Surface ultrastructure of gills in relation to the feeding ecology of an angler catfishChaca chaca(Siluriformes, Chacidae)

Abstract

Surface ultrastructure of the gills of the angler catfish Chaca chaca was investigated to unravel the adaptive modifications associated with the feeding ecology of the fish. The fish is often found in mud or in soft substrates where they remain buried both for protection and to feed. Gill rakers present on the gill arch in most fish species are absent in this fish. The absence of gill rakers are associated with the feeding habit of the fish and is considered to facilitate the swallowing of captured prey smoothly without any hindrance. Highly corrugated surface of the gill arch and gill filaments could be associated to retain water/mucus to prevent dessicassion of the fish. Papillae like epithelial protuberances each bearing a taste bud at its summit toward the pharyngeal side of the gill arch is associated with the sorting of the food. Large number of mucous goblet cells on the gill arch epithelium are considered to secret copious mucus to lubricate the prey for easy swallowing. In C. chaca the gill septa between gill filaments are reduced. This could enhance the flexibility and permit the free movement of the gill filaments. Extensive secondary lamellae and infrequent mucous goblet cells on secondary lamellae are associated to increase the surface area to enhance efficiency of gaseous exchange.

Gill morphology of Bagrus bayad (Forskal, 1775) using scanning electron microscopy

“…The main gill's functions are gas exchange in nearly all fishes, some waste products elimination, and the conservation of the fish's salt equilibrium (Perna & Fernandes, 1996). Today, the significance of structure and function of gills were studied in different fish species (M. Abumandour & El‐Bakary, 2017; M. Abumandour & Gewaily, 2016b; M. M. Abumandour, 2019; Alsafy, 2013; Hanafy, 2020; Mistri, Verma, Kumari, Mittal, & Mittal, 2016). Great variability in the structure of the gills thus demanding to study its morphology to provide information about its histophysiology in fishes in various environments (D. R. Eiras‐Stofella & Charvet‐Almeida, 2000).…”

Actin Microridges

“…While microridges have been extensively described in fish skin (Hawkes, 1974;Bereiter-Hahn et al, 1979;Fishelson, 1984;Arellano et al, 2004;Mistri et al, 2018), these structures are found in many other types of teleost tissue. Cornea (Collin and Collin, 1997, 2000, gills (Arellano et al, 2004;Eiras-stofella, 2000;Kumari et al, 2009;Mistri et al, 2016), nasal epithelium (Zeiske et al, 1994;Hansen and Zeiske, 1998), operculum (Mittal et al, 2004), head/ snout epidermis (Rai et al, 2012), and oral mucosa (Uehara et al, 1988(Uehara et al, , 1990Kumari et al, 2005) have all been shown to have microridges protruding from outer surfaces of the superficial layer. Microridges have also been identified in the epithelial enveloping layer (EVL) of gastrulating zebrafish (Danio rerio) embryos (Zalik et al, 1999;Crawford et al, 2003), on the surface of unfertilized Brachydanio eggs (Hart and Donovan, 1983), and in superficial epithelium of embryonic Poeciliopsis (Panhuis et al, 2017).…”

Gross morphological and surface ultrastructural investigation on the gills of the European barracuda Sphyraena sphyraena

“…The most characteristic feature of the European barracuda gills is the lacking the gill rakers. Also, Mistri, Verma, Kumari, Mittal, and Mittal (2016) observed the absence of the rakers in angler catfish chaca chaca and the lacking of these rakers permits smooth swallowing of the captured preys without any hindrance. Meanwhile, many authors recorded presence of gill rakers with a different appearance in a wide variety of fish with different feeding habits; The spaces between the gill rakers determine the size of the swallowed food items concerning the feeding habits of different fish species; the narrow spacing correlated to the small sized preys that will be eaten (Magnuson & Heitz, 1971;O'Brien, 1987).…”

“…The most characteristic feature of the European barracuda gills is the lacking the gill rakers. Also, Mistri, Verma, Kumari, Mittal, and Mittal (2016) observed the absence of the rakers in angler catfish chaca chaca and the lacking of these rakers permits smooth swallowing of the captured preys without any hindrance. Meanwhile, many authors recorded presence of gill rakers with a different appearance in a wide variety of fish with different feeding habits; Alsafy (2013) in sea bream and sea bass, Elsheikh (2013) in Oreochromis niloticus , Chrysichthys auratus , and Clarias gariepinus , Khalaf‐Allah, Azab, and Mohamed (2016) in Sparus aurata , Diplodus noct , Rhapdosargus haffara , and Boops boops , Abumandour and El‐Bakary (2017) in grey gurnard fish and striped mullet fish, Märss, Wilson, Saat, and Špilev (2017) in European plaice, European flounder, and turbot and Hanafy (2020) in European hake, Bassuoni (2021) in Bagrus bayad.…”