Several reproductive issues and the larval development of the ferruginous limpet, Patella ferruginea Gmelin, 1791, an endangered species endemic from the western Mediterranean Sea, were studied to fill gaps in the knowledge of its life cycle.Average diameter of mature oocytes was 141.83 μm and mean oocyte density in the ovary was 283,800 oocytes/gram. No significant correlations were found between both oocyte diameter or density and female shell length. Female fecundity (number of oocytes per gonad) was significantly correlated with shell length and varied between 189,200 oocytes in a 40.0 mm female and 5,019,200 oocytes in an 86.4 mm female. However, there was considerable variability, in particular for largest females.Spawning induction was not achieved using usual molluscan aquaculture methods. Thus, oocytes obtained after dissection of females were used for fertilizations trials. Alkalinization treatments of seawater were used to test improvement in oocyte maturation and later fertilization rates. Treatment at pH 9 during 2 h produced the highest increase in the percentage of mature oocytes and in the fertilization rate; but these results showed high variability and were mainly significant when the initial degree of maturation was low. Sperm concentration experiments determined that best in vitro fertilization were performed at 105 and 5×105 spermatozoids/ml. The sequence and timing of the complete larval development of Patella ferruginea in laboratory conditions is described and illustrated here for the first time. At 20 °C, larvae became competent for metamorphosis 3 days after fertilization, but some crawling pediveliger larvae with a still well developed velum were found even 7 days after fertilization. Recruits 1-2 mm in length were achieved in low numbers from two of the last assays and were first detected between 131-141 days after fertilization. The resulting juveniles were monitored during two years and sex determination of five survivors at the end of this period showed that two were mature males, two mature females and one indeterminate.Our results show that the main reproductive traits or larval development of P. ferruginea hardly differ from those of other non-endangered Mediterranean or NE Atlantic limpet species. Therefore, its decline cannot be mainly attributed to some constraints of these traits as was previously suggested, but to human impact.On the other hand, it is feasible to complete the life cycle of this species in laboratory conditions, from fertilized eggs to mature individuals. However, an important part of the process like spawning induction was not achieved as gonads needed to be dissected fatally from females, although sperm could be obtained from males through non-lethal biopsies. At present, large-scale aquaculture production for reintroduction, restocking or stock enhancement purposes is neither possible nor an advisable conservation tool yet. Further study is required and meanwhile, an appropriate design of a network of effectively protected marine areas that ensures connectivity among extant populations is necessary.

Vibrio parahaemolyticus is the leading cause of seafood-associated bacterial gastroenteritis worldwide. Although different studies have focused on its pattern of variation over time, knowledge about the environmental factors driving the dynamics of this pathogen, within the Chilean territory, is still lacking. This study determined the prevalence of total and pathogenic V. parahaemolyticus strains (tdh and/or trh genes) in mussels (Mytilus chilensis) collected from two natural growing areas between 2017 and 2018, using selective agar and PCR analysis. V. parahaemolyticus was detected in 45.6% (93/204) of pooled samples from the Valdivia River Estuary. The pathogenic strains carrying the tdh and/or trh gene were detected in 11.8% (24/204): tdh in 9.8% (20/204), trh in 0.5% (1/204), and 1.5% (3/204) presented both genes. In Reloncaví Fjord, V. parahaemolyticus was detected in 14.4% (30/209) of the samples, pathogenic V. parahaemolyticus carrying the trh gene was detected in 0.5% (1/209) of the samples, while the tdh gene was not detected in the samples from this area. The total count of mauve-purple colonies typical of V. parahaemolyticus on CHROMagar was positively associated by multivariate analysis with area, water temperature, and salinity. Similarly, V. parahaemolyticus detection rates by PCR had a positive correlation with the area and water temperature. The chances of detecting total V. parahaemolyticus in the Valdivia River Estuary are significantly higher than in the Reloncaví Fjord, but inversely, during spring-summer months, the interaction factor between the area and temperature indicated that the chances of detecting V. parahaemolyticus are higher in the Reloncaví Fjord. Interestingly, this period coincides with the season when commercial and natural-growing shellfish are harvested. On the other hand, pathogenic V. parahaemolyticus tdh+ was significantly correlated with an increase of water temperature. These environmental parameters could be used to trigger a warning on potential hazard, which would influence human health and economic losses in aquaculture systems.

A range of phenotypes differing in growth rate were designed in the Manila clam by 15 combining separate breeding families with size segregation within each family to constitute 16 fast and slow growing groups. Physiological components of the energy budget and scope for 17 growth (SFG) were then compared between these different phenotypes during the acute and 18 chronic responses to two diets that were iso-caloric but differed by 3-fold in their 19 protein/energy (P/E) ratios. Both diets were based on the microalgae Rhodomonas lens 20 obtained in either the exponential or the stationary phase of culture. The aims of the study 21 were 1) to test the effects of these changes in food composition on growth rate, estimated as 2 22 the balance of physiological processes of energy gain and loss integrated in the SFG; and 2) 23 to assess the extent to which physiological adjustments to diet composition are modulated in 24 order to fulfill the variable energy requirements posed by the occurrence of differential 25 growth phenotypes. Growth performance improved with the high-protein (N+) diet for the 26 different family * growth group combinations, with SFG values exceeding by 50% on 27 average the values of the low-protein (N-) diet. Digestive constraints resulted in reduced 28absorption efficiency with the N-diet, which tended to cancel out the potential benefits of 29 adjusting feeding rates in order to compensate for a low protein ration. Endogenous 30 differences in growth rate associated with segregated phenotypes were mainly accounted for 31 by differences in energy acquisition, with feeding rates differing by ~ 2-fold between fast 32 and slow growers. Additionally, significant differences were recorded for the unitary 33 metabolic costs (i.e., per unit of metabolizable energy), indicating that higher metabolic 34 efficiency was also a component of faster growth.

This study describes the first data on larval development and growth of the smooth clam Callista chione under two different temperature regimes (19 and 23 ºC). The mean diameter of the oocytes was 89.5 ± 0.7 micrometers. After seven days, the mean length of D-shaped larvae was 132.9 ± 7.8 micrometers at 19 ºC and 148.38 ± 12.74 micrometers at 23 ºC. Metamorphosis took place between days 32 and 39. Differences in length associated with different culture temperatures were statistically significant on days 11, 13, and 20. At 23 ºC, larvae reached a length of 175.15 micrometers within 11 days, whilst during the same period they reached 137.88 micrometers at 19 ºC (a difference in growth of 39%); however, survival rate was higher at 19 ºC (8%) than at 23 ºC (2%).

The presence of Vibrio parahaemolyticus in bivalve mollusc is an important cause of foodborne illnesses, and their levels are influenced by environmental changes, such as temperature and salinity. Clams are common species in estuaries and are used in environmental monitoring programmes. Present study compared the uptake and retention of nonpathogenic V. parahaemolyticus by two species of clam (Ruditapes decussatus and R. philippinarum), cohabitating in a closed system. Results showed no significant differences were found between both species of clams. Bacterial levels are following a similar trend with values between 3.48 and 3.70 log CFU/g for R. decussatus and between 3.15 and 3.49 log CFU/g for R. philippinarum. So, in the absence of water renewal, high and stable levels of V. parahaemolyticus were observed in cultured clams after exposure. Changes in physical parameters should be taken into account to design surveillance programmes in bivalves, and sampling should focus on species that have faster filtration rates at that water temperature since they potentially represent the worst-case scenario.