R. K. O'Dor

Influence of dietary lipid sources on fecundity, egg hatchability and fatty acid composition of Chinese prawn (Penaeus chinensis) broodstock

The effect of feeding four semi-purified diets containing different lipid sources (anchovy oil, linseed oil, corn oil and pork lard) on fecundity, egg hatchability and egg and spent gonadal tissue fatty acid composition of Chinese prawn (Penaeus chinensis) broodstock was compared with a fresh clam diet in a 60-day feeding trial. Broodstock prawn fed the diet containing pork lard showed poor fecundity and low egg hatchability. Broodstock fed the diets containing linseed or corn oil showed improved egg production (P<0.05); however, no significant improvement in hatchability was observed. When broodstock were fed the diet containing anchovy oil, both fecundity and egg hatchability were significantly improved (P<0.01). Eggs from broodstock fed anchovy oil as sole dietary lipid had a higher n−3 highly unsaturated fatty acid (HUFA) content (27.6%) compared with those of prawn fed diets containing linseed oil (19.5%), corn oil (14.0%) or pork lard (12.8%). Good correlations between the 20:5n−3 content of the egg lipid and fecundity and between 22:6n−3 content and hatchability were observed. The results suggest that each of these n−3 HUFAs may play different and specific roles in crustacean reproduction and that either or both must be included in the broodstock diet.

Ultrasonic telemetry, tracking and automated monitoring technology for sharks

Sharks were among the first marine animals to carry telemetry systems because of their size and the need to understand their interactions with humans. Modern telemetry systems can gather many kinds of data (limited only by imagination, funding and sensor types), indicating which animals are near telemetry receivers and what they are doing. Receivers now range from simple autonomous detector units for deployment in mid-water in large-scale grids, to sophisticated automated benthic recorders, to triangulating radio-linked buoy systems (RAP), to ship-borne transponders. In addition, archival tags can now gather and store data even while the shark is away, to be downloaded later. Older types had to be recovered, but popup tags release from sharks automatically, surface and transfer data to satellites, while CHAT tags download whenever queried by a nearby transponding acoustic receiver. Sophisticated animal-borne tags dramatically increase the information gathered about sharks and their environment. The examples provided show the parallel progression of shark biology and acoustic biotelemetry illustrating that telemetry systems are tools for gathering data, which can often be honed to facilitate biological experiments. Future visions include sensors that directly measure shark swimming power and cardiac output, compressing the data so that it can be delivered to RAP systems tracking multiple animals with meter resolution in near real time. CHAT tags as small as 22 mm diameter should be able to return similar data from trips of hundreds of kilometers. Continued communication between biologists and engineers is essential to develop these technologies.

Nutrient absorption, storage and remobilization in octopus vulgaris

Average absorption and conversion to 14CO2for free leucine included in a meal were 96% and 30% after 24 h. The values for glucose were 98% and 48% and for palmitate 46% and 12.5%. Muscle was the major repository of leucine (38% of the total ingested) and glucose (44%), but the digestive gland contained most of the palmitate (20%). During normal feeding 14CO2 production from octopuses given leucine dropped to low stable levels after only 2 days, those given glucose required 4 to 5, but palmitate apparently did not enter a stable reserve. Fasting increased the release of 14CO2 from octopuses given palmitate and leucine, but glucose animals showed little change. A 5‐fold increase in 14CO2 production during forced exercise after fasting by octopuses given glucose may indicate increased carbohydrate catabolism. Reduced 14CO2production in exercise after other substrates is consistent with this, suggesting muscle carbohydrate reserves may be exclusively for locomotion. A comparison of nutrient uptake, catabolism...

Essential fatty acid requirement of the Chinese prawn, Penaeus chinensis

The aim of this study was to determine the essential fatty acid (EFA) requirement of one of the most important commercially cultured crustacean species in the world, Penaeus chinensis. Groups of 16 individually housed juvenile Chinese prawn were fed for 60 days with 12 semi-purified experimental diets. These diets were based on the crab-protein-concentrate Standard Reference Diet and contained either 5% of a mixture of tripalmitin (16:0) and triolein (18:1n−9) (EFA deficient control diet), or 4% of this mixture and a 1% supplement of various purified polyunsaturated fatty acids (PUFA) or highly unsaturated fatty acids (HUFA). Prawns fed the EFA-deficient control diet suffered 100% mortality. The prawns fed a diet containing 1% trilinolenin (18:3n−3) had higher growth and longer survival than that of animals fed the diet containing 1% trilinolein (18:2n−6). Feeding a diet containing a mixture 0.5% of each of these lipids resulted in a greater growth rate and a 0.25:0.75 mixture of trilinolein and trilinolenin produced a greater survival than any other mixture or either purified fatty acid supplement alone. When the 18-carbon polyunsaturated fatty acid supplement was replaced with 1% of the triglyceride of arachidonic acid in the diet fed to prawns, however, the growth was about equal to that of prawns receiving 1% 18:3n−3 and survival was significantly higher than that of prawns fed any combination of 18:2n−6 or 18:3n−3 tested, while being less than that of prawns fed a diet containing 1% of the triglyceride of docosahexaenoic acid (DHA, 22:6n−3). The prawns fed the EFA-deficient control diet or any of the diets with 18:2n−6 or 18:3n−3 supplemented individually had extremely low body lipid levels. Mixtures of these two fatty acids or any combination of the n−6 or n−3 HUFA resulted in more normal body lipid levels, suggesting that both n−3 and n−6 type fatty acids might be required by the Chinese prawn. The fatty acid composition of the total body lipid reflected that of the experimental diets. Though 18:2n−6 and 18:3n−3 were not apparently desaturated and elongated to the physiologically important EFA members of the respective n−6 and n−3 series of fatty acids (20:4n−6, 20:5n−3 and 22:6n−3), there was evidence for elongation of these acids to 20:2n−6 and 20:3n−3. The results indicate that the essential fatty acid values of the fatty acids in the diet of the Chinese prawn increased in the following order 18:2n−6 < 18:3n−3 < 20:4n−6 < 22:6n−3.

Diurnal changes in activity and metabolic rate in octopus vulgaris

The activity of Octopus vulgaris was monitored continuously in the laboratory. Starving animals are active mainly at night, with an activity peak at about 23.00 hrs. Feeding in the evening preserves this pattern, while feeding at 10.00 hrs or ad lib disrupts but does not reverse it. Oxygen consumption rises and falls with activity. For a 350g animal, the Standard Metabolic rate is about 53 ml O2 Kg−1 h−1 Routine M.R. 72 ml O2 Kg−1 h−1; feeding and movement both produce large increases in oxygen consumption. Oxygen uptake varies as Weight 0.7 and shows a Q10 of 1.77. These findings are discussed in relation to previous reports of the oxygen consumption of cephalopods, to the diurnal pattern of activity shown by O. vulgaris in the sea, and in relation to the results of training experiments.

Applications and performance of Radio-Acoustic Positioning and Telemetry (RAPT) systems

RAPT was developed to use systems of semi-autonomous buoys with hydrophones and radio transmitters to continuously monitor the positions and performance of multiple objects, animals and/or people tagged with miniature acoustic transmitters under water. Buoys communicate signal arrival times to shore, ship or aircraft based computers which triangulate positions in three dimensions and decode telemetered information such as heart rate, respiration rate, temperature, salinity and light encoded in pulse intervals. It is the only way of tracking with high-resolution (meters) at intermediate ranges (10’s-1000’s of meters) in seawater and the most accurate in freshwater. The technique is powerful and flexible with wide application, but is constrained by tradeoffs between electrical power and signal accuracy under extreme conditions. Technological solutions to some of these constraints are possible, but optimization of information gathering, in many cases, simply requires more experience and can be achieved by software, information sharing and a cadre of trained personnel.

Feeding and metabolic rate in octopus

Feeding raises the metabolic rate of Octopus vulgaris. The increase in oxygen consumption has two distinct components. There is a progressive increase in routine uptake over the first three or four days of feeding following a period of starvation, which can end by doubling or trebling the standard metabolic rate; the effect is most marked in small animals. Superimposed on this rise in baseline there is a short‐term rise and fall, with a timescale of 6 hours or so, following each meal. The short‐term cost of assimilating crab flesh is in the region of 9 ml O2 g−1. Taken togeather and compared with the standard rate, and the cost of locomotion in search of prey, the short and long‐term increases that follow feeding mean that feeding state is overwhelmingly the most important determinant of the daily energy requirement of Octopus.

Costs of Locomotion and Vertic Dynamics of Cephalopods and Fish

The worlds oceans are three‐dimensional habitats that support high diversity and biomass. Because the densities of most of the constituents of life are greater than that of seawater, planktonic and pelagic organisms had to evolve a host of mechanisms to occupy the third dimension. Some microscopic organisms survive at the surface by dividing rapidly in vertically well mixed zones, but most organisms, small and large, have antisinking strategies and structures that maintain vertical position and mobility. All of these mechanisms have energetic costs, ranging from the “foregone metabolic benefits” and increased drag of storing high‐energy, low‐density lipids to direct energy consumption for dynamic lift. Defining the niches in the mesopelagic zone, understanding evolution, and applying such ecological concepts as optimal foraging require good estimates of these costs. The extreme cases above are reasonably well quantified in fishes, but the energetic costs of dynamic physiological mechanisms like swim bladders are not; nor are the costs of maintaining vertical position for the chief invertebrate competitors, the cephalopods. This article evaluates a matrix of buoyancy mechanisms in different circumstances, including vacuum systems and ammonium storage, based on new data on the metabolic cost of creating buoyancy in Sepia officinalis.

Oxygen consumption in movement by octopus

Octopuses were made to walk in a closed annular respirometer, and the oxygen cost of locomotion determined. It is 253 ± 8 ml O2 Kg−1 Km−1 for an octopus of 500 g at 22°C travelling at 0.34 Km h−1, about three times the cost of swimming for a fish of similar size and one third the cost of tetrapod walking on land. Maximum oxygen uptake was about 2.4 X the routine uptake. The animal is able to sustain a small oxygen debt (of the order of 19 ml Kg−1) much of which would appear to be accumulated during the first 5 or 10 minutes of enforced loeomotion. The cost of walking by octopus is compared with the cost of jet‐propelled swimming in squid.

A review of ammonia‐mediated buoyancy in squids (cephalopoda: Teuthoidea)

Some deep water squids are known to achieve neutral buoyancy by storing ammonium in their body tissues. The Cranchiidae use a unique coelomic cavity to store ammoniacal fluid; in 15 other families, ammonium appears to be sequestered in either vacuoles in the active body tissues or in a gelatinous outer layer. The hypothesis that these squids form a single lineage is here reconsidered through reviews of morphological characters that could support this hypothesis and physiological mechanisms that could contribute to the repeated evolution of ammonium storage. No readily apparent character identifies all ammoniacal squids as belonging to a single lineage, although 5 families of tissue ammoniacal squids appear to be monophyletic. If the elaborate funnel locking apparatus of this group arose within the clade, it is not homologous with that in other taxa, refuting a basis on which close relationships were suggested for ammoniacal squids. Given the limited data available, we question whether some squids consider...