Structure and functional significance of branched anastomosing mucosal folds in the proximal intestine of the farmed African catfish (Clarias gariepinus Burchell 1822)

Histology has provided morphologist a powerful tool that enhances the nature, form and detailed structure of organs. The proximal intestine though a more muscular tube than the rest of the intestine presented a complex anastomosing mucosal fold resembling a honey comb-like structure. This specialization was not seen in the other intestinal segments. This specialization increases the surface area for nutrient absorption. This probably compensates for shortness of intestine and absence of pyloric caeca in this species. The glycoconjugates in the goblet cell of proximal intestine mucosal fold were subjected to mucin  histochemical study. The study revealed the presence of neutral andacid mucin but acid mucin was predominant. The neutral mucin can be associated to buffering the effect of gastric acid, transport of small disaccharide molecules. The predominating acid mucin suggest air-breathing function since the acid will always make the epithelium moist for gaseous exchange between dissolved air in   swallowed water and abundant blood vessels present in the tunica mucosa.Keywords: Nutrient absorption, Proximal intestine, Anastomosing mucosal folds, Histology, Histochemistry, Clarias gariepinu

Distal Intestinal Caecum of Farmed African Catfish (Clarias gariepinus Burchell, 1822): A Case Report

The microanatomical characteristics of the distal intestinal caecum were investigated. The histology was typical of tubular organs containing tunicamucosa, submucosa, muscularis and adventitia. The lumen was lined by simple mucosal folds. The covering epithelium was of simple columnar cells containing goblet cells and intraepithelial lymphocytes. The lamina propria contained blood vessels, loose connective tissue and leukocytes.The muscularis mucosae of smooth muscle cells were observed. The submucosa contained loose connective tissue, smooth muscle cells, bloodvessels and leukocytes. The tunica muscularis contained a myenteric plexus between the inner circular and outer longitudinal layers of smoothmuscle cells. The mucin histochemistry revealed that the goblet cells present contained neutral and acid mucin but acid mucin predominated suggesting an organ with more need for protection against bacteria in the blind ended tube. When compared with the histology of the intestinal segments cranial and caudal to the diverticulum, the features of thecaecum were very similar to the segment cranial to it necessitating the conclusion that the diverticulum is the distal intestinal caecum. The histology suggests an organ serving as complementary digestivestructure to distal intestine in nutrient absorption without increasing the space occupied by the digestive tract.KEYWORDS: DISTAL, INTESTINAL, CAECUM, FARMED, AFRICAN, CATFISH, CASE REPOR

Morphology of the oropharyngeak cavity and oesophagus of the farmed adult African catfish (Clarias gariepinus Burchell, 1822)

The morphology of the adult farmed African catfish -Clarias gariepinus a prominent omnivorous cultivable species in Nigeria was investigated. It revealed cornified horny plates lining the buccal surfaces of the lips. The tongue was not free moving, and the oesophagus was a narrow tube connecting the oropharyngeal cavity to the stomach with no valve or constriction separating it from the later. Histologically, the cavity wall was lined by stratified squamous epithelium containing eosinophilic club cells, mucous cells and taste buds. The laminar propria contained dense collagen fibres. No taste bud was seen on the tongue suggesting it non involvement in food selection through gustation unlike the cavity wall which contained taste buds. The oesophagus was lined by stratified mucous epithelium containing club cells. Histochemistry revealed the presence of neutral, acid and combination of the two. The large extent of oesophageal mucification indicates need for mucin lubrication of food since teleost is known to lack salivary glands and also an adaptation to ingestion of varied feed.La morfología bagre africano del adulto cultivado -Clarias gariepinus- una especie omnívoras cultivables prominente en Nigeria fue investigada. Reveló placas córneas que cubren las superficies vestibulares de los labios. La lengua no tiene movimiento libre y el esófago es un tubo estrecho que conecta la cavidad orofaríngea al estómago sin válvula o constricción que lo separe. Histológicamente, la pared de la cavidad estaba revestida por epitelio escamoso estratificado que contiene células eosinófilas, células mucosas y papilas gustativas. La laminar propia contenía fibras de colágeno denso. No fie vista ninguna papila gustativa en la lengua lo que sugiere la no participación la selección de los alimentos a través gustación a diferencia de la pared de la cavidad que contiene papilas gustativas. El esófago estaba revestido por epitelio estratificado que contiene células mucosas. La histoquímica reveló la presencia de ácido a neutro, y la combinación de los dos. La gran extensión de mucificación esofágica indica la necesidad de lubricación de mucina de los alimentos se sabe que los teleósteos carecen de glándulas salivales y también una adaptación a la ingestión de alimentos variados

The histomorphology of the African palm squirrel (Epixerus ebii) lacrimal gland.

The histomophology of the dorso-lateral lacrimal gland of the African Palm Squirrel –Epixerus ebii, was investigated to establish its normal histology. The grossly almond shaped organ appeared as a pink coloured U-shaped structure with lobules on low magnification. The organ was coated by thin connective tissue fibres. The lobules averaging seven in number contained tubuloalveoalar glands. The cells of the glands were typically serous cells with low columnar shape containing basally located ovoid to spherical nucleus. While some gland acini lumen contained foamy eosinophilic secretions, other acini contained foamy eosinophilic secretions with basophilic materials. These acini were designated types I and II respectively. Periodic acid Schiff reaction revealed that the basement membrane were PAS positive while the gland secretions were poorly PAS positive. This data will fill the knowledge gap and aid biologists’, comparative anatomists’ in further investigative research, while it will be of interest to wildlife clinicians in this species disease management

Corneal Histomorphology of the Adult Squirrel (Epixerus ebii)

The cornea is the transparent anterior portion of the fibrous tunic of the globe. It is the most important structure of the ocular surface for the maintenance of vision. The histomorphology of the Squirrel (E.ebii) cornea was investigated in this study. The Squirrel cornea consisted of five layers – Anterior epithelium, anterior limiting membrane (Bowman’s membrane), substancia propria (stroma), posterior limiting membrane (Descement’s membrane) and posterior epithelium (endothelium).The anterior epithelium was of the non-keratinized stratified squamous type sitting on a vaguely defined PAS positive anterior limiting membrane. The stroma was made up of regularly arranged collagen fibers with fibrocytes found between the lamella. The posterior limiting membrane was present and was PAS positive. The posterior epithelium consisted of a single layer of large squamous cells

Lip histology of the adult farmed African Catfish (Clarias gariepinus)

The lip histology of the adult farmed African catfish was investigated to fill the knowledge gap in available literature especially those from commercial concrete tanks. This microanatomy is important as the lip is the principal organ involved in prehension. The lip epidermis was lined by stratified squamous epithelium containing PAS and AB positive mucous cells, and occasional eosinophilic club cells. Some melanocytes were seen at the basal epithelial layer and subepithelium. Pectinate ligament of dense regular connective tissue was seen attaching the epithelium to the deep dermal dense regular connective tissue. This deep dense regular connective tissue was seen ventral to the subepithelial loose areolar connective tissue. In the lower lip, the core contained skeletal muscle fibres in varying directions, elastic cartilage, and bone. This core provides anchorage for the horny pad teeth. Abundant nerve fibres were observed in the deep connective tissue layers. No taste bud was observed. This microanatomical observation suggests an organ involved in prehension and tearing of feed; protractibility, protection but no gustatory function.Keywords: Pectinate ligament, mucous cells, club cells, Histology, lip

Histological study of the pharyngeal pad of the african catfish (Clarias gariepinus Burchell 1822)

The pharyngeal pad located dorsally on the oro-pharynx was processed for light microscopy. The epithelium was of stratified mucous type containing taste buds, club cells and teeth. The micromorphology revealed the co-localization of teeth and taste bud. Developing, erupting and erupted teeth were also seen. The thin bone of cancellous type with a marrow seen provided point of origin and insertion for the skeletal muscle present. Osteoblasts were seen on the surface of the cancellous bone probably depositing bone matrix. The pad had a base of hyaline cartilage. Stratum adiposum was observed and may be site for nutrient storage and also function in reducing friction between sliding muscle fibres since it was sandwiched between muscle fibres. The micromorphology suggest an organ used in trituration and selection of food by gustation. The blood vessels in the bone marrow suggest haematopoietic function. The bone and cartilage present is for support.Keywords: Pharyngeal pad, Histology, Food selection, Taste bud, African catfishAnimal Research International (2012) 9(3): 1613 – 161