James R. and Helen Lee Billingsley Professor of Marine Biology
130C Druckenmiller Hall
Current teaching schedule available on the public course finder.
(*indicates undergraduate student co-author)
Johnson AS, Salyers JM*, Alcorn NJ*, Ellers O, Allen JD (2013) Externally visible fluorochrome marks and allometries of growing sea urchins. Invertebrate Biology. 132:251-269.
Pfister, A*, Johnson, A, Ellers, O, Horch, HW (2013). Quantification of dendritic and axonal growth after injury to the auditory system of the adult cricket Gryllus bimaculatus. Front. Physio. 3:367. doi: 10.3389/fphys.2012.00367 (online research article, 861 views: http://journal.frontiersin.org/Journal/10.3389/fphys.2012.00367/full)
Ellers, O., Johnson, A.S. (2009) Polyfluorochrome marking slows growth only during the marking month in the green sea urchin Strongylocentrotus droebachiensis. Invert. Biol. DOI:10.1111/j.1744-7410.2008.00159.x.
*Selden, R., Johnson, A.S., Ellers, O. (2009) Crab scent induces thicker skeletons, smaller gonads and size-specific growth responses in sea urchins. Mar. Biol. 156:1057–1071 DOI : 10.1007/s00227-009-1150-0 pdf
*Butler, M., Johnson, A.S. (2004). Are melanized feather barbs stronger? J. Exp. Biol. 207: 285-293
*Lohrmann NL, Logan BA, Johnson AS (2004) Seasonal acclimatization of antioxidants in Chondrus crispus and Mastocarpus stellatus, two co-occurring red algae with differing winter tolerances. Biol Bull 2004 207: 225-232.
Johnson, A.S., Ellers, O., *Lemire, J., *Minor, M., *Leddy, H. (2002). Sutural loosening and skeletal flexibility during growth: determination of drop-like shapes in sea urchins. Proc. R. Soc. Lond. B, 269: 215-220.
*Pratt, M.P., Johnson, A.S. (2002). Strength, Drag, and Dislodgement of Two Competing Intertidal Algae from Two Wave Exposures and Four Seasons. J. Exp. Mar. Biol. Ecol. 272: 71-101
Johnson, A.S. (2001). Drag, drafting, and mechanical interactions in canopies of the red alga Chondrus crispus. Biological Bulletin 201: 126-135.
*Leddy, H.A., Johnson, A.S. (2000). Walking vs. breathing: mechanical differentiation of sea urchin podia corresponds to functional specialization. Biological Bulletin 198: 88-93.
Ellers, O, Johnson, A.S., Moberg, P. (1998). Sutural strengthening of urchin skeletons by collagenous sutural ligaments. Biological Bulletin 195: 136-144.
Johnson, A. (1997). Flow is genet and ramet blind: Consequences of individual, group and colony morphology on filter feeding and flow. Proceedings of the 8th International Coral Reef Symposium 2: 1093-1096.
Johnson, A.S. and Koehl, M.A.R. (1994). Maintenance of environmental stress factor in different flow habitats: Thallus allometry and material properties of a giant kelp. Journal of Experimental Biology 195: 381-410. Abstract; Full article
Johnson, A.S. (1993). Sag-mediated modulated tension in terebellid tentacles exposed to flow. Biological Bulletin 185: 10-19.
Johnson, A.S. and K.P. Sebens (1993). Consequences of a flattened morphology: Effects of flow on feeding rates of the scleractinian coral Meandrina meandrites (Linnaeus 1758). Marine Ecology Progress Series 99: 99-114.
*Trussell, G.C., A.S. Johnson, S.G. Rudolph, and E.S. Gilfillan (1993). Resistance to dislodgment: Habitat and size-specific differences in morphology and tenacity in an intertidal snail. Mar. Ecol. Prog. Ser. 100: 135-144.
Dudgeon, S.R. and A.S. Johnson (1992). Thick versus thin: Thallus morphology and tissue mechanics influence differential drag and dislodgement of two co-dominant seaweeds. J. Exp. Mar. Biol. Ecol. 165: 23-43.
Sebens, K.P. and A.S. Johnson. (1991). The effect of water movement on prey capture by reef corals. Hydrobiologia 216/217: 247-248.
Sebens, K.P. and A.S. Johnson. (1991). Effects of water movement on prey capture and distribution of reef corals. Hydrobiologia 226: 91-101
Johnson, A.S. (1990). Flow around phoronids: Consequences of a neighbor to suspension feeders. Limnol. and Oceanogr. 35(6): 1395-1401.
Johnson, A.S. (1988). Hydrodynamic study of the functional morphology of the benthic suspension feeder, Phoronopsis viridis (Phoronida). Mar. Biol. 100: 117-126.
Dickinson PS, Dickinson ES*, Harmon KE*, Qu X*, Johnson AS, Ellers O. (2015) Mechanisms of sensory feedback and interactions with neuromodulators in a rhythmic pattern generator. March 2015, Boston, MA, Experimental Biology, Poster #841.4.
Horch HW, Saidenbert L*, Chong M*, Fiorillo B*, Vergara-Benitex J*, Zhand A*, Pfister A*, Ellers O, Johnson A (2014). Exploration of two different compensatory strategies for recovery from injury in the adult cricket CNS. Neuroscience Annual Meeting, Nov 15-19, Wash DC.
Harmon K*, Chin-Purcell M*, Dickinson ES*, Hartley TM*, Ellers O, Johnson AS, Dickinson, PS (2014). Mechanisms and effects of stretch feedback in the heart of the American lobster, Homarus americanus. Neuroscience Annual Meeting, Nov 15-19, Wash DC.
Ellers O, Johnson AS, Guttenplan K*, Motokawa T (2014) The bounce in a seastar's step: classifying gaits in underwater legged locomotion Integrative and Comparative Biology (2014) 54 (suppl 1): e59 doi: 10.1093/icb/icu/008 (published abstract).
Dickinson E*, Johnson AS, Ellers O; Dickinson PS (2014). Cardiac muscle in Homarus americanus responds differently to loading in transverse and longitudinal directions. Integrative and Comparative Biology (2014) 54 (suppl 1): e59 doi:10.1093/icb/icu008
Ellers O, Johnson AS, Guttenplan K*, Motokawa T (2013) Does the starfish Protoreaster nodosus use a pendular gait while walking underwater? Japan Zool. Soc. Symp., Tokyo Inst. of Tech. Mar 16, 2013
Horch HW, Johnson A, Ellers O, Berry K*, Low I*, Sangal R*, Pfister A* (2012). Sexually dimorphic dendritic responses to deafferentation and the potential role of semaphorins. Society for Neuroscience Abstracts Volume: 42
Askins, M*, Lonati, G,* Guttenplan, K,* Fahey, A,* Johnson, A, Ellers, O. (2012) Externally visible polyfluorochrome marking of urchins: growth comparisons between lab-reared and tidepool urchins. Integrative and Comparative Biology, Poster Presentation, Annual Meeting Abstract, Jan. 3-7, 2012 Charleston, NC
Johnson, A.S., Ellers, O., (2010) Precise measurement of growth using multiple fluorochrome markers, the cubed root of weight and a new growth function. Integrative and Comparative Biology, Annual Meeting, Jan. 3-7, 2010, Seattle, WA
Ellers, O., Yoshimura, K., Motokawa, T., Johnson, A.S. (2010). Why not walk faster, underwater? Integrative and Comparative Biology, Annual Meeting Abstract, Jan. 3-7, 2010, Seattle, WA
Norton, E.*, Ellers, O., Johnson, A.S. (2010). Testing an inverted pendulum model for underwater walking in the crab Carcinus maenus. Integrative and Comparative Biology, Annual Meeting Abstract, Jan. 3-7, 2010, Seattle, WA
Brasili, A.*, Johnson, A.S. (2010). Temperature and size-dependent growth in a marine ectotherm: the green sea urchin Strongylocentrotus droebachiensis. Integrative and Comparative Biology, Annual Meeting Abstract, Jan. 3-7, 2010, Seattle, WA
Ellers, O., Yoshimura, K., Motokawa, T., Johnson, A.S. (2009) An inverted pendulum model for underwater walking. Integrative and Comparative Biology, Annual Meeting Abstract 74.1, Jan. 3-7, 2009, Boston, MA
Johnson, A., Selden, R.*, Ellers, O. (2009) Crab scent induces thicker skeletons, smaller gonads and size-specific adjustments in growth rate in sea urchins. Integrative and Comparative Biology, Annual Meeting Abstract 74.1, Jan. 3-7, 2009, Boston, MA
Johnson, A.S., Ellers, O., Butler, M.* (2006). Barbs of a feather bend (and twist) together. Integr. Comp. Biol. 46(1): e70; doi:10.1093/icb/icl056
Lake, B.* Johnson, A.S. Mauck, R.A. (2006) Influence of orientation and flow speed on feeding behavior and metabolism of the barnacle Semibalanus balanoides. Integr. Comp. Biol. 46(1): e219; doi:10.1093/icb/icl056
Johnson, A.S., Ellers, O. (2006) A new fluorochrome-based identification tag for sea urchins for use in a hatchery and lease-site aquaculture. Northeast Aquaculture Conference and Exposition. Mystic, Connecticut. December, 2006.
Ellers, O., Johnson, A.S. (2006). Temperature determines size and time-to-size in urchins: calibration of size-temperature effects in marine ectotherms. International Echinoderm Conference, University of New Hampshire, August 2006.
Johnson, A.S., Ellers, O., *Wright, M., *Selden, R, *Stranges, B. (2006). Is there an oxygen-limited lag phase in early growth in sea urchins, Strongylocentrotus droebachiensis? International Echinoderm Conference, University of New Hampshire, August 2006.
Johnson, A.S., Ellers, O., *Wright, M., *Stranges, B. (2005). Implications of transport processes and 2/3 power metabolic scaling to Bertalanffy and bimodal growth in sea urchins. Integr. Comp. Biol. 44(6):709
Note that as of October 2012 this is only working in Internet Explorer; we are working on a fix for other browsers.
This demonstration allows the user to manipulate the value of physically important variables in the system and the output is the motion of a pendulum as defined by the angular position of the pendulum bob relative to vertical.
The damped pendulum model is programmed in Mathematica by Olaf Ellers and is based on the math published by others in the following paper:
Neill D, Livelybrooks D & Donnelly R (2007). A pendulum experiment on added mass and the principle of equivalence. Am. J. Phys. 75(3): 226-229. Neill et al. (2007) also provide an experimental test of the calculations.
Kids, dogs, cats, music, reading, walking, gymnastics, light flecks on new spring leaves, thimble moon on night of first frost, full moon setting at the edge of an autumn morning mist, rain falling through a leafy forest canopy
A demipyramid ossicle (jaw bone) from the sea urchin Strongylocentrotus droebachiensis. The calcite ossicle was marked first with tetracycline and then with alizarin complexone. These fluorescent markers become incorporated into the growing edge of the ossicle. The marks are four days apart. Image by A. Johnson and O. Ellers. See: Ellers, O., Johnson, A.S. (2009) Polyfluorochrome marking slows growth only during the marking month in the green sea urchin Strongylocentrotus droebachiensis. Invert. Biol. DOI:10.1111/j.1744-7410.2008.00159.x.