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Miller et al. BEM V, 26 Mar @ 1100 1
TEMPERATURE AND SALINITY TOLERANCE TEMPERATURE AND SALINITY TOLERANCE OF VIETNAMESE BAIT WORMS, OF VIETNAMESE BAIT WORMS,
NAMALYCASTISNAMALYCASTIS SP.: IMPLICATIONS FOR SP.: IMPLICATIONS FOR ESTABLISHMENT OF A TROPICAL IMPORT ESTABLISHMENT OF A TROPICAL IMPORT
IN THE SOUTHEASTERN USAIN THE SOUTHEASTERN USA
D.C. Miller, R.K. Dale and J.R. Brown University of Delaware, Lewes, DE, USA
[email protected], [email protected], [email protected]
P.D. HugginsFairmont State College, Fairmont, WV, USA
Miller et al. BEM V, 26 Mar @ 1100 2
Talk Outline• What is Namalycastis sp? • What is its invasion potential?• Temperature and salinity
experiments• Reproduction, regeneration, survivorship• Ongoing cold acclimation experiment• Tentative conclusion: limited by 10 ºC
isotherm– Potential survival south of Charleston, SC
Miller et al. BEM V, 26 Mar @ 1100 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
Miller et al. BEM V, 26 Mar @ 1100 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
Miller et al. BEM V, 26 Mar @ 1100 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
Miller et al. BEM V, 26 Mar @ 1100 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
Miller et al. BEM V, 26 Mar @ 1100 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
Miller et al. BEM V, 26 Mar @ 1100 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
Miller et al. BEM V, 26 Mar @ 1100 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
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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
Miller et al. BEM V, 26 Mar @ 1100 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
0
2
4
6
8
10
12
0 24 48 72 96
Time (Hours)
Ind
ivid
ual
s R
emai
nin
g
25ºC
16ºC
15ºC
12ºC
11ºC
Miller et al. BEM V, 26 Mar @ 1100 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
0
2
4
6
8
10
12
0 24 48 72 96
Time (Hours)
Ind
ivid
ual
s R
emai
nin
g
0 ppt
25 ppt
35 ppt
Miller et al. BEM V, 26 Mar @ 1100 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”
60
70
80
90
100
110
120
0 30 60 90 120
Time (minutes)M
ean
Per
cen
t In
itial
M
ass
0 ppt
10 ppt
20 ppt
30 ppt
Miller et al. BEM V, 26 Mar @ 1100 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?
Surviviorship at 22-23 ºC
0
20
40
60
80
100
120
0 50 100 150
Days in cultureIn
div
idu
als
(n)
Miller et al. BEM V, 26 Mar @ 1100 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?
Miller et al. BEM V, 26 Mar @ 1100 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
Miller et al. BEM V, 26 Mar @ 1100 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
Miller et al. BEM V, 26 Mar @ 1100 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
