Gill morphometry of the facultative air-breathing loricariid fish,Hypostomus plecostomus (Walbaum) with, special emphasis on aquatic respiration

In response to progressive aquatic hypoxia, the armoured loricariid catfishes Ancistrus chagresi and Hypostomus plecostomus become facultative air-breathers and utilize their stomachs as accessory air-breathing organs. Hypostomus initiates air breathing at a higher aquatic O2 tension (Pw, Ow, O2) than does Ancistrus (60 v. 33 mmHg). Once begun, the air-breathing frequencies of both species increase with decreasing Pw, Ow, O2; the frequency of Ancistrus, however, is greater than and increases more with hypoxia than does that of Hypostomus, which appears to be a more efficient air breather. Hypoxia acclimation reduces the air-breathing rate of both species. A larger rate reduction occurs in Ancistrus, which, however, continues to require more frequent breaths than Hypostomus. Hypoxia acclimation does not affect the air-breathing threshold of either species, suggesting that external O2 receptors initiate facultative air breathing. In progressive aquatic hypercapnia Ancistrus has a lower air-breathing CO2 threshold (8.7 mmHg) than Hypostomus (12.8 mmHg). However, in some tests, individual fish of both species did not initiate air breathing even at Pw, COw, CO2 as high as 21 mmHg. Also, air breathing evoked by hypercapnia was short-lived; both species quickly compensated for this gas and resumed exclusively aquatic respiration within a few hours of exposure. Thus, CO2 is not an important regulator of air breathing in these species. Between 25 and 35 °C, the Pw, Ow, O2 air breathing threshold of Ancistrus is temperature-independent, but air-breathing frequency increases with temperature. Ancistrus and Hypostomus do not breathe air in normoxic (air-saturated) water; their air-breathing responses are evoked by environmental hypoxia. This is fundamentally different from other fish species that breathe air in normoxia in order to meet heightened metabolic demands. Also, the facultative air-breathing adaptations of Ancistrus and Hypostomus differ in scope and magnitude from those utilized by species that breathe air in nor-moxia and adapt to hypoxia by increasing air-breathing rate.

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The Transition to Air Breathing in Fishes: III. Effects of Body Size and Aquatic Hypoxia on the Aerial Gas Exchange of the Swamp Eel Synbranchus Marmoratus

Journal of Experimental Biology ◽

10.1242/jeb.108.1.357 ◽

1984 ◽

Vol 108 (1) ◽

pp. 357-375 ◽

Cited By ~ 1

Author(s):

JEFFREY B. GRAHAM ◽

TROY A. BAIRD

Keyword(s):

South American ◽

Air Breathing ◽

Aquatic Respiration ◽

Environmental Selection ◽

Blood Haemoglobin ◽

Hypoxic Water ◽

Breath Co2 ◽

Hb Concentration ◽

Swamp Eel ◽

Exchange Surface

Synbranchus marmoratus (Bloch) breathes air during terrestrial excursions and while dwelling in hypoxic water and utilizes its gills and adjacent buccopharyngeal epithelium as an air-breathing organ (ABO). This fish uses gills and skin for aquatic respiration in normoxic (air-saturated) water but when exposed to progressive aquatic hypoxia it becomes a metabolic O2 conformer until facultative air breathing is initiated. The threshold PwOO2 (aquatic O2 tension or partial pressure in mmHg) that elicits air breathing in S. marmoratus is higher in larger fish. However, neither air-breathing threshold nor the blood haemoglobin (Hb) concentration of this species were changed following hypoxia (PwOO2 < 20 mmHg) acclimation. In hypoxic water S. marmoratus supplies all of its metabolic O2 requirement through air breathing. ABO volume scales with body weight raised to the power of 0.737 and the amount of O2 that is removed from each air breath depends upon the length of time it is held in the ABO. Ambient PwOO2 directly affects the air-breath duration of this fish, but the effect is smaller than in other species. Also, average air-breath duration (15.7 min at PwOO2 0–20 mmHg) and the average inter-air-breath interval (15.1 min) of S. marmoratus are both longer than those of other air-breathing fishes. Although the gills of S. marmoratus are involved in aerial O2 uptake, expelled air-breath CO2 levels are not high and always closely correspond to ambient PwCOCO2, indicating that virtually no respiratory CO2 is released to air by this fish. CO2 extrusion therefore must occur aquatically either continuously across another exchange surface or intermittently across the gills during intervals between air breaths. This study with S. marmoratus from Panama reveals physiological differences between this population and populations in South America. The greater Hb content of South American S. marmoratus may be the result of different environmental selection pressures.

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Gill morphology and morphometry of the facultative air‐breathing armoured catfish, Corydoras paleatus , in relation on aquatic respiration

Journal of Fish Biology ◽

10.1111/jfb.14837 ◽

2021 ◽

Author(s):

S.E. Plaul ◽

A. O. Díaz ◽

C.G. Barbeito

Keyword(s):

Air Breathing ◽

Aquatic Respiration ◽

Gill Morphology ◽

Morphology And Morphometry ◽

Armoured Catfish

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Respiratory faculties of aquatic invertebrates

Respiratory Biology of Animals ◽

10.1093/oso/9780199238460.003.0006 ◽

2019 ◽

pp. 65-83

Author(s):

Steven F. Perry ◽

Markus Lambertz ◽

Anke Schmitz

Keyword(s):

Aquatic Invertebrates ◽

Air Breathing ◽

Aquatic Respiration

This chapter introduces the ‘who has what’ in terms of respiratory organs for major water-breathing invertebrate groups. It begins with sponges and cnidarians—groups that have no recognizable respiratory faculty—and continues through the bilaterian lineage, pointing out how bits and pieces of a respiratory faculty accumulate. The most complex respiratory faculties are found in molluscs and arthropods, which consequently make up the bulk of this chapter. Aside from the ancestral aquatic respiration, this chapter furthermore explains how also within some terrestrial (air-breathing) groups such as arachnids and insects, mechanisms that allow lone—even permanent—stays under water have secondarily arisen.

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The transition to air breathing in fishes. V. Comparative aspects of cardiorespiratory regulation in Synbranchus marmoratus and Monopterus albus (Synbranchidae)

Journal of Experimental Biology ◽

10.1242/jeb.198.7.1455 ◽

1995 ◽

Vol 198 (7) ◽

pp. 1455-1467 ◽

Cited By ~ 1

Author(s):

J Graham ◽

N Lai ◽

D Chiller ◽

J Roberts

Keyword(s):

Heart Rate ◽

Respiratory System ◽

Chronotropic Effect ◽

Cardiac Innervation ◽

Sinus Arrhythmia ◽

Air Breathing ◽

Monopterus Albus ◽

Factors Affecting ◽

Aquatic Respiration ◽

Primitive Species

Extreme heart-rate lability accompanies the air-breathing cycles of Synbranchus marmoratus and Monopterus albus. When air is taken into the buccopharyngeal air-breathing organ of these fishes, heart rate increases sharply above pre-inspiration rates of 325 beats min-1 to as high as 4045 beats min-1. With time, and as O2 is depleted from the air-breathing organ, heart rate gradually declines and drops to its lowest level with, or following, exhalation. Relationships between air breathing and sinus arrhythmia in M. albus were investigated by injecting variable gas volumes and O2 mixtures into the cannulated air-breathing organ. Tests were also carried out on undisturbed fish breathing volitionally in atmospheres containing different O2 levels. Both the volume and O2 content of the inspired gas affect the level and duration of inspiration tachycardia. Additional factors affecting tachycardia are the heart rate prior to inspiration and the time since air was last held. S. marmoratus is a non-obligatory air breather and uses rhythmic branchial aquatic respiration to a greater extent than M. albus, an obligate air breather. While the heart rates of both species are increased during aquatic ventilation, the higher heart rate to ventilation ratio in S. marmoratus (23 versus approximately 1 in M. albus) seems attributable to its more proficient aquatic respiratory system. The available cardiorespiratory data for air-breathing fishes indicate that the scope of air-inspiration tachycardia is smaller in lungfishes and other primitive species than in most teleosts. This difference is mainly attributable to the greater chronotropic effect of sympathetic cardiac innervation in teleosts.

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Respiratory and hydrostatic functions of the intestine of the catfishes Hoplosternum thoracatum and Brochis splendens (Callichthyidae)

Journal of Experimental Biology ◽

10.1242/jeb.74.1.1a ◽

1978 ◽

Vol 74 (1) ◽

pp. 1-16 ◽

Cited By ~ 2

Author(s):

J. H. Gee ◽

J. B. Graham

Keyword(s):

Gas Phase ◽

Respiratory Organ ◽

Neutral Buoyancy ◽

Similar Frequency ◽

Air Breathing ◽

Aquatic Respiration ◽

Metabolic Scope ◽

Hypoxic Water ◽

The Mean ◽

Increased Activity

1. The air-breathing behaviour of Hoplosternum thoracatum and Brochis splendens has been studied and their strategy of coordinating the respiratory and hydrostatic functions of the accessory respiratory organ has been examined. 2. H. thoracatum and B. splendens are continuous but not obligate air-breathers and individuals of the former breathe air in synchrony with each other. 3. Frequency of air-breathing increased with increased activity in H. thoracatum. 4. Aquatic respiration (Vo2) in H. thoracatum decreased in hypoxic water but aerial Vo2 maintained a fairly constant total Vo2 independent of aquatic O2. Total Vo2 is higher when fish breathe both air and water but aerial Vo2 did not exceed 75% of total Vo2. 5. The accessory respiratory organ provides about 75% of the lift required to attain neutral buoyancy whereas the swimbladder provides less than 5%. The mean decreases in volume of the accessory respiratory organ in the period between breaths of B. splendens and H. thoracatum were 13.2 and 7.8% respectively. 6. With a gas phase of O2, B. splendens maintained a similar frequency of air breathing and showed a slightly greater reduction in buoyancy between air breaths when compared to breathing air. With a gas phase of N2, air breathing was less frequent and decreases in buoyancy between air breaths were much less than when breathing air. 7. The respiratory and hydrostatic functions of the accessory respiratory organ are compatible. Buoyancy is maintained by frequent air breaths taken in part in response to a decrease in volume of the accessory respiratory organ. This reservoir of O2 could increase metabolic scope during bursts of activity.

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Respiration in an Air-Breathing Fish, the Climbing Perch, Anabas Testudineus

Journal of Experimental Biology ◽

10.1242/jeb.53.2.281 ◽

1970 ◽

Vol 53 (2) ◽

pp. 281-298

Author(s):

G. M. HUGHES ◽

B. N. SINGH

Keyword(s):

Tap Water ◽

Time Interval ◽

Water Control ◽

Pure Nitrogen ◽

Anabas Testudineus ◽

Air Breathing ◽

High Co2 ◽

Climbing Perch ◽

Aquatic Respiration ◽

Made In

1. A study has been made of the patterns of respiration in climbing perch (Anabas testudineus) living in water containing different concentrations of oxygen and carbon dioxide and also in air-exposed fish. 2. The fish breathes both water and air in normal tap water. The intervals between air-breaths are irregular and vary within the range 8-15 min. 3. Air-breathing increases in water of high CO2 content. The time interval between air breaths falls with increasing CO2 content. Gill ventilatory frequency increases when 5-10% CO2 is bubbled into the water. Aquatic respiration stops and only aerial respiration occurs if more than 20% CO2 is bubbled into the water. 4. Three factors, CO2 content, pH and O2 content of water, control the respiratory patterns in climbing perch. Of these CO2 content appears to be most important for fish living in water. 5. The climbing perch can live for long periods (6-12 h during observations made) in water of very high CO2 content (20-33 vols. %). In such hypercarbic water gases are only exchanged through the air-breathing organs. The mouth and opercula are closed tightly and gill ventilation stops completely. 6. Exposure to air increases air-breathing but the frequencies are irregular. Inhalation of hypoxic gas or pure nitrogen also evokes air-breathing.

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