Darnell Lab

Marine Invertebrate Ecophysiology, Behavior, and Fisheries

My research focuses on the environmental constraints imposed on marine and estuarine invertebrates. More specifically, this encompasses (1) physiological, behavioral, and ecological responses to environmental change and environmental stress, (2) environmental effects on life histories, distributions, and population dynamics, and (3) anthropogenic impacts on organism-environment interactions. My research lies at the intersection of several disciplines and combines field and laboratory experimentation with quantitative and spatial analyses of long-term datasets to better understand the interactions between marine organisms and their environments. This research also has a strong applied focus, using ecophysiological approaches to address fisheries management and conservation questions. I work closely with local and regional management agencies to improve our understanding and management of coastal invertebrate species.


12/7/15: The lab is growing! In January, Sarah Cunningham will be joining us as lab manager and Helen Olmi and Lennah Shakeri will be entering our M.S. program.

8/18/15: Louisiana Sea Grant has recommended our proposal "Migratory movements and fishing mortality of the Louisiana blue crab spawning stock" for funding in the 2016-2018 omnibus funding competition. Pending final approval, we look forward to starting this project in the spring, tagging 6,000 female blue crabs in the Pontchartrain and Terrebonne Basins.

8/1/15: Our collaborative proposal with The Water Institute of the Gulf, "Linking blue crab abundance, growth, and mortality to marsh fragmentation and submerged aquatic vegetation cover", has been funded by NOAA through the Saltonstall-Kennedy Program. Collaborators at the Water Institute include PI Tim Carruthers and Co-PIs Kelly Darnell and Ann Hijuelos.

8/1/15: Our proposal "Large-scale movements, spawning locations, and structure of the Gulf of Mexico blue crab spawning stock" has been funded by NOAA through the Saltonstall-Kennedy Program. This project is a collaboration with Elizabeth North of UMCES Horn Point Lab and includes a large-scale mark-recapture study with a goal of tagging 25,000 crabs Gulf-wide.

7/20/15: Our manuscript "Thermal ecology of the fiddler crab Uca panacea: Thermal constraints and organismal responses" has been published in the Journal of Thermal Biology.

6/16/15: Our manuscript "Temperature-dependent growth and molting in early juvenile blue crabs, Callinectes sapidus" has been accepted for publication in the Journal of Shellfish Research.


Large-scale movements, spawning locations, and structure of the Gulf of Mexico blue crab spawning stock

Blue crabs support the 9th most valuable commercial fishery in the U.S., with 2013 coastwide landings of over 60,000 metric tons (132 million lbs.) for a wholesale value of over $191 million. Blue crab abundance and commercial landings, however, are highly variable from year to year and many states have seen large declines in crab harvests in recent years. Management efforts for this species typically take place on a state-by-state basis and have been hindered by a lack of information on stock structure and boundaries. Difficulties in assessing stock structure and boundaries have arisen due to a lack of information on large-scale movements of adult crabs and larval dispersal patterns and unclear and often conflicting population genetic information for the species. A collaborative project with Dr. Elizabeth North (UMCES) as well as all five Gulf states fisheries agencies, this project uses a Gulf-wide mark-recapture study of spawning female blue crabs, combined with spatial analyses of state and regional fishery-independent survey data, to better understand the structure and boundaries of the blue crab stock(s) in the Gulf of Mexico.

Linking blue crab abundance, growth, and mortality to marsh fragmentation and submerged aquatic vegetation cover

Louisiana supports the largest blue crab fishery in the Gulf of Mexico, yet is is experiencing unprecedented loss of salt marsh nursery habitats due to a combination of sea level rise, subsidence, saltwater intrusion and reduced sediment inflow. The overarching goal of this project is to assess the effects of marsh fragmentation and associated changes in submerged plant distribution on blue crab abundance, growth and mortality, and improve existing habitat suitability models to increase understanding of the consequences of landscape change, either degradation or restoration, for the blue crab fishery. This project is a collaboration with Tim Carruthers, Kelly Darnell, and Ann Hijuelos at The Water Institute of the Gulf.

Population-level consequences of phenotypic plasticity in crustacean reproduction

Phenotypic plasticity in maternal investment and reproductive traits can be driven by environmental fluctuations or changes in population density and demography, and can have important consequences for performance and fitness of offspring. These effects can scale up to affect abundance, distribution, and population dynamics. Crustaceans in particular exhibit an astounding diversity of reproductive strategies and degrees of maternal investment, and often show remarkable plasticity in response to environmental conditions.. Research in this area is focused on phenotypic plasticity in reproductive traits and behaviors in response to exploitation, environmental stochasticity, climate change, and range shifts (including both anthropogenic and climate-triggered invasions of novel habitats) and also considers the impacts of reproductive plasticity and maternal investment on performance and survival of early life history stages, stages that typically experience high mortality.

Ecology, physiology, and behavior of migration

Marine organisms often have migratory life cycles, with migratory ability optimized by complex interactions between physiological changes, orientation mechanisms, and movement behaviors. My long-term research interests in migratory ecology are focused on the mechanisms that optimize migratory ability of both adults and larvae under a variety of biotic and abiotic conditions and the implications of these mechanisms for the abundance and distribution of the species. I am especially interested in species that use selective tidal-stream transport to increase migratory ability or decrease the energetic costs of migration. This works involves a combination of laboratory behavioral experiments to examine migratory mechanisms and decision rules and multiple telemetry techniques to monitor migratory behavior, routes, and timing in the field.

Ecological consequences of sexual selection and sexual dimorphism

The form of a secondary sexual trait is determined by the complex interplay between sexual selection and natural selection, which interact to facilitate or constrain the evolution of sexually selected traits. For example, sexual selection often favors exaggerated male traits, armaments, or ornaments that confer reproductive advantages, but these exaggerated traits may impose ecological or physiological costs on the male. Natural selection thus often limits the degree of exaggeration of the trait. Conversely, in certain cases, sexual dimorphism can arise, be maintained, or even be enhanced because of ecological differences between the sexes. Thus, the form and degree of sexual dimorphism are shaped by both sexual and natural selection and must be considered in the context of multiple, interacting selective pressures. Research in this area has focused on ecological consequences of the sexually dimorphic major claw of fiddler crabs, especially the role of the major claw in heat transfer and thermoregulation.
-BBC Nature, ScienceDaily, and Science News coverage of Darnell and Munguia (2011).

Behavioral, physiological, and life history responses to climate change

Ocean temperatures and coastal climates are rising, and organisms will a number of challenges, including changes in heat and desiccation stress, and synchronization of mating and gamete cycles, and shifts in phenology. The degree to which species are impacted by a changing climate, however, will depend on the species’ adaptability, acclimation ability, and capacity for behavioral thermoregulation, all of which can buffer effects of climate change. Research in this area has focused on understanding responses to thermal shifts and thermal stress in the context of predicting future responses to climate change, focusing on a number of crustaceans including fiddler crabs and blue crabs.

Biological timing and endogenous rhythmicity

Regardless of habitat, organisms encounter numerous environmental cycles on a variety of temporal scales, from tidal cycles of salinity and hydrostatic pressure (for marine/estuarine organisms) to seasonal cycles of photoperiod, temperature, and food availability. Endogenous biological rhythms allow an organism to alter physiology or behavior in anticipation of these cycles, rather than in response to these cycles. I have previously examined endogenous biological rhythms in blue crabs, amphipods, fiddler crabs, and terrestrial crabs. My interests in biological rhythms lie in the functional significance of these rhythms as adaptations to fluctuating environmental conditions, as well as the entrainment cues used for synchonization of rhythms in marine animals.


Samantha Hicks

Samantha joined the lab as an M.S. student in Fall 2014 and is investigating maternal care behaviors in blue crabs, including proximate cues underlying egg ventilation behaviors and the costs and benefits of maternal care behaviors.

Adam Kemberling

Adam joined us in August 2015. Adam will be examining offshore movements and habitat use of spawning female blue crabs in the Gulf of Mexico.

Abby Kuhn

Abby also joined us in August 2015, and will be examining potential impacts of climate change on crustacean growth and maturation rates.

Helen Olmi

Helen joined us in January 2016, and will be working on the LA Sea Grant-funded project investigating migratory movements and fishing mortality of the LA blue crab spawning stock.

Lennah Shakeri

Lennah joined us in January 2016, coming from a position with USGS in Olympia, WA. Lennah will be examining effects of habitat fragmentation on blue crab populations.


Please contact me for reprints if not linked below. * indicates undergraduate student co-author

(19) Cunningham, S.R.*, M.Z. Darnell. 2015. Temperature-dependent growth and molting in early juvenile blue crabs, Callinectes sapidus. Journal of Shellfish Research 34:505-510. Link

(18) Darnell, M.Z., H.S. Nicholson*, P. Munguia. 2015. Thermal ecology of the fiddler crab Uca panacea: Thermal constraints and organismal responses. Journal of Thermal Biology 52: 157–165. Link

(17) Darnell, M.Z., K.K. Fowler*, P. Munguia. 2013. Sex-specific thermal constraints on fiddler crab behavior. Behavioral Ecology 24: 991-1003. Link

(16) Kronstadt, S.M.*, M.Z. Darnell, P. Munguia. 2013. Background and temperature effects on Uca panacea color change. Marine Biology 160: 1373-1381. Link

(15) Darnell, M.Z. 2012. Ecological physiology of the circadian pigmentation rhythm in the fiddler crab Uca panacea. Journal of Experimental Marine Biology and Ecology 426-427: 39-47. Link

(14) Darnell, M.Z., T.G. Wolcott, D. Rittschof. 2012. Environmental and endogenous control of selective tidal-stream transport behavior during blue crab Callinectes sapidus spawning migrations. Marine Biology 159: 621-631. Link

(13) Darnell, M.Z., P. Munguia. 2011. Thermoregulation as an alternate function of the sexually dimorphic fiddler crab claw. The American Naturalist 178: 419-428. PDF

(12) Hines, A.H., E.G. Johnson, M.Z. Darnell, D. Rittschof, T.J. Miller, L.J. Bauer, P. Rodgers, R. Aguilar. 2010. Predicting effects of climate change on blue crabs in Chesapeake Bay. In: Kruse, G.H., G.L. Eckert, R.J. For, R.N. Lipcius, B. Sainte-Marie, D.L. Stram, D. Woodby (eds) Biology and Management of Exploited Crab Populations Under Climate Change. Alaska Sea Grant College Program, Fairbanks. PDF

(11) Rittschof, D., M.Z. Darnell, K.M. Darnell, M. Goldman, M.B. Ogburn, R.E. McDowell. 2010. Estimating relative abundance of the female blue crab spawning stock in North Carolina. In: Kruse, G.H., G.L. Eckert, R.J. For, R.N. Lipcius, B. Sainte-Marie, D.L. Stram, D. Woodby (eds) Biology and Management of Exploited Crab Populations Under Climate Change. Alaska Sea Grant College Program, Fairbanks. PDF

(10) Darnell, M.Z., K.M. Darnell, R.E. McDowell, D. Rittschof. 2010. Postcapture survival and future reproductive potential of ovigerous blue crabs Callinectes sapidus caught in the central North Carolina pot fishery. Transactions of the American Fisheries Society 139: 1677-1687. PDF

(9) Darnell, M.Z., D. Rittschof, R.B. Forward Jr. 2010. Endogenous swimming rhythms underlying the spawning migration of the blue crab, Callinectes sapidus: ontogeny and variation with ambient tidal regime. Marine Biology 157: 2415-2425. PDF

(8) Darnell, M.Z., D. Rittschof. 2010. Role of larval release pheromones and peptide mimics in abdominal pumping and swimming behavior of ovigerous blue crabs, Callinectes sapidus. Journal of Experimental Marine Biology and Ecology 391: 112-117. PDF

(7) Darnell, M.Z., D. Rittschof, K.M. Darnell, R.E. McDowell. 2009. Lifetime repoductive potential of female blue crabs Callinectes sapidus in North Carolina, USA. Marine Ecology Progress Series 394: 153-163. PDF

(6) Forward Jr, R.B., M.H. Bourla*, M.Z. Darnell, J.H. Cohen. 2009. Entrainment of the circadian rhythm of the supratidal amphipod Talorchestia longicornis by light and temperature: mechanisms of detection and hierarchical organization. Marine and Freshwater Behaviour and Physiology 42: 233-247. PDF

(5) Ramach, S.M., M.Z. Darnell, N.G. Avissar, D. Rittschof. 2009. Habitat use and population dynamics of blue crabs, Callinectes sapidus, in a high-salinity embayment. Journal of Shellfish Research 28: 635-640. PDF

(4) Darnell, M.Z., M.B. Ogburn, H. Diaz. 2008. A novel running wheel apparatus to monitor locomotor rhythms in land crabs. Marine and Freshwater Behaviour and Physiology 41: 205-210. PDF

(3) Welch, M.E., M.Z. Darnell, D.E. McCauley. 2006. Variable populations within variable populations: quantifying mitochondrial heteroplasmy in natural populations of the gynodioecious plant Silene vulgaris. Genetics 174: 829-837. PDF

(2) Forward Jr, R.B., J.H. Cohen, M.Z. Darnell, A. Saal. 2005. The circatidal rhythm in vertical swimming of female blue crabs, Callinectes sapidus, during their spawning migration: A reconsideration. Journal of Shellfish Research 24: 587-590. PDF

(1) McCauley, D.E., M.F. Bailey, N.A. Sherman, M.Z. Darnell. 2005. Evidence for paternal transmission and heteroplasmy in the mitochondrial genome of Silene vulgaris, a gynodioecious plant. Heredity 95: 50-58. PDF


Marine and Environmental Biology I (BIOL 551) is a core course in our M.S. program in Marine and Environmental Biology. My goals for this course are for students to to gain a thorough understanding of ecological principles from readings and discussions of foundational papers and to stimulate critical thinking about ecological theory, experimental design, and the current state of research in the field. This is a discussion-based course with discussions focusing on the primary literature, including both foundational papers as well as more current papers. The 2015 syllabus can be downloaded here.

Introduction to Marine Biology (BIOL 283/284) is offered during the Fall semester. This course has two primary objectives. The first is for students to gain an understanding of and appreciation for life in the the marine environment. The second goal is for students to develop a mechanistic understanding of the processes structuring marine populations, communities, and ecosystems. We will take a process-based approach to study the diversity of life in the oceans, the interactions between these organisms, and the interactions between organisms and their environment. The 2015 syllabi can be downloaded here (Biol 283, lecture) and here (Biol 284, lab).

Invertebrate Zoology (BIOL 354) is offered during the Spring semester. The primary objective of this course is for students to gain an understanding of and appreciation for the diversity of invertebrate life in marine, freshwater, and terrestrial environments. We will work our way through the invertebrate phyla from Porifera to Chordata, focusing on form, function, and phylogeny. In addition to lectures, dissections and labs will be used to explore invertebrate anatomy, morphology, and behavior, and field trips to local habitats will be used to collect invertebrate organisms and explore relationships between invertebrates and their environment. The 2016 syllabus can be downloaded here.

Marine Field Ecology is offered at LUMCON during even-year summers. This course focuses on introducting students to the marine environment through a number of excursions to local habitats throughout the Louisiana Coastal Zone. Students spend the first two weeks of the course exploring the local environment and learning basic principles of marine ecology. The second two weeks of the course are devoted to original research projects conducted in groups of 2–3 students. The 2014 syllabus can be downloaded here.

Prior to coming to Nicholls, I taught several courses at the University of Texas at Austin, including Marine Invertebrates, Marine Environmental Science, and Laboratory Studies in Marine Ecology.

Research Photos


Zack Darnell
Department of Biological Sciences
Nicholls State University
P.O. Box 2021
Thibodaux, LA 70310
Phone: (985) 448-4709
Email: zachary.darnell@nicholls.edu