Showing papers in "The Biological Bulletin in 1980"
TL;DR: The coral Astrangia danae is dioecious, with an early age of first reproduction, and this species exhibits an annual reproductive cycle with gametogenesis starting in March-April, and vestigial gametes are absorbed during the winter months.
Abstract: 1. The coral Astrangia danae is dioecious, with an early age of first reproduction.2. In Narragansett Bay, this species exhibits an annual reproductive cycle with gametogenesis starting in March-April. Spawning occurs during August, and vestigial gametes are absorbed during the winter months.3. Gametes originate from interstitial cells which differentiate in the mesenterial mesoglea.4. Ova are 100-130-µm in diameter and sperm are 2-3-µm in length, excluding the tails. Egg production was estimated at up to 6000 eggs per polyp.5. Fertilization and development are external; no fertilization membrane was seen even though a layer of cortical vesicles was present before fertilization.6. Embryonic cell divisions are around 30 min apart and the larval planual stage is reached within 12-15 hr after fertilization. Larval settlement was not observed.7. Ova from colonies containing zooxanthellae did not contain zooxanthellae when spawned.
149 citations
TL;DR: Time-lapse cinematography was used with laboratory-reared specimens of M. sexta to obtain information on and timing of behavioral activities.
Abstract: 1. Time-lapse cinematography was used with laboratory-reared specimens of M. sexta to obtain information on and timing of behavioral activities.2. Insects used in this study were selected as the mo...
132 citations
TL;DR: These findings point to a previously unsuspected shifting role of JH in the control of metamorphosis, and apparently the secretion and inhibitory action of J H persists in brainless fourth-instar larvae.
Abstract: 1. Juvenile hormone delayed or prevented the onset of metamorphosis by neck-ligated fourth-instar tobacco hornworm larvae and by fifth instars neck-ligated prior to the cessation of feeding.2. After the onset of the wandering period J H had precisely the opposite effects in that it accelerated the onset of metamorphosis. This was the case both for wandering larvae and for pupae, irrespective of whether they were intact or subjected to brain removal or neck ligation.3. These findings point to a previously unsuspected shifting role of JH in the control of metamorphosis.4. Fourth-instar larvae underwent no further development after brain removal unless they were also effectively allatectomized by neck ligation. Evidently the secretion and inhibitory action of JH persists in brainless fourth-instar larvae.5. Brainless fifths, by contrast, were often able to initiate metamorphosis despite the continued presence of their CA. Development could be prevented by daily application of JH. The disappearance of effecti...
114 citations
TL;DR: The first zoeal stage of Callinectes sapidus shows negative geotaxis unaffected by salinity changes of 5‰; high barokinesis at pressure increments above 1 atm; an increase in swimming rate with a salinity increase; and maintenance of swimming rate as temperature drops.
Abstract: 1. The first zoeal stage of Callinectes sapidus shows negative geotaxis unaffected by salinity changes of 5‰; high barokinesis at pressure increments above 1 atm; an increase in swimming rate with a salinity increase; and maintenance of swimming rate as temperature drops.2. Stage IV larvae show both positive and negative geotaxis. As salinity drops, positive geotaxis prevails; as it increases negative geotaxis prevails. Stage IV larvae show a tendency to reduce swimming rate as pressure increases, as temperature drops, and as they become acclimated to higher salinities.3. Stage VII larvae show positive geotaxis and reduced swimming rate in response to increased pressure, reduced temperature, and as they are acclimated to increased salinity.4. Between hatching and the seventh (terminal) zoeal stage, passive sinking rate increases 3.2-fold, while swimming rate increases 4.4-fold.5. These responses to environmental stimuli produce a pattern of early stages moving to surface waters and later stages to deeper ...
100 citations
TL;DR: In this article, the patterns of sexuality and asexual reproduction in 10 species of subtidal Demospongiae were investigated by following reproductive activity in particular individuals and in the populations of each species over a 2-year period.
Abstract: 1. The patterns of sexuality and asexual reproduction in 10 species of subtidal Demospongiae were investigated by following reproductive activity in particular individuals and in the populations of each species over a 2-year period. Potential reproductive output was measured and related to recruitment rates recorded from natural and artificial surfaces.2. The ceractinomorph sponges were found to be all hermaphrodites producing viviparous larvae while most of the tetractinomorph sponges were found to be gonochoric over the period of study and apparently oviparous. In the tetractinomorph sponge populations there was usually a majority of females and in two species no males were found. Three of the tetractinomorph species also produced buds.3. Viviparous larvae are thought to be adaptations to habitats with high levels of disturbance.4. Recruitment in both groups of sponges was low and unpredictable except in Polymastia sp. (yellow) which produced buds all year round and had predictable recruitment of low nu...
100 citations
TL;DR: The morphology of large cortical specializations (rods) located in the peripheral ooplasm is described in oocytes of the shrimp Penaeus aztecus and confirmed with P. setiferus.
Abstract: The morphology of large cortical specializations (rods) located in the peripheral ooplasm is described in oocytes of the shrimp Penaeus aztecus and confirmed with P. setiferus. The rods, which are perpendicular to the oolemma, are "club"-shaped and approximately 39.9 µm long, with an apical diameter of 9.3 µm and a basal diameter of 4.6 µm. They are composed of numerous, tightly packed, fibrillar structures. Each cortical rod lies within a partially membrane-bound crypt and is separated from the external media by a thin investment coat. The investment coat lies directly adjacent to the oolemma and completely surrounds the egg. Upon exposure to sea water, the cortical rods begin to emerge from the crypts and appear to lift the investment coat off the egg surface. A corona is formed around the oocyte as the rods are expelled, but quickly dissipates. Extensive membrane vesiculation associated with cortical rod crypts is apparent at this time.
97 citations
TL;DR: Drills exposed to diurnal tidal fluctuations of salinity, reflecting the estuarine environment, had predation rates significantly less than those at the optimal constant salinity (20‰) at 30° C, but were not significantly less at 20° C.
Abstract: 1. The predation and ingestion rate of Thais haemastoma on oyster spat is sensitive to temperature and salinity. The effect of salinity on predation rate was different at 20° and 30° C.2. The temperature threshold for predation was between 10° and 12.5° C; drills were not observed to feed below 7.5‰.3. Drills exposed to diurnal tidal fluctuations of salinity, reflecting the estuarine environment, had predation rates significantly less than those at the optimal constant salinity (20‰) at 30° C, but were not significantly less at 20° C. The predation and ingestion rates in the fluctuating salinity cycles were not significantly different than rates for drills at the constant acclimation salinities of 10 and 30‰.4. Predation rates were not significantly affected by drill sex or weight and length. However, the experiments were designed to exclude size effects by selecting drills within a size range of 45 to 55 mm.5. Predation rates were not significantly different between large drills feeding as individuals (1...
92 citations
TL;DR: The acrorhagial responses of four sea anemones, Anthopleura krebsi, Bunodosoma cavernata, Anemonia sargassensis, andAnthopleura xanthogrammica, are described and can be considered forms of aggression.
Abstract: The acrorhagial responses of four sea anemones, Anthopleura krebsi, Bunodosoma cavernata, Anemonia sargassensis, and Anthopleura xanthogrammica, are described. All four acrorhagial responses can be...
87 citations
TL;DR: Analyses for tissue copper concentrations showed that the gill was the primary organ for the concentration of copper and exhibited a linear relationship between its copper content and the exposure concentration, which was associated with high mortalities and a sublethal cytotoxic response.
Abstract: 1. Clams of the species Protothaca staminea were exposed to a range of copper concentrations of control (= 0.35), 7, 18, 39 and 82 µg/l for 30 days.2. Mortalities were monitored during the exposure. The results indicated that copper concentrations of 39 and 82 µg/l were extremely stressful with survivals of only 14 and 3%, respectively, after 30 days. At 7 and 18 µg/l, survival was slightly reduced when compared to controls.3. Analyses for tissue copper concentrations showed that the gill was the primary organ for the concentration of copper and exhibited a linear relationship between its copper content and the exposure concentration.4. Effects of copper on the gill were demonstrated by a disruption of sodium and potassium regulation at 39 µ/l and increases in acid phosphatase activity at lower exposure concentrations. The former was associated with high mortalities, while the latter was considered to be a sublethal cytotoxic response.5. Two low-molecular-weight, copper-binding proteins could be distingui...
86 citations
TL;DR: The skin of the American eel Anguilla rostrata is composed of a crossed-helical array of fibers that are oriented at an angle of 45° with the long axis of the fish, and the mechanical behavior of the skin indicates that it is stiffest in the direction of the fibers.
Abstract: 1. The skin of the American eel Anguilla rostrata is composed largely of a crossed-helical array of fibers, believed to be collagen, that are oriented at an angle of 45° with the long axis of the fish. Uniaxial and biaxial tension testing of eel skin was used to assess the role of the collagen fibers in the locomotor functions of the skin.2. The elastic modulus of skin stressed in the circumferential direction of the fish is 14.6 MN/m2 while that of skin stressed in the longitudinal direction is 3.5 MN/m2, thus eel skin is an order of magnitude stiffer in the circumferential than in the longitudinal direction. The skin is stiffest in the direction of the fibers, having an elastic modulus of 0.16 GN/m2 in this direction. Within the range of in vivo extensions the behavior of skin stressed in the longitudinal direction is similar to that of a model consisting of continuous crossed-fibers, while that of skin stressed in the circumferential direction is not.3. The mechanical behavior of the skin indicates tha...
85 citations
TL;DR: Coelomic cells from solitary ascidians exhibit a nonphagocytic cellular reaction when they are mixed in vitro with such cells from different species or another individual of the same species, and this reaction was denoted "contact reaction".
Abstract: Coelomic cells from solitary ascidians exhibit a nonphagocytic cellular reaction when they are mixed in vitro with such cells from different species or another individual of the same species. The reaction is triggered by direct contact between reactive cells and hence was denoted "contact reaction." The contact reaction is reciprocal and results in mutual cell deaths or a state of prolonged incapacitation of both cells involved. Coelomic cells of several morphological types are capable of carrying out the reaction. Similar reactions were also observed in vivo when foreign cells were deliberately introduced into intact animals.Individuals from a single variant type of Halocynthia roretzi (Drasche) are mutually reactive when their cells are brought into contact, but not in every combination of individuals. The patterns of positive and negative contact reactivity among such allogeneic individuals do not follow conventional rules of transplantation genetics established for the vertebrates. These reactions see...
TL;DR: Hippodamia convergens migrates long distances to and from mountain-top aggregation sites and undergoes an imaginal diapause associated with a 6-9 month aestivo-hibernation at the aggregation sites.
Abstract: Hippodamia convergens migrates long distances to and from mountain-top aggregation sites. It undergoes an imaginal diapause associated with a 6-9 month aestivo-hibernation at the aggregation sites. Laboratory tethered-flight tests can be used as an assay for migratory behavior. Beetles that fly 30 min on a tether will nearly always fly much longer.Long tethered flight is pre-reproductive in females, though apparently not in males. Starvation or poor quality food will greatly enhance migratory behavior. However, the tendency to display migratory behavior is greatly reduced in both sexes after about 7 days of optimum food. Even starvation at that time will not stimulate an increase in long-flight behavior. It would appear that some type of physiological committment to reproduction which excludes or greatly reduces the tendency to migrate is made at that time. Photoperiod has little effect on migratory behavior when food is poor. But under optimal feeding conditions, short photoperiod enhances long flight be...
TL;DR: It is suggested that differences in rate of respiration are the result of differences in energy expenditure in the biosynthesis of tissue growth and that this is determined to a large extent by the nutritional input into the colony from the zooxanthellae.
Abstract: 1. The rate of oxygen consumption of a number of Caribbean corals was determined, in darkness, and the results expressed on a unit-weight and unit-surface-area basis to enable inter-and intraspecific comparisons to be made.2. Intraspecific comparisons of Montastrea annularis and M. cavernosa and comparisons between species of Agaricia show that corals living in deep water (40 m) have lower rates of respiration than shallow-water corals.3. Corals, such as Acropora and Agaricia, with a high surface-to-volume ratio have higher rates of respiration per unit weight than the massive corals like Montastrea.4. It is suggested that differences in rate of respiration are the result of differences in energy expenditure in the biosynthesis of tissue growth and that this is determined to a large extent by the nutritional input into the colony from the zooxanthellae.
TL;DR: The crushing strength of 170 specimens of shells of 21 species of Thaididae has been measured and it is shown that the tropical shells are much stronger, mass for mass, than the temperate ones.
Abstract: The crushing strength of 170 specimens of shells of 21 species of Thaididae has been measured. In general, the tropical shells are much stronger, mass for mass, than the temperate ones. This strength is achieved mainly by the shells being thicker walled in the tropics, thereby leaving less room for the animal inside.
TL;DR: Sebens et al. as mentioned in this paper found that Anthopleura elegantissima does not divide in the fall and winter when individual anemones are decreasing in size and the mean size of clonal individuals decreases with increasing intertidal height and with increasing tidepool temperature.
Abstract: The sea anemone, Anthopleura elegantissima, forms distinct clonal aggregations in the field by longitudinal fission (Hand, 1955, Ford, 1964, Francis, 1973a, b, 1976, Sebens, 1977). Field observations indicate that division takes place most often in the fall and winter when individual anemones are decreasing in size (Sebens, 1977). Mean size of clonal individuals decreases with increasing intertidal height (Sebens, 1977) and with increasing tidepool temperature at a given height.In the laboratory, asexual division is inhibited when A. elegantissima is fed continuously. Such division occurs more rapidly and in a larger fraction of the population as ambient water temperature increases. Starvation, defined as weight loss, is not in itself sufficient stimulus to initiate the division process. Shrinking individuals, given food, do not divide even though that food may not be efficiently assimilated (as at 20° and 25° C). Strong light or darkness has no significant effect on the division process although it has a...
TL;DR: The diet of the opossum shrimp, Neomysis mercedis, in the Sacramento River Estuary was studied in relation to food availability, i.e., plankton, from January through November, 1976 and it was determined that predation on rotifers and copepods accounted for > 80% of the energy consumed by other-than-juvenile mysids.
Abstract: The diet of the opossum shrimp, Neomysis mercedis, in the Sacramento River Estuary was studied in relation to food availability, i.e., plankton, from January through November, 1976. The composition of the diet of N. mercedis varied in relation to mysid size and prey availability. Mysids exhibited strong positive selection for the large diatom prey species while "avoiding" small diatom prey. Although diatoms were the most abundant prey identified from the guts of specimens of N. mercedis it was determined that predation on rotifers and copepods accounted for > 80% of the energy consumed by other-than-juvenile mysids (≥7 mm in length). Juvenile mysids (≤ 3 mm in length) ingested rotifers when rotifers were abundant but were not found to consume copepods. Laboratory feeding experiments indicate a density-dependent feeding by N. mercedis on copepods, i.e., as copepod density increases mysid predation on copepods also increases. Feeding observations indicate that N. mercedis is not a particularly active predat...
TL;DR: Intuitive formulations concerning the nature of cellular substrates for associative learning are considered and a sequence of neural processes is proposed to underlie acquisition and retention of an associative behavioral change of Hermissenda.
Abstract: Intuitive formulations concerning the nature of cellular substrates for associative learning are considered. Invertebrate models of vertebrate learning are discussed. A cellular analysis of a long-term associative behavioral change is reviewed for the nudibranch mollusc Hermissenda crassicornis. Convergence of neuronal pathways which mediate natural sensory stimuli used for associative training have been determined. Primary biophysical changes within single identified neurons are analyzed for their causal role in learning behavior. A sequence of neural processes is proposed to underlie acquisition and retention of an associative behavioral change of Hermissenda. Paired sensory stimuli enhance voltage-dependent currents by means of converging sensory pathways. Repeated pairings cause progressive membrane depolarization, which in turn causes long-lasting conductance changes. Biochemical correlates of these phenomena are presented.
TL;DR: In this paper, the calanoid copepod Labidocera aestiva was reared in the laboratory at 15°C and the results indicated that photoperiod is an important factor controlling the life cycle of L. aestiva.
Abstract: The calanoid copepod Labidocera aestiva was reared in the laboratory at 15°C. Individuals that developed under a photoperiod regime of 18L:6D produced subitaneous eggs, whereas copepods exposed to a short-day regime of 8L:16D produced mostly diapause eggs. The results indicate that photoperiod is an important factor controlling the life cycle of L. aestiva. It is suggested that in Vineyard Sound, MA, this species produces subitaneous eggs during the summer in response to long daylengths, and in the fall produces mostly diapause eggs in response to short daylengths.
TL;DR: The effects of group size and intensity of constant illumination on the circadian locomotor activity of the Atlantic killifish, Fundulus heteroclitus, were examined and Circadian period lengths and relations to LL of shoaling fish were significantly reduced.
Abstract: The effects of group size and intensity of constant illumination on the circadian locomotor activity of the Atlantic killifish, Fundulus heteroclitus, were examined. Individual fish displayed a free running circadian rhythm of locomotor activity under constant darkness (DD) and constant illumination (LL). The period length (r) under DD was significantly greater than that under LL (26.3 ± 0.20 hr for DD as compared to 24.6 ± 0.40 hr at 100 lux). Period lengths were significantly dependent on the intensity of constant illumination. Groups of 5 fish displayed more variable circadian activity with no significant differences in r values from DD and LL. The group of 25 fish formed a shoal and displayed precise circadian periods under DD and LL. The DD period was significantly greater than that under LL (25.7 ± 0.20 hr for DD as compared to 24.7 ± 0.20 hr for 100 lux). r also decreased with increasing intensity of illumination. Circadian period lengths and relations to LL of shoaling fish were significantly diff...
TL;DR: The amount of time required to consume specimens of L. littorea depended on snail size (shell length), reflecting different methods of attack by crabs, and in the laboratory, crabs required more time to locate and attack periwinkles in rock crevices than periwinkingles on rock surfaces.
Abstract: Individuals of Littorina littorea in rocky intertidal pools crawled to pool sites where they were less visible (into rock crevices; under rocks and macroalgal fronds) when either crushed conspecifics or juice from crushed conspecifics was added to these pools. A significant proportion of snails hid in 10 min or less; individual snails in one pool tested quadrupled their crawling velocities after snail juice was added.Field observations and laboratory experiments tested the hypothesis that this alarm behavior helps L. littorea avoid being eaten. Green crabs (Carcinus maenas) were observed consuming individuals of L. littorea in tide pools at night and along the shore at high tide during the day. In the laboratory, crabs required more time to locate and attack periwinkles in rock crevices than periwinkles on rock surfaces. The amount of time required to consume specimens of L. littorea depended on snail size (shell length), reflecting different methods of attack by crabs. Small snails (< 9.0 mm) were crushe...
TL;DR: 1-Methyladenine, known as the maturation-inducing hormone of starfishes, failed to induce oocyte maturation of the sea cucumbers, and mature eggs obtained with DTT treatment developed to the typical auricularia larvae.
Abstract: Isolated oocytes of the sea cucumbers Holothuria leucospilota and Holothuria pardalis were induced to mature with 2,3-dimercapto-1-propanol (BAL), dithiothreitol (DTT) and L-cysteine. 1-Methyladenine, known as the maturation-inducing hormone of starfishes, failed to induce oocyte maturation of the sea cucumbers. Observation of the maturation process revealed that the germinal-vesicle of the oocyte treated with DTT migrated to the micropyle process and broke down there, where polar bodies were subsequently formed. After insemination, mature eggs obtained with DTT treatment developed to the typical auricularia larvae.
TL;DR: In Phyllospadix beds of central California, the gastropods Lacuna marmorata, Alia carinata, and Notoacmea paleacea have defensive adaptations that reduce the frequency of predation by the predatory seastar Leptasterias hexactis.
Abstract: 1. In Phyllospadix beds of central California, the gastropods Lacuna marmorata, Alia carinata, and Notoacmea paleacea occur in abundance with the predatory seastar Leptasterias hexactis. All three gastropods have defensive adaptations that reduce the frequency of predation by this seastar.2. Lacuna responds to waterborne chemicals ("scent") emanating from distant Leptasterias by rotating the shell through an arc of 360°, waving its cephalic tentacles, and increasing general activity. Upon contact with the predator, Lacuna flees by falling off the Phyllospadix blade.3. Alia does not respond vigorously to the scent of distant specimens of Leptasterias. Upon contact with Leptasterias, Alia rears up on the posterior portion of the foot and then begins to run away. If contact with the seastar persists, the snail strikes at the seastar's tube feet with its proboscis.4. N. paleacea does not give a behavioral defensive response to Leptasterias. Rather, this stenotopic limpet may be chemically camouflaged, and thi...
TL;DR: Effects of the parasitic isopod, Probopyrus pandalicola, on the sex characters of its host shrimp, Palaemonetes paludosus, are described, and possible mechanisms for these effects are discussed.
Abstract: Effects of the parasitic isopod, Probopyrus pandalicola, on the sex characters of its host shrimp, Palaemonetes paludosus, are described, and possible mechanisms for these effects are discussed. P. pandalicola sterilize the female host by preventing ovarian maturation but do not affect the external sex characters. In contrast, the growth of the external sex characters of the male host was either acelerated (chela) or retarded (pleopod structures), but there was no parasitic effect on the testes. The mechanism for these castration effects appears to be some combination of a nutritional drain and/or a hormonal interference by the parasite.
TL;DR: Brain removal at appropriate times in the life cycle uniformly delayed or prevented the onset of all known ecdysone-mediated transitions and at the pupal-adult transformation.
Abstract: 1. Brain removal at appropriate times in the life cycle uniformly delayed or prevented the onset of all known ecdysone-mediated transitions. This effect was especially pronounced at larval-larval molts and at the pupal-adult transformation.2. Loose brains reduced but did not eliminate the delay induced by brain removal.3. Isolated larval abdomens never developed nor were they induced to do so by implantation of an active brain.4. Loose pupal brains retained their original commitment to diapause or not to diapause. This was true even when the loose brain was implanted into a brainless host pupa with an opposite diapause commitment.5. Larval brains effectively elicited the development of pupae, and conversely, pupal brains elicited the development of larvae.6. Prothoracicotropic activity was found in the brain but in no other ganglia.7. Extracts of Bombyx mori PTTH were inactive in Manduca in the concentrations tested.8. Consideration is given to several mechanisms which might mediate the development of bra...
TL;DR: Although mandibular glands of Callinectes sapidus do not store or secrete ecdysteroids, implants of the glands do accelerate molting in shrimp.
Abstract: This study examines the mandibular glands of Callinectes sapidus in both males and females. These pale yellow organs are located at the anterior end of the paired chitinous tendons that extend from the mandibles to the dorsal carapace. Channels of hemolymph subdivide the glands into cords. Each cord is composed of irreg ularly shaped cells with eccentric nuclei. The karyoplasm contains patches of condensed chromatin closely associated with the nuclear envelope. The most distinguishing feature of mandibular gland cells is two distinct types of smooth endoplasmic reticulum. Golgi complexes, mitochondria, and lipidlike inclusions are also prominent cytoplasmic organelles. The plasma membrane, when adjacent to hemolymph channels, exhibits varying degrees of convolution. These structural features are characteristic of other steroid-producing cells. Although mandibular glands do not store or secrete ecdysteroids, implants of the glands do accelerate molting in shrimp.
TL;DR: Tidal rhythms in swimming speed and phototaxis were measured in stage III zoeae of the crab Rhithropanopeus harrisii and it is hypothesized that the phototactic pattern represents a tidal rhythm in a shadow response used for predator avoidance.
Abstract: 1. Tidal rhythms in swimming speed and phototaxis were measured in stage III zoeae of the crab Rhithropanopeus harrisii. Larvae were captured in the Newport River estuary, North Carolina, and maintained under constant conditions in the laboratory.2. Swimming speed increases during rising tide with a maximum several hours after low tide, and decreases to a minimum about 2 hr after high tide. It is argued that this pattern is the basis of the endogenous tidal vertical migration, in which the larvae ascend on rising tides and descend on falling tides.3. The tidal rhythm in phototaxis consists of an increase in negative responsiveness which is strongest around the middle of the rising tide, and a decline to a minimum during falling tides. Positive phototaxis shows the opposite pattern. There is no convincing evidence that phototaxis participates in vertical migration. It is hypothesized that the phototactic pattern represents a tidal rhythm in a shadow response used for predator avoidance.
TL;DR: The results suggest that the disappearance of DOPA is linked to the sclerotization of periostracum, probably by way of quinone-tanning; tyrosine does not appear to participate in sclerOTization.
Abstract: 1. The periostracum of Mytilus edulis is a highly sclerotized protein structure as demonstrated by its low solubility in 13 M formic acid.2. The concentration of DOPA in periostracal hydrolysates is not uniformly distributed, but varies directly with protein solubility and logarithmically with the approximate age of the material.3. The results suggest that the disappearance of DOPA is linked to the sclerotization of periostracum, probably by way of quinone-tanning; tyrosine does not appear to participate in sclerotization.4. Sclerotization of DOPA-protein in Mytilus periostracum is compared to a similar process in the exoskeleton of the locust, Schistocerca gregaria.
TL;DR: Adult crabs removed from the blue mussel Mytilus edulis can be induced to respond to odor from the bay scallop Argopecten irradians concentricus, which supports the plastic "chemical search image" concept.
Abstract: 1. The pea crab Pinnotheres maculatus is a host-generalist symbiotic brachyuran. When subadult posthard and adult crabs are removed from the bivalve Mytilus edulis, Mytilus host odor increases their nonspecific movement as well as their location of the odor source. Odors from other previously recorded host species, however, generally do not affect their searching behavior.2. Such response specificity may be due to olfactory induction to their host. Adult crabs removed from the blue mussel Mytilus edulis can be induced to respond to odor from the bay scallop Argopecten irradians concentricus. Such induction supports the plastic "chemical search image" concept.3. Antennules are the principal sites of chemoreceptors used in host location.
TL;DR: In terrestrial isopods, different sensory cues initiate reproduction and moulting, indicating that the two processes are controlled by different physiological mechanisms, which interact via specific cues which coordinate and adjust the timing of theTwo processes.
Abstract: In terrestrial isopods, different sensory cues initiate reproduction and moulting, indicating that the two processes are controlled by different physiological mechanisms. A specific sensory trigger which initiates premoult is identified; it occurs well before conventional signs of premoult become evident. Specific coordinating mechanisms adjust the chronology of moulting and vitellogenesis under conditions promoting both processes. The first phase of vitellogenesis can occur either in intermoult or early premoult according to conditions and is considered to be independent of ecdysone. The second phase invariably occurs in late premoult and may be ecdysone-dependent. The relations between moulting and reproduction are regarded as separately controlled processes which interact via specific cues which coordinate and adjust the timing of the two processes. Implications of this concept are discussed.
TL;DR: Ambient water currents enhance internal flow and feeding in Styela montereyensis by forcing water through the branchial basket, and observed patterns of microdistribution probably result from differential mortality rather than habitat selection.
Abstract: Virtually all sessile suspension feeders rely on ambient water niovement to renew their food supplies and to carry away waste products and depleted water. In addition, species in imiany taxa have developed hydrodynamic mechanisms for exploiting the energy in the velocity gradient between the substratum and the moving water. For instaimce, exogenous currents induce flow through tubes, burrows, or internal chambers, and across external food-collecting surfaces ( Vogel, 1978) . Where currents are predictably unidirectional or bidirectional, colonial organisms frequently exhibit a perniatmeimt onientatioim which maximizes exposure to current (Wainwright and Dillon, 1969 ; Gnigg, 1972 ; Meyer, 1973). In areas with turbulent water or currents of unpredictable direction, orientation-independent mechanisnms are common (Warner, 1977). These are exemplified by animals with irregular or radial forms, such as sponges (Vogel, 1974) aimd some cninoids (Meyer, 1973) . While barnacles (Crisp and Stubbings, 1957) and brachiopods (La Bar bara, 1977) reorient actively when the current direction changes, certain sea anemones (Koehl, 1976) , conical stalked hydroids, and erect bryozoans allow currents to orient them passively (\Varner, 1977). Monniot ( 1967) has reported that the subtidal ascidian Microcosnios vulgaris normally orients its siphons up-current, but is capable of actively reorienting when suspended material becomes too dense. Surprisingly, evidence for induced flow has been presented for only one ascidian species. Sfyela plicafa ( Bretz, 1972). Styela montereyensis is a common stolidobranch ascidian in the Northeast Pacific. Johnson and Abbott ( 1972) have nedescnibed the species clearly, calling attention to morphological variation within and among local populations. The animal is anchored by an irregular tunic holdfast and held more or less erect in the water by a long stalk. Although both siphons are inserted anteriorly as in most ascidians, the larger incurrent siphon is recurved to point either posteriorly or yen trally. The entire body appears longitudinally plicated due to alternating thick and thin tunic areas. Preliminary diving observations indicated that the flexible stalk of Styela allows ambient currents to reorient the animal passively, facilitating induced flow. The mechanism by which this occurs operates regardless of the direction from which the current comes. This feature is appropriate since Styela characteristically occupies shallow water where the surge oscillates, sonietimes in unpredictable direc tions, every few seconds. In this paper, we docunment current-induced flow and describe aspects of orientation, morphological variation, habitat utilization, and larval habitat selection related to the use of currents by Styela.