Papers by Joana Figueiredo
Ecology
Many organisms have a complex life-cycle in which dispersal occurs at the propagule stage. For ma... more Many organisms have a complex life-cycle in which dispersal occurs at the propagule stage. For marine environments, there is growing evidence that high levels of recruitment back to the natal population (“self-recruitment”) are common in many marine organisms. For fish, swimming behavior is frequently invoked as a key mechanism allowing high self-recruitment. For organisms with weak-swimming larvae, such as many marine invertebrates, the mechanisms behind self-recruitment are less clear. Here, we assessed whether the combination of passive retention of larvae due to re-circulation processes near reefs, and the dynamics of settlement competence, can produce the high levels of self-recruitment previously estimated by population genetic studies for reef-building corals. Additionally, we investigated whether time to motility, which is more readily-measurable than competence parameters, can explain the between-species variation in self-recruitment. We measured the larval competence dynamics of broadcastspawning and brooding corals and incorporated these in a model of larval retention around reefs to estimate the potential for self-recruitment and assess its variation among species and reefs. Our results suggest that the larvae of many corals, even those with an obligate planktonic phase, develop with sufficient rapidity to allow high levels of self-recruitment, particularly for reefs with long water retention times. Time to motility explained 77-86% of the between-species variation in potential self-recruitment in scenarios with a realistic range of retention times. Among broadcast spawners, time to motility was strongly and positively correlated with egg size, i.e. broadcast spawner species with small eggs developed more rapidly and exhibited greater potential for self-recruitment. These findings suggest that, along with water retention estimates, easy-to-measure species traits, such as egg size and time to motility, may be good predictors of potential self-recruitment, and therefore may be used to characterize the spectrum of self-recruitment in corals.
Coral Reefs, Jan 1, 2012
Some scleractinian coral larvae have an extraordinary capacity to delay metamorphosis, and this i... more Some scleractinian coral larvae have an extraordinary capacity to delay metamorphosis, and this is reflected in the large geographic range of many species. Coral eggs typically contain a high proportion of wax esters, which have been hypothesized to provide a source of energy for long-distance dispersal. To better understand the role of lipids in the dispersal of broadcast spawning coral larvae, ontogenetic changes in the lipid and fatty acid composition of Goniastrea retiformis were measured from the eggs until larvae were 30 days old. Egg biomass was 78.8 ± 0.5% lipids, 86.3 ± 0.2% of which were wax esters, 9.3 ± 0.0% polar lipids, 4.1 ± 0.2% sterols, and 0.3 ± 0.1% triacylglycerols. The biomass of wax esters declined significantly through time, while polar lipids, sterols and triacylglycerols remained relatively constant, suggesting that wax esters are the prime source of energy for development. The most prevalent fatty acid in the eggs was palmitic acid, a marker of the dinoflagellate Symbiodinium, highlighting the importance of symbiosis in coral reproductive ecology. The proportion of polyunsaturated fatty acids declined through time, suggesting that they are essential for larval development. Interestingly, triacylglycerols are only abundant in the propagules that contain Symbiodinium, suggesting important differences in the energetic of dispersal among species with vertical and horizontal transmission of symbionts.
Understanding biodiversity maintenance when species compete for shared limiting resources remains... more Understanding biodiversity maintenance when species compete for shared limiting resources remains
an outstanding ecological problem. For a half century, the competition–colonization trade-off has been
invoked to explain species coexistence. More recently, asymmetric dispersal has been shown to alter
the conditions for species coexistence under pure scramble competition for space, even in the absence
of spatial heterogeneity. Therefore, in this study, we investigated why and how asymmetric dispersal
may alter the effect of competition–colonization trade-off on species coexistence. Our main findings are
that: (1) self-recruitment of a superior competitor facilitates persistence of an inferior competitor; (2)
the degree to which a community is recruitment-limited influences the threshold dispersal asymmetry
required for persistence of a species with a birth or survival disadvantage; (3) an inferior competitor
with a high recruitment strategy is better able to benefit from spatial asymmetries in dispersal than one
with a high survival strategy, and (4) an inferior competitor may persist, and even exclude the superior
competitor, when dispersal is highly asymmetric (i.e., the competition–colonization trade-off can be
violated). These results underscore the importance of dispersal patterns promoting species coexistence
and their synergies with species’ colonization and competition abilities, and highlight the need to assess
dispersal-mediated coexistence within a framework that incorporates the interactive effects of dispersal
patterns, demographic and competitive strategies.
The establishment of an adequate larval diet for crustacean and fish often involves a series of t... more The establishment of an adequate larval diet for crustacean and fish often involves a series of time-consuming
and expensive trial and errors. Despite being nutritionally poor, rotifers and Artemia are the most commonly used
preys in larviculture. Whether (and to what extent) the prey needs to be enriched with essential fatty acids differs from
species to species. We hypothesized that the DHA content of a newly spawned eggs and its consumption through
embryogenesis can be a good indicator of the need to enrich the prey with DHA. In order to assess this hypothesis,
we performed a search in the scientific literature and compared DHA consumption through embryogenesis with
larval culture success with unenriched and DHA-enriched Artemia nauplii, respectively a prey poor and rich in DHA
of fish and crustacean. Data available from previously published studies suggests that, higher the consumption of
DHA during embryonic development, greater the requirement of a diet rich in DHA during early larval development;
and when, although present, DHA is not consumed during embryogenesis, larvae seem to be able to successfully
develop with diet poor in DHA (i.e. using solely their reserves). Further studies will be necessary to better validate
this hypothesis, but if confirmed, it may allow a reduction of time and costs associated with the establishment of an
adequate larval diet.
Aquaculture, Jan 1, 2008
Larval resistance to temporary starvation is considered a key factor for successful development i... more Larval resistance to temporary starvation is considered a key factor for successful development in the wild. Subjecting larvae to temporary starvation during early and/or late development is occasionally used in larviculture to reduce production costs.Mithraculus forceps is a popular species in the marine aquarium industry for their ability to control nuisance algae in aquarium tanks; a larval culture methodology was previously proposed in order to avoid collection from the wild. In an attempt to reduce production/feeding costs of M. forceps larval culture (two zoea stages and a megalopa), larvae (megalopa stage) were starved after 7 and 8 days post-hatch (DPH); starvation treatments were compared with those of the control treatment where larvae were fed continuously. No differences were found in survival to juvenile, metamorphosis synchronism or larval duration between the treatments, which suggest that at least by day 7 DPH, megalopae have already achieved the point-of-reserve-saturation (PRS) and are able to successfully metamorphose to crab stage without feeding (facultative lecithotrophic); newly metamorphosed juveniles are slightly smaller (particularly the ones starved after 7DPH). This flexible way of development might be very advantageous in the wild and might allow the reduction of costs of larval culture in captivity.
Aquaculture, Jan 1, 2005
The effects of different rearing temperatures, densities, and diets on the larval development, su... more The effects of different rearing temperatures, densities, and diets on the larval development, survival to metamorphosis, settlement synchronism, and fatty acid profile of the ornamental shrimp Lysmata seticaudata were evaluated. Survival of larvae raised at 20 °C was not significantly different (average±standard deviation) (94.8±4.5%) from that of those raised at 26 °C (85.3±9.5%), and presented significantly longer larval durations (31.8±1.0 days) than the ones raised at 26 °C (19.5±1.3 days). Larvae starved in zoea I displayed significantly lower survival (64.7±10.0%), and higher numbers of larvae remained in the last zoeal stage and died before metamorphosing. Larvae fed newly hatched Artemia nauplii, Artemia metanauplii or enriched Artemia metanauplii displayed similar survival (85.3±9.5%, 81.3±5.9%, and 75.5±2.1%, respectively) and similar larval stage durations. Larvae cultured at rearing densities of 10, 20, and 40 larvae l−1 showed similar survival rates (85.3±9.5%, 88.0±1.8%, and 86.8±5.4%, respectively). When cultured at 40 larvae l−1, a significantly higher proportion of larvae remained in the last zoeal stage (13.5±5.9%) 15 days after the settlement of the first postlarva. The survival of larvae fed newly hatched Artemia nauplii, or fed newly hatched Artemia nauplii until zoea V and switched to enriched Artemia metanauplii until settlement did not differ significantly (86.8±5.4% and 87.0±6.0%, respectively). Both treatments showed similar proportions of late stage larvae that did not metamorphose by the 15th day following the first settled postlarva. With the exception of larvae starved in zoea I, and those cultured at 40 larvae l−1, that did not display any “mass settlement period,” settlement mainly occurred during the 3rd and the 7th day following the settlement of the first postlarva. The fatty acid content of postlarvae cultured under different temperatures (20 and 26 °C) and fed the same larval diet (newly hatched Artemia) were similar. With the exception of docosahexaenoic acid (DHA) content, postlarvae fed enriched Artemia metanauplii displayed similar fatty acid content to those displayed by postlarvae fed on newly hatched Artemia and Artemia metanauplii. Wild postlarvae displayed a significantly lower fatty acid content (46.95±2.85 μg/mg dry weight), when compared to cultured organisms. These differences in fatty acid composition were more pronounced on saturated and monounsaturated fatty acids. Wild postlarvae always displayed a significantly higher DHA/EPA ratio (1.01±0.13), even when compared with that of postlarvae fed on enriched Artemia.
Aquaculture, Jan 1, 2006
The clinging crab, Mithraculus forceps (A. Milne Edwards, 1875), has been demonstrated to be a go... more The clinging crab, Mithraculus forceps (A. Milne Edwards, 1875), has been demonstrated to be a good candidate for aquaculture. The present study tests the possibility of using the 2nd clutch produced from wild captured ovigerous females for larval rearing. Although larvae of the 2nd clutch took slightly more time to metamorphose to crab, survivorship to newly settled juveniles (13 days post hatching — DPH) was not significantly different between the 1st clutch (85.7 ± 11.2%) and 2nd clutch (68.3 ± 8.4%). No differences were found in crab carapace length (1.32 ± 0.04 and 1.31 ± 0.03 mm for 1st and 2nd clutches, respectively) between the spawns, although the crabs from the 1st clutch were significantly wider than the ones from the 2nd clutch (1.14 ± 0.04 and 1.06 ± 0.03 mm, respectively). The high survivorship and fast larval development obtained in the 2nd clutch suggest that wild captured ovigerous M. forceps females can store sperm and should be maintained in captivity for multiple spawns.
Aquaculture, Jan 1, 2009
Artemia nauplii are among the most commonly used cultured prey in aquaculture, but they may lack ... more Artemia nauplii are among the most commonly used cultured prey in aquaculture, but they may lack certain essential fatty acids pertinent to their target species. While enrichment can improve Artemia nutritional profile, enrichment procedures can cause undesired effects such as mortality and rapid growth, which is problematic for larvae with a small mouth gape. In this study we tested the effect of salinity (3-33), temperature (16-28°C) and enrichment time (0-24 h) on survival, total length and fatty acid profile of Artemia franciscana nauplii (marine strain) using a factorial design. Results were used to construct an A. franciscana nauplius enrichment model. Temperature was the most important forcing function influencing mortality, growth and fatty acid incorporation; temperature increase caused higher mortality, faster growth and more fatty acid incorporation. Salinity affected primarily growth and arachidonic acid (ARA) incorporation; lower salinities reduced growth and maintained higher ARA levels. The model allowed us to test different combinations of temperature and salinity, predict their outcomes, and consequently, choose the optimal combination of these abiotic factors and enrichment time to produce a prey with the desired properties (a specific total length and fatty acid profile), while minimizing mortality.
World Aquaculture, Jan 1, 2010
Red-clinging crabs Mithraculus forceps are used for their ability to control nuisance algae in ma... more Red-clinging crabs Mithraculus forceps are used for their ability to control nuisance algae in marine aquariums. Their larval and juvenile culture protocol has already been successfully developed. The objective of this work is to build a model that integrates the effect of different abiotic and biotic factors (temperature, stocking density, prey density), as well as space (number and volume of tanks) in production and economic parameters (costs of feed, labour and maintenance, market price and profit). The model aimed to be used as a tool to support management decisions. Overall, the model was able to integrate previously collected data and produce expected forecasts of M. forceps larval and juvenile culture reared under different combinations of temperature, stocking density, and prey density. Sensitivity analysis revealed that temperature was the most important factor regulating survival and growth, and consequently profit. According to the model, a batch of 1500 larvae reared in ten 10 L tanks in optimal conditions (10 prey mL − 1 and 28°C) and then, as juveniles, in a 3 m 2 water table at 28°C, is expected to reach commercial size in 225 days.
Journal of Crustacean Biology, Jan 1, 2008
We examined potential fertility, egg volume, and water, lipid, and fatty acid content through emb... more We examined potential fertility, egg volume, and water, lipid, and fatty acid content through embryogenesis in a population of female U. rapax from Sebastian Inlet, Florida. Carapace width (CW) ranged from 10.80 to 20.09 mm (N ¼ 184), and each female carried 5000 to 30,000 eggs in the last stage of development. Female CW was found to be a good predictor of the number of eggs in the later stage of development (potential fertility ¼ 7.908 CW 2.7655 , R 2 ¼ 0.749). Egg volume increases (from 0.0079 to 0.0134 mm 3 ) was mildly correlated (r ¼ 0.79) with an increase in egg water content (from 60 to 69%). Egg lipid and fatty acid content decreased through embryogenesis, due to its importance as energy source. The most consumed fatty acids were the monounsaturated (97.81 lg . mg dw À1 ) followed by the saturated (64.34 lg Á mg dw À1 ) and polyunsaturated (38.69 lg Á mg dw À1 ). Fatty acids 16:0, 18:2n-6, 16:1n-7, and 18:2n-6 are consumed preferentially (39.91, 38.45, 29.4 and 23.93 lg Á mg dw À1 , respectively), while essential polyunsaturated fatty acids, particularly docosahexaenoic acid (22:6n-3) and eicosapentaenoic acid (20:5n-3), are conserved. Egg fatty acid profile also reflects diet and habitat of adults. A medium-low EPA/DHA ratio suggests U. rapax occupies a medium trophic level. The low ratio (18:1n-7/18:1n-9) and high percentages of 18:1n-9 fatty acid (18%) and essential C 18 and C 20 polyunsaturated fatty acids (19-23%) suggests adults are omnivores consuming primary producers (like algae and mangrove leaves) and small invertebrates. The high percentage of odd-numbered fatty acids (above 3-3.5%) also suggests scavenger/detritivore behaviour.
Journal of the Marine …, Jan 1, 2008
Ornamental crabs of the genus Mithraculus (Decapoda: Brachyura: Majidae) are utilized in reef aqu... more Ornamental crabs of the genus Mithraculus (Decapoda: Brachyura: Majidae) are utilized in reef aquaria to control nuisance algae, particularly bubble algae. Although Mithraculus have modified, spooned-shaped chelae to feed on both fleshy and filamentous algae, they may consume alternative foods offered in a reef aquarium. The objective of this study was to determine the efficiency of using Mithraculus sculptus to control the bubble alga Ventricaria ventricosa (Siphonocladales-Cladophorales complex, Chlorophyta) in the presence of alternative foods (commercial pellets and frozen mysids) commonly utilized in reef aquaria. Results indicated that medium and large sized crabs consumed more bubble algae than smaller conspecifics. Although, M. sculptus first chose alternative foods to bubble alga (77% and 69% of the time chose pellets and frozen mysids, respectively), algal consumption only decreased significantly if, besides algae, pellets were provided; when only algae were provided, algal consumption was similar to when they were provided with mysids. The prey choice model was used as a conceptual framework to study the mechanisms underlying active selection; food energy content and handling time were measured and food profitability was calculated. Handling time decreased with increasing crab size. Pellets presented a higher profitability than algae but mysids and algae presented similar profitability; this seems to be in agreement with the observed reduced algal consumption when pellets made part of the diet. Mithraculus sculptus feeding behaviour on V. ventricosa recorded with digital high-speed video (DHSV) suggests that as the crab tears the algal cell apart, the cell liquid that contains juvenile cytoplasmatic spheres is released into the water; this behaviour might contribute to algal dispersal and consequently algal infestation.
Landscape ecology, Jan 1, 2011
We developed a mathematical model with two-way linked socio-ecological dynamics to study farmland... more We developed a mathematical model with two-way linked socio-ecological dynamics to study farmland abandonment and to understand the regimes shifts of this socio-ecological system. The model considers that migration is a collective behavior socio-economically driven and that the ecosystem is dynamic. The model identifies equilibria that vary from mass migration, farmland abandonment, and forest regeneration, to no migration and forest eradication; partial migration and/or coexistence of farmland and forest also constitute possible equilibria. Overall, the model reflects farmland abandonment processes observed in the field and illustrates the importance of the complex interlinked mechanisms between the social and ecological systems determining farmland abandonment, that are not evident when approached independently. The model dynamics show that the hysteresis on the social dynamics renders regimes shifts difficult to reverse, and that this difficulty is accentuated when considering the ecological system dynamic. Similar models could be applied to other socio-ecological systems to help their management.
Journal of the Marine Biological …, Jan 1, 2008
Fatty-acid and energy content of Maja brachydactyla eggs at different developmental stages (recen... more Fatty-acid and energy content of Maja brachydactyla eggs at different developmental stages (recently spawned, half-developed and ready to hatch) were analysed in order to understand what is being consumed and produced during the embryonic development. Egg volume increased during development (34%, 0.187 to 0.285 mm 3 , N ¼ 270) and was negatively correlated with egg energy and fatty-acid content (r ¼ 20.80 and r ¼ 20.46, respectively), which decreased through embryogenesis. The most consumed fatty acids were the PUFA (21.2 mg . mg dw 21 ), followed by the SFA (18.8 mg . mg dw 21 ) and MUFA (14.9 mg . mg dw 21 ). Palmitic (16:0), oleic (18:1n-9) and eicosapentaenoic (EPA, 20:5n-3) acids were preferentially consumed (13.14, 9.21 and 8.67 mg . mg dw 21 , respectively). The fatty acid composition found in M. brachydactyla eggs reflected the habitat and omnivorous and detritivorous scanvenger diet of the adults, although the consumption of algae was more important than previously thought, at least in the area where these adults were captured. Pre-hatching eggs have a high PUFA content (64.5 mg . mg dw 21 or 46.3% of the egg fatty-acid content). We conclude that larvae of this species might need a diet rich in PUFA, particularly EPA and DHA, for successful development. From the culture perspective, live preys commonly used in aquaculture will likely require to be enriched with DHA.
The 93rd ESA Annual …, Jan 1, 2008
Red-clinging crabs Mithraculus forceps are used for their ability to control nuisance algae in ma... more Red-clinging crabs Mithraculus forceps are used for their ability to control nuisance algae in marine aquariums. Their larval and juvenile culture protocol has already been successfully developed. The objective of this work is to build a model that integrates the effect of different abiotic and biotic factors (temperature, stocking density, prey density), as well as space (number and volume of tanks) in production and economic parameters (costs of feed, labour and maintenance, market price and profit). The model aimed to be used as a tool to support management decisions. Overall, the model was able to integrate previously collected data and produce expected forecasts of M. forceps larval and juvenile culture reared under different combinations of temperature, stocking density, and prey density. Sensitivity analysis revealed that temperature was the most important factor regulating survival and growth, and consequently profit. According to the model, a batch of 1500 larvae reared in ten 10 L tanks in optimal conditions (10 prey mL− 1 and 28 °C) and then, as juveniles, in a 3 m2 water table at 28 °C, is expected to reach commercial size in 225 days.
Aquaculture, Jan 1, 2007
In the present study, by using accumulated information of Mithraculus forceps larval and juvenile... more In the present study, by using accumulated information of Mithraculus forceps larval and juvenile rearing, survival, growth/size and productivity models were developed, allowing for optimization and improvement of the culture methodology of this species. By taking into account the productivity, we estimated larval optimal conditions as: 60 larvae.L− 1 and 10 Artemia nauplii.mL− 1. For juveniles we estimated optimal conditions as: 12 900 crabs.m− 2 and feed juveniles with Artemia nauplii, if possible supplemented with Amphora microalgae.
Journal of the …, Jan 1, 2003
Portuguese sole, Synaptura lusitanica, were collected from the Portuguese coast, between April 20... more Portuguese sole, Synaptura lusitanica, were collected from the Portuguese coast, between April 2001 and March 2002, to examine feeding habits, age and growth, and sexual cycle. Synaptura lusitanica fed on few prey items, its diet mainly composed of polychaeta, bivalvia and cephalochordata. Signi¢cant di¡erences were found between the proportion of prey items according to season, length class of ¢sh and coastal area. The main di¡erences related to ¢sh size were the higher ingestion of bivalvia by larger ¢sh, in the west coast area, and the increase in the important cephalochordata for ¢sh larger than 300 mm total length, in the south coastal areas. Polychaeta presented a lower importance in the spring^summer period while bivalvia increased its values in the autumn^winter period. Cephalochordata were more important in the autumn^winter period, but only for ¢sh larger than 300 mm total length and in the south coastal areas. Vacuity was extremely high (mean value of 52%). Ages of S. lusitanica were determined from sagittae otoliths. The length of ¢sh analysed varied from 157 mm to 480 mm, and the oldest ¢sh was age 8. The von Bertalan¡y growth equation parameters di¡ered little between sexes, being the asymptotic length obtained for females higher compared to males. The highest values of the gonadosomatic index were obtained in summer, which was the period when the highest percentage of individuals in the spawning stage were recorded. Therefore, the spawning season seems to be from mid-spring (May) until the end of summer (September).
Marine Biology, Jan 1, 2008
Aquaculture, Jan 1, 2006
The Monaco shrimp Lysmata seticaudata (Risso, 1816) is a marine ornamental species whose ecology ... more The Monaco shrimp Lysmata seticaudata (Risso, 1816) is a marine ornamental species whose ecology and biology, as well as its larval culture has previously been addressed. The objective of the study was to predict and improve productivity of this species rearing protocol through modelling. The models developed intend to help aquaculturists to maximize survival to postlarva, decrease larval duration and increase synchronism of metamorphosis and newly metamorphosed postlarvae size by manipulating temperature, diet, first feeding period and stocking density.The models developed allow us to conclude that the L. seticaudata rearing protocol productivity can be improved by raising larvae at a density of 40 larvae L− 1 and fed newly hatched Artemia nauplii since hatching to zoea V, and with Algamac 2000™ enriched Artemia metanauplii from zoea V to metamorphosis to postlarvae.By providing more productive protocols to aquaculturists, destructive practices and wild collection may be reduced.
Journal of Sea …, Jan 1, 2003
The Portuguese sole, Synaptura lusitanica Capello, 1868, is distributed from Portugal to Angola. ... more The Portuguese sole, Synaptura lusitanica Capello, 1868, is distributed from Portugal to Angola. In Portugal, it occurs on the west coast and on the south-eastern coast. The genetic and morphological variation of S. lusitanica was studied based on protein electrophoresis and morphometric and meristic analyses of samples collected in four areas along the Portuguese coast. The genetic analysis was based on 12 loci, 10 of which were polymorphic. The morphological analysis included 12 morphometric measurements and 7 meristic counts. Both analyses indicated divergence between the west coast sample (Setúbal) and the other samples collected in the south-eastern coast (Olhão, Tavira and Vila Real de Santo António). Although the discreteness of the west coast individuals of S. lusitanica was not completely evident, a conservative approach to the fisheries management of this species would consider two independent stocks.
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Papers by Joana Figueiredo
an outstanding ecological problem. For a half century, the competition–colonization trade-off has been
invoked to explain species coexistence. More recently, asymmetric dispersal has been shown to alter
the conditions for species coexistence under pure scramble competition for space, even in the absence
of spatial heterogeneity. Therefore, in this study, we investigated why and how asymmetric dispersal
may alter the effect of competition–colonization trade-off on species coexistence. Our main findings are
that: (1) self-recruitment of a superior competitor facilitates persistence of an inferior competitor; (2)
the degree to which a community is recruitment-limited influences the threshold dispersal asymmetry
required for persistence of a species with a birth or survival disadvantage; (3) an inferior competitor
with a high recruitment strategy is better able to benefit from spatial asymmetries in dispersal than one
with a high survival strategy, and (4) an inferior competitor may persist, and even exclude the superior
competitor, when dispersal is highly asymmetric (i.e., the competition–colonization trade-off can be
violated). These results underscore the importance of dispersal patterns promoting species coexistence
and their synergies with species’ colonization and competition abilities, and highlight the need to assess
dispersal-mediated coexistence within a framework that incorporates the interactive effects of dispersal
patterns, demographic and competitive strategies.
and expensive trial and errors. Despite being nutritionally poor, rotifers and Artemia are the most commonly used
preys in larviculture. Whether (and to what extent) the prey needs to be enriched with essential fatty acids differs from
species to species. We hypothesized that the DHA content of a newly spawned eggs and its consumption through
embryogenesis can be a good indicator of the need to enrich the prey with DHA. In order to assess this hypothesis,
we performed a search in the scientific literature and compared DHA consumption through embryogenesis with
larval culture success with unenriched and DHA-enriched Artemia nauplii, respectively a prey poor and rich in DHA
of fish and crustacean. Data available from previously published studies suggests that, higher the consumption of
DHA during embryonic development, greater the requirement of a diet rich in DHA during early larval development;
and when, although present, DHA is not consumed during embryogenesis, larvae seem to be able to successfully
develop with diet poor in DHA (i.e. using solely their reserves). Further studies will be necessary to better validate
this hypothesis, but if confirmed, it may allow a reduction of time and costs associated with the establishment of an
adequate larval diet.
an outstanding ecological problem. For a half century, the competition–colonization trade-off has been
invoked to explain species coexistence. More recently, asymmetric dispersal has been shown to alter
the conditions for species coexistence under pure scramble competition for space, even in the absence
of spatial heterogeneity. Therefore, in this study, we investigated why and how asymmetric dispersal
may alter the effect of competition–colonization trade-off on species coexistence. Our main findings are
that: (1) self-recruitment of a superior competitor facilitates persistence of an inferior competitor; (2)
the degree to which a community is recruitment-limited influences the threshold dispersal asymmetry
required for persistence of a species with a birth or survival disadvantage; (3) an inferior competitor
with a high recruitment strategy is better able to benefit from spatial asymmetries in dispersal than one
with a high survival strategy, and (4) an inferior competitor may persist, and even exclude the superior
competitor, when dispersal is highly asymmetric (i.e., the competition–colonization trade-off can be
violated). These results underscore the importance of dispersal patterns promoting species coexistence
and their synergies with species’ colonization and competition abilities, and highlight the need to assess
dispersal-mediated coexistence within a framework that incorporates the interactive effects of dispersal
patterns, demographic and competitive strategies.
and expensive trial and errors. Despite being nutritionally poor, rotifers and Artemia are the most commonly used
preys in larviculture. Whether (and to what extent) the prey needs to be enriched with essential fatty acids differs from
species to species. We hypothesized that the DHA content of a newly spawned eggs and its consumption through
embryogenesis can be a good indicator of the need to enrich the prey with DHA. In order to assess this hypothesis,
we performed a search in the scientific literature and compared DHA consumption through embryogenesis with
larval culture success with unenriched and DHA-enriched Artemia nauplii, respectively a prey poor and rich in DHA
of fish and crustacean. Data available from previously published studies suggests that, higher the consumption of
DHA during embryonic development, greater the requirement of a diet rich in DHA during early larval development;
and when, although present, DHA is not consumed during embryogenesis, larvae seem to be able to successfully
develop with diet poor in DHA (i.e. using solely their reserves). Further studies will be necessary to better validate
this hypothesis, but if confirmed, it may allow a reduction of time and costs associated with the establishment of an
adequate larval diet.