Date post: | 12-Jan-2016 |
Category: |
Documents |
Upload: | timothy-stevens |
View: | 215 times |
Download: | 1 times |
Mysid Life Cycle Detailed Review Paper
NACEPTEndocrine Disruptor Methods Validation
SubcommitteeJuly 2002
Leslie Touart
Detailed Review Paper:
MYSID LIFE CYCLE TOXICITY TEST
WORK PERFORMED BY
On behalf of the United States Environmental Protection Agency
EPA CONTRACT NUMBER 68-W-01-023
METHODS USED IN THIS ANALYSIS
• On-line Literature Search (August 15th 2001)• “Dialog” On-Line search with database Biosis
Previews Aquatic Science and Fisheries Abstracts • Endocrine disruptor screening methods for mysids
and sheepshead minnows• Key Words “sheepshead minnow” “mysid shrimp*
or reproduc* toxicity or devel*”• Approximately 526 records were refined down to
26 papers that were reviewed
METHODS USED IN THIS ANALYSIS
• Second search of Biosis and Aquatic Science and Fisheries abstracts was performed on August 22, 2001 which resulted in approximately 184 records
• Additional Search August 22 –24 on the ISI Web of Science database. Twenty references were found
METHODS USED IN THIS ANALYSIS
External/Internal Peer Review• Dr. Jerry Neff - Battelle• Jeff Ward -Battelle• EPA Technical Experts
OVERVIEW AND SCIENTIFIC BASIS OF MYSID LIFE CYCLE TOXICITY TEST
• Estuaries, which are important ecosystems, are among the earliest recipients of endocrine disrupting chemicals (EDCs)
• Crustaceans are often among the most abundant and most sensitive organisms (particularly mysids) in estuaries and they form vital links in food webs
• Many insecticides are considered putative EDCs. Certain insecticides formulated as IGRs adversely affect crustaceans by disrupting molting and metamorphosis
OVERVIEW AND SCIENTIFIC BASIS OF MYSID LIFE CYCLE TOXICITY TEST
• Endocrine system of an invertebrate differs from that of a vertebrate; therefore, the response of an invertebrate to an EDC could be expressed differently
• Ecdysteroids, which are the molting hormones in mysids, are also involved in the control of reproduction and embryogenesis. Mysids show promise as a potential indicator for evaluating ecdysteroid and EDC interaction.
TEST SPECIES
• Americamysis bahia• Holmesimysis costata• Mysidopsis intii• Neomysis integer
Americamysis bahia
• Reach 10 mm total length• Ecologically relevant to Gulf of Mexico
up through Narragansett, Rhode Island• Sexually mature at 12-20 days, brood
pouch fully formed at 15 days, developing young carried 2-5 days resulting in life cycle of between 17 to 20 days
• Females produce 11 juveniles/brood
Holmesimysis costata
• Reach 7 mm total length• Ecologically relevant to northeast Pacific
region• Sexually mature at 42 days, young are
released at about 65 to 73 days• Species are field-collected and available
year round
Mysidopsis intii
• Adults reach 7 mm total length• Ecologically relevant throughout South
America and Southern California• Sexually mature with young released at
about 20 days• Species are field-collected and then
easily cultured in the laboratory
Neomysis integer
• Females reach 18 mm total length, males are smaller
• Ecologically relevant throughout Northern Europe
• Sexually mature at 42 days, young are released at about 65 to 73 days
• Females can produce up to 80 juveniles/brood
• Species are field-collected and then easily cultured
Americamysis bahia
StrengthsWidely availableEasily culturedEasily identified from
others Short generation timeWidely usedStandardized protocol
WeaknessesMay not be ecologically relevant to colder-water materials-testing
Homesimysis costata
StrengthsEcologically relevant to
the Northeast Pacific region
Large brood sizesEase of handling and
maintenanceUsed extensivelyStandardized protocol
WeaknessesLonger generation
timeDifficulty in raising
multiple broodsField-collected --
identified prior to use
Tests required to measure EDC related endpoints must be developed
Mysidopsis intii
StrengthsEcologically important in
northeast Pacific coastShorter generation time than H.
costataEPA sponsored 7-day toxicity
testing protocol
WeaknessesField-collected --
identified prior to useTests required to
measure EDC-related endpoints must be developed
Must be fed dietary supplement of copepods
Neomysis integer
StrengthsEcologically important in
EuropeProtocols to measure
EDC- related endpoints are underway
WeaknessesField-collected --
identified prior to use
Tests required to measure EDC-related endpoints must be developed
ROUTES OF ADMINISTRATION OF
CHEMICAL EXPOSURE
• Aqueous Continuous flow-through systemConstant concentration of spiked water to the
test chamber
• SedimentMysids have been observed to collect
sediment, manipulate it at mouth region, and drop it. Therefore, clean spiked sediment could be used
• Dietary UptakeMix chemical with mysid food prior to feeding
POTENTIAL MEASUREMENT ENDPOINTS
• Survival• Molting frequency• Growth: ash-free dry weight and length • Measures of reproductive performance
– Sexual maturity– Time to first brood release– Total number of offspring
• Biochemical measures– Metabolic disruption– Vitellogenin induction– Cytochrome P450 enzyme Levels– Blood glucose levels
CANDIDATE PROTOCOLS
1) ASTM E1191 (ASTM 1997)2) OPPTS 850.1350 (EPA 1996)3) Chapman (1995)4) EPA-supported study (Langdon et al.
1996)
ASTM E 1191
Test Species: A. bahia, A. bigelowi, and A. almyra
Chemical Exposure:7 days after median brood release
Exposure Measurement Endpoints:Adult survival, body length, dry weight Number of young produced
Acceptance Criteria: 70% Survival of Adults75% of adult females produce young 3 average number of young/female
OPPTS 850.1350 Test Species: A. bahia
Chemical Exposure: 28 days
Exposure Measurement Endpoints:Adult survival, body length, dry weight and Number of young produced
Acceptance Criteria: 75% of parent females produce young 3 average number of young/female
CHAPMAN (1995)
Test Species:H. costata
Chemical Exposure:7 days
Exposure Measurement Endpoints:Adult survivalAdult growth
Acceptance Criteria: 75% of control survival 0.40 g dry weight in control Survival minimum significant difference (MSD) <40% Growth MSD <50 g
LANGDON (1996) Test Species: M. intii
Chemical Exposure: 28 days
Exposure Measurement Endpoints:Adult survival, body length, dry weightNumber of young produced
Acceptance Criteria: 75% of adult females produce young, and >3
average number of young/female
RECOMMENDED PROTOCOL-BLENDING OF EPA AND ASTM
Test Species: Americamysis bahia
Duration:Two-generation: 7 days after median first brood release in F1”
Reproductive Endpoints: Survival: (P, F1’, F1”, F2)Molt frequency: (P, F1’, F1”)Time to maturation: (P and F1”)Time to first brood release: (P and F1”)Time to second brood release: (P)Growth: length and dry weight: (P, F1’, F1”)Brood size/number of offspring: (P, and F1”)
RECOMMENDED PROTOCOL
Biochemical Endpoints:
Metabolic disruption: (P and F1”)
Steroid metabolism: (P and F1”)Vitellogenin induction: (P and F1”)Cytochrome P450 enzymes: (P and F1”)Blood glucose: (P and F1”)
Test Validity Criteria:
75% in parent controls
3 average number young/female/day Water quality requirements are met
SIGNIFICANT DATA GAPS
• Determine specific information on longer testing duration and on incorporating a second generation
• Biochemical Measurement Endpoints:– Refine steroid metabolism endpoints for mysids– Study cytochrome P540 enzyme level– Conduct vitellogenin mechanistic studies to confirm
endocrine disruption versus metabolic toxicity– Final goal: determine whether specific endpoint
responses can be linked to different classes of compounds affecting ecdysteroid, androgen, or other hormonal cycles
IMPLEMENTATION CONSIDERATIONS
• Prevalidation studies following the ICCVAM validation process Recommend studies to determine how
biochemical matrices may be related to hormonal disturbances
• Validation of the study design through interlaboratory comparisons
Questions1) Does the EDMVS agree that the two-generation
method recommended with Americamysis bahia is appropriate?
2) Does the EDMVS agree that prevalidation should evaluate the increased sensitivity of a two-generation design over the existing one-generation standard practice?
3) Should EPA explore the feasibility and utility of biochemical endpoints, as described in the DRP, for possible addition to the recommended protocol?
4) Does the EDMVS have suggestions to improve the DRP?