Robert E. Knowlton
Professor of Biology
Physiological Ecology of Marine Decapod Crustacea (adults
Department of Biological Sciences
The George Washington University
Lisner Hall 345, 2023 G Street, NW
Washington, D.C. 20052
Lab: (202) 994-9223
Office: (202) 994-6093
Fax: (202) 994-6100
Dept E-mail : firstname.lastname@example.org
B.A. in Biology, Bowdoin College, 1960
Ph.D. in Zoology, University of North Carolina at Chapel Hill, 1970
Experimental studies assessing the endocrinological mechanism
of control of developmental processes such as morphogenesis (changes
in morphology), including metamorphosis (the drastic transition from
larva to juvenile), molting (the periodic sloughing of the external
skeleton), and growth, using larvae of the “snapping shrimp”
Alpheus heterochaelis as a model system. Neurosecretory
tissue in the paired eyestalks is thought to be the main source
of a “molt-inhibiting hormone” that acts on another
organ which produces the hormone (20-hydroxyecdysone) that actually
brings about the molt, and a factor that regulates morphogenesis,
either directly or by acting on another organ that produces a “juvenile
hormone.” Accordingly, effects of eyestalk removal are being
Laboratory and field studies analyzing life histories and behavioral
responses of various species of the “grass shrimp” Palaemonetes
to differences in salinity, substrate, and cover (submergent vegetation).
These differences could contribute to habitat partitioning, allowing
the sympatric estuarine species P. pugio and P. vulgaris
to coexist. Osmotic relations, substrate preferences, and competitive
displacement have been suggested as factors determining the distribution
of these two species. Laboratory work includes salinity tolerance
experiments (adults and larvae), selection of substrate types and
vegetative covers with and without predators present, and one-on-one
interaction trials (to determine aggression). Field work consists
of periodic sampling of grass shrimp populations from various localities
in the mid-Atlantic and assessment of structural, reproductive,
and developmental characteristics.
Descriptions of larval instars (stages) of various species of
shrimps in families Alpheidae, Palaemonidae, Hippolytidae.
Survey of invertebrate and plant communities in saline conduit
lakes of San Salvador, Bahamas.
2006. [with D. Marshalonis and H. Merchant] Acute toxicity of Permethrin to four populations of ovigerous grass shrimp, Palaemoneter pugio Holthuis. Bulletin of Environmental Contamination and Toxicology, 77:543-550.
2004. [with C.K. Vargo] The larval morphology of Palaemon
floridanus Chace, 1942 (Decapoda, Palaemonidae) compared to
other species of Palaemon and Palaemonetes,
Crustaceana, 77: 683-715.
2002. [with H. H. Ganz] Reproductive differences among Delmarva
grass shrimp (Palaemonetes pugio and P. vulgaris)
populations, Virginia Journal of Science, 53: 35-49.
2002. [with P. S. Gross] Morphological variations among larval-postlarval
intermediates produced by eyestalk ablation in the snapping shrimp
Alpheus heterochaelis Say. Biological Bulletin, 202: 43-52.
2001. [with H. C. Merchant and R. N. Khan] The effect of macrophytic
cover on survival of Palaemonetes pugio and P. vulgaris
(grass shrimp) in the presence of predatory Fundulus heteroclitus
(killifish). Contributions to Zoology, 70: 61-71.
1999. [with P. S. Gross] Variation in larval size after eyestalk
ablation in larvae of the snapping shrimp Alpheus heterochaelis.
Journal of Crustacean Biology, 19: 8-13.
1997. [with R. N. Khan and H. C. Merchant] Effects of macrophytic
cover upon the distribution of grass shrimp Palaemonetes pugio
and Palaemonetes vulgaris. Invertebrate Biology, 116: 243-247.
1997. [with P. S. Gross] The effect of eyestalk ablation on molting
in larvae of the snapping shrimp Alpheus heterochaelis
Say. Invertebrate Reproduction and Development, 32: 119-126.
1995. [with R. N. Khan and H. C. Merchant] Distribution of two sympatric
species of grass shrimp, Palaemonetes pugio and Palaemonetes
vulgaris, in relation to homogeneous and heterogeneous aquarium
substrates. Journal of the Elisha Mitchell Scientific Society, 111:
1995. [with M. R. Alavi] The larval morphology of Lysmata anchisteus
Chace (Crustacea Decapoda) compared with other Lysmata
species. Caribbean Journal of Science, 31: 289-310.
1995. [with R. N. Khan, P. A. Arguin, T. A. Aldaghlas, and R. Sivapathasundram]
Factors determining distribution and abundance of Palaemonetes
pugio and P. vulgaris (grass shrimp) along Delmarva
shores. Virginia Journal of Science, 45: 231-247.
1994. Effects of larval eyestalk extirpation on morphogenesis and
molting in the snapping shrimp Alpheus heterochaelis Say.
Journal of Experimental Zoology, 270: 162-174.
130 - Invertebrate Zoology, Fall
167 - Marine Biology, Spring
168 - Tropical Marine Biology, Spring, even years
169 - Applied Marine Ecology, Spring, odd years
-Seminar: Invertebrate Zoology, Fall, even years
Recent Graduate Students:
Daniel Marshalonis, M.S., 2003: “ Acute effects of Permethrin
on four populations of grass shrimp, Palaemonetes pugio.”
Ronald B. Gallin, Ph.D., 2002: “Effects of salinity and temperature
on survival and behavior of two sympatric species of grass shrimp,
Palaemonetes pugio and Palaemonetes vulgaris, and implications
of these effects on their distribution at Point Lookout State Park,