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Showing papers in "The Biological Bulletin in 1986"


Journal ArticleDOI
TL;DR: Revue sur les interactions sexuelles et les phenomenes de reconnaissance cellulaire chez les Algues vertes et Phacophycophyta marine.
Abstract: Revue sur les interactions sexuelles et les phenomenes de reconnaissance cellulaire chez les Algues vertes et Phacophycophyta marine

188 citations


Journal ArticleDOI
TL;DR: Native aggregation level and subunit composition of the hemocyanins from 86 adult chelicerates and crustaceans, and from the larval stages of 2 crabs, were analyzed by means of electron microscopy, polyacrylamide electrophoresis, immuno blotting, and crossed immunoelectrophoresIs, supported by a variety of preparative separation techniques.
Abstract: Native aggregation level and subunit composition of the hemocyanins from 86 adult chelicerates and crustaceans, and from the larval stages of 2 crabs, were analyzed by means of electron microscopy, polyacrylamide electrophoresis, immuno blotting, and crossed immunoelectrophoresis, supported by a variety of preparative separation techniques. The up to eight immunologically discernible subunit types were interspecifically correlated, classified, and evolution lines derived. Phylogenetic consequences are discussed, and are particularly aggravating in spiders.A single subunit suffices for the formation of hexamers (1 x 6). In the architecture of higher-ordered hemocyanins, the various subunits act as building-blocks of distinct specification. This was studied in 2 x 6 molecules from a hunting spider and several crustaceans, and in 4 x 6 hemocyanin from a tarantula. The various subunits are present in constant proportions. The total set is required to reorganize the original aggregate from subunit mixtures. St...

169 citations


Journal ArticleDOI
TL;DR: Sulfideentering the blood in Riflia and Ca!yptogenamay be bound by sulfide-binding factors that transportsulfide to the symbionts and protect against sulfide inhibition ofaerobic respiration [via effects on the cytochrome-c oxidase (CytOx) system].
Abstract: The detoxification and metabolism of sulfide were studied in three symbiont containing invertebrates from the deep-sea hydrothermal vents: the tube worm, R@ftia pachyptila; the clam, Ca!yptogena nwgn@fica; and the mussel, Bathymodiolus ther mophilus. Sulfide oxidizing activities, due to specific sulfide oxidase enzymes, were found in all tissues, with the greatestactivities occurringin the symbiont-contaiing tissues:the trophosome ofthe tube worm and the gills ofthe bivalves. Sulfideoxidase activity was correlated with the bacterial content of the tissues. The sulfide oxidases in the outer cell layer(s)ofsymbiont-free tissues, e.g., body wall muscle ofRzfiia and foot and mantle of the bivalves, may detoxify sulfide as soon as it enters the body. Sulfideenteringthe blood in Riflia and Ca!yptogenamay be bound by sulfide-binding factors that transportsulfide to the symbionts and protect against sulfide inhibition ofaerobic respiration [via effects on the cytochrome-c oxidase (CytOx) system]. Sulfide strongly inhibited the CytOx systems of these animals, but this inhibition was offset by the additionto the CytOxassaymixtureofblood ofRj/iia or Ca!yptogena.Reduced sulfur compounds, sulfide, sulfite, and thiosulfate, were effective in stimulating ATP synthesis in homogenates of symbiont-containingtissues. The most effective reduced sulfur compound varied among the three symbioses.

168 citations


Journal ArticleDOI
TL;DR: The ability of K+ to directly influence cell membrane potential is proposed as an explanation for its broad effectiveness as a metamorphic inducer for larvae that recruit to different habitats.
Abstract: An increase in the concentration of K@in defined seawater medium induces settlement and metamorphosis in larvae of the marine molluscs Phestilla sibogae, Haliotis rufescens, and Astraea undosa, and in larvae of the marine annelid Phrag matopoma californica. The effect is dose-dependent, optimal at approximately double the normal concentration of K@in seawater, and specific for the K@ion. The ability of K@to directly influence cell membrane potential is proposed as an explanation for its broad effectiveness as a metamorphic inducer for larvae that recruit to different habitats. Depolarization ofexternally accessible, excitable cells thus is suggested to be a mechanism common to the induction ofsettlement and metamorphosis ofa number ofspecies. For Phestilla and Haliotis, the inductive effect ofexcess K@is additive with that of the substratum-derived inducers or analogs. The sensitivity of induction by K@ to external tetraethylammonium (TEA, a K@-channelblocker) reported previously for Haliotis (Baloun and Morse, 1984) is not present in Phestilla or Phragmatopoma. Results presented here indicate that the addition of excess K@may provide a widely useful technique for inducing metamorphosis, and for analyzing the mechanisms which govern this process, in other marine invertebrate larvae.

143 citations


Journal ArticleDOI
TL;DR: At an intertidal study site in southern California the daily settlement of barnacle cyprids was followed during the summer of 1983, and the pattern of settle ment is nearly identical to that of the megalopa of an interTidal crab, Pachygrapsus crassipes, and this suggests that, like these megalopae, cyprid may be transported onshore in slicks over tidally forced internal waves.
Abstract: At an intertidal study site in southern California the daily settlement of barnacle cyprids (probably Chthama/us spp.) was followed during the summer of 1983. Daily settlement was not significantly cross correlated with wind speed or direction but was significantly cross correlated with the maximum daily tidal range at lags of +1 to +4 days; peak settling occurred several days before the spring tide. This pattern of settle ment is nearly identical to that of the megalopa of an intertidal crab, Pachygrapsus crassipes, and this suggests that, like these megalopae, cyprids may be transported onshore in slicks over tidally forced internal waves.

128 citations


Journal ArticleDOI
TL;DR: In the spring, horseshoe crabs along the eastern coast of North America migrate toward shore to build nests close to the water's edge, and in 1984 the mating season near Woods Hole, Massachusetts, extended from 14 May to 7 July.
Abstract: In the spring, horseshoe crabs (Limulus polyphemus) along the eastern coast of North America migrate toward shore to build nests close to the water's edge. In 1984 the mating season near Woods Hole, Massachusetts, extended from 14 May to 7 July. Mating activity during this period fluctuated with the phase of the moon, the height of the tide, and diurnal changes in daylight. As the moon approached new and full phases, large numbers of animals migrated into the intertidal zone to mate and build nests. They appeared 1-2 h before high tide, and returned to deep water about 2 h after high tide. No mating activity occurred during low tides. The two daily high tides in this region are unequal in height. The inequality is greatest during new and full moons. At these times most animals migrated toward shore on the higher tide, which occurred in the late afternoon and throughout the night. As the moon passed through quadrature the tidal inequality diminished and reversed. Mating activity changed accordingly: shore ...

123 citations


Journal ArticleDOI
TL;DR: A population of Thor manningi sampled for one year was composed of 50% primary males, 49% protandric hermaphrodites, and 1% primary females, with average life spans of approximately 4-5 months.
Abstract: A population of Thor manningi sampled for one year was composed of 50% primary males, 49% protandric hermaphrodites, and 1% primary females. Primary males have prehensile third pereiopods, massive appendices masculinae, and life-long sperm production. Protandric hermaphrodites pass first through a male phase (non-prehensile third pereiopods, small appendices masculinae, sperm production) and a transitional phase (reduction of appendices masculinae and sperm ducts, development of female incubatory flanges, ovarian development) before maturing into breeding (embryocarrying) females.Eighty-six to 100% of females (female-phase hermaphrodites and primary females) in monthly samples carried embryos. Breeding females produced new embryo clutches approximately every nine days. Although reproduction was continuous, recruitment chiefly occurred in the summer. Measurements of density, size-specific dry weight, and cohort analysis indicate average life spans of approximately 4-5 months, production of 35 mg dry weight...

116 citations


Journal ArticleDOI
TL;DR: In Phase II, Botryllus growth rates and survivorships in seven of the eight laboratory treatments were better than those of marina colonies, whereas none of the marinacolonies produced eggs during Phase II.
Abstract: Growth and sexual maturity were compared among Monterey Botryllus schiosseri colonies cultured in the laboratory and in Monterey Marina in two separate studies: Phase I—Aprilto July 1984, a time when Botryllus growth is rapid in the field, and Phase Il—December 1984to March 1985, a time when growth is minimal in the field. Laboratory colonies were kept in tanks of standing. aerated filtered seawater at 15°C, 20°C,and 24°C;the seawater was changed daily or on alternate days. Food types were two concentrations of an algal mixture and five concentrations of Liquifry, a commercially availablefood for filter-feedingmarine invertebrates.All algae-fedcol onies did poorly. During Phase I, the colonies kept in Monterey Marinagrew much faster than those in the laboratory, but they took longer to reach sexual maturity than the Liquifry-fedcolonies grown at 20°C and had a lower survivorship.In Phase II, Botryllusgrowth ratesand survivorshipsin sevenof the eight laboratory treatments were better than those ofmarina colonies. These laboratory treatments yielded a sub stantial proportionof sexually maturecolonies, whereasnone of the marinacolonies produced eggs during Phase II.

103 citations


Journal ArticleDOI
TL;DR: The vanadium, iron, and manganese contents of 15 species of solitary ascidians belonging to the suborders Phlebobranchia and StolidobranchIA were determined by thermal neutron activation analysis.
Abstract: The vanadium, iron, and manganese contents of 15 species of solitary ascidians belonging to the suborders Phlebobranchia and Stolidobranchia were determined by thermal neutron activation analysis. Vanadium was detectable in all species examined. In general, the vanadium content in various tissues of the Phlebobranchia was considerably higher than the iron and manganese contents. The blood cells especially contained a large amount of vanadium. The highest value (21 µg vanadium/mg dry weight) was obtained from blood corpuscles of Ascidia ahodori. Species in the suborder Stolidobranchia, on the other hand, had smaller quantities of vanadium in comparison with those in the suborder Phlebobranchia. The iron and manganese contents did not differ greatly between the two suborders. The data are considered in the light of physiological roles of these transition metals in ascidians.

103 citations


Journal ArticleDOI
TL;DR: American oysters, Crassostrea virginica, from a high-salinity(HS) and a low- salinity (LS) location in the Chesapeake Bay were acclimated to six salinities in the laboratory for 3-4 weeks and hemolymph was drawn from oysters and granular hemocytes were tested in vitro.
Abstract: American oysters, Crassostrea virginica, from a high-salinity(HS) and a low-salinity (LS) location in the Chesapeake Bay were acclimated to six salinities (6-36 ppt) in the laboratory for 3-4 weeks. After acclimation, hemolymph was drawn from oysters and granular hemocytes were tested in vitro. Measurements of time to hemocyte spreading (TTS) and rate of hemocyte locomotion (ROL) were made in six media ranging in salinity from 6-36 ppt. TTS measurements were fastest at the acclimation salinities and slowed with acute rises in salinity. The time to spreading may be a measure of the osmotic adjustment process. Locomotion was dependent on ameboid shape. ROL decreased with acute rises in salinity for both populations, and increased with acute reductions in salinity for all test conditions except HS hemocytes acclimated at 30 and 36 ppt salinity. ROL tested at the acclimation salinities showed no differences between HS oysters (complete acclimation to lower salinities) but LS oyster hemocytes at 30 and 36 ppt ...

86 citations


Journal ArticleDOI
TL;DR: Shipboard studies showed major differences in the incorporation of CO2 by the specific prokaryotic symbionts of two deep-sea vent invertebrates, and metabolic dissimilarities between the symbiont of the two hosts extend to DNA base ratios and cell sizes.
Abstract: Shipboard studies showed major differences in the incorporation of CO2 by the specific prokaryotic symbionts of two deep-sea vent invertebrates. The rate of CO2 fixation was optimal at approximately 22°Cin fresh trophosome material from the pogonophoran tube worm R@/1iapachyptila. Sulfide, but not thiosulfate, served as the electron donor. Thirty-five percent ofthe aerobic rate remained in deoxygenated sam pies presumablydue to traces of hemoglobin-bound oxygen. Gill preparationsfrom the mytilid mussel Bathymodiolus thermophilus,however, assimilated CO2 with a maximum rate at 12° to 15°C. Thiosulfate, but not sulfide, served as the electron donor.The activitywascompletelyinhibitedin deoxygenatedsamples.Thesemetabolic dissimilarities between the symbionts ofthe two hosts extend to DNA base ratios and cell sizes. Partialfractionationofthe mussel gill preparationyielded a prokaryoticor “?�bacterial” fraction that showed a CO2 assimilation rate three-fold higher than that of the crude homogenate. This activity was not affected by the in situ hydrostatic pressure of 250 atm (100% barotolerance). The mussel gill symbiont represents the first sulfur-oxidizing vent prokaryote with psychrophilic growth characteristics. The natural distribution ofR. pachyptila and B. thermophilus within the physico-chemical regime ofthe immediate vent vicinity corresponds well with the metabolic differences oftheir symbionts.

Journal ArticleDOI
TL;DR: Biaxial stressing tests demonstrate that the skins of the spot and the skipjack do not behave as simple crossed-fiber systems, and are therefore incapable of transmitting forces down the lengths of these fishes or acting as "extensible" systems.
Abstract: The skin of the Norfolk spot, Leiostomus xanthurus, is composed largely of a crossed-helical array of collagen fibers. Over most of the body of the fish these are oriented at angles of 45-80° with the long axis of the fish. The skin of the skipjack tuna, Katsuwonus pelamis, also contains a crossed-helical array of collagen fibers, although fewer fiber layers are present and fiber angles are generally in the range of 55-75°. Uniaxial stress-strain tests indicate that for both species skin is most extensible in the longitudinal direction. For the Norfolk spot, skin is stiffer in the direction of the fibers than in the circumferential direction, but for the skipjack tuna, the skin is of about the same stiffness in the circumferential direction as it is in the direction of the fibers. Biaxial stressing tests demonstrate that the skins of the spot and the skipjack do not behave as simple crossed-fiber systems, and are therefore incapable of transmitting forces down the lengths of these fishes or acting as "ext...

Journal ArticleDOI
TL;DR: Holothurian metamorphosis for a relatively unspecialized aspidochirote, Stichopus californicus, is described here and assignment of holothurians with echinoids to the subphylum Echinozoa is discussed.
Abstract: Descriptions of holothurian metamorphosis are based on data from the relatively specialized order Apoda. Metamorphosis for a relatively unspecialized aspidochirote, Stichopus californicus, is described here. Metamorphosis in Stichopus is characterized by the following features: the madreporic vesicle is a calcite secreting syncytium, not a coelom. Stichopus has no separate axocoel and no transient axial complex forms during metamorphosis. The buccal podia form from the water vascular ring, not the radii. The axes of bilateral larval symmetry and the pentaradial adult symmetry are congruent; therefore, the secondarily derived symmetry in holothurians is the pentaradial symmetry of the adult, as in the other extant echinoderms. No axial or visceral torsion occurs during metamorphosis. The enclosed ambulacra form in a manner distinct from that of the ophiuroids and echinoids. Perivisceral coelomic pores develop near the end of metamorphosis, and before the definitive anus forms. Assignment of holothurians with echinoids to the subphylum Echinozoa is discussed.

Journal ArticleDOI
TL;DR: Although invertebrate deuterostomes are believed to lack discrete excretory organs, an analysis of the metamorphosis of the larval nephridia suggests that adult echi...
Abstract: The pore canal-hydropore complex in the larvae of echinoderms and hemichordates has long been recognized as an important character establishing a close phylogenetic relationship between the two phyla. An experimental and ultrastructural analysis of this complex in a tornaria and a bipinnaria larva indicates that it is a functional nephridium. The ciliated pore canal drives a constant, unidirectional efflux of coelomic fluid out of the hydropore. Two percent and 14% ofthe body volume are cleared per hour at the hydropore by a tornaria of Schizocardium brasiliense and a bipinnaria of Asterias forbesi, respectively. Fluid recovery by the coelom is from the blastocoel, the presumptive blood vascular space, across basal lamina and podocytes lining the coelomic cavity suggesting that the discharged fluid is formed by ciliary-driven ultrafiltration. Although invertebrate deuterostomes are believed to lack discrete excretory organs, an analysis of the metamorphosis of the larval nephridia suggests that adult echi...

Journal ArticleDOI
TL;DR: It is concluded that repeated loading enables crabs to open larger bivalves than could be crushed outright; by greatly increasing the maximum size of prey vulnerability this expands the size range of molluscan prey available to crabs.
Abstract: Observations of behavior and direct measurements of force indicated that the cancrid crab Cancer productus could directly crush only the smallest specimens of Protothaca staminea, a venerid bivalve. Crabs opened larger P. staminea by repeatedly loading the same region of the bivalve's shell with a chela; we hypothesized that this repeated loading caused fatigue of the shell material. To test whether significant fatigue damage would accumulate in the number of cycles a crab was likely to exert, live bivalves and cleaned valves were cyclically loaded in a mechanical testing machine to loads of a constant maximum amplitude of 70-100% of the bivalves' predicted static strength. Failure frequently occurred in fewer than 200 cycles. Recordings from strain gauges attached to the chelae of crabs showed that during an attack on a bivalve a crab would squeeze more than 200 times and that failure of the bivalve could occur during a force pulse which was weaker than previous force pulses. We conclude that repeated loading enables crabs to open larger bivalves than could be crushed outright; by greatly increasing the maximum size of prey vulnerability this expands the size range of molluscan prey available to crabs.

Journal ArticleDOI
TL;DR: Field studies suggest mucous trails can, but may not always, persist long enough to allow algal enhancement, and biochemical analyses suggest that the ability of mucous Trails to trap microalgae adhesively is correlated with carbohydrate content.
Abstract: ABSTRACI The mucous trails secreted by certain species of intertidal limpets serve as adhe sive traps for the microalgae that are their primary food resources. The mucous trails of two solitary homing limpets, Lottia gigantea and Coiisella scabra, also stimulate the growth of microalgae. In contrast, the mucous trails of an aggregating limpet, Coiisella digitalis, and the carnivorous dog whelk, Nucella emarginata, do not stim ulate microalgal growth. These results may be explained by differences in the behav ior of these gastropod species. Homing species can capitalize on the production of a food enhancing mucus because they have restricted home ranges and retrace their own mucous trails. The persistence time of mucus in the field varied with gastropod species, mucus type (i.e., mucus produced by moving or stationary limpets), and tidal height. Field studies suggest mucous trails can, but may not always, persist long enough to allow algal enhancement. Biochemical analyses suggest that the ability of mucous trails to trap microalgae adhesively is correlated with carbohydrate content. The ability of mucous trails to stimulate microalgal growth is correlated with higher total organic content of mucous secretions and an ability to stimulate bacterial growth. A bacterial film may be impor tant in the stimulation effect.

Journal ArticleDOI
TL;DR: The sexual reproduction of the alcyonacean octocoral Sarcophyton glaucum was studied for a period of about four years on the coral reefs of the northern Red Sea to study the synchronous maturation of numero...
Abstract: The sexual reproduction of the alcyonacean octocoral Sarcophyton glaucum (Quoy & Gaimard, 1833) was studied for a period of about four years on the coral reefs of the northern Red Sea. S. glaucum is a dioecious species with gonads borne in the autozooids. The smallest colonies bearing testes measure 11 cm3 (6-7 years old) while females attain maturity at a much larger colony size of at least 61 cm3 (> ten years old). Sex ratio of the population is 1:1. The annual development of the sperm sacs takes 10-12 months. Oogenesis occurs every year, however egg maturation requires 22-23 months, resulting in the presence of two cohorts of oocytes in each female. The mature eggs are large with a maximal diameter of 500-750 µm. S. glaucum has a brief annual spawning period which occurs in the majority of the population during a single night (in 1980, spawning was on 9 July). The large size of the eggs is not the ultimate cause for their prolonged period of oogenesis. Nevertheless, the synchronous maturation of numero...

Journal ArticleDOI
TL;DR: Sea anemones fed 35S methionine labeled food translocated labeled material to symbiotic zooxanthellae took up host-derived organic materials and were interpreted as evidence for heterotrophy, suggesting that the reinfection of the symbiotic animals by zooxanhellae caused a decrease in animal biomass.
Abstract: Sea anemones (Aiptasia pulchella) fed 35S methionine labeled food translocated labeled material to symbiotic zooxanthellae. This uptake of host-derived organic materials by the symbiotic algae is interpreted as evidence for heterotrophy. It is calculated that 2.8-6.4% of the zooxanthellae growth requirement for protein was satisfied by heterotrophy under a 12 hour light:12 hour dark photoperiod. The cost of algal heterotrophy to the animal host was demonstrated by exposing aposymbiotic anemones to cultured zooxanthellae. Aposymbiotic animals rapidly re-established a stable symbiosis, but the symbiotic animals had a protein biomass significantly lower than control aposymbionts, suggesting that the reinfection of the symbiotic animals by zooxanthellae caused a decrease in animal biomass. Zooxanthellae spontaneously appeared and grew in the control aposymbionts. These repopulating algal cells were apparently derived from a residual heterotrophic population of zooxanthellae maintained by anemones after four y...

Journal ArticleDOI
TL;DR: To integrate very long-term disparity in growth rates associated with infestation, mussels from a robust, naturally occurring population of mussels are used, used to measure shell accretion in the field and numerically characterizing shell shape.
Abstract: ABsTRACr Pea crabs living within the mantle cavities ofa variety ofbivalve hosts have several adverse effects. In blue mussels (Mytilus edulis L.), the crab Pinnotheres maculatus (Say) steals food strands and causes gil lesions. We studied the long-term stress of P. maculatus on its host by measuring shell accretion in the field, and by numerically characterizing shell shape. Shell form in M. edulis is presumed to reflect environmental and physiological history. We computed growth increments in infested populations of mussels over a three-month period at two sites with high and low nutrient regimes. When growth was measured by change in shell length, significant differences between mussels with and without large pea crabs occurred at the low nutrient site, but not where mussels enjoyed a high nutrient regime. To integrate very long-term disparity in growth rates associated with infestation, we used mussels from a robust, naturally occurring population. We recorded and analyzed mussel sithouette shapes with a video digitizer. Elliptic Fourier approximation completely characterized the two-dimensional outlines of shells in such a way that the allometric dependence of shape variables on shell size could be easily removed. At this evidently favorable site, infested mussels displayed significant shell shape distortion characteristic of reduced growth rates. Thus, even in apparently benign environments, pea crab infestation appears to be a chronic stress to M. edulis.

Journal ArticleDOI
TL;DR: Nutrient enrichments at 8x and 32x the average aerial input into Narragansett Bay, Rhode Island, resulted in increases in body length, segment number, and length per segment, and a doubling of brood size in S. benedicti females.
Abstract: The influence of organic enrichment on growth and planktotrophic development of the spionid polychaete Streblospio benedicti Webster was examined in two mesocosm experiments conducted at the MERL facility, University of Rhode Island. Specimens of S. benedicti were collected and their reproductive traits monitored near the conclusion of a two-year eutrophication experiment, and in the middle of a sludge addition experiment. Nutrient (N, P, and Si) enrichments at 8x and 32x the average aerial input into Narragansett Bay, Rhode Island, resulted in increases in body length, segment number, and length per segment, and a doubling of brood size in S. benedicti females. These increases were substantially higher during May (12°C) than August (20°C). Enrichment effects were stronger in the 8x than 32x nutrient treatment. In the sewage sludge experiment body size increased 20% over control values at the highest (8x) sludge treatment level (nitrogen loading equivalent to the 8x nutrient treatment) but no significant ...

Journal ArticleDOI
TL;DR: The structure and organization of the larval nervous system of the holothurian, Parasticopus californicus, is described using glyoxylic acid-induced fluorescence, indirect immunofluorescence with antibodies against serotonin, and transmission and scanning electron microscopy.
Abstract: The structure and organization of the larval nervous system of the holothurian, Parasticopus californicus, is described using glyoxylic acid-induced fluorescence, indirect immunofluorescence with antibodies against serotonin, and transmission and scanning electron microscopy. Tracts of catecholaminergic axons are located at the base of the ciliary bands and catecholaminergic nerve cell bodies are dispersed along the length of the ciliary bands. Clusters of catecholaminergic cells form a ganglion on the lower lip of the larva and a ganglion of serotonergic cells is located at the anterior tip of the larva. Serotonergic cells are scattered throughout the apical portion of the larva in the epidermis. Axon tracts identified only with TEM are located in the esophagus associated with the circumesophageal muscles. The neuroanatomy of the auricularia shares several features with larval forms of the other classes of echinoderms.

Journal ArticleDOI
TL;DR: Sex determination in this species, based on the sex ratio in triploids, best fits the model of an X:autosome balance mechanism as exemplified in some insect species.
Abstract: Triploid soft-shell clams (Mya arenaria) were produced by inhibiting polar body extrusion with cytochalasin B immediately after fertilization. Diploid and triploid clams grown in suspended tray culture were examined histologically during the reproductive season of their second year. Most diploids had matured by the end of May and displayed normal gametogenic development in every individual. Triploids did not mature and most had undeveloped gonads. The few triploid females which developed some oocytes by the end of May had abnormal maturation. Triploids were 77% female as judged by the presence of oocytes; another 16% were female-like and may have been intersexes; the sex of 6% could not be identified because there was no sexual differentiation. Sex determination in this species, based on the sex ratio in triploids, best fits the model of an X:autosome balance mechanism as exemplified in some insect species.

Journal ArticleDOI
TL;DR: Data support the hypothesis that selection to resist prying forces has been an important feature in the evolution of limpet shell morphology.
Abstract: The feeding behavior of rocky intertidal crabs in the tropical and temperate eastern Pacific was studied in relation to specific mechanical properties of the shells of their limpet prey. A series of laboratory experiments, involving direct observations, records of shell remains, and measurements of the forces generated by a feeding crab, showed that by far the most common feeding technique was to pry the margin of the limpet shell away from the substratum. The pattern of deformation in models of limpet shells subject to a similar prying force indicated (1) that the greatest stress on the shell was at the point of force application at the shell margin and (2) that the thickness of the shell margin contributed more to shell strength than did thickness in more apical regions of the shell. Measurements of the strength of real shells provided further support for this latter conclusion.In addition, the strength of foot attachment, which sets the maximum prying force that the shell can experience, closely parall...

Journal ArticleDOI
TL;DR: The best explanations for the anomalously high volumetric growth of juveniles relative to adults in December and January are: winter availability of a food source accessible only to juveniles or biochemical storage of energy during winter by adults in preparation for the process of rapid gametogenesis in spring.
Abstract: Thirteen monthly measurements of individually marked juvenile (16 mm long) and adult (60 mm long) specimens of Mercenaria mercenaria (L.) from field plots in North Carolina demonstrated similar seasonal patterns in size-adjusted monthly growth rates in shell volume: a large absolute maximum occurred in spring (April or May) with smaller relative maxima in mid summer and late autumn. The ratio of juvenile to adult size-adjusted growth rates in shell volume was nearly constant for ten months but then increased eight-fold in December and January. This growth anomaly between size classes could not be explained by examining dry weights of soma and gonads from additional marked juvenile and adult Mercenaria that were sacrificed monthly. Juveniles differed from adults by possessing negligible gonadal mass on all dates. However, knowledge of monthly changes in adult gonadal mass did not explain a significant amount of the residual variation in the regression of monthly juvenile volumetric growth on monthly adult volumetric growth. Seasonal changes in growth of adult gonadal mass and quarterly examinations of gonad histology both suggested a winter period of negligible gametogenesis followed by a spring burst of intense reproductive activity. The best explanations for the anomalously high

Journal ArticleDOI
TL;DR: While a influences only oxygen affinity, CO2 may influence cooperativity as well and this finding suggests that the effective species is molecular CO2.
Abstract: The effect of CO2 on hemocyanin-oxygen binding is not generally related to the effect of Cl-. Some hemocyanins respond to both and some to either one alone. The direction of the responses of O2 affinity of the various hemocyanins to CO2 is poorly correlated with the direction of responses to other effectors. The influence of CO2 on Busycon and Limulus hemocyanins reaches its maximum at high pH. Since the effect can be abolished by restoring divalent cation activities to the control levels prior to the addition of CO2, we suggest that the effect is not specific but rather indirect, by the pairing of the allosteric effectors Ca+2 and Mg+2 with the CO2 anions. In contrast the effect of CO2 on crustacean hemocyanins is greaterat low pH and it can be enhanced by maintaining HCO3- levels within narrow limits and permitting PCO2 to vary by a large factor. This finding suggests that the effective species is molecular CO2. While a influences only oxygen affinity, CO2 may influence cooperativity as well. Indifferen...

Journal ArticleDOI
TL;DR: Levels of toxicity and feeding deterrence were not correlated; i.e., feeding deterrence was as common among non-toxic corals as among toxic ones, may help to explain why some soft corals, which apparently lack toxic defense substances, do not exhibit signs of predation in the field.
Abstract: ABSTRACr Thirty-six specimens ofsoft corals (Coelenterata, Alcyonacea) were tested for tox icity by exposing Gambusia affinis (Vertebrata, Pisces) to aqueous extracts of coral macerate and assessing mortality. Fifty percent ofthe soft coral extracts were deter mined to be ichthyotoxic to the fish, supporting earlier studies. In another experi ment, commercial fish food was immersed in the same aqueous soft coral extracts, dried, and offered to G. affinis at three concentrations with appropriate controls. The study of feeding deterrence showed that 88% of the 36 extracts produced negative feeding responses atthehighest concentration. Atintermediate concentrations, 75% oftheextracts actedasfeeding deterrents; 48%showeddetectable deterrence atlowest concentrations. Levelsoftoxicity andfeeding deterrence, however, werenotcorre lated; i.e., feeding deterrence wasascommon amongnon-toxic corals asamongtoxic ones.Thisfinding may helptoexplain whysomesoftcorals, whichapparently lack toxic defense substances, donotexhibit signs ofpredation inthefield.

Journal ArticleDOI
TL;DR: Certain amino acids, peptides, and proteins are chemoattractants for Tetrahymena, since they increase swimming speeds, whereas attraction by PDGF may involve chemotaxis.
Abstract: Chemoattraction of Tetrahymena pyriformis, strain GL, was measured during starvation and under different growth conditions. Log phase cells starved in buffer are attracted by certain amino acids, peptides, and proteins. Cysteine, methionine, and phenylalanine are attractants at i0@ M. The peptides in proteose peptone (PP) and yeast extract (YE) are active at 10_6M. Epidermal growth factor (EGF) is active at >3 X i0@ M. Among the proteins, platelet derived growth factor (PDGF) is the most active (3 X 108 M). Cells growing in defined medium are attracted by PP, YE, and some proteins (PDGF). Swimming speed was measured for starved cells with and without added attractants or repellents. With addition of PP the swimming speed increases from 0.42 to 0.51 mm/s., but for PDGF it is unchanged. The swimming speed of starved cells increases when the cells approach a solidified attractant (PP) as measured by the speed at a given distance. The speed of cells moving towards the attractant is higher than that of cells moving away from it. In conclusion, certain amino acids, peptides, and proteins are chemoattractants for Tetrahymena. Chemokinesis likely plays a considerable role in the case of PP (and YE), since they increase swimming speeds, whereas attraction by PDGF may involve chemotaxis.

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TL;DR: Shell birefringence was detected at preveliger stages in all species and indicates that at least for three species studied (S. solidissima, A. papillosa, and H. crassicornis), the SFI is still present during initial shell mineralization; thus for these three species the cells of the S FI may be involved in initial shell calcification.
Abstract: Embryos of Spisula solidissima (Bivalvia); Crepidula fornicata, C. convexa, Ilyanassa obsoleta (Gastropoda: Prosobranchia); and Dendronotus frondosus, Aeolidia papillosa, and Hermissenda crassicornis (Gastropoda: Opisthobranchia) were reared in the laboratory and examined periodically to determine when shell mineralization began, as detected by birefringence under polarized light. Shell birefringence was detected at preveliger stages in all species. At onset of shell birefringence, samples were prepared for transmission electron microscopy to determine ifthe transitory shell field invagination (SFI) was still present. Contrary to previous reports for other molluscs, the present ultrastructural evidence indicates that at least for three species studied (S. solidissima, A. papillosa, and H. crassicornis), the SFI is still present during initial shell mineralization; thus for these three species the cells of the SFI may be involved in initial shell calcification. Electron cytochemical staining with pyroantim...

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TL;DR: Results indicate that the trigger is the onset of darkness (not onset of light) of the preceding day under natural illumination, which is a light signal that stimulates the sponge colonies to release larvae.
Abstract: The intertidal sponge, Halichondria panicea, regularly begins releasing larvae shortly after dawn, and ejects most of them during morning hours under a natural light-dark (LD) cycle. Its diurnal periodicity was confirmed under an artificial LD 12:12h cycle. In search of a trigger that stimulates the sponge colonies to release larvae, the colonies were subjected to experimentally modified LD cycles. Under continuous darkness, only a single release peak was observed about fifteen hours after the beginning of darkness. Further, the colonies invariably released larvae about fifteen hours after the change from light to dark on the preceding day under all illumination regimes examined. The timing of their larval release was independent of both the tidal cycle and the daily cycle of seawater temperature. These results indicate that the trigger is a light signal: the onset of darkness (not onset of light) of the preceding day under natural illumination. Subsequent to this stimulus, H. panicea needs a period of fi...

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TL;DR: The presence of NE in oyster larvae at the time of meetingamorphosis supports the hypothesis of a role for endogenous NE in mediating metamorphosis.
Abstract: ABSTRi@CT Oyster larvae and spat of varying ages were homogenized and analyzed for cate cholamine content using high-performance liquid chromatography with electro chemical detection. Norepinephrine (NE) and dopamine (DA) were found in appre ciable quantities, with more DA present than NE. The presence of epinephnne was equivocal. Norepinephrine levels were low in young larvae (0.062 ± 0.035 pgJ@tg pro tein), then increased to an intermediate level (0.5 17 ± 0.031 pgJ@ig protein) for most of the larval period and finally increased again just before metamorphosis to 1.08 ±0.09 p@ig protein. Dopamine levels in the corresponding larval groups did not change significantly, with 11.5 ± 1.9, 8.58 ± 0.98, and 7.47 ± 0.92 pg DA/sg protein, respectively. The levels of NE (1.00 ± 0.04 pg/tag protein) and DA (7. 13 ± 0.29 pg/ @ig protein) present in spat following metamorphosis were not significantly different from the pre-metamorphic values. The presence ofNE in oyster larvae at the time of metamorphosis supports the hypothesis of a role for endogenous NE in mediating metamorphosis. IrsrrRoDucmoN Although norepinephrine (NE) is a major neurotransmitter in the vertebrates, its role(s) in the invertebrates has not been established (Welsh, 1972; Leake and Walker, 1980;Gospe, 1983). Although low levels ofNE have been found in most invertebrate phyla, there has been little evidence ofa functional role for NE or for the presence of receptors that might mediate such a function. However, Coon et al. (1985) have demonstrated that larvae of the Pacific oyster Crassostrea gigas (Thunberg), can be induced to metamorphose from a pelagic larval stage to a sessile juvenile stage by a brief (<1h)exposure toNE orepinephrine (EPI), andsubsequent research (seebe low) suggests catecholamines may be directly involved in natural oyster metamor phosis. Prior to metamorphosis, C. gigas larvae, like many marine invertebrate larvae, are pelagic and must spend some period of growth and development in the plankton. At a certain developmental stage, the larvae become competent to respond to appro priate environmental stimuli, which can cause them to proceed through a series of complex stereotyped behaviors called settlement. If a suitable substrate is encoun tered during settlement, the larvae will attach to it irreversibly. After attachment, the larvae undergo a morphological and physiological metamorphosis to a sessilejuvenile stage. Norepinephrine- and EPI-induced metamorphosis is independent of settle ment and attachment; upon exposure to NE or EPI, the larvae sink to the bottom and metamorphose without attaching (Coon et al., 1985). Coon and Bonar (submitted) have shown that induction of metamorphosis by