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Gall ML, Holmes SP, Campbell H, Byrne M. Effects of marine heatwave conditions across the metamorphic transition to the juvenile sea urchin (Heliocidaris erythrogramma). MARINE POLLUTION BULLETIN 2021; 163:111914. [PMID: 33385800 DOI: 10.1016/j.marpolbul.2020.111914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 11/29/2020] [Accepted: 12/03/2020] [Indexed: 06/12/2023]
Abstract
For short development species, like the sea urchin Heliocidaris erythrogramma, the entire planktonic duration can be impacted by marine heatwaves (MHW). Developmental thermal tolerance of this species through metamorphosis was investigated over a broad range (7.6-28.0 °C), including temperatures across its distribution and MHW conditions. In controls (19.5-21.0 °C), 80% of individuals developed to metamorphosis at day 5, doubling to 10 days at 14.0 °C. The thermal range (14.4-21.2 °C) of metamorphosis on day 7 reflected the realised thermal niche with 25.9 °C the upper temperature for success (T40). By day 10, juvenile tolerance narrowed to the local range (16.2-19.0 °C), similar to levels tolerated by adults, indicating negative carryover effects across the metamorphic transition. Without phenotypic adjustment or adaptation, regional warming will be detrimental, although populations may be sustained by thermotolerant offspring. Our results show the importance of the metamorphic transition in understanding the cumulative sensitivity of species to MHW.
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Affiliation(s)
- Mailie L Gall
- School of Science and Health, Western Sydney University, Penrith, New South Wales 2751, Australia
| | - Sebastian P Holmes
- School of Science and Health, Western Sydney University, Penrith, New South Wales 2751, Australia
| | - Hamish Campbell
- School of Life and Environmental Sciences, The University of Sydney, New South Wales 2006, Australia
| | - Maria Byrne
- School of Life and Environmental Sciences, The University of Sydney, New South Wales 2006, Australia.
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Balogh R, Byrne M. Developing in a warming intertidal, negative carry over effects of heatwave conditions in development to the pentameral starfish in Parvulastra exigua. MARINE ENVIRONMENTAL RESEARCH 2020; 162:105083. [PMID: 32810717 DOI: 10.1016/j.marenvres.2020.105083] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 07/12/2020] [Accepted: 07/15/2020] [Indexed: 06/11/2023]
Abstract
Ocean warming and increasing incidence of marine heat waves (MHW) are having far-reaching impacts on coastal ecosystems. The small intertidal asterinid starfish, Parvulastra exigua, in south-eastern Australia, occurs in a global warming hotspot. Development occurs in the intertidal as this species lays eggs and has benthic larvae. The impact of temperature on development to the juvenile was determined over a broad temperature range (12-28 °C) encompassing temperatures experienced during the breeding season (16-20 °C) and cool (- 4 °C) and warm (+10 °C) extremes with the higher temperatures (24-28 °C) simulating a MHW. As the larva to juvenile transition involves major body reorganisation, we determined the impact of temperature on metamorphosis and formation of the normal five-armed juvenile. Development was faster at the higher temperatures 24-28 °C, but survival decreased from 1 to 5 days post fertilisation (dpf). Mortality was evident from day 15 at 22 °C and no larvae survived to 20 dpf at 28 °C. Thermal tolerance decreased over developmental time and the thermal optimum for 95% survival to the 20 day old juvenile spanned from 12 to 20.0 °C with the lethal temperature for 50% survival being 23.5 °C (5.5 °C above ambient). Juveniles reared in 26 °C were smaller, suggesting application of the temperature size rule. Increased temperature (22-26 °C) perturbed pentamery with three, four, six and no-armed juveniles present, contrasting with the low level of non-pentamerous individuals (<3%) in the cooler cultures and in nature (five populations surveyed). Despite the high thermal tolerance in premetamorphic stages, negative carry over effects were evident in the juveniles. This shows the importance of considering the whole of development in climate warming studies. As sea surface temperatures increase and heatwaves become more prevalent, habitat warming will be detrimental to P. exigua populations.
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Affiliation(s)
- Regina Balogh
- School of Life and Environmental Sciences, A11, The University of Sydney, NSW, 2006, Australia.
| | - Maria Byrne
- School of Life and Environmental Sciences, A11, The University of Sydney, NSW, 2006, Australia
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Chaparro OR, Cubillos VM, Montory JA, Navarro JM, Andrade-Villagrán PV. Reproductive biology of the encapsulating, brooding gastropod Crepipatella dilatata Lamarck (Gastropoda, Calyptraeidae). PLoS One 2019; 14:e0220051. [PMID: 31335878 PMCID: PMC6650077 DOI: 10.1371/journal.pone.0220051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 07/08/2019] [Indexed: 11/18/2022] Open
Abstract
Among calyptraeid gastropods, males become females as they get older, and egg capsules containing developing embryos are maintained beneath the mother’s shell until the encapsulated embryos hatch. Crepipatella dilatata is an interesting biological model considering that is an estuarine species and thus periodically exposed to elevated environment-physiological pressures. Presently, there is not much information about the reproductive biology and brooding parameters of this gastropod. This paper describes field and laboratory observations monitoring sex changes, brooding frequencies, sizes of brooding females, egg mass characteristics, and embryonic hatching conditions. Our findings indicate that C. dilatata is a direct-developing protandric hermaphrodite, changing from male to female when individuals were between 18 and 20 mm in shell length. At our study site in Quempillén estuary, females were found to be brooding almost continuously throughout the year, having an average maximum of 85% of simultaneous brooding, with a short rest from April through June. No relationship was found between the number of capsules per egg mass and the size of the brooding female. However, capsule size and the number of embryos and nurse eggs were strongly related to female size. The offspring hatched with an average shell length > 1 mm. About 25% of the hatched capsules were found to contain both metamorphosed (juveniles) and non-metamorphosed (veliger) individuals. The sizes of the latter were < 1000 μm. The length of hatching juveniles was inversely related to the number of individuals per capsule, which seems related to differences in the availability of nurse eggs per embryo. Although fecundity per reproductive event of this species is relatively low (maximum approx. 800 offspring per egg mass) compared with those of calyptraeid species showing mixed development, the overall reproductive potential of C. dilatata seems to be high considering that females can reproduce up to 5 times per year, protecting their encapsulated embryos from physical stresses until well-developed juveniles are released into the population, avoiding a dangerous pelagic period prior to metamorphosis.
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Affiliation(s)
- Oscar R. Chaparro
- Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, Valdivia, Chile
- * E-mail:
| | - Víctor M. Cubillos
- Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, Valdivia, Chile
- Laboratorio de Recursos Acuáticos y Costeros de Calfuco, Universidad Austral de Chile, Valdivia, Chile
| | | | - Jorge M. Navarro
- Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, Valdivia, Chile
- Centro Fondap de Investigación Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Universidad Austral de Chile, Valdivia, Chile
| | - Paola V. Andrade-Villagrán
- Centro de Investigación en Biodiversidad y Ambientes Sustentables (CIBAS), Facultad de Ciencias, Universidad Católica de la Santísima Concepción, Concepción, Chile
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Havird JC, Vaught RC, Weese DA, Santos SR. Reproduction and development in Halocaridina rubra Holthuis, 1963 (Crustacea: Atyidae) clarifies larval ecology in the Hawaiian anchialine ecosystem. THE BIOLOGICAL BULLETIN 2015; 229:134-142. [PMID: 26504154 DOI: 10.1086/bblv229n2p134] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Larvae in aquatic habitats often develop in environments different from those they inhabit as adults. Shrimp in the Atyidae exemplify this trend, as larvae of many species require salt or brackish water for development, while adults are freshwater-adapted. An exception within the Atyidae family is the "anchialine clade," which are euryhaline as adults and endemic to habitats with subterranean fresh and marine water influences. Although the Hawaiian anchialine atyid Halocaridina rubra is a strong osmoregulator, its larvae have never been observed in nature. Moreover, larval development in anchialine species is poorly studied. Here, reproductive trends in laboratory colonies over a 5-y period are presented from seven genetic lineages and one mixed population of H. rubra; larval survivorship under varying salinities is also discussed. The presence and number of larvae differed significantly among lineages, with the mixed population being the most prolific. Statistical differences in reproduction attributable to seasonality also were identified. Larval survivorship was lowest (12% settlement rate) at a salinity approaching fresh water and significantly higher in brackish and seawater (88% and 72%, respectively). Correlated with this finding, identifiable gills capable of ion transport did not develop until metamorphosis into juveniles. Thus, early life stages of H. rubra are apparently excluded from surface waters, which are characterized by lower and fluctuating salinities. Instead, these stages are restricted to the subterranean (where there is higher and more stable salinity) portion of Hawaii's anchialine habitats due to their inability to tolerate low salinities. Taken together, these data contribute to the understudied area of larval ecology in the anchialine ecosystem.
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Affiliation(s)
- Justin C Havird
- Department of Biological Sciences and Molette Laboratory for Climate Change and Environmental Studies, Auburn University, 101 Rouse Life Sciences Bldg., Auburn, Alabama 36849
| | - Rebecca C Vaught
- Department of Biological Sciences and Molette Laboratory for Climate Change and Environmental Studies, Auburn University, 101 Rouse Life Sciences Bldg., Auburn, Alabama 36849
| | - David A Weese
- Department of Biological Sciences and Molette Laboratory for Climate Change and Environmental Studies, Auburn University, 101 Rouse Life Sciences Bldg., Auburn, Alabama 36849
| | - Scott R Santos
- Department of Biological Sciences and Molette Laboratory for Climate Change and Environmental Studies, Auburn University, 101 Rouse Life Sciences Bldg., Auburn, Alabama 36849
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Calado R, Leal MC. Trophic Ecology of Benthic Marine Invertebrates with Bi-Phasic Life Cycles: What Are We Still Missing? ADVANCES IN MARINE BIOLOGY 2015; 71:1-70. [PMID: 26320615 DOI: 10.1016/bs.amb.2015.07.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The study of trophic ecology of benthic marine invertebrates with bi-phasic life cycles is critical to understand the mechanisms shaping population dynamics. Moreover, global climate change is impacting the marine environment at an unprecedented level, which promotes trophic mismatches that affect the phenology of these species and, ultimately, act as drivers of ecological and evolutionary change. Assessing the trophic ecology of marine invertebrates is critical to understanding maternal investment, larval survival to metamorphosis, post-metamorphic performance, resource partitioning and trophic cascades. Tools already available to assess the trophic ecology of marine invertebrates, including visual observation, gut content analysis, food concentration, trophic markers, stable isotopes and molecular genetics, are reviewed and their main advantages and disadvantages for qualitative and quantitative approaches are discussed. The challenges to perform the partitioning of ingestion, digestion and assimilation are discussed together with different approaches to address each of these processes for short- and long-term fingerprinting. Future directions for research on the trophic ecology of benthic marine invertebrates with bi-phasic life cycles are discussed with emphasis on five guidelines that will allow for systematic study and comparative meta-analysis to address important unresolved questions.
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Affiliation(s)
- Ricardo Calado
- Departamento de Biologia & CESAM, Universidade de Aveiro, Aveiro, Portugal.
| | - Miguel Costa Leal
- Department of Fish Ecology and Evolution, EAWAG: Swiss Federal Institute of Aquatic Science and Technology, Center for Ecology, Evolution and Biogeochemistry; Kastanienbaum, Switzerland.
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Padilla DK, McCann MJ, Glenn MM, Hooks AP, Shumway SE. Effect of food on metamorphic competence in the model system Crepidula fornicata. THE BIOLOGICAL BULLETIN 2014; 227:242-251. [PMID: 25572212 DOI: 10.1086/bblv227n3p242] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Food quality and quantity, as well as temperature, are all factors that are expected to affect rates of development, and are likely to be affected by expected climatic change. We tested the effect of a mixed diet versus a single-food diet on metamorphic competence in the emerging model species Crepidula fornicata. We then compared our results with other published studies on this species that examined time to metamorphic competence across a range of food concentrations and rearing temperatures. Ours was the only study to test the effects of single food versus a mixed diet on metamorphic competence for this species. Diet composition did not affect metamorphic competence or survivorship. Comparing results across studies, we found that the shortest time to metamorphic competence was typically found when the food availability per larva was the greatest, independent of rearing temperature. Unfortunately, some published studies did not include important metadata needed for comparison with other studies; these data included larval rearing density, food density, frequency of feeding, and rearing temperature. Mortality rates were not always reported and when reported were often measured in different ways, preventing comparison. Such metadata are essential for comparisons among studies as well as among taxa, and for the determination of generalizable patterns and evolutionary trends. Increased reporting of all such metadata is essential if we are to use scientific studies performed to their fullest potential.
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Affiliation(s)
- Dianna K Padilla
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794-5245;
| | - Michael J McCann
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794-5245
| | - Mica McCarty Glenn
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794-5245
| | - Alexandra P Hooks
- School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794-5000; and
| | - Sandra E Shumway
- Department of Marine Sciences, University of Connecticut, Groton, Connecticut 06340
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First principles of copepod development help explain global marine diversity patterns. Oecologia 2012; 170:289-95. [DOI: 10.1007/s00442-012-2313-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 03/16/2012] [Indexed: 10/28/2022]
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Henry JJ, Collin R, Perry KJ. The slipper snail, Crepidula: an emerging lophotrochozoan model system. THE BIOLOGICAL BULLETIN 2010; 218:211-229. [PMID: 20570845 DOI: 10.1086/bblv218n3p211] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Recent developmental and genomic research focused on "slipper snails" in the genus Crepidula has positioned Crepidula fornicata as a de facto model system for lophotrochozoan development. Here we review recent developments, as well as earlier reports demonstrating the widespread use of this system in studies of development and life history. Recent studies have resulted in a well-resolved fate map of embryonic cell lineage, documented mechanisms for axis determination and D quadrant specification, preliminary gene expression patterns, and the successful application of loss- and gain-of-function assays. The recent development of expressed sequence tags and preliminary genomics work will promote the use of this system, particularly in the area of developmental biology. A wealth of comparative information on phylogenetic relationships, variation in mode of development within the family, and numerous studies on larval biology and metamorphosis, primarily in Crepidula fornicata, make these snails a powerful tool for studies of the evolution of the mechanisms of development in the Mollusca and Lophotrochozoa. By bringing a review of the current state of knowledge of Crepidula life histories and development together with some detailed experimental methods, we hope to encourage further use of this system in various fields of investigation.
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Affiliation(s)
- Jonathan J Henry
- Department of Cell & Developmental Biology, University of Illinois, 601 S. Goodwin Ave, Urbana, Illinois 61801, USA.
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Stanley JA, Radford CA, Jeffs AG. Induction of settlement in crab megalopae by ambient underwater reef sound. Behav Ecol 2009. [DOI: 10.1093/beheco/arp159] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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11
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Effect of temperature on survival and infectivity of Echinostoma trivolvis cercariae: a test of the energy limitation hypothesis. Parasitology 2009. [DOI: 10.1017/s0031182000081920] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SUMMARYTrematode cercariae typically become unable to successfully infect a host many hours before they die. We examined the hypothesis that both time to 50% mortality and time to loss of infective capacity are controlled to the same degree by rates of energy expenditure, by determining the relative effects of temperature on both parameters. Infective capacity was assessed by exposing Echinostoma trivolvis cercariae of different ages to a suitable second intermediate host (the gastropod Biomphalaria glabrata) and counting 1–2 days later the number of metacercarial cysts formed. Temperature had a remarkably similar effect on time to 50% mortality and loss of infective capacity, supporting the hypothesis that both absolute and functional cercarial life-spans are limited by the rates at which energy stores are utilized.
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ZUPO VALERIO, PATTI FRANCESCOP. Laboratory spawning, larval development and metamorphosis of the marine snailNassarius reticulatus(L.) (Caenogastropoda, Nassariidae). INVERTEBR REPROD DEV 2009. [DOI: 10.1080/07924259.2009.9652286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Schneider DW, Stoeckel JA, Rehmann CR, Douglas Blodgett K, Sparks RE, Padilla DK. A developmental bottleneck in dispersing larvae: implications for spatial population dynamics. Ecol Lett 2003. [DOI: 10.1046/j.1461-0248.2003.00443.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Pechenik JA, Li W, Cochrane DE. Timing is everything: the effects of putative dopamine antagonists on metamorphosis vary with larval age and experimental duration in the prosobranch gastropod Crepidula fornicata. THE BIOLOGICAL BULLETIN 2002; 202:137-147. [PMID: 11971809 DOI: 10.2307/1543650] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The signal transduction pathway through which excess potassium ion stimulates the larvae of many marine invertebrates to metamorphose is incompletely understood. Recent evidence suggests that dopamine plays important roles in the metamorphic pathway of Crepidula fornicata. Therefore, we asked whether blocking dopamine receptors might prevent excess potassium ion from stimulating metamorphosis in this species. Surprisingly, the effects of the three putative dopamine antagonists tested (all at 10 microM) varied with exposure duration and the age of competent larvae. Chlorpromazine, a nonspecific dopamine antagonist known to have a number of other pharmacological effects, blocked the inductive action of excess potassium ion during the initial 5-8-h exposure periods in most assays, particularly for younger or smaller competent larvae. However, chlorpromazine in the absence of excess potassium ion also stimulated metamorphosis, particularly over the next 18 h, and worked faster on older competent larvae than on younger competent larvae. The specific D(1) antagonist R(+)-Sch-23309 had similar effects, blocking potassium-stimulated metamorphosis in short-term exposures and stimulating metamorphosis in longer exposures, particularly for older competent larvae. Although the specific D(2) antagonist spiperone (SPIP) blocked the inductive effects of excess potassium ion in only 1 of 6 assays during the first 6 h of exposure, it blocked metamorphosis in 2 of the assays during 24-h exposures. Our results indicate that dopamine receptors are involved in the pathway through which excess potassium ion stimulates metamorphosis in C. fornicata. In addition, the largely latent inductive effects of chlorpromazine, an inhibitor of nitric oxide synthase, suggest that endogenous nitric oxide may play a natural role in inhibiting metamorphosis in this species. Overall, our results would then suggest that exposing larvae of C. fornicata to excess K(+) leads to a shutdown of nitric oxide synthesis via a dopaminergic pathway, a pathway that can be blocked by some dopamine antagonists. Alternatively, chlorpromazine might eventually be stimulating metamorphosis by elevating endogenous cyclic nucleotide (e.g., cAMP) concentrations, again acting downstream from the steps acted on directly by excess K(+).
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Affiliation(s)
- Jan A Pechenik
- Biology Department, Tufts University, Medford, Massachusetts 02155, USA.
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Pechenik JA. Evaluating whether velar lobe size indicates food limitation among larvae of the marine gastropod Crepidula fornicata. JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY 2000; 252:255-279. [PMID: 10967336 DOI: 10.1016/s0022-0981(00)00245-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Disproportionately large feeding structures have been used to infer food limitation in some marine invertebrate larvae, but few studies have investigated whether other factors alter larval morphology in similar ways. In this study, larvae of Crepidula fornicata were reared either at five different food concentrations of Isochrysis galbana (clone T-ISO) at a single temperature (22 degrees C) (Experiments I and II); or on three different phytoplankton species (Isochrysis galbana, Dunaliella tertiolecta, and Pavlova lutheri) at both high and low concentrations at a single temperature (22 degrees C) (Experiment III); or at high and low concentrations of Isochrysis galbana at four different temperatures between 16 and 25 degrees C (Experiment IV). Shell lengths and velar lobe dimensions were determined for individual larvae at intervals to monitor relative rates of velar and shell growth. In addition (Experiment V), fast growing and slow growing larvae in Experiment I were examined separately to determine whether velar lobes developed at similar rates (relative to shell growth) for fast and slow growing larvae within individual cultures. In general, velar lobes grew significantly larger, relative to shell length, when larvae were reared at low food concentrations (P<0.0001); for larvae of similar shell length, the velar lobes of those fed 1x10(4) cells ml(-1) were on average 17.7% larger than those of larvae fed 18x10(4) cells ml(-1) of T-ISO. In contrast, larvae fed different phytoplankton species at equivalently high food concentrations did not differ in relative velum size (P=0.2666), even though shell growth rates differed significantly for larvae raised on the different diets, indicating substantial variation in food quality. We also found that relative rates of velum and shell growth differed among fast and slow growing individuals within treatments. Temperature had no significant effect on relative rates of velar and shell growth within the 16-25 degrees C range tested (P=0.121), but may have altered the relationship between food concentration and relative velar growth. These results indicate that dramatically reduced food concentration induces disproportionate growth in the velar lobes of C. fornicata, but that interpretation of data from field-collected individuals of this species will be made difficult by the potentially confounding effects of temperature, food quality, and differences in individual growth potential. Assessments of food limitation using morphological measurements for field-collected larvae will need to be supplemented with other indicators before convincing conclusions about the extent of food limitation in C. fornicata can be drawn.
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Collin R. Phylogeny of the Crepidula plana (Gastropoda: Calyptraeidae) cryptic species complex in North America. CAN J ZOOL 2000. [DOI: 10.1139/z00-058] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The taxonomy of Crepidula species with flat white shells is particularly difficult. These animals from the east coast of North America have generally been classified as a single species, Crepidula plana Say, 1822. Based on allozyme and developmental data, however, Hoagland (K.E. Hoagland. 1984. Malacologia, 25: 607-628; K.E. Hoagland. 1986. Am. Malacol. Bull. 4: 173-183) concluded that two species of flat white-shelled Crepidula live along the east coast of the United States, but she did not apply any name to the second species. Herein I use molecular techniques to characterize populations of flat white-shelled Crepidula species from Texas, Florida, Georgia, North Carolina, and |Massachusetts, and describe their morphology and development. DNA-sequence data support the existence of three species. One species is readily distinguished on the basis of morphology and development, but the other two are very similar. To clarify the nomenclature of these species, I designate neotypes for C. plana Say, 1822 and Crepidula depressa Say, 1822, and describe Crepidula atrasolea sp.nov.
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Hentschel BT. Complex Life Cycles in a Variable Environment: Predicting When the Timing of Metamorphosis Shifts from Resource Dependent to Developmentally Fixed. Am Nat 1999; 154:549-558. [PMID: 10561127 DOI: 10.1086/303263] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
To test models of the timing of and size at metamorphosis, researchers manipulate food at several times during the larval phase of an animal's complex life cycle. Data from diverse taxa show that the age at metamorphosis becomes resource independent (i.e., fixed) at some point during the larval phase. Although existing models have been modified to incorporate a fixed rate of development, none predicts when phenotypic plasticity in metamorphic timing is lost. A graphical model is presented that extends knowledge of a genotype's optimal age and size at metamorphosis in different environments in which resources remain constant throughout the larval phase (i.e., the genotype's reaction norm) to predict when development rate becomes fixed in response to resource variability during the larval phase. Model predictions concur with data from food-switching experiments on anuran tadpoles and barnacle nauplii. As interest in the timing of and size at metamorphosis expands from well-studied taxa (e.g., amphibians) to the many others that have complex life cycles, the predictive model provides a useful tool to design and improve experiments.
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