| 1. |
- Bok, Michael J., et al.
(author)
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Radiolar eyes of serpulid worms (Annelida, serpulidae) : Structures, function, and phototransduction
- 2017
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In: Biological Bulletin. - : University of Chicago Press. - 0006-3185 .- 1939-8697. ; 233:1, s. 39-57
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Journal article (peer-reviewed)abstract
- Fan worms, represented by sabellid and serpulid polychaetes, have an astonishing array of unusual eyes and photoreceptors located on their eponymous feeding appendages. Here we organize the previous descriptions of these eyes in serpulids and report new anatomical, molecular, and physiological data regarding their structure, function, and evolution and the likely identity of their phototransduction machinery. We report that, as in sabellids, serpulids display a broad diversity of radiolar eye arrangements and ocellar structures. Furthermore, the visual pigment expressed in the eyes of Spirobranchus corniculatus, a species of the charismatic Christmas tree worms, absorbs light maximally at 464 nm in wavelength. This visual pigment closely matches the spectrum of downwelling irradiance in shallow coral reef habitats and lends support to the hypothesis that these radiolar photoreceptors function as a silhouette-detecting “burglar alarm” that triggers a rapid withdrawal response when the worm is threatened by potential predators. Finally,we report on the transcriptomic sequencing results for the radiolar eyes of S. corniculatus, which express invertebrate c-type opsins in their ciliary radiolar photoreceptors, closely related to the opsin found in the radiolar eyes of the sabellid Acromegalomma interruptum.We explore the potential for a shared evolutionary lineage between the radiolar photoreceptors of serpulids and sabellids and consider these unique innovations in the broader context of metazoan eye evolution.
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| 2. |
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| 3. |
- Carey, N., et al.
(author)
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Sea Hare Aplysia punctata (Mollusca: Gastropoda) Can Maintain Shell Calcification under Extreme Ocean Acidification
- 2016
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In: Biological Bulletin. - : University of Chicago Press. - 0006-3185 .- 1939-8697. ; 231:2, s. 142-151
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Journal article (peer-reviewed)abstract
- Ocean acidification is expected to cause energetic constraints upon marine calcifying organisms such as molluscs and echinoderms, because of the increased costs of building or maintaining shell material in lower pH. We examined metabolic rate, shell morphometry, and calcification in the sea hare Aplysia punctata under short-term exposure (19 days) to an extreme ocean acidification scenario (pH 7.3, similar to 2800 mu atm pCO(2)), along with a group held in control conditions (pH 8.1, similar to 344 mu atm pCO(2)). This gastropod and its congeners are broadly distributed and locally abundant grazers, and have an internal shell that protects the internal organs. Specimens were examined for metabolic rate via closed-chamber respirometry, followed by removal and examination of the shell under confocal microscopy. Staining using calcein determined the amount of new calcification that occurred over 6 days at the end of the acclimation period. The width of new, pre-calcified shell on the distal shell margin was also quantified as a proxy for overall shell growth. Aplysia punctata showed a 30% reduction in metabolic rate under low pH, but calcification was not affected. This species is apparently able to maintain calcification rate even under extreme low pH, and even when under the energetic constraints of lower metabolism. This finding adds to the evidence that calcification is a largely autonomous process of crystallization that occurs as long as suitable haeomocoel conditions are preserved. There was, however, evidence that the accretion of new, non-calcified shell material may have been reduced, which would lead to overall reduced shell growth under longer-term exposures to low pH independent of calcification. Our findings highlight that the chief impact of ocean acidification upon the ability of marine invertebrates to maintain their shell under low pH may be energetic constraints that hinder growth of supporting structure, rather than maintenance of calcification.
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| 4. |
- Gewert, Berit, et al.
(author)
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Variability in Toxicity of Plastic Leachates as a Function of Weathering and Polymer Type : A Screening Study with the Copepod Nitocra spinipes
- 2021
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In: The Biological Bulletin. - : University of Chicago Press. - 0006-3185 .- 1939-8697. ; 240:3, s. 191-199
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Journal article (peer-reviewed)abstract
- The production and use of plastic over many decades has resulted in its accumulation in the world’s oceans. Plastic debris poses a range of potential risks to the marine environment and its biota. Especially, the potential hazards of small plastic debris and chemicals associated with plastic have not been extensively studied. When buoyant plastic is exposed to ultraviolet radiation, it will slowly degrade and leach chemicals into surrounding waters. These leachates can include additives, sorbed organic pollutants, and degradation products of the plastic polymers. While most hazard assessments have focused on studying adverse effects due to the uptake of plastic, toxicity studies of the leachates of plastics are less common. To begin to address this knowledge gap, we studied the acute toxicity of leachates from diverse plastics in the harpacticoid copepod Nitocra spinipes. Our results show that leachates caused a higher toxicity after plastic was exposed to ultraviolet light compared to leaching in darkness. We observed differences in toxicity for different polymer types: polyvinyl chloride and polypropylene resulted in the most toxic leachates, while polystyrene and poly[ethylene terephthalate] were least toxic. Furthermore, we observed increased toxicity of leachates from some plastics that had been weathered in the real marine environment compared to matching new materials. Our results indicate that both weathering condition and polymer type influence the toxicity of plastic leachates.
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| 5. |
- Lindmark, Max
(author)
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Integrative Approaches to Understanding Organismal Responses to Aquatic Deoxygenation
- 2022
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In: Biological Bulletin. - : University of Chicago Press. - 0006-3185 .- 1939-8697. ; 243, s. 85-103
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Journal article (peer-reviewed)abstract
- Oxygen bioavailability is declining in aquatic systems worldwide as a result of climate change and other anthropogenic stressors. For aquatic organisms, the consequences are poorly known but are likely to reflect both direct effects of declining oxygen bioavailability and interactions between oxygen and other stressors, including two-warming and acidification-that have received substantial attention in recent decades and that typically accompany oxygen changes. Drawing on the collected papers in this symposium volume ("An Oxygen Perspective on Climate Change"), we outline the causes and consequences of declining oxygen bioavailability. First, we discuss the scope of natural and predicted anthropogenic changes in aquatic oxygen levels. Although modern organisms are the result of long evolutionary histories during which they were exposed to natural oxygen regimes, anthropogenic change is now exposing them to more extreme conditions and novel combinations of low oxygen with other stressors. Second, we identify behavioral and physiological mechanisms that underlie the interactive effects of oxygen with other stressors, and we assess the range of potential organismal responses to oxygen limitation that occur across levels of biological organization and over multiple timescales. We argue that metabolism and energetics provide a powerful and unifying framework for understanding organism-oxygen interactions. Third, we conclude by outlining a set of approaches for maximizing the effectiveness of future work, including focusing on long-term experiments using biologically realistic variation in experimental factors and taking truly cross-disciplinary and integrative approaches to understanding and predicting future effects.
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| 6. |
- Lindmark, Max
(author)
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Mechanistic Temperature-Size Rule Explanation Should Reconcile Physiological and Mortality Responses to Temperature
- 2022
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In: Biological Bulletin. - : University of Chicago Press. - 0006-3185 .- 1939-8697. ; 243
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Journal article (peer-reviewed)abstract
- The temperature-size rule is one of the universal rules in ecology and states that ectotherms in warmer waters will grow faster as juveniles, mature at smaller sizes and younger ages, and reach smaller maximum body sizes. Many models have unsuccessfully attempted to reproduce temperature-size rule-consistent life histories by using two-term (anabolism and catabolism) Putter-type growth models, such as the von Bertalanffy. Here, we present a physiologically structured individual growth model, which incorporates an energy budget and optimizes energy allocation to growth, reproduction, and reserves. Growth, maturation, and reproductive output emerge as a result of life-history optimization to specific physiological rates and mortality conditions. To assess which processes can lead to temperature-size rule-type life histories, we simulate 42 scenarios that differ in temperature and body size dependencies of intake, metabolism, and mortality rates. Results show that the temperature-size rule can emerge in two ways. The first way requires both intake and metabolism to increase with temperature, but the temperature-body size interaction of the two rates must lead to relatively faster intake increase in small individuals and relatively larger metabolism increase in large ones. The second way requires only higher temperature-driven natural mortality and faster intake rates in early life (no change in metabolic rates is needed). This selects for faster life histories with earlier maturation and increased reproductive output. Our model provides a novel mechanistic and evolutionary framework for identifying the conditions necessary for the temperature-size rule. It shows that the temperature-size rule is likely to reflect both physiological changes and life-history optimization and that use of von Bertalanffy-type models, which do not include reproduction processes, can hinder our ability to understand and predict ectotherm responses to climate change.
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| 7. |
- Nezlin, Leonid P, et al.
(author)
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Transmitter-specific subsets of sensory elements in the prosobranch osphradium.
- 1994
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In: Biological Bulletin. - : University of Chicago Press. - 0006-3185 .- 1939-8697. ; 187, s. 174-184
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Journal article (peer-reviewed)abstract
- The osphradium is a putative chemosensory organ of aquatic molluscs. Previously, we identified two distinct types of primary sensory neurons in the osphradial ganglion of freshwater pulmonates, one immunoreactive to leucine-enkephalin (LEnk-ir) and another to FMRFamide (FMRFa-ir). In addition, NADPH diaphorase (NADPHd)-positive elements apparently producing nitric oxide (NO) were demonstrated in the organ. In the present study, prosobranch molluscs, which have retained the osphradial sensory neurons within the epithelium, were studied. Both types of peptidergic neurons, as well as NADPHd-positive cells, were found within the epithelium or in a basiepithelial position in the relatively simple osphradium of the mesogastropod Littorina littorea and in the complex, bipectinate osphradium of the neogastropod Buccinum undatum. Similar evidence was also obtained for another mesogastropod, Ampullarius sp. Transmitter-specific sensory cell types like those discovered in the osphradium are also present as single neuroepithelial cells in other organs of the mantle complex in prosobranchs and in the pelecypod Anodonta cygnea. We suggest that evolutionarily conservative, transmitter-specific types of epithelial and neuroepithelial sensory cells predated the osphradium, which developed as the site of their concentration, while retaining characteristic subsets of sensory neurons.
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| 8. |
- Svedberg, The, et al.
(author)
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The sedimentation constants of the respiratory proteins
- 1934
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In: The Biological Bulletin. - 0006-3185 .- 1939-8697. ; 66:2, s. 191-223
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Journal article (peer-reviewed)abstract
- 1. A systematic study of the sedimentation constants of the respiratory blood proteins throughout the animal kingdom has been carried out by means of the ultracentrifugal method. 2. Respiratory proteins enclosed in corpuscles have low sedimentation constants. The following values were found for erythrocruorin: capitellide worms and Cyclostomata, 2.1 x 10-13; glyceride worms and lamellibranchians, 3.5 x 10-13; holothurians, 2.6 x 10-13. Hemoglobin characterized by the sedimentation constant 4.4 x 10-13 occurs only in the five higher classes of the vertebrates, viz., Mammalia, Aves, Reptilia, Amphibia, Pisces. Among the reptiles and amphibians an association product of hemoglobin with sedimentation constant 7.1 x 10-13, probably representing a doublet, was often found. This product was never observed in the other classes of the vertebrates. 3. Respiratory proteins dissolved in the plasma have, as a rule, high sedimentation constants. The only exception is the erythrocruorin of the Chironomus larvæ, which has the constant 2.0 x 10-13. All polychæte worms and hirudineans with dissolved pigment have the constant 57.5 x 10-13 (erythrocruorin and chlorocruorin) . A dissociation product of constant 11.7 x 10-13 (probably 1/16 of the normal molecule) is sometimes found. The oligochæte worms have a variety of erythrocruorin of slightly higher constant, 61.9 x 10-13. The crustaceans show as a rule two sedimentation constants, 16.9 and 23.5 x 10-13. The former one, which occurs both in erythrocruorins and hemocyanins, probably represents a molecular weight of one-half of the latter. Species characterized by the latter constant have hemocyanin and give a mixture of both constants in alkaline solution, thus demonstrating the dissociation into half molecules. One crustacean species (Calocaris macandreae) has a hemocyanin constant of 34.0 x 10-13. This sedimentation constant is also characteristic of the hemocyanin of the scorpion (Euscorpius carpaticus). The xiphosuran (Limulus polyphemus) has a hemocyanin of the same constant, but its blood contains two more hemocyanin varieties of constants 16.5 and 59.1 x 10-13 and a dissociation product of constant 6 x 10-13. The erythrocruorin of the gastropods has the same constant, 33.8 x 10-13. The normal hemocyanin of the gastropods, on the other hand, is characterized by the constant 100.1 x 10-13. It forms an association product of constant 133.6 x 10-13 and two dissociation products of constants 16.2 and 61.9 x 10-13 (probably 1/2 and 1/8 of the normal molecule respectively). The constant 60.9 x 10-13 is also found in the amphineuran hemocyanin (Tonicella marmorca). The cephalopods show two constants, 56.2 x 10-13 for the decapods and 50.1 x 10-13 for the octopods. The latter constant has not been observed in any other place and is the only sedimentation exclusively characteristic of an animal group. 4. The significance of the data collected in the present investigation cannot be fully understood until a sufficient number of pH-stability curves and sedimentation equilibrium measurements have been made on respiratory proteins. The few determinations of this kind so far available, however, seem to indicate that all native proteins form a closed system in which only a very limited number of mass and shape types are stable. Reversible association and dissociation reactions take place easily when the pH of the solution is slightly changed. Within a well-defined animal group all species have as a rule respiratory pigments of the same sedimentation constant (or constants) and dissociate in a similar way. Biological kinship, therefore, is usually accompanied by identity in the sedimentation constants. On the other hand, owing to the small number of different constants possible, the same constant must of necessity occur in different animal groups.
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| 9. |
- Webster, S. G., et al.
(author)
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Putative molt-inhibiting hormone in larvae of the shore crab Carcinus-maenas L. - an immunocytochemical approach
- 1991
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In: The Biological Bulletin. - Chicago : University of Chicago Press. - 0006-3185 .- 1939-8697. ; 180, s. 65-71
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Journal article (peer-reviewed)abstract
- Immunocytochemical investigations of the eyestalk of Carcinus maenas zoeal larval stages, using an antiserum directed against putative Carcinus molt-inhibiting hormone (MIH), revealed immunopositive neuronal structures. These structures included perikarya associated with the medulla terminalis X-organ, parts of the sinus gland tract, and the neurohemal organ-the sinus gland. Apart from an increase in volume of the sinus gland between zoeal stage I and II, no striking changes in the topography or morphology of the MIH neurosecretory system were observed. Immunopositive structures were found in similar locations to those seen in adult crabs. Our results suggest that the control of molting by MIH in crustacean larvae may be similar to the currently accepted model of molt control in adult decapod crustaceans.
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| 10. |
- Dahlgren, Thomas G., 1963, et al.
(author)
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Molecular phylogeny of the model annelid Ophryotrocha
- 2001
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In: Biological Bulletin. - 0006-3185. ; 201:2, s. 193-203
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Journal article (peer-reviewed)abstract
- Annelids of the genus Ophryotrocha are small opportunistic worms commonly found in polluted and nutrient-rich habitats such as harbors. Within this small group of about a, 40 described taxa a large variety of reproductive strategies are found, ranging from gonochoristic broadcast spawners to sequential hermaphroditic brooders. Many of the species have a short generation time and are easily maintained as laboratory cultures. Thus they have become a popular system for exploring a variety of biological questions including developmental genetics, ethology, and sexual selection. Despite considerable behavioral, reproductive, and karyological studies, a phylogenetic framework is lacking because most taxa are morphologically similar. In this study we use 16S mitochondrial gene sequence data to infer the phylogeny of Ophryotrocha strains commonly used in the laboratory. The resulting mtDNA topologies are generally well resolved and support a genetic split between hermaphroditic and gonochoristic species. Although the ancestral state could not be unambiguously identified, a change in reproductive strategy (i.e., hermaphroditism and gonochorism) occurred once within Ophryotrocha. Additionally, we show that sequential hermaphroditism evolved from a simultaneous hermaphroditic ancestor, and that characters previously used in phylogenetic reconstruction (i.e., jaw morphology and shape of egg mass) are homoplasic within the group.
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