatty acids (LC-PUFA), essential nutrients for animals. Such ability makes them as ideal candidates to apply principles of Circular Economy through which waste materials of low nutritional value can be used for the production of high value biomass that can be utilized as aquafeed ingredients. The molecular and functional characterization of enzymes involved in the biosynthesis of LC-PUFA is a key step to establish the potential of aquatic invertebrates to apply the above strategy. Among its objectives, the IMPROMEGA project aims to explore the LC-PUFA biosynthetic capacity of polychaetes and crustaceans like gammarids and copepods. The most relevant results are presented herein., [ES]: Algunos invertebrados marinos tienen la capacidad para la síntesis de ácidos grasos poliinsaturados de cadena larga, esenciales para los animales. Ello los convierte en candidatos ideales para aplicar los principios de la Economía Circular, a través del reciclaje de materiales de desecho de bajo valor nutricional, generando biomasa de alto valor nutritivo susceptible de ser utilizada en alimentación acuícola. La caracterización molecular y funcional de enzimas implicados en la síntesis de ácidos grasos es el primer paso para definir el potencial de los diferentes organismos como generadores netos de ácidos grasos esenciales. El proyecto IMPROMEGA contempla esta caracterización en poliquetos, así como crustáceos gamáridos y copépodos. Se presentan aquí los resultados más destacados.

[EN]: Gammarids are arising as promising candidates for feed formulation in aquaculture due to their capacity to be fed on a wide range of sidestreams while maintaining adequate levels of long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA). The main goal of this work was to elucidate how different conditions (temperature and diet) modulate the expression of LC-PUFA biosynthesis and energy metabolism related genes. Individuals of the marine gammarid Gammarus locusta were fed on different diets (3) and reared at several temperatures (4), their RNA was sequenced, and the raw data were used to build a reference transcriptome for differential gene expression (DGE) analysis. Genes related to LC-PUFA and energy metabolism were downregulated in the gammarids fed low LC-PUFA diets and reared at suboptimal temperatures., [ES]: Los gamáridos son prometedores candidatos para la formulación de pienso en acuicultura debido a su capacidad para alimentarse de una amplia gama de subproductos mientras mantienen niveles adecuados de ácidos grasos poliinsaturados de cadena larga (≥C20) (LC-PUFA). El objetivo principal de este trabajo fue dilucidar cómo diferentes condiciones (temperatura y dieta) afectan a la expresión de genes relacionados con la biosíntesis de LC-PUFA y el metabolismo energético. Ejemplares del gamárido marino Gammarus locusta se alimentaron con diferentes dietas (3), a distintas temperaturas (4), se secuenció su ARN y los datos se usaron para construir un transcriptoma de referencia para el análisis de la expresión génica diferencial (DGE). Los resultados indican que los genes relacionados con LC-PUFA y el metabolismo energético están subexpresados en los gamáridos alimentados con dietas pobres en LC-PUFA y cultivados a temperaturas subóptimas

Eurasian brine shrimp (genus Artemia) have closely related sexual and asexual lineages of parthenogenetic females, which produce rare males at low frequencies. Although they are known to have ZW chromosomes, these are not well characterized, and it is unclear whether they are shared across the clade. Furthermore, the underlying genetic architecture of the transmission of asexuality, which can occur when rare males mate with closely related sexual females, is not well understood. We produced a chromosome-level assembly for the sexual Eurasian species Artemia sinica and characterized in detail the pair of sex chromosomes of this species. We combined this new assembly with short-read genomic data for the sexual species Artemia sp. Kazakhstan and several asexual lineages of Artemia parthenogenetica, allowing us to perform an in-depth characterization of sex-chromosome evolution across the genus. We identified a small differentiated region of the ZW pair that is shared by all sexual and asexual lineages, supporting the shared ancestry of the sex chromosomes. We also inferred that recombination suppression has spread to larger sections of the chromosome independently in the American and Eurasian lineages. Finally, we took advantage of a rare male, which we backcrossed to sexual females, to explore the genetic basis of asexuality. Our results suggest that parthenogenesis is likely partly controlled by a locus on the Z chromosome, highlighting the interplay between sex determination and asexuality.

The fast and remarkable growth of global aquaculture in recent years has created new challenges, such as guaranteeing a sustainable supply of raw materials used for aquafeed formulation. Gammarids are low-trophic crustaceans with an increasing interest in aquaculture due to their high nutritional profiles and their capacity to grow under high-density conditions. Moreover, gammarids have the ability to thrive on a wide range of sidestreams while accumulating relatively high levels of long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA). In the present study, juveniles of the marine gammarid Gammarus locusta were cultured at four different temperatures (5°C, 10°C, 15°C, and 20°C) for 21 days and fed three diets, including the seaweed Fucus sp. as control, and carrot leaves and coconut flesh representing two agri-food industry sidestreams. Our results indicate that both the survival and biomass of G. locusta were highly affected by diet, with coconut showing the lowest growth performance. The temperature had no effect on biomass, although high temperature (20°C) resulted in a decrease in survival. The effects of temperature on the gammarid fatty acids were not evident, with diet being the main modulator of the profiles. Furthermore, the results also reveal that the Fucus sp. diet was associated with relatively high percentages of n-3 and n-6 LC-PUFA. Interestingly, essential LC-PUFA such as eicosapentaenoic (20:5n-3, EPA) and docosahexaenoic (22:6n-3, DHA) acids were detected in gammarids fed on either Fucus sp. or any of the sidestreams irrespectively of their presence in the diets. These results suggest an ability of G. locusta for LC-PUFA biosynthesis (trophic upgrading) and/or retention, making this species a promising candidate for the production of high-value ingredients for aquafeeds.

Determining how and how often asexual lineages emerge within sexual species is central to our understanding of sex-asex transitions and the long-term maintenance of sex. Asexuality can arise “by transmission” from an existing asexual lineage to a new one through different types of crosses. The occurrence of these crosses, cryptic sex, variations in ploidy, and recombination within asexuals greatly complicates the study of sex-asex transitions, as they preclude the use of standard phylogenetic methods and genetic distance metrics. In this study we show how to overcome these challenges by developing new approaches to investigate the origin of the various asexual lineages of the brine shrimp Artemia parthenogenetica. We use a large sample of asexuals, including all known polyploids, and their sexual relatives. We combine flow cytometry with mitochondrial and nuclear DNA data. We develop new genetic distance measures and methods to compare various scenarios describing the origin of the different lineages. We find that all diploid and polyploid A. parthenogenetica likely arose within the past 80,000 years through successive and nested hybridization events that involved backcrosses with different sexual species. All A. parthenogenetica have the same common ancestor and therefore likely carry the same asexuality gene(s) and reproduce by automixis. These findings radically change our view of sex-asex transitions in this group and show the importance of considering scenarios of asexuality by transmission. The methods developed are applicable to many other asexual taxa.

[ES] Los estudios sobre nutrición lipídica en piscicultura marina se han centrado en el suministro de ácidos grasos esenciales (AGE) en niveles altos para cumplir con los requisitos de supervivencia, crecimiento y desarrollo de los peces. Sin embargo, los ácidos grasos poliinsaturados de cadena muy larga (VLC-PUFA, más de 24 C) prácticamente no han sido explorados en el escenario de la acuicultura. Los VLC-PUFA, aunque presentes en muy poca cantidad, podrían ser fundamentales para el correcto desarrollo y funcionalidad de tejidos como la retina, el cerebro o las gónadas. El objetivo de este trabajo es contrastar a nivel interespecífico el patrón de expresión de los genes que codifican para las enzimas limitantes durante el proceso de biosíntesis de LC-PUFA (Elovl5, Fads2) y VLC-PUFA (Elovl4a, Elovl4b) analizando su regulación nutricional en postlarvas de S.aurata y S.senegalensis. Este proceso se ha estudiado en respuesta a una situación variable de biodisponibilidad de LC-PUFA, mediante el uso de micro-piensos inertes en cuya composición se ha variado el porcentaje de aceite de pescado (FO) en 33, 50 y 100%. Los resultados obtenidos proporcionan una visión integral de la regulación nutricional de estos genes en respuesta al contenido en aceite de pescado presente en la dieta. Todo ello, teniendo en cuenta las particularidades existentes en el mecanismo biosintético de PUFA asociado a cada especie. Además se resaltan las diferencias de expresión en función del tejido analizado., [EN] Studies on lipid nutrition in marine fish farming have focused on supplying essential fatty acids (EFA) at high levels to meet requirements for survival, growth and development of fish. However, very long chain polyunsaturated fatty acids (VLC-PUFA, more than 24 C) have been practically unexplored within the aquaculture scenario. VLC-PUFA, although present in very little amount, could be pivotal for the correct development and functionality of tissues like retina, brain and gonads. The aim of this work is to contrast the interspecific expression pattern of the genes encoding for the limiting enzymes in the biosynthesis of LC-PUFA (Elovl5, Fads2) and VLC-PUFA (Elovl4a, Elovl4b), analyzing their nutritional regulation, in postlarvae of S. aurata and S. senegalensis. This process is assessed in response to a variable situation of bioavailability of LC-PUFA, through the use of inert micro-feeds with different content (33, 50 and 100 %) of fish oil (FO). The results provide an integral vision of the nutritional regulation of these genes in response to the FO content present in the diet, depending on the particular PUFA biosynthetic mechanism of each species. Moreover, the differences as a function of the analyzed tissue are revealed.

This work brings together the view of different specialists in the areas of larviculture, physiology, ecology, nutrition and animal health, regarding how to deal with the aquaculture farming of species with complex life cycles in a multidisciplinary way, using as models the octopus and the muricid C. concholepas, with the aim of reducing the gap between the experimental and the industrial culture of species that are relevant for the diversification of aquaculture, particularly in Chile. Although these species are similar in their difficulty to reach the terminal planktonic phase prior to juvenile, they differ in the bottlenecks they have to overcome to reach it. Relevant aspects of study to achieve juvenile production from early life stages rearing, whether for repopulation or for ongrowing, are as follows: (i) Replacement or supplementation of live diets with inert diets to achieve significant survival values over the first stages of life. (ii) Physiological approaches to establish cultivation conditions evaluating the individual responses to several rearing conditions, specially the interaction between temperature, dissolved oxygen and acidity. Studies of urgent character due to the global warming scenario. (iii) Genomic studies associated with the effect of ontogenetic development, environment, health and nutrition on gene expression to understand, in an integrated way, the key processes for the development and growth of immature stages. (iv) Studies on the control of reproduction, the quality control of the ova, the genetic structure of reproductive populations and the characterization of diseases are also necessary to achieve efficient hatchery technologies.

Octopus vulgaris rearing/production presents several problems, mainly during the first stages, from eggs incubation to paralarvae rearing. In the last years, several research groups have been doing an effort to produce O. vulgaris in aquaculture focused on larval rearing phase, in order to solve these bottlenecks. In this sense, the present study aims to analyse the effect of different temperatures on common octopus embryonic development from one single female brood; as well as, larval viability and biomarkers of growth, physiological stress, antioxidant defences and neuronal activity (RNA/DNA, HSP70, GST and AChE, respectively). O. vulgaris eggs were incubated from stage XV to hatchlings at 19ºC and 22ºC, and then were maintained at room temperature (22±1ºC) for 14 days. Survival, specific growth rate, biomass and dry weight were measured over time. Samples from 0 and 14 days were taken in order to analyse biomarkers individually. Only HSP70 was analysed using a pool of 7-8 paralarvae. The results showed differences between temperatures in terms of survival and specific growth rate. RNA/DNA ratios and GST (0 and 14 days), and HSP70 (0, 7 and 14 days) showed differences between ages at different temperatures. No significant differences were found in AChE activity between groups (age and temperatures). The results point out at the RNA/DNA ratio, GST and HSP70 as sensitive biomarkers for growth, thermal stress and antioxidant defences in paralarvae. However, growth and temperature did not alter the neurotransmission system of the paralarvae.