Lamprey Feeding & Respiration

Cross references:     Amphioxus Feeding & Respiration     Lamprey  

Searching PubMed for "Lamprey Feeding & Respiration" revealed 3 references :   

Feeding and breathing in lampreys. - PubMed       
Central pattern generators for respiration are distributed in the medulla, particularly lateral to Vm, and drive branchial motoneurons in VIIm-IXm-Xm. Trigeminal pattern generators in lampreys may be a holdover from the ammocoete stage, in which they drive nearby velar motoneurons as the primary pump for ventilation. Respiration in lampreys and ammocoetes is stimulated by hypoxia and modulated by reflexes. Metamorphosis from ammocoete to adult lamprey involves extensive remodeling of the head with regression and replacement of most muscles. Trigeminal motoneurons are probably preserved during metamorphosis, as inferred from constant maps of motoneurons in Vm. This hypothesis is supported by analogy with anuran metamorphosis in which V motoneurons are retained and remodeled. In Mallatt's current models, the earliest vertebrates breathed by branchial contractions and valves; jaws initially evolved for better ventilation and later were used for feeding."  

Respiration of Lampreys - Canadian Journal of Fisheries and Aquatic Sciences   
In lampreys, though the gross morphology of the branchial chamber and the method of ventilating the gills are radically different from that found in gnathostomes, the total gill area of larval (1462–2717 mm2∙g−1) and adult (1402–2337 mm2∙g−1) lampreys, the ultrastructure of the gills, and the thickness of the water–blood barrier are similar to active teleosts.  
    The standard rates of oxygen consumption of ammocoetes are low, values for medium-sized Ichthyomyzon hubbsi ranging from 18.1 μL∙g−1∙h−1 at 3.5 °C to 90.1 μL∙g−1∙h−1 at 22.5 °C. The consumption rates increase during metamorphosis rising in Lampetra fluviatilis held at 10 °C from 29.3 to 60.4 μL∙g−1∙h−1, and at the same time a circadian rhythm of consumption develops; maximum rates occur in the dark.  
    Adult lampreys have consumption rates ranging from 66.1 μL∙g−1∙h−1 in L. fluviatilis to 36.9 μL∙g−1∙h−1 in Petromyzon marinus, and Q10's in the temperature range 5–15 °C are from 1.6 to 4.83. Sexually mature males of L. planeri and L. fluviatilis have higher metabolic rates than the females. The active oxygen consumption of P. marinus at 332.5 μL∙g−1∙h−1 is within the range reported for teleosts. Resting ventilation rates are higher in adults than ammocoetes and reach maximum values in sexually mature spawning males. 
     Hypoxia results in an increase in the ventilation and heart rates.Key words: lampreys, respiration; gills, morphology; oxygen consumption, sexual maturity, ventilation rates"  

Lamprey - The Canadian Encyclopedia   
Brief, well written article available online for free. 
For respiration and feeding, water enters the mouth and is extruded through the gill openings. ... In adults, water for respiration enters and exits only through the gill openings."  
    My comment
This reference accepts the idea that lamprey respiration is through the gills. 

2014    Free PMC Article   
Lamprey breathing when feeding sucks: the respiratory rhythm generator of a parasitic fish. - PubMed  
    Note:  To read the article, click on the link, above, and then click on  Free PMC Article again. 
or click:
Unlike most fish, which use a buccal pump to gill ventilate, adult lampreys use muscles associated with their gill slits. Constriction of these muscles causes water expulsion; water inhalation is by passive recoil. This arrangement frees their buccal musculature for parasitic feeding; they can suck, feed and breathe all at the same time (Rovainen, 1996). The rhythmic contractions associated with ventilation are controlled by rhythmic bursts of branchial motor neurons (VIIm–IXm–Xm) that persist with high fidelity when the brainstem is isolated (Kawasaki, 1979). Two brainstem sites have been associated with rhythm generation, an area around the trigeminal motor nucleus (i.e. the paratrigeminal respiratory group; pTRG) and the vagal motor neuron region (VMR)."
Firstly, confirmation that the pTRG is necessary and sufficient for rhythm generation allows us to add lamprey to a growing list of vertebrates in which discrete respiratory rhythm generating sites (oscillators) have been identified, including frogs, chicks, rats, mice and goats. Secondly, this architecture is very different to that proposed for gill rhythm generator in other fish (a discrete oscillator for gill ventilation has yet to be located in any other kind of fish, with the most recent data from elasmobranch and teleosts suggesting rhythm generation is distributed along the length of the brainstem; Duchcherer et al. 2010; Taylor et al. 2010). Thirdly, the pTRG is the first confirmed vertebrate respiratory oscillator located in the pons; in all other vertebrates, respiratory oscillators appear to be confined to the medulla (evidence for a pontine oscillator in rat and carp is anecdotal; see Wilson et al. 2006)."    
    My comment
The location of the respiratory generator does not seem to be constant among different species. 

Searching Google for "Lamprey Feeding & Respiration" revealed 53,400 references:   

Full text of "The Breathing and Feeding Mechanism of the Lampreys. II" THE BREATHING AND FEEDING MECHANISM OF THE LAMPREYS. II. ( Concluded. ) JEAN DAWSON.
CONTENTS. II. Food and Mechanism of Feeding 91 A. Mode of Attachment 91 B. Mode of Feeding of Attached Lampreys 94 C. Character of Food 94 III. Mechanism of Respiration 96 A. When the Lamprey is Attached 96 B. When the Animal is not Attached 99 C. Detachment and Regurgitation 101 D. Velar Jaws 105 IV. Summary 106 V. References m II. Food and Mechanism of Feeding.

    also, 2 PDFs: 
The Breathing and Feeding Mechanism of the Lampreys. II
The Breathing and Feeding Mechanism of the Lampreys. II - 1535761.pdf   
Note:  This is a very informative, 22-page PDF.   It's worth reading if you have the time, but it's old enough that it doesn't have anything to say about physiology.   

For a contrary view, see: 
    mbbiology - Lamprey   
Circulatory/Respiratory Systems Blood flows through a series of vessels to supply oxygen and nutrients to the body and to remove carbon dioxide and other wastes. Arteries and arterioles carry blood away from the heartVeins and venules carry blood back towards the heartCapillaries are the smallest vessels where the gases are exchanged with the cells of the body A lamprey “breathes” by extracting the oxygen present in the water in which it livesWater: mouth →pharynx → respiratory tube Within the respiratory tube are seven gill pouches, each containing the finer feather-like gill lamellae. The gill lamellae increase the surface area of the respiratory structures and contain the small capillary beds that extract oxygen.