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D.C. Miller, R.K. Dale and J.R. Brown University of Delaware, Lewes, DE, USA

TEMPERATURE AND SALINITY TOLERANCE OF VIETNAMESE BAIT WORMS, NAMALYCASTIS SP.: IMPLICATIONS FOR ESTABLISHMENT OF A TROPICAL IMPORT IN THE SOUTHEASTERN USA. D.C. Miller, R.K. Dale and J.R. Brown University of Delaware, Lewes, DE, USA  dmiller@udel.edu, ryandale@udel.edu, jrbrown@udel.edu

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D.C. Miller, R.K. Dale and J.R. Brown University of Delaware, Lewes, DE, USA

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  1. TEMPERATURE AND SALINITY TOLERANCE OF VIETNAMESE BAIT WORMS, NAMALYCASTIS SP.: IMPLICATIONS FOR ESTABLISHMENT OF A TROPICAL IMPORT IN THE SOUTHEASTERN USA D.C. Miller, R.K. Dale and J.R. Brown University of Delaware, Lewes, DE, USA  dmiller@udel.edu, ryandale@udel.edu, jrbrown@udel.edu P.D. Huggins Fairmont State College, Fairmont, WV, USA phuggins@mail.fscwv.edu

  2. Talk Outline • What is Namalycastis sp? • What is its invasion potential? • Temperature and salinityexperiments • Reproduction, regeneration, survivorship • Ongoing cold acclimation experiment • Tentative conclusion: limited by 10 ºC isotherm • Potential survival south of Charleston, SC

  3. Namalycastis sp. • Undescribed species • Family Nereididae • subfamily Namanereidinae • cf. Namalycastis abiuma • Bright pink and >2 m in length • Mangrove swamps, dug from roots, Mekong Delta • Vietnam  Bay Area  Mid-Atlantic

  4. Nuclear Blood Worms® • Sold as bait • alternative to bloodworms • do not bite or bleed • $6 - 7 per container • 2 - 3 worm per container,  50 g live weight

  5. Known Risks • Media: local and national print, plus local TV in 2002 • Pathogens in soil packing material • Including Vibrio cholera • Now packed in newspaper compost • No federal or state restriction on import and distribution • Falls between established regulations and agencies • Release through use as bait • Cut bait or whole worms when discarded • Long-term survival thought unlikely due to seasonally cold temperatures

  6. Potential Invader? • Conventional wisdom is that there is little risk locally • Worms die if refrigerated, kept for sale on counters at room temperature • Could be sold as bait anywhere in US • Cut bait, discarded whole animals • Could be bought here and easily transported and released in southeast US • I-95 corridor south to SE or Gulf coasts • Seasonal temperature range likely would not necessarily prevent survival or establishment in southeast US

  7. Almost No Natural History Information • Undescribed species in poorly known subfamily of clam worms • Temperature and salinity tolerances poorly known • Reportedly established in Hawaii • In culture in France? • Suitably warm, vegetated habitats certainly exist in US southeast in marshes and mangroves

  8. Goal • To determine temperature and salinity tolerances, which combined with seasonal water temperature data, will permit science-based assessment of the risk of establishment of this species in Delaware and points south along the US east coast

  9. Temperature and salinity tolerance experiments • Worms “collected” at Wal-Mart • Lab bins with mud and salt marsh detritus • Variations in moisture, salinity, sediment type and food supplements • Temperature 22 – 25 ºC, salinity kept at 10 – 13 ppt

  10. Temperature Setup • Two replicate tanks, n=10 worms each, 3 temps at once • 11, 12 15, 16,25 ºC for 5 days • Pretests and repeated twice with same results

  11. Temperature Results • Fine at >15 ºC for 5 days • Quick death at 11 ºC • Ho Chi Minh City • 22 – 34 ºC year-round • wet season: May – Nov • dry season: Jan - Mar

  12. Salinity Setup and Results • Buckets in temperature control bath, 29 ºC • N = 10 worms at S = 0, 25, 35 ppt • Survive 0 to > 30 salinity for almost 5 days

  13. Osmoregulation Capabilities • 4 worms each at • 0, 10, 20, 30 ppt • No weight change at 10 ppt • Gain at 0 ppt, lose at 20, 30 ppt • “Osmoconformers”

  14. Other Observations • Mortality 1% to < 0.5% per day in culture • Deposit feeder and scavenger, but have not observed predation • Spontaneous fragmentation“near death” • Regeneration?

  15. Problems with Tropical Imports • Diverse fauna, undescribed species • Bait, exotic pets, novelty and cachet • Collected at minimal cost by hand, with methods that may be environmentally damaging • No regulation of harvesting in country of origin • Extended collecting season, even year-round • Shipped without need for refrigeration • Lacking justification • harmful effects not demonstrated, so why restrict?

  16. Some Biological Data Goes a Long Way • Local culture would eliminate some, but not all problems • Allow sale and use where deemed safe, but restrict or raise flags where survival cannot be excluded? • NODC Coastal Water Temperature Guide or other real-time data products

  17. Next Steps • Cold acclimation experiment completed: no temperature acclimation observed • Photoperiod? • Wet-dry seasonality? • Reproduction? • Prey on local species? • Temperature microclimates and microhabitats in local marshes and mangroves to south • Support from the Sea Grant Aquatic Nuisance Species program

  18. Summary • Habitat—cryptic, in vegetation, semi-marine, semi-aquatic, semi-terrestrial • Euryhaline and estuarine-tolerant–salinity not limiting • Doubtful overwintering in Mid Atlantic • <10 ºC for 4-5 months each year average • 10 ºC (or greater) is minimum temperature from about Charleston southward • Cannot exclude possibility of invasion from there southward

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