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Scanning electron micrography of the inner lining of the prerectal alimentary tract of Tylosurus gavialoides. A: Primary and secondary folding in the esophagus. B: Intestinal villus covered in hexagonal epithelial cells and pores (arrow). C: Primary and secondary folding in the anterior intestine. D: Villar pores (arrow in the lining of the anterior intestine). E: Primary and secondary folding of the posterior intestine. F: Villar pores (arrow of the posterior intestine).
Source publication
Belonidae are unusual in that they are carnivorous but lack a stomach and have a straight, short gut. To develop a functional morphological model for this unusual system the gut contents and alimentary tract morphology of Tylosurus gavialoides and Strongylura leiura ferox were investigated. The posterior orientation of the majority of the pharyngea...
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... revealed complex folding patterns, includ- ing primary and secondary folding, in the mucosae of each section (Figs. 3-5). The esophageal mucosa presented an irregular zig-zag folding (Fig. 3A); however, the folds were less amplified than in other sections. Luminal faces of epithelial cells and pore openings occurred on the surface of the villi (Fig. 3B). More accentuated zig-zag folding patterns occurred in the anterior intestine (Fig. 3C). Valleys were ...
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... revealed complex folding patterns, includ- ing primary and secondary folding, in the mucosae of each section (Figs. 3-5). The esophageal mucosa presented an irregular zig-zag folding (Fig. 3A); however, the folds were less amplified than in other sections. Luminal faces of epithelial cells and pore openings occurred on the surface of the villi (Fig. 3B). More accentuated zig-zag folding patterns occurred in the anterior intestine (Fig. 3C). Valleys were clearly apparent (Fig. 3C), as were pore openings on the villi (Fig. ...
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... revealed complex folding patterns, includ- ing primary and secondary folding, in the mucosae of each section (Figs. 3-5). The esophageal mucosa presented an irregular zig-zag folding (Fig. 3A); however, the folds were less amplified than in other sections. Luminal faces of epithelial cells and pore openings occurred on the surface of the villi (Fig. 3B). More accentuated zig-zag folding patterns occurred in the anterior intestine (Fig. 3C). Valleys were clearly apparent (Fig. 3C), as were pore openings on the villi (Fig. 3D). The luminal surfaces of epithelial cells could not be distin- guished. The posterior intestine showed a complex, irregular folding pattern, similar to the ...
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... mucosae of each section (Figs. 3-5). The esophageal mucosa presented an irregular zig-zag folding (Fig. 3A); however, the folds were less amplified than in other sections. Luminal faces of epithelial cells and pore openings occurred on the surface of the villi (Fig. 3B). More accentuated zig-zag folding patterns occurred in the anterior intestine (Fig. 3C). Valleys were clearly apparent (Fig. 3C), as were pore openings on the villi (Fig. 3D). The luminal surfaces of epithelial cells could not be distin- guished. The posterior intestine showed a complex, irregular folding pattern, similar to the anterior intestine (Fig. 3E). Valleys occurred, and pore openings were abundant on the villi ...
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... esophageal mucosa presented an irregular zig-zag folding (Fig. 3A); however, the folds were less amplified than in other sections. Luminal faces of epithelial cells and pore openings occurred on the surface of the villi (Fig. 3B). More accentuated zig-zag folding patterns occurred in the anterior intestine (Fig. 3C). Valleys were clearly apparent (Fig. 3C), as were pore openings on the villi (Fig. 3D). The luminal surfaces of epithelial cells could not be distin- guished. The posterior intestine showed a complex, irregular folding pattern, similar to the anterior intestine (Fig. 3E). Valleys occurred, and pore openings were abundant on the villi (Fig. 3E). The inner surface of the ...
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... folding (Fig. 3A); however, the folds were less amplified than in other sections. Luminal faces of epithelial cells and pore openings occurred on the surface of the villi (Fig. 3B). More accentuated zig-zag folding patterns occurred in the anterior intestine (Fig. 3C). Valleys were clearly apparent (Fig. 3C), as were pore openings on the villi (Fig. 3D). The luminal surfaces of epithelial cells could not be distin- guished. The posterior intestine showed a complex, irregular folding pattern, similar to the anterior intestine (Fig. 3E). Valleys occurred, and pore openings were abundant on the villi (Fig. 3E). The inner surface of the rectum was elaborate and less regular than the other ...
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... More accentuated zig-zag folding patterns occurred in the anterior intestine (Fig. 3C). Valleys were clearly apparent (Fig. 3C), as were pore openings on the villi (Fig. 3D). The luminal surfaces of epithelial cells could not be distin- guished. The posterior intestine showed a complex, irregular folding pattern, similar to the anterior intestine (Fig. 3E). Valleys occurred, and pore openings were abundant on the villi (Fig. 3E). The inner surface of the rectum was elaborate and less regular than the other sections (Fig. 4A). Valleys were abundant (Fig. 4B), as were pore openings (Fig. 4C) on the surface of villi. Epithelial cells (Fig. 4D) were only noticeable in the secondary folds of ...
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... (Fig. 3C). Valleys were clearly apparent (Fig. 3C), as were pore openings on the villi (Fig. 3D). The luminal surfaces of epithelial cells could not be distin- guished. The posterior intestine showed a complex, irregular folding pattern, similar to the anterior intestine (Fig. 3E). Valleys occurred, and pore openings were abundant on the villi (Fig. 3E). The inner surface of the rectum was elaborate and less regular than the other sections (Fig. 4A). Valleys were abundant (Fig. 4B), as were pore openings (Fig. 4C) on the surface of villi. Epithelial cells (Fig. 4D) were only noticeable in the secondary folds of the ...
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... of a fish, by having a Falcon tube inserted while fresh, showed flattened folds in the alimentary tract wall (Fig. 5A). In the anterior intestine, mucus and numerous pore openings were present in the valleys and on the edge of villi (Fig. 5B). Few pores occurred on the crests of the villi. Unlike the nonexpanded preparation of anterior intestine (Fig. 3B), the luminal surfaces of epithe- lial cells were not clearly visible on the villi. The valleys and edges of villi in the posterior intestine were covered by numerous pore openings but some also occurred on the crests of the villi (Fig. ...
Citations
... The stomach plays a role in the storage and digestion of food [44]. Some fish species, such as zebrafish (Danio rerio), ballan wrasse (Labrus bergylta), garfish (Belone belone), and needlefish (Tylosurus gavialoides and Strongylura leiura ferox) do not have stomachs [45][46][47]. The morpho-histological results of the red snapper stomach in this study are comparable to our previous study on Asian seabass [19]. ...
This study offers a comprehensive morpho-histological analysis of the gastrointestinal tract (GIT) of the Malabar red snapper. A comparison of its GIT morphology with that of the Asian seabass reveals similarities and differences between the two species. Additionally, the moisture content, crude protein, and ash in the fillets of Malabar red snapper and Asian seabass were slightly different, with Malabar red snapper exhibiting higher levels of essential fatty acids. Furthermore, higher levels of the polyunsaturated fatty acid (PUFA)/saturated fatty acid (SFA) ratio and docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratio, and a lower omega-6/omega-3 ratio, were observed in Malabar red snapper compared to Asian seabass. The Malabar red snapper’s esophagus featured protective mechanisms such as simple columnar epithelial cells, mucous-secreting glands, and goblet cells that were predominantly stained for acid and neutral mucosubstances. Furthermore, its stomach, with mucus cells that were weakly stained for acid mucosubstances, exhibited distinct regions with varying glandular densities, with the pyloric region featuring few glands. The pyloric caeca of the fish were composed of five finger-like structures and few goblet cells. Several goblet cells gradually increased from the anterior to the posterior region of the intestine. These findings provide useful insights for the aquaculture sector, focusing on Malabar red snapper.
... The oral teeth are differentiated by size, and its location has an apical curvature directed toward the interior of the cavity, suggesting that the primary use of their teeth is to catch prey and prevent it from escaping. The second line of small teeth could be related also to killing, disabling, and swallowing the prey, with the help of the tongue (Manjakasy et al., 2008). Interestingly, the few oral teeth of the large-first category with a curvature directed toward an exterior angle could also be armaments related to agonistic combats during intra-sexual selection. ...
... We demonstrated it since we only found small, unchewed crustaceans with their interior contents intact in all sections of the intestine. Also, it is reasonable to suggest that the curvature of the teeth in a posterior direction could prevent prey from returning to oral cavity as a secondary function (Manjakasy et al., 2008;Tibbetts et al., 2008). Since the exoskeleton, and tissues of ingested prey are perforated in this region, it may explain why it was where the largest number of taste corpuscles was found, because fishes taste the substances emanating from their "broken" prey with them (Konishi & Zotterman, 1963). ...
Annual killifishes have active and voracious rates in acquisition of food resources with display of behaviors that allow them to maintain high metabolic rates to deal with the harsh and unpredictable conditions prevalent in temporary pools where they inhabit. The objective of this research was to describe histologically and ultrastructurally, the digestive system of the annual killifish Millerichthys robustus to identify morphological traits related to its annual life history and digestive physiology. Also, we quantify food items along the intestine as a proxy for rates of digestion. Millerichthys has a short digestive system, associated with a carnivorous diet, with no evidence of a stomach. Instead, the presence of pharyngeal jaws with caniform teeth was documented, related to the breakdown of invertebrate exoskeletons, allowing prey fluids to be tasted by taste corpuscles related to selection of food items, and that digestive enzymes penetrate once in the intestine. The histological morphology of the intestine showed four different regions, associated with its digestive rates: (i) reception of food from the esophagus with intact pray; (ii) digestion with enzymes from the pancreas and liver/gallbladder of simple exoskeleton prey (Entognatha), and beginning of absorption; (iii) absorption of nutrients, and digestion of large-complex exoskeleton prey (Hexanauplia, Brachiopoda, and Ostracoda); and (iv) probable absorption of intact macromol-ecules. The second region of the intestine presented two anatomical loops and the highest thickness that may be related to reducing the speed of food transit, allowing for more efficient digestion given the large amount of food ingested by this species. K E Y W O R D S annualism, fish digestive system, Millerichthys, Rivulidae, ultrastructure
... Site 'ps7 was not included in the analyses because too deep and not representative of a seagrass habitat. Table S3: list of fish species observed in the videos, including species functional traits (feeding information) [29,46,61,[122][123][124][125][126]; Figure S1: example of (a) an artificial Posidonia unit in a seagrass patch and (b) in a bare area and (c) of a supra-canopy GoPro set up; Figure S2: correlation plots among variables: distance to patch edge, seagrass shoot density, area and level of fragmentation at 50 m, 250 m and 500 m of radius. ...
Habitat complexity plays a critical role in shaping biotic assemblages and ecosystem processes. While the impacts of large differences in habitat complexity are often well understood, we know less about how subtle differences in structure affect key ecosystem functions or properties such as biodiversity and biomass. The late-successional seagrass Posidonia australis creates vital habitat for diverse fauna in temperate Australia. Long-term human impacts have led to the decline of P. australis in some estuaries of eastern Australia, where it is now classified as an endangered ecological community. We examined the influence of P. australis structural complexity at small (seagrass density) and large (meadow fragmentation) spatial scales on fish and epifauna communities, predation and sediment erosion. Fine-scale spatially balanced sampling was evenly distributed across a suite of environmental covariates within six estuaries in eastern Australia using the Generalised Random Tessellation Structures approach. We found reduced erosion in areas with higher P. australis density, greater abundance of fish in more fragmented areas and higher fish richness in vegetated areas further from patch edges. The abundance of epifauna and fish, and fish species richness were higher in areas with lower seagrass density (seagrass density did not correlate with distance to patch edge). These findings can inform seagrass restoration efforts by identifying meadow characteristics that influence ecological functions and processes.
... Agastric fish, rigorously defined as lacking acid-peptic digestion as adults, comprise approximately 20-27% of known species (Wilson and Castro, 2010). Several species have developed accessory anatomical apparatus or gut modifications such as specialized pharyngeal teeth, gizzards, pyloric caeca, long guts, or short-but-wide diameter (Horn, 1989;Stevens and Hume, 2004;Manjakasy et al., 2009;Egerton et al., 2018) to compensate the lack of acid-peptic digestion in a stomach. Notably, despite several short-gut agastric species from the Belonidae family having been described from a nutritional ecology standpoint (Manjakasy et al., 2009), to our knowledge, no representatives of fish with this digestive configuration exist in commercial aquaculture, and their feeding requirements for optimal growth performance are unknown. ...
... Several species have developed accessory anatomical apparatus or gut modifications such as specialized pharyngeal teeth, gizzards, pyloric caeca, long guts, or short-but-wide diameter (Horn, 1989;Stevens and Hume, 2004;Manjakasy et al., 2009;Egerton et al., 2018) to compensate the lack of acid-peptic digestion in a stomach. Notably, despite several short-gut agastric species from the Belonidae family having been described from a nutritional ecology standpoint (Manjakasy et al., 2009), to our knowledge, no representatives of fish with this digestive configuration exist in commercial aquaculture, and their feeding requirements for optimal growth performance are unknown. This information is relevant because feeding frequency can contribute to maximizing growth performance and use of food by reducing waste and production costs (De Silva et al., 2007;Tian et al., 2015;Abdel-Aziz et al., 2021). ...
... Thus, it is an emerging species with excellent potential for aquaculture diversification needs (Little et al., 2016;Martínez-Palacios et al., 2020). Like other carnivore fishes from the Atherinomorpha clade, C. estor lacks a stomach, has a short intestine (relative gut length: 0.7), is prey selective (ram suction feeding), and feed processing occurs in well-developed pharyngeal teeth (Ross et al., 2006;Manjakasy et al., 2009;Martínez-Palacios et al., 2019). However, although significant advances in husbandry for the conservation and commercial production of C. estor have been successfully developed (Martínez-Chávez et al., 2014;Corona-Herrera et al., 2016;Ospina-Salazar et al., 2016;Ríos-Durán et al., 2016;Martínez-Chávez et al., 2018;Juárez-Gutiérrez et al., 2021;Motta et al., 2021), further knowledge on the feeding habits (feeding frequency) associated to the anatomical alimentary canal is required to maximize growth performance and reduce skeletal deformities due to inadequate feeding strategies of this zooplanktophagous fish under culture. ...
Several fish species with potential for aquaculture diversification possess agastric short-intestine anatomical configuration. The absence of a stomach or long intestine in fish may imply specific feeding frequency strategies for optimal growth. Because adequate feeding frequencies are paramount for thriving fish culture, the present study aimed to evaluate the effects of feeding frequency on growth performance, feeding efficiency, survival, deformities, proximate body composition, and muscle growth in Mexican pike silverside (Chirostoma estor: Atherinopsidae) a short-intestine agastric fish. Fish with an average weight of 180.57 ± 3.02 mg were randomly distributed in twelve tanks and fed four (M4), eight (M8), and twelve (M12) times a day until apparent satiety for 45 days. Significantly higher growth (70%) was found in M12 treatment compared to M4. There was no difference in survival among treatments. However, significantly fewer deformities were found in the M12 treatment compared to M8 and M4 treatments. Increased feeding frequency produced fish with higher lipids, with a concomitant reduction in ash content. Muscle fiber diameters were significantly different in all treatments: M12 (32.97 ± 3.13 μm), M8 (30.28 ± 4.59 μm), and M4 (26.74 ± 4. 42 μm). These results reflect the importance of feeding strategies in accordance to fish habits and their digestive configurations and may be relevant for other emerging species with similar digestive morphology and lower in the trophic chain, which are essential for aquaculture diversification and sustainability.
... Many functions have been reported for the fish intestinal bulb. Many authors attributed its role as temporary food storage (Manjakasy et al., 2009;Mokhtar, 2017). Mishra & Ahmed (1991) declared that the intestinal bulb of hillstream teleosts shows structural and physiological absorptive characteristics. ...
The intestinal bulb is a simple dilatation in the anterior part of the intestine of agastric fish. This study was conducted on 18 adult specimens
of molly fish (Poecilia sphenops) and demonstrated the presence of an intestinal bulb. The intestinal epithelium was composed of enter-
ocytes covered with microvilli, many mucous goblet cells, and enteroendocrine cells. Numerous intraepithelial lymphocytes, neutrophils,
plasma cells, dendritic cells, stem cells, rodlet cells, and macrophages were identified in the epithelial layer. Interestingly, this study recorded
the process of autophagy and formation of autophagosomes, multivesicular bodies, and dense bodies. The intestinal epithelium extended
into the intestinal gland that consisted of simple columnar epithelium, mucous cells, stem cells, enteroendocrine cells, and basal cells. These
glands opened to the lumen of the bulb and were surrounded by a network of telocytes. Moreover, immunohistochemistry revealed that the
intestinal epithelium expressed APG5, myostatin, TGF-β, IL-1β, NF-κB, Nrf2, and SOX9. Leukocytes in the lamina propria-submucosa
expressed APG5. The inflammatory cells in the connective tissue showed strong immunoreactivity to myostatin and TGF-β. The smooth
muscular layer also expressed myostatin. Both IL-1β and NF-κB showed immunoreactivity in macrophages in the lamina propria-submu-
cosa. Stem cells expressed Sox-9 and telocytes expressed NF-κB and SOX9; while astrocytes in the tunica muscularis expressed GFAP. The
high frequency of immune cells in the intestinal bulb suggested an immune role of this organ. This is the first study demonstrating the
absence of the stomach and its replacement with an intestinal bulb in molly fish, and consequently, this species could be reclassified as
agastric fish according to this study.
... This study supports the notion that the intestinal bulb of grass carp served as a temporary storage part for ingested food, which is supported by a large lumen diameter and the presence of many plant cells within its lumen. A large number of zigzag-shaped mucosal folds and thick mucosa of the bulb with the resultant increase in the surface area might aid in the mixing of food with hepatic and pancreatic digestive juices as well as with mucus secreted by goblet cells (Manjakasy et al., 2009;Mokhtar, 2017). ...
Cyprinid fishes have one of the simplest types of gastrointestinal tract among vertebrates. Those fish species do not possess a true stomach that is replaced by a simple dilatation at the anterior part of the intestine called the intestinal bulb. Twenty adult specimens of grass carp were used in the present study to identify the cellular components as well as the immunohistochemical and surface architectural characteristics of the intestinal bulb. The mucosa of the intestinal bulb shows numerous, deep longitudinal folds arranged in zigzagging-like patterns. The epithelium is composed mainly of absorptive columnar cells covered by microvilli and mucous goblet cells. Spindle-shaped enteroendocrine cells and some migratory immune cells such as intraepithelial lymphocytes and rodlet cells could be identified between the absorptive cells. The epithelium also contains many secretory granules and large numbers of vacuoles containing digestive enzymes mostly in the basal part. The immunohistochemistry revealed that CD20-positive B-lymphocytes are immunolocalized mainly in the connective tissue core lamina propria of the mucosal folds. However, CD3-immunopositive T-lymphocytes are highly concentrated in the lamina propria. In addition, intraepithelial T-lymphocytes expressed immunopositivity to CD3. The current study presented many types of immune cells and suggests their essential immunological role for the intestinal blub.
... The presence of sialic acid in the acid mucins has been associated with the protection against viruses and bacteria by preventing the recognition of their receptors in the intestinal mucosa (Gisbert et al. 2004, Nazlić et al. 2014). In the posterior intestine, the acid mucins have been related to the evacuation process (Shi et al. 2007), while the neutral mucins are responsible for neutralizing pH and protecting the intestinal mucosa (Manjakasy et al. 2009). ...
The histological structure, histochemical features, and enzymatic activity of the digestive tract of juvenile Pacific seahorse (Hippocampus ingens) are described to provide information during the cultivation of this species. Serial histological sections were stained with either hematoxylin-eosin, alcian blue-PAS, toluidine blue, Sudan black, Masson's trichome, and ninhydrin-Schiff to describe the general features and the presence of glycogen, mucopolysaccharides, lipids, muscle layers, and proteins, respectively. The enterocytes height and the mucosal villi height in the esophagus and intestines were measured. Additionally, the digestive enzymes trypsin, chymotrypsin, lipase, amylase, aminopeptidase, acid phosphatase, and alkaline phosphatase activities were recorded. The esophagus showed two distinctive regions, the anterior with numerous mucous cells secreting acid mucins and the posterior with longitudinal folds and no mucous cells. The intestine was differentiated into three regions. The anterior showed goblet cells secreting acid and neutral mucins, while the middle and posterior regions presented goblet cells secreting only acid mucins. The activity of aminopeptidase, chymotrypsin, and amylase showed low levels, while the trypsin and acid phosphatase activity levels were intermediate. Lipase and alkaline phosphatase showed the highest activities. The results point that juvenile H. ingens presents a digestive structure similar to other teleost species. The high levels of lipase suggest that juvenile H. ingens have high requirements for lipids during this stage.
... The presence of sialic acid in the acid mucins has been associated with the protection against viruses and bacteria by preventing the recognition of their receptors in the intestinal mucosa (Gisbert et al. 2004, Nazlić et al. 2014). In the posterior intestine, the acid mucins have been related to the evacuation process (Shi et al. 2007), while the neutral mucins are responsible for neutralizing pH and protecting the intestinal mucosa (Manjakasy et al. 2009). ...
The histological structure, histochemical features, and enzymatic activity of the digestive tract of juvenile Pacific seahorse (Hippocampus ingens) are described to provide information during the cultivation of this species. Serial histological sections were stained with either hematoxylin-eosin, alcian blue-PAS, toluidine blue, Sudan black, Masson's trichome, and ninhydrin-Schiff to describe the general features and the presence of glycogen, mucopolysaccharides, lipids, muscle layers, and proteins, respectively. The enterocytes height and the mucosal villi height in the esophagus and intestines were measured. Additionally, the digestive enzymes trypsin, chymotrypsin, lipase, amylase, aminopeptidase, acid phosphatase, and alkaline phosphatase activities were recorded. The esophagus showed two distinctive regions, the anterior with numerous mucous cells secreting acid mucins and the posterior with longitudinal folds and no mucous cells. The intestine was differentiated into three regions. The anterior showed goblet cells secreting acid and neutral mucins, while the middle and posterior regions presented goblet cells secreting only acid mucins. The activity of aminopeptidase, chymotrypsin, and amylase showed low levels, while the trypsin and acid phosphatase activity levels were intermediate. Lipase and alkaline phosphatase showed the highest activities. The results point that juvenile H. ingens presents a digestive structure similar to other teleost species. The high levels of lipase suggest that juvenile H. ingens have high requirements for lipids during this stage.
... (Zhang et al., 2016) la región anterior del esófago carece de células mucosas, mientras que en la región posterior las presenta atribuyéndoles la función de protección de la capa mucosa. La secreción de las células mucosas puede clasificarse en mucinas ácidas y neutras (Neuhaus et al., 2007;Murillo-Higuera, 2017) y su presencia se ha reportado en diferentes especies como Chalcalburmus tarichi (Ünal et al., 2001), Sphoeroides testudineus (Fagundes et al., 2015) y Belone belone (Bočina et al., 2017), que presentan mucinas ácidas al igual que en H. ingens, mientras que Tylosurus gavialoides y Strongylura leiura ferox (Manjakasy et al., 2009) reportan mucinas neutras, aunque en ocasiones como Esox lucius y Silurus glanis (Petrinec et al., 2005), Claris batrachus y Serrasalmus nattereri (Raji & Norouzi, 2010) y Lates calcarifer (Purushothaman et al., 2016), poseen ambos tipos de mucinas. El mucus secretado contribuye a la lubricación del alimento a través del esófago hacia el tracto intestinal, y al aumento de la eficiencia digestiva. ...
... La función de las mucinas ácidas está relacionada con la protección ante infecciones, prevenir la degradación de la glicoproteína y principalmente como lubricante, mientras que las mucinas neutras se encargan de la neutralización del pH, la protección de la mucosa intestinal y el proceso de digestibilidad de alimentos (Manjakasy et al., 2009;Cabrera & García, 2010;Murillo-Higuera, 2017). ...
Fishes have a great variety of structural and physiological adaptations that allow them to capture, digest and absorb food. In Hippocampus ingens it has been reported that they do not have teeth or stomach. However, it has the same intestinal structure as in other teleosts. In the present work the histological, histochemical characteristics and the presence of digestive enzymatic activity of the digestive tract of H. ingens are described with the purpose of providing information that can be used in the development of the culture of this species. We obtained 15 juveniles from a farm in Mazatlan, Sinaloa, Mexico. Some of them were fixed in the Davidson´s solution, sectioned at 4 μm using a rotatory microtome and stained with H-E, Alcian Blue-PAS, Toluidine Blue, Masson's Trichrome, Black Sudan and Ninhydrin-Schiff. To the rest, the digestive tract and the accessories were extracted to determine the presence of trypsin activity, chymotrypsin, lipase, amylase, aminopeptidase, acid phosphatase and alkaline phosphatase. The presence of an anterior and posterior esophagus was confirmed. Only the anterior region presents numerous acid-type mucosal cells, while the posterior region has simple cylindrical epithelium. Based on the type of epithelium, presence and height of villi as well as type and coverage of mucins present, the intestine differentiates into three regions. The anterior region presents acidic and neutral mucins, whereas in the middle and posterior regions it presents acidic mucins in greater production. The presence of vacuoles containing triglycerides within the enterocytes of the anterior intestine was recorded, as well as the proteins in the hepatocytes. The activity of aminopeptidase, chymotrypsin and amylase showed very low values with respect to lipase and alkaline phosphatase, which were the highest. Trypsin and acid phosphatase showed intermediate values. These results confirm that H. ingens presents an alkaline intestinal digestion and that it has high lipid requirements.
... The parasites that have been reported from T. gavialoides are the acanthocephala Neoechinorhynchus tylosuri Yamaguti, 1939, caligid copepod Caligodes laciniatus (Krøyer, 1863), isopods Mothocya karobran (Bruce, 1986) and M. renardi (Bleeker, 1857) and the nematodes Philometra lomi and P. kohnae Moravec and Rohde, 1992 [63-66]. Nematodes and unidentified gut parasites have also been reported by Manjakasy, Day, Kemp and Tibbetts [67]. ...
We surveyed 30 individuals of Tylosurus gavialoides (Castelnau) (Belonidae) collected from Moreton Bay, Queensland, Australia, and describe three new species of Prosorhynchoides Dollfus, 1929 from them. The new species are morphologically distinct from existing Prosorhynchoides spp. and 28S and ITS-2 ribosomal DNA data further supports our morphological findings. We also conduct the first mitochondrial DNA analysis of species of Prosorhynchoides. The new species from T. gavialoides form a strongly supported clade on the basis of the two ribosomal markers, further supporting the emerging hypothesis that bucephaline clades are strongly associated with host groups. We have not observed any of the new species reported here in over 3500 surveyed individuals of other piscivorous fish in Australia, suggesting that these species are host-specific at least to belonids, if not to only T. gavialoides. Our findings support previous reports that suggest that belonids are exceptional hosts for bucephalids. We predict that further sampling of the numerous other belonid species present in Australian waters, for which nothing is known of the bucephalid fauna, will uncover further bucephalid richness.
