Aspects of the reproductive biology ofPollicipes pollicipes (Cirripedia; Lepadomorpha) from the southwest coast of Portugal

The pedunculated cirripedePollicipes pollicipes is of considerable economic importance in Portugal, particularly along the southwest coast. Current knowledge of its biology is poor, as evidenced by the paucity of available literature. This paper reports on the reproduction of twoP. pollicipes populations, Castelejo and Zavial, on the southwest coast of the Algarve. Differences in reproductive patterns between the two sites were minor and not statistically significant, despite differences in environmental conditions between the two sites. Adult animals carried fertilised eggs from April throughout September, and the percentage of individuals with egg masses correlated positively with air but not with sea water temperature. Brooding success was greater with average air temperature in excess of 14°C during months of strong upwelling and presumed food availability. Functional ovaries and testes are available in the population all year round but fertilisation does not appear to occur during the winter months. Reproduction ofP. pollicipes on the southwest coast of the Algarve appears closely linked to the upwelling phenomenon with the rate of deposition of gonadal tissue probably being determined by environmental temperature. The cues which determine the cessation of fertilisation remain to be investigated.     

Isolation and characterization of nine polymorphic microsatellite markers in the two‐banded sea bream (Diplodus vulgaris) and cross‐species amplification in the white sea bream (Diplodus sargus) and the saddled bream (Oblada melanura)

We have developed nine new microsatellite markers for the two‐banded sea bream (Diplodus vulgaris) from an enriched genome library protocol. All these loci are polymorphic, with mean allelic diversity of 13 (range 5 –21), and expected and observed heterozygosities from 0.641 to 0.932 and 0.428 to 0.914, respectively. Cross‐species tests in two close‐related species of the genus Diplodus (D. sargus and O. melanura) revealed successful amplifications at 8 out of 9 loci, with mean allele number of 4.75 (range 2–8) and 5.50 (range 3 –10), respectively. These results are consistent with the close phylogenetic relationships between the three species, indicating this set of primers might prove useful for studying the levels of genetic diversity and population differentiation in these three species and in other phylogenetically close species of the genus Diplodus and Sparus.     

Morphometric characterization of sharpsnout sea bream (Diplodus puntazzo) and gilthead sea bream (Sparus aurata) spermatozoa using computer-assisted spermatozoa analysis (ASMA)

As part of a larger study on sperm quality and cryopreservation methods, the present study characterized the head morphometry of sharpsnout sea bream (Diplodus puntazzo) and gilthead sea bream (Sparus aurata) spermatozoa, using both scanning electron microscopy (SEM) and computer‐assisted morphology analysis (ASMA). The latter method has been used rarely in fish and this is its first application on sharpsnout sea bream and gilthead sea bream spermatozoa. Results obtained using SEM are expensive and time‐consuming, while ASMA provides a faster and automated evaluation of morphometric parameters of spermatozoa head. For sharpsnout sea bream spermatozoa, similar head measurement values were obtained using both ASMA and SEM, having a mean ± standard error length of 2.57 ± 0.01 μm vs 2.54 ± 0.02 μm, width of 2.22 ± 0.02 μm vs 2.26 ± 0.04 μm, surface area of 4.44 ± 0.02 μm² vs 4.50 ± 0.04 μm² and perimeter of 7.70 ± 0.02 μm vs 7.73 ± 0.04 μm using ASMA and SEM, respectively. Although gilthead sea bream spermatozoa were found to be smaller than those of sharpsnout sea bream, spermatozoal head morphometry parameters were also found to be similar regardless of evaluation method, having a mean head length of 1.97 ± 0.01 μm vs 1.94 ± 0.02 μm, head width of 1.80 ± 0.01 μm vs 1.78 ± 0.02 μm, surface area of 3.16 ± 0.03 μm² vs 3.18 ± 0.06 μm² and perimeter of 6.52 ± 0.04 μm vs 6.56 ± 0.08 μm using ASMA and SEM, respectively. The results demonstrate that ASMA can be considered as a reliable technique for spermatozoal morphology analysis, and can be a useful tool for studies on fish spermatozoa, providing quick and objective results.     

Morphology of the tongue dorsal surface in white sea bream (Diplodus sargus sargus)

In the present study, the tongue dorsal surface of the white sea bream Diplodus sargus sargus (Linnaeus, 1758) (teleosts, Sparidae) was studied, to give a support to the knowledge of the anatomical characteristics of the oral cavity of a species with a future potential use in aquaculture. The feeding habits in captivity are one of the critical steps in the species of commercial interest, strictly related to the morphological characteristics of the oropharyngeal cavity. This study was undertaken, using light and scanning electron microscopy, to analyse the morphology of the dorsal tongue surface to show whether relationships are present between the anatomy and the nutritional habits and choices of this farmed species. Three zones, an apex, a body and a root, can be clearly distinguished, with a pouch partially covering the apex. In the pouch, cylindroid and mucosal ridges were observed. Along the whole tongue surface, from the apex to the root, on the medial and lateral parts, many papillae are present, with a fungiform, cylindroid and cone‐like aspect. Taste buds are showed on the dorsal surface of some papillae.     

Ontogeny of the digestive tract in sharpsnout sea bream Diplodus puntazzo (Cetti, 1777)

The ontogeny of the digestive tract was studied histologically and histochemically in sharpsnout sea bream Diplodus puntazzo from hatching (0 DAH, Days After Hatching) until day 57 (57 DAH). At hatching, the digestive tract appeared as a histologically undifferentiated straight tube lying dorsally to the yolk sac. When the mouth opened at 3 DAH, the digestive tract was differentiated into buccopharynx, oesophagus, incipient stomach and intestine. The pancreas, liver and gall bladder were also differentiated at this stage and both the bile and pancreatic duct had opened into the anterior intestine. Active feeding began in 50% of larvae at 4 DAH, although permanence of yolk reserves until 7 DAH suggests a period of both endogenous and exogenous feeding. Nutrient absorption was first visible from 5 DAH, as colourless supra- and infranuclear vacuoles in the anterior intestinal mucosa, suggesting a lipid content, as well as supranuclear, eosinophilic vacuoles, containing protein, in the posterior intestinal mucosa. Early caecal development could be detected from 10 DAH, whereas gastric glands appeared at 30 DAH, indicating the transition from larval to juvenile stage and the acquisition of an adult mode of digestion. Goblet cells appeared in the digestive tract of sharpsnout sea bream larvae shortly after first feeding. The mucus content of goblet cells varied with the digestive region and, in the buccal cavity and oesophagus, also with the developmental phase. This study provides knowledge for better husbandry practices in the aquaculture industry, as well as for the implementation of future nutritional studies.     

Sharpsnout sea bream (Diplodus puntazzo) humoral immune response against the parasite Enteromyxum leei (Myxozoa)

The humoral innate immune response of sharpsnout seabream Diplodus puntazzo against the myxozoan Enteromyxum leei was studied. Enteromyxosis was transmitted by cohabitation and a group of uninfected fish served as control. At 5, 12, 19, 26, 40 and 55 days post-exposure (p.e.), control and recipient fish were sampled to determine the prevalence of infection and some humoral innate immune parameters (antiprotease, antitumoral and peroxidase activities). Prevalence of infection was high from day 12 p.e. and reached 100% at days 40 and 55, when intensity of infection was medium to severe. The antiprotease activity was significantly increased in E. leei-exposed fish with respect to control fish at days 12 and 19 p.e. The serum antitumoral activity was slightly lower in recipient than in control fish at all sampling times, except at 40 days p.e., though no statistically significant differences were observed. Serum peroxidases were higher in all recipient fish than in control ones, with the highest stimulation index at 40 days p.e. Within recipient fish, no differences were detected between sampling times in any of the measured activities. The possible implication of these immune factors in the high susceptibility of D. puntazzo to this enteromyxosis is discussed.     

Characterization of eight microsatellite markers in the white sea bream, Diplodus sargus (Teleostei, Sparidae)

The white sea bream, Diplodus sargus (Teleostei, Sparidae), is a species with a high commercial importance in Mediterranean aquaculture. There is currently little information available about the genetic characteristics of cultured populations. In this survey, we have developed eight polymorphic microsatellites for the white sea bream using an enriched genome library protocol. All of them were polymorphic in the 67 individuals tested, 32 of which were wild specimens, and 35 were individuals from a captive F(1) broodstock. These markers can potentially be useful tools for use in population genetic studies.     

Diet overlap of juvenile salema (Sarpa salpa), bogue (Boops boops) and common two‐banded sea bream (Diplodus vulgaris) in the south‐eastern Adriatic

The food compositions of salema Sarpa salpa, bogue Boops boops and common two‐banded seabream Diplodus vulgaris in Donji Molunat Bay (south‐eastern Adriatic) were studied in order to evaluate the diet overlap among them. Fish were collected from March to July 2009 using a beach seine net. Three species of crustaceans were the most common prey, the most abundant being copepods. A significant overlap in the diet calculated using Schoener's index was recorded in May when the index was 0.9266 for bogue and salema, 0.6091 for bogue and common two‐banded seabream, and 0.6142 for common two‐banded seabream and salema.     

The growth of the common two-banded seabream, Diplodus vulgaris (Teleostei, Sparidae), in Canarian waters, estimated by reading otoliths and by back-calculation

The yearly nature of increment formation in the otoliths of 1–9‐year‐old seabream, Diplodus vulgaris (E. Geoffrey Saint‐Hilaire 1817), from the Canary Islands was validated. The marginal increment method showed that the opaque rings were formed in summer, and the translucent rings in winter. The Brody Proportional Hypothesis and the power length–radius relationship used to back‐calculate the growth trajectories of D. vulgaris showed that this growth model could provide reasonable growth estimates in this species. Growth back‐calculation and growth estimates obtained by direct otolith readings were similar. Data on age and size used to estimate the parameters of the von Bertalanffy growth model for D. vulagris from the Canary Islands showed that males and females had similar growth rates.     

Pea protein concentrate in diets for sharpsnout sea bream (Diplodus puntazzo): effects on growth and health status

Four diets for sharpsnout sea bream juveniles (14 g body weight) with four levels of air-processed pea protein concentrate (PPC) (0, 160, 320 and 487 g/kg diet) were tested in triplicate. The experimental diets were isonitrogenous (43% crude protein) and isolipidic (19% ether extract) and the fish were fed to satiation twice a day. After 125 d, fish growth was diminished by the inclusion of PPC. Feed conversion did not show significant differences in any treatment. Neither the body analyses nor the protein and individual essential amino acid retention efficiencies were affected by the inclusion of PPC in the diet. However, histological gut examinations revealed noticeable differences. Fish fed the diet with the highest inclusion level of PPC presented the longest villous length and the most goblet cells, and the width of the lamina propria increased in the anterior intestine. Although no negative changes in nutritive parameters were detected, these alterations might affect nutrient transport, with negative consequences for fish growth. It was concluded that the PPC in the amounts tested here is an inappropriate substitute for fishmeal in diets for sharpsnout sea bream juveniles.     

Reproductive cycle of the commercially harvested sea urchin (Paracentrotus lividus) along the western coast of Portugal

Harvested populations of the sea urchin (Paracentrotus lividus) from the northwestern (Carreço) and southwestern (Aljezur) coasts of Portugal were surveyed to describe the species reproductive cycle and assess possible relationships with geographical location and seawater temperature. Individuals were sampled monthly to analyze gonad histology, mean gonadal index (GI), and gonadosomatic index (GSI) during 2 consecutive years (November 2010–November 2012). Both populations presented an annual reproductive cycle, with synchronous gonad maturation and gamete release between sexes. Gonad maturation occurred throughout autumn–winter, followed by a single but prolonged spawning season during spring–summer. The duration of the spawning season displayed a latitudinal gradient likely related to the north–south increasing trend in seawater temperature, with the northwestern population (Carreço) exhibiting a shorter spawning period compared to the southwestern population (Aljezur). The timing and duration of the spawning season was compared with several populations throughout the distributional range of P. lividus in the Atlantic Ocean and Mediterranean Sea. In the population from Carreço, the size at first sexual maturity (test diameter = 35.9 mm) was considerably smaller than the minimum conservation reference size (MCRS) of 50 mm test diameter legally established for P. lividus. This study confirms that sustainable exploitation depends on harvesters’ awareness of and compliance with the MCRS and provides useful information for the eventual establishment of a closed season in the harvesting of P. lividus.     

The reproductive biology of the genusBaldellia (Alismataceae)

The reproductive biology of the genusBaldellia was studied under cultivation and in nature.B. ranunculoides subsp.repens is self-incompatible whereasB. ranunculoides subsp.ranunculoides andB. alpestris are self-compatible. Bud-pollination occurs in theB. alpestris. Self-incompatibility correlates with the production of fewer, larger, more showy flowers, higher pollen production (but reduced pollen grain size), fewer carpels and smaller seeds. Resource allocation to sexual reproduction is inversely correlated with the degree of vegetative growth.B. ranunculoides subsp.repens produces more ramets than subsp.ranunculoides, which reproduces mainly by seeds.B. alpestris is intermediate between the two since it is self-compatible, produces fewer, larger seed than subsp.ranunculoides and is also able to propagate by vegetative means.     

Genetic evidence for the mating system and reproductive success of black sea bream (Acanthopagrus schlegelii)

Understanding the mating system and reproductive success of a species provides evidence for sexual selection. We examined the mating system and the reproductive success of captive adult black sea bream (Acanthopagrus schlegelii), using parentage assignment based on two microsatellites multiplex PCR systems, with 91.5% accuracy in a mixed family (29 sires, 25 dams, and 200 offspring). Based on the parentage result, we found that 93.1% of males and 100% of females participated in reproduction. A total of 79% of males and 92% of females mated with multiple partners (only 1 sire and 1 dam were monogamous), indicating that polygynandry best described the genetic mating system of black sea bream. For males, maximizing the reproductive success by multiple mating was accorded with the sexual selection theory while the material benefits hypothesis may contribute to explain the multiple mating for females. For both sexes, there was a significant correlation between mating success and reproductive success and the variance in reproductive success of males was higher than females. Variation in mating success is the greatest determinant to variation in reproductive success when the relationship is strongly positive. The opportunity for sexual selection of males was twice that of females, as well as the higher slope of the Bateman curve in males suggested that the intensity of intrasexual selection of males was higher than females. Thus, male–male competition would lead to the greater variation of mating success for males, which caused greater variation in reproductive success in males. The effective population number of breeders (N_b) was 33, and the N_b/N ratio was 0.61, slightly higher than the general ratio in polygynandrous fish populations which possibly because most individuals mated and had offspring with a low variance. The relatively high N_b contributes to the maintenance of genetic diversity in farmed black sea bream populations.     

The reproductive biology of blackspot sea bream Pagellus bogaraveo in captivity. I. gonadal development, maturation and hermaphroditism

Gonadal development, maturation, spawning and hermaphroditism were investigated in captive blackspot sea bream, Pagellus bogaraveo Brünnich, 1768, during the second, third and fourth years of life. The gonads of 224 fish were examined macroscopically and histologically. Undifferentiated gonads were found in fish smaller than 22.0 cm. Adult fish showed four gonadal differentiations: ovotestes with functional testis and quiescent ovary (Mf), ovotestes with functional ovary and regressed testis (mF), ovotestes with both ovary and testis at a resting stage (mf), and ovaries with no male tissue (F). The overall incidence of gonochoric females F was 41%. Functional males Mf were more frequent in age classes 1+ and 2+, whereas functional females mF predominated in the 3+ age class, above 25.0 cm TL. Histological examination revealed testicular degeneration and atrophy in functional females mF. On the basis of both histological data as well as size and age frequency distribution, it is suggested that the reproductive strategy of P. bogaraveo in captivity is characterized by protandrous hermaphroditism, with a high incidence of female gonochorism. Spawning occurred in March–April, at a size of 28.0 cm and age 3 in males and at 29.5 cm and age 4 in females. The gonosomatic index (GSI) remained constantly low (≤ 0.05) throughout the second and third years of life. A significant increase in GSI was noted in both males and females at the accomplishment of the fourth year of life, coinciding with the spawning season. The results are compared with information available on wild P. bogaraveo and discussed with a view to a possible exploitation of this species in aquaculture, through a reliable control of reproduction.     

Two new species of Siriella (Crustacea--Mysidacea) from the southwest coast of Australia

Two new species of Siriella, S.australiensis sp. nov. and S.spinulasp. nov., are described here. Siriella australiensis is distinguishedby the character of the third and fourth pleopods of the male.Siriella spinula is characterized by the short frontal spineof the labrum and the short linguiform telson showing sexualdimorphism.     

The gonadal cycle of captive white bream, Diplodus sargus (L.)

A histological study was carried out to follow gonadal changes in captive white bream during the second and third years of life. All but one individual matured as a male. Spawning was found to occur in winter. Environmental factors are likely to have influenced the reproductive activity of the captive fish.     

Reproductive biology and recruitment of the white sea bream in the Azores

The life history of the white sea bream Diplodus sargus in the Azores showed a pattern consistent with digynic hermaphroditism achieving sexual maturity during the second year of life, at 16·7 cm L _T. Spawning occurred from March to June at temperatures between 15 and 17° C and the onset and duration of spawning season in the sea bream appeared to be influenced by sea water temperatures. As latitude decreased, both in the northern and southern hemispheres, the spawning season of D. sargus populations started earlier and extended longer, highlighting the potential importance of temperature to the onset and duration of reproduction in this species. Settlement took place from late May to July, and settlers remained in the nursery area for c . 2·5 months. Emigration from the nursery area to join shoals of juveniles occurred from late July to September.     

Sorting grid trials to improve size selectivity of red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis) in Turkish bottom trawl fishery

Sorting grids with two different bar spacings (12 mm and 14 mm) were tested to improve size selectivity of the commercially important fish species, red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis), in Turkish bottom trawl fishery. Fishing trials were carried out with R/V ‘Egesüf’ between April and May 2003 in Izmir Bay, Aegean Sea, using a traditional bottom trawl. Selectivity data were collected by the top cover method and analyzed by means of a logistic equation with the maximum likelihood method. Selectivity parameters for individual hauls were obtained with the software program cc 2000 . Mean selectivity was also estimated and compared using the EC Model software that takes between‐haul variations into account. The codend catch size as an additional explanatory variable was used in the comparison. The Kolmogorov–Smirnov (K–S) test was also applied to detect differences between length‐frequency distributions in the upper and lower bags of the 12 and 14 mm bar spacings for red mullet and annular sea bream. The mean L₅₀ values of red mullet were 8.7 and 10.0 cm with the 12 and 14 mm grids, respectively. The L₅₀ value of 14 mm was comparable with the L₅₀ value of the codend mesh size; however, the 12 mm value was rather low. The mean L₅₀ values of 12 and 14 mm bar spacings were 8.8 and 10.4 cm for annular sea bream, respectively; the value of 14 mm bar spacing was very close to 50% size at sexual maturity of the species (10.5 cm). The K–S test indicated length distributions of red mullet and annular sea bream in the 12 and 14 mm upper and lower bags as significantly different (P < 0.05). These results show that improving the size selectivity in a multi‐species fishery using a single selective device is rather difficult. However, higher size selectivity can be obtained when considering the minimum landing size or the 50% sexual maturity size for a given species.