POSTER - A New, Non-Lethal Phenotype, the Blackburn College Floater (BC-Floater), in the Axolotl (Ambystoma mexicanum) (original) (raw)
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The swimbladder is a well-known adaptation with which many fish species create upward hydrodynamic forces to prevent them from sinking. Development and survival rates are adversely affected by deflated swimbladders. Based on morphology, an open swimbladder system (physostomous) and a closed swimbladder system (physoclistous) are distinguished. In this study two physostomous species, zebrafish (Danio rerio) and goldfish (Carassius auratus), and two physoclistous species, tilapia (hybrid of Oreochromis mossambicus and Oreochromis niloticus ) and the cichlid (Haplochromis piceatus) were exposed to severe chronic hypoxia. The zebrafish showed reduced buoyancy. X-ray pictures and MRI scans showed that all individuals exposed to severe hypoxia suffered from deflated swimbladders after three weeks. To maintain their position in the water column under hypoxic conditions, zebrafish redirect their swimming movements and swim at an angle of around 45 degrees, which ultimately leads to the development of lordosis. The other three tested species were able to keep their swimbladders inflated and maintained their buoyancy. As a result, none of them changed their swimming movements or developed lordosis. Our results demonstrate that coping with low oxygen levels is done in a species specific manner and that severe chronic hypoxia effects zebrafish on the long term.
Lung Mechanics in Marine Mammals
The long term goal of this study is to develop methods to study lung physiology in live marine mammals and to use these techniques to investigate the mechanical properties of the respiratory system in different marine mammals. This effort is vital to understand how diving mammals manage inert and metabolic gases during diving and will help determine what behavioral and physiological responses increase DCS risk. OBJECTIVES Recent theoretical studies have suggested that marine mammals commonly live with elevated blood and tissue N 2 levels, and that they use both physiological and behavioral means to avoid DCS [1, 2]. But what physiological variables are the most important to reduce N 2 levels below those that cause DCS, and how important is a link between behavior and physiology? For example, if the duration of each individual dive was extended, the repeated dives during a bout (a series of repeated dives with a short intervening surface interval) may result in accumulation N 2 to levels that may cause DCS. A variety of situations, such as sonar exposure, reduction in prey abundance or environmental change, may result in behavioral changes in dive pattern. Such changes could cause elevated tissue and blood N 2 levels that either result in DCS or force the animal to end a foraging bout prematurely to prevent the formation of inert gas bubbles. Prematurely ending a diving bout reduces foraging efficiency and could have detrimental implications for survival. While the results from theoretical studies have to be viewed with caution, sensitivity analyses have indicated that the degree of gas exchange and cardiac output
Journal of Comparative Physiology ? B, 1975
Aquatic turtles utilize changes in lung volume in their buoyancy regulation. The relationship between lung volume and ventilatory activity have been studied in the turtle, Carstta caretta. Lung volume was varied in response to specific gravity changes brought about by adding weights or floats to the animals. End inspiratory lung volumes were made to vary from 4.4 to 8.1 ml/100 g body weight. These lung volume changes maintained specific gravity relatively constant. An inverse linear relationship exists between lung volume and frequency of respiration.
Respiratory Function in the South American Lungfish, Lepidosiren Paradoxa (Fitz)
Journal of Experimental Biology, 1967
Few animal species have aroused as much excitement upon their discovery as the South American lungfish. Its possession of distinct piscine as well as amphibian characters made the animal a link in the transition of vertebrate life from water breathing to air breathing. Its special attributes are clearly reflected in its name,
Homeostasis in the Aquatic Environment
HO~.rEOSTA.\;)IS IN THE AQUATlC ENVIDONJVIENT N /1arille manllnals have made lllallY interesting and ilnporlant ~ physiulogi 'al adjllslmcllts in albplillg t() aqllali ' life. IUlllc roll S analomical va riations r li e 'l clJanges that 11av(' oc 'lilT dill Jl1atnlllali[ln res piralory fUlIclioLl, UICJ"lIIUrcglllatioll, circulatioll, remll physiology. and JlcuralmechaJlisIIls. There i.' it strikillg degre · of illl grat-i(Jll in Lh e ph .jo-I(l"ical mo lincatiulls that marine mammals lwv ' achi .v d. DifieJ"f'ut species O(t Oll have Llchiev ~d th ". c adjust ments in dive 'so \.va 'S d P lleling lIpon Ul e sp 'ciIic ological delll<lllcis made "pOll t"1H'III. All of tltes -, spc.:ciali7. d aquatic.: ada )tatiulls lllllst lIe cUllsid e re d h~' an yone \\ 110 wish e -' to work w iLli tld. s . gw,,1,l of 1I1<lllllllals . Homeos tatic II1 t.: ('II:lllisIIIS lIlust IJavt. Cll llsid -ration jll til ' clillical lllQll:l eJ1Jellt of tlt(' \"a.riulls aqllatic spc 'ie ·. As Hobin (IUG() poinLs (Jut-, "comparative physiulogy 0 11 the; Oll(' hand and cLinicf)1 nl edicill 011 th' otii r C()Jl s lillllt-' a hl"ll;HI ["'IJ -w a y str ' d. Each discipliuf' is capabl e uF lllakiug illlportant cO lltrilJlIliollS t() th e Illlier hecalls " there is a basic Ililily <lIlIOllg living forrns." Tfollleos/((sis in tIle Af]1I1rlic FII/ :il'Onment '.
Hypoxia tolerance of the mummichog: the role of access to the water surface
Journal of Fish Biology, 2003
Low dissolved oxygen (DO) had a significant effect on specific growth rate (G S ), length increment (I L ) and haematocrit (Hct) of the mummichog Fundulus heteroclitus. Regardless of access to the water surface, F. heteroclitus maintained high growth rates (G S and I L ) at DO concentrations as low as 3 mg O 2 l À1 . With access to the water surface, both G S and I L of F. heteroclitus decreased by c. 60% at 1Á0 mg O 2 l À1 compared to all higher DO treatments. When denied access to the water surface, a further decrease in G S (c. 90%) and I L (c. 75%) was observed at 1 mg O 2 l À1 . There was no effect of diel-cycling DO (1-11 mg O 2 l À1 ) with or without surface access on G S , I L or Hct of F. heteroclitus. Similar trends between G S and faecal production across DO treatments suggest that decreased feeding contributed significantly to the observed decrease in growth rate. Haematocrit was significantly elevated at 1 mg O 2 l À1 for fish with and without access to the water surface. Increased Hct, however, was not sufficient to maintain high G S or I L at severely low DO. When permitted to respire in the surface layer, however, F. heteroclitus was capable of maintaining moderate growth rates at DO concentrations of 1 mg O 2 l À1 (c. 15% saturation). Although aquatic surface respiration (ASR) was not quantified in this study, F. heteroclitus routinely swam in contact with the water surface and performed ASR at DO concentrations 3 mg O 2 l À1 . No hypoxia-related mortality was observed in any DO or surface access treatment for as long as 9 days. This study demonstrates that surface access, and thus potential for ASR, plays an important role in providing F. heteroclitus substantial independence of growth rate over a wide range of low DO conditions commonly encountered in shallow estuarine environments. #
Hydrostatic lung compression in diving marine mammals, with collapsing alveoli blocking gas exchange at depth, has been the main theoretical basis for limiting N 2 uptake and avoiding gas emboli (GE) as they ascend. However, studies of beached and bycaught cetaceans and sea turtles imply that air-breathing marine vertebrates may, under unusual circumstances, develop GE that result in decompression sickness (DCS) symptoms. Theoretical modelling of tissue and blood gas dynamics of breath-hold divers suggests that changes in perfusion and blood flow distribution may also play a significant role. The results from the modelling work suggest that our current understanding of diving physiology in many species is poor, as the models predict blood and tissue N 2 levels that would result in severe DCS symptoms (chokes, paralysis and death) in a large fraction of natural dive profiles. In this review, we combine published results from marine mammals and turtles to propose alternative mechanisms for how marine vertebrates control gas exchange in the lung, through management of the pulmonary distribution of alveolar ventilation (_ V A) and cardiac output/lung perfusion (_ Q), varying the level of _ V A = _ Q in different regions of the lung. Man-made disturbances, causing stress, could alter the _ V A = _ Q mismatch level in the lung, resulting in an abnormally elevated uptake of N 2 , increasing the risk for GE. Our hypothesis provides avenues for new areas of research, offers an explanation for how sonar exposure may alter physiology causing GE and provides a new mechanism for how air-breathing marine vertebrates usually avoid the diving-related problems observed in human divers.