horseshoe crab, Limulus polyphemus, is a versatile
model for scientific research. Scientists in a wide variety
of fields including ecology, microbiology, biotechnology, pharmacology,
immunology, and neurophysiology have focused their investigations
on this extraordinary marine creature. As it is the most intensively
studied marine invertebrate, you might think that we already
know everything there is to know about the horseshoe crab.
every year, exciting new discoveries are being reported around
the country. What questions are scientists asking this year?
Where can you go to study horseshoe crabs? Click on the labeled
states to learn more about current horseshoe crab research!
University of California, Santa Barbara
Dr. Robert Jacobs investigates the biochemical processes that
cause inflammation or allergic responses in humans. He uses
horseshoe crab amoebocytes (circulating blood cells) as a
model to understand what intercellular events contribute
to the immune response, and what biochemical reactions are
required for healing wounds. California Sea Grant has provided
funding for this research.
University of California, Davis
Dr. Peter Armstrong studies proteins in the immune system of
Limulus polyphemus. Recently, he discovered that mucous
secreted from the carapace prevents fouling by organisms such
as blue-green algae, tube worms, and barnacles. The mucous
contains multiple proteins that help protect the horseshoe
crab shell from biological invaders. Currently, Dr. Armstrong
is investigating the role of a blood plasma protein, alpha2-macroglobulin,
in the immune response. This protein may protect the horseshoe
crab by preventing the harmful bacteria trapped inside the
clot from escaping. Funding for this research has been provided
by the National Science Foundation (NSF).
Sacred Heart University, Fairfield, Connecticut
Project Limulus is a research program investigating the population dynamics of horseshoe crabs in Long Island Sound (LIS). It is run by the Department of Biology at Sacred Heart University in Fairfield, Connecticut by Drs. Jennifer Mattei, Mark Beekey and Kirk Bartholomew. This collaborative research effort, involves federal, state, nonprofit, and community groups while promoting science literacy across all age groups.
Currently, our research focuses on the genetic diversity of the horseshoe crab population, migration patterns, mating behaviors, assessment of spawning success, and links to other species in LIS. Our data are used by state agencies for management purposes. Over the past eight years, Project Limulus has trained and taught more than 40 undergraduate research assistants, 2000 elementary and secondary school students, 250 teachers, and has developed an active volunteer network of well over 500 concerned citizens who participate each year in tagging and spawning surveys.
Our latest publication:
Mattei, J., Beekey, M.A., Rudman, A., Woronik, A. 2010. Reproductive behavior in horseshoe crabs: Does density matter? Current Zoology 56(5): 634-642.
Contact: Jennifer H. Mattei, Ph.D., Associate Professor
Department of Biology, Sacred Heart University
Fairfield, CT 06825
University of Delaware, College of Earth, Ocean, and Environment, Lewes,
and the Delaware Biotechnology Institute,
Nancy Targett and
Dr. Pamela Green are
investigating an economical artificial bait that could be used
as a substitute for adult female horseshoe crabs in the American
eel and whelk fisheries. They are working
to produce the protein from the horseshoe crab that attracts
eels and whelks and then incorporate it into an artificial
bait product. This research is supported by Delaware
Patrick Gaffney, at the University of Delaware is collaborating
James Pierce, at the University of the Sciences in
Philadelphia, to investigate the population genetics of Limulus
Recently they examined DNA from Chesapeake and Delaware Bay
horseshoe crabs and determined the two populations to be genetically
The Delaware National Estuarine Research Reserve (DNERR)
DNERR has been conducting studies of horseshoe crab egg densities
since 1997. The DNERR is a cooperative program between the Delaware
Department of Natural Resources and Environmental Control and the
National Oceanic and Atmospheric
Administration. The goal of the
program is to establish, protect, and manage natural estuarine
habitats for research and education. The purpose of this multi-year
study is to:
1. Develop a statistically sound methodology for sampling, extracting,
and enumerating horseshoe crab eggs from beach sediments.
2. Develop an understanding of the role beach nourishment activities have on horseshoe crab egg densities.
3. Develop an understanding of between-beach differences in egg densities.
4. Evaluate the amount of horseshoe crab eggs available as food to migratory shorebirds.
5. Make recommendations regarding beach management for optimal horseshoe crab spawning habitat.
Horseshoe crab egg densities for each beach are estimated by
taking core samples of sand and extracting the eggs through a
multi-step process. The resulting egg numbers represent relative
abundance of eggs within the sand. Parameters such as sand grain-size
distribution, beach slope, and beach width are measured on each
beach. These measurements, paired with estimated egg densities,
may reveal important information about ideal beach conditions
for horseshoe crab spawning and egg survival. In turn, natural
resource managers can use this information to optimize beach
conditions for spawning horseshoe crabs.
Funding for this project has been provided by the Delaware
National Estuarine Research Reserve,
Coastal Programs, the Delaware
Division of Fish and Wildlife, the National
Oceanic and Atmospheric Administration,
NOAA's National Ocean
Service, and the U.S. Fish and
Wildlife Service. For more information, contact Susan Love at email@example.com or
USGS Biological Resource Division,
Division of Fish and Wildlife, and the
Delaware National Estuarine Research
Biological Resources Division, in cooperation
with the Delaware
Division of Fish and Wildlife and the Delaware
National Estuarine Research Reserve, is conducting
a study to better understand the factors that determine the
distribution of horseshoe crab eggs across the beach profile
and availability of these eggs to shorebirds.
Horseshoe crabs lay eggs in the sand to a depth where the eggs are sufficiently protected from the elements, including hungry birds. However, some eggs migrate to the surface of the sand, becoming available as food for shorebirds. The eggs can be brought to the surface by a number of different factors including beach morphology, weather, and wave action. In addition, it is thought that spawning horseshoe crabs play a role in egg migration to the surface by disturbing previously laid eggs.
The purpose of this study is to:
1. Determine the effect of beach characteristics, weather, and
level of spawning activity on egg availability to shorebirds.
2. Identify beach characteristics that affect egg availability.
3. Determine distribution of eggs in reference to high-tide line
and determine beach characteristics that affect egg location.
4. Use information on variation in egg distribution to make recommendations on protocol to effectively sample egg densities.
For more information, e-mail Dave Smith at firstname.lastname@example.org.
Delaware Division of Fish and Wildlife, Fisheries Section
Division of Fish and Wildlife, Fisheries Section, is
charged with management of tidal and non-tidal water fisheries,
and conducts a range of monitoring and research activities
each year. Relative abundance of both juvenile and adult
horseshoe crabs is monitored year-round by 30-foot and
16-foot trawl surveys. The Fisheries Section also collects
data regarding commercial landings of horseshoe crabs and
characterizes the commercial catch.
In addition, the Fisheries Section is:
1. Identifying juvenile horseshoe crab habitats in Delaware's
2. Estimating horseshoe crab fecundity.
3. Funding the Delaware Bay spawning survey coordinator and participating
in spawning surveys.
4. Participating in a joint study with the U.S. Fish and Wildlife
Service and Old Dominion University to establish a method to
reliably age horseshoe crabs using a lipofuscion technique.
5. Partially funding and cooperating in a large project to design
a pilot coastwide benthic horseshoe crab sampling program, delineate
the horseshoe crab stock using microsatellite DNA, identify techniques
to identify pre-recruits, and investigate the feasibility of
night time aerial videography.
6. Partially funding and cooperating in an initiative promoting
the use of bait bags.
7. Participating in the ASMFC process through the Management Board, Technical Committees, Stock Assessment Committee, and the Plan Development and Review Teams.
For more information, contact Stewart Michels at email@example.com.
Florida Institute of Technology, Melbourne
Gretchen Ehlinger is studying the ecology of horseshoe crabs
in the Indian River Lagoon to determine why the population
is declining and how it can be protected. Her research on
the distribution and movement of adult and larval horseshoe
crabs within the lagoon combined with identification of critical
habitat will benefit management of this multiple-use resource.
Her research has been supported in part by NASA and
the National Park Service.
University of Florida, Gainesville
Dr. Jane Brockmann studies
the behavior, natural history, and population biology of horseshoe
crabs in the Cedar Keys National Wildlife Refuge. She has also
investigated mating behavior and nest-site selection in Delaware
Bay. Her current research focuses on patterns in male mating
behavior. Do males use chemical cues to detect their mates? Why
do some females attract multiple males, when others only attract
a few? Dr. Brockmann's
research has been funded by the National
Science Foundation (NSF),
the University of Florida
Foundation, and the Division of Sponsored
University of Florida, Whitney Laboratory, St. Augustine
Barbara-Anne Battelle's research focuses on light sensitivity
in the retina of the horseshoe crab. Currently, she is investigating
the biochemical interactions between light-dark cycles and internal
(circadian) clocks that alter the retina, enabling the horseshoe
crab to see as clearly at night as it does during the day.
Northeastern Illinois University,
Mary Kimble studies embryonic development in horseshoe
crabs. Specifically, she is interested in the evolution of
homeotic genes that regulate embryonic development and the
roles they play in the primitive horseshoe crab embryo.
Purdue University, West Lafayette
Dr. Gerald S. Wasserman studies sensory coding using horseshoe crabs as
a model for understanding human vision.
University of Kansas
Dr. Rachel Moore is currently working on all aspects of horseshoe crab evolution including a phylogeny of fossil and recent horseshoe crabs, describing new fossil taxa and documenting their distribution over the last 400 million years. Researching their habitat preference throughout their evolution and their relationship to other living and extinct chelicerate groups is also part of this project.
University of Maryland Eastern Shore, and the
Fish and Wildlife Research Unit, Princess Anne
Dixie Bounds of CFWRU, and Monica Williams, a graduate student
at UMES, are studying the impact of horseshoe crab population
dynamics on migratory shorebird abundance. They are investigating
whether migratory shorebirds can locate suitable food resources
and habitat adjacent to Delaware Bay if the horseshoe crab population
were to collapse.
Joseph Margraf of CFWRU is evaluating current sampling methodologies to develop a population index for horseshoe crabs in Maryland and Delaware. He is also investigating techniques for estimating horseshoe crab egg densities, to assess the availability of eggs for migratory shorebirds.
Boston University Marine Program,
Marine Biological Laboratory, Woods Hole
Dr. Ruth Carmichael is
using stable-isotope analysis to determine habitat and food
preferences of horseshoe crabs in Pleasant Bay, Massachusetts.
The isotope analysis will help to evaluate the trophic position
of horseshoe crabs in the bay and how far they travel to forage.
Her research is supported by the Friends of Pleasant Bay.
Marine Biological Laboratory,
Woods Hole, and Charles River Laboratories
Norman Wainwright, at the Marine Biological Laboratory, is
working to understand the molecular defense mechanisms exhibited
by the horseshoe crab in response to invasion by bacteria, fungi,
and viruses. Several proteins found in Limulus hemocyte
and hemolymph display microbial binding properties that contribute
to antimicrobial defense. He also is collaborating with Charles
River Laboratories on the Endosafe®-PTS
(Portable Test System), a miniature machine no bigger than a
large calculator, that can use the horseshoe crab Limulus Amebocyte
Lysate (LAL) test to detect microbes on spacecraft and perhaps
even on Mars and other planets.
Research in Dr.
Daniel Gibson's lab examines the role of amino acid
neurotransmitters in muscle twitches, the effects of molting
hormones and pesticides on horseshoe crab growth and development,
and learning behavior in horseshoe crabs.
Worcester Polytechnic Institute, Worcester
Research in Dr.
Daniel Gibson's lab examines the role of amino acid neurotransmitters
in muscle twitches, the effects of molting hormones and pesticides
on horseshoe crab growth and development, and learning behavior
in horseshoe crabs.
University of New Hampshire, Durham
Dr. Winsor Watson investigates the influence of tidal and circadian
rhythms on mating behavior and locomotion in horseshoe crabs.
He is also interested in the role of pheromones in mate selection.
Plymouth State University
Dr. Chris Chabot is involved in collaborative research with undergraduate students at PSU and Dr. Win Watson, UNH. Their goal is to investigate the role of environmental factors as well as endogenous factors on locomotor activity in Limulus.
Rutgers University, New Brunswick
Dr. Robert Loveland investigates
the life history and ecology of horseshoe crabs, focusing on
conservation of this species. Recent research with undergraduate
students examined the relationship between mating behavior and
fouling patterns on the horseshoe crab carapace. New
Jersey Sea Grant has provided funding for this research.
In addition, Dr. Loveland collaborates with Dr.
University) and the Cape May Bird Observatory to estimate horseshoe
crab population trends based on egg density counts along New
Fordham University, New York City
Dr. Mark Botton studies
conservation biology of shorebirds and horseshoe crabs in the
Delaware Bay estuary. Recent research with undergraduate students
investigated the effects of visual impairment on male mating
success. Dr. Botton's
research interests also focus on the effects of heavy metal pollution
on horseshoe crab larvae and embryos. In addition, Dr. Botton
collaborates with Dr.
Loveland (Rutgers University) and the Cape
May Bird Observatory to estimate horseshoe crab population trends
based on egg density counts along New Jersey beaches. New
Jersey Sea Grant has provided funding for this research.
S.U.N.Y Upstate Medical University, Syracuse
Robert Barlow is investigating the role of vision in potential
mate selection. A "crabcam" mounted
on the horseshoe crab carapace records what the horseshoe crab
sees underwater. The recorded images are used to generate a computer
model which helps Dr. Barlow analyze how the horseshoe crab brain
processes signals transmitted from the eyes and optic nerve.
Funding has been provided by the National
Institutes of Health (NIH), the National
Science Foundation (NSF),
Research to Prevent Blindness, and
the Lions of Central New York.
University of North Carolina, Chapel Hill
Dr. Ken Lohmann and
graduate student Bill Irwin are investigating the beach-finding
mechanism in horseshoe crabs. Specifically, they are trying to
establish if horseshoe crabs use the Earth's magnetic field as
an orientation cue during seasonal migration to spawning beaches.
University of the Sciences in Philadelphia, Philadelphia
on the use of biotechnology to understand genomic organization
and evolution of homeobox genes and primitive immune systems
in the horseshoe crab. Homeobox
genes, and the proteins they encode, the homeodomain proteins,
have turned out to play important roles in the developmental
processes of many multicellular organisms. Recent research
in his lab includes a genetic analysis of the Delaware Bay
horseshoe crab population and the activity of an antimicrobial
peptide from horseshoe crabs against an oyster pathogen.
University of Rhode Island, Graduate School of Oceanography, Narragansett
Dr. M. J. James-Pirri surveys spawning densities and population
demographics (sex, size, age estimates) of horseshoe crabs in
Cape Cod, Massachusetts. Her studies will establish a set of
baseline data to evaluate long-term population trends in the
Cape Cod region. She also has developed a tagging
study to investigate whether horseshoe crabs return to their
native spawning beaches. She collaborates closely with the Massachusetts
Audubon Society, Wellfleet
Bay Wildlife Sanctuary, and Monomoy
National Wildlife Refuge. Her research is supported by the National
Marine Resources Research Institute, Charleston
Resources Research Institute (MRRI) is one of the
largest sections within the Marine Resources Division of the
South Carolina Department
of Natural Resources. MRRI coordinates
research on horseshoe crab population abundance and habitat requirements
in South Carolina. MRRI has developed a tagging program to monitor
horseshoe crab behavior, population characteristics, and mortality.
The institute is also gathering information on critical feeding,
spawning, and nursery grounds to assist in the management and
conservation of horseshoe crabs.
Virginia Institute of Marine Science, Gloucester Point
Fisheries scientist Bob Fisher is examining alternatives to horseshoe
crab bait for Virginia conch fisheries. Currently, he is investigating
whether waste from local seafood industries will provide an effective
binder matrix for alternative baits. He is also field-testing
mesh bait bags as a means to reduce the amount of horseshoe crab
bait used in conch pots. Funding has been provided by Virginia
Virginia Polytechnic Institute, Blacksburg
Jim Berkson and graduate student Beth
studying the population dynamics of Chesapeake Bay horseshoe
crabs. Berkson and Walls are also investigating techniques to
reduce horseshoe crab mortality in the biomedical industry, a
result of bleeding to obtain LAL. Both demographic studies and
LAL-related mortality estimates will provide valuable information
to develop effective management strategies for the horseshoe
crab population. Funding for this research has been provided
Whittaker, which is now part of the Cambrex
Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech
Title: Biochemical Profiles Of The Hemolymph Of The Horseshoe Crab, Limulus polyphemus.
Stephen A. Smith believes that while the horseshoe crab's "blue blood" and the composition of the LAL have been studied in detail, basic biochemical parameters of the hemolymph of the horseshoe crab are lacking. Thus, hemolymph from fifty adult (29 male and 21 female) horseshoe crabs was collected for analysis. Hemolymph samples were analyzed using an automated chemistry system. Results of the biochemistry parameters for the hemolymph of the horseshoe crab were: total protein (8.15 g/dl), glucose (58.5 mg/dl), creatinine (0.7 mg/dl), cholesterol (0.8 mg/dl), sodium (389.5 mEq/l), potassium (12.5 mEq/l), chloride (445.1 mEq/l), calcium (39.0 mg/dl), magnesium (96.1 mg/dl), phosphorus (3.4 mg/dl), triglycerides (5.3 mg/dl), amylase (9.3 U/l)), lipase (32.7 U/l), alkaline phophatase (12.1 U/l), aspartate aminotransferase (5.4 U/l) and gamma glutamyl transferase (0.92 U/l).
Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech
Title: Comparison Of Hemolymph Proteins From The Horseshoe Crab, Limulus polyphemus.
The horseshoe crab (Limulus polyphemus) has been described as one of the oldest living organisms on the planet, with it's closest relatives being in the Subphylum Chelicerata which contains the scorpions and spiders. To further examine this relationship, hemolymph from several adult horseshoe crabs was analyzed by SDS-PAGE and the protein bands separated. The bands were then compared to protein bands derived from the hemolymph of a scorpion, spider, lobster and blue crab. Results of the SDS-PAGE analysis of horseshoe crab hemolymph produced three major proteins that most likely represent the alpha-2 macroglobulin, hemocyanin and C-reactive protein, respectively. Western blot analysis was performed using a rabbit anti-horseshoe crab whole hemolymph antibody and the results demonstrated that the rabbit antibody clearly recognized all of the horseshoe crab protein bands in the gel. In addition, the rabbit anti-horseshoe crab antibody also recognized protein bands from the hemolymph of the scorpion and spider, but not those of the lobster and blue crab. This is further evidence that members of the Class Arachnida are more closely related to the horseshoe crab than are members of the Subphylum Crustacea. The title of this project is being conducted by Dr. Stephen A. Smith.
USGS, Leetown Science Center, and
Aquatic Ecology Laboratory, Kearneysville
Dr. David Smith is developing a statistically robust census to analyze trends in horseshoe crab spawning activity in Delaware Bay. This project is coordinated among federal and state agencies, academic institutions, and private industry in Maryland, Delaware, and New Jersey.
Cuttack, Orissa, India
Ashis Senapati is involved in a research project where Lysate of the Horseshoe crab will be collected from the sea of Orissa an eastern state of India and the lysate will be tested on some AIDS or HIV patients after taking blood samples.