Elephants evolved strategies reducing the biomechanical complexity of their trunk

Dagenais, Paule; Hensman, Sean; Haechler, Valérie; Milinkovitch, Michel C.

doi:10.1016/j.cub.2021.08.029

Cited by 37 publications

(45 citation statements)

References 46 publications

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“…For example, one of the facial muscles, M. naso-labialis, extends over the whole length of the trunk in elephants, likely to manipulate it. 16,18 Morphological modification of several facial muscles related to trunk manipulation have been reported in the tapirs as well. 19 The anatomical components and kinetics of rostral appendages have been studied so far in elephants, 16,18,[20][21][22] tapir, 19 and saiga.…”

Section: Introductionmentioning

confidence: 96%

“…The ability to manipulate these appendages probably evolved through modifications of the facial muscles. For example, one of the facial muscles, M. naso‐labialis, extends over the whole length of the trunk in elephants, likely to manipulate it 16,18 . Morphological modification of several facial muscles related to trunk manipulation have been reported in the tapirs as well 19 .…”

Section: Introductionmentioning

confidence: 99%

“…Morphological modification of several facial muscles related to trunk manipulation have been reported in the tapirs as well 19 . The anatomical components and kinetics of rostral appendages have been studied so far in elephants, 16,18,20‐22 tapir, 19 and saiga 23 . However, because only a few rostral appendages have been examined and embryological data concerning how different rostrum are formed is lacking, the evolutionary relationship between mammalian facial muscles and movable rostral appendages remains largely unexplored.…”

Section: Introductionmentioning

confidence: 99%

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Facial muscle modification associated with chiropteran noseleaf development: Insights into the developmental basis of a movable rostral appendage in mammals

Usui

Khannoon

Tokita

2022

Developmental Dynamics

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Background: Mammal evolution has generated diverse craniofacial morphologies, including remarkable movable rostral appendages. However, the muscular and skeletal architecture providing the mobility of these appendages remains largely unexplored. Here, we focus on chiropteran noseleaves and compare the three-dimensional internal morphology of late-stage embryos between the greater horseshoe bat Rhinolophus ferrumequinum, which possesses a noseleaf, and the Asian bent-winged bat Miniopterus fuliginosus and Egyptian fruit bat Rousettus aegyptiacus, which do not. We also assess earlier stage cell proliferation within the rostrum to elucidate cellular mechanisms underlying noseleaf-associated morphological modifications. Results: The musculus maxillolabialis inserted into proximal vibrissae follicles in M fuliginosus and R aegyptiacus embryos but instead inserted into the horseshoe plate in R ferrumequinum. This modification suggests that the M maxillolabialis has adapted to controlling the noseleaf rather than vibrissae in rhinolophid bats. Our cellular analysis showed higher cell proliferation within the maxillary and frontonasal processes of St. 14 embryos in R ferrumequinum compared to M fuliginosus and R aegyptiacus, suggesting that the spatial alteration of noseleaf-associated muscle is derived from changes in facial morphogenesis that occur by St. 14. Conclusion:This is the first study clarifying the morphological and cellular bases underlying the development of mammalian rostral appendages.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Facial muscle modification associated with chiropteran noseleaf development: Insights into the developmental basis of a movable rostral appendage in mammals

Usui

Khannoon

Tokita

2022

Developmental Dynamics

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“…Grasping techniques, mainly including the morphological and kinematic aspects, are well studied in muscular hydrostats ( Grasso, 2008 ; Ritter & Nishikawa, 1995 ). Elephant grasping has also received increasing attention, especially the techniques that involve the distal part of the trunk ( Dagenais et al, 2021 ; Schulz et al, 2021 ). Although the most commonly used grasping technique in muscular hydrostats is coiling around the item, elephant trunk tips can also engage in pinch grasping ( Rasmussen & Munger, 1996 ; Wu et al, 2018 ) as can chameleon tongues ( Herrel et al, 2000 ).…”

Section: Introductionmentioning

confidence: 99%

The relationship between distal trunk morphology and object grasping in the African savannah elephant (Loxodonta africana)

Soppelsa

Pouydebat

Lefeuvre

et al. 2022

PeerJ

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Background During reach-to-grasp movements, the human hand is preshaped depending on the properties of the object. Preshaping may result from learning, morphology, or motor control variability and can confer a selective advantage on that individual or species. This preshaping ability is known in several mammals (i.e., primates, carnivores and rodents). However, apart from the tongue preshaping of lizards and chameleons, little is known about preshaping of other grasping appendages. In particular, the elephant trunk, a muscular hydrostat, has impressive grasping skills and thus is commonly called a hand. Data on elephant trunk grasping strategies are scarce, and nothing is known about whether elephants preshape their trunk tip according to the properties of their food. Methods To determine the influence of food sizes and shapes on the form of the trunk tip, we investigated the morphology of the distal part of the trunk during grasping movements. The influence of food item form on trunk tip shape was quantified in six female African savannah elephants (Loxodonta africana). Three food item types were presented to the elephants (elongated, flat, and cubic), as well as three different sizes of cubic items. A total of 107 ± 10 grips per individual were video recorded, and the related trunk tip shapes were recorded with a 2D geometric morphometric approach. Results Half of the individuals adjusted the shape of the distal part of their trunk according to the object type. Of the three elephants that did not preshape their trunk tip, one was blind and another was subadult. Discussion and perspectives We found that elephants preshaped their trunk tip, similar to the preshaping of other species’ hands or paws during reach-to-grasp movements. This preshaping may be influenced by visual feedback and individual learning. To confirm these results, this study could be replicated with a larger sample of elephants.

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“…Indeed, we surmise that agents are intelligent when they are found in large regions of action-state space, by either visiting new spatial locations or by generating richer or unexpected behaviors, not when they maximize external reward. Our theory provides a rational account of exploratory and curiosity-driven behavior where the problem of defining an external reward goal vanishes, and captures the variability of perception and behavior [29][30][31][32][33][34] by taking it as principle.…”

Section: Introductionmentioning

confidence: 99%

Seeking entropy: complex behavior from intrinsic motivation to occupy action-state path space

Ramírez-Ruiz¹,

Grytskyy²,

Moreno‐Bote³

2022

Preprint

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Intrinsic motivation generates behaviors that do not necessarily lead to immediate reward, but help exploration and learning. Here we show that agents having the sole goal of maximizing occupancy of future actions and states, that is, moving and exploring on the long term, are capable of complex behavior without any reference to external rewards. We find that action-state path entropy is the only measure consistent with additivity and other intuitive properties of expected future action-state path occupancy. We provide analytical expressions that relate the optimal policy with the optimal state-value function, from where we prove uniqueness of the solution of the associated Bellman equation and convergence of our algorithm to the optimal state-value function. Using discrete and continuous state tasks, we show that 'dancing', hide-and-seek and a basic form of altruistic behavior naturally result from entropy seeking without external rewards. Intrinsically motivated agents can objectively determine what states constitute rewards, exploiting them to ultimately maximize action-state path entropy.

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Elephants evolved strategies reducing the biomechanical complexity of their trunk

Cited by 37 publications

References 46 publications

Facial muscle modification associated with chiropteran noseleaf development: Insights into the developmental basis of a movable rostral appendage in mammals

Facial muscle modification associated with chiropteran noseleaf development: Insights into the developmental basis of a movable rostral appendage in mammals

The relationship between distal trunk morphology and object grasping in the African savannah elephant (Loxodonta africana)

Seeking entropy: complex behavior from intrinsic motivation to occupy action-state path space

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