Schooling behavior of Antarctic krill (Euphausia superba) in laboratory aquaria: Reactions to chemical and visual stimuli

Antarctic krill,Euphausia superba, often exhibit abnormal behavior in laboratory aquaria, usually hovering in a stationary position, unresponsive to most external stimuli. In the austral summer of 1985–1986 at Palmer Station on Anvers Island, Antarctica, we provided laboratory conditions which inducedE. superba to school in large aquaria. Captive krill swam horizontally and exhibited the full spectrum of behaviors normally displayed while schooling at sea. Schooling krill avoided visually contrasting stimuli, with avoidance distances correlated with stimulus size. Schools responded in qualitatively different ways to presentations of food, chemical compounds, and abrupt increases in light intensity. We describe the conditions necessary for aquarium schooling and discuss the importance of an appropriate social environment for displays of escape, avoidance, and feeding behaviors and of positional preference within the school.     

High connectivity among locally adapted populations of a marine fish (Menidia menidia)

Patterns of connectivity are important in understanding the geographic scale of local adaptation in marine populations. While natural selection can lead to local adaptation, high connectivity can diminish the potential for such adaptation to occur. Connectivity, defined as the exchange of individuals among subpopulations, is presumed to be significant in most marine species due to life histories that include widely dispersive stages. However, evidence of local adaptation in marine species, such the Atlantic silverside, Menidia menidia, raises questions concerning the degree of connectivity. We examined geochemical signatures in the otoliths, or ear bones, of adult Atlantic silversides collected in 11 locations along the northeastern coast of the United States from New Jersey to Maine in 2004 and eight locations in 2005 using laser ablation inductively coupled plasma mass spectrometry (ICP-MS) and isotope ratio monitoring mass spectrometry (irm-MS). These signatures were then compared to baseline signatures of juvenile fish of known origin to determine natal origin of these adult fish. We then estimated migration distances and the degree of mixing from these data. In both years, fish generally had the highest probability of originating from the same location in which they were captured (0.01-0.80), but evidence of mixing throughout the sample area was present. Furthermore, adult M. menidia exhibit highly dispersive behavior with some fish migrating over 700 km. The probability of adult fish returning to natal areas differed between years, with the probability being, on average, 0.2 higher in the second year. These findings demonstrate that marine species with largely open populations are capable of local adaptation despite apparently high gene flow.     

Temporal patterns in three-dimensional structure and activity of schools of the Atlantic silverside Menidia menidia

Temporal patterns in the structure and activity of schools of the Atlantic silverside Menidia menidia were investigated under laboratory conditions using a new computerized video technique for three-dimensional analysis. Fish were collected by seining at Middle Bridge, Pettaquamscutt River, South Kingstown, Rhode Island, USA. Approximately once a week from May to December, 1979, the behavior of a school was videotape-recorded in the laboratory at 30 min intervals from sunrise to sunset under a temperature and photoperiod regime simulating ambient field conditions. Four measurements of structure and activity were computed: (1) swimming speed (SPEED); (2) distance to nearest neighbor (NN); (3) mean direction of travel (DOT); (4) depth in the tank (DEPTH). Results demonstrated a strong seasonal rhythm in the behavior of schools, but were inconclusive in showing periodicities associated with daily, tidal or lunar cycles. NN and DEPTH were significantly different between spring, summer, fall and winter while SPEED changed significantly across 3 seasons (summer and winter were not significantly different). DOT was bimodally distributed, with peaks in spring and fall. Changes in these variables corresponded to shifts in the behavior of silversides from active, synchronized schools in spring and fall to inactive mills in summer and inactive non-schooling groups in winter. Changes in schooling behavior were only partly related to changes in temperature and photoperiod. Patterns of silverside schooling behavior correlated with their reproductive and migratory cycles and may represent an anti-predator strategy.     

Toxicity of the pyrethroid bifenthrin insecticide

Bifenthrin is a chiral synthetic pyrethroid insecticide that has been commonly used for agricultural and domestic pest control over the past decades. Due to its widespread application, residues of bifenthrin has been frequently detected in environmental media, residential areas and biota, thus posing potential risks to the health of wildlife and humans. In particular, bifenthrin exhibits high acute lethal toxicity to aquatic species, and it is the primary contributor to the toxicity of insecticides in waters. Additionally, bifenthrin can also cause sublethal toxic effects on various non-target organisms, including developmental toxicity, neurobehavioral toxicity, oxidative damage, immune toxicity and endocrine disrupting effects. Here we review recent studies about the fate of bifenthrin in the environment and biological systems, the toxicity of the chiral parent compound bifenthrin and the toxic effects of main metabolites. The adverse effects of bifenthrin, identified from both in vitro and in vivo studies, and the potential underlying mechanisms are presented. We discuss the enantiomeric difference in the toxicological effects of bifenthrin, since enantiomers of chiral compounds show different interactions with biological systems. Pyrethroid insecticides metabolites are not acutely toxic, but they have sublethal toxicity, such as endocrine disrupting effects and immunotoxicity. We provide emerging evidence for toxic effects of several main metabolites.     

Schooling decisions in guppies (Poecilia reticulata) are based on familiarity rather than kin recognition by phenotype matching

Evidence from a number of freshwater species indicates that fish prefer to school with familiar individuals. Do they also choose to associate with kin? Our experiment tested this idea using the Trinidadian guppy, Poecilia reticulata, a species whose reproductive biology favours the association of kin groups. Juveniles reared together were able to recognise one another on the basis of either visual or chemical cues, but showed no preference for schooling with unfamiliar kin. We therefore conclude that any naturally occurring kin groups in this species will occur as a result of familiarity rather than as a consequence of kin recognition based on phenotype matching.     

Schooling tendency and foraging benefit in the ocean surgeonfish

Summary Field observations of individuallytagged ocean surgeonfish (Acanthurus bahianus) indicated that schooling provided a foraging benefit: an increase in relative forging time. The magnitude of this increase differed among individuals, primarily due to time budgets of the fish when they were not in schools. The proportion of nonschooling time devoted to foraging was positively correlated with fish size, while the proportion of schooling time that was spent forging was similar for all individuals. Schooling tendency (percentage of time in schools) was positively related to magnitude of foraging benefit and negatively related to fish size. When fish size was held constant by partial correlation, schooling tendency remained positively related to foraging benefit. These results provide evidence that fish which derive a greater foraging benefit from school membership spend more time in schools.     

Interactive effects of predation pressure and insecticide (temefos) toxicity on populations of the marsh fiddler crab Uca pugnax

The interaction of predation pressure with lethal and sublethal effects of temefos (Abate^®) an organophosphorous insecticide, were studied in field populations of Uca pugnax (S.I. Smith). Changes in fiddler crab population densities were followed in open-marsh temefos-treated and untreated test plots and in treated and untreated plots which were caged over to reduce predation by marsh birds. Temefos significantly reduced the population density of U. pugnax in the open test plots but not in the caged plots. These results indicate that temefos has a primarily sublethal effect on the crabs, the effect becoming lethal only after interaction with avian predation. Evidence from the presence of a time-lag effect in the population decrease, from a calculated predation index, and from laboratory studies reported elsewhere of behavioral alteration by temefos also supports the conclusion that temefos primarily impairs the escape response of U. pugnax: this leads to increased predation and subsequently to a decreased fiddler crab population. Such studies of sublethal effects of toxicants and field studies of interactions of lethal and sublethal effects of such compounds with natural population dynamics of affected species are necessary to evaluate possible effects of toxicants on populations.     

Homing behavior of wood thrushes (Hylocichla mustelina)

Summary Using the wood thrush (Hylocichla mustelina) as an example of a typical nocturnal migrant, we employed radio telemetry to follow breeding birds during the course of homing movements following displacements. Seven thrushes were displaced over distances of 6.5 to 17.3 km in a variety of directions from their nesting territories. The thrushes moved in a series of short flights (mean = 2.1 km) performed primarily at dawn. Consequently, the birds took several days to home from even these relatively short displacements. Thrushes flew under clear and solid overcast skies and even in light rain. The pooled individual flights of the birds were significantly oriented in the homeward direction (Fig. 2). Their orientation relative to home did not improve significantly as they progressed toward the goal. Three of the birds were documented to have returned to their home territories. The detailed tracks of the birds preclude the possibility that they homed by random search.     

Associative behavior of the fish Cryptocentrus cryptocentrus (Gobiidae) and the pistol shrimp Alpheus djiboutensis (Alpheidae) in artificial burrows

Observations and experiments on the associative behavior of the fish Cryptocentrus cryptocentrus (Valenoiennes) and the shrimp Alpheus djiboutensis De Man from the Red Sea were carried out in artificial burrows. A signal system, bringing about correlated behavior in fish and shrimp, consisted of antennal contact of the shrimp with the fish, tail undulations by the fish and, finally, emergence of the shrimp. The shrimp emerged from the burrow only in the presence of the fish. A constant antennal contact was maintained by the partners while the shrimp was outside the burrow. Emerging from the burrow, the shrimp pushed the fish towards the entrance. Following visual stimulation, the shrimp always retreated back into the burrow with the fish. However, the further back the shrimp was located inside the burrow, the less intense was its retreat with the fish. In the absence of the fish, visual stimulation of the shrimp had no effect. Cleaning of fish by shrimp was observed within the burrow.     

Toxicity of cupric lon to eggs of the spot Leiostomus xanthurus and the Atlantic silverside Menidia menidia

Experiments were conducted to determine the toxicity of free cupric ion to the eggs of two marine fish: the spot Leiostomus xanthurus, and the Atlantic silverside Menidia menidia. A cupric ion buffer consisting of 5 mM of the chelator, trishydroxymethylamino methane (Tris), and varied concentrations of CuSO₄ was employed to achieve stable cupric ion activities in experimental seawater media. Egg hatch of the silverside appears to be more sensitive to cupric ion than that of the spot. The silverside had 60% inhibition of hatch at a pCu (negative logarithum of cupric ion activity) of 9.4 with complete supporession of hatching at pCu values below 8.2, while the spot had 50% inhibition at a pCu of 9.0 and complete suppression at a pCu of 8.0. Cupric ion was most toxic to the eggs of silverside at or around the time of hatching, whereas a pronounced sensitivity at hatching was not apparent with the eggs of spot. Calculated estimates of the range of cupric ion activity in seawater indicate that natural activity levels may in some instances inhibit the hatching of silverside and spot eggs.     

Provisioning behavior and the estimation of investment ratios in a solitary bee,Calliopsis (Hypomacrotera) persimilis (Cockerell) (Hymenoptera: Andrenidae)

Summary One aspect of behavioral ecology that has received considerable attention, especially by students of social insects, is the relative amount of energy invested by parents in the rearing of male versus female offspring. Sexual selection theory makes predictions about how individuals should allocate their total investment in the sexes. To test these predictions we must accurately quantify the relative cost incurred by a parent in the production of an average individual of either sex. Body weight ratios are the most common estimate of cost ratio, but the correspondence between offspring body weight and energetic investment on the part of the parent has rarely been determined. Calliopsis (Hypomacrotera) persimilis is a solitary, ground-nesting bee whose natural history makes it particularly convenient for studies of investment patterns and foraging behavior. Each day females construct and provision from 1 to 6 cells in linear, closely-spaced series. Each cell is provisioned with pollen from Physalis Wrightii flowers, which is collected on two or three foraging trips. However, the temporal sequence in which two- and three-trip foraging bouts occur is not random. Females invariably begin each day provisioning cells with three trips worth of pollen and usually switch to provisioning the latter cells of the day with just two trips worth of pollen. The sex of the offspring within the same co-linear series of cells also varies non-randomly — female offspring predominate in the first cells of each series and male offspring in the latter cells. The correspondence between the number of foraging trips to provision a cell, the total time spent foraging, and offspring sex was determined for 36 cells. The data indicate a close, though not absolute, relationship between the number of foraging trips and the sex of the offspring: males usually received two trips of pollen, though some received three, whereas female offspring invariably received three trips worth of pollen. A number of potential estimates of the relative cost of female and male offspring production were calculated. Estimates of the cost ratio based on the amount of time spent foraging, adult dry body weight, and pollen ball dry weight all give similar values. Female offspring receive an energetic investment of from 1.3 to 1.5 times that of males. These results support the use of adult dry body weight ratios in the estimation of cost ratios.     

The presence of eggs in the nest and female choice in common freshwater gobies (Rhinogobius brunneus)

In many species of fishes with paternal care, females prefer to spawn with males who are already guarding eggs. We studied the effect of egg presence on female mate choice in common freshwater gobies, Rhinogobius brunneus sp. OR. In our tests, females did not prefer males with eggs, suggesting egg presence per se may not act as a cue to attract females. We also examined the effects of brood size on paternal care and offspring survival to look for possible benefits females could obtain when choosing males with eggs. Both fanning by egg-guarding males and egg survival increased with brood size. The presence of neighboring males did have a significantly negative effect on males' parental activity, which subsequently results in a lower level of egg survival than in solitary egg-guarding males. This result provides a partial explanation for the result of eggs not attracting females to mate.     

Mating behavior in three species of Pseudodiaptomus (Copepoda: Calanoida)

Quantitative studies of mating behavior between conspecific and heterospecific pairs of three closely related species in the genus Pseudodiaptomus reveal differences in the timing of life-history events, species-specific attraction of mates, distinctive tactile cues, multiple spermatophore attachments, and gametic incomptibility or hybrid inviability. These differences may function as reproductive isolating mechanisms among calanoid copepods. Differences in breeding behaviors and associated morphological features are greater between sympatric than between allopatric species, indicating that selection reinforces both behavioral and morphological divergences.     

Feeding behavior and ecology of shallow-water unstalked crinoids (echinodermata) in the Caribbean Sea

The feeding behavior, living position, and skeletal morphology of 8 species of reef-dwelling Caribbean comatulid crinoids are intimately related to the regime of water movement prevailing in the microhabitat. These adaptations are related to the dependence of the crinoid suspension-feeding mechanism on externally produced water movements for a continuous food supply. Greater numbers of co-occurring comatulid species (6 to 7) and larger populations have been found off Colombia and Panamá than off Curaçao and Jamaica (4 species). It is suggested that these differences may be related to increased or diversified primary productivity close to the larger land masses. Overal food availability as determined by primary productivity may, thus, be an important factor controlling the regional diversity and abundance of these species.     

Mating behavior of Labidocera aestiva (Copepoda: Calanoida)

The calanoid copepod Labidocera aestiva Wheeler exhibits a ritualized mating behavior. Sensory hairs and spines and integumental pores on the male and female are believed to play a regulatory role in the mating encounter. Scanning electron microscopy (SEM) revealed approximately 20 unusual pore structures (pit-pores) on the right ventrolateral surface of the female's abdominal segment, the area where the spermatophore coupling device is attached. Prior to spermatophore transfer, the male vigorously strokes this area with the modified endopod of his left fifth leg to prepare the pit-pore region for attachment of a new spermatophore. Transmission electron microscopy (TEM) indicated that the cells underlying each pit-pore may have a secretory function. We hypothesize that the pit-pores secrete a substance which dissolves the cement binding the coupling device to the abdomen and aids the female to remove a discharged spermatophore from her urosome.Contribution No. 116, Harbor Branch Foundation, Inc.     

Mating behavior of Centropages typicus (Copepoda: Calanoida)

Observations were made on approximately 300 mating couples of Centropages typicus Krøyer. Mating behavior consists of 4 distinct stages: pre-copulation, spermatophore extrusion, copulation, and post-copulation. Successful copulation requires proper positioning of the spermatophore complex on the female urosome and is dependent upon precise movements and orientation of the male during the mating encounter. Sub-optimal mating encounters, resulting in the improper placement of the spermatophore complex, were observed and adaptations tending to reduce spermatophore wastage are discussed.Contribution No. 62, Harbor Branch Foundation, Inc.