Effects of Resmethrin and PBO on Foraging Habits of

Juvenile Callinectes sapidus

Erin PlachyKaitlyn Schroeder-Spain

& Dr. D. L. Smee

Blue Crabs (Callinectes sapidus)

• Key predator and prey species in estuarine systems

• Commercially important: Texas landings at lowest levels since 1960s– Decline due to loss of habitat,

overfishing, and pollution

• Blue crab importance makes it necessary to mitigate additional pressures on existing populations

(Williams, 1973; Sutton & Wagner, 2007; Guillory et al., 2001)

Introduction

• Growing concern for insecticide runoff into estuaries– After significant rainfall,

pesticides have been found in nearby estuaries

– Mid-Texas Coast study found 93.4% of all samples contained triazine herbicides

• Insects and crabs are related– Share target enzymes

• Juvenile blue crabs grow up in estuaries– After mating, males go to lower

salinities and females move to higher salinities to release eggs

(Pennington et al. 2001)

Similar Studies• Virtually no studies done on crabs

with Res. + PBO, but there are several that have been conducted with mercury and other heavy metals– Produce similar effects on aquatic

organisms

• Contaminants like mercury have been found to cause reduced feeding and foraging ability of aquatic species such as killifish– Can affect organism’s motivation to

feed– Reduces foraging search effectiveness– Reduce ability to capture prey

(Weis et al. 2001)

Mercury Studies

• When exposed to mercury, blue crabs have a decreased ability to capture more active prey, but consumed equal amounts of less active prey– Blue crabs may be more

affected by reduced coordination rather than lack of motivation or hunger

(Reichmuth et al. 2009; Weis et al. 1999, 2000, 2001, 2011)

SCOURGE™

• Study sublethal effects of Res. + PBO on foraging ability of juvenile blue crabs

• Some studies have investigated effects of pesticides on blue crabs, but sublethal effects of ingredients in SCOURGE™ on crabs are unknown

(Osterburg et al. 2012; Horst and Walker 1999)

• SCOURGE™: used primarily in mosquito pesticide spraying

• Resmethrin: pyrethroid insecticide– Interferes with nervous system

• Piperonyl Butoxide (PBO): synergist– Inhibits metabolization of toxins– Makes resmethrin more potent

(Zulkosky et al., 2005; WHO, 2001)

Mesocosm: Experimental Design

• Juvenile male blue crabs and brown shrimp caught in Corpus Christi, TX– Crabs: 35-60 mm; Shrimp 35-50 mm– Crabs must have chelipeds,

swimming legs, and most walking legs

– Salinity: 18-20 (PSU)– Acclimated to lab for min. 48-hrs

• Exposed to treatment or control for 3 or 12 hours, separately

• Each mesocosm:– A filter, oyster shell layer, and

untreated saltwater– 1 crab + 8 shrimp

Measured crab and shrimp length

12-hr Exposure

CONTROLCrab: control-ethanol

Shrimp: control-ethanol(n=12)

LOW TREATMENTCrab: 1:3 Res. + PBO

Shrimp: control-ethanol(n=6)

HIGH TREATMENTCrabs: 10:30 Res. +

PBOShrimp: control-

ethanol (n=6)

3-hr Exposure

HIGH TREATMENTCrab: 10:30 Res. +

PBOShrimp: control-

ethanol

(n=2)

High mortality in 12-hr 10:30 exposure, so new crabs were measured and put in high exposure for 3 hrs

*Indicates control ethanol

Data Collection

• 1 crab & 8 shrimp• Observations recorded:

– # shrimp alive– shrimp dead at each hr– total shrimp dead– # shrimp out– if/where crab was hiding

(filter or shell)– oyster piling occurrence

• Data recorded at hour: – 0, 1, 2, 3, 6, 8, 12, 24, 36,

48, 60, & 72 hrs – or until no shrimp left

Data Analysis

• Statistical tests completed in either JMP or Excel– Repeated measures

ANOVA – Post hoc: Students t-

test, with Bonferroni correction to compare treatments

Average Shrimp Alive: Res. + PBO With High Exposure 12-hr

0 1 2 3 6 8 12 240

1

2

3

4

5

6

7

8

9 Control Ethanol

Hour

Nu

mb

er o

f S

hri

mp

Ali

ve

10:30 ppb Res. +PBO ate significantly less than control (p=0.006)

p = 0.006

Average Shrimp Alive: Res. + PBO With High Exposure 12-hr

0 1 2 3 6 8 12 240

1

2

3

4

5

6

7

8

9 Control Ethanol 10:30 ppb 3-hr 1:3 ppb 12-hr

Hour

Nu

mb

er o

f S

hri

mp

Ali

ve

10:30 ppb Res. +PBO ate significantly less than control (p=0.006)

Results

• 10:30 ppb Res. + PBO (12-hr) not analyzed because of low replication (n=2)

• Focus on the treatments that had more replicates

Repeated Measures ANOVA

• Treatment has a nearly significant ( p = 0.0630) effect on consumption – Due to low number of

replicates, could be considered significant in order to avoid making a Type II error

• Time is a significant factor (p<0.0001)

• Time-treatment interaction was not significant (p=0.280)

Average Shrimp Alive: Res. + PBO

0 1 2 3 6 8 12 240

1

2

3

4

5

6

7

8

9Control Ethanol 10:30 ppb 3-hr1:3 ppb 12-hr

Hour

Nu

mb

er

of

Sh

rim

p A

live

Treatment has a nearly significant ( p = 0.0630) effect on consumption

p=0.0796 p=0.0079

p=0.0004

Post hoc Analysis: Students t-test

• 1:3 ppb Res. + PBO (12-hr)– crabs ate more than the

control ethanol group (p=0.0079)

• 10:30 ppb Res. + PBO (3-hr) – Nearly significant: crabs ate

less than the control ethanol group (p=0.0796)

• 10:30 ppb Res. + PBO ate less than 1:3 ppb Res. + PBO treatment (p=0.0004)

1:3 ppb Res + PBO (12-hr)

10:30 ppb Res. + PBO (12-hr)

Discussion

• In 10:30 ppb Res. + PBO 12-hr treatment, surviving crabs waved chelipeds erratically and flipped upside-down– Dead crabs were found upside-

down having ejected their claws– Evidence of neuromuscular

dysfunction

• 10:30 ppb 3-hr treatment did not act as severely as the 10:30 12-hr– It is expected they endured

similar, but reduced, side effects

Discussion

• With poor motor skills, blue crabs were less able to catch active prey

• Consistent with the 10:30 3-hr ppb exposure– Ate less and at a slower

pace

• Similar results to mercury studies

Unexpected Results

• 1:3 ppb Res. + PBO surprisingly ate significantly more than the control group– Was expected to eat less– Inconsistent with other studies

• Could have the opposite effect of the higher exposure (10:30 ppb)– Crabs could begin to consume

more, increasing predation pressure

Implications

• Pesticides could potentially change community structure– In contaminated waters, grass shrimp are able

to effectively avoid predators and partition their energy, favoring growth and reproduction

– Effect of contamination was offset by decrease in predation pressure

– Result was more numerous, larger shrimp

• With blue crabs not being able to target active prey, predation pressure on those prey species is decreased

(Reichmuth et al. 2009)

Implications

• Exposed to pesticides, blue crabs would not be able to forage well, having to select less optimal prey– Generalist diet would narrow– May not get proper nutrition

• Predation pressure would be relieved for many prey species who would then be allowed to increase in numbers– Community structure based on

predator-prey interactions would shift

(Weis et al. 1999, 2011)

Further Experimentation

• In the future I would repeat the experiment with increasing concentrations of Res. + PBO in order to see the trend in amount of shrimp alive per hour for each exposure time

• At what concentration of Res. + PBO do the crabs start feeling the negative effects?

• How do exposures above or below 1:3 ppb Res. + PBO affect foraging ability?

Works Cited• Williams, A. B. (1973). The Swimming Crabs of the Genus Callinectes (Decapoda: Portunidae). Fishery Bulletin 72: 685-692.• Sutton, G., and T. Wagner. (2007). Stock Assessment of Blue Crab (Callinectes sapidus) in Texas Coastal Waters. Texas Parks and

Wildlife Department Management Data Series No. 249.• Guillory, V., H. Perry, P. Steele, T. Wagner, W. Keithly, B. Pellegrin, J. Peterson, T. Floyd, B. Buckson, L. Hartman, E. Holder, and C. Moss,

(2001, October). The Blue Crab Fishery of the Gulf of Mexico, United States: A Regional Management Plan. Gulf States Marine Fisheries Commission.

• Pennington, P. L., J. W. Daugomah, A. C. Colbert, M. H. Fulton, P. B. Key, B. C. Thompson, E. D. Strozier, and G. I. Scott. (2001). Analysis of Pesticide Runoff From Mid-Texas Estuaries and Risk Assessment Implications for Marine Phytoplankton. Journal of Environmental Science and Health B36: 1-14.

• Weis, J. S., G. Smith, T. Zhou, C. Santiago-Bass, and P Weis. (2001). Effects of Contaminants on Behavior: Biochemical Mechanisms and Ecological Consequences. BioOne 51: 209-217.

• Reichmuth, J. M., R. Roudez, T. Glover, and J. S. Weis. (2009). Differences in Prey Capture Behavior in Populations of Blue Crab (Callinectes sapidus Rathburn) from Contaminated and Clean Estuaries in New Jersey. Estuaries and Coast, 32: 298-308.

• Weis, J. S., G. M. Smith, and T. Zhou. (1999). Altered predator/prey behavior in polluted environments: implications for fish conservation. Environmental Biology of Fishes 55: 43-51.

• Weis, J. S., G. Smith, and C. Santiago-Bass. (2000). Predator/prey interactions: a link between the individual level and both higher and lower level effects of toxicants in aquatic ecosystems. Journal of Aquaric Ecosystem Stress and Recovery 7: 145-153.

• Weis, J. S., L. Bergey, J. Reichmuth, and A. Candelmo. (2011). Living in a Contaminated Estuary: Behavioral Changes and Ecological Consequences for Five Species. BioOne 61: 375-385.

• Osterburg, J. S., K. M. Darnell, T. M. Blickley, J. A. Romano, D. Rittschof. 2012. Acute toxicity and sub-lethal effects of common pesticides in post-larval and juvenile blue crabs, Callinectes sapidus. Journal of Experimental Marine Biology and Ecology. 424-425: 5-14.

• Horst, M. N. and A. N. Walker. 1999. Effects of the Pesticide Morphogenesis and Shell Formation on the Blue Crab Callinectes sapidus. Journal of Crustacean Biology. 19: 699-707.

• Zulkosky, A. M., J. P. Ruggieri, S. A. Terracciano, B. J. Brownawell, and A. E. McElroy. (2005). Acute Toxicity of Resmethrin, Malathion, and Methoprene to Larval and Juvenile American Lobsters (Homarus americanus) and Analysis of Pesticide Levels in Surface Waters After Scourge, Anvil, and Altosid Application. BioOne 24: 795-804.

• World Health Organization. (2001). Piperonyl Butoxide (062). In Pesticide Residues in Food - 2001: Evaluations. Residues, Part 1 (pp. 607-705).

Photo/Image Sources• http://www.nola.com/• http://renegadehealth.com• Http://www.fairfaxcounty.gov • http://pested.ifas.ufl.edu/• http://ecdpw.org/pdf/pesticide%20info.label.msds/Scourge%204-

12%20Label.pdf• http://www.gcmlc.com• http://www.animalhdwalls.com• http://www.polartrec.com• http://www.nysm.nysed.gov/• http://4you.tulane.edu/• http://www.activistpost.com• http://www.divebums.com/• http://www.raesidecartoon.com• http://sadcrab.tumblr.com

Thank You

• Dr. Smee• Kaitlyn Schroeder-Spain & Kelly

Correia • Dr. Withers• Dr. Gardner• SURF program

Questions?