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Feeding behaviour in a 'basal' tortoise provides insights on the transitional feeding mode at the dawn of modern land turtle evolution.

Natchev N, Tzankov N, Werneburg I, Heiss E - PeerJ (2015)

Bottom Line: In M. emys, the hyolingual complex remained retracted during all food uptake sequences, but the food transport was entirely lingual based.The kinematical profiles significantly differed from those described for other tortoises and from those proposed from the general models on the function of the feeding systems in lower tetrapods.We conclude that the feeding behaviour of M. emys might reflect a remnant of the primordial condition expected in the aquatic ancestor of the tortoises.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Integrative Zoology, Vienna University , Vienna , Austria ; Faculty of Natural Science, Shumen University , Shumen , Bulgaria.

ABSTRACT
Almost all extant testudinids are highly associated with terrestrial habitats and the few tortoises with high affinity to aquatic environments are found within the genus Manouria. Manouria belongs to a clade which forms a sister taxon to all remaining tortoises and is suitable as a model for studying evolutionary transitions within modern turtles. We analysed the feeding behaviour of Manouria emys and due to its phylogenetic position, we hypothesise that the species might have retained some ancestral features associated with an aquatic lifestyle. We tested whether M. emys is able to feed both in aquatic and terrestrial environments. In fact, M. emys repetitively tried to reach submerged food items in water, but always failed to grasp them-no suction feeding mechanism was applied. When feeding on land, M. emys showed another peculiar behaviour; it grasped food items by its jaws-a behaviour typical for aquatic or semiaquatic turtles-and not by the tongue as generally accepted as the typical feeding mode in all tortoises studied so far. In M. emys, the hyolingual complex remained retracted during all food uptake sequences, but the food transport was entirely lingual based. The kinematical profiles significantly differed from those described for other tortoises and from those proposed from the general models on the function of the feeding systems in lower tetrapods. We conclude that the feeding behaviour of M. emys might reflect a remnant of the primordial condition expected in the aquatic ancestor of the tortoises.

No MeSH data available.


Selected frames and graphics (based on high-speed video with 250 frs) showing the movements of jaws, hyoid, and head during attempts of aquatic food uptake in Manouria emys.(A) start of the gape cycle; (B) end of jaw opening; (C) maximum gape end; (D) fast closure end; note the lack of movement of the hyoid complex during the whole cycle; grid 10 × 10 mm. Abbreviations in Appendix S1.
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fig-4: Selected frames and graphics (based on high-speed video with 250 frs) showing the movements of jaws, hyoid, and head during attempts of aquatic food uptake in Manouria emys.(A) start of the gape cycle; (B) end of jaw opening; (C) maximum gape end; (D) fast closure end; note the lack of movement of the hyoid complex during the whole cycle; grid 10 × 10 mm. Abbreviations in Appendix S1.

Mentions: When trying to feed under water (Fig. 4 and at http://figshare.com/s/5d9e23c8f4ec11e49cb306ec4b8d1f61), M. emys submerged its head under the water level and protruded the gaping jaws toward the food item. The gape cycle was newer split in slow and fast jaw open phases. The tongue tip was not visible from the lateral aspect and the hyolingual complex did not protract prior reaching peak gape. No retraction of the hyoid complex was detected prior jaw closure. The gape cycle duration exceeded one and a half seconds and was 1.94 ± 0.36 s (mean ± SD). Despite the unsuccessful attempts, the turtles repeatedly tried to catch the submerged food. In several events, we were able to detect that the food item was carried away by the bow wave induced by jaw closing.


Feeding behaviour in a 'basal' tortoise provides insights on the transitional feeding mode at the dawn of modern land turtle evolution.

Natchev N, Tzankov N, Werneburg I, Heiss E - PeerJ (2015)

Selected frames and graphics (based on high-speed video with 250 frs) showing the movements of jaws, hyoid, and head during attempts of aquatic food uptake in Manouria emys.(A) start of the gape cycle; (B) end of jaw opening; (C) maximum gape end; (D) fast closure end; note the lack of movement of the hyoid complex during the whole cycle; grid 10 × 10 mm. Abbreviations in Appendix S1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4558077&req=5

fig-4: Selected frames and graphics (based on high-speed video with 250 frs) showing the movements of jaws, hyoid, and head during attempts of aquatic food uptake in Manouria emys.(A) start of the gape cycle; (B) end of jaw opening; (C) maximum gape end; (D) fast closure end; note the lack of movement of the hyoid complex during the whole cycle; grid 10 × 10 mm. Abbreviations in Appendix S1.
Mentions: When trying to feed under water (Fig. 4 and at http://figshare.com/s/5d9e23c8f4ec11e49cb306ec4b8d1f61), M. emys submerged its head under the water level and protruded the gaping jaws toward the food item. The gape cycle was newer split in slow and fast jaw open phases. The tongue tip was not visible from the lateral aspect and the hyolingual complex did not protract prior reaching peak gape. No retraction of the hyoid complex was detected prior jaw closure. The gape cycle duration exceeded one and a half seconds and was 1.94 ± 0.36 s (mean ± SD). Despite the unsuccessful attempts, the turtles repeatedly tried to catch the submerged food. In several events, we were able to detect that the food item was carried away by the bow wave induced by jaw closing.

Bottom Line: In M. emys, the hyolingual complex remained retracted during all food uptake sequences, but the food transport was entirely lingual based.The kinematical profiles significantly differed from those described for other tortoises and from those proposed from the general models on the function of the feeding systems in lower tetrapods.We conclude that the feeding behaviour of M. emys might reflect a remnant of the primordial condition expected in the aquatic ancestor of the tortoises.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Integrative Zoology, Vienna University , Vienna , Austria ; Faculty of Natural Science, Shumen University , Shumen , Bulgaria.

ABSTRACT
Almost all extant testudinids are highly associated with terrestrial habitats and the few tortoises with high affinity to aquatic environments are found within the genus Manouria. Manouria belongs to a clade which forms a sister taxon to all remaining tortoises and is suitable as a model for studying evolutionary transitions within modern turtles. We analysed the feeding behaviour of Manouria emys and due to its phylogenetic position, we hypothesise that the species might have retained some ancestral features associated with an aquatic lifestyle. We tested whether M. emys is able to feed both in aquatic and terrestrial environments. In fact, M. emys repetitively tried to reach submerged food items in water, but always failed to grasp them-no suction feeding mechanism was applied. When feeding on land, M. emys showed another peculiar behaviour; it grasped food items by its jaws-a behaviour typical for aquatic or semiaquatic turtles-and not by the tongue as generally accepted as the typical feeding mode in all tortoises studied so far. In M. emys, the hyolingual complex remained retracted during all food uptake sequences, but the food transport was entirely lingual based. The kinematical profiles significantly differed from those described for other tortoises and from those proposed from the general models on the function of the feeding systems in lower tetrapods. We conclude that the feeding behaviour of M. emys might reflect a remnant of the primordial condition expected in the aquatic ancestor of the tortoises.

No MeSH data available.