Publications

Export 8 results:
Sort by: Author [ Title  (Desc)] Type Year
A B [C] D E F G H I J K L M N O P Q R S T U V W X Y Z   [Show ALL]
C
Crognale, MA, Levenson DH, Ponganis PJ, Deegan JF, Jacobs GH.  1998.  Cone spectral sensitivity in the harbor seal (Phoca vitulina) and implications for color vision. Canadian Journal of Zoology-Revue Canadienne De Zoologie. 76:2114-2118.   10.1139/cjz-76-11-2114   AbstractWebsite

The retinas of harbor seals (Phoca vitulina) contain two morphologically distinct photoreceptor types: rods and cones. The spectral properties of the cones have not been previously studied. The spectral sensitivities of the cones of harbor seals were measured using a retinal gross potential technique, flicker photometric electroretinography. We found a cone spectral sensitivity curve with a peak at about 510 nm. The shape of the spectral sensitivity curve remained invariant despite large changes in chromatic adaptation, implying that harbor seals have only a single cone photopigment. This means that harbor seals must lack color vision at photopic light levels. Any color discrimination in this species would have to be based on combined input from rods and cones and thus restricted to mesopic light levels. The spectral sensitivity of the cone pigment in the harbor seal is shifted to shorter wavelengths than those of terrestrial carnivores, consistent with adaptation to the aquatic photic environment.

Ponganis, PJ, Kooyman GL, h. Ridgway S.  2003.  Comparative Diving Physiology. Bennett and Elliott's physiology and medicine of diving. ( Brubakk AO, Neuman TS, Bennett PB, Elliott DH, Eds.).:16., Edinburgh; New York: Saunders Abstract
n/a
Ponganis, PJ.  2002.  Circulatory System. Encyclopedia of marine mammals. ( Perrin WF, W├╝rsig BG, Thewissen J, Eds.).:229-232., San Diego: Academic Press Abstract

This encyclopedia is a comprehensive, scientifically accurate work devoted to all aspects of marine mammals, including their anatomy, physiology, evolution, behavior, reproduction, ecology, and disease, as well as issues of exploitation, conservation, and management.

Kooyman, GL, Ponganis PJ.  2014.  Chick production at the largest emperor penguin colony decreases by 50% from 2008-10. Antarctic Science. 26:33-37.   10.1017/s0954102013000515   AbstractWebsite

The emperor penguin colony at Coulman Island is reputedly the largest known. This reputation is based on intermittent ground and aerial surveys performed since 1958. From an aerial survey obtained on 28 October 2010 we discovered that the total number of chicks was 56% of the lowest previous estimate of 2006 and only 41% of the most recent estimate in 2008. All of the counts tallied since 1983 were determined either by ground counts or from aerial film or digital photographs, or estimates from adult counts. We also determined the sea ice conditions in autumn, which is close to the time the adults arrive to breed. We present three hypotheses of what might have happened from 2008-10 to cause the step change in chick production, the small recovery of chick numbers in 2011, and the complete recovery of number of adults from 2010-11. We conclude that local circumstances may have strongly influenced the breeding behaviour of the emperor penguins in 2010 and to a lesser degree in 2011 when many adults elected not to breed.

Kooyman, GL, Ponganis PJ.  1997.  The challenges of diving to depth. American Scientist. 85:530-539. AbstractWebsite
n/a
Ponganis, PJ, Kooyman GL, Zornow MH.  1991.  Cardiac output in swimming California sea lions, Zalophus californianus. Physiological Zoology. 64:1296-1306. AbstractWebsite

Cardiac output was determined by the thermodilution technique in three California sea lions while resting and while swimming. Metabolic rates increased seven-to ninefold above resting rates during maximal exercise. While the sea lions were at rest, stroke volume was also determined by simultaneously counting heart rate during cardiac output determinations. At rest, cardiac output (2.5-3.0 mL kg-1s-1) and stroke volume (2 mL kg-1) were similar to those of harbor seals and terrestrial mammals of similar mass. During exercise, mean cardiac output increased linearly with work load and surface/submerged intervals were short and frequent. The exercise capacity of swimming sea lions appears similar to that of harbor seals, but the exercise response resembles that of terrestrial mammals more than that of harbor seals.

Ponganis, PJ, Kooyman GL, Zornow MH, Castellini MA, Croll DA.  1990.  Cardiac output and stroke volume in swimming harbor seals. Journal of Comparative Physiology B-Biochemical Systemic and Environmental Physiology. 160:473-482.   10.1007/BF00258974   AbstractWebsite

Cardiac output was measured by the thermodilution method in three young harbor seals, at rest and while swimming up to the maximum effort for which they could be trained. Stroke volume was determined by counting heart rate simultaneously with determination of cardiac output. Cardiac outputs varied widely between surface breathing (7.8 ml.kg-1.s-1) and breath-holding while swimming under water (1.8 ml.kg-1.s-1). Stroke volume while at the surface was almost twice the volume while submerged. Surface cardiac output was always near maximal despite work effort, whereas submerged cardiac output gradually increased at higher work efforts. The cardiovascular performance of seals at the maximum MO2 we could induce from them is equivalent to that of the domestic goat.

Ponganis, PJ, Stockard TK, Levenson DH, Berg L, Baranov EA.  2006.  Cardiac output and muscle blood flow during rest-associated apneas of elephant seals. Comparative Biochemistry and Physiology a-Molecular & Integrative Physiology. 144:105-111.   10.1016/j.cbpa.2006.02.009   AbstractWebsite

In order to evaluate hemodynamics and blood flow during rest-associated apnea in young elephant seals (Mirounga angustirostris), cardiac outputs (CO, thermodilution), heart rates (HR), and muscle blood flow (MBF, laser Doppler flowmetry) were measured.. Mean apneic COs and HRs of three seals were 46% and 39% less than eupneic values, respectively (2.1 +/- 0.3 vs. 4.0 +/- 0.1 mL kg(-1) s(-1), and 54 6 vs. 89 14 beats min(-1)). The mean apneic stroke volume (SV) was not significantly different from the eupneic value (2.3 +/- 0.2 vs. 2.7 +/- 0.5 mL kg(-1)). Mean apneic MBF of three seals was 51% of the eupneic value. The decline in MBF during apnea was gradual, and variable in both rate and magnitude. In contrast to values previously documented in seals during forced submersions (FS), CO and SV during rest-associated apneas were maintained at levels characteristic of previously published values in similarly-sized terrestrial mammals at rest. Apneic COs of such magnitude and incomplete muscle ischemia during the apnea suggest that (1) most organs are not ischemic during rest-associated apneas, (2) the blood O-2 depletion rate is greater during rest-associated apneas than during FS, and (3) the blood O-2 store is not completely isolated from muscle during rest-associated apneas. (c) 2006 Elsevier Inc. All rights reserved.