Terrestrial capture of prey by the reedfish, a model species for stem tetrapods

Abstract

Due to morphological resemblance, polypterid fishes are used as extant analogues of Late Devonian lobe‐finned sarcopterygians to identify the features that allowed the evolution of a terrestrial lifestyle in early tetrapods. Previous studies using polypterids showed how terrestrial locomotion capacity can develop, and how air ventilation for breathing was possible in extinct tetrapodomorphs. Interestingly, one polypterid species, the reedfish Erpetoichthys calabaricus, has been noted being capable of capturing prey on land. We now identified the mechanism of terrestrial prey‐capture in reedfish. We showed that this species uses a lifted trunk and downward inclined head to capture ground‐based prey, remarkably similar to the mechanism described earlier for eel‐catfish. Reedfish similarly use the ground support and flexibility of their elongated body to realize the trunk elevation and dorsoventral flexion of the anterior trunk region, without a role for the pectoral fins. However, curving of the body to lift the trunk may not have been an option for the Devonian tetrapodomorphs as they are significantly less elongated than reedfish and eel‐catfish. This would imply that, in contrast to the eel‐like extant species, evolution of the capacity to capture prey on land in early tetrapods may be linked to the evolution of the pectoral system to lift the anterior part of the body.

The feeding system of Tiktaalik roseae : an intermediate between suction feeding and biting

“…Polypterids, including multiple species of Polypterus and reedfish ( Erpetoichthys calabaricus ), are frequently used modern analogs for studies into tetrapodomorph feeding mechanisms ( 5 , 44 , 45 ). They possess dorsoventrally compressed cranial anatomy ( 5 , 45 ), similar to T. roseae , and the articulation of the hyomandibula is oriented posteriorly ( Fig.…”

“…The snout and jaws are elongate ( Fig. 3 A ), with no suggestion of fleshy lobes, such as found in polypterids ( 44 ), to occlude the corners of the mouth and facilitate forceful, directed suction ( 1 , 48 – 50 ). Instead, the tooth row extends posteriorly lateral to the adductor chamber ( Fig.…”

Aquatic–terrestrial transitions of feeding systems in vertebrates: a mechanical perspective

“…3, Table 1). This behavior has been described for the eel-catfish Channallabes apus (Van Wassenbergh et al, 2006;Van Wassenbergh, 2013) and for the reedfish Erpethoichthys calabaricus (Van Wassenbergh et al, 2017). This feeding behavior is more versatile than that of the European catfish, as the ground surface can be scanned for smaller food by left and right yawing of the head (with help of the chemotactile barbels of C. apus) (Van Wassenbergh et al, 2006).…”

“…However, most fish that feed on food lying on the substrate in the aquatic environment will tend to incline the entire body to steeper angles, e.g. cichlids (Rupp and Hulsey, 2014), eels (Mehta and Wainwright, 2007a,b), catfish (Van Wassenbergh et al, 2009a) and reedfish (Van Wassenbergh et al, 2017). As these postures are impossible outside water, not all aquatic solutions to benthic feeding facilitate the transition to terrestrial feeding.…”

“…4D-F) (Michel et al, 2015b), and it might well be that some as-yet-unknown stem tetrapods used a convergent mechanism (Michel et al, 2016). Option ii, dragging prey back to the water, might be the easiest way to circumvent the problem of transport as well as swallowing prey captured on land, and is used in a variety of aquatic and amphibious vertebrates that occasionally strike prey on land (Lopez and Lopez, 1985;Miller and Larsen, 1990;Peddemors and Thompson, 1994;Bels et al, 1997;Summers et al, 1998;Werth, 2000;Stayton, 2011;Heiss et al, 2013aHeiss et al, , 2015Michel et al, 2015a;Natchev et al, 2015;Van Wassenbergh et al, 2017). Option iii is found in crocodilians de Vree, 1992, 2000) and varanid lizards (Smith, 1982(Smith, , 1986, where food is literally thrown through the mouth (Smith, 1982) by fast dorsal head rotation in concert with coordinated gape opening to accelerate prey backwards (Smith, 1982(Smith, , 1986de Vree, 1992, 2000).…”