Helen Miliou

Studies on stress responses and recovery from removal in gilthead sea bream Sparus aurata (L.) using recirculated seawater system

The effects of serial cohort-removal stress on physiological responses in immature specimens of the euryhaline species, the gilthead sea bream Sparus aurata, were investigated (trial 1). In addition, physiological responses during recovery in tanks of 175 l (10.5 kg/m3) after a single (trial 2) or serial (trial 3) cohort-removal from a holding tank of 1 m3 (14 kg/m3) were examined. All trials were performed in a recirculated seawater system. Serial cohort-removal for 90 min, combined with a continuous pursuing (trial 1), caused a significant increase of plasma cortisol, glucose, osmolality, Na+, Cl− and pCO2, and a significant reduction of pH, K+ and HCO3− in the remaining fish of the holding tank. These alterations in most of the plasma parameters studied were progressive for 45–60 min and then remained almost constant. When undisturbed fish were netted and transferred (trial 2), the levels of plasma cortisol, glucose, osmolality, Cl− and Na+ initially increased, exhibiting maximum elevations at 40 min and recovering within 2 h. At the end of a serial cohort-removal after 15 min, without chasing the fish (trial 3), the levels of plasma cortisol, glucose, Na+, Cl− and K+ did not significantly differ from the control levels. However, during recovery from netting and transfer of fish disturbed by this serial cohort-removal, the levels of plasma cortisol and glucose recovered after 5 h. It is indicated that serial cohort-removal, depending on its duration, may increase the alterations in stress responses, especially the secondary ones, and prolong the extent of cortisol and glucose elevations. It was concluded, that serial cohort-removal of gilthead sea bream should be mild and short-term and could be repeated the same day allowing, however, a sufficient period for cortisol and glucose recovery.

Growth and physiological changes in scaled carp and blue tilapia under behavioral stress in mono- and polyculture rearing using a recirculated water system

Growth performance, carcass composition, liver and blood parameters ofscaled carp (C), Cyprinus carpio, and blue tilapia (T),Oreochromis aureus, reared for eight weeks in twomonoculture (100%C and 100%T) and two polyculture (60%C–40%T and40%C-60%T) conditions were investigated. In polyculture 40%C–60%T bothspecies achieved the highest levels of specific growth rate and the lowestlevels of food conversion ratio and carcass lipid content. In addition, theyexhibited the highest values of plasma pO2 and pH and the lowestvalues of plasma pCO2, cholesterol and albumin, although thedifferences among treatments were not significant in the case of tilapia.Tilapia showed significantly lower plasma Cl− levels than underthe other conditions. Carp in monoculture and tilapia in polyculture60%C–40%T had the lowest levels of specific growth rate and significantlyhigher levels of liver lipids and plasma triglycerides than in the other groups.In addition, carp in monoculture exhibited a significantly higher haematocritthan in polyculture. No significant variations among treatments were observedconcerning plasma cortisol, glucose, osmolality, Na+, K+,HCO3− andHCO3−/H2CO3 in either species.The combination of scaled carp and blue tilapia, in which blue tilapia were themain species, proved to be the best for both species. It was suggested thatgrowth and physiological changes under mono- and polyculture rearing, in anintensive system, seem to be as a result of a different state of stress relatedto fish behavior.

Bacteria associated with the sponge Spongia officinalis as indicators of contamination

Abstract A lot of micro-organisms can been found in the sponge body. In the present study, bacteria and fungi were isolated from the massive commercial sponge Spongia officinalis Linnaeus, 1759 (Porifera, Demospongiae). Samples (sponge extract and sea water) were collected from several areas of the Aegean Sea (ports, beaches, eutrophic gulf and open sea) with different levels and types of contamination. Bacteria identified in sponge extract belong to the genera Escherichia , Morganella , Proteus , Pasteurella , Aeromonas , Pseudomonas and Acinetobacter . Two fungal genera, Trichosporum and Fisarium , were identified in sponge extract. Bacterial load was greater in sponge extract than in proximal sea water, reflecting the sponge ability to concentrate bacteria in its body. The assessment of bacteria associated with the sponge S. officinalis as indicators of contamination is proposed.

The impacts of scallop dredging on sponge assemblages in the Gulf of Kalloni (Aegean Sea, northeastern Mediterranean)

Concerns have been raised on the impact of bottom-fishing activities in the shallow Gulf of Kalloni (Lesvos Island, Aegean Sea). Fishing with demersal gears was banned in 1995, but the Gulf was reopened in 1998 only for scallop dredging using the ‘‘lagamna’’ gear. Two series of samplings were done with this gear in 1998 and 1999 (October) before the beginning of scallop-fishing period (from November up to March), aiming to investigate possible changes in sponge assemblages. Sponges (Porifera) were the most abundant mesomegafaunal benthic organisms in the Gulf, besides scallops and other bivalves. Total abundance, number of species, species diversity, species richness and evenness of sponge assemblages reduced significantly from the year 1998 to 1999. The population of the excavating Cliona celata, the only infaunal sponge species found in the Gulf, decreased. Multivariate analysis on the abundance data of epibenthic sponge species revealed a clear separation of samples collected during the 2 years, indicating changes in the structure of sponge assemblages. The distinguishing species included a variety of growth forms: massive (Mycale massa, Suberites domuncula and Tethya citrina), lobose (Suberites massa, Tedania anhelans and Halichondria panicea), erect branching (Raspailia viminalis), encrusting (Crambe crambe) and cushion-shaped (Mycale contarenii and Chondrilla nuculla) sponges. Among these species, only S. massa increased its abundance in 1999. All others decreased. No significant loss of information occurred when multivariate analysis was applied to abundance data of genera or families. This comparative study demonstrated that the time interval between two consecutive scallop-fishing periods was insufficient for the recovery of sponge assemblages. It is concluded that scallop dredging causes long-term changes in the structure and biodiversity of sponge assemblages in the Gulf of Kalloni. An improved strategy of fishery management is required in future for the conservation of living resources in this Gulf. 2003 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights

Identification of the abiotic stress-related transcription in little Neptune grass Cymodocea nodosa with RNA-seq

Seagrasses exhibit vital ecological roles in the marine environment. Nevertheless, the genomic resources available for seagrasses are still scarce. In the present study, the transcriptome of Cymodocea nodosa was sequenced with a view to study the molecular mechanisms underlying abiotic stress responses. The sequenced transcriptome for the species was near-complete and a high percentage of the transcripts was computationally annotated. An experimental simulation of marine plant exposure to extreme temperature (34°C), salinity (50psu) and their combination was conducted. A dynamic transcriptome 24h response (short-term) from stress initialization was recorded. The most noteworthy alteration in gene expression was observed in heat-stressed plants. Transcripts associated with development, photosynthesis, osmotic balance and stress-response were differentially expressed, under the set experimental conditions. Results indicate a potential negative interaction of heat and osmotic stress on seagrasses transcriptome.

Effect of temperature and seasonality principal epizootiological risk factor on vibriosis and photobacteriosis outbreaks for European sea bass in Greece (1998-2013).

Our epizootiological survey was focused on bacterial diseases of European sea bass, Dicentrarchus labrax L., an important Mediterranean species for aquaculture, in Greece. Vibriosis and Photobacteriosis were the most severe bacterial diseases, located in the majority of Greek mariculture areas (Argolikos gulf, North Evoic gulf Maliakos gulf and Thesprotia Sagiada coast, Amvrakikos gulf, Aitoloakarnania Mitikas coast, Ionian island coasts) during the period 1998-2013. A database of 152 cases was formulated, from which 134 cases concerned vibriosis and photobacteriosis, while the rest outbreaks were motile aeromonas septicemia and tenacibaculosis. PCA pointed out three principal components with the following ranking order: a) temperature and seasonality, b) group of mariculture areas and average body weight, and c) case year. The results of logistic analysis showed the temperature - seasonality as the first, in ranking, and the only statistically significant epizootiolological risk factor. Contrast Test (low vs. high temperature values) also proved the significant effect of temperature (p<0.05). Vibriosis pathogen Listonella (Vibrio) anguillarum was recorded in a wide temperature range (12-260°) in the most of Greek rearing locations. In contrast, Vibriosis from rest vibria was found to a narrow temperature range, especially in Argolikos gulf, North Evoic gulf and Ionian Island coasts. Specifically, V. harveyi cases emerged at high temperatures (19-220°C), while those of V. alginolyticus and V. splendidus II at low temperatures (15-170°C). Photobacterium damselae subspecies piscicida in most of Greek rearing areas and Photobacterium damselae subspecies damselae in Argolikos gulf, North Evoic gulf and Ionian Island coasts appeared in a relatively wide range (19-250°C). However, they showed higher frequencies in warm period. The results will support an evolutionary epizootiological survey and will reinforce a preventive biosecurity program in Greek mariculture taking into consideration the temperature - seasonality factor along with the classical sanitary approach.