Distinctive anatomical features of the branchial basket in four carapidae species (ophidiiformi, paracanthopterygii).

The present study focuses on the branchial basket in four Carapidae species: Carapus acus, Encheliophis boraborensis, Encheliophis homei and Encheliophis gracilis. The aim is to highlight the skeletal and muscular features of the branchial basket, especially those that are believed to be related to their way of life and/or to be linked to the presence of primary sound-producing muscles. The space occupied by the primary sound-producing muscles between the neurocranium and the branchial basket gives rise to distinctive skeletal and muscular features. They prevent the 1st pharyngobranchials from becoming attached to the neurocranium in the normal way. These do not seem to play any role in the suspension of the upper pharyngeal jaws, as it is usually the case in teleosteans. The 1st epibranchials are separated from the 2nd pharyngobranchials. Ossified interarcual elements jointed to the 2nd pharyngobranchials and 1st epibranchials are found in the position usually occupied by the latter. The presence of primary sound-producing muscles gives rise to the need for the reorganisation of the musculature which is seen in particular with regards to the levatores branchiales. These are not found on the neurocranium but on the hyomandibular. The general skeletal and muscular data and the observations of the stomach contents suggest that the action of the branchial basket is restricted to carrying food in Carapus acus, Encheliophis boraborensis and Encheliophis homei, whereas it could also play a role in the work of cutting up soft food in Encheliophis gracilis.