Showing papers in "The Biological Bulletin in 1976"
TL;DR: Isolation of bacteria from the luminous organ of the fish Monocentris japonica has revealed that the organ contains a pure culture of luminous bacteria, the first time that P. fischeri has been identified in a symbiotic association.
Abstract: Isolation of bacteria from the luminous organ of the fish Monocentris japonica has revealed that the organ contains a pure culture of luminous bacteria. For the four fish examined, all contained Photobacterium fischeri as their luminous bacterial symbiont. This is the first time that P. fischeri has been identified in a symbiotic association.A representative isolate (MJl) of the light organ population was selected for in vivo studies of its luminous system. Several physiological features suggest adaptation for symbiotic existence. First, MJl has been shown to produce and respond to an inducer of luciferase that could accumulate in the light organ. Secondly, the specific activity of light production was seen to be maximal under low, growth-limiting concentrations of oxygen. Thirdly, unlike another luminous species (Beneckea harveyi), synthesis of the light production system of these bacteria is not catabolite repressed by glucose—a possible source of nutrition in the light organ. Fourthly, when grown aerob...
220 citations
TL;DR: Somatic growth and reproductive characteristics of an intertidal sponge, Haliclona permollis, were followed over a period of four years in a population on the central Oregon Coast, and temperature appears to have a secondary role in reproductive behavior but may influence sexual expression.
Abstract: 1. Somatic growth and reproductive characteristics of an intertidal sponge, Haliclona permollis, were followed over a period of four years in a population on the central Oregon Coast.2. Methods have been developed for estimating the instantaneous tissue temperature of sponges, calculating egg and embryo production, and measuring somatic growth rate.3. Initiation of oogenesis during early March is best related to increases in incident light.4. A maximum rate of oogenesis (1.5 eggs/mm3/day) is found near the first two weeks of March, and the annual oocyte production was constant at about 44 oocytes/mm3.5. Temperature appears to have a secondary role in reproductive behavior but may influence sexual expression.6. Development of embryos is related to particulate food supply in late spring.7. Somatic growth rates are minimal from December to April and reach a maximum average of 1% per day in the fall.
114 citations
TL;DR: Field studies demonstrate that the gorgonian coral Leptogorgia virgulata assumes a fan-shaped morphology oriented at right angles to prevailing tidal currents, and laboratory studies show that fan- shaped colonies oriented perpendicular to water currents capture more Artemia per unit time than the same colonies oriented parallel toWater currents.
Abstract: Field studies demonstrate that the gorgonian coral Leptogorgia virgulata assumes a fan-shaped morphology oriented at right angles to prevailing tidal currents. Laboratory studies using a recirculating water tunnel and Artemia salina nauplii as food show that fan-shaped colonies oriented perpendicular to water currents capture more Artemia per unit time than the same colonies oriented parallel to water currents. Several feeding strategies which may operate at various current speeds are suggested. Possible mechanisms controlling feeding response and the selective advantage of colony morphology and orientation as related to feeding and resistance to hydrodynamic forces are discussed.
97 citations
TL;DR: The aggregating form of the anemone Anthopleura elegantissima often lives in closely packed groups composed of genetically identical individuals that remain separated from each other because contact between non-clonemates elicits intraspecific aggression.
Abstract: The aggregating form of the anemone Anthopleura elegantissinla often lives at tached to large boulders and rocky outcroppings in closely packed groups. These are composed of genetically identical individuals, the products of asexual reproduc tion ( Francis, 1973a) . Contact between the tentacles of genetically different (non clonemate) members of the species elicits aggression in one or both animals, while similar contact between clonemates is tolerated passively. Clonal aggregations re main separated from each other ( Fig. 1) at least partly as a result of intraspecific aggression occurring at their adjacent borders (Francis, 1973b). This aggressive behavior is rather elaborate, involving inflation of specialized effector organs, the blunt, white-tipped acrorhagi (Fig. 2), and stretching and bending movements of the oral disc and column that bring these turgid acrorhagi into contact with the non-clonemate adversary. During contact, scraps of the white acrorhagial ectoderm are applied to the body of the adversary where they adhere, slowly firing their batteries of large atrich nematocysts. Both the acrorhagi them selves and their large atrich nematocysts are deployed only during aggression (Abel, 1954; Bonnin, 1964; Francis, 1973b). For an animal with a relatively limited behavioral repertoire and quite limited specialization of tissue types, this extensive investment in intraspecific aggression is remarkable. In large clonal aggregations relatively few of the anemones are in a position to engage in battles at any given time. One niight therefore expect the costs of intraspecific aggression to be distributed unevenly in such groups, with those ani mals at or near an interclonal border bearing more of the defense costs. To in vestigate this, I collected anemones from large, compact aggregations and compared individual size, sexual and asexual reproductive state, and acrorhagus size and number for animals from different locations within each clonal aggregation.
88 citations
TL;DR: Some embryos of Thais emarginata attain twice the shell length of others by the time of hatching, and these nurse-egg feeders reach variable hatching sizes because some embryos share their yo...
Abstract: Some embryos of Thais emarginata attain twice the shell length of others by the time of hatching (0.9 to 1.8 mm, +44% to -31%, about the mean). Larger hatchlings must have acquired more nurse eggs than smaller ones. Embryos tend to reach the same size when nurse eggs are scarce (in crowded capsules), and size differences are most apparent when nurse eggs are present in excess. Therefore, competition among embryos contributes little to hatching size differences. Embryos are distributed haphazardly among capsules; some capsules contain only one embryo which becomes large, while others contain as many as 33 embryos, each of which remains small. Nurse eggs are distributed more regularly. Embryos are also distributed haphazardly among capsules of Acanthina spirata. Each embryo of A. spirata has on average only 1.67 nurse eggs, and hatching size is correspondingly less variable (0.55-0.75 mm, +15% to -16%, about the mean). These nurse-egg feeders reach variable hatching sizes because some embryos share their yo...
81 citations
TL;DR: The existence of a rich motor innervation supplying the ciliated epithelium in Mangelia has been established using optical and electron microscopy and patterns of electrical signals during periods of ciliary arrest are shown.
Abstract: 1. The locomotory cilia of Mangelia and Pneumoderma larvae undergo arrests spontaneously and in response to tactile stimulation. These events are often associated with muscular contractions in an overall response thought to be protective in nature.2. Isolation of the ciliated bands from the central nervous system abolishes the ability for coordinated ciliary arrests and the cilia show continuous metachronal beating.3. Recordings with suction electrodes attached to the surface show patterns of electrical signals during periods of ciliary arrest. Intracellular recordings with glass microelectrodes from single ciliated cells in Pneumoderma show rapidly rising, slowly decaying, all or none 50 mV spikes when the cilia undergo arrest. There are no fluctuations in membrane potential during metachronal beating.4. The existence of a rich motor innervation supplying the ciliated epithelium in Mangelia has been established using optical and electron microscopy. The nerve endings appear to derive from neurons whose c...
79 citations
TL;DR: Dendraster excentricus used the spines and tube feet to capture large food items such as algal fragments, in addition, the large bidentate pedicellariae were used to capture active prey.
Abstract: 1. Dendraster excentricus used the spines and tube feet to capture large food items such as algal fragments. In addition, the large bidentate pedicellariae were used to capture active prey.2. Rejection of food occurred at the test surface or at the Y junction of the food grooves. The rejection response was well defined.3. Specimens of Dendraster from a protected outer coast location ate primarily small crustaceans, diatoms, algal fragments, and sand grains. In a summer sample, diatoms were the most abundant item in the diet; in a winter sample, crustaceans predominated the diet.4. Sand dollars from a protected outer coast sand dollar bed had more food of higher organic content in their guts than did sand dollars from two bay habitats.5. Food passed through the stomach in 5 hr and through the entire gut in 2 days. Specimens of Dendraster from a protected outer coast habitat fed continuously.6. Individuals of Dendraster were nonselective with respect to particle size in the range of 30 µm to 100 µm. Sixty p...
64 citations
TL;DR: The behavior of the planula of Cyanea capillata (Linneaus) is studied in the laboratory to determine if it responds to environmental cues in a way which may account for the distribution of its sedentary scyphistoma stage in the field.
Abstract: The behavior of the planula of Cyanea capillata (Linneaus) is studied in the laboratory to determine if it responds to environmental cues in a way which may account for the distribution of its sedentary scyphistoma stage in the field.The planulae react to gravity, water chemistry, surface texture, and possibly to light. They exhibit an initial geopositive response in well-aerated sea water, but become active and geonegative under conditions associated with local depletion of oxygen. Their attachment follows, and is usually upside-down on a horizontal surface. They attach with greatest frequency on substrates that are rough, and give evidence of discriminating among surfaces of different rugosity. The planulae possibly show a weak photonegative response at the time of attachment; confirmation of this photic response requires further work. These sequential responses shown in the laboratory result in an orientation at the time of attachment which is in agreement with the position usually occupied by the scyp...
64 citations
TL;DR: The longer the pre-treatment period with lead, the less readily is the metal removed from the cells in the shorter period, and much of the adsorbed lead is eluted.
Abstract: 1. Uptake of lead by Phaeodactylum tricornutum or Platymonas subcordiformis, exposed to lead concentrations ranging from 0.02 to 0.8 mg/l, occurs in two phases.2. The first phase, completed within minutes after addition of lead, can be described by a Freundlich adsorption isotherm. The number of binding sites per cell seems to be limited. Cells of Phaeodactylum become "saturated" when the lead burden reaches 11,640 µg/g (dry weight), equivalent to about 6.7 x 108 Pb atoms per cell.3. In the second phase, the lead content of Platymonas cells continues to rise slowly, whereas that of Phaeodactylum declines after two or three days.4. The addition of 2 x 10-6 M EDTA to a solution containing 0.5 x 10-6 M Pb completely inhibits the uptake of the metal by Phaeodactylum cells. When diatom cells, pre-treated with lead, are resuspended in a higher concentration of EDTA, 10-2 M, much of the adsorbed lead is eluted. The longer the pre-treatment period with lead, the less readily is the metal removed from the cells in...
63 citations
TL;DR: The present paper examines timing of molting and repro duction, and suggests that lunar and tidal synchrony of molts in the population 468 is suggested.
Abstract: One of the constraints imposed upon arthropods by their protective exoskeleton is the necessity to molt. While the physiology and morphogenesis associated with the molt cycle in crustaceans has commanded a great deal of attention (e.g., Pas sano, 1960 ; Drach and Tchernigovtzeff, 1967 ; Stevenson, 1972 ; Aiken, 1973; Davis, Fyhn, and Fyhn, 1973 ; Reaka, 1975a) , few workers have examined the process of molting in an evolutionary perspective. This study examines the eco logical and evolutionary consequences of molting in stomatopod crustaceans. Mantis shrimp are primitive members of the Malacostraca ( Brooks, 1962; Siewing, 1963 ; Holthuis and Manning, 1969 ; Schrani, 1%9a, b, 1973 ; Burnett and Hessler, 1973 ; Reaka, 1975b) , but they possess a highly specialized life style which may be associated with unique molting and reproductive adaptations. Stomatopods frequently live in species assemblages where as many as five con generics occupy indistinguishable microhabitats in one tidepool (Reaka, 1972, and in preparation) and seven congenerics may occupy one tide flat (this study). Protection from predation is afforded by burrows or cavities in mud, sand, rocks or coral. Stomatopods employ intense and sometimes lethal agonistic behavior against conspecifics and congenerics while fighting to obtain or retain burrows and in addition are rapacious carnivores. All crustaceans are susceptible to conspecific or other predators when molting and often possess behavioral adaptations to minimize mortality at this time (Passano, 1960). This vulnerability is considerably magnified in molting stoma topods because of their behavior and frequent sympatry with closely related species; if not killed by another mantis shrimp, a stomatopod may be displaced from its hole and exposed to predation by fishes (Townsley, 1953; Camp, 1973). Large size is an obvious advantage for pursuit and overpowering of prey, defense against predators, conspecific and congeneric fighting, and reproduction (Reaka, 1974, 1975c), but carries the disadvantage of repeated molts. How, then, do stomatopods minimize the effects of molting while maintaining their tactics of predation and contest competition? Reclusive and submissive behavior, as well as sealing the entrance of the burrow, reduce vulnerability at the molt in stomatopods; the stages of morphogenesis associated with incapacitation and exuviation are abbreviated in several aggressive taxa of crustaceans but especially in stomatopods; and asym metrical stages of the molt cycle suggest that the early premolt may be a waiting period, whereupon initiation of the molt progresses rapidly following the correct cue (Reaka, 1975a). The present paper examines timing of molting and repro duction, and suggests that lunar and tidal synchrony of molting in the population 468
63 citations
TL;DR: During acclimation of mussels to low salinity, free amino acids are released intact from the cells into the hemolymph and the subsequent transitory increase in hemoly mph ammonia concentrations and external ammonia excretion rates is probably due to degradation of the effluxed amino acids.
Abstract: 1. Free amino acid concentrations in the hemolymph increase rapidly in company with a decrease in the tissue free amino acid pool of propped-open M. demissus exposed to low salinity.2. As acclimation proceeds, blood amino acid concentrations level off and an increase in both hemolymph ammonia concentration and external ammonia excretion occurs.3. Finally, hemolymph amino acid concentrations decrease toward control levels, followed by hemolymph ammonia concentration and external ammonia excretion rates.4. Following complete acclimation of mussels to high or low salinity, ammonia excretion rates are the same. However, hemolymph free amino acid concentrations are lower in animals adapted to low salinity.5. These results show that during acclimation of mussels to low salinity, free amino acids are released intact from the cells into the hemolymph. The subsequent transitory increase in hemolymph ammonia concentrations and external ammonia excretion rates is probably due to degradation of the effluxed amino aci...
TL;DR: The precise stage of the animal in the molt cycle determines whether growth and/or DNA synthesis decrease or cease in the remaining primary regenerates.
Abstract: 1. Following the loss of one or more primary regenerates from the land crab, Gecarcinus lateralis, before a critical stage of the molt cycle (probably D1, early), secondary regenerates form to replace those lost.2. Although loss of at least five limbs from an intermolt animal is required to initiate molting preparations (Skinner and Graham, 1972) loss of only one primary regenerate, prior to the critical time, is sufficient to inhibit these preparations.3. Following the loss of one or more primary regenerates before a critical time, the rate of growth and the synthesis of DNA in other primary regenerates that remain in situ decrease or cease temporarily (10 to 14 days).4. The precise stage of the animal in the molt cycle determines whether growth and/or DNA synthesis decrease or cease in the remaining primary regenerates. Loss of regenerates early in D0 (R = 7-10) causes a decrease; loss of regenerates later in D0 or early D1 (R = 10-17) causes complete inhibition.5. The duration of the premolt period is ...
TL;DR: There was strong maternal (nongenetic) effects on age of maturity of males (which benefit from accelerated maturation) and on size, especially of females (which would benefit from enhanced fecundity).
Abstract: Heritabilities (h2, the ratio of additive genetic variance to total phenotypic variance) were estimated for a number of traits of Eurytemora herdmani from families of known parents reared with excess food at 10°, 12.5°, and 15° C. Age of maturity was strongly heritable only among female offspring at 15° C and size only among male offspring at 15° C. This temperature is extreme for waters near Halifax, Nova Scotia. Low and sometimes nonsignificant heritabilities at 10° and 12.5° C are as expected at these natural temperatures for fitness traits that have had their genetic variance trimmed by natural selection. There were strong maternal (nongenetic) effects on age of maturity of males (which benefit from accelerated maturation) and on size, especially of females (which would benefit from enhanced fecundity). Adult size and age of maturity are negatively correlated, so that growth rate should be even more strongly heritable. There is a suggestion that survivorship (not significantly heritable) is maternally...
TL;DR: In Washington State, Paranemertes peregrina spawns in spring and summer, with minor spawning periods in fall, and feeds exclusively on polychaetes; at both mud flats Platynereis bicanaliculata, an annual, was abundant and the dominant prey organism.
Abstract: In Washington State, Paranemertes peregrina spawns in spring and summer, with minor spawning periods in fall. Juveniles from spring spawning are first easily seen the following fall, when the population consists of both adults and juveniles. Throughout winter adults die and juveniles mature, becoming ripe for the spring and summer spawnings. These adults die the following winter; the life span is thus 1.5 to 1.75 years.P. peregrina feeds exclusively on polychaetes; at both mud flats Platynereis bicanaliculata, an annual, was abundant and the dominant prey organism.Observations in nature and in artificial tidal flats constructed in the laboratory permitted study of foraging behavior and activity patterns. P. peregrina emerges from its burrow when exposed by the receding tide and searches haphazardly until it contacts acceptable prey. After contact, feeding takes seven to eight minutes. Then P. peregrina returns to its burrow by following its own mucus trail. Individuals often remain within a one meter radi...
TL;DR: Discrimination of Modiolus modiolus and Mytilus edulis veligers is generally possible through a comparison of the following larval characteristics: hinge-line lengths, to...
Abstract: 1. Spontaneous spawning of Modiolus modiolus occurred under laboratory conditions at a temperature of approximately 14° C, and larvae were successfully cultured through settlement and metamorphosis.2. Fertilized egg diameters varied from 78 to 90 µ with a mean of 85 µ.3. The smallest shelled veliger observed had length, height, and straight-hinge dimensions of 105, 90, and 95 µ, respectively. The distribution of hinge-line lengths remained constant over time, with a mean at 100 µ and extremes of 90 and 110 µ.4. As total lengths reached 150 to 165 µ the hinge-line was obscured by the appearance of a low, rounded umbo which subsequently developed into a knobby protrusion.5. Pigmented eyespots began appearang as larvae exceeded 270 µ in size, and the full-grown foot of the pediveliger became functional as larvae surpassed 295 µ in length.6. Discrimination of Modiolus modiolus and Mytilus edulis veligers is generally possible through a comparison of the following larval characteristics: hinge-line lengths, to...
TL;DR: The reproductive elements of Haliclona loosanoffi were found to be very similar to the corresponding elements of other North American haliclonids, and the sex ratio is about 1:1.
Abstract: 1. A general description of the reproductive elements of Haliclona loosanoffi is given. They were found to be very similar to the corresponding elements of other North American haliclonids.2. Haliclona loosanoffi apparently is gonochoric, and the sex ratio is about 1:1. Abortive small oocytes are found in many male specimens during the latter part of the reproductive period.3. The reproductive period of Haliclona loosanoffi in the Mystic Estuary, Connecticut is from late May or early June to late July or early August; but specimens with only small oocytes or spermatic cysts may be found until late September.4. The reproductive period at Mystic, Connecticut is about two months earlier than at Milford, Connecticut and occurs at about the same time of year as the major reproductive period at Hatteras Harbor, North Carolina. Water temperature appears to be a major factor determining the reproductive period.5. Very small specimens of Haliclona loosanoffi, as well as large ones, have high densities of reproduct...
TL;DR: Density separation of blood cells has been achieved; this result coupled with various cell morphologies suggests that different cells may represent different maturational stages in a developmental process.
Abstract: 1. The blood plasma of Ascidia nigra has been characterized with regard to pH, salinity, and ultraviolet-visible absorption. Whole blood of A. nigra has been characterized with regard to cell count, cellular volume, hemoglobin (iron) content, vanadium content. Blood cell types have been examined, categorized, and differentially counted.2. Epr and nmr studies prove that trivalent vanadium is present. Staining of whole blood slides with OsO4 reagent identify the vanadium-carrying cells as being mainly the green globular blood cells. The observed uv-vis absorption spectrum does not correlate well with known vanadium(III) complex spectra.3. Density separation of blood cells has been achieved; this result coupled with various cell morphologies suggests that different cells may represent different maturational stages in a developmental process.4. Vanadium analyses of layerings of cells of different densities suggest that vanadium may be present in more than one type of blood cell, where, when not present as van...
TL;DR: There is significant heterogeneity among the three locations with respect to PHI genotype frequencies, suggesting that there may be geographical differentiation of the populations.
Abstract: 1. Metridium senile was studied for phosphohexose-isomerase variation at three locations on Cape Cod, Massachusetts: Woods Hole, Cape Cod Canal, and Barnstable Town Boat Harbor.2. All three locations exhibited significant polymorphism for PHI.3. Mapping of individual polyps was performed at Barnstable to analyze spatial distributions of clones and genotypes.4. In Barnstable, PHI does not depart significantly from Hardy-Weinberg expectations at the time of establishment of new polyps, and establishment of larvae is spatially random with respect to PHI genotype.5. Asexual reproduction was used as a measure of the relative success of different PHI genotypes. There are indications that not all genotypes are equally likely to produce large clones.6. There is significant heterogeneity among the three locations with respect to PHI genotype frequencies, suggesting that there may be geographical differentiation of the populations.7. Sessile, asexual organisms provide powerful tools for examining the dynamic aspect...
TL;DR: A shadow response consisting of oriented movement to light and gravity was studied by means of a closed circuit television system for stage I zoeae from the crab Rhithropanopeus harrisii.
Abstract: 1. A shadow response consisting of oriented movement to light and gravity was studied by means of a closed circuit television system for stage I zoeae from the crab Rhithropanopeus harrisii.2. If larvae are irradiated at an intensity that induces positive phototaxis and the light is extingushed, both light-and dark-adapted larvae show a descent. Since this response involves passive sinking, it is termed a sinking response. The minimum time that the light must be extinguished to evoke the response is 20 to 30 milliseconds.3. If the light intensity is reduced to a level that should induce negative phototaxis, light-adapted larvae show a sinking response followed by a negative phototaxis. The time delay between the responses is related to the initial stimulus intensity and duration.4. The minimum decrease in intensity that induces the sinking response is equivalent to a reduction by a 0.5 O.D. neutral density filter while the maximum response occurs at optical densities of 1.0 to 1.1 and greater. These value...
TL;DR: When the euryhaline decapod Carcinus maenas is transferred from sea water to a medium more dilute than 75% sea water, the frequency of heart beat increases.
Abstract: When the euryhaline decapod Carcinus maenas is transferred from sea water to a medium more dilute than 75% sea water, the frequency of heart beat increases. The cardioacceleratory response is probably mediated by external rather than internal receptors, and the parameter that is sensed in neither the total osmotic strength of the medium, nor the concentration of any single ion. Although it is not yet determined whether the heart responds to a hormonal or nervous signal, it is likely that the control mechanisms are similar to those which mediate the water permeability changes in Carcinus and other euryhaline crabs.In somewhat more than half of the crabs tested, the frequency of scaphognathite beating is markedly reduced when the animal is exposed to dilute external medium.
TL;DR: Brachyuran crabs can autotomize limbs at a preformed breakage plane in the basi-ischium, and subsequently regenerate them, culminating in ecdysis and unfolding of the new limb.
Abstract: Brachyuran crabs can autotomize limbs at a preformed breakage plane in the basi-ischium, and subsequently regenerate them. The limbs grow in a folded posi tion and at ecdysis they unfold and become functional. The progress of limb re generation has been divided into stages by Bliss (1956) . After an initial lag period, basal growth occurs which establishes the primary organization of the limb (Hodge, 1956) . This may be followed by a plateau of anecdysis if environmental conditions are not suitable. The next stage, one of intensive growth and further development of existing tissues, is the proecdysial stage, culminating in ecdysis and unfolding of the new limb. A terminal plateau often occurs just prior to ecdysis. Regenerating limb buds of crabs are generally described in terms of the regeneration index, or “?�R-value†(Bliss, 1956), which is (limb bud length/carapace width) X 100. Use of the R-value facilitates comparisons between crabs of different sizes. Growth of the regenerating limb is related to the molt cycle of the crab. Factors that influence the molt cycle can influence the rate of regeneration, and vice versa. The molt cycle of Brachyura has been divided into five major stages by Drach ( 1939) . Regenerating limbshave been used asanindexto thestage of proecdysis for crabs, since the growth of limb buds is closely correlated to the progress of proecdysis. The neurosecretory and hormonal systems exert important controls over the molt cycle. For example, in some species of crabs, ecdysone will accelerate proecdysial regenerative growth, leading to molt (Passano and Jyssum, 1963) . Basal growth was found to be independent of the hormone. Removal of eyestalks, which contain molt-inhibiting hormones produced by the X-organ, will lead to accelerated re generation and early ecdysis. Removal of many limbs (multiple autotomy) will also accelerate regeneration and molting in many species of crabs ( Skinner and Graham, 1972) . Fingerman and Fingerman ( 1974) have shown that removal of as few as two limbs will accelerate ecdysis in fiddler crabs. The neurosecretory system, which controls the niolt cycle, is itself affected by the external environment. Bliss and Boyer ( 1964) found that in the land crab, Gecarcin us lateralis, darkness, moderate temperature, and solitude were necessary environmental factors to permit proecdysial growth. These factors are likewise those which would increase the crab's chances of surviving ecdysis. Light, high temperature, and the presence of another crab inhibited proecdysial growth. The presence of dry sand delayed but did not stop regeneration. Rao ( 1965) found that light did not inhibit proecdysial growth in the ghost crab, Ocypode, if crabs were on a light background, and that privacy was a critical factor only for larger crabs, smaller individuals completing regeneration and niolting in the presence of
TL;DR: The pattern and form of colony growth in the ectoproct Conopeum tenuissimum was found to be diet-dependent and well fed colonies were rounded in shape and characterized by high zooid number to generation number ratios.
Abstract: 1. The pattern and form of colony growth in the ectoproct Conopeum tenuissimum was found to be diet-dependent.2. Poorly nourished colonies were characterized by their straggling shape and low zooid number to generation number ratios. These colonies apparently attempted to maximize substrate covered, facilitating location of a more favorable nutrient regime.3. Well fed colonies were rounded in shape and characterized by high zooid number to generation number ratios. These colonies maximized the number of zooids produced in their already favorable area, creating colony reserves, and preparing for reproduction.4. Initial growth in all colonies was exponential, but after a few days of culture growth, rates varied with food used. The chlorophyte flagellate Dunaliella tertiolecta and the dinoflagellate Gymnodinium simplex were good foods, supporting growth to more than 1,000 zooids and sexual maturation within the 42 day culture period. The chrysophyte flagellate Monochrysis lutheri and Va-12 (an un-named chrys...
TL;DR: Blue crabs from five locations on the Gulf of Mexico and Atlantic Ocean coasts of Florida, USA, and juvenile crabs reared in the laboratory, were examined for the incidence of cheliped laterality (location of the crusher and cutter chelipeds).
Abstract: Blue crabs from five locations on the Gulf of Mexico and Atlantic Ocean coasts of Florida, USA, and juvenile crabs reared in the laboratory, were examined for the incidence of cheliped laterality (location of the crusher and cutter chelipeds). The proportion of crabs possessing the crusher cheliped on the right decreased with size (age) from 100% in the smallest crabs to about 74% in the largest crabs. Crabs with two cutter chelipeds were not uncommon and apparently resulted from regeneration of a cutter regardless of which cheliped was autotomized. Only 0.4% of all crabs possessed two crusher chelipeds.
TL;DR: The close association of the increased rates of protein metabolism with the smoltification process in freshwater fish, the continuation of this increase in the saltwater fish and the decrease found in the post-smolts remaining in fresh water suggest that the processes which bring about the transformation of a stenohaline freshwater trout to a euryhaline trout increase its rates ofprotein metabolism.
Abstract: If growth is considered over the complete annual cycle, saltwater trout grow at a greater rate than freshwater trout when fed ad libitum. However, during the spring, the growth rate of the freshwater smolt increases to a level equivalent to that of the saltwater fish. This is not primarily a result of differences in temperature of the natural seawater and freshwater environments, nor is it associated with differences in food quality, consumption or assimilation rates, but results from the increased rates of protein synthesis and degradation found in freshwater smolt and saltwater fish. The close association of the increased rates of protein metabolism with the smoltification process in freshwater fish, the continuation of this increase in the saltwater fish and the decrease found in the post-smolts remaining in fresh water, all suggest that the processes which bring about the transformation of a stenohaline freshwater trout to a euryhaline trout increase its rates of protein metabolism. It is known that v...
TL;DR: The Tintinnida of the Woods Hole, Massachusetts region were identified during two consecutive summers; loricae of eleven species of the agglutinated variety were studied by scanning electron microscopy and there were distinct differences in the types of particles utilized.
Abstract: The Tintinnida of the Woods Hole, Massachusetts region were identified during two consecutive summers; loricae of eleven species of the agglutinated variety were studied by scanning electron microscopy. There were distinct differences in the types of particles utilized. In some species, quartz was incorporated almost to the exclusion of all other minerals. Biogenic particles such as fragments of diatom frustules, protozoan shells, and coccoliths were conspicuous on a number of species. The authors suggest that this observable difference in the nature of the agglutinated particles is significant at the generic level.Variability in the sizes and shapes of the lorica of Tintinnopsis acuminata and T. dadayi are discussed in relation to cell growth and lorica developmental processes.
TL;DR: The fate of Artemia (brine shrimp) nauplii offered as food to Hastigerina pelagica in laboratory cultures was determined using light and electron microscopy.
Abstract: The fate of Artemia (brine shrimp) nauplii offered as food to Hastigerina pelagica in laboratory cultures was determined using light and electron microscopy.Contact between prey and foraminiferal rhizopodia leads to immediate attachment. Adhesive substance is secreted and rhizopodia invade crevices of the prey. penetrate beneath the cuticle, and begin disruption of prey tissue. Some tissue masses and cells are dislodged and digestion is begun outside of the test as indicated by lysosomal enzymes surrounding partially degraded prey tissue within spaces created by surrounding rhizopodia. Dislodged prey tissue is sequestered into food vacuoles and carried into the intrashell cytoplasm where digestion also occurs. The digestive enzymes are secreted by the Golgi apparatus in membrane-bound vesicles (lysosomes) which are carried throughout the cytoplasm and fuse with the food vacuoles to produce digestion. The carapace or cuticle of digested prey is discarded and undigested waste material in residual vacuoles i...
TL;DR: In Juxtamusium, the concertina-like movements of the gill plicae could be correlated with the functional state of the water-transporting lateral cilia, and in Pteria and both species of Pycnodonte the response to mechanical stimulation was abolished.
Abstract: +An extensive literature deals with the function of the exposed gill or gill frag ments of suspension-feeding bivalves in transporting water and in retaining and sorting particles suspended in the water (see JA˜rgensen, 1966) . These studies have led to the view that normal feeding results from the largely independent activities performed by the three main ciliary systems on the gill filaments : the lateral cilia transport water, the latero-frontal cirri intercept and retain particles suspended in the water, and the frontal cilia sort and transport retained particles to ciliary tracts along the gill bases or the free margins of the demibranchs. The function of the latero-frontal cirri in straining particles from the water passing through the interfilanientar spaces and in transferring them to the frontal ciliary tracts was studied in the mussel Mytilus edulis by Dral (1967) , who concluded that the intercirral distances, 2—3 @m,determined how small particles could be efficiently retained. Measurements of the efficiency with which Mytilus and other bivalves clear suspended particles from the ambient water showed, however, that even smaller particles could be efficiently retained. The discrepancy between predicted and measured efficiencies of particle retention in Mytilus seemed to vanish when it was observed that the cirri are featherlike struc tures, composed of cilia of different lengths with distal ends branching off from the main stem of the cirrus at regular intervals of about one 1zm (Moore, 1971). It was assumed that these side branches of the cirri form the filter that is responsible for the retention of particles smaller than the intercirral spaces (Moore, 1971; Owen, 1974a, b). However, other suspension feeders that possess gills with short (oysters) or undeveloped (scallops) latero-frontal cirri can also efficiently retain particles (JA˜rgensen and Goldberg, 1953; Haven and Morales-Alamo, 1970; Vahl, 1972a, b, 1973a, b). Moreover, the M'@tilus gill may under circumstances become leaky even to large particles despite apparently normally beating latero-frontal cirri (JA˜rgensen, 1975). It was, therefore, found of interest to examine more closely how exposed gills and isolated gill fragments of various gill types transport water and deal with suspended particles, and especially to compare the efficiency with which particles are retained in relation to the size and function of the latero frontal cirri. Serotonin (5-HT) has been found to act in a cilio-excitatory way on the bivalve gill. It has been assumed that the serotonergic nerves demonstrated in gill fila ments of several bivalves control ciliary activity, especially of the lateral cilia (Aiello, 1960, 1970; Gosselin, 1961; Paparo, 1972; Paparo and Finch, 1972; Stephano and Aiello, 1975). Less is known about the role that serotonergic in nervation may play in controlling the activity of the latero-frontal cirri (or other
TL;DR: Renilla kollikeri is morphologically adapted to live in turbulent benthic areas by having a horizontally expanded rachis which offers less resistance to water flow than the vertically expanded rACHis of most pennatulaceans.
Abstract: 1. Renilla kollikeri is morphologically adapted to live in turbulent benthic areas by having a horizontally expanded rachis which offers less resistance to water flow than the vertically expanded rachis of most pennatulaceans. Furthermore, the colony is anchored by an extensible and flexible peduncle which is the largest (in relation to rachis height) among the Pennatulacea.2. R. kollikeri has a number of behavioral adaptations to life in turbulent water. In response to increasing flow it alters its rachis curvature and peduncle extension to decrease resistance and increase anchoring, respectively. The sea pansy can emerge from large deposits of sediment suddenly placed upon it. Such shifts in sediment are a common occurrence in its habitat. Renilla has a specific set of behavioral characteristics which re-establish the colony quickly if it is uprooted from the substrate.3. The anchoring ability of individual colonies, which decreases as the size of the colony increases, allows small colonies to inhabit t...
TL;DR: Aposymbiotic hydra survive and reproduce as well as green animals, and serve as important control and ex perimental organisms in many experiments examining the physiology and morphol ogy of the symbiosis.
Abstract: through circumstances described below, have become algal-free. Aposymbiotic hydra survive and reproduce as well as green animals, providing they are fed regularly ( Muscatine and Lenhoff, 1965 ) , and serve as important control and ex perimental organisms in many experiments examining the physiology and morphol ogy of the symbiosis. For instance, experiments regarding the nutritional basis of the symbiosis ( Muscatine and Lenhoff, 1965) , investigations demonstrating the recognition of potential symbionts hydra (Pardy and Muscatine, 1970, 1973), studies detailing the ultrastructural aspects of the animal-algal association (Pardy, unpublished) , and energetic evaluation of the symbiosis ( Stiven, 1965) , have all been possible due to the availability of aposymbiotic hydra. While the existence of free-living aposymbiotic hydra in nature is unreported, algal-free animals occasionally arise in laboratory cultures as a result of the chance occurrence of an algal-free zygote (Lenhoff, 1965) . Such aposymbiotic zygotes mature and by asexual budding, produce clones of white animals that do not normally become symbiotized in laboratory cultures. These aposymbionts, however, can be reinfected artificially with symbiotic algae (Pardy and Muscatine, 1973) and thus retain the capacity for symbiosis. The occurrence of algal-free zygotes, however, is at best an uncertain and capricious process. Moreover, the production of hydra by sexual processes gives rise to genetic recombinants which may not have the same physiological charac teristics as the asexually reproducing parent clone. Moore and Campbell (1973) have shown that inbred hydra give rise to zygotes that exhibit high mortality and that some zygotes exhibit morphological and developmental aberrations. The latter condition was first described by Lenhoff ( 1965) , who discovered a mutant strain of nonbudding hydra that was produced by sexual processes. Objections to the use of aposymbiotic hydra derived from algal-free zygotes described above are partly overcome by the production of aposymbiotic animals in the laboratory by chemically treating adult, green hydra. By means of a technique first described by Whitney (1907) , green hydra are maintained in 0.5% glycerine. After several days of exposure to glycerine, some animals become pale green to white. From some of the white animals, clones of aposymbiotic hydra can be reared by means of asexual budding. Using this method, investigators are able to prepare routinely algal-free animals that are genetically identical to their symbiotized progenitors. Glycerination has been used to produce aposymbiotic hydra
TL;DR: The oxygen transport system should be influenced by ionic changes in the blood, such as those which accompany the spring migrations into estuaries, and when Limulus enters dilute waters, blood NaCl is reduced by almost half, even though active hyperosmotic regulation occurs.
Abstract: 1. Oxygen affinity of Limulus hemocyanin is lowered by the addition of Cl-and raised by the addition of H+. Therefore the oxygen transport system should be influenced by ionic changes in the blood, such as those which accompany the spring migrations into estuaries.2. When Limulus enters dilute waters, blood NaCl is reduced by almost half, even though active hyperosmotic regulation occurs. At very low salinities, the excretory organ plays a role in the imperfect regulation of blood NaCl by forming a dilute urine.3. Unlike crustaceans, H+ concentration of blood changes very little at low salinity, because little additional NH3 is produced and no appreciable increase in H+ binding to molecular NH3 occurs. This response is believed to be related to the small role of free amino acids in intracellular osmotic adjustment.4. Blood PO2 decreases in low salinity as a result of bradycardia. While the oxygenation of hemocyanin at the gill does not change appreciably, deoxygenation at the tissues is enhanced and thus,...