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Devil firefish (Pterois miles), a member of Scorpaenidae family, is one of the most successful marine non-native species, dominating around the world, that was rapidly spread into the Mediterranean Sea, through the Suez Canal, originating from the Indian Ocean. Even though lionfishes (Scorpaenidae) are identified among the most prosperous marine invaders, within this taxonomic group, the genomic resources are scant, while reference genome assemblies are totally absent. Here, we built and analyzed the first reference genome assembly ofP. milesand explored its evolutionary background. The resulting genome assembly consisted of 660 contigs and scaffolds (N50 = 14,5 Mb) with a total size of about 902 Mb, while delivering 98% BUSCO completeness. We identified and described the large amount of transposable elements present in the genome and based on genomic data we constructed the first teleost phylogeny which includes a member of genusPterois. The high-quality and contiguityde novogenome assembly built herein provides a valuable resource for future studies in species’ biology and ecology, lionfish phylogeny, the influence of transposable elements on the evolution of vertebrate genomes and fish toxins evolution.

Exploring the genetic background of successful invasive phenotypes is essential in understanding their underlying mechanisms. Lionfish (Scorpaenidae) are identified among the most prosperous invaders spread along the coastlines of the Atlantic and recently the Mediterranean Sea. However, within this family, the genomic resources are depauperate while reference genome assemblies are totally absent. In this study, we focus on the devil firefish, Pterois miles (Bennett, 1828), one of the most successful invasive species across the coasts of the Mediterranean Sea. We sequenced the genome of P. miles using Oxford Nanopore Technology (ONT) and Illumina reads for building the reference genome. The resulting assembly consisted of 660 contigs and scaffolds (N50 = 14,5 Mb) with a total size of about 902 Mb, while delivering 98% BUSCO completeness. The high-quality de novo genome assembly constructed here is the first one among the members of Scorpaenidae and establishes the outset for further exploring this family and the biology of venomous and invasive species.

The Tetraodontidae family encompasses several species which attract scientific interest in terms of their ecology and evolution. The silver-cheeked toadfish (Lagocephalus sceleratus) is a well-known “invasive sprinter” that has invaded and spread, in less than a decade, throughout the Eastern and part of the Western Mediterranean Sea from the Red Sea through the Suez Canal. In this study, we built and analysed the first near-chromosome level genome assembly of L. sceleratus and explored its evolutionary landscape. Through a phylogenomic analysis, we positioned L. sceleratus closer to T. nigroviridis, compared to other members of the family, while gene family evolution analysis revealed that genes associated with the immune response have experienced rapid expansion, providing a genetic basis for studying how L. sceleratus is able to achieve highly successful colonisation. Moreover, we found that voltage-gated sodium channel (NaV 1.4) mutations previously connected to tetrodotoxin resistance in other pufferfishes are not found in L. sceleratus, highlighting the complex evolution of this trait. The high-quality genome assembly built here is expected to set the ground for future studies on the species biology.

The Mediterranean Triton Charonia seguenzae (Aradas & Benoit, 1870) is an endangered marine gastropod. Re-establishment of C. seguenzae populations in the depleted habitats requires knowledge of its biology and breeding in captivity. Temperature has been recorded to affect the development in marine gastropods. The present study aims to describe the encapsulated development and study the effect of three temperature regimes, that the embryos are exposed to in the wild (17, 20, 23οC), on it. At the stage of morula (7th Day After Deposition – DAD) 180 egg capsules were separated in three groups of 60 capsules. One group remained at 23 °C and the other two were acclimated at 20 and 17 °C. Two capsules were sampled randomly from each temperature setup (every day during the first 5 days, D1-D5, every other day from D7 to D17 and every other two days from D20 to eclosion), opened and the eggs, embryos or larvae were photographed under stereoscope. Stages of development and shape were assessed and dimensions were measured from microphotographs. All developmental stages were described in relation to temperature and time. At 23οC eclosion of free swimming veligers occurred 49 DAD, 17 days faster than the embryonic development at 20οC. Eclosion at 17 οC was not observed up until the 74th DAD when the last sampling was conducted. An increased amount of larval deformities was observed at 17οC reaching 94% during the last sampling (D74), while at eclosion only 4 and 3% of the hatching larvae were deformed at 20 and 23 οC respectively. In this study temperature appears as a key factor during the development of the marine gastropod Charonia seguenzae, affecting the survival and developmental rate. Although temperature affected the size of intermediate stages, the size of free swimming veligers at 20 and 23 οC did not differ.

Increased atmospheric CO 2 produced by anthropogenic activities will be absorbed by the oceans over the next century causing ocean acidification and changes in the seawater carbonate chemistry. Elevated CO 2 causes sublethal physiological and behavioural responses on the locomotion and foraging behaviour of marine organisms. This study aims to investigate the independent and synergistic effects of long term exposure to low pH and increased temperature on the feeding behaviour of two gastropod species, Hexaplex trunculus and Nassarius nitidus , both in adults and juveniles. Gastropods were maintained under controlled conditions of temperature (ambient = 20°C, increased = 23°C) and pH (ambient = 8, low = 7.6) for 2.5 years. The percentage of animals which successfully reached their food, the response time until gastropods began moving, the total duration until they reached food and the total distance covered, were measured. Speed and path index (i.e how straightforward the movement is) were estimated as means of foraging efficiency. Increased temperature (under ambient pH) resulted in faster responses, a shorter duration until food was reached and a higher speed in H. trunculus adults. H. trunculus (both adults and juveniles) were less successful in reaching their food source under low pH and ambient temperature in comparison to all other treatments. The response time, duration, speed and path index were not affected by low pH (at ambient or increased temperature) for H. trunculus adults and juveniles, as well as for N. nitidus . The foraging performance of juveniles hatched and developed under low pH (either at ambient or increased temperature) was more effective than adults of the same species, thus indicating a degree of acclimation. Also, the scavenger N. nitidus was more successful and responded faster in reaching carrion than the predator H. trunculus , whereas no significant effects were observed for N. nitidus under low pH.

The reproductive behavior of the gastropod Charonia seguenzae (Aradas & Benoit, 1870) was studied through the description of 19 copulation and 21 egg laying events of 134 wild individuals. Findings in the present study regarding a part of the reproduction temperature range (20 to 23oC) and the demonstration of maternal care provided important information on their biology, behavior and ecology. Furthermore, observed polyandry by the females and collaborative care of embryonic sacks, were two aspects of the species reproductive biology that pose new questions both at ecological and evolutionary level.

Sex differentiation is a puzzling problem in fish due to the variety of reproductive systems and the flexibility of their sex determination mechanisms. The Sparidae, a teleost family, reflects this remarkable diversity of sexual mechanisms found in fish. Our aim was to capture the transcriptomic signature of different sexes in two protogynous hermaphrodite sparids, the common pandora Pagellus erythrinus and the red porgy Pagrus pagrus in order to shed light on the molecular network contributing to either the female or the male phenotype in these organisms. Through RNA sequencing, we investigated sex-specific differences in gene expression in both species’ brains and gonads. The analysis revealed common male and female specific genes/pathways between these protogynous fish. Whereas limited sex differences found in the brain indicate a sexually plastic tissue, in contrast, the great amount of sex-biased genes observed in gonads reflects the functional divergence of the transformed tissue to either its male or female character. Α common “crew” of well-known molecular players is acting to preserve either sex identity of the gonad in these fish. Lastly, this study lays the ground for a deeper understanding of the complex process of sex differentiation in two species with an evolutionary significant reproductive system.

Veríssimo, Ana ... et al.-- 15 pages, 3 figures, 3 tables, supporting information https://dx.doi.org/10.1111/zsc.12224, The alpha taxonomy of the globally distributed shark genus Squalus has been under intense investigation recently, and many new species have been described over the last decade. However, taxonomic uncertainty remains about several taxa. Without consistent nomenclature and the ability to reliably distinguish between the different Squalus species, basic data collection, downstream conservation and management efforts are seriously compromised. To aid in clarifying the taxonomic status of Squalus species in the eastern Atlantic and Mediterranean, we assessed species diversity at the molecular level and evaluated the consistency in species identification in the region. Samples from all nominal Squalus species recognized in the above regions were collected in an international effort and sequenced for regions of the mitochondrial COI and ND2 genes. These data were further analysed alongside publicly available sequences, including 19 of the 26 Squalus species globally recognized, to compare the regional genus-level diversity with that found elsewhere. Our results confirm inconsistent species identification in the eastern Atlantic and Mediterranean Squalus, particularly concerning S. blainville and S. megalops, and reinforce the need to revise the status of S. megalops and S. mitsukurii as they may include several distinct species distributed around the world. The status of S. blainville is also discussed in the light of the current findings and its problematic taxonomic history, Partial funding for this project was provided by the Systematic Research Fund. AV was funded by Fundação para a Ciência e Tecnologia (SFRH/BPD/77487/2007) under ‘Programa Operacional Capital Humano’ cofinanced by the Social European Fund and by Portuguese funds (MCTES). This work was also supported (in part) by the New Zealand National Institute of Water and Atmospheric Research Ltd Core Funded Coasts & Oceans Programme 2: Biological Resources subcontract for fundamental knowledge of marine fish biodiversity with the Museum of New Zealand Te Papa Tongarewa

The alpha taxonomy of the globally distributed shark genus Squalus has been under intense investigation recently, and many new species have been described over the last decade. However, taxonomic uncertainty remains about several taxa. Without consistent nomenclature and the ability to reliably distinguish between the different Squalus species, basic data collection, downstream conservation and management efforts are seriously compromised. To aid in clarifying the taxonomic status of Squalus species in the eastern Atlantic and Mediterranean, we assessed species diversity at the molecular level and evaluated the consistency in species identification in the region. Samples from all nominal Squalus species recognized in the above regions were collected in an international effort and sequenced for regions of the mitochondrial COI and ND2 genes. These data were further analysed alongside publicly available sequences, including 19 of the 26 Squalus species globally recognized, to compare the regional genus-level diversity with that found elsewhere. Our results confirm inconsistent species identification in the eastern Atlantic and Mediterranean Squalus, particularly concerning S.blainville and S.megalops, and reinforce the need to revise the status of S.megalops and S.mitsukurii as they may include several distinct species distributed around the world. The status of S.blainville is also discussed in the light of the current findings and its problematic taxonomic history.

This article examines China’s strategy pertaining to their ‘String of Pearls’. China has strengthened their relationships through financial support and construction of infrastructure within countries that have a history of political instability. The focus is on maritime superiority with each ‘pearl’ can serve as both an economic and military hub for China. China has caught the attention of the United States with their increased military spending, increased support of local governments, and increased influence in Africa with the aid to dictators undoing the progress of democracy attempts.

The structural features of complementary liposomes and factors favoring formation of multicompartment systems are investigated. Specifically, liposomal formulations consisting of PEGylated unilamellar liposomes with guanidinium moieties located at the distal end of polyethylene glycol (PEG) chains interact with complementary multilamellar liposomes bearing phosphate moieties. Furthermore, the number of PEG chains attached to the unilamellar interface of the liposomes is enhanced by incorporating PEGylated cholesterol in their bilayer. While molecular recognition of the liposomes is the driving force for initiating multicompartmentalization, it is the enhanced PEGylation at the liposomal interface that synergistically promotes fusion resulting in large and well-formed multicompartment systems. A mechanism is proposed according to which initial adhesion of the liposomes, followed by reorganization of their membrane lipids, leads to giant bilayer aggregates incorporating large liposomes.

WOS: 000392316000003, This contribution forms part of a series of collective articles published regularly in Mediterranean Marine Science that report on new biodiversity records from the Mediterranean basin. The current article presents 51 geographically distinct records for 21 taxa belonging to 6 Phyla, extending from the western Mediterranean to the Levantine. The new records, per country, are as follows: Spain: the cryptogenic calcareous sponge Paraleucilla magna is reported from a new location in the Alicante region. Algeria: the rare Atlanto-Mediterranean bivalve Cardium indicum is reported from Annaba. Tunisia: new distribution records for the Indo-Pacific lionfish Pterois miles from Zembra Island and Cape Bon. Italy: the ark clam Anadara transversa is reported from mussel cultures in the Gulf of Naples, while the amphipod Caprella scaura and the isopods Paracerceis sculpta and Paranthura japonica are reported as associated to the -also allochthonous- bryozoan Amathia verticillata in the Adriatic Sea; in the latter region, the cosmopolitan Atlantic tripletail Lobotes surinamensis is also reported, a rare finding for the Mediterranean. Slovenia: a new record of the non-indigenous nudibranch Polycera hedgpethi in the Adriatic. Greece: several new reports of the introduced scleractinian Oculina patagonica, the fangtooth moray Enchelycore anatina, the blunthead puffer Sphoeroides pachygaster (all Atlantic), and the lionfish Pterois miles (Indo-Pacific) suggest their ongoing establishment in the Aegean Sea; the deepest bathymetric record of the invasive alga Caulerpa cylindracea in the Mediterranean Sea is also registered in the Kyklades, at depths exceeding 70 m. Turkey: new distribution records for two non-indigenous crustaceans, the blue crab Callinectes sapidus (Atlantic origin) and the moon crab Matuta victor (Indo-Pacific origin) from the Bay of Izmir and Antalya, respectively; in the latter region, the Red Sea goatfish Parupeneus forsskali, is also reported. Lebanon: an array of records of 5 alien and one native Mediterranean species is reported by citizen-scientists; the Pacific jellyfish Phyllorhiza punctata and the Indo-Pacific teleosteans Tylerius spinosissimus, Ostracion cubicus, and Lutjanus argentimaculatus are reported from the Lebanese coast, the latter notably being the second record for the species in the Mediterranean Sea since 1977; the native sand snake-eel Ophisurus serpens, rare in the eastern Mediterranean, is reported for the first time from Lebanon, this being its easternmost distribution range; finally, a substantial number of sightings of the lionfish Pterois miles further confirm the current establishment of this lessepsian species in the Levantine., COST (European Cooperation in Science and Technology) Action TD1209 Alien Challenge project; East and South European Network for Invasive Alien Species - a tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS) (EEA) project [33-51/30.06.2015]; EEA GRANTS; Public Investments Programme (PIP) of the Hellenic Republic; Cretaquarium, Nadhera Babali would like to thank Mr Nabil Hadjadji and Mr Mhamed Laid for taking pictures of the specimen of Cardium indicum during collection, which helped with identification of the collection date and site, as well as Mr Samuel Iglesias for valuable guidance. Gianna Servello and Fabio Crocetta acknowledge the study of the alien species recorded in the Italian Seas that was partially funded by the COST (European Cooperation in Science and Technology) Action TD1209 Alien Challenge (GS) and the East and South European Network for Invasive Alien Species - a tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS) (EEA funded: Contract No. -33-51/30.06.2015) (FC) projects. Francesco Tiralongo is grateful to the fishermen of the vessel "Oreste" (3288) who caught the specimen of Lobotes surinamensis, for providing the information and the picture. The reports of Caulerpa cylindracea, Oculina patagonica, and Enchelycore anatina were conducted along a survey in the Aegean Sea within the framework of the MARISCA project, co-funded (85%) by EEA GRANTS, 2009-2014, and the Public Investments Programme (PIP) of the Hellenic Republic (15%). Thomas Hasiotis and Stelios Katsanevakis thank Kostas Tsiamis for his comments on an earlier draft of their manuscript. Michail Ragkousis and Vasilis Gerovasileiou are thankful to Nina Premezzi and Ioannis Havakis who provided information and photos about the later record of E. anatina. Aspasia Sterioti sincerely thanks Cretaquarium for support and funding, G. Vardanis for the transportation and photo of the species and C.K. Doxa for the photo of the species. Fabio Crocetta and Michel Bariche acknowledge Messrs T. Assal, M. Ali Ibrahim, J. Bacha, J. Bahout, V. Bayrakdarian, D. Captan, K. Greig, M. Hado, M. Hayek, J.-P. Massoud K. Merhabi, W. Nini, H. Rifai, N. Saidi, E. Saliba, I. Sidawi, N. Weber, and several other fishermen and scuba divers who kindly provided records, photographs and videos of the reported animals from Lebanon. Finally, thanks are due to all anonymous reviewers for critical reading and providing helpful and constructive comments on the included articles.

This study presents data on the eiect of carotenoid sources on skin coloration of red porgy (Pagrus pagrus). Three experiments were conducted: in the ¢rst, ¢sh were fed an astaxanthin (Naturose s )-supplemented diet, while the second ¢sh received diets supplemented with b-carotene (Rovimix b-caroten s )o r

Enteromyxum leei (Myxozoa) has been identified as the aetiological agent of morbidity and mortality in captive feral parrotfish, Sparisoma cretense held at the facilities of Cretaquarium, the public aquarium of the Hellenic Centre for Marine Research in Crete. The parasite caused substantial mortality to the parrotfish exceeding 60% over a period of 3.5 months. Here we describe the course of disease, the effects of the parasite on the host based on histopathological observations and we provide morphological and molecular data on the parasite.

Biodegradable oligolysine and oligoarginine-type homopeptides functionalized with PEG of two different molecular weights interact with insulin, at physiological pH, affording complexes studied by dynamic light scattering, ζ-potential, circular dichroism, FTIR spectroscopy, and isothermal titration calorimetry (ITC). High levels of insulin complexation efficiencies (>99.5%) were determined for all derivatives. FTIR spectra suggest that the positively charged homo-oligopeptide derivatives interact with B chain C-terminus of insulin leading to the formation of nanoparticles than can be traced even at low oligopeptide/insulin molar ratios. The ITC profiles are complex, displaying significant endothermic and exothermic contributions. Oligoarginine-type derivatives exhibit the strongest interactions, while PEGylation of either oligopeptide with the high molecular weight chains significantly affects the ITC profiles and leads to larger enthalpy changes. This may be attributed to PEG-induced aggregation of insulin due to the depletion attraction effect leading to the formation of stable nanocomplexes. Stabilization of complexed insulin against enzymatic degradation by trypsin and α-chymotrypsin is observed especially for the high molecular weight PEGylated arginine-based derivative. Insulin release rates in simulated intestinal fluid are controlled by the length of PEG chains and the presence of arginine end-groups. Released insulin retains its secondary structure as established by circular dichroism spectroscopy.

WOS: 000315934300018 This paper presents records extending or confirming the distribution of Mediterranean species. Three alien algae are included, namely Codium taylorii reported for the first time from the Aegean and Turkey (Izmir Gulf), Caulerpa racemosa var. cylindracea (Karpathos and Chalki Isl., Aegean Sea) and Ganonema farinosum (Karpathos Isl., Aegean Sea). As far as animals are concerned, Litarachna divergens (Acari: Hydrachnidia) was recorded (Side, Eastern Mediterranean) and represents a new amendment at genus level for Turkish fauna. Other invertebrates include alien species such as the crabs Dyspanopeus sayi (Lago Fusaro, SW Italy), Percnon gibbesi (Larnaca, Cyprus; Karpathos and Chalki Isl., Aegean Sea) and Callinectes sapidus (Voda estuary, NAV Greece), the nudibranch Aplysia dactylomela (Boka Kotorska Bay, Montenegro), the gastropod Conomurex persicus (Karpathos and Chalki Isl., Aegean Sea) and the bryozoan Electra tenella (Livorno harbour and Messina Straits area). The alien fish Siganus luridus, Siganus rivulatus, Fistularia commersonii, Sphyraena chrysotaenia and Sargocentron rubrum are also reported from the islands of Karpathos and Chalki, and Pteragogus pelycus from Heraklion Bay, Crete. In addition, new localities for four rare Mediterranean inhabitants are given: the cephalopod Thysanoteuthis rhombus (NW Sardinia) and the fish: Lampris guttatus (Calabria, S Italy), Petromyzon marinus (Gokova Bay) and Remora australis (Saronikos Gulf), while the opisthobranch gastropod Cerberilla bernadettae is reported for the first time from the E Mediterranean (Cyprus). Finally, three species of the Aegean ascidiofauna are recorded for the first time: Lissoclinum perforatum, Ciona roulei and Ecteinascidia turbinata. Furthermore, it was established that Phallusia nigra has extended its distributional range to the north of the Aegean Sea. Celal Bayar UniversityCelal Bayar University [FBE 2011/080] The contribution of the following persons is highly appreciated: Prof. Paul C. Silva (Berkeley, USA) and Prof. Michael J. Wynne (Michigan, USA) for kindly providing assistance in the study of Codium taylorii, which was supported by the Celal Bayar University (FBE 2011/080); Giuseppe Urgu for his collaboration and the photographs of the Thysanoteuthis rhombus specimen; Dr. Suat Ate and Dr. Mehmet Cengiz Deval for their assistance, and Andrea Spyrou and Fani Konstantinou for their valuable help in collecting samples of Percnon gibbesi; Spyros Michopoulos for collecting the specimens of Callinectes sapidus; the Cretaquarium aquarists for the fish maintenance and Dr Divanach, Cretaquarium scientific responsible for his collaboration.

Second generation biodegradable poly(l-lysine) dendrigrafts functionalized with 12-48 arginine end-groups interact, at physiological pH, with insulin affording dendrigraft/insulin complexes as established by dynamic light scattering, ζ-potential, circular dichroism and isothermal titration calorimetry. Binding occurs in two steps; at low dendrigraft/insulin molar ratios (or = 0.07) interaction is accompanied with the endothermic dissociation of insulin dimers, while at higher molar ratios, complexation of insulin monomers with dendrigraft derivatives occurs exothermically. High levels of insulin complexation efficiencies (99%) were determined for all derivatives. Stabilization of complexed insulin against enzymatic degradation by trypsin and α-chymotrypsin is observed especially for the highly arginine end-functionalized dendrigrafts. Insulin release rates in simulated intestinal fluid are being controlled by the number of arginine end-groups and released insulin retains its conformation.

The temperature sex determination (TSD) mechanism in the European sea bass (Dicentrarchus labrax L.) was studied in respect to: a) the TSD sensitivity during the different developmental stages; and b) the intrapopulation correlation of sex determination with the growth rate up to the end of the TSD-sensitive period. At the stage of half-epiboly, eggs from the same batch were divided into four groups and subjected to different thermal treatments: a) 15 degrees C (G15 group) and b) 20 degrees C (G20 group) up to the middle of metamorphosis stage; c) 15 degrees C up to the end of yolk-sac larval stage and subsequently to 20 degrees C (G15-5 group); and d) 15 degrees C up to the end of the preflexion stage and then to 20 degrees C (G15-10 group). At the end of the treatments, size grading was applied and four additional populations were established from the upper (L) and lower (S) size portions of the G15 and G20 populations: G15L, G15S, G20L, and G20S. During the following growing phase, all populations were subjected to common rearing conditions. The sex ratios of each population were macroscopically determined at 190-210 mm mean total length. Female incidence was significantly affected (P < 0.05) by the different thermal treatments: 66.1% in the G15, 47.1% in the G15-10, 37.6% in the G15-5, and 18.1% in the G20 group. In addition, sex ratio was correlated with the growth rate of the fish up to the end of the TSD-sensitive period, with the larger fish presenting a significantly higher (P < 0.01) female incidence than the smaller fish in both thermal regimes tested: 73.1% in G15L vs. 57% in G15S, and 36.6% in G20L vs. 22.5% in G20S group. Results provide, for the first time, clear evidence that the sea bass is sensitive to TSD during all different ontogenetic stages up to metamorphosis, and that sex ratio is correlated with the growth rate of the fish well before the differentiation and maturation of the gonads.

SUMMARYThe influence of changes in environmental temperature on the mRNA levels of myogenic regulatory factors (MRFs), i.e. MyoD and myogenin, as well as myosin heavy chain (MyHC) were studied during early larval development in rainbow trout and sea bass. Phosphoimager analysis of northern blots indicated that there is an optimum temperature for the RNA transcript levels of MRF and MyHC RNA in trout and in sea bass larvae. In the trout strain studied, the highest concentration for MRF and MyHC transcripts was found at 8°C rather than 4°C or 20°C. In European sea bass, the highest concentrations of MRF and MyHC mRNA were observed at 15-20°C rather than 13°C. Raising sea bass larvae at 15°C was associated with higher MyHC gene expression as well as a trend towards an increase in total muscle fibre number and higher growth rates after transfer at ambient temperature. Results suggest that mRNA levels of MRF and MyHC can be used to optimise early development. An experiment in which the temperature was changed illustrates the consequence of precise temporal expression of MRF genes in specifying muscle fibre number at critical stages during early development.

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To test the hypothesis that sex determination in the European sea bass (Dicentrarchus labrax L.) Can be affected by the incubating temperature during the very early developmental stages, eggs from the same batch of spontaneously spawned broodstock were divided at the stage of half-epiboly into three groups according to rearing temperature: G13 = 13 degrees C, G15 = 15 degrees C, and G20 = 20 degrees C. Temperature treatment lasted until the middle of metamorphosis (17-18 mm total length, [TL]), and, with the exclusion of water temperature, all biotic and abiotic conditions were identical for the three experimental groups. The on-growing phase was performed under ambient photoperiod and temperature conditions for all groups. Sex proportions were determined by histological examination of the gonads of fish at 308, 467, and 568 days posthatch (DPH). At 308 DPH (TL: 135-201 mm), 100% of the specimens had differentiated into males and females. A significantly higher (P < 0.01) proportion of females was found in groups G13 (72-74%) and G15 (67-73%) than in group G20 (24-28%). At the final sampling there was no statistically significant difference in body weight between the experimental groups. However, in all groups, female fish were larger than males (P < 0.001). Results provide for the first time clear evidence that temperature during the very early developmental stages is the crucial factor affecting the process of sex differentiation of the sea bass, with low rearing temperatures (13 or 15 degrees C) resulting in sex proportions consistently skewed in favor of females.