Abbreviated Pelagic Life of Chilean and New Zealand Oysters

Summary 1. In analysing the ecological conditions of an animal population we have above all to focus our attention upon the most sensitive stages within the life cycle of the animal, that is, the period of breeding and larval development. 2. Most animal populations on the sea bottom maintain the qualitatively composition of the species composing them, over long periods of time, though the individual species use quite different modes of reproduction and development. This shows that species producing a large number of eggs have a larger wastage of eggs and larvae than those with only a few eggs. The wastage of eggs in the sea is much larger than on the land and in fresh water. 3. In the invertebrate populations on the level sea bottom, large fluctuations in numbers from year to year indicate species with a long pelagic larval life, while a more or less constant occurrence indicates species with a very short pelagic life or a non‐pelagic development. 4. In most marine invertebrates which shed their eggs and sperm freely in the water, either (a) the males are the first to spawn, thus stimulating the females to shed their eggs, or (b) an ‘epidemic spawning’ of a whole population takes place within a few hours. Both methods greatly favour the possibility of fertilization of the eggs spawned and show that the heavy wastage of eggs and larvae takes place after fertilization, during the free swimming pelagic life. 5. Embryos with a non‐pelagic development may originate (a) from large yolky eggs, in which case all the hatching young of the same species will be at the same stage of development, or (b) from small eggs which during their development feed on nurse eggs, when the individual embryos of the same species may vary enormously in size at the stage of hatching. 6. Three types of pelagic larvae are known: (a) Lecithotrophic larvae, originating from large yolky eggs spawned in small numbers by the individual mother animals; they are independent of the plankton as a source of food although growing during pelagic life, are absent from high arctic seas but constitute about 1 o % of the species with pelagic larvae in all other seas, (b) The planktotrophic larvae with a long pelagic life, originating from small eggs spawned in huge numbers by the individual mother animal; they feed from, and grow in, the plankton, constituting less than 5% of high arctic bottom invertebrates, 55–65% of the species in boreal seas, and 8 o ‐85 % of the tropical species, (c) The planktotrophic larvae with a short pelagic life having the same size and organization at the moment of hatching and at the moment of settling; these constitute about 5% of the species in all Recent seas. 7. To find out the factors which cause the enormous waste of eggs and larvae, we thus have to study those forms (constituting 7 o % of all species of bottom invertebrates in Recent seas) which have a long planktotrophic pelagic life, as only species reproducing in this way have really large numbers of eggs. 8. The food requirements of the planktotrophic pelagic larvae are much greater than those of the adult animals at the bottom. The adaptability of the larvae to poor food conditions seems, nevertheless, to be greater than hitherto believed. The significance of starvation seems mainly to be an indirect one: poor food conditions cause slow growth, prolong larval life, and give the enemies a longer interval of time to attack and eat the larvae. 9. At the temperatures to which they are normally exposed, northern as well as tropical larvae seem on an average to spend a similar time (about 3 weeks) in the plankton. The length of the pelagic life of the individual species may, however, vary significantly in nature. In the Sound (Denmark) the larvae are never exposed to temperatures outside the range which they are able to endure. The wastage caused by temperature, like that due to starvation, seems mainly to be an indirect one: low temperatures postpone growth and metamorphosis, and give the enemies a longer time to feed on the larvae. 1 o . When a larva feeding on a pure algal diet metamorphoses into a carnivorous bottom stage, a ‘physiological revolution’ occurs and a huge waste of larvae might be expected. Experiments have, however, shown that this is not the case. 11. Young pelagic larvae are photopositive and crowd near the surface; larvae about to metamorphose are photonegative. Larval polychaetes, echinoderms, and presumably also prosobranchs, may prolong their pelagic life for days or weeks until they find a suitable substratum. Forced towards the bottom by their photonegativity and transported by currents over wide bottom areas, testing the substratum at intervals, their chance of finding a suitable place for settling is much better than hitherto believed. 12. Continuous currents from the continental shelf towards the open ocean may transport larvae from the coast to the deep sea where they will perish. Such conditions may (for instance in the Gulf of Guinea) deeply influence the composition of the fauna, while in other areas (European western coast, southern California) they seem to be only of small significance. 13. The toll levied by enemies appears to be the most essential source of waste among the larvae. A list of such enemies, comprising other pelagic larvae, holoplank‐tonic animals and bottom animals, is given on p. 2 o . A medium‐sized Mytilus edulis , filtering 1–4 1. of water per hour, may retain and kill about 100,000 pelagic lamellibranch larvae in 24 hr. during the maximum breeding season in a Danish fjord. 14. Species reproducing in a vegetative way, by fission, laceration, budding, etc., might be expected to have good chances of competition in such areas where conditions for sexual reproduction are unfavourable. Nevertheless, they only supply a rather small percentage of the animal populations of all Recent seas, probably because their intensity of reproduction is low and because they are unable to spread to new areas. Most forms reproducing in a vegetative way have sexual reproduction as well. 15. Pelagic development is nearly or totally suspended in the deep sea, and is restricted to the shelf faunas. In the arctic and antarctic seas pelagic development is nearly or totally suppressed, even in the shelf faunas, but starting from here the percentage of forms with pelagic larvae gradually increases as we pass into warmer water, reaching its summit on the tropic shelves. 16. In order to survive in high arctic areas a planktotrophic, pelagic larva has to complete its development from hatching to metamorphosis within I–I ½ months (i.e. the period during which phytoplankton production takes place) at a temperature below 2–4 o C. Most larvae, that is in 95% of the species, are unable to do so and have a non‐pelagic development, but if a pelagic larva is able to develop under these severe conditions the planktotrophic pelagic life seems to afford good opportunities even in the Arctic. Thus the 5 % of arctic invertebrates reproducing in this way comprise several of the species which quantitatively are most common within the area. 17. The antarctic shore fauna has poor conditions similar to those of the Arctic. The longest continuous periods of phytoplankton production are 2 and 3 weeks respectively, and pelagic larvae have, in order to survive, to complete their development within this short space of time at a temperature between 1 and 4 o C. Accordingly, non‐pelagic development is the rule, but most arctic species are able to support their non‐pelagic development by means of much smaller eggs than the antarctic species, where brood protection and viviparity is dominant. The antarctic fauna has apparently had a longer time to develop its tendency to abandon a pelagic life. The greater the size of the individual born, the smaller its relative food requirements and the better its chance of competing under poor food conditions. 18. The relatively few data on reproduction in deep sea invertebrates point to a non‐pelagic development. The larvae of such forms, in order to develop through a planktotrophic pelagic stage, would have to rise by the aid of their own locomotory organs through a water column 2000–4000 m. high or more (often with counteracting currents) to the food producing surface layer, and to cover the same distance when descending to metamorphose and settle. 19. The ecological features common to the deep sea, the arctic and the antarctic seas, which enable the same animals to live and to reproduce there, contribute to explain the ‘equatorial submergence’ of many arctic and antarctic coastal forms. 20. In the tropical coastal zones where the percentage of species with pelagic larvae reaches its maximum, the production of food for the larvae takes place much more continuously than in temperate and arctic seas, because light conditions enable the phytoplankton to assimilate all the year round. The tropical species of marine invertebrates breed (in contrast to temperate and arctic species) within such different seasons that their larval stock, taken as a whole, is more or less equally distributed in the plankton all the year round. This makes the competition in the plankton less keen. 21. The fact that a mode of reproduction and development, well fit for an arctic area, is unfit in a tem

Ocean acidification is expected to decrease calcification rates of bivalves. Nevertheless, in many coastal areas high pCO2 variability is encountered already today. Kiel Fjord (Western Baltic Sea) is a brackish (12-20gkg(-1) ) and CO2 enriched habitat, but the blue mussel Mytilus edulis dominates the benthic community. In a coupled field and laboratory study we examined the annual pCO2 variability in this habitat and the combined effects of elevated pCO2 and food availability on juvenile M.edulis growth and calcification. In the laboratory experiment, mussel growth and calcification were found to chiefly depend on food supply, with only minor impacts of pCO2 up to 3350μatm. Kiel Fjord was characterized by strong seasonal pCO2 variability. During summer, maximal pCO2 values of 2500μatm were observed at the surface and >3000μatm at the bottom. However, the field growth experiment revealed seven times higher growth and calcification rates of M.edulis at a high pCO2 inner fjord field station (mean pCO2 ca. 1000μatm) in comparison to a low pCO2 outer fjord station (ca. 600μatm). In addition, mussels were able to out-compete the barnacle Amphibalanus improvisus at the high pCO2 site. High mussel productivity at the inner fjord site was enabled by higher particulate organic carbon concentrations. Kiel Fjord is highly impacted by eutrophication, which causes bottom water hypoxia and consequently high seawater pCO2 . At the same time, elevated nutrient concentrations increase the energy availability for filter feeding organisms such as mussels. Thus, M.edulis can dominate over a seemingly more acidification resistant species such as A.improvisus. We conclude that benthic stages of M.edulis tolerate high ambient pCO2 when food supply is abundant and that important habitat characteristics such as species interactions and energy availability need to be considered to predict species vulnerability to ocean acidification.

Understanding when small- or large-bodied cladocerans dominate zooplankton communities has received considerable debate over the past 50 years. While a large body of research has proposed that large-bodied species are superior competitors over small-bodied species, other studies have shown that small-bodied species can dominate at least under some environmental conditions. We tested the hypothesis that dominance by small- and large-bodied cladocerans varied in response to the coupled effects of food supply and temperature. Laboratory experiments with poly- and monocultures of small- and large-bodied cladocerans were performed at three temperatures (16°C, 22°C and 27°C) and with varying amounts of food supply. The results of the experiments showed that the small-bodied species (Ceriodaphnia quadrangula) dominated at low food supply and higher temperature, while the large-bodied species (Daphnia magna and Daphnia pulex) in contrast dominated at lower temperature and higher food supply. Furthermore, although there were variations in the relative biomass of the small- and large-bodied cladocerans in the polycultures, C. quandrangula replaced the two larger Daphnia species when they declined in biomass at low food supply. Species replacement in response to temperature and food supply helped to maintain the relatively constant level of total cladoceran biomass in the polycultures which was the most pronounced at the intermediate temperature. We suggest that the observed changes in dominance were similar to facilitative replacement rather than competitive exclusion. Physiological processes such as clearance rates can help to promote the succession of large- and small- bodied populations within a community along gradients of temperature and food availability.

The limiting effects of food and water on juvenile growth rates in the lizard Anolis aeneus were investigated in the field (Grenada, West Indies) and laboratory. Growth rates of lizards in the field were unrelated to their snout—vent lengths, but both prey biomass and rainfall had significant effects on juvenile growth rates. Laboratory experiments indicated that water had a primary limiting effect on growth; even when food supplies were superabundant, growth rates were low when drinking water was curtailed. Laboratory and field experiments suggest that limited water availability reduces growth rates for most (67%) of the dry season, whereas food levels are sufficiently low to limit growth during the weeks of the dry season when rainfall is sufficient for growth. During the wet season there is no evidence of water scarcity, food levels are high and average growth rates are 85% of the maximal rates observed under optimal conditions in the laboratory.

The distribution and density of every species of animal is at least loosely controlled by the distribution and abundance of its food. Particular attention has been paid recently to the distribution of salmonids as affected by selection of the site of the fish's feeding territory (Chapman & Bjornn 1969) and to their numbers as affected by varying abundance of food in different streams (Egglishaw 1967). Evidence that food supply does more than permit or prevent a population of salmonids from inhabiting a stream is as yet equivocal. Mason & Chapman (1965) found that the biomass and numbers ofjuvenile coho salmon (Oncorhynchus kisutch Walbaum) remaining in two stream channels from which they could emigrate were greater in the channel which had a greater food supply. However, since there was no replicate in which the varying rations were switched between channels, the possibility remained that the channel with the greater food supply retained more fish because of a greater number of hiding places, better cover, etc. In comparing two streams, one of which had three times as much food as the other, Egglishaw (1967) found that there were fewer trout in his food-poor stream, but more salmon, so that the total density of salmonids differed little (about 0 45 fish/m2 in the poor compared to 0 55 fish/m2 in the rich stream). Biomass differed even less. The streams were different in other respects besides food, however, which, in this case, may have masked the effect of food supply on density. Le Cren (1965) suggests that while a population of fish may be limited by food in the long run, in some instances other regulatory mechanisms usually reduce the importance of food supply as a regulatory factor. Effects offood supply on behaviour, in contrast to those on population density, have been reasonably well defined. In laboratory experiments with young salmon (Salmo salar L.), provision of food in two daily feedings was followed shortly afterwards by an increase in aggression which subsided gradually 30 min later (Keenleyside & Yamamoto 1962). Symons (1968) found when aggression was measured after immediate effects of feeding had waned, that fish deprived of food for 18-66 h were more aggressive than those receiving an abundance of food. Together these results indicate that, in those natural habitats having a continuous abundant supply of food, young salmon are probably less aggressive than in habitats where they are constantly hungry and meals are sporadic. Chapman (1962) has postulated that aggression of some territorial fish may cause the emigration of others with inferior fighting ability. Presumably an increase in aggression would speed this emigration process. Symons (1968) also suggested that the increase in aggression associated with food-deprivation might, in a natural environment, result in an

Laboratory experiments were used to determine effects of long‐ and short‐term food limitation on birth, growth, and death rates in Centropages typicus (Copepoda, Calanoida), a species previously reported to be sensitive to patchy food resources. Life‐history parameters were measured in cohorts from hatching to senescence in a range of constant food treatments (0.2–7 µg Chl a liter−1) and in two pulsed treatments that cycled between 0.5 and 2.0 µg Chl a liter−1 at periods of ~0.5 and 1.0 d. A flow‐through culture system minimized biochemical and grazing‐induced changes in food supply and allowed automated measurement of food levels (fluorescence). Particulate carbon, nitrogen, lipid, carbohydrate, and protein were measured also. Results show that even the “food‐sensitive” copepod, C. typicus, can integrate daily fluctuations in food supply at amplitudes comparable to patchiness levels observed in the field. This finding has important implications for field and laboratory studies that relate zooplankton growth and fertility to ambient food supply. Additional new findings include exponential growth in body length, sustained high fertility with age, ingestion of large algal and animal prey, and low contribution of carnivory to the diet. Comparisons with field data suggest that C. typicus is restricted to shelf regions due to food limitation, but that on the shelf it is a major contributor to total copepod production in the fall.

Our goal was to design a bench experiment tailored to the environment of advanced high school biology, college freshman biology, and nonmajor labs. To accomplish this goal, we developed a scientific protocol for isolation of apicomplexan cysts from store-bought meat by adapting existing protocols (Cornelissen et al., 1981 ; Blewett et al., 1983 ; Dubey, 1992 , 1998 ; Omata et al., 1997 ; Garcia et al., 2006 ). The majority of buffers used were common chemicals found in many introductory biology laboratories, and the protocol is simple enough for a freshman to use. What we found to be most challenging was modifying the experiment to fit time constraints imposed by a typical high school schedule. This experiment takes ∼3 h. We found that the lab could be split up into 4 d for high school and 2 d for college. The teacher should make some initial preparations (i.e., making buffers and solutions) to shorten the lab period. We suggest that students split up into at least five groups of six students each. The students should be encouraged to compare and share their results. We recommend that the students spend time researching T. gondii statistics on the CDC website (www.cdc.gov) and reading newspapers to identify related topics, such as food recalls as a result of tainted product. Specifically, we suggest creating a quiz to test their knowledge of food safety and administering it before and after the exercise. We would also suggest including a follow-up discussion section investigating student response to this assignment. For example, how has completing this laboratory exercise affected their opinions about food, science, and laboratory experiments? We have listed several very useful websites in Materials and Methods. These sites are extremely helpful in providing pictures for identification purposes and background information on the parasites themselves. In addition to T. gondii, numerous other organisms (i.e., multiple types of nematodes and tapeworms) can be observed by sampling the bottom of the meat slurry instead of the supernatant. Although we had multiple years of experience at the lab bench, we found that we were surprised by the abundance and diversity of organisms in meat. It provoked us to ask the question: “Just who is eating who?” Although many of these pathogens are species specific and thus not a health threat to human (i.e., N. caninum), some of the organisms, such as T. gondii, are human pathogens. We realized that it reinvigorated our interest in the topic, and we were fascinated by the images in the microscope. Some of us could not eat meat for a week after doing the experiment. This realization validated for us the idea that science at the bench as opposed to simple book learning is essential for biology and nonmajors students alike. It drives home the point that well-prepared foods (washing and cooking) are a cornerstone of food safety. Carrying out this experiment familiarizes students with the microscope and more advanced isolation techniques such as the use of Percoll. It introduces some concepts about parasitology and food safety. It can be incorporated into a lesson plan covering infectious agents or health. It meets Indiana secondary school standards for advanced life sciences (standard 2: health, safety, and microbiology of food), and human anatomy and physiology (standard 10: immune mechanisms). Completion of this exercise also meets national educational standards for secondary school in the topics science as inquiry, interdependence of organisms, personal and community health, and science as a human endeavor (National Committee on Science Education Standards and Assessment, 1996 ). Upon completion of this exercise, the following positive outcomes are expected for students: 1) gain confidence about ability to carry out labwork and stimulate curiosity about pursuing other science classes, 2) obtain insight about health and safety of food and provide students the chance to critically evaluate articles in the newspaper regarding food recalls, and 3) change student behavior in terms of food choice, food preparation behavior, or both. In sum, the ultimate outcome of this exercise is for students to apply the procedure to investigate a real and meaningful problem and, as a result, to describe organisms found in the meat supply, the hazards they pose, and procedures for avoiding the hazard. Because there is a compelling repulsion factor, there is a strong possibility that students would also change their behavior (either food choices or food preparation behavior). For teachers, it represents an innovative teaching strategy that provides a relatively inexpensive laboratory experience with direct student involvement that meets several national education standards.

Juvenile (12–152 g) shortfinned eels Anguilla australis and longfinned eels A. dieffenbachia caught in New Zealand streams were fed squid mantle Nototodarus spp. 4 days per week in laboratory experiments. A linear multiple regression equation showed the amount of food eaten (0–2·7% w day−1) explained 77·7% of the variation in specific growth rates (–0·60 to +1·07% w day−1) among individual eels, while previous growth rates, water temperature (10·0–20·6°C), and eel weight (12–152 g) explained a further 5·6, 1·4 and 0·8%, respectively. Growth in length ranged from –0·3 to +0·9 mm day−1. Eels which were starved and then given high rations grew substantially faster than expected. Once growth rates were adjusted for differences in ration and other factors, there were no significant differences in growth rates between species or individual fish. Growth of shortfinned eels fed maximum rations of commercial eel food depended on fish size and water temperatures and ceased below 9·0°C. Growth rates in the wild were substantially less than the maximum possible, after seasonal changes in water temperatures were taken into account, indicating that food supplies and not low water temperatures were controlling growth rates in the wild.

Juvenile (12–152 g) shortfinned eelsAnguilla australisand longfinned eelsA. dieffenbachiacaught in New Zealand streams were fed squid mantleNototodarusspp. 4 days per week in laboratory experiments. A linear multiple regression equation showed the amount of food eaten (0–2·7% w day−1) explained 77·7% of the variation in specific growth rates (–0·60 to +1·07% w day−1) among individual eels, while previous growth rates, water temperature (10·0–20·6°C), and eel weight (12–152 g) explained a further 5·6, 1·4 and 0·8%, respectively. Growth in length ranged from –0·3 to +0·9 mm day−1. Eels which were starved and then given high rations grew substantially faster than expected. Once growth rates were adjusted for differences in ration and other factors, there were no significant differences in growth rates between species or individual fish. Growth of shortfinned eels fed maximum rations of commercial eel food depended on fish size and water temperatures and ceased below 9·0°C. Growth rates in the wild were substantially less than the maximum possible, after seasonal changes in water temperatures were taken into account, indicating that food supplies and not low water temperatures were controlling growth rates in the wild.

It has sometimes been said that it is useless to try to prevent wars since man has an ineradicable combative instinct. The term instinct is very ambiguous in its application to humans, and it may be interesting to see what occurs amongst the insects, many of whose species show the highest development of instinctive behaviour.Many insect species are predatory, but if they depend on other distinct species, the relation is analogous to hunting or to a crude form of agriculture. Aggressive behaviour to be comparable with war must concern the different members of one species. There are many laboratory experiments which illustrate the effects of competition when a population begins to exceed the capacity of its food supply. In Flour beetles, for instance, the adult beetles and the larvae eat any egg or pupae which they happen to meet in their ceaseless burrowing through the flour. There is thus a fixed population density at which eggs are eaten as fast as they are laid. In Grain weevils, the effect of crowding is to reduce the rate at which eggs are laid by the females who appear to suffer from overstimulation when crowded. Other effects, usually harmful, may be produced by the accumulation of the products of respiration or of digestion. Finally, if the food supply is too small, there will be death from starvation. If, for instance, too many blowfly eggs are added to a piece of meat, the flies produced will either be small, weak, and infertile or, if the excess has been too great, the larvae may all starve when half grown. Thus, a piece of meat which could have produced 100 normal flies may produce none at all if a tenfold excess of eggs is laid on it.

Cutting edge technologies to end food waste

Trade-off between increased survival and reduced growth for blue mussels living on Pacific oyster reefs

Abstract.— Three experiments investigating larval stocking densities of summer flounder from hatch to metamorphosis, Paralichthvs dentalus, were conducted at laboratory‐scale (75‐L aquaria) and at commercial scale (1,000‐L tanks). Experiments 1 and 2 at commercial scale tested the densities of 10 and 60 larvae/L, and 10, 20, and 30/L, respectively. The laboratory scale experiment tested the densities of 10, 20, 30, and 40 larvae/L. Experiments were carried out in two separate filtered, flow‐through seawater systems at URI Narragansett Bay Campus (laboratory‐scale), and at GreatBay Aquafarms, Inc. (commercial‐scale). At both locations, the larvae were raised in a “greenwater” culture environment, and fed rotifers and brine shrimp nauplii according to feeding regimes established for each location. Water temperature was maintained at 21C (± 2) and 19C (± 1) for the duration of laboratory and commercial experiments, respectively. Experiments 1 and 2 at the commercial location were terminated at 42 and 37 d post hatch (dph), respectively, and the laboratory experiment lasted 34 DPH. Larvae initially stocked at 10/L grew to an average length of 14.3 and 14.4 mm, and were significantly larger (P < 0.05) than those stocked at 30/L (13.1 mm) and 60/L (11.7 mm) in commercial scale experiments I and 2, respectively. At laboratory scale, no significant differences in length were detected, although mean total length tended to decrease with increasing stocking density (average length of 14.2, 13.3, 12.7, and 12.7 mm for treatments of 10, 20, 30, and 40/L, respectively). Final survival percentage was not affected by stocking density in either commercial experiment, and was 61 and 40% for treatments of 10 and 60/L in Experiment 1, respectively, and 62, 59, and 56% for Experiment 2, respectively. Similarly, there was no significant difference in final survival percentage among treatments in the laboratory experiment, which averaged 59, 55, 56, and 37% for treatments of 10, 20, 30, and 40L. respectively. Since larval length was not different between the intermediate densities (20 and 30 Iarvae/L), and because high‐density rearing can produce a much greater numerical yield per tank, we recommend a density of 30 larvaen as an optimal stocking density for the hatchery production of summer flounder.

Livewell conditions during competitive angling events are thought to affect fish mortality. We examined the effects of livewell additives on initial and delayed mortality of largemouth bass Micropterus salmoides. We applied three treatments (salt, ice, or salt and ice) to livewells during tournaments conducted on lakes in Illinois, United States, as well as in laboratory and pond experiments designed to examine the effects of fish size and ambient water temperature on mortality. Fish were collected after tournament weigh-in procedures were completed and monitored for delayed mortality every 24 h for 5 d. Initial mortality did not differ among livewell additives during these field experiments. Although delayed mortality was high (35%), it was not significantly different among livewells that contained salt (56%), ice (48%), ice and salt (40%), and controls (30%). Additives administered during the laboratory experiments, at cool water temperatures, resulted in significantly lower delayed mortalities than those observed during the field experiments when ambient water temperatures were warmer. Initial and delayed mortality did not differ among livewell additives during the laboratory experiments. Larger fish in field experiments had significantly greater delayed mortality than smaller fish in the pond experiments even though initial and delayed mortality did not differ among livewell additives. Our results suggest that fish size and ambient water temperature have a greater influence on delayed mortality observed during competitive angling events than the specific livewell additives studied here.

In situ and laboratory growth by a population of blue mussel larvae ( Mytilus edulis L.) from a Danish embayment, Knebel Vig