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Lung anatomy and histology of the extant coelacanth shed light on the loss of air-breathing during deep-water adaptation in actinistians

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ABSTRACT

Lungs are specialized organs originated from the posterior pharyngeal cavity and considered as plesiomorphic for osteichthyans, as they are found in extant basal actinopterygians (i.e. Polypterus) and in all major groups of extant sarcopterygians. The presence of a vestigial lung in adult stages of the extant coelacanth Latimeria chalumnae is the result of allometric growth during ontogeny, in relation with long-time adaptation to deep water. Here, we present the first detailed histological and anatomical description of the lung of Latimeria chalumnae, providing new insights into its arrested differentiation in an air-breathing complex, mainly represented by the absence of pneumocytes and of compartmentalization in the latest ontogenetic stages.

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Histological thin sections of the anterior part of the vestigial lung, from adult specimen CCC 5. Oesophagus at the top left (asterisks indicate the lumen) and lung in the bottom right (numbered asterisks localize the lumen relative to the lung in figure 1b,c). (a) Vestigial lung at the level of its origin (asterisk 2 of figure 1) with disorganized muscle bundles (brackets) surrounding this organ. (b,c) Anterior portion (two successive sections) of the lung still in close proximity with the oesophagus, showing invaginations in the lung walls (asterisk 2 of figure 1). Muscle bundles distributed in an organized network (brackets). (d) Vestigial lung completely dissociated from the oesophagus (asterisk 3 of figure 1), presenting the clearly reduced invaginations of the lung walls. Arrowheads indicating the hard, but flexible, plates. Scales bar 0.1 cm (a–d). (a,b,d, azocarmin; c, cajal colorations).
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RSOS161030F2: Histological thin sections of the anterior part of the vestigial lung, from adult specimen CCC 5. Oesophagus at the top left (asterisks indicate the lumen) and lung in the bottom right (numbered asterisks localize the lumen relative to the lung in figure 1b,c). (a) Vestigial lung at the level of its origin (asterisk 2 of figure 1) with disorganized muscle bundles (brackets) surrounding this organ. (b,c) Anterior portion (two successive sections) of the lung still in close proximity with the oesophagus, showing invaginations in the lung walls (asterisk 2 of figure 1). Muscle bundles distributed in an organized network (brackets). (d) Vestigial lung completely dissociated from the oesophagus (asterisk 3 of figure 1), presenting the clearly reduced invaginations of the lung walls. Arrowheads indicating the hard, but flexible, plates. Scales bar 0.1 cm (a–d). (a,b,d, azocarmin; c, cajal colorations).

Mentions: Here, we describe the general morphology through partial dissections (figure 1), three-dimensional reconstructions (figure 1), histology (figures 2–4) and virtual thin-sections of long-propagation phase-contrast synchrotron X-ray microtomography (figure 4) of the lung of various developmental stages of the extant coelacanth L. chalumnae.Figure 1.


Lung anatomy and histology of the extant coelacanth shed light on the loss of air-breathing during deep-water adaptation in actinistians
Histological thin sections of the anterior part of the vestigial lung, from adult specimen CCC 5. Oesophagus at the top left (asterisks indicate the lumen) and lung in the bottom right (numbered asterisks localize the lumen relative to the lung in figure 1b,c). (a) Vestigial lung at the level of its origin (asterisk 2 of figure 1) with disorganized muscle bundles (brackets) surrounding this organ. (b,c) Anterior portion (two successive sections) of the lung still in close proximity with the oesophagus, showing invaginations in the lung walls (asterisk 2 of figure 1). Muscle bundles distributed in an organized network (brackets). (d) Vestigial lung completely dissociated from the oesophagus (asterisk 3 of figure 1), presenting the clearly reduced invaginations of the lung walls. Arrowheads indicating the hard, but flexible, plates. Scales bar 0.1 cm (a–d). (a,b,d, azocarmin; c, cajal colorations).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383850&req=5

RSOS161030F2: Histological thin sections of the anterior part of the vestigial lung, from adult specimen CCC 5. Oesophagus at the top left (asterisks indicate the lumen) and lung in the bottom right (numbered asterisks localize the lumen relative to the lung in figure 1b,c). (a) Vestigial lung at the level of its origin (asterisk 2 of figure 1) with disorganized muscle bundles (brackets) surrounding this organ. (b,c) Anterior portion (two successive sections) of the lung still in close proximity with the oesophagus, showing invaginations in the lung walls (asterisk 2 of figure 1). Muscle bundles distributed in an organized network (brackets). (d) Vestigial lung completely dissociated from the oesophagus (asterisk 3 of figure 1), presenting the clearly reduced invaginations of the lung walls. Arrowheads indicating the hard, but flexible, plates. Scales bar 0.1 cm (a–d). (a,b,d, azocarmin; c, cajal colorations).
Mentions: Here, we describe the general morphology through partial dissections (figure 1), three-dimensional reconstructions (figure 1), histology (figures 2–4) and virtual thin-sections of long-propagation phase-contrast synchrotron X-ray microtomography (figure 4) of the lung of various developmental stages of the extant coelacanth L. chalumnae.Figure 1.

View Article: PubMed Central - PubMed

ABSTRACT

Lungs are specialized organs originated from the posterior pharyngeal cavity and considered as plesiomorphic for osteichthyans, as they are found in extant basal actinopterygians (i.e. Polypterus) and in all major groups of extant sarcopterygians. The presence of a vestigial lung in adult stages of the extant coelacanth Latimeria chalumnae is the result of allometric growth during ontogeny, in relation with long-time adaptation to deep water. Here, we present the first detailed histological and anatomical description of the lung of Latimeria chalumnae, providing new insights into its arrested differentiation in an air-breathing complex, mainly represented by the absence of pneumocytes and of compartmentalization in the latest ontogenetic stages.

No MeSH data available.


Related in: MedlinePlus