George Koumoundouros

Effect of water currents on the development of skeletal deformities in sea bass (Dicentrarchus labrax L.) with functional swimbladder during postlarval and nursery phase

Abstract Lordosis in reared sea bass was previously related either to the absence of swimbladder, or to bad or late inflation of this organ when damages were irreversible. Our results prove that these explanations are insufficient and that similar deformations may occur frequently in fry with functional swimbladder during the early weaning phase, if currents in tanks are higher than 10 cm s −1 .

Evidence of Temperature-Dependent Sex Determination in the European Sea Bass (Dicentrarchus labrax L.)

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.

The opercular complex deformity in intensive gilthead sea bream (Sparus aurata L.) larviculture. Moment of apparition and description

Abstract External morphology, head morphometry and osteology were used for early detection, description and heuristic study of the opercular complex abnormalities of intensively reared gilthead sea bream larvae (Sparus aurata). The first evidence of malformations were observed in larvae of 6.1 mm total length (TL). The abnormalities were fully developed during metamorphosis (11.0–22.0 mm TL), i.e., before the end of the hatchery phase. In 81.4% of the abnormal fish, the problem was unilateral with similar right/left frequency. In 85.5% of the cases, it was associated with severe foldings and twists of the operculum and/or suboperculum and rarely with an atrophy of these bones. The etiology, aquaculture applications and research targets for the erasure of skeletal malformations are discussed.

Development of a saddleback-like syndrome in reared white seabream Diplodus sargus (Linnaeus, 1758)

Depression of the dorsal profile accompanied by kyphosis and, in most of the cases, haemal lordosis was observed in reared Diplodus sargus. The ontogeny and the anatomy of deformity are presented and the probable causative factors are discussed.

Morphological malformations of the lateral line in reared gilthead sea bream (Sparus aurata L. 1758)

Abstract A general description of the morphological modifications of the lateral line in gilthead sea bream, reared under hatchery conditions, is provided. Farm-reared fish were examined and compared to wild fish. We used the presence of a pore on the specialized scales of the lateral line to determine the density and distribution of associated sensory neuromasts. The malformations of the lateral line were: zigzag with missing sector, wavy with missing sector, several scattered missing sectors, and several consecutive missing sectors. These abnormalities occurred in 71.0–86.2% of the reared fish, depending on the hatchery. They did not occur in wild fish. The possible behaviour consequences for gilthead sea bream of deficient sensory reception are considered. In addition, the suitability of these abnormalities for use as individual markers in different types of studies is proposed.

Effects of three preservation methods on the evolution of swimbladder radiographic appearance in sea bass and sea bream juveniles

Abstract Sea bass and sea bream juveniles with functional swimbladder were exposed to three methods of preservation: (a) in 10% phosphate buffered formalin, (b) at 4°C, and (c) at −25°C. They were then X-rayed daily over 10 days to evaluate the impact of these methods on the evolution of the radiographic image. All methods significantly decreased the apparent length and depth of the swimbladder, but with different intensities. Freezing had the least effect (9% and 12% reduction in bream and bass, respectively) and only during the first day of preservation. Four days of formalin fixation led to the total disappearance of this image. Preservation at 4°C led to the autolysis and putrefaction of the internal organs which was responsible for the poor images after three days. The results were discussed in terms of their use for the assessment of juvenile quality by radiography.

Developmental temperature has persistent, sexually dimorphic effects on zebrafish cardiac anatomy

Over the next century, climate change of anthropogenic origin is a major threat to global biodiversity. We show here that developmental temperature can have significant effects on zebrafish cardiac anatomy and swimming performance. Zebrafish embryos were subjected to three developmental temperature treatments (TD = 24, 28 or 32 °C) up to metamorphosis and then all maintained under common conditions (28 °C) to adulthood. We found that developmental temperature affected cardiac anatomy of juveniles and adults even eight months after the different thermal treatments had been applied. The elevation of TD induced a significant increase of the ventricle roundness in juvenile (10% increase) and male (22% increase), but not in female zebrafish. The aerobic exercise performance of adult zebrafish was significantly decreased as TD elevated from 24 to 32 °C. Gene expression analysis that was performed at the end of the temperature treatments revealed significant up-regulation of nppa, myh7 and mybpc3 genes at the colder temperature. Our work provides the first evidence for a direct link between developmental temperature and cardiac form at later life-stages. Our results also add to the emerging rationale for understanding the potential effects of global warming on how fish will perform in their natural environment.

Segmentation pattern of zebrafish caudal fin is affected by developmental temperature and defined by multiple fusions between segments: CHRISTOU et al.

Caudal-fin lepidotrichia is composed of numerous segments, which are linked to each other by intersegmental joints. During fish growth, lepidotrichia elongate by the addition of new segments at their distal margin, whereas the length of each segment remains constant after it is formed. In the present paper, we examined whether the water temperature affects the segmentation pattern of the juvenile and adult caudal fin. For this purpose, zebrafish (Danio rerio) embryos and larvae were exposed to three different temperature conditions (24°C, 28°C, and 32°C) from the pharyngula stage (1 day postfertilization [dpf]) to metamorphosis, whereas the control temperature (28°C) was applied to all the groups before and after this period. Results demonstrated that water temperature had a significant effect on the length of the segments of each lepidotrichium, at both the juvenile and adult stages. Moreover, at higher temperatures, there was a significant proximal shift of the position of the first bifurcation of the second lepidotrichium of the dorsal lobe. At all the experimental conditions, the length of proximal segment was not constant during fish growth, but it followed a discontinuous saltatory growth. Histological analysis of the proximal lepidotrichia segments revealed that the observed apparent growth of segments is the result of fusions between segments. Fusion occurs not by mineralization of the intersegmental joints, but by bone deposition around the joints.

Morphometric discrimination of pelagic fish stocks challenged by variation in body condition

Morphometric discrimination of pelagic fish stocks challenged by variation in body condition George Geladakis, Nikolaos Nikolioudakis, George Koumoundouros, and Stylianos Somarakis* Biology Department, University of Crete, Vasilika Vouton, Heraklion, Crete, Greece Hellenic Centre for Marine Research (HCMR), Institute of Marine Biological Resources and Inland Waters (IMBRIW), Thalassocosmos, Gournes Heraklion, Crete, Greece *Corresponding author: tel: þ30 281 033 7832; fax: þ30 281 033 7822; e-mail: somarak@hcmr.gr

Skeletal ontogeny of the vertebral column and of the fins in shi drum Umbrina cirrosa (Teleostei: Perciformes: Sciaenidae), a new candidate species for aquaculture

The osteological development of the vertebral column and fins in shi drum Umbrina cirrosa was studied in order to improve knowledge for its introduction in Mediterranean aquaculture. The osteological development was studied in 171 individuals, of total length (LT ) from 2·7 to 30·2 mm that were reared under the mesocosm technique. Vertebral ontogeny starts at 3·4 and 4·0 mm LT , with the formation of the first cartilaginous neural and haemal arches, and spines, respectively, and is completed with the full attainment of epicentrals (12·5 mm LT ). The formation of vertebral centra occurs between 4·1 and 7·4 mm LT . Pectoral supports are the first fin elements to develop (3·0 mm LT ), followed by those of the caudal fin (3·8 mm LT ), pelvic fin (3·9 mm LT ) and finally by those of the dorsal and anal fins (4·5 mm LT ). The caudal fin is the first to develop fin rays and attain the full count of principal fin rays (4·5-6·8 mm LT ), but the last to be fully completed with the formation of procurrent fin rays (6·9-17·5 mm LT ). The next fins starting to present rays are the dorsal (5·3 mm LT ) and the pectoral fins (5·6 mm LT ), while the anal and pelvic fins are the last (5·7 mm LT ). Following the caudal principal fin rays (6·8 mm LT ), the dorsal, anal (6·9 mm LT ), pelvic (7·4 mm LT ) and pectoral fins (9·8 mm LT ) are the next with fully completed ray counts. Aggregation of qualitative changes, such as the appearance of cartilages, the beginning and the complement of the ossification process and the full complement of elements in U. cirrosa were measured as cumulative frequency counts. These measurements reveal three ontogenetic intervals: one very developmentally active period during early life stages (from 3 to 5·9 mm LT ), a second slower developmental period (from 6·0 to 8·9 mm LT ) and finally a period of ontogeny more focused on structure refinement up to metamorphosis and settlement (>9·0 mm LT ).