Vertical distribution and diurnal migration of some Cyclopoida (Copepoda) in the tropical region of the Pacific Ocean

The material was collected in the western equatorial part of the Pacific Ocean at a 24 h station on December 21 to 23, 1968. Collections were made by means of 2 Juday nets from 2 winches simultaneously. A series of hauls was made at 2 h intervals. The vertical distribution of 17 Cyclopoida species, belonging to 3 families (Oithonidae, Oncaeidae and Corycaeidae) was studied. From 0 to 300 m, the absolute number of Cyclopoida individuals was practically constant throughout the 24 h period. The bulk of the species performed no diurnal vertical migration, or migrated with low intensity in the usual way (i.e. moved upward at night and downward during the day). Only 2 Oncaeidae species performed significant diuranl vertical migration. No reversed migration in Cyclopoida was discovered. To characterize the vertical distribution of Cyclopoida, the distribution of the cores of populations (abundancies between 25 and 75%) was examined. During the 24 h period, the cores of populations of various Cyclopoida species were found at different depths; this steplike distribution was not disturbed in migrating species. The cores of populations differed both with habitat depth and time of ascent of the migrating species to the surface layer. This peculiarity, probably, tends to lessen the intensity of food competition between Cyclopoida species with similar nutritional habits.     

Uptake and loss of radioactive cadmium by the sea-skater Halobates robustus (Heteroptera: Gerridae)

Sea-skaters, Halobates robustus Barber, caught around the Galápagos Islands, were exposed over a period of 3 days to radioactive cadmium dissolved in seawater. Although ^115mCd (metastable ¹¹⁵Cd) was accumulated by the insects, they did not concentrate it above the seawater level. The experiments clearly showed that cadmium is taken up into the body, not merely adsorbed onto surfaces. The uptake of Cd followed a biphasic time course. When sea-skaters labelled in this way were transferred back into unlabelled seawater, the rate of loss of Cd was likewise biphasic. During uptake and loss, the biological half-life times for the first compartments were almost identical (0.64 and 0.79 h), indicating that the same compartment might be involved. On the other hand, the biological half-life times for the second compartments were different (1.7 days during uptake, 19.5 days during loss), indicating that the site or chemical form of bound Cd in the sea-skater had changed. For an adult female, weighing about 8.5 mg wet weight, the drinking rate of seawater was estimated at 2.5 l day^-1, equivalent to 29% body weight.     

Sperm swimming speed and energetics vary with sperm competition risk in bluegill (<Emphasis Type="Italic">Lepomis macrochirus</Emphasis>)

Under sperm competition, a males fertilization success depends largely on the ejaculate characteristics of competing males. Theoretical models predict that, in external fertilizers, increased risk of sperm competition should result in selection for increased sperm swimming speed. To test this prediction, we studied the behavior of sperm from parental and sneaker male bluegill (Lepomis macrochirus), a fish species characterized by high levels of cuckoldry due to alternative reproductive tactics of males (parentals and cuckolders). Because cuckolders (sneakers and satellites) always spawn in the presence of a parental male, but the reverse is not true, cuckolders experience the greater risk of sperm competition. We show here that the spermatozoa of sneakers have faster initial swimming speeds but shorter periods of motility than the sperm of parental males. Moreover, we show that sperm swimming speeds shortly after activation (when most fertilization occurs) are correlated with starting ATP levels in spermatozoa, suggesting that sperm competition has selected for higher energetic capacity in the sperm of sneakers. Thus, the higher energetic capacity and initial swimming speed of sneaker sperm may explain why, despite having fewer sperm per ejaculate than parentals, sneakers fertilize more eggs than parental males when they compete to fertilize a clutch of eggs.Communicated by L.W. Simmons     

Energetics of underwater swimming in the great cormorant (Phalacrocorax carbo sinensis)

Resting metabolic rate (RMR), energy requirements and body core temperature were measured during underwater swimming in great cormorants (Phalacrocorax carbo sinensis) at the zoological garden in Neumünster, Germany, using gas respirometry and stomach temperature loggers. We used a 13 m long still water canal equipped with a respiration chamber at each end. Birds swam voluntarily in the canal at a mean speed of 1.51 ms^-1. Power input during underwater swimming averaged 31.4 W kg^-1. Minimal costs of transport of 19.1 J kg^-1 m^-1 were observed at a speed of 1.92 m s^-1. Body core temperature was stable in all birds within the first 60 min spent in the canal. After that, body temperature dropped at a rate of 0.14°C min^-1 until the birds voluntarily left the water. Our data indicate that great cormorants spend 2.7 times more energy than Adélie penguins (Pygoscelis adeliae) during underwater swimming. This can be essentially attributed to their poor insulation, their mode of locomotion underwater and differences in streamlining. RMR on land was related to body mass via VO₂=0.691 M^0.755 (where VO₂ is O₂-consumption in litre h^-1 and M is body mass in kg). In order to quantify the effects of external devices on energy consumption during underwater swimming, we tested a dummy data logger attached to the back of the cormorants as well as a ring on the leg. The ring had no apparent influence on the swimming energetics of the cormorants. In birds equipped with dummy loggers, swimming speed was not significantly influenced, but both power input and costs of transport increased by a mean of 19% for swimming speeds between 1.4 and 1.8 m s^-1.     

Energy expenditure of swimming bottlenose dolphins (Tursiops truncatus)

The aim of our investigations was to determine, via oxygen and carbon-dioxide respirometry, how much energy dolphins (Tursiops truncatus) require when swimming at different speeds. Experiments were conducted on two female bottlenose dolphins (mean mass 162 kg) in the dolphinarium in Nuremberg Zoo, Germany, between March and August 1997. Animals were stationed in a respiration chamber for a minimum of 90 s after performing a variety of activities. We measured respiration frequency and oxygen requirements during (1) resting, (2) swimming at various velocities and (3) leaping to various heights. Resting metabolic rate of our bottlenose dolphins (2.15 W kg⁻¹) was comparable to previously published data. Metabolic rate in swimming dolphins increased to 2.47 W kg⁻¹ at 2 m s⁻¹, while leaps to 2.2 and 3 m height required a power input of 3.5 and 4 W kg⁻¹, respectively. Transport costs of swimming dolphins were lowest (1.16 J kg⁻¹ m⁻¹, corresponding to 0.12 J N⁻¹ m⁻¹) at a speed of 2.5 m s⁻¹, yielding an optimal range speed of between 1.9 and 3.2 m s⁻¹ (corresponding to minimum cost of transport ±10%). Breathing rates during all experiments correlated very well with oxygen consumption (r ² > 0.89) and could be used to derive metabolic rates in unencumbered dolphins at sea. Received: 18 December 1998 / Accepted: 27 April 1999     

Leptocephalus energetics: assembly of the energetics equation

The principles of energetics were used to examine the energetic requirements of leptocephali. Respiration and excretion rates and daily growth rates combined with proximate composition were used to examine the allocation of energy into each of the three main components of energetics: metabolism, excretion and growth. The daily energetic requirements for leptocephali, referred to as type 2 larvae based upon their unique developmental strategy, were compared to the requirements of non-leptocephalus larvae, known as type 1. Leptocephalus daily energetic requirements were also compared to the energy available from the leptocephalus' proposed food sources. The four species of eel larvae selected were all from the order Anguilliformes: Paraconger caudilimbatus (Poey), Ariosoma balearicum (Delaroche), Gymnothorax saxicola Jordan and Davis, and Ophichthus gomesii (Castelnau). The allocation of energy to each of the components of energetics as well as the total energetic requirements for the leptocephali proved to be very different from those of type 1 larvae. Metabolism received the majority, 60-92%, of the energy required per day. Growth and excretion were allocated 4-39% and <1-21%, respectively, of the total energy needed per day. Leptocephali required <50% of the energy needed by type 1 larvae of equal dry mass. The unique growth strategy used by leptocephali allows them to increase rapidly in size while allocating the majority of their energy, not to growth as in most larval fish, but to metabolism.     

Movements and swimming behaviour of white sharks (Carcharodon carcharias) in Australian waters

We used a combination of satellite telemetry, archival and conventional tags to show that white sharks made broad-scale movements consistent with mixing of the population across their entire Australasian range. The capture of one of these sharks in New Zealand, some 3,550 km from the point of tagging in South Australia, provides further confirmation that white sharks sometimes move into open ocean waters and cross deep ocean basins. However, most movements were confined to shelf waters, generally in areas of less than 100 m depth and in some cases into waters of less than 5 m depth. Sharks showed considerable plasticity in swimming patterns, which included many of the behaviours reported for other species. One of the archival-tagged sharks showed separate periods of distinct swimming behaviour as it moved into different habitats and travelled between them. The changes in swimming behaviour were abrupt and suggested rapid switching of hunting strategies for different prey types in these habitats. All tracked sharks showed both prolonged periods of directional swimming in coastal waters at swimming speeds of 2–3 km h⁻¹ as well as temporary residency in particular regions. Movements of tagged white sharks, together with data from shark control programs and bycatch records, suggest a seasonal movement northward along the east coast of Australia during the autumn–winter months and south in spring–early summer. The consistency of paths taken by white sharks in Australian waters suggests that they may follow common routes or “highways” in some areas. If so, identifying such areas may assist in reducing interactions with fishing operations and thus reduce bycatch.     

The effect of social interactions on calling energetics in the gray treefrog (Hyla versicolor)

Summary The vocal behavior of Hyla versicolor was studied in the field by means of behavioral observations and playback experiments, and these data were coupled with measurements of oxygen consumption in calling frogs to estimate the effect of social interactions on calling energetics. Male gray treefrogs have intense calls (median peak SPL=109 dB, fast RMS SPL=100 dB at 50 cm). At an air temperature of 23° C, males produced an average of 1,200–1,300 calls/h for 2–4 h per night. Calling rates and call durations differed among individuals, but were relatively constant for each male during periods of sustained calling. Males in dense choruses gave calls about twice as long as isolated males, but produced calls at about half the rate. Consequently, total calling effort and estimated aerobic costs were largely independent of chorus density. Playbacks of recorded calls to males in the field elicited increases in call duration and decreases in calling rate, regardless of the rate or duration of the stimulus. Males gave longer calls in response to long calls or to stimuli presented at high rates, but they did not precisely match either stimulus rate or duration. Calling effort and estimated oxygen consumption changed only slightly during stimulus playbacks. These results indicate that male-male competition elicits pro-found changes in the vocal behavior of calling males, but these changes have little effect on energy expenditure. We estimated that most calling males had metabolic rates of about 1.7–1.8 ml O₂/(g\h), or about 280 J/h for an average size (8.6 g) male at 20° C. Although changes in call duration and calling rate did not affect aerobic costs of calling, males producing long calls at slow rates called for fewer hours per night than males producing shorter calls at higher rates. This suggests that calling time may be limited by the rate at which muscle glycogen reserves are depleted.     

Circadian rhythm of swimming activity in juvenile pink salmon (Oncorhynchus gorbuscha)

The circadian rhythm of swimming activity and the role of the daily illumination cycle in the synchronization of this rhythm were studied in individual juvenile pink salmon. Sixty eight percent of all fish examined (n=38) were day-active when exposed to a 12 h L:12 h D cycle; the remaining fish were nocturnally active. One half of the fish tested under laboratory conditions of continuous, constant light intensity (LL) and constant temperature showed unambiguously endogenous activity rhythms with circadian periods for up to 10 d. The remaining fish were arrhythmic. Mean period length of the free-running activity rhythms for diurnal fish in LL shortened with constant light intensity increasing from 6 to 600 lx, as predicted by the circadian rule. In contrast, mean free-running period for nocturnal fish did not vary significantly with similarly increasing constant light intensity. Mean swimming speed (activity level) of both diurnal and nocturnal fish increased significantly with increasing light intensity. This is suggestive of a positive photokinetic response. When subjected to a phase-delayed LD cycle, the fish resynchronized their daily rhythms of activity with this new LD cycle after only one transient cycle in most instances. Hence, the timing of the daily activity rhythms appeared to occur through the direct masking action of the illumination cycle on activity, rather than through entrainment of an endogenous circadian system.     

Impact of ocean acidification in the metabolism and swimming behavior of the dolphinfish (Coryphaena hippurus) early larvae

Since the industrial revolution, [CO₂]_atm has increased from 280 μatm to levels now exceeding 380 μatm and is expected to rise to 730–1,020 μatm by the end of this century. The consequent changes in the ocean’s chemistry (e.g., lower pH and availability of the carbonate ions) are expected to pose particular problems for marine organisms, especially in the more vulnerable early life stages. The aim of this study was to investigate how the future predictions of ocean acidification may compromise the metabolism and swimming capabilities of the recently hatched larvae of the tropical dolphinfish (Coryphaena hippurus). Here, we show that the future environmental hypercapnia (ΔpH 0.5; 0.16 % CO₂, ~1,600 μatm) significantly (p < 0.05) reduced oxygen consumption rate up to 17 %. Moreover, the swimming duration and orientation frequency also decreased with increasing pCO₂ (50 and 62.5 %, respectively). We argue that these hypercapnia-driven metabolic and locomotory challenges may potentially influence recruitment, dispersal success, and the population dynamics of this circumtropical oceanic top predator.     

Role of protein in larval swimming and metamorphosis of Bugula neritina (Bryozoa: Cheilostomatida)

Larvae of the marine cheilostomatid bryozoan Bugula neritina (L.) were prevented from settling for 1, 4 and 8 h by mechanical agitation, following which settlement and metamorphosis success were examined. Settlement rates were significantly affected by swimming time, which decreased from 100% after 2 h to 93.7 ± 4.3% after 8 h. Similarly, metamorphosis to the feeding ancestrula was significantly impaired following a swimming time of 8 h, declining from 93.7 ± 4.3% after 1 h to 65.9 ± 7.0% after 8 h. The resultant colonies grew well for the first 3 wk, following which time, growth patterns became erratic. Growth rate was in all cases highly variable, and did not correlate with enforced swimming times. Larval protein composition was examined after 1, 4 and 8 h swimming time, and post-larval composition 1, 2, 5, 24 and 48 h after settlement using sodium-dodecyl-sulphate polyacrylamide-gel electrophoresis (SDS-PAGE). Individual protein content was measured using a densitometer. Larvae did not consume protein during swimming, however a protein measuring 170 kdaltons was consumed during metamorphosis. These results are discussed in the context of larval settlement and energetics. Received: 19 July 1998 / Accepted: 3 December 1998     

Circatidal swimming activity rhythm in a subtidal cumacean Dimorphostylis asiatica (Crustacea)

Dimorphostylis asiatica, a cumacean crustacea inhabiting the sublittoral line of the Seto Inland Sea, shows a rhythmic pattern of swimming activity coinciding with daily and tidal components in the field. This activity pattern was bimodal at first, i.e., circatidal activity coinciding with high tides at their habitat. The mean free-running period (i.e., bitidal interval) of this endogenous rhythm was 23.1 h at 10°C, which was significantly shorter than the environmental tidal cycle. In most cases (90% of the records) this bimodal activity became unimodal within 10 d. The unimodal period was 24 to 27.5 h, which is markedly longer than the preceding bimodal period. The bimodal pattern observed in the present study was not observed in the field. The difference between field and laboratory activity patterns can be explained in terms of direct response of the bimodal circatidal rhythm to the day-night cycle in the field. Field observations were made and laboratory experiments conducted between 1988 and 1992.     

Application of Laser Doppler Spectroscopy (LDS) in determining swimming velocities of motile phytoplankton

Pumping rates in Mytilus edulis L. were measured by means of a constant-level-tank method, in which hydrostatic pressure differences between inhalant and exhalant water levels were recorded by means of a laser beam reflected from a tethered mirror floating on the water surface. Hydrostatic pressure gradients were determined to ±0.05 mm H₂O or better. The developed technique of directly measuring pumping rates in mussels is not subject to the artefacts of other methods. The pumping rates measured in M. edulis were substantially higher than those previously determined by means of direct techniques, but similar to the maximum filtration rates, as obtained by means of two indirect techniques, i.e. about 50 ml min^-1 for a 0.15 g dry weight mussel. Positive hydrostatic pressures drastically affected water pumping. The pumping rate decreased linearly with increasing hydrostatic pressures towards a maximum pump pressure between 3 and 5 mm H₂O. Negative pressures only affected the pumping rate slightly or insignificantly, except when the mussels were exposed to rapidly increasing negative pressures. Under this condition a shunt was presumably established between the inner demibranchs, allowing water to bypass the gills.     

Thermal effects on swimming activity and habitat choice in juvenile Pacific cod (Gadus macrocephalus)

The behavioral responses of fishes to temperature variation have received less attention than physiological responses, despite their direct implications for predator–prey dynamics in aquatic ecosystems. In this paper, we describe the temperature dependence of swimming performance and behavioral characteristics of juvenile Pacific cod (Gadus macrocephalus; 75–125 mm total length). Maximum swimming speeds increased with temperature and body size. Routine swimming speeds of Pacific cod in small groups of similarly sized fish (N = 6) increased with body size and were 34 % faster at 9 °C than at 2 °C. The response to temperature was opposite that previously described for juvenile walleye pollock (Theragra chalcogramma), reflecting species-specific differences in behavioral responses. In a separate experiment, we demonstrated the effect of temperature on habitat selection of juvenile Pacific cod: Use of an artificial eelgrass patch in a 5-m-long laboratory tank was significantly greater at 9 °C than at 2 °C. These results illustrate that temperature affects a range of behavioral traits that play important roles in determining the frequency and outcomes of predator–prey interactions.     

Population dynamics and growth of juveniles of the velvet swimming crab Necora puber (Decapoda: Portunidae)

Recruitment variability plays a critical role in determining local population densities of benthic organisms, but extreme vulnerability at the onset of juvenile life is a trait that is largely responsible for population survivorship trends. The aim of the present study was to determine the role of juvenile recruitment in the population structure of Necora puber. Juveniles of N. puber were collected from the lower intertidal of rocky shores of Plymouth Sound (southwest coast of the UK) and monthly size–frequency distribution were used to determine the dynamics and the growth of the population. The parameters of the von Bertalanffy growth function were estimated (K=0.281 year⁻¹; t ₀=0.043; C=0.103; and t _s=0.268) assuming a L _∞=105 mm. Growth was markedly seasonal and present results indicated a slower juvenile growth rate than described previously for N. puber. The recruitment period was extensive and was two times higher in 2001 than in 2000 at the start of the 1+ year, but levelled off at the end of the 1+ year class on three of the four shores studied. Instantaneous mortality as high as 5.1 year⁻¹(99.4% year⁻¹) was observed during the higher recruitment year. Early juvenile mortality appears to be density dependent and a demographic bottleneck appears to limit the number of juveniles on some shores.     

Physiological energetics of cultivated mussel (Mytilus edulis) populations in two Scottish west coast sea lochs

Physiological responses of suspended cultured mussels, Mytilus edulis L., in two Scottish sea lochs (Lochs Etive and Leven) were investigated in their native and transplanted environments, after 15 d, 4.5 mo and 1 yr acclimatization, during the main growing season of May to September 1992. These measurements were integrated by means of the balanced energy equation, and scope for growth was calculated to assess the performance of each stock. Transplanted mussels showed clear signs of stress during the first 15 d after transfer, with low clearance rates and energy retention and high rates of respiration and nitrogen excretion. There were significant differences in some of the physiological responses (clearance, respiration and excretion rates), scope for growth and growth efficiency between the native populations, with the responses of mussels in Loch Etive being more favourable than those in Loch Leven. With newly transplanted mussels after 15 d acclimatization, almost all these measurements also differed significantly from native mussels in their host site and the original stocks but, with the exception of ammonia excretion rates, all the variables of cross-transplanted mussels after 4.5 mo acclimatization were the same as those of the native stock at the host site. Good agreement between observed long-term growth rates and estimated scope for growth suggests that, like growth rate, differences in physiological responses are mainly controlled by environmental factors; i.e., stock or origin had no significant influence on variations in physiological response (except ammonia excretion). The results further indicate that scope for growth estimated during the main growing season can be used to assess the actual growth rate and to compare sites for on-growing.     

Ökologie und Postlarvalentwicklung von Scottomyzon gibberum,eines auf Asterias rubens parasitisch lebenden Copepoden (Cyclopoida siphonostoma)

Scottomyzon gibberum (copepodid stages, males and females) lives ectoparasitically on the sea star Asterias rubens. The female digests the skin of Asterias extra-intestinally, and sucks up the food by means of the sipho-shaped mouth, the structure of which is described. The skin of Asterias rubens, chiefly the tissue of the pedicellariens, forms gall-like structures overgrowing feeding females of S. gibberum. The mature females grow by extension of the chitincuticula and by moulting from a slender, cyclopslike shape to balloon-formed, swollen-up individuals. On the abdomen, simultaneous reductions take place which, in a certain period of life are retrogressive and, after this, start anew. the number of eggs depends on season and the post-larval developmental stage of the female. It varies between 1 and 24 eggs for each eggsack, averaging about 8. Old females are no longer able to swim, they become progressively sessile as their body volume increases, and can no longer leave the sea star. At the beginning of May, the population of S. gibberum on the Helgoländer Austernbank (Southern North Sea) reaches the maximum rate of egg production. At the beginning of June, large numbers of copepodid stages attack the Asterias rubens population. Four weeks later the bulk of them metamorphose into males and females. The males die in August after mating-time. The females develop during autumn and winter. By January of the next year they have attained the size of old females. In spring they procreate the nauplii of the following generation, finally dying in summer or autumn. The cycle of development of populations of S. gibberum of other localities around Helgoland and in the Kattegat, varies from that of the population of the Helgoländer Austernbank. The parasite S. gibberum has so far been found in the area between the Irish Sea in the West, the Big Belt (Baltic Sea) in the East, and the Oslofjord (Norway) in the North. It demands a higher and more constant salinity than its host Asterius rubens and does not, therefore, follow Asterias into the more brackish parts of the Baltic Sea.     

Ecological energetics of Nerita (Archaeogastropoda,Neritacea) populations on Barbados,West Indies

Population energy budgets estimated on the assumption of steady state conditions for Nerita tessellata Gmelin, N. versicolor Gmelin, and N. peloronta L. on Barbados, W. Indies, are presented. Large differences in population structure, and hence energetics, occurred at different localities along the beach. Relatively high proportions (81 to 88%) of the assimilated energy were lost via metabolism. Assimilation efficiencies ranged from 39 to 43%, net growth efficiencies from 5 to 13%, and ecological efficiencies from 3 to 7%. For each species, production (P), energy flow (A) and total energy consumption (C) were expressed as functions of animal size, in order to facilitate gross estimations of the energy components for other populations for which data on size-frequency and density are available. Respiration studies of all three species in the laboratory failed to detect differences between respiration rates in air or under seawater.