Energy metabolism during development of eggs and larvae of gilthead sea bream (Sparus aurata)

Developing eggs and larvae of laboratory-reared gilthead sea bream (Sparus aurata) maintained in filtered seawater (40 ppt) at 18°C, were measured for oxygen uptake, ammonia excretion, contents of free amino acids (FAA), protein, fatty acids (FA) accumulated ammonia, and volumes of yolk-sac and oil globule. Absorption of the yolk coincided with the consumption of FAA and was complete ca. 100 h post-fertilisation. Amino acids from protein were mobilised for energy in the last part of the yolk-sac stage. Absorption of the oil globule occurred primarily after hatching following yolk absorption, and correlated with catabolism of the FA neutral lipids. Overall, FAA appear to be a significant energy substrate during the egg stage (60 to 70%) while FA from neutral lipids derived from the oil globule are the main metabolic fuel after hatching (80 to 90%).     

The importance of free amino acids to the energy metabolism of eggs and larvae of turbot (Scophthalmus maximus)

A study was undertaken to establish the role of free amino acids (FAA) in aerobic energy dissipation in embryos of turbot (Scophthalmus maximus) which contain an oil globule in the egg. Laboratory-reared developing eggs and larvae (15°C, 34 salinity) were measured for oxygen uptake, ammonia excretion, contents of FAA, protein, and ammonium, and volumes of yolksac and oil globule. Newly spawned eggs from different batches contained 55 to 90 nmol egg^–1 of FAA. Resorption of FAA occurred in parallel with the consumption of yolk. Resorption of the oil globule, however, occurred predominantly after hatching and mainly after yolk resorption. The combined data suggest that approximately 70% of the FAA are utilized as an energy substrate, while the rest are polymerized into body proteins. FAA become a significant energy substrate in the early egg stage and account for 100% of the aerobic energy dissipation 2 d after Fertilization then decrease to ca. 60% at the time of hatching. Lipids derived from the oil globule seem to be the main fuel after hatching and account for ca. 90% of the energy dissipation at the onset of first-feeding. Thus, the energetics of fish embryos which contain an oil globule seems to be different from those that depend exclusively on the nutritional reserves of the yolk.     

Energetics of early development for the sea urchinsStrongylocentrotus purpuratus andLytechinus pictus and the crustaceanArtemia sp.

Embryos and larvae of two species of sea urchin,Strongylocentrotus purpuratus andLytechinus pictus, and larvae of the brine shrimpArtemia sp. (San Francisco brand) were cultured to investigate the contribution of dissolved organic material in seawater to the energetics of early development. When embroys ofS. purpuratus were reared in artificial seawater, a net loss in dry organic mass was observed. In contrast, when sibling embryos were reared to Day 2 under identical conditions in natural seawater, there was either a net increase in dry organic mass or no change. A net decrease in mass was observed in only one of five cultures reared in filtered natural seawater. Energy budgets for each species were determined by giving energy equivalents to the changes in carbohydrate, lipid and protein, and to the rate of oxygen consumption for each day of development. In the case ofS. purpuratus, the use of endogenous reserves accounted for either 0 or 38% of the metabolic demand for two independent cultures reared from Days 0 to 2. For larvae ofL. pictus, reared to 8 d, only 66% of the metabolic demand could be accounted for by the use of endogenous reserves. Sea urchins are capable of transporting dissolved organic material from seawater. Calculations revealed that the energy deficit during the early development of sea urchins (S. purpuratus) could be accounted for by the uptake of dissolved organic matter from seawater. However, for a species that cannot use this resource (Artemia sp.), the metabolic needs during development are supplied through the use of endogenous reserves.     

Female reproductive biology and oocyte development of the red frog crab,Ranina ranina,off Hachijojima,Izu Islands,Japan

Speciments of the red frog crab, Ranina ranina, examined in this study were collected off Hachijojima, Japan from 1987–1988 and 1990–1991. Ovigerous females occurred from May to September, and their carapace length ranged from 61.8 to 102.1 mm. Minimum size at the maturity was estimated to be 50 to 60 mm carapace length. The lobule-type ovary had a longitudinal ovarian cavity at the center. Germinal zones were located along the sides of the cavity. Oogenesis was divided into five main and ten detailed stages: proliferation (oogonium); previtellogenesis (bouquet, early chromatin nucleolus, late chromatin nucleolus); primary vitellogenesis (oil globule and yolk granule); secondary vitellogenesis (primary yolk platelet, secondary yolk platelet and prematuration); and maturation (maturation) stages. Vitellogenesis started at the oil globule stage when weakly positive periodic acid-Schiff granules appear in the cytoplasm. Based on the gonadosomatic index and histological changes in ovary, the reproductive cycle was divided into five stages: multiplication, from December to January; developing, from February to March; ripe in April and early May; spawning, from late May to August; and recovery, from August to November. Each crab spawned more than once during the spawning season.     

Oocyte development in the kuruma prawn Penaeus japonicus

Female kuruma prawns (Penaeus japonicus Bate) with undeveloped, early developing, developing, nearly ripe and ripe ovaries, were collected from Ise Bay, Japan, in 1984. Oocyte development of the kuruma prawn was classified into ten stages according to morphological characters, namely: (1) synapsis stage, (2) chromatin nucleolus stage, (3) early perinucleolus stage, (4) late perinucleolus stage, (5) oil globule Stage I, (6) oil globule Stage II, (7) yolkless stage, (8) yolk granule stage, (9) prematuration stage, and (10) maturation stage. The synapsis stage is a multiplication stage. The chromatin nucleolus stage, early and late perinucleolus stages are previtellogenesis and primary growth stages. Oil globule Stage I is an initial stage of primary vitellogenesis and secondary growth. Follicle cells on the oil globule Stage I oocytes expand rapidly and reach maximum size during oogenesis. Yolk granule stage oocytes are in the initial stages of secondary vitellogenesis. Strongly acidophilic yolk granules accumulate within basophilic vesicles of the cytoplasm. The yolk granules are first concentrated in the inner part of the cytoplasm, then gradually spread to the periphery. Cortical crypts, which are separated from the oocyte cytoplasm by the cytoplasmic membrane, are situated outside of oocyte cytoplasm. Germinal vesicle breakdown (GVBD) is initiated in the late phase of prematuration and continues until the late phase of maturation immediately prior to spawning. At the beginning of the maturation stage, the oocytes are ovulated, after which the nuclei further shrink and migrate out-wards. After ovulation, meiotic division of the ovarian oocyte progressed up to the metaphase of primary maturation division. Finally, the meiotic metaphase is visible just beneath the cytoplasmic membrane in the mature oocyte. Though ovulation is synchronous within the same ovary, GVBD is not completely synchronous. Ovulated mature oocytes have many club-shaped cortical crypts in the peripheral part of the cytoplasm and contain extensive accumulations of yolk granules dispersed throughout the cytoplasm. The apical end of the club-shaped cortical crypts and cytoplasmic membrane are coated by the vitellin envelope in the mature oocyte.     

Route of egg yolk protein uptake in the oocytes of kuruma prawn,Penaeus japonicus

The route of egg yolk protein uptake into the oocytes of kuruma prawn, Penaeus japonicus, was studied using immunohistochemical and electron microscopical methods. Although a significant immunofluorescence with anti-vitellin-immunoglobulin was observed in the enlarged follicle cells surrounding oil globule stage oocytes of the early vitellogenic ovary, no fluorescence was detected in shrunken follicle cells surrounding oocytes in the yolk granule stage. Electron microscopically, yolk granule stage oocytes have an irregular surface with numerous well-developed microvilli. In contrast, the surface of follicle cells is relatively smooth. The irregular surface of yolk granule stage oocytes was covered with a layer of electron dense material. Similar dense material was found in the spaces between the neighboring follicle cells on the yolk granule stage oocytes. The outer surface of the follicle cells on yolk granule stage oocytes was covered by dense materials which were similar to those found on the irregular surface of oocytes. Micropinocytotic vesicles containing dense material were found in the ooplasm near the irregular surface with numerous well-developed microvilli. Dense material was concentrated in the peripheral part of the small forming yolk bodies of yolk granule stage oocytes. This suggests that the electron dense material, probably egg yolk protein, transferred to the surface of yolk granule stage oocytes from the spaces between the neighboring follicle cells may be incorporated into the ooplasm by pinocytosis through the microvilli and subsequently aggregate to form yolk bodies.     

Control of food influx by temporal subcastes in the fire ant,Solenopsis invicta

Summary Temporal subcastes in the fire ant, Solenopsis invicta Buren were selectively starved to determine if foragers could assess the nutritional status of their nestmates and respond accordingly. We found that starved foragers increase the honey entering the colony (Fig. 1). When nurses are starved more oil and liquid egg yolk enters the colony (Figs. 2, 3) and when both reserves and nurses are starved, more egg yolk powder is brought in by the foragers (Fig. 4). When queens are starved, more liquid egg yolk and oil enters the colony (Figs. 2, 3). Starved larvae increase the oil in the colony (Fig. 2) and when held with nurses for 24h before feeding, increase the egg yolk powder brought in and receive significantly more of it than other subcaste members (Fig. 5). We conclude that foragers can respond to the nutritional needs of their nestmates. Based on our behavioural observations, the quantity of food brought in by the foragers is regulated via discriminatory solicitation by reserves in response to the nutritional needs of the nurses.     

Assimilation of dissolved glucose from sea water by the sea bass Dicentrarchus labrax and the sea bream Sparus aurata

Larvae of sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) were transferred to normal or glucose-enriched sea water immediately after mouth opening to assess their ability to absorb and assimilate glucose at the beginning of the larval period. Assimilation was monitored by histological and cytochemical analysis of the liver. The results showed that (1) the larvae of both species regularly ingested water, (2) glucose absorption resulted in glycogen accumulation in the hepatocytes (this was more marked in sea bass than in sea bream), and (3) glucose delayed the pathological effects of fasting. Consideration of metabolic derivatives indicates that hepatic glycogen probably arises from neoglucogenesis.     

Fish predators and scavengers of the sea urchin Paracentrotus lividus in protected areas of the north-west Mediterranean Sea

Direct observations of predation on 436 individuals of the sea urchin Paracentrotus lividus (Lamarck) were carried out in infralittoral rocky bottoms (between 5 and 20 m deep) in three Mediterranean marine reserves. The predator guild was composed of six fish species, the sparids Diplodus sargus and D. vulgaris being the main predators, and the labrid Coris julis a major predator of juvenile sea urchins. Four species attempted but failed to open sea urchins. The scavenger guild was most rich in species, with 17 species observed. Predation was size-dependent; the size of predators increased with increasing size of the sea urchins. The presence of two feeding guilds is suggested, one composed of sparids (Diplodus spp.), able to kill juvenile and adult sea urchins, and the other composed of labrids (mainly C. julis), which feed on juvenile sea urchins. To avoid the extension of overgrazed, barren areas created by P. lividus populations, fisheries' regulations should focus on major sea-urchin predators, chiefly D. sargus, D. vulgaris and C. julis. Received: 23 April 1997 / Accepted: 30 May 1997     

The reproductive biology of echinothuriid and cidarid sea urchins from the deep sea (Rockall Trough,North-East Atlantic Ocean)

The reproductive biology of 5 species of echinothuriid (Phormosoma placenta, Calveriosoma hystrix, Araeosoma fenestrum, Sperosoma grimaldii and Hygrosoma petersii) and 2 species of cidarid (Cidaris cidaris and Poriocidaris purpurata) sea urchins from the deep sea (Rockall Trough) has been examined from samples collected during 1973–1983. In all species the gonads lie within the interambulacrum attached to aboral gonopores and when fully developed occupy most of the test not occupied by the gut or Aristotle's lantern. In all the species, initial oocyte development takes place along the germinal epithelium embedded in nutritive tissue. In all the echinothuriids and in Poriocidaris purpurata, the oocyte grows to ca. 200 to 450 m, at which stage vitellogenesis begins. Oocyte growth continues until a maximum egg size of 1 100 to 1 500 m is attained. In the echinothuriids, two types of nutritive tissue are found. In the carly stages of gametogenesis the oocyte is surrounded by well-structured periodic acid Schiff (PAS)-positive tissue. As the oocyte grows this tissue becomes vacuolated, suggesting that there is a transfer of nutriment to the developing oocyte. In Phormosoma placenta, unspawned oocytes are phagocytosed. There is no evidence of seasonality in any of the echinothuriid species or in Poriocidaris purpurata. Extrapolation with shallow-water echinothuriids suggests that larval development is lecithotrophic, omitting any planktotrophic phase. Of the species examined, only Cidaris cidaris has a reproductive strategy which produces a known larva, although the limited samples did not permit any determination of seasonality in this deep-sea population.     

Seasonal changes in feeding, gonad development and lipid stores in Calanusfinmarchicus and C. hyperboreus from Malangen, northern Norway

 Seasonal dynamics of feeding activity, oil sac volume, gonad development, sex ratio and spawning periods in the two sibling species Calanusfinmarchicus and C. hyperboreus, the key zooplankton copepod organisms throughout the northern Atlantic waters, were studied simultaneously in Malangen, northern Norway, during 1992. We were also tracing differences in surface- and deep-dwelling components of these populations in terms of oil sac volume and gonad development during the time period when the G₁ is preparing for a subsequent generation (G₂) or hibernation. The main difference in the life cycle strategies of these species is the earlier maturation and spawning of C. hyperboreus. No feeding activity in either of the two species was found in February, but both commenced feeding in March, prior to the spring phytoplankton peak. The larger copepod, C. hyperboreus, had a more intensive energy deposition than C. finmarchicus. The period of active feeding was much shorter for the former species, only from March through July in copepodite stages CIV and CV, and even less in females – March and April. Basically, a similar pattern of seasonal changes in gonad length and lipids was observed in the two species. In June, oil sacs in the surface- and deep-dwelling specimens were about equal, during the rest of the year, lipids in the deep CVs exceeded those in the surface. We propose that as copepods accumulated sufficient lipid reserves, they started to descend, while others, containing less fat, stayed in the upper layers feeding. The mean length of the gonads in the surface-dwelling copepods was consistently less than in their deep counterparts from October to February, so that gonad development at the expense of accumulated reserves during resting stage was confirmed. C. finmarchicus males were found in considerable numbers only in February and March, and were only occasionally found in the upper layers (0–100 m), while adult male C. hyperboreus were present from October to March, but were never found in the surface layers. The differences in life cycle timing among the two species are discussed in relation to tradeoffs with regard to foraging strategies, generation numbers, bioenergetics and predator avoidance. Received: 31 March 1999 / Accepted: 23 November 1999     

Yolk resorption,onset of feeding and survival potential of larvae of three tropical marine fish species reared in the hatchery

This paper provides basic early life-history information on milkfish (Chanos chanos), seabass (Lates calcarifer) and rabbitfish (Siganus guttatus) which may explain in part the observed differences in their survival performance in the hatchery. Egg size, larval size, amount of yolk and oil reserves and mouth size are all greater in milkfish than in seabass, and greater in the latter than in rabbitfish. During the first 24 h after hatching, rabbitfish larvae grow much faster than milkfish and seabass larvae at similar ambient temperatures (range 26°–30°C, mean about 28°C). The eyes become fully pigmented and the mouths open earlier in seabass and rabbitfish (32–36 h from hatching) than in milkfish (54 h). Seabass larvae learn to feed the earliest. Yolk is completely resorbed at 120 h from hatching in milkfish, and yolk plus oil at 120 h in seabass and 72 h in rabbitfish at 26° to 30°C. Milkfish and seabass larvae have more time than rabbitfish to initiate external feeding before the endogenous reserves are completely resorbed. Delayed feeding experiments showed that 50% of unfed milkfish larvae die at 78 h and all die at 150 h from hatching. Milkfish larvae fed within 54 to 78 h after hatching had improved survival times: 50% mortality occurred at 96 to 120 h, and 10 to 13% survived beyond 150 h. Unfed seabass larvae all died at 144 h, while 6 to 13% of those fed within 32 to 56 h after hatching survived beyond 144 h and well into the subsequent weeks. Unfed rabbitfish larvae all died at 88 h, while 7 to 12% of those fed within 32 to 56 h after hatching survived beyond 88 h. A delay in initial feeding of more than 24 h after eye pigmentation and opening of the mouth may be fatal for all three species.Contribution No. 167 from the SEAFDEC Aquaculture Department     

The association of N2-fixing bacteria with sea urchins

Dinitrogen fixation associated with bacteria in the gastrointestinal tract of sea urchins appears to be a widespread phenomenon: sea urchins from the tropics (Diadema antillarum, Echinometra lacunter, Tripneustes ventricosus), the temperature zone (Strongylocentrotus droebachiensis) and the arctic (S. droebachiensis) exhibited nitrogenase activity (C₂H₂ reduction). Pronounced seasonal variation was found in nitrogenase activity of temperate sea urchins feeding on kelp (Laminaria spp.) and eelgrass (Zostera marina). The mean monthly nitrogenase activity was inversely correlated with the nitrogen content of the sea urchin's food, which varied up to fivefold over the course of a year. The highest rate of nitrogenase activity recorded for a temperate sea urchin during the 14 month sampling period was 11.6g N fixed g wet wt^-1 d^-1, with a yearly mean activity of 1.36 g N fixed g wet wt^-1 d^-1. Studies with ¹⁵N confirmed the C₂H₂ reduction results and showed incorporation of microbially-fixed nitrogen into S. droebachiensis demonstrating that N₂ fixation can be a source of N for the sea urchin. Laboratory experiments indicated that part of the sea urchin's (S. droebachiensis) normal gastrointestinal microflora is responsible for the observed nitrogenase activity.     

Antibacterial activity of the marine blue-green alga Trichodesmium erythraeum in the gastro-intestinal contents of the sea gull Laurus brunicephalus

The gastro-intestinal contents of the sea gull Laurus brunicephalus Jerdon were found to possess antibacterial activity. This activity could be traced to heavy accumulations of the marine blue-green alga Trichodesmium erythraeum in the gut. During 1969, a bloom of T. erythraeum began in Porto Novo waters about the middle of February, and attained a peak during the second week of March. It has been reported previously by the author that antibacterial properties are exhibited by T. erythraeum maintained in laboratory cultures, as well as in water samples collected from a red tide area. It was also reported (Ramamurthy, 1970) that the gut contents in 2 pelagic fishes, Hilsa kanagurta and Rastrelliger kanagurta, collected during the same red tide bloom period, possessed antibacterial properties. During this period large numbers of these fishes were consumed by sea gulls L. brunicephalus. In view of this finding, experimental procedures were adopted to determine whether extracts of T. erythraeum occurring in the gut of the sea gulls might exhibit antibacterial activity. It was found that T. erythraeum collected from the gut of L. brunicephalus could inhibit both gram positive and gram negative bacteria. Gastro-intestinal extracts from L. brunicephalus collected during the non-bloom period of T. erythraeum showed heavy microbial growth of bacteria and fungi. Evidently, antibacterial or sterile conditions prevail in the gut of these tropical sea gulls in a manner similar to that observed in Polar penguins by Sieburth (1959, 1961).     

Effects of starvation,and light and dark on the energy metabolism of symbiotic and aposymbiotic sea anemones,Anthopleura elegantissima

Rates of oxygen and carbon-dioxide exhange were measured in symbiotic and aposymbiotic specimens of the sea anemone Anthopleura elegantissima while fed and starved under light or dark conditions. Respiratory quotients indicated that fed anemones switched from a carbohydrate to a fat catabolism when starved, with the exception that symbiotic individuals starved in the light showed a pronounced carbohydrate catabolism for over 1 month. The source of the carbohydrate was probably photosynthate translocated by the dinoflagellate Symbiodinium (=Gymnodinium) microadriaticum (Freudenthal) living in the anemones' tissues. The starved symbiotic anemones maintained in the light had lipid levels not significantly different from fed controls and 44 to 61% higher than starved aposymbiotic anemones after 1 month. Thus, the quality and quantity of the metabolic flux from the symbionts to the sea anemone were sufficient to conserve the host's lipid reserves.     

The effects of predator abundance and habitat structural complexity on survival of juvenile sea urchins

We studied the effect of the abundance of predatory fishes and structural complexity of algal assemblages on the survival of juveniles of the sea urchin Paracentrotus lividus on Mediterranean infralittoral rocky bottoms. Post-settlement juveniles (2–10 mm) were placed on four distinct natural substrates with increasing structural complexity (coralline barren, algal turf, erect fleshy algal assemblages and small crevices) inside and outside the Medes Islands Marine Reserve. Predation on these sea urchins increased at greater abundance of predatory fishes, and decreased with greater structural complexity. The refuge provided by structural complexity, however, decreased with increasing size of sea urchin recruits. Predation on the smallest post-settlers was carried out almost exclusively by small fishes (<20 cm), mainly the labrid Coris julis, while the dominant predator of larger juveniles was the sparid Diplodus sargus. Our results demonstrate the cascading effects caused by the prohibition of fishing in marine reserves, and highlight the potential role of small predatory fishes in the control of sea urchin populations.Communicated by O. Kinne, Oldendorf/Luhe     

Abalones and sea urchins in an area inhabited by sea otters

Abalones (Haliotis spp.) and sea urchins (Strongylocentrotus spp.) are part of the subtidal fauna in the kelp bed off Hopkins Marine Station, Pacific Grove, California, USA, a protected marine reserve. Although these animals have been preyed upon by sea otters for over 10 years, their densities are gubstantial (Haliotis spp.: 0.21/m²; Strongylocentrotus spp.: 0.22/m²), and two species, H. rufescens (Swainson) and S. purpuratus (Stimpson), have wide size distributions indicating broad age ranges. Most of the adult abalones and sea urchins occur clustered deep in crevices, either as a direct result of sea-otter predation or because ample drift of algal food reduces foraging activities. Abalones tend to occur in larger crevices than sea urchins, and competition for suitable crevice space may exist among these large, invertebrate, algal-drift feeders.     

Effects of temperature on oxygen consumption,growth, and development of embryos and yolk-sac larvae of Siganus randalli (Pisces: Siganidae)

Eggs from laboratory spawnings of the coralreef fish Siganus randalli Woodland were incubated at two temperatures (27 and 30 °C). Eggs and larvae were sampled until larval starvation, while changes in oxygen consumption, growth, yolk utilization, and development were monitored. Oxygen consumption, which peaked at hatching, was higher for embryos incubated at 30 °C than at 27 °C. Rates of oxygen consumption (nl h^-1 individual^-1) at hatching were similar to those for other temperate and tropical species. Rates of oxygen consumption by yolk-sac larvae were highly variable, and these data suggest that larval oxygen consumption prior to yolk-sac absorption may not be significantly influenced by temperature. Rates of yolk depletion were higher for larvae at the higher temperature. After an initial rapid increase in length, length of larvae at 30 °C decreased with age. Egg size, egg weight, and maximum notochord length of larvae differed significantly between spawns. Age-specific oxygen consumption rates by the embryos varied between spawns, but regressions describing oxygen consumption as a function of age did not differ significantly. The initiation and completion of eye pigmentation were used as developmental markers to calculate the amount of yolk remaining for larvae at the different temperatures. Larvae maintained at 30 °C completed eye pigmentation approximately 3 h sooner than those maintained at 27 °C, but had less endogenous reserves. This finding indicates a trade-off between rapid development and efficient utilization of the endogenous reserves. The completion of eye pigmentation in larvae incubated at the higher temperature occurred at midnight and, depending on the amount of time that the larvae have to initiate feeding prior to the point-of-no-return, the timing of completion of eye pigmentation could influence larval survival.     

A laboratory study of behavioral interactions of the Antarctic keystone sea star Odontaster validus with three sympatric predatory sea stars

The circumpolar sea star Odontaster validus is ubiquitous in the nearshore marine benthos of Antarctica. Despite its ecological importance, little is known of its behavioral interactions with other common sympatric sea stars. To examine these interactions we employed time-lapse video analyses conducted in a large laboratory tank (1.8 m diameter circular tank, 1,629 L). In each experimental trial, 34 adult O. validus were placed in a tight circular grouping on one side of the tank, and one adult individual of one of three common sympatric species of predatory sea star (Labidiaster annulatus, Diplasterias brandti, or Perknaster aurorae) was placed on the opposite side of the tank. Digital images of sea star movements were then captured at one min intervals over a 24 h period and aspects of sea star movements subsequently analyzed. Each 24 h treatment was replicated three times, as was a control treatment consisting only of O. validus. O. validus had significantly elevated levels of activity in the presence of P. aurorae when compared with the other two sea stars (potential chemically mediated response), and displayed a distinct “flight response” (change in direction and twofold to sixfold increase of speed) upon tactile contact with this species. Moreover, an “alarm response” was detected when individuals of O. validus that encountered a fleeing conspecific also fled the vicinity. In contrast, our results indicated that O. validus displays virtually no chemical or tactile behavioral responses to the large multi-armed L. annulatus and only weak tactile responses to D. brandti.     

Toxicity and transfer of metal oxide nanoparticles from microalgae to sea urchin larvae

Nanoparticles (NPs) contained in commercial products are released and enter into the aquatic ecosystem, posing serious possible risks to the environment and affecting the food chain. Therefore, investigating the potential toxicity of NPs on aquatic organisms has become an important issue. This study assessed the toxicity and trophic transfer of metal oxide NPs from marine microalgae (Cricosphaera elongata) to the larvae of the sea urchin Paracentrotus lividus. Larvae (24 h old) were fed on 2000 cell mL^?1 48 h of microalgae contaminated with 5 mg L^?1 of several metal oxide NPs (SiO₂, SnO₂, CeO₂, Fe₃O₄) for 15 days. Larval viability and development were monitored from the 4-arm stage to the 8-arm pluteus stage. A significant decrease in survival was observed in larvae fed with microalgae exposed to SiO₂ and CeO₂ NPs. Abnormal development, characterised by skeletal degeneration and altered rudiment growth, was observed in all larvae fed with contaminated NP algae. Our findings revealed that SiO₂ and CeO₂ NPs exerted a toxic effect in the trophic interaction analysed, by reducing sea urchin larval viability, and all metal oxide NPs induced toxicological effects. In conclusion, metal oxide NPs may enter the food chain and become bioavailable for marine organisms, affecting their development.