{"id":37393,"date":"2019-10-31T22:17:23","date_gmt":"2019-10-31T19:17:23","guid":{"rendered":"https:\/\/prohoster.info\/blog\/zubnaya-feya-tut-ne-rabotaet-struktura-emali-zubov-krokodilov-i-ih-doistoricheskih-predkov\/"},"modified":"2019-10-31T22:17:23","modified_gmt":"2019-10-31T19:17:23","slug":"zubnaya-feya-tut-ne-rabotaet-struktura-emali-zubov-krokodilov-i-ih-doistoricheskih-predkov","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/zubnaya-feya-tut-ne-rabotaet-struktura-emali-zubov-krokodilov-i-ih-doistoricheskih-predkov","title":{"rendered":"The tooth fairy doesn't work here: the structure of crocodile teeth enamel and that of their prehistoric ancestors","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"The
\n
\nYou enter a dimly lit corridor, where you encounter destitute souls tormented by pain and suffering. But there will be no peace for them here, for behind each door lies even greater torment and fear, filling every cell in their bodies and overwhelming all thoughts. You approach one of the doors, behind which you hear a hellish scraping and buzzing that chills you to the bone. Gathering the remnants of courage, you extend your cold hand to the doorknob when suddenly someone touches your shoulder from behind, startling you. \"The doctor will be free in a few minutes. Please take a seat; we will call you,\" a gentle voice of the nurse informs you. This is how some people imagine a trip to the dentist, particularly those who have a strong aversion to these \"sadists\" in white coats. But today, we will not speak about dentophobia; we will talk about crocodiles. Yes, indeed, about them, or rather about their teeth, which do not require dental treatment. <\/p>\n

Scientists from the University of Missouri (USA) conducted a study on crocodile teeth that revealed interesting features of the enamel of these impeccable hunters, who rely heavily on their jaws. What did the researchers find out, how do the teeth of modern crocodiles differ from their prehistoric relatives, and what is the benefit of this study? We will learn this from the research group's report.<\/a><\/noindex><\/p>\n

The foundation of the research<\/h3>\n

\nFor most vertebrates, teeth are an essential attribute of obtaining and consuming food (anteaters are not included). Some predators rely on speed while hunting (cheetahs), others on teamwork (lions), and for some, the strength of their bite plays a huge role. This also applies to crocodiles, which sneak up on their prey in the water and grab them with their powerful jaws. For the prey to be unable to escape, the grip must be strong, resulting in significant loads on the bone structure. To neutralize the negative effect of their powerful bites, crocodiles have a secondary bony palate that is firmly connected to the skull. <\/p>\n

\"The
\nA clear demonstration of the opening and closing of a crocodile's jaw.<\/i><\/p>\n

One of the main features of crocodile teeth is their constant replacement with new ones as the old ones wear out. The thing is, crocodile teeth resemble a nesting doll, inside which new teeth develop. Approximately every two years, each tooth in the jaw is replaced with a new one.<\/p>\n

\"The
\nNotice how tightly this \"dental trap\" closes.<\/i><\/p>\n

Crocodile teeth are divided into several categories based on their shape and corresponding function. At the front of the jaw, there are four large canines that are crucial for effectively capturing prey. In the middle, there are thicker teeth that increase in size along the jaw. This part is necessary for cutting prey. At the base, the teeth widen and become flatter, allowing crocodiles to crack open the shells of mollusks and turtle shells like seeds. <\/p>\n

How strong is a crocodile's jaw? Naturally, it depends on its size and species. For example, in 2003, it was found that a 272-kilogram Mississippi alligator bites with a force of about 9500 N (N \u2014 Newton, 1 N = 1 kg\u00b7m\/s\u00b2). Meanwhile, a 1308-kilogram saltwater crocodile demonstrated an astounding force of about 34500 N. For reference, the absolute bite force of a human is approximately 1498 N.<\/p>\n

Bite force depends not so much on the teeth as on the jaw muscles. In crocodiles, these muscles are very dense and numerous. However, there is a significant difference between the well-developed muscles responsible for closing the mouth (which provides such biting power) and the weaker muscles responsible for opening it. This explains why a closed crocodile mouth can be held shut with simple tape.<\/p>\n

\"The
\nWell, show us who called you a little one.<\/i><\/p>\n

But crocodiles need their jaws not only for merciless killings for food but also for caring for their offspring. Female crocodiles often carry their hatchlings in their jaws (it's hard to find a safer place for them, as who would dare to go there). The mouths of crocodiles are equipped with very sensitive receptors, allowing them to regulate their bite force, which enables them to better hold onto their prey or gently carry their young.<\/p>\n

Unfortunately, human teeth do not grow back after the old ones fall out, but there is something in common with crocodiles \u2014 enamel.<\/p>\n

\"The
\nImage #1: the caudal tooth of the American alligator (Alligator mississippiensis).<\/i><\/p>\n

Enamel is the outer covering of the crown part of the tooth. This is the hardest part of the human body, as well as that of many other vertebrates. However, unlike us, as we know, teeth do not get replaced, so our enamel needs to be thicker. Crocodiles, on the other hand, replace worn teeth with new ones, so there is no need for thick enamel. Sounds quite logical, but is that really the case?<\/p>\n

Scientists say that understanding the changes in enamel within one taxon will allow for a better understanding of how enamel structure changes depending on the biomechanics and diet of the animal. <\/p>\n

Crocodiles, namely Alligator mississippiensis<\/i>, are well suited for this research for several reasons. First, their teeth, bite force, and enamel structure change depending on the age and size of the individual, which is also influenced by dietary changes. Second, crocodile teeth have different morphologies depending on their position in the jaw. <\/p>\n

\"The
\nImage #2: a and b show the difference in teeth between large and small individuals, while c and e show the teeth of fossil ancestors of modern crocodiles.<\/i><\/p>\n

Rostrally positioned teeth are slender and are used for capturing prey, while caudally positioned teeth are blunt and are used for crushing with higher bite forces. In other words, the stress on the tooth depends on its position in the jaw and the size of the owner of that jaw.<\/p>\n

This study presents the results of analysis and measurements of absolute enamel thickness (AET) and size-standardized (relative) enamel thickness (RET) of crocodile teeth.<\/p>\n

AET is an estimate of the average distance from the enamel-dentin junction to the external surface of the enamel and is a linear measurement. RET, on the other hand, is a dimensionless quantity that allows for the comparison of relative enamel thickness across different scales.<\/p>\n

Scientists evaluated AET and RET of rostral (at the 'nose' of the jaw), intermediate (in the middle of the row), and caudal (at the base of the jaw) teeth in seven individuals of the species. Alligator mississippiensis<\/i>.<\/p>\n

It is also important to note that enamel structure can depend on the diet of the individual and the species as a whole. Crocodiles have a very diverse diet (whatever they catch becomes lunch), but it differs from that of their extinct relatives. To verify this in terms of enamel, scientists conducted an analysis of AET and RET in fossils. Protosuchidae<\/i> (UCMP 97638), Iharkutosuchus<\/i> (MTM VER 2018.837) and Allognathosuchus<\/i> (YPM-PU 16989). Protosuchidae<\/i> is a representative of the Jurassic period, Iharkutosuchus<\/i> \u2014 of the Cretaceous period, and Allognathosuchus<\/i> from the Eocene.<\/p>\n

Before the actual measurements began, researchers conducted a brainstorming session and proposed several theoretical hypotheses:<\/p>\n