Transcript TEMPERATURE AND SALINITY TOLERANCE OF VIETNAMESE …

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
[email protected], [email protected], [email protected]
P.D. Huggins
Fairmont State College, Fairmont, WV, USA
[email protected]
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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
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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
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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
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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
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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
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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
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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
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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
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Miller et al. BEM V, 26 Mar @ 1100
25ºC
8
16ºC
15ºC
6
12ºC
4
11ºC
2
96
72
0
48
– 22 – 34 ºC yearround
– wet season: May
– Nov
– dry season: Jan Mar
10
24
• Ho Chi Minh City
12
0
• Fine at >15 ºC
for 5 days
• Quick death at
11 ºC
Individuals Remaining
Temperature Results
Time (Hours)
11
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12
10
8
0 ppt
6
25 ppt
4
35 ppt
2
96
72
48
24
0
0
• 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
Individuals Remaining
Salinity Setup and Results
Time (Hours)
12
• 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”
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Mean Percent Initial
Mass
Osmoregulation Capabilities
120
110
0 ppt
100
10 ppt
90
20 ppt
80
30 ppt
70
60
0
30
60
90
120
Time (minutes)
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Other Observations
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Individuals (n)
• 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
100
80
60
40
20
0
0
50
100
150
Days in culture
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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?
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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
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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
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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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