QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online March 14, 2008
Journal of Experimental Biology 211, 1141-1147 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.015339

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Uriona, T. J. Articles by Farmer, C. G. Search for Related Content PubMed PubMed Citation Articles by Uriona, T. J. Articles by Farmer, C. G. Social Bookmarking                         What's this?

Recruitment of the diaphragmaticus, ischiopubis and other respiratory muscles to control pitch and roll in the American alligator (Alligator mississippiensis)

T. J. Uriona and C. G. Farmer

Department of Biology, 257 South 1400 East, University of Utah, Salt Lake City, UT 84112, USA

View larger version (40K): [in this window] [in a new window]   Fig. 1. (A) Illustration of some of the major anatomical features associated with ventilation in crocodilians. Expiration is produced by caudal rotation of the ribs through contraction of the internal intercostals and constriction of the abdominal cavity, which produces a cranial translation of the viscera. Constriction of the abdomen results from activity of the transversus abdominis muscle and the rectus abdominis muscle, which rotate the pubes and gastralia dorsally. Inspiration is produced by cranial rotation of the ribs and caudal translation of the viscera. The viscera, including the large stomach, are pulled caudad by contraction of the diaphragmaticus muscle. The ischiopubis muscles increase the abdominal volume by rotating the pubes and gastralia ventrally. [Diagrams modified with permission from Farmer and Carrier (Farmer and Carrier, 2000a).] (B) X-ray picture illustrating the degree to which the lung is displaced during an inspiration [modified with permission from Brainerd (Brainerd, 1999)].

View larger version (13K): [in this window] [in a new window]   Fig. 2. Sample recordings from alligator 2 (body mass 1.22 kg) of change in pitch (top trace) associated with EMG activity (second trace) in the diaphragmaticus during ventilation and during a dive. The V below the EMG trace indicates muscle activity in the diaphragmaticus associated with inspiration. During this time the alligator's head was level with the water and its body was at a positive 45° angle as illustrated by the schematic alligator above the left side of the pitch angle trace. It should be noted that during this particular ventilation cycle very little change in the pitch angle can be seen. The D below the EMG trace indicates muscle activity in the diaphragmaticus associated with a dive. The vertical bars that mark the beginning of a dive and the subsequent return to the original pitch angle after surfacing from the dive delimit a dive–surface cycle. The maximum pitch angel for this dive–surface cycle was reached at around –45° when the alligator's head was parallel to the surface of the water and its body assumed the indicated angle as illustrated by the schematic (upper right side of the inclinometer trace). In order to compare muscle activity over the course of a dive–surface cycle of different lengths, the cycle was divided into 100 equal bins and the average integrated muscle activity for each bin calculated. A sample of how this was done for a cycle is shown below the EMG trace in this figure. The calibration bar, 1 s.

View larger version (19K): [in this window] [in a new window]   Fig. 3. Graphs of timing and intensity of muscle activity during a dive–surface cycle with the relative muscle activity of each muscle divided into 100 bins and expressed as means ± s.e.m. for each bin. (A) Diaphragmaticus, N=7; (B) ischiopubis; N=4; (C) rectus abdominis, N=4; (D) internal intercostals, N=2.

View larger version (13K): [in this window] [in a new window]   Fig. 4. Graphs of the integrated EMG activity divided by change in pitch (mean ± s.e.m.) in the diaphragmaticus, ischiopubis and rectus abdominis muscles for each alligator during a dive under three conditions; with no weight added to the animal (gray bars), with weight equaling 2.5% of the animal's body mass under the jaw (white bars), and with weight equaling 2.5% of the animal's body mass on the base of the tail (black bars). Numbers 1–5 indicate the alligator that was used, followed by a L or R, which indicates if the muscle on the left or right side, respectively, was used; * significant treatment effect when comparing head weighted to tail weighted dives (P0.05); significant treatment effect when comparing dives where no weighted was added to tail weighted dives (P0.05). The values for integrated EMG activity divided by the change in pitch should not be compared between animals or muscles because of differences in electrodes, placement of electrodes, and individual muscle activity.

View larger version (18K): [in this window] [in a new window]   Fig. 5. Sample data for two alligators showing timing and intensity of muscle activity as the average integrated EMG activity divided into 100 bins during a dive where the animals rolled hard to the right side (clockwise) and to the left side (counterclockwise). The shaded area in the middle of the graphs represents the period of time during the dive where the animals rolled to the right or the left side respectively. An equal period prior to and following the period of time associated with the roll is shown on either end of the graphs. The first set of graphs shows muscle activity in the right rectus abdominis of alligator 2. The second set of graphs shows muscle activity in the right diaphragmaticus of alligator 5. The third set of graphs shows muscle activity in the left diaphragmaticus of alligator 5. The final set of graphs shows muscle activity in the left diaphragmaticus of alligator 2. For both animals muscle activity can be seen to diminish or stop in left diaphragmaticus during the period of time that the animal was rolling to the right and the opposite is seen as the animal rolls to the left. The same trend can be seen in the right rectus abdominis in alligator 2 and the right diaphragmaticus in alligator 5. At around 66% of the entire cycle the animal is no longer diving down and muscle activity stops for all the muscles shown in both alligators.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

Twitter