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Spawning & Larviculture of Bivalve Mollusks

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Spawning & Larviculture of Bivalve Mollusks Spawning & Larviculture of Bivalve Mollusks Grade Level: Subject Area: Time: 9-12 Aquaculture, Biology, Preparation: 30 minutes to prepare Reproduction, Anatomy Activity: 50 minute lecture (may require 1 ½ class periods) Clean-up: NA SPS (SSS): 06.04 Employ correct terminologies for animal species and conditions (e.g. sex, age, etc.) (LA.A.1.4.1-4; LA.A.2.4.4; LA.B.1.4.1-3; LA.B.2.4.1-3; LA.C.1.4.1; LA.C.2.4.1). 11.09 Develop an information file in aquaculture species (LA.A.1.4, 2.4; LA.B.1.4, 2.4; LA.C.1.4, 2.4, 3.4; LA.D.2.4; SC.D.1.4; SC.F.1.4, 2.4; SC.G.1.4, 2.4). 11.10 List and describe the major factors in the growth of aquatic fauna and flora (LA.A.1.4, 2.4; LA.B.1.4, 2.4; LA.C.1.4, 2.4, 3.4; LA.D.2.4; SC.D.1.4, SC.F.1.4, 2.4; SC.G.1.4, 2.4). 13.02 Explain how changes in water affect aquatic life (LA.A.1.4, 2.4; LA.B.2.4; LA.C.1.4, 2.4; LA.D.2.4; SC.F.1.4; SC.G.1.4). 13.03 Explain, monitor, and maintain freshwater/saltwater quality standards for the production of desirable species (LA.A.1.4, 2.4; LA.B.2.4; LA.C.1.4, 2.4; LA.D.2.4; MA>B.1.4; MA.E.1.4, 2.4, 3.4; SC.E.2.4; SC.F.2.4; SC.G.1.4). 14.01 Identify factors to consider in determining whether to grow an aquaculture species (LA.A.1.4, 2.4; LA.B.2.4; LA.C.1.4, 2.4; MA.A.1.4, 2.4, 5.4; MA.B.1.4, 3.4; MA.D.2.4; DD.N.2.4; SS.D.2.4, 3.4). 14.02 Identify/describe facilities used in a grow out operation (LA.A.1.4, 2.4; LA.B.2.4; LA.C.1.4, 2.4; MA.A.5.4; SC.G.1.4; SS.B.2.4). 14.04 Determine the purpose and functions of a hatchery (LA.A.1.4, 2.4; LA.B.1.4, 2.4; LA.C.1.4, 2.4; MA.A.1.4, 5.4; MA.E.1.4, 2.4; SC.F.1.4, 2.4; SC.G.1.4, 2.4; SS.B.2.4; SS.D.1.4, 2.4). 14.05 Identify and describe the sexual reproductive process and methods of reproducing aquaculture organisms (LA.A.1.4, 2.4; LA.B.2.4; LA.C.1.4, 2.4; SC.F.1.4, 2.4; SC.G.1.4, 2.4; SC.H.1.4, 2.4, 3.4). 14.06 Identify and describe the spawning facilities used in aquaculture (LA.A.1.4, 2.4; LA.B.2.4; LA.C.1.4, 2.4; MA.A.1.4, 2.4, 3.4, 4.4, 5.4; MA.C.1.4; SC.F.1.4, 2.4; SC.G.1.4, 2.4; SC.H.1.4, 2.4, 3.4). 15.01 Identify the types of growing systems and important factors in their selection, design, and use (LA.A.1.4, 2.4; LA.B.2.4; LA.C.1.4, 2.4; MA.A.1.4, 2.4, 3.4, 4.4, 5.4; MA.B.1.4, 2.4, 3.4, 4.4; MA.C.3.4; MA.D.1.4, 2.4; MA.E.2.4; SC.G.1.4, 2.4; SC.H.3.4). Objectives: 1. Students will be able to describe reproductive characteristics in bivalve mollusks. 2. Students will be able to describe the environmental conditions that induce spawning in bivalve mollusks. 3. Students will be able to describe the process of spawning for bivalve mollusks. Abstract: In the simplest molluskan reproductive systems, two gonads sit next to the coelom that surrounds the heart and shed ova or sperm into the coleom, from which the nephridia extract them and emit them into the mantle cavity. Mollusks that use such a system remain of one sex all their lives and rely on external fertilization. Some mollusks use internal fertilization and / or are hermaphrodites, where an individual can function as both sexes; both of these methods require more complex reproductive systems. The most basic molluskan larva is a trochophore which is planktonic and feeds on floating food particles by using the two bands of cilia around its "equator" to sweep food into the mouth, which uses more cilia to drive them into the stomach, which uses further cilia to expel undigested remains through the anus. New tissue grows in the bands of mesoderm in the interior, so that the apical tuft and anus are pushed further apart as the animal grows. The trochophore stage is often succeeded by a veliger stage in which the prototroch, the "equatorial" band of cilia nearest the apical tuft, develops into the velum ("veil"), a pair of cilia-bearing lobes with which the larva swims. Eventually the larva sinks to the seafloor and metamorphoses into the adult form. In some species the newborn larvae are already veligers, and other species have direct development, in which a miniature adult emerges from the egg. Bivalve reproduction takes place externally when eggs and sperm from the gonads are released into the water, and a female may spawn millions of eggs in her lifetime. Once fertilized, tiny, free-swimming larvae are formed. This planktonic stage usually lasts a few days, and the larvae settle and attach themselves to a hard surface, where they then begin to form a shell. Interest Approach: In small groups have students try to come up with definitions for the following words: hermaphroditic protandrous oocytes synchronous spawning trochophore veliger metamorphosis Share a few of the class definitions then explain that the lecture will cover these words. Student Materials: 1. Paper 2. Pencil Teacher Materials: Material Store Estimated Cost Bivalve Reproduction NA NA lecture notes Bivalve Reproduction NA NA figures Student Instructions: 1. Actively participate in a lecture regarding bivalve reproduction. Teacher Instructions: Preparations: This activity is an overview of bivalve reproduction and is intended to be used within a classroom lecture framework. Lecture notes and figures for this lesson are in the SUPPORT MATERIALS section. Activity: 1. Lecture on Bivalve Reproduction Post work/Clean-up: There is no clean-up for this lesson. NOTE: As an alternate activity, have students collect adult clams or oysters from the wild during the appropriate season (spring/fall). Dissect some of the specimens to determine if they are in reproductive condition to spawn. Anticipated Results: Students will become knowledgeable of the reproductive biology of bivalve mollusks, spawning and larval development, and setting and nursery culture. The hard clam, known throughout New England as the northern quahog, (Mercenaria mercenaria) will be used as a model. Support Materials: 1. Bivalve Reproduction lecture notes 2. Bivalve Reproduction figures 3. Online Publications: Southern Regional Aquaculture Center ― www.msstate.edu/dept/srac/publicat.htm 4. Biology and Culture of the Northern Quahog (Mercenaria mercenaria) (SRAC 433) 5. The Cultivation of American Oysters (SRAC 432) 6. Helm, M.M. and N. Bourne. 2004. The Hatchery Culture of Bivalves: a Practical Manual. FAO Technical Paper No. 471. http://www.fao.org/docrep/007/y5720e/y5720e00.htm 7. Adams, C. et al. 1991. Investing in Commercial Hard Clam Culture: A Comprehensive Guide to the South Atlantic States. Florida Sea Grant Report No. 104 (SGR-104). Gainesville, FL. 128 pp. 8. Huner, J.V. and E.E. Brown (Eds.). 1985. Crustaceans and Mollusk Aquaculture in the United States. AVI Publishing Company, Inc., Westport, Connecticut. 476 pp. 9. Castagna, M. and J. Kreuter. 1981. Manual for Growing the Hard Clam Mercenaria. Sea Grant Program, Virginia Institute of Marine Science, Gloucester Point, VA. 107 pp. 10. Landau, M. 1992. Introduction to Aquaculture. John Wiley and Sons, New York. 440 pp. 11. Manzi, J. and M. Castagna. (Eds.). 1989. Clam Mariculture in North America. Elsevier Press, New York, New York. 461 pp. 12. Manzi, J. and J.M. Whetstone. 1983. Intensive Hard Clam Mariculture: A Primer for South Carolina Watermen. South Carolina Sea Grant Consortium Publication No. 91-01. 20 pp. 13. Quayle, D.B. and G.F. Newkirk. 1989. Farming Bivalve Mollusks: Methods for Study and Development. Advances in World Aquaculture, Volume 1. World Aquaculture Society, Baton Rouge, LA. 294 pp. 14. Sarkis, S. 2008. Installation and Operation of a Modular Bivalve Hatchery. FAO Fisheries Technical Paper No. 492. Rome, Italy. 173 pp. 15. Vaughan, D., L. Creswell, and M. Pardee. 1990. A Manual for Farming the Hard-Shell Clam in Florida. Florida Dept. of Agriculture and Consumer Services, Tallahassee, FL. 42 pp. Explanation of Concepts: Characteristics of bivalve reproduction Environmental conditions for bivalve reproduction Spawning, larviculture, metamorphosis, and post-set nursery Support Materials Bivalve Reproduction Lecture Notes I. General Characteristics a. Bivalve mollusks, such as clams, oysters and scallops have unique reproductive biology, in that they are all hermaphroditic i. They are both male and female during their lifetime ii. Clams and oysters are protandrous (begin as males and later develop into females) iii. In contrast, many fish such as grouper are protogynous (females that later develop into males) iv. Scallops are even more unique, they are simultaneous hermaphrodites v. Reproductive organs 1. Oocytes (eggs) and sperm are located overlying the visceral mass (see bivalve anatomy) 2.
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