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Novel structure in sciaenid fish skulls indicates continuous production of the cephalic neuromast cupula

View Article: PubMed Central - PubMed

ABSTRACT

The presence of a conspicuous and frequent but never-described structure in the skull cavities of sciaenid fish was noted during population studies in an urbanized bay. The ultrastructure closely resembles the cupula of neuromasts, an organ associated with the perception of the environment in teleost fish. The bodies were recorded detached in both preserved and freshly sampled individuals and without associated cilia. Prominent characteristics are acellularity, the elliptic-conic shape composed of stack-like protein lamellas, and a mesh-like appearance in cross section. These acellular lamellar cephalic bodies (ALCBs) were more abundant in larger individuals and showed temporal peaks of abundance independently of the fish size. The conic and lamellar features suggest that the deposition of protein layers follows fish growth, and the bimodality of the size of these structures in individuals indicates temporal peaks of production. These results indicate that these ALCBs are a consequence of the accretion of the cupula of neuromasts at a faster rate than they degrade. Given the novelty of this structure and the increasing records of diseases of marine organisms worldwide, an important question is whether these bodies occur subsequently to some environmental change and whether their accumulation in the skull cavities has consequences to fish health.

No MeSH data available.


Upper and lateral surfaces.Basic views of the Acellular Lamellar Cephalic Body: upper (A) and lateral (B) surfaces, under the stereomicroscope. Scales: 1 mm.
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f2: Upper and lateral surfaces.Basic views of the Acellular Lamellar Cephalic Body: upper (A) and lateral (B) surfaces, under the stereomicroscope. Scales: 1 mm.

Mentions: In the interest of readability, we distinguished three basic surfaces: the lower or basal view, which is the larger surface; the upper surface, very similar at first glance to the basal one, but smaller; and the lateral views, both identical. Both the lower and upper surfaces as viewed under the stereomicroscope are elliptic-conical, with a denser central region surrounded by a more translucent, flap-like area (Fig. 2A). In lateral view, an ALCB is somewhat trapezoidal and shows flap-like sides, with a more opaque central region (Fig. 2B). When describing the ultrastructure of the neuromast cupula, Kelly and van Netten15 pointed out that “the cupula is composed of a central region overlying the macula and wings not overlying the macula”. These authors also showed that the central region is composed of a series of compartments that lend it “the appearance of a honey-comb in section”. Both light and SEM microscopy revealed precisely this feature in the ALCBs assessed here (Fig. 3), an extraordinary resemblance to that shown for the cupula, a structure that, as Kelly and van Netten15 mentioned, has a refined structure and is far from being a simple gelatinous mass, as frequently described.


Novel structure in sciaenid fish skulls indicates continuous production of the cephalic neuromast cupula
Upper and lateral surfaces.Basic views of the Acellular Lamellar Cephalic Body: upper (A) and lateral (B) surfaces, under the stereomicroscope. Scales: 1 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120346&req=5

f2: Upper and lateral surfaces.Basic views of the Acellular Lamellar Cephalic Body: upper (A) and lateral (B) surfaces, under the stereomicroscope. Scales: 1 mm.
Mentions: In the interest of readability, we distinguished three basic surfaces: the lower or basal view, which is the larger surface; the upper surface, very similar at first glance to the basal one, but smaller; and the lateral views, both identical. Both the lower and upper surfaces as viewed under the stereomicroscope are elliptic-conical, with a denser central region surrounded by a more translucent, flap-like area (Fig. 2A). In lateral view, an ALCB is somewhat trapezoidal and shows flap-like sides, with a more opaque central region (Fig. 2B). When describing the ultrastructure of the neuromast cupula, Kelly and van Netten15 pointed out that “the cupula is composed of a central region overlying the macula and wings not overlying the macula”. These authors also showed that the central region is composed of a series of compartments that lend it “the appearance of a honey-comb in section”. Both light and SEM microscopy revealed precisely this feature in the ALCBs assessed here (Fig. 3), an extraordinary resemblance to that shown for the cupula, a structure that, as Kelly and van Netten15 mentioned, has a refined structure and is far from being a simple gelatinous mass, as frequently described.

View Article: PubMed Central - PubMed

ABSTRACT

The presence of a conspicuous and frequent but never-described structure in the skull cavities of sciaenid fish was noted during population studies in an urbanized bay. The ultrastructure closely resembles the cupula of neuromasts, an organ associated with the perception of the environment in teleost fish. The bodies were recorded detached in both preserved and freshly sampled individuals and without associated cilia. Prominent characteristics are acellularity, the elliptic-conic shape composed of stack-like protein lamellas, and a mesh-like appearance in cross section. These acellular lamellar cephalic bodies (ALCBs) were more abundant in larger individuals and showed temporal peaks of abundance independently of the fish size. The conic and lamellar features suggest that the deposition of protein layers follows fish growth, and the bimodality of the size of these structures in individuals indicates temporal peaks of production. These results indicate that these ALCBs are a consequence of the accretion of the cupula of neuromasts at a faster rate than they degrade. Given the novelty of this structure and the increasing records of diseases of marine organisms worldwide, an important question is whether these bodies occur subsequently to some environmental change and whether their accumulation in the skull cavities has consequences to fish health.

No MeSH data available.