These results were given by both accelerometer and acoustic data. For example, when the shell is closed and placed on the bottom, the pitch angle is 90. PHILIP, GRAEME M. Data obtained from a single great scallop exposed for 2 hours to the higher cell concentration (500 000 cells L-1) of A) Heterocapsa triquetra control treatment and B) the toxic Alexandrium minutum. Pecten philippii Rcluz, 1853 accepted as Aequipecten commutatus (Monterosato, 1875) Rank. Differences between the two algal diets were investigated using the non-parametric Wilcoxon signed rank test for each concentration (for example, high concentration of toxic algae vs high concentration of control algae for the total number of movements) because assumptions of normality of data and equal variance tests were not validated. PLoS ONE 11(8): Fig 3 shows a representative visualization of typical scallop valve movement types (expulsion, displacement, closure, and swimming) simultaneously obtained from acoustic (Fig 3A) and accelerometer (Fig 3B) recordings. S1 Fig. Calico scallops that settle in the spring generally reach a size of 30 to 35 millimeters in shell height by the following fall and are fully able to reproduce. While bay scallop shells are solid in color, the upper shell of a calico scallop is a patchwork of red and pink. Adv. Each individual was assigned to a control treatment on the first day and then assigned to the matching toxic treatment on the second day. Kellogg, Drew, and Belding use P. irradians. These data were also compared with visual observations or images taken by cameras, which were recorded simultaneously. This unique, delightful flavor makes scallops a tasty ingredient in seafood scampi. The scallops natural sweetness is never on display so clearly as before its cooked. I of Catalogue of the type and figured specimens of fossils, minerals, rocks, and ores in the Department of Geology, United States National Museum, Index of condition and percent solids of raft-grown oysters in Massachusetts, Micropaleontology and stratigraphy of a deep well at Niceville, Okaloosa County, Florida, Characters and observations on new genera and species of Mollusca and Conchifera collected by Mr. Cumming, Monograph of the genus Pecten. What are Bay Sea and calico varieties of? (Log in options will check for institutional or personal access. Argopecten gibbus. Two members of the scallop genus Pecten (Bivalvia: Pectinidae) occur in European waters. What is related to Pecten Gibbus? Proof of ancient seas is, in part, from the marine fossils that accumulated with the bottom sediments. Due to their potential sensitivity (e.g., environmental changes), bivalves through their valve movements can be monitored to detect harmful algal blooms. On the basis of the materials analyzed thus far, the evolution (both phyletic change and splitting) of the stock has been faster on the Atlantic side of the Americas than on the Pacific side, with the living Pacific species resembling late Miocene and early Pliocene Atlantic species. Sonderdruck Mitt. By the end of the Miocene, on the eastern side of the Americas, this variable species had split, giving rise to a primitive bay scallop, A. anteamplicostatus (Mansfield), that, like the living bay scallop (its phyletic descendant), was probably ecologically restricted to the semienclosed waters of bays and sounds, and to another species, A. vicenarius (Conrad), probably restricted to open marine waters like the living calico scallop. Activities Complete the following activities: 1. Ziegler, Willi One, without scallop, nor alga, served as an acoustic control to record ambient noise and validates detected sounds from the three other tanks. Lindstrm, Maurits Sci. A silicone plate (0.5 cm thick) on the bottom of the tank prevented sound emissions due to friction between hard body parts and the glass when animals moved. Moreover, for real-time monitoring, these loggers usually require connecting cables, which limit this technique to sessile species. Aurlie Jolivet, Harmful algal blooms produced by toxic dinoflagellates have increased worldwide, impacting human health, the environment, and fisheries. Assoc. PLEASE ANSWER THE FOLLOWING ASAP! An edible saltwater clam, it is native to the northwest Atlantic from Cape Cod to the Gulf of Mexico . Analyses of acoustic recordings taken in the empty control tank confirmed the absence of any significant acoustic signal outside the experimental tanks during each sessions and the sound transfer from scallop movement from a tank to another. Alexandrium minutum is particularly well established in marine European coastal waters [1, 4]. During the Pleistocene, A. nucleus, a tropical bay scallop, is inferred to have split from A. gibbus and to have become morphologically convergent on the true bay scallop, A. irradians. Furthermore, the increased movements detected in this study (closures and expulsion) may serve as a reaction to reject invasion by A. minutum cells from the mantle cavity, clean the gills, or refresh the water flowing inside the animal, especially expulsion, which allows the expulsion of captured material [42]. Valve movements are closely related to vital activities, such as respiration, feeding, excretion, and moving. 1.8 million years ago Pecten gibbus are index fossils found in the Cenozoic Era in the Quaternary period, 1.8 million years ago. I of Cenozoic Muricidae of the western Atlantic region, Chicoreus (Phyllonotus), part III of Cenozoic Muricidae of the Western Atlantic region, Genera of the Bivalvia: A systematic and bibliographic catalogue, Two FORTRAN II programs for the univariate and bivariate analysis of morphometric data, Paleontology of the marine Tertiary formations of Oregon and Washington, Late Cenozoic pelecypods from northern Venezuela, The calico scallop community in North Carolina, The edible clams, mussels and scallops of California, Mollusca and Crustacea of the Miocene formations of New Jersey, The evolution of the swimming habit in the Lamellibranchia, Mus. V, Tellinacea, Solenacea, Mactracea, Myacea, Molluscoidea, p. 185249 (1928); 142-F, Pt. Scallops were experimentally exposed to three ecologically relevant concentrations of A. minutum for 2 hours. Rept. However, no correspondence could be found between any of these parameters and the event detection. It would be interesting to investigate the impact of A. minutum on the valve responses of scallops over a longer period of exposure, to better evaluate this absence of effect at low-medium concentrations and possibly detect an impact after a few hours of exposure. Your email address will not be published. Has unequal wings 3. Biodiversity. Finally, accelerometer data showed that exposure to A. minutum caused changes in the opening amplitude of expulsion compare to exposure of H. triquetra at 500 000 cells L1 (Wilcoxon test, p = 0.03, Fig 4A4). The number of each type of valve movement and their sound intensity, opening duration, and valve-opening amplitude were measured. The animals were fed every 2 days with Isochrysis sp. After a two-week pelagic (open water) larval phase the juvenile scallops, commonly called spat, settle out of the water and attach to hard surfaces, usually older calico scallop shells. No other valve movement patterns, such as acceleration, mean duration, or mean valve gape for a movement type, were affected by exposure to the toxic treatment compare to the control treatment at either concentration (Wilcoxon tests, p > 0.05). Black dots represent algae added in the tank at the beginning of the trial. This study highlighted that both swimming and displacement events were always detectable in acoustic recordings, unlike closures and expulsions that were the behaviors significantly different from the control at high concentrations. 526. 1952, Catalogue of marine Mollusca added to the fauna of New England during the past ten years, A study of the family Pectinidae, with a revision of the genera and subgenera, Murex, sensu stricto, pt. These four movement types were detected and characterized by accelerometry and acoustics, demonstrating its potential for monitoring scallop valve movements. PDF NATURAL HISTORY OF THE BAY SCALLOpl - National Oceanic and Atmospheric I-XIV, 1-303, Tab. The postulated phylogeny shows a poorly known species, Argopecten species b, in the early middle Miocene (Oak Grove Sand), that is apparently very near the origin of the stock. PLOS ONE promises fair, rigorous peer review, The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. It lives an average of 20 months, with a maximum life expectancy of 24 months (Allen and Costello 1972). Three of them were used to run experiments with scallops. Pecten gibbus Name Synonyms Aequipecten gibbus (Linnaeus, 1758) Argopecten gibbus (Linnaeus, 1758) Chlamys gibbus (Linnaeus, 1758) Ostrea gibba (Linnaeus, 1758) Pecten gibbus (Linnaeus, 1758) Pecten gibbus (Linnaeus, 1758) Homonyms Pecten gibbus (Linnaeus, 1758) . They pump water across gills to filter out food particles and use their large adductor muscle to open or close their shells. One hundred and twelve species are reported from this community of which only two, Polydora websteri and Cerato- nereis tridenlata, can be loosely considered as borers. Bivalvia (Mollusca) of the Gulf of Mexico, Pp. The shell was found by Soviet scientists and hoarded by Russian collectors until it existence was announced to the world in 1990. ASW,USA. The sanitary threshold defined by the French harmful algal monitoring network REPHY developed by IFREMER is 10 000 cells L-1. Hostname: page-component-7fc98996b9-rscnt 83, A population study of the Tasmanian commercial scallop, Notovola meridionalis (Tate) (Lamellibranchiata, Pectinidae). Methods that measure valve activity require bivalve-attached sensors and usually connected cables to data . A piece of Velcro (1 cm2) was glued to the upper (left/flat) valve of each scallop and to a sealed data logger using glue (Araldite 90 s epoxy, Huntsman Advanced Materials). Argopecten gibbus Name Homonyms Pecten gibbus (Linnaeus, 1758) Bibliographic References. 1.) Marine and Freshwater Res. ), Observations on the epifauna of the deep-water muds of the Clyde Sea area, with special reference to, Influence de la fixation pleurothtique sur la morphologie des mollusques acphales dimyaires: Paris, Thses prsentes la Facult des Sciences, The Tertiary and Quaternary pectens of California: U. S. Geol. These observations suggest that P. maximus keep a stable valve gape to filter even in the presence of the toxic algae but reacts, and may protect itself, during movements that require an increased valve gape in order to, for example, expel pseudofaeces more efficiently. Retained Earnings 462 . The King Scallop (Pecten maximus) is the second most valuable shellfish species landed in Scotland after Nephrops, valued around 23 million in 2015. Are Pecten maximus and Pecten jacobaeus different species? - ResearchGate When exposed to a concentration of 500 000 cells L-1, both methods detected a significant (by a factor of 2) increase in the number of movements in the presence of A. minutum compared to the control diet H. triquetra (p = 0.034 and p = 0.021 for accelerometer and acoustic, Fig 4A1 and 4B1). e0160935. 3, On some fossil and recent shells of the United States, Descriptions of a new genus, and of twenty-nine new Miocene, and one Eocene fossil shells of the United States. This study seeks to determine evolutionary relationships within the Argopecten gibbus stock by working back through the fossil record from a model of the morphological and ecological relationships of living species and subspecies. They clearly appeared as potential parameters to follow in order to characterize the presence of an Alexandrium sp bloom. Required fields are marked *. VI, Pteropoda, Opisthobranchia, and Ctenobranchia, p. 251435 (1937 [1938]); 142-G, Pt. Scientific theories on evolution and the fossil record change over time because new animals are discovered, or studies more closely, adding to current theories or changing them, like the pecten gibbus being related to things originally not suspected. Nat. and Enumeratio molluscorum Siciliae cum viventium tum in tellure tertiaria fossilium, quae in itinere suo observavit. Over the last few decades, toxic marine dinoflagellate blooms have become more frequent worldwide, inducing dramatic human health and economic effects [13]. outcrops, South Carolina, Stratigraphy of the Neogene deposits, lower Neuse Estuary, North Carolina, Paleoecology of the Choctawhatchee deposits, Jackson Bluff, Florida, Invertebrate megafossils of the Belvedere expedition to the Gulf of California, Estuaries and lagoons in relation to continental shelves, Estuaries: Washington, D.C., Am. Sounds play an important role in detecting early signs of animal stress [27, 28]. Harmful algal blooms often begin in spring when winter storms are over and the sea calmer. Tran et al. Summary of detected movement number found by both accelerometer and acoustics methods for each recording. Epibionts were removed from the outer shell surface and the scallops acclimated to laboratory conditions 4 weeks before the start of the experimental sessions. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); 2012-2023 On Secret Hunt - All Rights Reserved They swim by quickly opening and closing their shells, propelling themselves forward. To compare the effect of the concentration (for example comparison between high vs medium vs low concentrations of toxic algae for the total number of movements), a Welchs ANOVA test was applied. Here, ax, ay, and az are dynamic acceleration values derived from raw x, y, and z acceleration data [37]. The bottom of each tank was equipped with a silicone plate (0.5 cm thick) to prevent sound emissions due to the friction of shells on the glass when the animals moved. In our study, the valve gape of expulsion was significantly different between the two algal treatments at the higher concentration. Chapter 5 Neurobiology and behaviour of the scallop Depending on the species, suspension-feeding bivalves do not have the same abilities to tolerate and accumulate paralytic toxins [911]. These which operate in sequence to bring about downward movement. Fossil Evidence - Phylum Mollusca Several areas in Brittany, France, are subjected to yearly intense blooms of A. minutum. There are more than 400 species of scallops found around the world. While bay scallop shells are solid in color, the upper shell of a calico scallop is a patchwork of red and pink. The species name Argopecten vicenarius (Conrad), unused since 1898, is reinstated as the only available name for an important taxon occurring in the Caloosahatchee Marl of Florida and the Waccamaw Formation of the Carolinas. v. Born's Testaceis Musei Caesarei Vindobonensis, Supplementary report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. 1 of A historical review of the mollusks of Linnaeus, The habits, anatomy, and embryology of the giant scallop (Pecten tenuicostatus, Mighels), Stratigraphy and paleontology of the late Neogene strata of the Caloosahatchee River area of southern Florida, Neogene stratigraphy of southwestern Florida, The Waccamaw and Croatan deposits of the Carolinas, S.C. State Devel. American Fisheries Society Special Publication 16. vii + 277. Field Trip, Feb. 1968, Pliocene Mollusca of southern Florida, with special reference to those from North St. Petersburg, Mission zoologiqueMalacologie (1912) : Paris, Macro-invertebrate assemblages as indicators of sedimentary environments in the east Mississippi delta region, Macro-invertebrate assemblages of central Texas coastal bays and Laguna Madre, Ecology and distributional patterns of marine macro-invertebrates, northern Gulf of Mexico, Recent sediments, northwest Gulf of MexicoA symposium summarizing the results of work carried on in Project 51 of the American Petroleum Institute, 19511958, Les lamellibranches de l'expedition du Siboga. While bay scallop shells are solid in color, the upper shell of a calico scallop is a patchwork of red and pink. III, Lucinacea, Leptonacea, Cardiacea, p. 101149 (1926); 142-D, Pt. Fish and Game, Note on Pecten (Chlamys) muscosus Wood, 1828, and P. exasperatus Sow., 1842, The molluscan fauna of the Alum Bluff group of Florida, U. S. Geol. The total number of movements and the number of expulsion, displacement, and closure events were stable during the 2 hours for all exposure conditions. They range from 70.6 to0.0 years old. Calico scallops are generally smaller than bay scallops with maximum shell heights between 40 and 60 millimeters (1.6 to 2.4 inches). 06.03 Origin and Evolution of Life: Pecten Gibbus, Sharp scales located on the lower surface of this fossils ribs, describe any known or theorized behavioral characteristics, describe its biological evolution and phylogeny. Umur, ukuran, umur: Argopecten Gibbus mencapai 40 hingga 60 mm (1,6 hingga 2,4 inci) Tinggi cangkang dan sekitar 80 mm (3,2 inci) panjang shell. [31] recorded P. maximus valve movements to evaluate the potential use of these sounds in monitoring environmental changes. Pecten irradians Lamarck. Report fish kills, wildlife emergencies, sightings, etc. Soc., 2nd Ann. We thank Cline Liret, Dominique Barthlmy, Sbastien Delaporte, Marie-Pierre Pelecq, and the aquariology staff of the public aquarium Ocanopolis in Brest for their technical support. This species evolved phyletically through A. nicholsi (Gardner) of the Shoal River Formation and A. choctawhatcheensis (Mansfield) of the Arca Faunizone into A. comparilis (Tuomey & Holmes) of the upper Miocene (Tamiami, Pinecrest, Duplin, and Yorktown Formations). Thus far, no data are available for acoustic changes in P. maximus valve movement in the presence of environmental variations or stressors. Activity stability over the 2 hours recording. Age, Size, Lifespan: Argopecten gibbus reaches 40 to 60 mm (1.6 to 2.4 inches) shell height and approximately 80 mm (3.2 inches) in shell length. A) Accelerometer and B) acoustic data showing movement responses in Pecten maximus exposed to three concentrations of Heterocapsa triquetra (light grey bars, control) or toxic Alexandrium minutum (dark grey bars) for 2 hours (mean SE, n = 9 per concentration). After approximately 1 minute of homogenization, sound was recorded for 2 hours, which corresponds to the time for observing a thin algal layer on the silicone plate as a result of algal sedimentation since the sea water exchange was turned off. Casting a Genetic Light on the Evolution of Eyes, Science, 313, 5795, (1914-1918 . Nat. The anonymous reviewers are acknowledged for their helpful suggestions and comments on this manuscript. During the recording sessions, four behaviour types were identified (Fig 2): displacement was the result of an increase in the opening amplitude before rapid shell closure inducing shell displacement (variation in pitch and roll angles > 3); swimming was a succession of shell displacement events associated with water expulsion, with the valve reopening quickly between flapping (time between displacement events < 1 second); expulsion was a rapid valve adduction associated with the expulsion of faeces, water, and other substances from the mantle cavity but not sufficient to displace the shell (variation in pitch angle > 3 and variation in roll angle < 3); and closures were observed as minor contraction movements to return to an optimal opening amplitude (variation in pitch and roll angles < 3). It is split into Quaternary Period, Pecten gibbus, and Terti MyIQIsHigh MyIQIsHigh 05/01/2020 Biology College answered expert verified The table shows index fossils. Further experiments, with longer exposure periods would also be necessary in order to confirm the results of the effect of A. minutum on swimming and displacement behaviors. Volume 43 Issue S3: Paleontological Society Memoir Issue S3: Paleontological Society Memoir 3. Corrections, Expressions of Concern, and Retractions. Camp (eds. Philadelphia Proc., 3rd ser. On the Pacific coast of North America, P. : a fossil consisting of a stony mass that entered a hollow natural object (such as a bivalve shell) in the form of mud or sediment, was consolidated, and remained as a cast after dissolution of the mold. The hydrophones were suspended at the centre of the tank 13 cm above the silicone plate. Four behaviours were identified: closures, expulsion, displacement, and swimming. Mucrospirifer mucronatus, Devonian Period, 420-360 mya. Thus, the raw values of these features do not represent exactly sounds that would be recorded under field conditions. Naturf. Only few recent studies examined the effects of harmful algal blooms on marine biological sound production. Briefly, an approximation of absolute acceleration resulting only from dynamic acceleration in each of the three dimensions was extracted from each axis after removing the static acceleration using a running mean of 3 s [36]. Belgique Mm., ser. Regarding P. maximus and previous acoustic studies, it has been shown that escape responses (swimming or displacement) and adduction movements produce specific sounds [26, 31]. Calico and bay scallops are bivalve (two-shells) molluscs in the Pectinidae family and are similar in both anatomy and life history. 5 of, Results of the Puritan-American Museum of Natural History Expedition to western Mexico: Am. State Geologists, 44th Ann. IX, Index to chapters A-H, p. 657709 (1950), Additions to the molluscan fauna of the Alum Bluff group of Florida, Pelecypoda, pt. 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Total loading time: 0 The majority of scallops are landed by dredgers, but approximately 5% of scallops are caught by hand-dive or passive fisheries ( Marine Scotland, 2018 ). Turgeon, D. D., A. E. Bogan, E. V. Coan, W. K. Emerson, W. G. Lyons, W. Pratt, et al., 1988: Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks. Is described as a comb describe any known or theorized behavioral characteristics 1. Thus far, accelerometry and passive acoustics do not seem to allow the detection of such concentrations in the water, but this approach should be continued to define the behavioural responses of P. maximus to A. minutum over a longer period of time and assess whether a response can be detected over time at a concentration of 10 000 cells L-1. Why is natural selection a mechanism for biological change? ASE,Norocco. Thus, despite the fact that closure and expulsion behaviors were the quietest identified with passive acoustics, a significant increase in the number of events was observed with acoustics after A. minutum exposure. With regard to nomenclature, the name Argopecten is shown to be a senior synonym of Plagioctenium; the generic name Aequipecten is rejected for American species related to Argopecten gibbus; and it is concluded that the generic name Chlamys, sensu lato, is better applied as the subfamily name Chlamydinae. 2, The function of zigzag de-flexions in the commissures of fossil brachiopods. Several parameters, such as the maximum opening amplitude during the movement, the rotation of the shell, and the proximity or position of the scallop next to the hydrophone, could explain why closure and expulsion were not always detected. Pecten gibbus ing of the land surface, sediments were deposited on the ocean floor. Can Subclass Override The Static Methods Of Superclass? Pecten is related to other scallops. Calico scallops have several blue eyes located in the mantle cavity along the edge of each shell, which they use to detect shadows and movement. Feature combination analyses of signal shape, sound intensity, and duration, would result to a reliable distinction between the four behavior types in the field where no visual validation is possible. Species Description: Valves of Argopecten gibbus are deep and generally equal, with 17-23 (usually 20) deep, radiating ribs (Allen and Costello 1972). Argopecten gibbus (Linnaeus, 1758) - GBIF Differences between samples were studied and evaluated by means of morphometric data consisting of 70 measurements and form ratios of the outline, ligamenture, and musculature of each valve. In correspondence, Dr. Paul Bartsch BUTCHER; pp. AN W , U SA FIRS/S114 Scallops V 3,3 Adult phase CONTENTS 2DISTRIBUTION7 2,1Total area7 2,2Differential distribution7 2,21Spawn, larvae and juveniles7 2,22 Adults* 2.3 Determinants of distribution changes8 2.4 Hybridization* 3BIONOMICS AND LIFE HISTORY8 Pecten gibbus (Linnaeus, 1758) by Melissa Casey - Prezi Pecten - an overview | ScienceDirect Topics Once you have your total number of ridges, divide the number by 365. Acoustically, no difference was detected in intensity or event duration for the different behaviours between the two algal diets. Assessing the threshold concentration at which significant changes can be observed would also be valuable. Valve movement recorded by accelerometry. As a result of this rapid growth and early maturation, groups of scallops, or cohorts, may overlap and scallops of many different sizes may occupy a bed at any given time. The typical life span of a calico scallop, 18 months, is longer than that of a bay scallop and some . I of Mollusca from the Miocene and lower Pliocene of Virginia and North Carolina, Catalogue of the marine Pliocene and Pleistocene Mollusca of California and adjacent regions, A new subspecies of Pecten (Plagioctenium) gibbus (Linn), Pecten (Plagioctenium) gibbus portusregii, new name, Safe landing on Sable, isle of 500 shipwrecks, The Phanerozoic time-scaleA symposium dedicated to Professor Arthur Holmes. The valve activity of P. maximus was different when exposed to high concentrations (500 000 cells L-1) of A. minutum compared to the non-toxic dinoflagellate Heterocapsa triquetra; the number of valve movements increased, especially closure and expulsion, which were detected acoustically. Age, Size, Lifespan: Argopecten gibbus reaches 40 to 60 mm (1.6 to 2.4 inches) shell height and approximately 80 mm (3.2 inches) in shell length. 1940, Evolutionary processes and taxonomy with special reference to grades, Biometrical methods in the study of invertebrate fossils, International Commission on Zoological Nomenclature, International Code of Zoological Nomenclature, adapted by the XV International Congress of Zoology, International Trust for Zoological Nomenclature, Phylogeny of the Pelecypoda. Argopecten irradians, formerly classified as Aequipecten irradians, common names Atlantic bay scallop or bay scallop, is a species of scallop in the family Pectinidae. Genetic distances between these species were estimated using both allozyme electrophoresis and mitochondrial DNA . The four valve movement types were represented by short spikes and perceived by the human ears as shorts cracks. Swimming and displacement events had a similar mean sound intensity (95.0 2.5 dB re 1 Pa vs. 94.5 2.5 dB re 1 Pa, respectively), as did expulsion and closure events (80.5 1.7 dB re 1 Pa vs. 81.5 1.9 dB re 1 Pa, respectively). The sound data were analysed in terms of the number of visible higher energy events compared to the surrounding background noise. MED. Adult P. maximus (n = 27, mean shell height standard deviation = 90.0 4.8 mm) were caught with a scallop dredge in the Bay of Brest, France. The calico scallop inhabits the relatively shallow waters of the continental shelf and upper slope out to reported depths of 370 m (Waller, 1969). Although closely related to larger bay scallops, calico scallops ( Argopecten gibbus) live in deeper, offshore waters along the east and west coasts of Florida. Exposures to 5 000 cells L-1 and 10 000 cells L-1 A. minutum resulted in similar valve movement patterns as H. triquetra exposure at the same concentrations, but significant differences were obtained between the two algal treatments at 500 000 cells L-1 (Fig 4). However, the valve gape outside active periods was identical in all exposure conditions. The left (upper) valve is somewhat more convex than the right (lower) (Broom 1976).