Biological Aspects of the Tongue and Oropharyngeal Cavity of the Eurasian Collared Dove (Streptopelia decaocto, Columbiformes, Columbidae): Anatomical, Histochemical, and Ultrastructure Study

We characterized the morphological and anatomical adaptations of the lingual microstructures of the Eurasian collared dove and discussed their implications for its dietary niche. We analyzed tongues of nine S. decaocto using histological, histochemical, stereomicroscopic, and scanning electron microscopic techniques. Our findings showed that the tongue is relatively short with a tapered apex that carries a terminal lingual nail. However, the lingual body has median scales and is bordered laterally by filiform papillae. Further, the tongue body bears a distinctive papillary crest. The tongue root is nonpapillate and infiltered with orifices of the posterior salivary glands. The bulky laryngeal mound has a circular glottic fissure, carrying a single row of papillae at the rear edge. Concurrently, our histological and histochemical findings demonstrate that the tongue has taste buds, anterior and posterior salivary glands, along with an elongated entoglossum that extends from lingual apex to root. Besides, ovoid and globular mucous glands displayed intense alcianophilic reactions. More substantially, the palate is made up of three palatine ridges with a caudal choanal cleft that was bounded by two rows of palatine papillae. Our data indicate multiple and novel structural variations for the lingual and palatal sculptures coopted for their feeding style.

Macro- and microstructures of the digestive tract in the Eurasian collared dove, Streptopelia decaocto (Frivaldszky 1838): Adaptive interplay between structure and dietary niche

We describe the functional morphology of the digestive tract of the Eurasian collared dove, Streptopelia decaocto using anatomical, morphometric, histological, histochemical, and ultrastructure techniques, and relate our findings to the species' dietary niche. Our results revealed that the esophagus is displaced on both sides of the neck and has highly folded tunica mucosa, which confer greater elasticity for efficient swallowing and passage of food to the crop. The proventriculus is delicate and its mucosal layer contains polymorphic glands with dense profound and superficial secretory units that open to the luminal surface by gastric pores. The ventriculus is biconvex and lined with a keratinized koilin membrane. The tubular glands within the mucosal lining include the isthmus, the neck, and the basal segment that comprise chief and basal cells with prominent nuclei. At the cuticle-mucosal interface, pyramidal vertical rodlets of the cuticle are secreted and superficially covered by a thin film of a horizontal matrix. The mucosa of the ileum form pyramidal villi that are oriented perpendicularly to the central lumen. Enterocytes infiltrated with goblet cells make up the epithelial lining of the villi. There are subtle differences in the thicknesses of corresponding tunics together with histochemical reactions of alcian blue (AB) and Masson-Goldner trichrome (MT) for their microstructures. Overall, our findings reveal remarkable convergence of both macro-and microstructures in S. decaocto to other granivorous species, and offer further evidence of the close association between functional morphology and feeding style relative to food swallowing, digestion, and absorption.

Optimization of the Protocol for Cryopreservation of Arabian Stallion Spermatozoa: Effects of Centrifugation, Semen Extenders and Cryoprotectants

BACKGROUND

Cryopreservation of Arabian stallion semen is important in order to improve the function and fertility of frozen/thawed semen in this breed.

OBJECTIVE

To investigate the effects of centrifugation, type of semen extenders, and type of cryoprotectants on the quality of frozen/thawed Arabian stallion spermatozoa.

MATERIALS AND METHODS

Semen samples collected from four adult Arabian stallions (one ejaculate per week for 10 consecutive weeks) were either processed directly without centrifugation (no centrifugation; NC) or subjected to centrifugation on the gel-free fraction. Centrifugation protocols were divided into six categories; 600 x g for 10 min (C1), 600 x g for 15 min (C2), 900 x g for 10 min (C3), 900 x g for 15 min (C4), 1200 x g for 10 min (C5), or 1200 x g for 15 min (C6) (Experiment 1). Two semen extenders, INRA-82 and modified Kenney's were compared (Experiment 2). Three different cryoprotectants, [namely 5% glycerol, 5% dimethylformamide (DMF) and 2.5% glycerol] plus 2.5% DMF were used (Experiment 3). Following freezing and thawing, motility, viability, plasma membrane integrity, acrosome status and viability index were evaluated.

RESULTS

Centrifugation at 600 x g for 15 min before cryopreservation increased (P< 0.05) sperm motility, viability, membrane integrity and percentage of spermatozoa with intact acrosome compared to other centrifugation protocols. Dilution of Arabian stallion semen with INRA-82 before cryopreservation improved (P< 0.05) sperm quality after freezing and thawing compared to modified Kenney's extender. Supplementation of semen diluent INRA-82 with 5% DMF improved (P< 0.05) the quality of frozen/thawed Arabian stallion spermatozoa compared to 5% glycerol.

CONCLUSION

These findings suggest that optimized conditions such as centrifugation, types of semen extenders and cryoprotectants play an important role in processing Arabian stallion spermatozoa for cryopreservation.