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International Journal of Morphology

On-line version ISSN 0717-9502

Int. J. Morphol. vol.21 no.3 Temuco  2003

http://dx.doi.org/10.4067/S0717-95022003000300003 

Int. J. Morphol., 21(3):199-204, 2003.

HISTOLOGICAL STUDY OF THE SALIVARY GLANDS IN
Dasypus hybridus (MAMMALIA, DASYPODIDAE)

ESTUDIO HISTOLÓGICO DE LAS GLÁNDULAS SALIVALES DE
Dasypus hybridus (MAMMALIA, DASYPODIDAE)
*Stella Maris Codón; *Silvia Estecondo; **Emma Beatriz Casanave 

CODÓN, S. M.; ESTECONDO, S. & CASANAVE, E. B. Histological study of the salivary gland in Dasypus hybridus (Mammalia, Dasypodidae). Int. J. Morphol., 21(3):199-204, 2003.

SUMMARY: The histology of the salivary glands of the armadillo Dasypus hybridus (Desmarest, 1804), was studied. Two pairs of salivary glands, parotid and submaxillary, and a salivary bladder are distinguished. Parotids are located anteriorly to the submaxillary glands. They are purely serous glands and excretory intralobular ducts, intercalated and particularly striated ones, are very numerous. Submaxillary glands are of greater size. They possess two lobes, which differs in their histology and histochemistry. The anterior lobe is mixed and the presence of numerous intralobular excretory ducts is remarkable. The bigger posterior lobe is mucous. Intralobular excretory ducts are observed, but they are not as abundant as in the anterior portion.

KEY WORDS. 1. Mammals; 2. Armadillos; 3. Dasypodidae; 4. Dasypus hybridus; 5. Histology; 6. Salivary glands. 


INTRODUCTION

Studies carried out by numerous investigators show a great anatomical, histological and histochemical diversity in the salivary glands of mammals (Shackleford & Klapper, 1962; Hagelqvist et al., 1991; Meyer et al., 1993; Tandler et al., 1994; Watanabe et al., 1996). Those glands vary in number, size and location in different species (Fahrenholz, 1937; Shackleford & Wilborn, 1968; Wilborn & Shackleford, 1969; Pérez Clavier, 1976; Young & Lennep, 1978).

In Dasypodidae, the salivary glands are of big dimensions and the presence of a salivary bladder is a particular characteristic (Pouchet, 1868; Burne, 1901; Grassé, 1955; Warren, 1959; Shackleford,1963; Fava de Moraes, 1965). Morphological studies carried out in salivary glands of some armadillos showed distinctive features (Pouchet; Burne; Shackleford; Ruby & Allen, 1976; Ruby, 1978; Ruby & Canning, 1978; Estecondo et al., 1995, 2002). Little is known about Dasypus hybridus (Cuba Caparo, 1979). The objective of this work is to describe the histological and histochemical structure of the salivary glands of this species, commonly known as "mulita". Results are compared with those available for other Dasypodidae.

MATERIAL AND METHOD

Six adult armadillos Dasypus hybridus of both sexes were used; they were live-trapped in a ratio of 40-90 km southwest of the Bahía Blanca city, Province of Buenos Aires, Argentina. Animals were euthanized with 75 mg/kg sodium thiopentate (i. p.) and salivary glands were removed. They were fixed in Bouin´s solution, dehydrated and included in paraffin 56-58°C. Transverse and longitudinal sections at 5µm thickness were made with a Leitz microtome and stained with haematoxylin-eosin, Masson´s trichrome, perioidic acid Schiff reaction (PAS) and Alcian Blue (AB) pH 2.5. They were examined and photographed with a Nikon AFM microscopy.

RESULTS

Two pairs of tubuloacinar exocrine salivary glands are distinguished: parotid and submaxillary. They are surrounded by a capsule of dense connective tissue, which penetrates toward the interior of the glands. Septa of this connective tissue, containing blood vessels and excretory conduits, divide the gland into lobes and lobules. Sublingual glands were not observed.

There is a salivary bladder related with the submaxillary gland. It is covered by a pseudostratified columnar epithelium, lying over connective tissue and a thick layer of striated skeletal muscle with circular and longitudinal fibbers (Fig. 1).


Fig. 1. Salivary bladder with pseudostratified columnar epithelium (arrow), connective tissue (c) and a thick layer of striated skeletal muscle (m). Masson. 100X. Inset: Detail of the epithelium. Masson. 400X.

Parotids glands are located anteriorly to the submaxillary glands, having their posterior portion in close contact with the anterior part of the latter. They are composed exclusively of small serous acini with pyramidal cells, having basal basophilic and apical eosi-nophilic cytoplasm, rounded and basal nuclei and small acinar lumen (Figs. 2, 3). The acinar cells are strongly PAS+ (Fig. 4) and give no reaction with AB pH 2.5 (Fig. 5). The intralobular excretory ducts are very numerous (Figs. 2, 3). There are inter-calated ducts with cubical epithelium connecting the acini with the striated ducts. The last ones, more nume-rous, are enclosed by higher cubical or columnar epithe-lium, with more eosinono-philic cells and basal striations (Fig. 3). In the septa, interlobular conduits of larger calibre encircled by a pseudostratified columnar epithelium, are also observed.


Figs. 2, 3. Parotid gland. Fig. 2. General view showing small serous acini and many intralobular excretory conduits. Masson. 100X. Fig. 3. Section of the gland with serous acini, intercalated (i) and striated (s) intralobular excretory ducts. Masson. 400X.


Figs. 4, 5. Parotid gland. Fig. 4. Strongly PAS positive acini. PAS. 100X. Fig. 5. Alcian Blue negative acini. AB pH 2.5. 100X.

Submaxillary glands are of greater size and are located caudal to the parotid glands. They have two lobes, which differs in their histo-logy and histochemistry (Fig. 6). The anterior lobe, of smaller size, is mixed (Figs. 6, 7). The mucous component is formed by small mucous acini with spongy cytoplasm stained blue pale with Masson, and flattened nuclei located close to the base of the cells. The serous component of this lobe is formed by serous demilunes formations and occasionally there are serous acini (Figs. 6, 7). It is remarkable the presence of numerous, well-developed intralobular intercalated and striated excretory ducts (Figs. 6, 7), as well as interlobular conduits. The posterior lobe, of more size, is mucous. It is almost exclusively formed by mucous acini , which are more voluminous and darker with Masson (Fig. 6, 8). They have clear cellular limits, more homogeneous cytoplasm, flattened and basal nuclei and small, irregular acinar lumen (Fig. 8). Intercalated and striated ducts are less abundant than in the anterior portion (Fig. 6). Interlobular conduits are also observed in the septa.


Figs. 6, 7 and 8. Submaxillary gland. Fig. 6. General view of the anterior (a) and posterior (p) lobes; note the abundance of intralobular ducts in the anterior lobe. Masson. 100X. Fig. 7. Anterior lobe with small and clear mucous acini (m) and serous demilunes (arrow). Note the presence of intralobular intercalated (i) and striated (s) conduits. Masson. 400X. Fig. 8. Posterior lobe, with more voluminous and darker mucous acini. Masson. 400X.

In the anterior lobe the mucous portion is strongly PAS + and AB pH 2.5 +, while the demilunes and serous acini react intensely with PAS and are negative to the AB pH 2.5 (Figs. 9, 10). In the posterior lobe, the mucous acini react less intensely with PAS and weakly with AB pH 2.5 (Figs. 9, 10).


Fig. 9, 10. Submaxillary gland. Fig. 9. General view of the anterior lobe (a) with mucous acini, serous demilunes and serous acini which react strongly with PAS and posterior lobe (p), with mucous acini which react less intensely with PAS. PAS. 100X. Fig. 10. General view of the anterior lobe (a) with mucous acini AB+ and demilunes and serous acini AB- and posterior lobe (p), with mucous acini which react weakly with AB. AB pH 2.5. 100X.

DISCUSSION

The presence of a salivary bladder is a characteristic of armadillos (Pouchet; Fahrenholz; Grassé; Warren). It has been observed in Euphractus sexcinctus and Chlamyphorus truncatus (Burne), Dasypus novemcinctus (Shackleford; Fava de Moraes), Cabassus loricatus (Fava de Moraes), D. hybridus (Cuba Caparo), Chaetophractus villosus and Chaetophractus vellerosus (Estecondo et al., 1995) and Zaedyus pichiy (Estecondo et al., 2002). It is histologically similar in all the species, since their wall is formed mainly by striated skeletal muscle. Nevertheless, the pseudostratified columnar lining epithelium here described differs from the informed by Cuba Caparo, who considered this epithelium in

D. hybridus as simple cubical or columnar. Moreover, it differs from the stratified columnar one refered for Cabassus loricatus and D. novemcinctus (Fava de Moraes); and from the simple one reported for D. novemcinctus (Shackleford) and Chaetophractus (Estecondo et al., 1995).

As well as in D. novemcinctus (Shackleford; Shackleford & Wilborn; Ruby & Allen; Ruby), we have not observed sublingual glands in D. hybridus. Nevertheless, it must be established that a true sublingual gland was observed in other armadillos as Chaetophractus (Estecondo et al., 1995), Zaedyus (Estecondo et al., 2002), Chlamyphorus truncatus and Euphractus sexcinctus (Burne).

Parotid glands serous acini are similar to those of Chaetophractus (Estecondo et al., 1995), Zaedyus (Estecondo et al., 2002), Cabassus loricatus and D. novemcinctus (as were described by Fava de Moraes). However, it must be pointed out that in the interpretation of Shackleford, the parotid glands acini of D. novemcinctus would be seromucous, and then different from those of D. hybridus.

The strongly reaction to PAS here observed, is comparable to the one described in D. novemcinctus (Shackleford). Nevertheless, the absence of reaction with AB pH 2.5 is a noticeable difference with D. novemcinctus, where the acini are strongly AB+ (Shackleford).

The great quantity of intralobular ducts in the parotid glands of D. hybridus, particularly striated ones, correspond with the described by Fava de Moraes for D. novemcinctus and is a clear morphological difference with Cabassus loricatus (Fava de Moraes) and Chaetophractus (Estecondo et al., 1995).

The presence of two histological and histochemical well-differenced lobes in the submaxillary glands of D. hybridus, coincides with the informed for D. novemcinctus (Shackleford) and Chaetophractus (Estecondo et al., 1995). Although the histological and histochemical characteristics observed in those lobes closely resemble the reported by Shackleford for D. novemcinctus, they differed from both points of view with the ones observed for Chaetophractus (Estecondo et al., 1995). Those findings clearly suggest that the secretion of both lobes would be different between them and among the species.

In addition, the histological structure of the anterior and posterior lobes of the submaxillary glands in D. hybridus, coincides with the reported for D. novemcinctus and Cabassus loricatus by Fava de Moraes for the sublingual and submaxillary glands, respectively. Therefore, and also coinciding with Shackleford, we think that in D. hybridus the anterior lobe of the submaxillary gland might probably function as sublingual and the posterior one as a true submaxillary gland. Furthermore, in our opinion, the figure showed by Cuba Caparo as submaxillay in D. hybridus, would be an histological section of the posterior lobe of this gland, and the one presented as sublingual, would correspond to the anterior lobe of the submaxillary gland.

Finally, we emphasised the great quantity of intralobular ducts in the anterior lobe of the submaxillary gland in D. hybridus, not informed previously for other armadillos, and its scarce number in the posterior lobe, already reported in the submaxillary gland of D. novemcinctus (Fava de Moraes).


CODÓN, S. M.; ESTECONDO, S. & CASANAVE, E. B. Estudio histológico de las glándulas salivales de Dasypus hybridus (Mammalia, Dasypodidae). Int. J. Morphol., 21(3):199-204, 2003.

RESUMEN: Se estudió la histología de las glándulas salivales del armadillo Dasypus hybridus. Se distinguen dos pares de glándulas salivales, parótidas y submaxilares y un reservorio salival. Las parótidas se localizan en posición anterior con respecto a las submaxilares, son glándulas exclusivamente serosas y los conductos intralobulares excretores intercalares y, particularmente estriados, son muy numerosos. Las glándulas submaxilares son de mayor tamaño y poseen dos lóbulos que difieren tanto histológica como histoquímicamente. El lóbulo anterior es mixto y resulta notable la presencia de numerosos conductos intralobulares. El lóbulo posterior, de mayor tamaño, es mucoso. Se observan conductos intercalares y estriados, no tan abundantes como en la porción anterior.

PALABRAS CLAVE. 1. Mamíferos; 2. Armadillos; 3. Dasypodidae; 4. Dasypus hybridus; 5. Histología; 6. Glándulas salivales. 


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Correspondence to:
Prof. Dra. Stella Maris Codon
Universidad Nacional del Sur
Depto. Biología, Bioquímica y Farmacia
San Juan 670
B8000FWB
Bahía Blanca
ARGENTINA

Email smcodon@criba.edu.ar

Received : 09-06-2003
Accepted : 10-07-2003


* Laboratorio de Histología Animal, Depto. de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (U.N.S.), Bahía Blanca, Argentina.
* * Laboratorio de Fisiología Animal, Depto. de Biología, Bioquímica y Farmacia, U.N.S., Bahía Blanca, Argentina; Member of the Researcher Career of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.

The paper was supported by Secretaría General de Ciencia y Tecnología, UNS, Projects 24/B060 and 24/B086.

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