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Mercenaria Mercenaria (Mollusca: Bivalvia): Temperature-Time Relationships for Survival of Embryos and Larvae

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Mercenaria Mercenaria (Mollusca: Bivalvia): Temperature-Time Relationships for Survival of Embryos and Larvae W&M ScholarWorks VIMS Articles Virginia Institute of Marine Science 1974 Mercenaria mercenaria (Mollusca: Bivalvia): temperature-time relationships for survival of embryos and larvae VS Kennedy WH Roosenburg M Castagna Virginia Institute of Marine Science JA Mihursky Follow this and additional works at: https://scholarworks.wm.edu/vimsarticles Part of the Aquaculture and Fisheries Commons Recommended Citation Kennedy, VS; Roosenburg, WH; Castagna, M; and Mihursky, JA, Mercenaria mercenaria (Mollusca: Bivalvia): temperature-time relationships for survival of embryos and larvae (1974). Fisheries Bulletin, 72(4), 1160-1166. https://scholarworks.wm.edu/vimsarticles/1873 This Article is brought to you for free and open access by the Virginia Institute of Marine Science at W&M ScholarWorks. It has been accepted for inclusion in VIMS Articles by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. MERCENARIA MERCENARIA (MOLLUSCA: BIVALVIA): TEMPERATURE-TIME RELATIONSHIPS FOR SURVIVAL OF EMBRYOS AND LARVAE1 V. S. KENNEDY,2 W. H. RoosENBURG,3 M. CASTAGNA,4 AND J. A. MlHURSKY3 ABSTRACT To estimate the effects of entrainment of Mercenaria mercenaria embryos and larvae in the cooling­ water systems of steam-electric power plants, we used a thermal gradient apparatus. Cleavage stages, trochophore larvae and straight-hinge veliger larvae were subjected to 11 different temperatures for 8 different time periods. There was a direct relationship of mortality with tempera­ ture increase and, at higher temperatures, with increase in time exposure. As the clams aged, temperature tolerance increased, with cleavage stages most sensitive to higher temperature and straight-hinge larvae least sensitive. Multiple regression analyses of percentage mortality on temperature and time produced estimating equations that allow prediction of percentage 1nortality under different conditions of temperature and time exposure. Entrainment ofM. mercenaria embryos and larvae in cooling systems of power plants should be as short as possible if mortality is to be held to a minimum. Passage of plankton through the cooling system priate references). We used an aluminum thermal of steam-electric power plants is a matter of gradient apparatus (Thomas, Scotten, and Brad­ concern (Coutant, 1970). Mortality caused by such shaw, 1963) to determine thermal tolerances of entrainme11t (e.g. Marcy, 1971) might lead to loss hard clam embryos and larvae at different com­ of species from the vicinity of a power plant, with binations of temperature and time exposure. This various ecological and economic consequences. It simulated exposure of these organisms to heat is estimated that increased demand for cooling for varying time periods in power plant cooling water may necessitate the location of power plants systems. The research was undertaken in the in estuarine and marine environments (Tarzwell, summer of 1972 and spring of 1973 at the Eastern 1972). Thermal tolerances of planktonic organ­ Shore Laboratory, Virginia Institute of Marine isms in these environments must be determined to Science, Wachapreague, Va. Similar experiments allow estimation of lengths of entrainment and have been made on embryos and larvae of the increases in temperature that are least harmful coot clam, Mulinia lateralis (Say) (Kennedy et to entrained organisms. al., 1974). Reference should be made to that paper The hard clam, Merceriaria niercenaria (L.), for fuller details of experimental apparatus and is an abundant and commercially important techniques. bivalve found in shallow inshore waters of the east coast of North America. It is easily spawned in MATERIALS AND METHODS the laboratory and has bee11 the subject of nu­ merous investigations on the influence of various Mercenaria mercenaria were stimulated to factors on its larval biology (see Loosanoff and spawn by fluctuating water temperatures (Loo­ Davis, 1963; Calabrese and Davis, 1970 for appro- sanoff and Davis, 1963) over the range of 22° to 30°C. Gametes from 3 to 32 females and 2 to 30 males were pooled in each experiment to provide 1Contribution No. 565 of the Natural Resources Institute, University of Maryland and Contribution No. 552 of the Vir­ genetic diversity (Calabrese and Davis, 1970). We ginia Institute of Marine Science. used three developmental stages: early cleavage 2Natural Resources Institute, University of Maryland, Ches­ - apeake Biological Laboratory, Solomons, Md.; present address: stages (2 h old); trochophore larvae (10-11 h); Fisheries Research Board of Canada, Biological Station, St. John's, Newf., Can. straight-hinge veliger larvae (32-50 h). 3Natural Resources Institute, University of Maryland, Chesa­ Wild stock collected as needed in the summer peake Biological Laboratory, Solomons, MD 20688. 4Virginia Institute of Marine Sci(lnce, Eastern Shore Labora­ near Wachapreague provided the gametes. After tory, Wachapreague, VA 23480. the experiments ended in 1972, the preservative Manuscript accepted Pebruar·y 1974. FISHERY BULLETIN: Vol. 72. No 4, 1974. 1160 KE NEDY ET AL.: TE1v!PERATURE-TIME RELATI ONSHIPS TABLE 1.- Percentage mortality of cleavage stages of Mercenaria mercenaria under different temperature-time combinations. Values in parentheses are temperatures corrected for the influence of injection water. Temperature •c Time (min) 17.5 20.2 22.7 25.1 27 6 30.0 32.5 34.9 37.4 39.7 42.4 1 0 39 14 12 12 35 0 0 3 26 85 (1 8.8) (2 1.5) (23.3) (31 6) (34.0) (35.8) (37 .7) (39.4) 5 26 0 24 11 21 0 0 12 64 99 100 (1 8.4) (2 1. 1) (22. 7) (31.9) (34.3) (36.4) (38.5) (40.3) 10 22 0 12 0 16 0 0 78 98 100 100 ( 18.3) (21 0) {34.1) (36.4) (38.5) (40.8) 30 0 16 1 0 8 40 63 100 100 100 100 60 1 1 0 12 0 22 46 88 100 100 100 100 120 0 0 10 0 16 0 91 100 100 100 100 180 0 7 0 28 0 54 72 100 100 100 100 360 21 0 0 0 0 0 98 100 100 100 100 TABLE 2.-Percentage mortality of trochophore larvae of Mercenaria mercenaria under different temperature-time combinations. Values in parentheses are temperatures corrected for the influence of injection water. Temperature •c Time (min) 17.6 20.1 22.6 25.0 27.5 29.9 32.4 34.8 37.3 39 7 42.3 1 29 19 14 0 0 2 1 1 0 0 14 20 (1 8.9) {2 1.4) (23.2) (31.5) (33.9) (35. 7) (37 7) (39.3) 5 25 30 19 14 0 0 0 0 0 41 93 (18.5) (21 0) (22.6) (31 .8) (34.2) {36 3) {38.5) (40.2) 10 25 21 2 3 1 0 0 0 2 86 100 (18.4) {21 1) (34. 1) (36.3) (38.5) ( 40.7) 30 20 13 0 17 8 1 2 10 55 100 100 60 20 0 5 7 6 0 0 0 100 100 100 120 17 0 0 0 0 0 0 63 100 100 100 180 18 1 0 0 0 0 0 100 100 100 100 360 11 8 7 10 0 3 47 100 100 100 100 'PABLE 3.-Percentage mortality of straight-hinge larvae of Mercenaria mercenaria under different temperature-tin1e combinations. Values in parentheses are temperatures corrected for th e influence of injection \vater. Temperature •c Time (min) 18.3 21 .0 23.5 26.1 285 30.9 33.4 358 382 40 7 43.1 1 3 2 3 2 2 3 4 4 3 5 4 (19.6) (21 .6) {30.0) {32.5) (34.2) (36.4) (38.4) (40 .1) 5 3 3 3 5 5 4 6 4 4 4 5 (19.2) (30.3) (32.8) (34.8) (37 0) (39.2) (41 0) 10 3 3 3 4 3 4 3 5 5 5 7 ( 1 9. 1) (35.0) (37 2) (39.5) (4 1.5) 30 3 2 3 3 4 3 5 5 8 5 29 60 5 4 2 4 4 4 5 7 5 47 76 120 3 3 5 2 5 4 5 3 9 13 99 180 5 4 4 4 6 3 3 11 6 12 96 360 4 4 4 5 5 6 4 8 9 97 98 in most of the vials containing the cleavage stages Embryos and larvae not used immediately in and trochophores was found to have developed a experiments were held at an1bient temperatures precipitate that hindered microscopic analysis of in 60-liter plastic containers at a density of about the results. Consequently, in March 1973 we 33/ml (cleavage stages, trochophores) or about spawned 2-yr-old individuals of the F2 generation 17/ml (straight-hinge) with the seawater changed produced in the. hatchery in 1971 from the same daily. Development appeared normal with no high local wild stock. Th.ese clams had been held in mortalities observed. Larvae not used in our beds near the h atchery. They were conditioned for experiments were successfully carried through to 6 wk in warm water before being spawned (Loo­ metamorphosis. sanoff and Davis, 1963) and provided us with re­ We used clarified, ultraviolet irradiated sea­ placement cleavage stages and trochophore water (28-31 °/oo) in the experiments. The cast larvae. Results of experiments using these re­ aluminum block, bored to hold 88 test tubes placements did not appear to differ from prelimi­ (25 mm) in an 8 )( 11 matrix (see Figure 1, nary results of the 1972 experiments. Kennedy et al., 1974) provided a thermal gradient 1161 FISHERY BULLETIN : VOL. 72, 0 . 4 that was approximately linear, varying by 2.3° 23° to 25°C. This altered the temperature in the to 2. 7°C from one column of test tubes to the next.
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