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Showing papers in "The Biological Bulletin in 1975"


Journal ArticleDOI
TL;DR: It was concluded that larvae of Manduca simply continue to grow and molt until they reach or exceed a sharply defined threshold size (corresponding to a head capsule size of 5.1 mm), and the final larval instar during which the corpora allata will be...
Abstract: 1. Under standard laboratory rearing conditions, caterpillars of Manduca sexta invariably go through 5 larval instars before pupating.2. Evidence is presented that the head capsule width of a given instar is proportional to the weight that the individual had attained at the time that the molt to that instar occurred. Fifth-instar larvae with a large range of head capsule sizes were produced by temporarily starving 3rd and 4th instars, thus inducing them to molt at subnormal weights.3. Further observations on such larvae revealed that individuals with head capsules wider than 5.1 mm proceeded to pupate at the following molt whereas larvae with smaller head capsules underwent a supernumerary larval molt.4. It was concluded that larvae of Manduca simply continue to grow and molt until they reach or exceed a sharply defined threshold size (corresponding to a head capsule size of 5.1 mm). The instar in which this threshold size is attained is then the final larval instar during which the corpora allata will be...

313 citations


Journal ArticleDOI
TL;DR: The determination of JH titers in heniolymph during the fourth and fifth instars of wild-type Manduca larvae, by means of a sensitive and quantitative JH bioassay utilizing larvae of the black mutant, is described.
Abstract: The juvenile hormone (JH) , as with many other developmental hormones in insects, must reach its target tissues by way of the hemolymph. Thus, the hemolymph concentration bears an important relation to effects of JH ( see de Wilde, de Kort and de Loof, 1971 ) , although tissue retention of hormone or of “?�covert effects”of hormone may be of significance as well (e.g., Ohtaki, Milk man, and Williams, 1968 ; Nijhout, 1975). It is generally accepted that the JH titer is “?�high” during most of premetamorphic development, yet the effects of JH are made manifest only at discrete times during this development—when ecdysone induces a molt. Ligation studies of larvae of the tobacco hornworm Manduca sexta suggest that in a larval molt, the effects of JH on epidermal commitment occur simultaneously with initiation of the molting process by ecdysone (Truman, 1972 ; Truman and Riddiford, 1974) . Observations in these studies and in others (Wigglesworth, 1934 ; Fukuda, 1944) suggest indirectly that in premetamorphic molts the JH titer, in fact, may be very low at the time of prothoracicotropic hormone (PTTH) release, just prior to the critical period for ecdysone secretion. Other reports suggest that substantial titers of ecdysone and of JH do not occur simultaneously even in a larval molt (Patel and Madhavan, 1969). Much has been deduced about JH titers from indirect measurements of cyto logical, size, or activity changes in the corpora allata (CA) (see Doane, 1973), but there are difficulties with such methods (Williams, 1961; Johnson and Hill, 1973a) and direct determination of hemolymph titers is desirable. The tobacco horn worm is especially suited for such an investigation of hemolymph titers of JH during larval development. The “?�gating” of PTTH release by photoperiod (Tru nian, 1972) allows one to select developmentally synchronous groups of animals from which to obtain hemolymph for analysis. Titers observed can be correlated precisely with developmental events relative to the release of PTTH and ecdysone. Finally, the JH content of hemolymph samples can be analyzed in a bioassay system using assay animals of the sanie species and stage as those which provided the hemolymph. This report describes the determination of JH titers in heniolymph during the fourth and fifth instars of wild-type Manduca larvae, by means of a sensitive and quantitative JH bioassay utilizing larvae of the black mutant (Safranek and Riddi ford, 1975).

232 citations


Journal ArticleDOI
TL;DR: Feeding response exhibition in five marine crustaceans was observed in the presence of a range of concentrations of an amino acid mixture composed of equal parts DL alpha arnino-n-butyric acid, L-glutamic acid and taurine and Panulirus interruptus antennule receptors displayed a degree of specificity to mono- and dicarboxylic amino acids.
Abstract: 1. Feeding response exhibition in five marine crustaceans was observed in the presence of a range of concentrations of an amino acid mixture composed of equal parts DL alpha arnino-n-butyric acid, L-glutamic acid and taurine. Gnathophausiaingens, Pleuroncodes planipes, and Cancer antennarius displayed behavioral thresh olds of between 10-10 and 10-12 M; Spirontocaris taylori and Pagurus hirsutiusculus displayed thresholds between 10-7 and 10-9 M.2. Electrophysiological response thresholds to the amino acid mixture were examined in G. ingens and C. antennarius. The antennular and dactyl receptors of G. ingens displayed thresholds of 10-7 and 10-8 M respectively. Maxilliped and dactyl receptors of C. antennarius both displayed a threshold of 5 x 10-5 M.3. Panulirus interruptus antennule receptors displayed a degree of specificity to mono- and dicarboxylic amino acids.

112 citations


Journal ArticleDOI
TL;DR: Intracellular stores of dopamine and serotonin were found to be synthesized in the proper neuron and transported down the axon to the terminal varicosities and taken up by both kinds of nerve cells and by some other tissues.
Abstract: Monoamine localization was accomplished in Mytilus edulis by the use of histofluorescence. Intracellular stores of dopamine and serotonin were found to be synthesized in the proper neuron and transported down the axon to the terminal varicosities.Most of the cells in the cortex of the cerebral and visceral ganglia were non-fluorescent. Of the fluorescent cells, serotonin predominated in the cerebral ganglion and dopamine predominated in the visceral ganglion. There was a net flow of serotonin in the cerebro-visceral connective from the cerebral to the visceral ganglion and a net flow of dopamine in the opposite direction.Serotonin fluorescence was localized in intracellular granules in neurons and blood cells. Dopamine fluorescence was distributed homogenously in neurons and in the supporting rod of the gill. The visceral ganglion supplies the gill with nerve fibers of both types.Exogenously supplied serotonin and dopamine were taken up by both kinds of nerve cells and by some other tissues. Endogenous st...

96 citations


Journal ArticleDOI
TL;DR: The present contribution provides direct evidence for a rapid net influx of naturally occurring organic material and amino acids in two genera of the annelid infauna and stimulation of production of available organic compounds in sediments as a result of the presence and activity of the Annelid Infauna.
Abstract: Rapid, carrier-mediated influx of small organic molecules across the body wall of marine invertebrates has been studied by a number of investigators. Recent literature is reviewed by Stephens ( 1972) who interprets available evidence as supporting a net influx which is large enough in many instances to represent a significant supplement to the nutrition of the animals concerned. This interpre tation has been questioned by Johannes, Coward and Webb ( 1969) . These investi gators studied exchanges of amino acids between the flatworm, Bdelloura, and the environment and found a net efflux. Stephens and Schinske ( 1961 ) studied net exchanges of amino acids in a wide range of invertebrate material and reported a net influx. These results can be reconciled by noting the very different ambient concentrations used by the two sets of investigators and the relative insensitivity of efflux to changes in ambient concentration (as argued in Stephens, 1972) . How ever, this analysis is somewhat indirect since it is based on separate measurements of influx and efflux using labelled substrates. The present contribution provides direct evidence for a rapid net influx of naturally occurring organic material and amino acids in two genera of the annelid infauna. A fundamental gap in the literature concerning transepidermal uptake is the failure to establish any convincing link between this process and a quantitatively tenable source of available organic compounds in the environment. Speaking more generally, transepidermal uptake needs to be integrated into the general trophic structure of marine communities in order to aspire to a status other than that of an interesting curiosity of unknown significance. The present contribution also reports stimulation of production of available organic compounds in sediments as a result of the presence and activity of the annelid infauna. This represents the requiredlinkagebetweenuptakeandproduction andisan initial stepinthedesired integration of the process into the overall trophic structure of the community. This work was greatly faciliated by the introduction of a new reagent, fluores

90 citations


Journal ArticleDOI
TL;DR: Evidence is presented which suggests that the action of JH is mediated by long-lived covert effects and that these covert effects are swiftly eliminated toward the end of larval life, apparently through theaction of an unidentified blood-borne factor.
Abstract: 1. The half-life of endogenous juvenile hormone (JH) in the hemolymph of early 5th (final) instar larvae of Manduca sexta is approximately 25 minutes. Two hours after ligation JH is no longer detectable in isolated abdomens.2. The morphogenetic action of JH as well as its inhibitory action on the secretion of the prothoracicotropic hormone persist for several days after molecular JH has become undetectable in the hemolymph and in blood-free carcasses.3. Evidence is presented which suggests that the action of JH is mediated by long-lived covert effects and that these covert effects of JH are swiftly eliminated toward the end of larval life, apparently through the action of an unidentified blood-borne factor.4. Two contrasting hypotheses can explain the persistent covert effect of JH. One suggests that the covert effects are stable biochemical changes in the target tissues induced as a normal part of the molecular action of JH. Alternatively, it is possible that molecular JH persists in an unextractable for...

88 citations


Journal ArticleDOI
TL;DR: Little is known of the functional significance of the reduction of the midgut to four or six caeca and, in terrestrial species, of the subdivision of the hindgut and the development of a typhiosole, but it would seem likely that the latter modifications are related in some way to the terrestrial habit, probably as adaptations to the type of food available.
Abstract: The alimentary canal of isopod crustaceans is comparable to that of most other Arthropoda in that three basic regions can be recognized. These are the foregut, derived from the ectodermal stomodaeum and consisting of an oesophagus and pro ventriculus, the endodermal midgut, and an ectodermal hindgut derived from the proctodaeum (Goodrich, 1939) . The midgut, though, is unusual in that it is vir tually restricted to four or six simple caeca which arise at the junction of the fore- and hindgut. Controversy over whether any other part of the alimentary canal is of endodermal origin, and therefore to be regarded as midgut, has been resolved by Holdich ( 1973) who concludes from a comprehensive review of the literature that the discontinuity between the chitinous intimas of the fore- and hind gut described by Goodrich ( 1939), underlain in some species by a band of endo derm two to three cells wide, is the only remnant of a true midgut in isopods, other than the caeca. The terrestrial isopods show further modifications of the alimentary canal in that the hindgut is subdivided into an anterior somewhat expanded region, which bears along its length a dorsal typhiosole, a median papillate region, a muscular sphincter, and a short posterior rectum (Sutton, 1972). The histology and ultrastructure of the isopod gut is known from a consider able number of studies, summarized in Jones, Babbage and King (1969), Schmitz and Schultz (1969), Holdich and Ratcliffe (1970), Clifford and Witkus (1971) and Alikhan (1972). The caeca have received particular attention and most authors agree that they are the source of endogenous digestive enzymes which act on the food within the caecal lumen, the proventriculus, or the hindgut. The caeca are also concerned with absorption of digested food and in some instances are believed to carry on digestion intracellularly. Little is known, though, of the functional significance of the reduction of the midgut to four or six caeca and, in terrestrial species, of the subdivision of the hindgut and the development of a typhiosole. It would seem likely, however, that the latter modifications are related in some way to the terrestrial habit, probably as adaptations to the type of food available. The terrestrial isopods have a large proportion of cellulose in their diet, feeding on moist vegetable litter and often supplementing this by consuming their own, faeces (Wieser, 1966; Sutton, 1972). They show strong preferences for partly decomposed litter rich in the micro organisms which effect its decomposition (Edwards, 1974: Hassall, 1975a) and their gut modifications may well be adaptive features facilitating efficient utilization of this food, possibly by allowing the isopods to make extensive use of the cellulose degrading properties of the litter microflora. Endogenous cellulases are not corn

84 citations


Journal ArticleDOI
TL;DR: It is suggested that disconnection of the corpora allata from the brain partly removes their inhibition and induces secretion of a low titer of juvenile ho...
Abstract: 1. The implantation of three brains into freshly ecdysed last instar larvae which possess at least one of the two corpora allata induces extra larval development. Implanted brains appear to produce a neurohumoral allatotropic factor.2. Corpora allata seem to be inhibited via their nervous connections 48-60 hours after the last larval-larval ecdysis and become insensitive to the allatotropic factor. Severance of the nerves innervating the corpora allata and adjacent corpora cardiaca induces extra larval development in 7% of the experimental insects and restores sensitivity to the implanted brains in as many as 20%.3. Severance of the nerves to the corpora cardiaca—corpora allata complexes or implantation of corpora cardiaca—corpora allata complexes into allatectomized larvae in some instances causes a considerable prolongation of the last larval instar. It is suggested that disconnection of the corpora allata from the brain partly removes their inhibition and induces secretion of a low titer of juvenile ho...

83 citations


Journal ArticleDOI
TL;DR: An attempt is made to outline the sea water-plasma and plasma muscle steady states by comprehensive analyses of muscle and plasma of specimens of the spiny dogfish Squalus acanthias.
Abstract: Marine Research Laboratory, 0 ban, Scotland The blood plasma of elasmobranchs is isosmotic or slightly hyperosmotic to sea water, but ions account for only part of its osmotic concentration, a large fraction being made up by urea and trimethylamine oxide (Holmes and Donaldson, 1969). These nitrogenous compounds are also present in high concentration in muscle (Smith, 1929; Dyer, 1952). In this paper an attempt is made to outline the sea water-plasma and plasma muscle steady states by comprehensive analyses of muscle and plasma of specimens of the spiny dogfish Squalus acanthias. Measurements of osmotic concentration of plasma and muscle have been made and compared with the sum of analyzed constituents, values of the latter, first obtained as milligram-ion or niillimolar con centrations per kilogram solvent water, being converted to milliosmoles by the ap propriate osmotic coefficients. Imprecision arises here owing to lack of knowledge of some coefficients, and because of the possibility that some of the constituents may be bound to protein, exerting little osmotic effect. Some idea of the amount of ion binding in muscle has been obtained by analyses of the juice expressed from muscle by a tissue press or obtained by ultracentrifugation. Estimates have also been made of the extracellular space in muscle, thus enabling intracellular concentrations to be calculated. MATERIALS AND @IETHODS Specimens of Squalus acanthias were caught by trawl in the Firth of Clyde and were kept in tanks of flowing sea water. Salinity during several summer periods varied from 32.2—33.4%@ ( 18.20—18.88g Cl/liter) with temperatures of 9—12° C. After stunning the fish, blood was withdrawn by syringe or pipette under liquid paraffin from the heart and placed in centrifuge tubes kept in a beaker of crushed ice. After centrifugation, the plasma, still under paraffin, was removed and used for analysis. Samples of white parietal muscle were taken from the dorsal and lateral region of the tail just behind the second dorsal fin (epaxial muscles) . After light blotting with filter paper, separate samples were used for cations (ashing at 5500 C in the presence of sulphuric acid) , determination of dry weight and the preparation of trichloroacetic extracts, tungstic acid extracts and zinc hydroxide extracts. Methods for the analysis of Na, K, Ca, Cl and SO4 of muscle and plasma were essentially those of Robertson (1949, 1960) with appropriate modifications for the lower concentration of ions in elasmobranchs. Magnesium was estimated by Heagy's (1948) method. Some of the analyses for Ca were done by atomic absorp tion spectrophotometry; interference by phosphate in the Ca estimation of muscle 303

81 citations


Journal ArticleDOI
TL;DR: Characteristics of cyclic breathing movements have been examined in a number of fish species at rest and during swimming acceleration to velocities above those sufficient to induce transfers from active to passive gill ventilation (ram gills ventilation).
Abstract: 1. Characteristics of cyclic breathing movements have been examined in a number of fish species at rest and during swimming acceleration to velocities above those sufficient to induce transfers from active to passive gill ventilation (ram gill ventilation). They were trained to swim in one of several types of swimming tunnels after electrode implants to permit recording of ECG's and ventilatory muscle EMG's.2. Transfer to the ram mode of gill breathing is marked by a drop-out of individual cyclic breathing movements as swimming increases from rest. When the swimming speed reaches about 65 cm· sec-1, most fish that use ram gill ventilation complete conversion to the ram mode (35 to 82 cm·sec-1, range of all fish tested). This is equivalent to an across-gill differential pressure of 2.1 cm H2O as measured with a combined impact-reverse pitot tube as an approximate model. Generally, a fish must be swimming to ram gill ventilate, but some exceptions are noted such as the shark-riding remoras.3. Control of the...

78 citations


Journal ArticleDOI
TL;DR: Differences in predation pressure and prey tissue utilization efficiency are proposed as factors influencing the evolution of a significantly faster generation time in Phestilla sibogae than in the closely related P. melanobranchia.
Abstract: 1. The complete life cycles of two coral-eating aeolid nudibranchs, Phestilla melanobranchia Bergh, 1874 and Phestilla sibogae Bergh, 1905, are described. Information on their life histories includes developmental stages and timing, duration of the veliger stage, veliger behavior, factors necessary for settling and metamorphosis, and adult growth rates, fecundity and longevity. The life cycles of the two Phestilla are similar and their physical and behavioral differences are related to the characteristics of their respective coral prey. 2. P. melanobranchia has planktotrophic development, is negatively phototactic when ready to settle, requires close proximity to living dendrophylliid coral tissue for metamorphosis and has a generation time from egg to egg of 60 days. The dendrophylliid corals on which P. melanobranchia feeds are small, patchy and photonegative in distribution. 3. P. sibogae which has now been under serial cultivation for four years, has lecithotrophic development, is positively phototactic when ready to settle, requires only a chemical factor from living Porites tissue for metamorphosing and has a generation time of 38 days. The Porites corals which P. sibogae feeds on are large, very common and photopositive in distribution. 4. Differences in predation pressure and prey tissue utilization efficiency are proposed as factors influencing the evolution of a significantly faster generation time in Phestilla sibogae than in the closely related P. melanobranchia.

Journal ArticleDOI
TL;DR: The effects of various photoperiod-temperature regimes on gonadal activity in the cyprinid teleost, Notemigonus crysoleucas, were examined during several different phases of the annual reproductive cycle.
Abstract: 1. The effects of various photoperiod-temperature regimes on gonadal activity in the cyprinid teleost, Notemigonus crysoleucas, were examined during several different phases of the annual reproductive cycle.2. Regardless of the time of year when the experiment is initiated a long photoperiod-warm temperature regime stimulates gonadal development to the prespawning condition or induces spawning. Neither a warm temperature alone nor a long photoperiod alone will stimulate final gonadal maturation.3. Notemigonus is not "refractory" to long photoperiod-warm temperature gonadal activation during the postspawning season.4. Short photoperiods in combination with warm temperatures cause gonadal regression in this species. A low temperature-short photoperiod regime does not induce gonadal involution.5. Spermatocyte formation and proliferation as well as the early phases of vitellogenesis occur independently of environmental factors. Final gonadal maturation and the rate of gametogenesis, however, depend on specifi...

Journal ArticleDOI
TL;DR: Gametogenesis proceeds in characteristic fashion, although oogenesis is accompanied by the formation of a trophonema between the oocyte and edge of the mesentery, and attached juveniles are capable of capturing prey.
Abstract: 1. Epiactis prolifera is a gynodioecious hermaphrodite, most of the intermediate-size individuals being female and most of the larger ones hermaphroditic. The population studied lacked purely male individuals.2. Fertile animals may be found not brooding young, but all brooding individuals examined were fertile. Both females and hermaphrodites brood.3. Gametogenesis proceeds in characteristic fashion, although oogenesis is accompanied by the formation of a trophonema between the oocyte and edge of the mesentery. All stages of both types of gametes were present throughout the year.4. The zygotic nucleus divides a number of times and the resulting nuclei segregate into two layers before cytokinesis occurs. Mesenteries form while endodermal cells are still yolk-laden, and before it is all absorbed, tentacles with functional nematocysts and gland cells develop. Thus attached juveniles are capable of capturing prey.5. Mucus and perhaps nematocysts, both of parental origin, are probably responsible for adhesion ...

Journal ArticleDOI
TL;DR: The annual reproductive cycle of the Palos Verdes (Southern California) subtidal population of S. purpuratus correlates with seasonal changes in ocean temperature: a rise of temperature above 17° C (June) coincides with cessation of gamete production and storage.
Abstract: 1. The annual reproductive cycle of the Palos Verdes (Southern California) subtidal population of S. purpuratus correlates with seasonal changes in ocean temperature: a rise of temperature above 17° C (June) coincides with cessation of gamete production and storage.2. Sea urchins maintained at low temperature (13° C) retained gametes nearly two months (as long as they were observed) beyond the date when the field population had "apawned out."3. At a time when the field population was reproductively active, the spawning capability of a laboratory population was terminated by three weeks of warm water temperature(19° C).4. The spawning capability of animals kept at 13° C was not terminated by long-day photoperiod (14L:10D).5. The onset of reproductive activity in animals started during the summer months could not be accelerated experimentally by 10 weeks of low temperature (13° C).6. In laboratory animals maintained at 13° C, the onset of reproductive activity was neither enhanced by short-day (10L:14D), no...


Journal ArticleDOI
TL;DR: The skin covering the tail and hinder trunk region of Oikopleura propagates impulses at 15-21 cm/sec and in general resemble skin impulses in hydromedusae more than those of amphibian and tunicate tadpole larvae.
Abstract: The skin covering the tail and hinder trunk region of Oikopleura propagates impulses at 15-21 cm/sec. Spread is non-decremental and unpolarized. The impulses are of short duration (8-12 msec) and in general resemble skin impulses in hydromedusae more than those of amphibian and tunicate tadpole larvae.The skin was examined by optical and electron microscopy. The cells are connected by gap junctions. Impulses are assumed to spread by direct current flow from cell to cell.Electromyograms of tail activity during three behavior patterns (pumping, swimming, and house rudiment expansion) are analyzed in relation to neuromuscular histology. There appear to be at least two classes of pacemakers, both located in the caudal ganglion. There is no evidence that proprioceptive feedback is required for maintenance of rhythmic activity; and isolation of the tail from the trunk, which contains the cerebral ganglion, does not affect rhythmicity. The system differs fundamentally from the locomotory systems of Amphioxus and...

Journal ArticleDOI
TL;DR: The shell-forming mantle tissue attained a steady state with respect to 45Ca in the sea water medium within 2 hours and the molar ratio of 45Ca to 14C-carbonate deposited in shell was not significantly different from unity during 5 hours.
Abstract: 1. Incorporation of calcium and carbonate into shell has been studied in the scallop Argopecten irradians using 45Ca and 14C-bicarbonate. 2. The incorporation of 45Ca and 14C-carbonate into shell was linear with time after a lag period of 1 to 2 hours. The shell-forming mantle tissue attained a steady state with respect to 45Ca in the sea water medium within 2 hours. 3. The molar ratio of 45Ca to 14C-carbonate deposited in shell was not significantly different from unity during 5 hours. 4. The rate of incorporation of 14C-carbonate into shell was highest at the ventral edge and extremely low in the central and hinge areas. 5. The rate of incorporation at the ventral shell edge did not change with increase in shell size. 6. The rate of incorporation of carbonate was low at night when growth ridges form and increased 3-fold at midday when growth ridges are not being formed. 7. The protein content of the shell ridges was 32.9 ± 3.9% and the protein content of the shell including ridges was 16.0 ± 2.1%.

Journal ArticleDOI
TL;DR: There were repeatable and significant differences in tolerance between populations collected in March and August and also between salinities and the proportional variance between populations, using the index, was increased over TS and TR.
Abstract: 1. Thermal tolerances of populations of Eurytemora affinis were measured using two basic methods, at various salinities with and without acclimation. Little distinction in tolerances was made using temperature of inactivation. A more useful assay was temperature shocking at 34.5° C, observing time to succumb (TS) and time to recover (TR) over a 30 minute period.2. Using the shock-recovery assay, there were repeatable and significant differences in tolerance between populations collected in March and August and also between salinities. Average tolerances and differences between populations generally increased with salinity.3. The distinction between populations in thermal tolerance was greater when the animals were osmotically acclimated for 24 hours.4. A simple index of tolerance combining TS and TR was suggested. In most cases the proportional variance between populations, using the index, was increased over TS and TR.5. The seasonal distribution of E. affinis is contrary to that expected from the therma...

Journal ArticleDOI
TL;DR: The investigation of the possibility of an analogous effect of temperature on the kinetics of amino acid uptake is clearly indicated and this approach has been taken in the present study of Aurelia aitrita polyps (scyphistomae) using dissolved glycine.
Abstract: During the last decade there has been a considerable renewal of interest in the uptake of dissolved organic matter (especially amino acids) by marine in vertebrates. Among the goals of these investigations is the elucidation of the importance of dissolved free amino acids to the nutrition of these animals (for recent reviews and bibliographies, see : Johannes, Coward and Webb, 1969; Stephens, 1972 ; Dixit, 1973 ; Schlichter, 1973) . Most experiments attempting to demonstrate a nutritive role of these substances have utilized well fed animals presumably having high levels of metabolic substrates, although a priori, it is in the starved animal that one might expect a significant supplemental nutritional contribution by dissolved compounds. There appears to be very little direct evidence supporting the hypothesis that dissolved amino acids (at environmentally realistic concentrations) are in fact an energy source for marine invertebrates. Stephens ( 1967) has pointed out that not all of the assimilated material is necessarily oxidized. but that it may also exert a sparing effect on a variety of metabolic pathways and on growth and re productive processes. This implies that there need not necessarily be a net uptake of these compounds for them to be nutritionally significant. In the absence of data regarding the total flux of amino acids, an alternative course of investigation is to make qualitative and quantitative comparisons of biochemical, physiological and developmental processes among fed, starved and starved/amino acid-exposed animals. It is this approach that has been taken in the present study of Aurelia aitrita polyps (scyphistomae) using dissolved glycine. The uptake of dissolved free amino acids generally follows Michaelis-Menten kinetics, and while this does not necessarily imply that the uptake process is enzyme-mediated, the calculation of the kinetic constant K@permits comparisons of the affinities of the amino acid uptake systems among different groups of ani mals. To date, the K@values reported for marine invertebrates have been dis cussed almost exclusively in terms of the animals' adaptations to the concentra tions of dissolved free amino acids in their respective habitats (Southward and Southward, 1972a, 1972b; Stephens, 1972), although an additional consideration has been demonstrated by Dixit (1973), who found ontogenetic differences in K@for glycine uptake by a sea urchin. In view of the known influence of tem perature on enzyme kinetics in poikilotherms (Hochachka and Somero, 1973), the investigation of the possibility of an analogous effect of temperature on the kinetics of amino acid uptake is clearly indicated.

Journal ArticleDOI
TL;DR: The larval development of Pseudopolydora paucibranchiata and P. kempi (Southern) is described, both species occur in tidal flats of California bays and estuaries.
Abstract: 1. The larval development of Pseudopolydora paucibranchiata (Okuda) and P. kempi (Southern) is described. Both species occur in tidal flats of California bays and estuaries. 2. Adult females of P. paucibranchiata deposit eggs in capsules which are attached to the inner lining of their tubes. All eggs are fertilized. Larvae develop in the capsules until they have 3 setigerous segments at which time they enter the plankton. After development of 13-17 setigers they begin to settle out of the plankton and assume a benthic life. 3. Eggs of P. kempi are also deposited in capsules, but in this case only a small percentage are fertilized. The unfertilized eggs fragment into separate yolk granules and are eaten by the developing embryos. After all yolk is devoured the larvae continue their development sustained by this stored food reserve. They remain in the capsule until they have about 15 setigers. They remain in the plankton only a short time before settling and taking up a benthic life.

Journal ArticleDOI
TL;DR: 1. Feeding in the medusa of Proboscidactyla flavicirrata is accompanied by local, small amplitude impulses recorded from the bases of perradial tentacles, which are the electrical accompaniment to local tentacle contraction.
Abstract: 1. Feeding in the medusa of Proboscidactyla flavicirrata is accompanied by local, small amplitude impulses recorded from the bases of perradial tentacles.2. Medusae, both attached and free, swim spontaneously with electrodes in place thus giving data on the temporal patterns of contractions of the swimming muscle.3. Swimming pulses (SP's) can be recorded from the circular muscle of the subumbrella. Each SP is preceded by a pre-swim pulse (PSP) which is a neuronal pulse conducted in the marginal nerve(s).4. Marginal pulses (MP's) are neuronal pulses conducted in the marginal nerve(s) which can trigger synchronous tentacle contraction.5. MP's originate from pacemaker sites located in tentacle bulbs. When new tentacles first appear the firing of MP's from these new sites is not synchronized with established pacemakers: eventually they become linked to the original pacemaker system.6. Synchrony between MP pacemakers is lost under Mg++ anaesthesia.7. Tentacle contraction pulses (TCP's) are the electrical accom...

Journal ArticleDOI
TL;DR: The observed rate at which N. obsoletus veligers leave their egg capsules is shown to be in close agreement with the rate predicted from an equation assuming random movements of individuals within the capsules.
Abstract: 1. The loosening of the egg capsule plug prior to escape of the veligers is shown to be chemically mediated in Nassarius obsoletus and N. trivittatus. 2. The hatching substance is not produced continuously during development, but rather in a short pulse beginning just prior to hatching and ending within 4 hours of escaping from the capsule, for N. obsoletus. 3. The hatching substance produced by the embryos of one species is effective only on the capsule plugs of that species, for the two species studied. 4. The substance is functionally short-lived, at room temperature in sea water, losing its potency within three hours after its secretion by N. obsoletus. 5. The observed rate at which N. obsoletus veligers leave their egg capsules is shown to be in close agreement with the rate predicted from an equation assuming random movements of individuals within the capsules.

Journal ArticleDOI
TL;DR: The entire process of development in the sea-star, Astropecten latespinosus, is reported, especially with regard here to the external morphology and the skeletal system, with special reference to the type of development of sea-stars.
Abstract: 1. The entire process of development in the sea-star, Astropecten latespinosus, is reported, especially with regard here to the external morphology and the skeletal system.2. The eggs are medium-sized, about 300 µ in diameter. They develop into free-swimming larvae through a wrinkled blastula stage by holoblastic, radial cleavage.3. The free-swimming larva has a peculiar barrel shape, being neither bipinnaria nor brachiolaria. Such a larva has not previously been reported.4. Metamorphosis takes place while the larva is pelagic, and there is no feeding at this stage. Five days after insemination, metamorphosis is completed and the resulting juveniles bear 2 pairs of tube-feet and a terminal tentacle in each arm.5. The present observations are compared with those studied by other workers, and are discussed, with special reference to the type of development of sea-stars.

Journal ArticleDOI
TL;DR: The rate of respiration of the sea urchin Strongylocentrotus purpuratus measured with an oxygen electrode parallels but is somewhat lower than that determined manometrically on the same individuals under the same conditions, indicating the change in oxygen consumption during the reproductive cycle.
Abstract: 1. The rate of respiration (Qo2) of the sea urchin Strongylocentrotus purpuratus measured with an oxygen electrode parallels but is somewhat lower than that determined manometrically on the same individuals under the same conditions. The higher values of the Qo2 obtained manometrically are attributable to the higher partial pressure of oxygen (ppO2) in the fluid of the manometric vessels continuously equilibrated with air as compared to the closed chamber used with the oxygen electrode, in which the ppO2 is continuously falling.2. The effects of a number of factors on Qo2 were determined: ppO2 (including oxygen enrichment), relation between ambient oxygen partial pressure (AO2), perivisceral oxygen partial pressure (PvfO2) and effect of body size on Qo2, oxygen consumption of isolated and intact body wall; and the main thrust of this investigation—the change in oxygen consumption during the reproductive cycle.3. The sea urchin is an oxygen conformer, its oxygen consumption being dependent upon the oxygen ...

Journal ArticleDOI
TL;DR: It is shown that hard clam reproductive cycles in Delaware Bay are in phase and that spawning activity during 1971-1973 was of sufficient intensity to provide ample larval stocks and supporting evidence that different physiological races exist in the three areas compared.
Abstract: 1. This study has shown that hard clam reproductive cycles in Delaware Bay are in phase and that spawning activity during 1971-1973 was of sufficient intensity to provide ample larval stocks.2. The gonad developmental patterns for clams in Delaware are intermediate between those for Long Island and North Carolina. The data provide supporting evidence that different physiological races exist in the three areas compared. A further test on the validity of physiological races could be determined by studying the developmental patterns of Long Island and North Carolina clams held experimentally in Delaware Bay.3. Environmental factors attribute to subtle differences in reproductive physiology as evidenced by the different mechanisms of regeneration and development between Delaware Bay and Henlopen hard clam females.The authors wish to thank Dr. Melbourne R. Carriker, Dr. R. W. Menzel, Dr. L. Watling, Mr. Hugh Porter for critical review of the manuscript, and Dr. Jonathan Taylor and Ms. Ann Taylor who provided p...

Journal ArticleDOI
TL;DR: It is suggested that larvae of L. floridanus may swim at their capacity at low light intensities, in contrast to larvae of P. herbstii, whose phototaxis responses were determined to have dominated that of gravity in the first zoea stage.
Abstract: 1. Experiments were conducted to determine the phototaxis responses of each larval stage of two species of Xanthid crabs and to assess the influence of light on depth regulation.2. Two primary orientations in response to light are described.3. Secondary orientation in response to light results in positive phototaxis in all four zoea stages and the megalopa of each species.4. In response to changes in light intensity, the first zoea stage of P. herbstii demonstrated high photokinesis. Although some increase in swimming rate in response to increased light intensity was noted in larvae of L. floridanus, particularly in the first zoea stage, the differences were not statistically significant. It is suggested that larvae of L. floridanus may swim at their capacity at low light intensities, in contrast to larvae of P. herbstii.5. Light response dominates that of gravity in the first zoea stage; in the megalopa, gravity response dominates that of light in a majority of individuals.6. Light aimed down the axis of...

Journal ArticleDOI
TL;DR: Comparisons of tropical and temperate echinoid oxygen consumption rates reveal that, when animals of similar size are compared, the Qo2 of the tropical forms is similar to that of their temperate counterparts.
Abstract: 1. "Whole body oxygen consumption data are determined for a variety of echinoid, asteroid and holothuroid species, and for one ophiuroid and one crinoid.2. Comparisons of tropical and temperate asteroids indicate no correlation of oxygen consumption rate with environmental temperature among the individuals tested. As is the case for echinoids. body size appears to be an important factor in determining the Qo2 of a particular species.3. Whole body oxygen consumption data are determined for several temperate and tropical echinoid species, and for a deep-water echinoid of the Pacific Coast.4. A comparison of respiratory physiology in S. purpuratus and A. fragilis is made, with particular attention to the body wall and gonad indices.5. Comparisons of tropical and temperate echinoid oxygen consumption rates reveal that, when animals of similar size are compared, the Qo2 of the tropical forms is similar to that of their temperate counterparts.6. The generally smaller body size of the tropical species tested res...

Journal ArticleDOI
TL;DR: Sigmoid growth curves resulted when either length or segment-formation was used as an indicator of growth among laboratory-reared worms.
Abstract: The nereid polychaete Laeonereis culveri (Webster) reproduces in the atokal condition in the Mystic River Estuary, Connecticut. Females spawn demersal eggs, 135-162 µ in diameter, that do not extrude a jelly layer upon fertilization and that give rise to unciliated embryos. Embryogenesis leads directly to a 3-setigen larva in four days (at 22 ± 3° C; 30‰). The trochophore is suppressed due to the retarded development of locomotory cilia which do not appear until the 3-setiger larva has formed. Although provided with ciliary tracts and capable of swimming, L. culveri larvae are normally benthic in habit. They reside in burrows within the upper 2 cm of fine, flocculent sediments where they feed chiefly on benthic diatoms until developing past the 5-setiger stage after which they become non-selective deposit feeders. The primary function of the larval ciliature is to pass water currents through the burrow. In the laboratory, 3-to 5-setiger larvae alternately swim and crawl in the absence of sediments on in the presence of coarse sediments (particle diameters > 250 µ); but they readily burrow into and remain within fine sediments (particle diameters < 250 µ) even if the latter are relatively free of organic matter. Swim-crawl behavior also appears to be elicited under conditions of unfavorable water quality. When the sixth setiger forms, the larva is no longer capable of swimming by means of its cilia. Development beyond the 3-setger stage approximates that of other species except that L. culveri larvae are apparently unique in ultimately developing eight nototrochs (one per each of the first eight trunk segments). The nototrochs are retained and function in burrow ventilation until the 16-to 18-setiger stages when body undulations commence creating ventilation currents. Larval development is completed with addition of the eighth trunk segment. At this stage, the tentacular segment (first trunk segment) is incorporated into the peristomium and the first pair of parapodia are modified to form the posterodorsal tentacular cirri. Sigmoid growth curves resulted when either length or segment-formation was used as an indicator of growth among laboratory-reared worms. Sexually mature, laboratory-reared worms were only about one-half the length of sexually mature worms in a natural population. Thirty-two individuals (17 females, 15 males) of an F1 generation were reared to maturity and spawned after 168-198 days of development. F2 generation larvae were identical in morphology to those of the F1 generation.

Journal ArticleDOI
TL;DR: It is very likely that the zoospore identified in pellets extruded by the actinian host is an infective stage in the life history of the zooxanthella, and there is some evidence to suggest that indirect infection of hosts by Zooxanthellae is also possible.
Abstract: 1. Various morphological stages in the life history of the zooxanthella symbiotic with Aiptasia tagetes have been identified in pellets extruded by the actinian host. One of the stages is a motile zoospore.2. This zoospore resembles that observed by Kawaguti (1944) and differs from those identified in axenic cultures of G. microadriaticum in containing a large accumulation body. Suggestions are made as to the significance of this difference.3. It is very likely that the zoospore is an infective stage in the life history of the zooxanthella.4. There is some evidence to suggest that indirect infection of hosts by zooxanthellae is also possible.

Journal ArticleDOI
TL;DR: The ecological data presented in this paper supports a synonymy between M. lugubris and Illinobdella moorei, the first record of a fish leech utilizing both a fish and an arthropod in its life history.
Abstract: A cyclic seasonal abundance for fish leeches has been reported by Gibson and Tong (1969) and Sawyer and Hammond (1973). Fish leeches leave their hosts to deposit cocoons on rocks (Becker and Katz, 1965), oyster clumps, and other suitable surfaces (Sawyer and Hammond, 1973). From the present work it ap pears that the piscicolid Myzobdella lugubris is parasitic on a piscine host for most of the year and then leaves the fish and deposits cocoons on decapods. This is the first record of a fish leech utilizing both a fish and an arthropod in its life history. Myzobdella lugubris Leidy 1851 and Illinobdella nioorei Meyer 1940 have until recently been separated primarily on the basis of salinity and host. Myzob della lugubris was known as a marine leech commensal on crustaceans (Hutton and Sogandares-Bernal, 1959; Pearse; 1936; Sawyer, 1967; Wurtz and Roback, 1955), and Illinobdella moorei as a freshwater leech parasitic on fishes (Hoffman, 1967). Sawyer, Lawler and Overstreet (1974) have recently synonymized these two forms with M. lugubris taking precedence. The ecological data presented in this paper supports such a synonymy.