Current Developments in the Study of Bellamya japonica, a New Invasive Freshwater Snail in the Savannah Basin

Transcription

1 Current Developments in the Study of Bellamya japonica, a New Invasive Freshwater Snail in the Savannah Basin John Hains Clemson University Clemson, South Carolina This work was supported through the Creative Inquiry Program at Clemson University.

2 Aquatic Invasive Species (selected for brevity) Aquatic Plants Alligatorweed (Alternanthera philoxeroides) Brazilian Waterweed (Egeria densa) Caulerpa, Mediterranean Clone (Caulerpa taxifolia) Common Reed (Phragmites australis) Curly Pondweed (Potamogeton crispus) Didymo (Didymosphenia geminata) Eurasian Watermilfoil (Myriophyllum spicatum) Giant Reed (Arundo donax) Giant Salvinia (Salvinia molesta) Hydrilla (Hydrilla verticillata) Melaleuca (Melaleuca quinquenervia) Purple Loosestrife (Lythrum salicaria) Water Chestnut (Trapa natans) Water Hyacinth (Eichhornia crassipes) Water Lettuce (Pistia stratiotes) Water Spinach (Ipomoea aquatica) Aquatic Animals Alewife (Alosa pseudoharengus) Asian Carps Asiatic Clam (Corbicula fluminea) Asian Shore Crab (Hemigrapsus sanguineus) Asian Swamp Eel (Monopterus albus) Blueback herring (Alosa aestivalis) Bullfrog (Lithobates catesbeianus) Channeled Apple Snail (Pomacea canaliculata) Chinese Mitten Crab (Eriocheir sinensis) Eurasian Ruffe (Gymnocephalus cernuus) European Green Crab (Carcinus maenas) Flathead Catfish (Pylodictis olivaris) Northern Snakehead (Channa argus) New Zealand Mud Snail (Potamopyrgus antipodarum) Quagga Mussel (Dreissena bugensis) Round Goby (Neogobius melanostomus) Rusty Crayfish (Orconectes rusticus) Sea Lamprey (Petromyzon marinus) Spiny Water Flea (Bythotrephes longimanus) Tilapia (Tilapia spp.) Zebra Mussel (Dreissena polymorpha)

3 The vast majority of invasions fail. For this reason, we usually are not aware of them. Introduced and Died??

4 The vast majority of invasions fail. For this reason, we usually never hear about them. Introduced and Died BUT, If they succeed.??

5 The public is often unaware of the costs until too late.??

6 And these problems can be compounded by ignorance of biological or ecological interactions.??

7 THIS STUDY??

8 Meet: Bellamya japonica Rita Randy

9 Other Names: Bellamya japonica, Bellamya chinensis, Cipangopaludina chinensis, Viviparus malleatus, Viviparus chinensis malleatus, Viviparus japonicus, Viviparus stelmaphora, Paludina malleata, Paludina japonicus, Cipangopaludina malleata.

10 It may outcompete native snails and transmit human parasites, but very little is known about its ecological impacts in invaded systems and more research is necessary. Dr. Robert Dillon

11 Imported to West Coast Asian food market about Deliberate release to the Great Lakes where it was stocked as food for channel catfish, Ictalurus punctatus in Lake Erie in the 1940s

12 2006 Known Infestations

13 Invertebrate Anatomy OnLine Bellamya japonica Japanese Mystery Snail 24may2007 Copyright 2005 by Richard Fox Lander University

14 This species has the potential to serve as a vector for various parasites and diseases. Over its native range, the mysterysnail may serve as an intermediate host for: Echinocasmus elongatus, E. redioduplicatus, E. rugosus, Eupariphium ilocanum, E. recurvatum, Echinostoma macrorchis, E. cinetorchis Pace, G.L The Freshwater Snails Of Taiwan (Formosa). Malacological Review Supplement 1. Pages 1-117

15 But in 2008, a new impact emerged at Clemson University

16 But in 2008, a new impact emerged at Clemson University Industrial Impact

17 Intake for Chiller Systems at Clemson University Maintenance issues in summer of 2008 Chiller systems were clogged by snails

18 Internal exchange tubes for the chiller system. In this photo, the occlusions by snails is obvious. Approximately 30% of the flow through this heat exchanger was blocked. This maintenance had to be repeated every few days.

19 Professional divers were engaged to examine the status of the intake system. The system consisted of three pump wells, each with cross-section dimensions of 5x9 feet. One pump well alone contained approximately 400,000 snails.

20 Back to the field: We had long noticed that we would find most snails UNDER the rocks. So we hypothesized that they avoided daylight (phototaxis). This question had never been answered before.

21 Phototaxis: Vertical Experiment Regardless of the position of the light, above or below, or the starting position of the snails, after 400 trials (100 for each treatment) over 70% of the motion of the snails was away from the light without regard to position. Conclusion: there is an element of negative phototaxis but no detected geotaxis.

22 Phototaxis Experiment Then we tested the experimental method using a different species of freshwater snail, using identical methods. No evidence of either photo- or geotaxis. Conclusion: Experimental design was sound.

23 . which explained our observations in the field. But it left questions of how fast do they reproduce, metabolic rate, dispersal, etc. Almost nothing is known about these as invaders of new environments.

24 Remember, these are internally fertilized, live-bearing organisms. Basic Anatomy, Reproduction Just like us. Most of the same body parts. Called the same things.

25 Dissections showed that the sex ratio was nearly 1:1 but the number of baby snails was variable. If a female was reproductively mature and pregnant, she contained a minimum of approximately 30 babies. But she could have greater than 150 babies if she was a larger individual. The real question was the rate at which she gave birth.

26 Deep inside her uterus

27 Deep inside her uterus Could be over 100 of these

28 Rita - female Randy - male Males have a modified tentacle

29 Preliminary Results of the Fecundity Experiments We placed captive mature females into closed chambers, perforated with holes to allow water exchange but small enough to prevent the loss of newly born baby snails. We placed up to 30 of these chambers into an experimental pond and monitored them on a weekly basis beginning in at the end of February and ending in May. We found that the seasonal reproductive trend began in mid- March and peaked in May through the remainder of the summer. At peak, up to 20 babies per female could be born in a week.

30 Typical data for two weeks in April (the beginning of the season) Number of offspring per female Weeks

31 Dispersal: Mark and Recapture Trials To examine their dispersal, we tagged snails for a mark and recapture study in an experimental pond. The pond was divided into eight equal quadrats and the pre-existing population of Bellamya japonica was sampled from each quadrat. Each individual snail was individually measured, weighed, and tagged.

32 We also re-introduced tagged specimens to Lake Hartwell and monitored their position. The quadrat study indicated that this species does not meet the random re-assortment assumption of the mark-recapture method. Dispersal is too slow. However, the re-introduction study indicated that while they disperse slowly, this rate can be measured. After approximately 200 individuals were released, only 1% of them were found as far as 5 m from their re-introduction origin after two weeks. This is evidence that dispersal is very slow unless facilitated by active external intervention (perhaps by high water velocity, other animals, or people).

33 Allometric Relationships may be important for population dynamics and physiological processes.

34 Metabolic Studies: Snail Chambers 12 Dissolved Oxygen (mg/l) Birth Dissolved Oxygen 1 Dissolved Oxygen 2 Dissolved Oxygen 3 Dissolved Oxygen Time (s)

35 A certain horrified fascination with death..

36 Hypothesis: The damage observed in older (larger) snails is due to predator attack. Null Hypothesis: The damage observed in older (larger) snails is due to erosion (dissolution) of the calcium matrix in corrosive (low conductance) waters. Hypothesis: Mortality is increased as a result of this damage and survival rates can be increased by patching the damage. Null Hypothesis: Mortality is unaffected by these repairs.

37 Results of all studies to date: 1. Negative phototaxis 2. Moderate fecundity 3. Slow natural dispersal 4. No evidence of substrate preference 5. Obligate aerobic metabolism and metabolic rate 6. Allometric dependence under investigation 7. Circadian Rhythm Study evidence of its presence 8. Thus far no evidence of parasites 9. Unknown predators but evidence of predation

38 Conclusion 1. Infestations may be inconspicuous 2. Impacts to the ecosystem are uncertain 3. Proven potential for industrial impacts 4. Eradication methods unknown, possibly futile once the invasion has been detected 5. Basic biological and ecological features: continuing investigation

39 So Long and Thanks for all the Fish!

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