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Observations of the reduction of external gill filaments during larval development in Heterotis niloticus

Publication Date
  • Heterotis Niloticus
  • Larval Development
  • External Gill Resorption
  • Life Sciences :: Zoology [F14]
  • Sciences Du Vivant :: Zoologie [F14]

Abstract Belg. J. Zool., 137 (2) : 247-249 July 2007 Observations of the reduction of external gill filaments during larval development in Heterotis niloticus Michaël Hermens1, Mamina Daffé2 & Pierre Vandewalle1 1 Université de Liège, Laboratoire de Morphologie Fonctionnelle et Évolutive. Institut de Chimie, B6 Sart Timan. B-4000 Liège, Belgique. 2 Université Cheikh Anta Diop, Institut Universitaire de Pêche et d'Aquaculture. UCAD II, Bat. Pédagogie-rez de chaussée, B- 45784 Dakar, Sénégal. Corresponding author: [email protected] KEY WORDS : Heterotis niloticus, external gills, larval development, resorptions. The arowana Heterotis niloticus (Cuvier, 1829) is dis- tributed in the Sahelo-Sudanese freshwaters of West Africa (DAGET & DURAND, 1981; PAUGY, 2003) (1) (2). Until recently included within Osteoglossidae in the sub- family Heterotidinae, this species is now considered to belong to the Arapaimidae family, along with the south american pirarucú Arapaima gigas (Schinz) (FERRARIS, 2003) (3). Among other peculiarities, H. niloticus pos- sesses externally projecting gill filaments at the earliest larval stages (DAGET, 1957) (4). These gills have an endo- dermal origin and seem to have a purely respiratory func- tion. Although the presence of external gills has been reported in most major groups of aquatic anamniotes, they can be observed in teleosts in only one other species, Gymnarchus niloticus Cuvier (BUDGETT, 1901; ASSHETON, 1907) (5) (6). In Elasmobranchs, external fila- ments which float in the albuminous fluid are present dur- ing the embryonic phase, before the formation of the yolk sac. They appear to have a respiration as well as a food absorption function (BERTIN, 1958; PELPSTER & BEMIS, 1992) (7) (8). Smaller external gill filaments have been reported in Chondrosteans larvae (BERTIN, 1958; GIS- BERT, 1999) (7) (9). Analogous gills are present in juve- nile Polypterids and in the larvae of the African and South American lungfishes (BERTIN, 1

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