The trunk ( neulat. Proboscis from Greek προβοσκίς) in the narrower sense represents an organ that arose from the fusion of the nose with the upper lip , which led to the formation of an elongated, fleshy, muscular tube in elephants and tapirs . In a broader sense, the term denotes the more or less similar elongated mouth and nose sections in many other animals. The term proboscis is mainly used in the field of mammals and invertebrates . A real trunk like that of elephants and tapirs is characterized by a high degree of flexibility with a wide range of uses, whereby in addition to breathing, active food intake is of great importance. The other trunk-like formations are mostly limited in their functionality and in many cases are not directly related to nutrition.
Proboscis in the strict sense in mammals
Function of the real trunk
With the elephant and its narrower and wider relationship ( Russell animals or Proboscidea) connected Proboscis label thus includes a nose structure which is also used in addition to their primary function as an olfactory organ primarily as a gripping hand for ingestion. In addition, it serves as a suction and pressure pump when drinking or sand bathing, as a tool for personal hygiene, as a means of transport, as a weapon , as a snorkel or for social interaction between individual individuals (for example by looping around each other's trunk) and for communication (for example when threatening gestures or claims to dominance). In contrast to the high functionality of the elephant's trunk, the short trunk of the tapir is less versatile in addition to breathing and eating. The size of the objects that can be used with the trunk is very limited. However, as with the elephants, it is used for social communication (such as flehmen ) or as a snorkel.
Functionally real probes are only found in the elephants (Elephantidae) and tapirs (Tapiridae) within the group of mammals . The real trunk means a fusion of the nose with the upper lip and the formation of an elongated, fleshy tube with the nostrils at the lower, free end and a missing bony or cartilaginous substructure. It mainly consists of muscles , nerve tracts , connective tissue , blood and lymph vessels as well as skin and hair. Cartilage tissue is only found on the skull and, among other things, separates the two nostrils. The high flexibility and mobility of the trunk is ensured by a large number of longitudinal and transverse as well as helical or oblique muscle strands. The number of individual muscles in elephants is estimated to be around 150,000.
In the evolutionary emergence of highly functional trunk of elephants and tapirs occurred in the course of evolutionary history in addition to the changes in the soft tissue morphology (nose and upper lip) and numerous skeletal anatomical modifications to the skull. This mainly concerns an extreme reduction in the area of the nasal bone , which only exists as a short process. As a result, the nostrils are sometimes massively enlarged. In both cases, the nasal bone is also strongly offset backwards on the skull, so that in the tapirs the interior of the nose extends above the orbit and takes up to 75% of the length of the skull, of which the nasal vestibule takes up three quarters. Other bones of the facial skull, such as the upper jaw or the intermaxillary bones in elephants and tapirs, on the other hand, became more massive and act as a base for the muscles of the trunk. The mandibular bone has completely lost contact with the nasal bone, in elephants it forms the massive alveoli of the tusks. In the elephants as well as in the tapirs, these changes are clearly recognizable in the skull structure, the reduction of the upper facial skull was necessary so that the extensive trunk muscles had enough space. However, the remodeling of the elephant's skull is much more advanced and also affects large areas of the upper and lower jaw and the teeth. The front set of teeth was significantly reduced, since the current and numerous extinct representatives no longer have any incisors apart from the tusks , whose function was lost through the primary ingestion of food with the trunk. The tapirs, on the other hand, still have a complete front set of teeth, which is functionally somewhat restructured by small incisors (except for the upper outer teeth, which resemble a canine tooth ).
Evolution of the trunk
The development of a trunk in both elephants and tapirs began relatively early in tribal history . In elephants, it is associated with increasing body size, along with the formation of long, columnar legs, a shortening of the neck and thus a very high position of the skull. The trunk was created to bridge the distance between head and floor and is therefore an organ that is essential for survival. Probably the early representatives of the proboscis of the Eocene such as Numidotherium or Barytherium had proboscis, although this is usually only indicated by the structure and high position of the nasal bone. In other early proboscis such as Moeritherium , however, no proboscis is assumed. The development took place in stages and began with a tapir-like, short trunk, which is partially postulated for the huge Deinotherium . It is not yet known whether the trunk of today's elephants developed only once or whether it developed independently several times in the various lines of the trunk animals. In the case of the tapirs, the proboscis also developed from the group of the Tapiroidea as early as the Eocene period . Very early forms such as Heptodon or Hyrachyus still had a small, protruding nasal cavity that was more reminiscent of horses. In other representatives such as Helaletes , the interior of the nose was drawn far back and ended above the middle premolars . However, the nasal bone was still very long, which speaks against a clear trunk, as the bone embedded in it would have severely restricted its mobility. In contrast, Colodon from the transition to the Oligocene already showed a greatly reduced nasal bone, which makes a proboscis very likely. Thus, the trunk of both elephants and tapirs developed around 30 million years ago, but this development continued more profoundly in the ancestors of the elephants.
The well-known noticeable skeletal anatomical changes associated with the formation of a trunk can be used as a comparison for extinct groups of mammals. For example, some groups that no longer exist today have similar redesigns of the skull that suggest a real trunk. These include the Eocene to Oligocene Amynodontidae from the closer relationship of the rhinos , whose skull structure of the late forms such as Amynodontopsis and Cadurcodon with the strongly regressed nasal bone is reminiscent of that of the tapirs, just as both groups have the same dentition structure. The Astrapotheria , which belong to the South American ungulates and lived from the Eocene to the Miocene , can be seen as a possible example of convergent evolution to the proboscis . As with the giant Astrapotherium and Granastrapotherium, there was not only an extreme regression of the nasal bone, but also the complete loss of the incisors and the development of the canine teeth into pronounced tusks that were up to 1 m long. In addition, the upper jaw had shrunk considerably in length compared to the lower jaw, so that food was only possible through an additional organ such as a trunk. Traces of wear on the tusks, which resemble those of today's elephants and point to an effective cooperation between tusk and trunk, suggest that the trunk of the Astrapotheria was at least so long that it could reach the tips of the tusks. On the other hand, a proboscis is assumed for the Pleistocene Macrauchenia from the group of Litopterna due to the design of the front skull.
The word proboscis used in scientific language originally comes from the Greek ( προβοσκίς , proboskís ) and is generally translated as "trunk". The Greek prefix προ- ( pro- ) means something like “to be in front of something”, the root of the word refers to the Greek words βοσκή ( boskḗ “fodder”, “pasture”) and βόσκειν ( bóskein “pasture”, “to feed "Or βόσκω bósko " I graze "). Thus, the trunk is causally related to food intake (in some cases, Proboscis is simply translated as "in front of the mouth"). The word proboskís was already used by Aristotle in the 4th century BC. Used in relation to the elephant trunk, some scientists believe that it is much older. Aristotle described the trunk in great detail in his works De partibus animalium and Historia animalium and noted that elephants would use it like a hand. According to him, they use the proboscis to grab food and then put it in the mouth. Furthermore, with its help they would drink, touch other objects or wrap their trunk around them or transport something. In addition, Aristotle was aware that the trunk has no bones and that it owes its high flexibility to this circumstance, and that elephants without a trunk cannot eat any food.
In zoo animal husbandry, the trunk hole is sometimes used as a technical aid for feeding.
Trunk-like formations in the broader sense in mammals
In a broader sense, the term proboscis often denotes elongated or enlarged noses in many other mammals, which, strictly speaking, do not represent real proboscis. These include the proboscis monkeys ( Nasalis ), coatis ( Nasua ), hedgehogs (Erinaceidae), shrews (Soricidae), elephants (Macroscelidea), tenreks (Tenrecidae), opossums (Caenolestidae) coati (Peramelemorphia) or some representatives of the ungulates (Artiodemorphia) (Artiodemorphia) , for example pigs (Suidae), saiga antelopes ( Saiga ) or dikdiks ( Madoqua ). In many cases, however, no serious anatomical remodeling of the skull took place here, rather changes in the soft tissue occurred for the most part. The rostrum of the elephants is compact with an elongated nasal bone, the extended nose is mainly made of cartilage, the upper lip is separate and is not fused with the nose. Although the nose is used to probe the search for food and is extremely mobile as an olfactory organ, food is ultimately consumed with the elongated tongue typical of insectivores. In numerous cloven-hoofed animals, the nasal bones are significantly reduced or offset backwards. In the Saiga, the inside of the nose is also extremely enlarged and the intermaxillary bone is redesigned in such a way that it has a large, muscular nose that partially hangs over the upper lip. However, it represents a special adaptation for filtering dust in dry landscapes. The situation is similar with the extended nose of the elk , which overhangs in front , but only occurs in adult individuals. Their direct function is unknown; it is partly speculated that this is an adaptation that enables the feeding of aquatic plants , whereby moose dive up to 5 m deep to acquire them and remain under water for about a minute or more.
In principle, none of the special nasal formations in mammals achieve the high functionality of the trunk of the elephant or the tapir. They also are not related to direct food intake in combination, but make respective adjustments represent the ecological circumstances. Aside from the fact that many of the structures often referred to as "trunk" ( proboscis are called), proposals were made for a more nuanced distinction. So should according to some scholars pure extensions of the nose, which involve but not the upper lip and depending on the species or group a different, but mostly limited function possess the nostrils such as in the elephant-shrews, the Saiga and the moose, as Prorhiscis referred become (Greek ῥίς ( rhīs ) for "nose").
Further trunk-like formations in the animal kingdom
Neither birds nor reptiles , with the exception of some softshell turtles , have pronounced trunk-like structures. With some fish , however, extensions of the nose or stretching of the snout are known, which are sometimes referred to as trunk-like. These include long-nosed chimera (Rhinochimaera), plownose chimera (Callorhinchidae), paddlefish ( Polyodon ), spiny eel (Mastacembelidae) or Nile pike (Mormyridae).
Furthermore, in some invertebrates the mouthparts redesigned such that is often spoken of trunks, such as the proboscis of butterflies , of the absorption of the floral nectar or (in a few species) of the blood of warm-blooded creatures, is necessary also for scribing flowers and is drawn in or rolled up when idle. In addition, the proboscis of flies and bugs is a suction organ that can also be used to prick surfaces if necessary. In weevils and a few other beetle families , the extension of the head is called a proboscis, but the mouthparts sit at the tip of the immobile proboscis.
Many marine snails , especially carnivorous ones, have a long, extendable proboscis, which they use to get to the soft tissues of their prey through gaps in the shell or drilled holes ( moon snails , prickly snails ) or to dissolve the shell with acid ( barrel snails ). Some parasitize fish with the help of their very long proboscis, such as the dwarf conch of the genus Colubraria or the snails of the genus Cancellaria .
- Antoni V. Milewski and Ellen S. Dierenfeld: Structural and functional comparison of the proboscis between tapirs and other extant and extinct vertebrates. Integrative Zoology 8, 2013, pp. 84-94.
- Lawrence M. Witmer, Scott D. Sampson and Nikos Solounias: The proboscis of tapirs (Mammalia: Perissodactyla): a case study in novel narial anatomy. Journal of Zoology 249, 1999, pp. 249-267.
- Jeheskel Shoshani: Skeletal and basic anatomical features of elephants. In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and palaeoecology of the Elephants and their relatives. Oxford, New York, Tokyo, 1996, pp. 9-20.
- GN Markov, N. Spassov and V. Simeonovski: A reconstruction of the facial morphology and feeding behavior of the deinotheres. In: G. Cavarretta et al. (Eds.): The World of Elephants - International Congress. Consiglio Nazionale delle Ricerche. Rome, 2001, pp. 652-655.
- Jehezekel Shoshani, Robert M. West, Nicholas Court, Robert JG Savage, John M. Harris: The earliest proboscideans: general plan, taxonomy, and Palaeoecology. In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and Palaeoecology of the Elephants and their Relatives. Oxford, New York, Tokyo, 1996, pp. 57-75.
- Robert M. Schoch: A review of the Tapiroids. In: Donald R. Prothero and Robert M. Schoch (Eds.): The evolution of Perissodactyls. New York and Oxford, 1989, pp. 298-320.
- Leonard B. Radinsky: Origin and Early Evolution of North American Tapiroidea. Peabody Museum of Natural History Yale University Bulletin 17, 1963, pp. 1-106.
- William P. Wall: Cranial evidence for a proboscis in Cadurcodon and a review of snout structure in the family Amynodontidae (Perissodactyla, Rhinocerotoidea). Journal of Paleontology 54 (5), pp. 968-977.
- Steven J. Johnson and Richard H. Madden: Uruguaytheriine astrapotheres of tropical South America. In: Richard F. Kay, Richard H. Madden, Richard L. Cifelli, and John J. Flynn (Eds.): Vertebrate Paleontology in the Neotropics. The Miocene Fauna of La Venta, Colombia. Smithsonian Institution Press, Washington, 1997, pp. 355-382.
- MC Vallejo-Pareja, JD Carrillo, JW Moreno-Bernal, M. Pardo-Jaramillo, DF Rodriguez-Gonzalez and J. Muñoz-Duran: Hilarcotherium castanedaii, gen. Et sp. nov., a new Miocene astrapothere (Mammalia, Astrapotheriidae) from the Upper Magdalena Valley, Colombia. Journal of Vertebrate Paleontology 2015, doi : 10.1080 / 02724634.2014.903960 .
- Bruce J. MacFadden and Bruce J. Shockey: Ancient feeding ecology and niche differentiation of Pleistocene mammalian herbivores from Tarija, Bolivia: morphological and isotopic evidence. Paleobiology 23, 1997, pp. 77-100.
- Jehezekel Shoshani and Pascal Tassy: Order Proboscidea - Elephants. In: Jonathan Kingdon, David Happold, Michael Hoffmann, Thomas Butynski, Meredith Happold, Jan Kalina (Eds.): Mammals of Africa Volume I. Introductory Chapters and Afrotheria. Bloomsbury, London, 2013, pp. 173-175.
- Wilhelm Pape: Concise dictionary of the Greek language. Braunschweig, 1914 (  ).
- Merlin Peris: Aristotle's Notices on the Elephant. Gajah 22, 2003, pp. 71-75.
- Jean E. Kratzing and Peter F. Woodall: The rostral nasal anatomy of two elephant shrews. Journal of Anatomy 157, 1988, pp. 135-143.
- Andrew B. Clifford and Lawrence M. Witmer: Case studies in novel narial anatomy: 3. Structure and function of the nasal cavity of saiga (Artiodactyla: Bovidae: Saiga tatarica). Journal of Zoology 264, 2004, pp. 217-230.
- Andrew B. Clifford and Lawrence M. Witmer: Case studies in novel narial anatomy: 2. The enigmatic nose of moose (Artiodactyla: Cervidae: Alces alces). Journal of Zoology 262, 2004, pp. 339-360.
- Harald W. Krenn and Horst Aspöck: Form, function and evolution of the mouthparts of blood-feeding Arthropoda. Arthropod Structure & Development 41, 2012, pp. 101–118.
- Jessica I. Grant, Dylan M. Djani and Matthew S. Lehnert: Functionality of a reduced proboscis: fluid uptake by Phigalia strigataria (Minot) (Geometridae: Ennominae). Journal of the Lepidopterists' Society 66 (4), 2012, pp. 211-215.
- Philippe Bouchet and Doug Perrine: More gastropods feeding at night on parrotfishes. Bulletin of Marine Science 59, 1996, pp. 224-228.
- Marco Oliverio and Maria Vittoria Modica: Relationships of the haematophagous marine snail Colubraria (Rachiglossa, Colubrariidae), within the neogastropod phylogenetic framework. Zoological Journal of the Linnean Society 158, 2009, pp. 779-800.
- JB O'Sullivan, RR McConnaughey and ME Huber: A blood-sucking snail: the Cooper's nutmeg, Cancellaria cooperi Gabb, parasitises the California electric ray, Torpedo californica Ayres. Biological Bulletin 172, 1997, pp. 362-366.