Stereological estimation of the surface area and oxygen diffusing capacity of the respiratory stomach of the air‐breathing armored catfish Pterygoplichthys anisitsi (Teleostei: Loricariidae)

Abstract

The stomach of Pterygoplichthys anisitsi has a thin, translucent wall and a simple squamous epithelium with an underlying dense capillary network. In the cardiac and pyloric regions, most cells have short microvilli distributed throughout the cell surface and their edges are characterized by short, densely packed microvilli. The mucosal layer of the stomach has two types of pavement epithelial cells that are similar to those in the aerial respiratory organs. Type 1 pavement epithelial cells, resembling the Type I pneumocyte in mammal lungs, are flat, with a large nucleus, and extend a thin sheet of cytoplasm on the underlying capillary. Type 2 cells, resembling the Type II pneumocyte, possess numerous mitochondria, a well-developed Golgi complex, rough endoplasmic reticulum, and numerous lamellar bodies in different stages of maturation. The gastric glands, distributed throughout the mucosal layer, also have several cells with many lamellar bodies. The total volume (air + tissue), tissue, and air capacity of the stomach when inflated, increase along with body mass. The surface-to-tissue-volume ratio of stomach varies from 108 cm(-1) in the smallest fish (0.084 kg) to 59 cm(-1) in the largest fish (0.60 kg). The total stomach surface area shows a low correlation to body mass. Nevertheless, the body-mass-specific surface area varied from 281.40 cm(2) kg(-1) in the smallest fish to 68.08 cm(2) kg(-1) in the largest fish, indicating a negative correlation to body mass (b = -0.76). The arithmetic mean barrier thickness between air and blood was 1.52 +/- 0.07 microm, whereas the harmonic mean thickness (tau(h)) of the diffusion barrier ranged from 0.40 to 0.74 microm. The anatomical diffusion factor (ADF = cm(2) microm(-1) kg(-1)) and the morphological O(2) diffusion capacity (D(morphol)O(2) = cm(3) min(-1) mmHg(-1) kg(-1)) are higher in the smallest specimen and lower in the largest one. In conclusion, the structure and morphometric data of P. anisitsi stomach indicate that this organ is adapted for oxygen uptake from air.

Oxidative stress in Nile tilapia (Oreochromis niloticus) and armored catfish (Pterygoplichthys anisitsi) exposed to diesel oil

“…These factors make the fish easily accessible for ecotoxicological studies. P. anisitsi have accessory air-breathing mechanisms (Cruz et al 2009) and when they rise to the surface to breathe they make contact with the diesel-insoluble portion. Thus, despite the fish's benthic habit, diesel oil at the doses tested was able to generate oxidative stress and affect the fish's metabolism.…”

“…Studies on benthic animals can provide important data on differential responses of organisms to pollutants in different aquatic matrices. Pterygoplichthys anisitsi is a benthic armored catfish (Loricariidae) found in fresh waters of South America throughout the Uruguay, Paraguay, and Paraná River basins, where it inhabits water bodies characterized by low oxygen concentrations (Cruz et al 2009). This South American endemic species has not been used in ecotoxicological studies, and data generated from it could be of great importance for research on biomonitoring benthic freshwater environments in South America.…”

Stable carbon and nitrogen incorporation in blood and fin tissue of the catfish Pterygoplichthys disjunctivus (Siluriformes, Loricariidae)

“…Perhaps this amount is not reflective of the amount of food the fish are capable of eating, and need to consume, to meet their energetic and nitrogen requirements. Moreover, corn gluten meal, although appropriate for tilapia, which possess an acidic stomach, may not be digested as efficiently by P. disjunctivus, which lacks a gastric stomach (da Cruz et al 2009;German 2009b).…”

Breaking wind to survive: fishes that breathe air with their gut

“…Other authors report the complete absence of digestive glands in the ABO stomach of loricariids (Carter, ; Oliveira et al , ). Surfactant‐producing lamellar bodies have also been documented in the stomach epithelial cells and gastric glands of Ancistrus (Satora & Winnicki, ), Hypostomus (Podkowa & Goniakowska‐Witalińska, ) and Pterygoplichthys (Cruz et al , ).…”

“…The ranges reported fall within those of other fish non‐gut ABOs and are in the range of mammalian lung diffusive distances (Weibel, ). Capillary densities of gut ABOs are typical for fish ABOs in general (Podkowa & Goniakowska‐Witalińska, , ; Cruz et al , ). Cruz et al () found the diffusing capacity of the Pterygoplichthys (Loricariidae) stomach ABO to be higher than for most other fish ABOs, but lower than published values for the lungs of the South American lungfish Lepidosiren paradoxa Fitzinger 1837 and the marbled lungfish Protopterus aethiopicus Heckel 1851 and substantially below estimates for lungs of same‐sized mammals (Weibel, ).…”