Dinophysis blooms in Greek coastal waters (Thermaikos Gulf, NW Aegean Sea)

The first documented Dinophysis bloom from Greek coastal watersassociated with a diarrhetic shellfish toxins outbreak was recordedin January 2000 during the HAB monitoring program in ThermaikosGulf. A species with morphological features similar to D. acuminataClaparède and Lachmann dominated this bloom. MaximumD. cf. acuminata abundance (85.4 x 10³ cells L^–1) appearedin February 2000. In 2001, high numbers of D. cf. acuminata(5 x 10³ cells L^–1) were recorded in April under conditionsof weak thermal stratification, while in 2002 maximum numbers(37 x 10³ cells L^–1) of the same species were found inFebruary under low temperature levels (11.5–12.5°C).All Dinophysis blooms persisted for no more than 4 months. Inaddition to cells resembling typical D. cf. acuminata, cellsof similar shape but smaller in size were observed at differentstages of the blooms. Other observations include couplets oflarge and small-sized cells, and also a larger robust form witha dense granular cytoplasm. The D. cf. acuminata populationalways presented a stratified vertical distribution with verticalpeaks positioned in or just above the pycnocline. Among thephysico-chemical parameters, water temperature appears to bethe most important factor influencing the distribution of Dinophysisabundance.     

Macrofauna biodiversity of mussel bed assemblages in Thermaikos Gulf (northern Aegean Sea)

Biomonitoring of mussel bed assemblages can provide valuable information about the impact of pollution on hard substrate assemblages. This study of Mytilus galloprovincialis mussel beds in Thermaikos Gulf (northern Aegean Sea) deals with the spatial and temporal structure of the associated fauna. Samples were collected and abiotic factors were measured in two successive years. Common biocoenotic methods were employed to analyze the data. The samples could be separated into three groups, with summer and winter samples being clearly different. A total of 100 species were found: polychaetes and crustaceans were the most dominant taxa. The assemblage shows high diversity with respect to species abundance. Biotic interactions within the assemblage appear to influence its composition, although the total evenness remains unaffected in space and time. The M. galloprovincialis assemblages can be found in clean as well as in polluted waters and, therefore, are of great interest in biomonitoring studies.Communicated by H.-D. Franke     

Steinhausia mytilovum in cultured mussels Mytilus galloprovincialis in the Thermaikos Gulf (northern Aegean Sea, Greece)

The microsporidian Steinhausia mytilovum was found parasitising female cultured mussels Mytilus galloprovincialis L. in the Thermaikos Gulf (northern Aegean Sea). The parasites affected the condition index of infected mussels and induced a strong hemocyte infiltration inside affected gonadal follicles. The prevalence (7.5 to 35.5%) of the parasite was relatively high in a polluted area.     

Protozoan parasites in cultured mussels Mytilus galloprovincialis in the Thermaikos Gulf (north Aegean Sea, Greece)

The protozoans Ancistrum mytili (Oligohymenophorea: Ancistridae) and Marteilia refringens/maurini (Marteiliidea: Marteiliidae) were found parasitizing cultured mussels Mytilus galloprovincialis L. in the Thermaikos Gulf (north Aegean Sea, Greece). The former did not affect the condition index of infected mussels, in contrast to the latter, which did so and which also induced hemocyte infiltration in the affected digestive epithelium. The prevalence of both parasites was relatively high in a polluted area.     

Metazoan parasite species in cultured mussel Mytilus galloprovincialis in the Thermaikos Gulf (North Aegean Sea, Greece)

This is the first study on parasites of cultured Mytilus galloprovincialis L. in Greek waters, and is based on samples collected every 2 to 3 mo between September 2000 and November 2001 at 3 stations in the Thermaikos Gulf. Each sample comprised 40 mussels. We found 4 metazoan parasite species: hydroid Eugymnanthea inquilina, gill turbellarian Urastoma cyprinae, trematode Proctoces maculatus and gut copepod Mytilicola intestinalis. Of 840 mussels examined, 406 (48.3%) mussels were harbouring hydroids of E. inquilina, 278 (33.1%) were infested with U. cyprinae, 94 (11.2%) were infested with M. intestinalis, and only 7 (0.8%) were infested with P. maculatus. The prevalence and intensity of these parasites were related to temperature and pollution. Mussels infested with these parasites had significantly lower condition indices than non-infested mussels; larger mussels were more often infested than smaller ones.     

Neuroendocrine control of reproduction in the male penaeid prawn,Parapenaeopsis hardwickii (Miers) (Crustacea,Decapoda, Penaeidae)

Effects of bilateral eyestalks ablation and injections of eyestalks, (Es) brain (Br) and thoracic ganglia (ThG) extract separately on the androgenic gland and testis development of Es-ablated (Experiment 1) and normal (Experiment 2) P. hardwickii, were investigated. The androgenic gland activity increased significantly in prawns having Es-ablated (Group II), and eyestalkless (Groups VI & VII) and normal (Groups D & E) prawns received Br and ThG extracts, separately, as compared to their respective controls (Groups I & A). Injection of unboiled Es extract in eyestalkless (Group V) and normal (Group C) prawns arrested the androgenic gland activity. Simultaneously, there was a significant (p<0.05) increase in the diameter of testicular follicles, testis weight, testis index and number of mature spermatocytes per follicle in the prawns of groups II, VI & VII of experiment 1 and of groups D & E of experiment 2 when compared to their respective controls. Injection of Es extract into the eyestalkless (Group V) and normal (Group C) prawns ceased testicular development. A significant (<0.05) decrease in testicular protein and midgut gland glycogen and lipid was found in groups II, VI & VII of experiment 1 and in groups D & E of experiment 2, but the glycogen and lipid content of the testis increased. These results indicate that the hormones released from the neuroendocrine centres regulate androgenic gland activity and spermatogenesis.     

Isolation and cDNA cloning of ovarian cortical rod protein in kuruma prawn Marsupenaeus japonicus (Crustacea: Decapoda: Penaeidae)

Two cortical rod proteins having molecular weights of 28.6 kDa and 30.5 kDa were isolated from the mature ovary of Marsupenaeus japonicus using gel filtration and reversed-phase HPLC. Analysis of the N-terminal amino acid sequence of the 28.6 kDa molecule revealed that amino acid residues 1-21 corresponded to residues 9-29 of the 30.5 kDa molecule. Examination of homology using BLAST showed that 21 amino acids out of 29 residues of the 28.6 kDa molecule, and 14 out of 29 residues of the 30.5 kDa molecule were identical to that of the ovarian cortical rod proteins of Penaeus semisulcatus. Positive immunohistochemical reaction to antiserum raised against the 28.6 kDa protein was observed on cortical rods forming around the periphery of oocytes at the maturation stages. Western blotting analysis revealed that both the 28.6 kDa and 30.5 kDa molecules stained with the anti-28.6 kDa antiserum. Furthermore, the 28.6 kDa and 30.5 kDa proteins were both glycosylated, as evidenced by positive carbohydrate staining using Concanavalin A and production of positive PAS reaction. These results indicate that the cortical rods are comprised of the 28.6 kDa and 30.5 kDa molecules. We subsequently cloned two full-length cDNAs based on the N-terminal sequences of the 28.6 kDa and 30.5 kDa molecules. The open reading frame of 28.6 kDa and 30.5 kDa encoded 276 amino acid residues. Comparison analysis of the two cDNAs revealed that the location of the processing site and sequence of signal peptides differed, indicating that the two cDNAs are products of two separate genes and encode the 28.6 kDa molecule and 30.5 kDa molecule, respectively. Both proteins possessed one potential N-linked glycosylation site. It is considered that both molecules are components of the cortical rods, forming a jelly layer after fertilization.     

Thiol pools and glutathione redox ratios as possible indicators of copper toxicity in the green macroalgae Enteromorpha spp. from the Scheldt Estuary (SW Netherlands,Belgium) and Thermaikos Gulf (Greece,N Aegean Sea)

Defence mechanisms against Cu toxicity were examined in two dominant Enteromorpha species from two coastal water types. The macroalgae were collected at three locations in the eulittoral of the Scheldt Estuary (Netherlands, Belgium) and the Thermaikos Gulf (Greece). For 10 days E. prolifera (Scheldt) and E. linza (Thermaikos) were incubated in seawater media of different salinities: 6, 9, 23 psu and 25, 30, 35 psu, respectively. In one series, media were enriched with 100 μg Cu l-1; responses were compared with those in controls with no extra Cu added. Enteromorpha, which is frequently used as a monitor species for heavy metal contamination, had relatively high Cu tissue levels (0.5–3.8 μmol Cu gdwt-1). Cu levels in E. prolifera controls (Scheldt) decreased with salinity; this was not the case with Cu levels in E. linza controls (Thermaikos). During the 10-d incubation algal protein contents and tissue Cu were rather stable. In E. linza (Thermaikos) algal protein contents were significantly lower than those of E. prolifera (Scheldt), although there was no indication for nitrogen limitation in E. linza. E. linza also had much lower glutathione pools than E. prolifera. Only under acute Cu stress (metal addition) did E. prolifera synthesise metal-binding thiols (phytochelatins). Phytochelatin pools are not suitable as an indicator of the Cu levels in these algae. The glutathione redox ratio GSH:(GSH + 0.5GSSG) was used as an indicator of (Cu-induced) oxidative stress. In E. prolifera (Scheldt) this ratio decreased with algal Cu content (P <0.05), from ~0.5 to ~0.2. The average glutathione ratios in Enteromorpha from the Scheldt and Thermaikos showed some oxidative stress induction with increasing algal Cu contents, however more clearly if Cu was added. As this redox ratio can also be influenced by environmental factors such as irradiance and desiccation, it may not be useful as an indicator for Cu-induced oxidative stress in situ. This revised version was published online in September 2006 with corrections to the Cover Date.     

Some aspects of respiratory metabolism of a penaeid prawn,Penaeus japonicus (Bate) (Crustacea,Decapoda, Penaeidae)

Respiratory metabolism of a marine penaeid prawn, Penaeus japonicus (Bate) was studied in relation to body size, starvation, dissolved oxygen tension, salinity and temperature. Oxygen consumption was significantly (P < 0.03) elevated with decline in body size. The rate of oxygen consumption was decreased significantly (P < 0.05) with an increase in the day of starvation, but the values of the loth and 15th day did not differ significantly (P > 0.05) from each other, indicating adaptation to starved conditions. Respiratory rate was on the ascending scale with an elevation in the surrounding oxygen content. Oxygen consumption increased significantly (P < 0.05) in both hyper- and hypotonic media. Rate of oxygen consumption was significantly (P < 0.05) augmented with an increase in the ambient temperature upto 34°C but a drastic fall was found at both low (18°C) and high (36°C) extreme temperatures. Functional significance of these findings to the prawn, in combating the environmental eddies is discussed.This investigation was supported by I.C.A.R., New Delhi, through a project No. 21 (80)/73-ASR (I)This investigation was supported by I.C.A.R., New Delhi, through a project No. 21 (80)/73-ASR (I)     

Modelling and forecasting the fortnightly cladoceran abundance in the Saronikos Gulf (Aegean Sea)

In the present study, we evaluated the ability of dynamic regressionon the basis of its efficiency to model and forecast the fortnightlyabundance of dadocerans during 1989–1993 in a coastalregion of the eastern Saronikos Gulf (Aegean Sea). The followingdynamic regression model explained 79% of the variability ofthe transformed cladoceran abundance during the fitting period(January 1989-December 1992): In (cladocerans)_t = 0.4314 In(chlorophyll ) –5.9013 In (salinity) + 8.7760 In (temperature)+ 0.2371 In (cladocerans)_t–20. The model always predictedthe start and the end of the cladoceran season, and forecastedthe cumulative cladoceran abundance during January-December1993 with an absolute percentage error of 14.5%. The positiveeffect of sea temperature and chlorophyll , and the negativeeffect of salinity, on cladoceran abundance are all consistentwith previous studies. The positive relationship between cladoceranabundance at times and t–20 approximates the seasonalcycle of their abundance.     

Role of eyestalk hormone in the carbohydrate metabolism of a marine penaeid prawn,Parapenaeopsis hardwickii (MIERS) (Crustacea,Decapoda, Penaeidae)

Data furnished here concern with the role of eyestalk hormone in the regulation of carbohydrate metabolism in Parapenaeopsis hardwickii. Bilateral eyestalk ablation has brought about a significant (P < 0.01) fall and rise in the glycogen content in the midgut gland and abdominal muscle respectively. Although eyestalk ablation resulted in a significant (P < 0.01) depletion of fat in midgut gland, n0 significant (P > 0.05) change was observed in the abdominal muscle. Eyestalk extract administration in eyestalk-less prawns has significantly (P < 0.05) restored the glycogen and fat metabolites in the midgut gland. There was an obvious change in the glycogen content of the midgut gland and abdominal muscle of normal prawns when injected with eyestalk extracts from prawns in different molting stages. Eyestalk extract from intermolt prawns caused a significant (P < 0.05) decrease and increase in the glycogen quantity in the midgut gland and abdominal muscle respectively. Eyestalk extract from premolt and postmolt prawns has, although not significantly (P > 0.05), decreased and increased the utilization of glycogen respectively in the midgut gland. The physiological significance of these findings are discussed briefly.Paper forms part IV of the series

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Reproductive biology of the smooth-hound shark Mustelus mustelus (L.) in the Gulf of Gabès (south-central Mediterranean Sea)

The reproductive biology of the smooth-hound shark Mustelus mustelus was studied in the Gulf of Gabès (southern Tunisia). Females were found to mature between 1075 and 1230 mm total length ( L _T) whereas males matured between 880 and 1120 mm L _T. The L _T at which 50% of the population reached maturity was 971 and 1172 mm for males and females, respectively. Male gonads were symmetrical in terms of mass and both functional, whereas in females only the right ovary was functional. The seasonal changes in the oocytes and testes development, embryo length and the occurrence of near-term and post-partum females showed that this species displayed a clearly defined annual reproductive cycle with parturition occurring during late April and early May, after a gestation period of 10–11 months. Mating took place during May and early June and fertilization occurred from early June to early July. The embryo sex ratio was not significantly different from unity. Litter size varied from four to 18 embryos and was positively correlated with maternal L _T. The young were born with a L _T of 340–420 mm.     

Study of changes in physicochemical and microbiological characteristics of shrimps (Melicertus kerathurus) stored under modified atmosphere packaging

Fresh minimally processed shrimps were stored under modified atmosphere packaging (60% CO₂:40% N₂ for MAP A and 92.9% N₂:5.1% CO₂:2% O₂ for MAP B) for 5 days at 3 °C. Total mesophiles, H₂S forming bacteria, Pseudomonas spp., Brochothrix thermosphacta, firmness, color and sensory parameters were investigated throughout the whole time of the experiment. During storage period samples stored under MAP B managed to retain firmness values close to the initial values. All microbial populations growth was suppressed by the presence of MAP A. Samples stored under MAP B managed to maintain their firmness values close to the initial ones while MAP A samples were significantly less firm (p < 0.05).     

Reproductive biology of the rock shrimp Sicyonia dorsalis (Decapoda: Penaeoidea) from the southeastern coast of Brazil

Summary

Sicyonia dorsalis is not commercially exploited in Brazil, but it forms a critical link in marine food chains by converting detritus food sources into microorganism biomass that is available for higher trophic levels. We examined the reproductive biology of this species, sampled for five and a half years in a tropical locality, the southeastern coast of São Paulo (23° S), Brazil. Monthly samples were taken from January 1998 to June 2003 at depths of 5 to 45 m. Degree of ovarian development was used to examine breeding in adult females. Recruitment was estimated by changes in proportion of individuals in juvenile size classes of carapace length (CL #8.2 mm) in relationship to the total number of individuals. The largest immature female measured 9.2 mm CL, but 75% of females were smaller than 7.3 mm CL. The largest immature male measured 6.8 mm CL. The relative frequency of reproductive females was negatively correlated with the relative frequency of recruitment (p <0.001). Reproductive females were found in every season, with peaks in December-February following the recruitment peak in March-June, and a second peak of spawning in May-July and of recruitment in September-November. The continuous reproductive pattern observed for S. dorsalis, combined with the hypothesis that during spring and summer the phytoplankton production is higher, when the South Atlantic central water mass intrudes into the region during upwelling events, suggests that food availability for protozoeal and mysis larvae may be an important selective factor shaping the seasonal breeding pattern for S. dorsalis. The classical paradigm of continuous reproduction at lower latitudes, with increased seasonality of the breeding period at higher latitudes, seems to be valid for this species.     

Neural control of the pyloric region in the foregut of the shrimp Penaeus (Decapoda: Penaeidae)

Pyloric pattern-generating neurons that control the pyloric region of the foregut were identified in the stomatogastric ganglion of the most primitive decapod genus Penaeus. Five types of motor neurons and one interneuron are involved in generation of pyloric motor pattern. One cell type of motor neurons innervates muscles of both the gastric mill and the pylorus like the gastric motor neurons in Cancer, but unlike those in Panulirus. These identified neurons are connected to each other either by electrical or inhibitory chemical synapses to construct the neural circuit. This pyloric circuit is similar to the homologous circuit of other crustacean species though some differences are seen in synaptic connections, supporting the hypothesis that the basic design of the neural circuit has been conserved during evolution of the Malacostraca, and that differences have occurred in the synaptic connectivity as the foregut structure has become complex. The motor neurons use either acetylcholine or glutamate as a neurotransmitter like in reptantians. The foregut structure, the number of the pyloric cells, muscle innervation, neurotransmitters, and circuitry are compared among malacostracan crustaceans to provide insight into how the neural circuits change and evolve to produce the motor patterns mediating behaviour. Accepted: 18 April 1997     

An unusual abnormality in the development of an eye of a marine penaeid prawn,Parapenaeopsis stylifera (H. Milne Edwards). (Crustacea,Decapoda, Penaeidae)

A male prawn, Parapenaeopsis stylifera, collected in a haul, was found to be having an undeveloped right eye. The eyestalk was absent and eye pigment was located directly on the reduced basal segment. The observation is briefly discussed on a neurobiological basis.     

Ontogeny of gut morphology in the white shrimp Penaeus setiferus (Decapoda,Penaeidae)

Ontogeny of the gut in Penaeus setiferus was investigated by reconstruction of serial sections examined by light microscopy. Development of the gut into the adult form is protracted over several weeks beyond metamorphosis in steps that may be directly related to the unique postlarval life history of Penaeus. The gastric mill is lacking in larval stages of P. setiferus. In protozoeal stages Z₁-Z₃, the pyloric ampullae are blind sacs that do not communicate with the midgut. The gland filter first appears in mysis stage M₂. The gastric mill in early postlarval (PL) stages consists of poorly chitinized lobes with flexible setae. By PL₂₁ the ossicles of the gastric mill are rigid and setae are replaced by spine-like denticles, but even by PL₃₅ the gastric mill is neither as massive nor heavily chitinized as in adults. During the mysis stages and early PL stages, the hepatopancreas communicates freely with both the foregut and the midgut trunk. By PL₃₅ the hepatopancreatic ducts are essentially isolated from the remainder of the midgut by foregut ossicles. The midgut in Z₁ consists of two pairs of simple caeca and the midgut trunk. During larval growth, each of the lateral midgut caeca develops into a number of lobes. After metamorphosis these lobes begin to ramify into small-diameter tubules, and by PL₃₅ have completely ramified into the hepatopancreas of adults. From M₁ to PL₄, the anterior midgut caeca decrease in absolute size and become a single anterior diverticulum. The posterior midgut diverticulum first appears in PL₂₁ as a simple sac and thereafter increases in size and complexity.     

Reproductive biology of the shore crab Carcinus maenas (Decapoda,Portunidae): a macroscopic and histological view

A histological study of the reproductive cycle of male and female shore crabs, Carcinus maenas (Linnaeus), was performed monthly on the South West coast of Ireland (from December 2006 to July 2008). The calculated sex ratio deviated from equality, 1:0.53, revealing a strong male bias. A system was devised, based on screening of tissue sections, to describe and stage gametogenic development. Histological examinations revealed that ovarian development occurred biannually, with a primary winter cycle in which the larger crabs reproduced and a secondary summer cycle, when smaller crabs reproduced. An association was observed where more of the larger specimens were caught in the summer months and the smaller specimens in the winter months, which inversely correlated with the segregated breeding cycles. There was strong evidence that mature male crabs could potentially copulate year round since all mature specimens, collected throughout the year, contained viable spermatozoa. Developmental stages of oogenesis and spermatogenesis were described to develop a practical gonadal index for this portunid crab, providing information on the biology of this species, which will be of benefit for fisheries management.     

Some aspects of the biology and ecology ofKnipowitschia caucasica (Teleostei: Gobiidae) in the Evros Delta (North Aegean Sea)

Some aspects of the biology and ecology of the gobyKnipowitschia caucasica were studied over a period of 13 months in a poly-to euhaline area in the Evros Delta (North Aegean Sea). This fish grows rapidly in the summer and autumn after hatching, matures after its first winter, breeds from the end of April to the end of July, and grows rapidly again in July–September. The older males perish after their second February, whereas some females have a second breeding season at the end of April/beginning of May, shortly before their death. The fish grows to about 40 mm in total length. There is a positive correlation between the total length (TL) and the standard length (SL) or the cleaned body weight (CW). SL increases slower than TL, whereas CW increases slower than TL in immature individuals and faster in males and females. There is no difference between immature individuals, males and females, in the growth rate of SL, TL and CW, TL. The mean monthly values of the condition factor varies from 0.289 to 0.576 in females and from 0.313 to 0.548 in males. The overall sex ratio of females to males is 1: 1.46. Fecundity ranges from 60 to 217 eggs with a mean value of 109.8 and depends upon size, whereas relative fecundity varies between 968 and 2170 with a mean of 1558. The fish feeds predominantly on benthic amphipods and polychaetes.