Physiological Adaptations of the Plesiosaur for ‘Holding its Breath’
One hundred and fifty million years ago, large aquatic species of reptile such as the Plesiosaur dominated the ocean, and were pre-eminent predators of the sea. The branch of now extinct Plesiosaurs, or ‘near lizards’, evolved into variant closely related species specialised to take different niches in the food chain. Such species of Plesiosaur include the phenotypically similar Plesiosauroid and Pliosauroid. The physiological adaptations of the long necked variant, the Plesiosauroid, as it relates to deep sea diving, will be addressed in depth.
Oxygen breathing lungs are a universal trait of class reptilia. As such, it would have been necessary for the Plesiosauroid - a marine reptile, to return to the ocean surface to inhale air. Oxygen expenditure in reptiles is proportional to strenuosity of locomotion (Frappell, Schultz & Christian, 2002). Therefore the Plesiosauroid must have held physiological traits that enabled the species to avoid oxygen deficit while hunting deep-sea dwelling prey. This essay will outline the hypothesised respiratory, circulatory, pulmonary and sensory attributes of the Plesiosauroid as they relate to diving. These hypotheses will be supported by investigating the physiological adaptations of the Plesiosaur’s biological analogues, and the prospect of similar adaptations in the former will be speculated upon.
Reptiles have a low metabolic rate: they consume energy, and therefore oxygen, slowly. According to Robinson (1975), Plesiosauroids were enduring swimmers with lower flipper aspect ratios and drag-causing long necks. Massare (1988) made the same conclusion, since the hydrodynamic properties of the Plesiosauroids indicate the species moved no faster than 2.3 metres every second. Therefore, the species was confronted by a conundrum: it sought to dive hundreds of metres to hunt its prey yet was constrained, by virtue of its body shape, to travel at slow speed. Invariably, the animal would have been required to forgo oxygen for periods of more than a minute, while keeping the presence of mind to hunt.
Fortunately, when making its descent of hundreds of metres, the Plesiosauroid would have been able to exploit traits possessed by many of the reptile class. Many reptiles hold the ability to temporarily slow their heart rate to reduce their oxygen consumption, via bradycardia. This effect may be caused by low temperatures, such as is found deeper in the ocean, or may be voluntarily triggered by the animal.
There would be no need for the Plesiosauroid to retain all of its oxygen-consuming faculties during the long descent.
For this experiment, it is important to be familiar with the diving reflex. The diving reflex is found in all mammals and is mainly focused with the preservation of oxygen. The diving reflex refers to an animal surviving underwater without oxygen. They survive longer underwater than on dry land. In order for animals to remain under water for a longer period of time, they use their stored oxygen, decrease oxygen consumption, use anaerobic metabolism, as well as aquatic respiration (Usenko 2017). As stated by Michael Panneton, the size of oxygen stores in animals will also limit aerobic dive capacity (Panneton 2013). The temperature of the water also plays a role. The colder the water is, the larger the diving reflex of oxygen.
Ceratopsians and Pachycephalosaurs are closely related in their characteristics. Ceratopsians processed a saddle-shaped boney frill that extended from the skull to the neck and typically had horns over the nose and eyes. The most popular was the triceratops, which could reach over 26 feet and weigh in excess of twelve metric tons. Their frills served as two major functions. It protected the vulnerable neck from being harmed. The second major function that the frill provided was due to the fact that the frill contained a network of blood vessels on its underside, which were used as a means to get rid of excess heat. The Pachycephalosaurs were considered to be bipedal. They were also found to have thick skulls, flattened bodies, and tail that were covered in an array of body rods. Pachycephalosaurs were thought to have been more than fifteen feet long and processed a skull that was surrounded by a rounded dome of solid bone. It was thought that they used their heads in combat or mating contests, but that was disproved fairly recently, which I will discuss later in the paper. Both Ceratopsians and Pachycephalosaurs were “bird-hipped” and both of these suborders contained a backwards pubic bone. Both were Marginocephilia, or “fringed heads”, which is one of three clads under the Orinthiscia order. They were also herbivore dinosaurs that inherited their fringe at the back of the skull from earlier ancestors.(2) Their classi...
...s in the water, as well as quick change in pace and direction. This again is to evade predation.
Low oxygen consumption rates were reported in this study, most likely due to the low standard metabolic rates of the nurse sharks. The nurse sharks also had a lower routine metabolic rate compared to other species which was attributed to their slower swimming speeds. Metabolic rate increased with temperature. The cost of transport was lower than is found in other species. This was attributed to the nurse sharks inactivity and less streamlined body. The cost of activity is high compared to other shark species. This means that nurse sharks have a higher metabolic cost of activity when switching from rest to movement. The difference in values found in nurse sharks as compared to other species is attributed to their less streamlined
Metabolic rate is directly linked to the core temperature in an animal. An ectotherm, or cold blooded animal, warms its body mainly by absorbing heat from its surroundings. The amount of heat it derives from its metabolism is negligible. In contrast, endotherms derive most or all of its body heat from its own metabolism (Campbells,p899). Because ectotherms do not produce their own heat, they cannot actively ensure their ideal temperature for an ideal metabolic rate (aquacult.htp).
Seahorses are a prime example of species whose atypical biology and unusual global distribution leads to a series of evolutionary questions. Seahorses (genus Hippocampus) are a marine species that have extensively been studied because of their abnormal behaviors in the marine environment compared to other marine creatures. Many of the seahorse species have large ranges, both longitudinally (over a great horizontal distance across the ocean), and latitudinal (great vertical distance within the ocean), regardless of the fact that they are characterized as weak swimmers and lack any large structural fins for efficient swimming (Lourie et al., 1999a). Although they do have these large range environments, seahorses
The discovery of Willo is unique because it is the first dinosaur with a fossilized heart. However, this was just the beginning of an extraordinary find. “Not only does this specimen have a heart, but computer enhanced images of its chest strongly suggest it is a four-chambered, double-pump heart with a single systemic aorta, more like the heart of a mammal or bird than a reptile,” according to Dr. Dale Russell. Russell is a paleontologist at North Carolina State University and a senior research curator at the N.C. Museum of Natural Sciences. This discovery is unusual because all modern reptiles, except the crocodile, contain a single ventricle that pumps blood to the lungs and the rest of the body. All modern reptiles have paired systemic aortas developing from the ventricle, which distributes the blood to the body. “In contrast, the four chambered heart of modern birds and mammals has two completely separated ventricles and a single systemic aorta, ensuring that only completely oxygenated blood is distributed to the body” (Fisher 2).
Whales are considered to be intelligent mammals, but they live in the water despite the fact that mammals evolved on land. Paleontologist Phil Gingerich has been studying the evolution of whales since 1978. In 1978, he and his team discovered a rock in Pakistan with a skull on the inside. The skull appeared to be a wolf-like animal upon first sight, but Gingerich noticed the distinct whale ear on the skull. The skull, which had characteristics of both whales and other mammals, was that of a common ancestor of the whale known as Pakicetus. Many scientists believe that Pakicetus resembled the seal in its appearance. Pakicetus could not be considered a whale, since its backbone and limbs do not have similar features to those of a whale. Therefore, it is considered an ancestor of the whale, since it has some features of the whale and some unique features (or features of other mammals). Today’s whales have mammalian characteristics, which prove that they have evolved from a common ancestor of the mammal. A whale’s fin also has traits that are common of many species. The fin seems to be similar to that of a fish, but the bones on the inside of the fin are similar to those on a bird’s wing, a monkey’s arm, and a frog’s limb. This seems to be proof that these organisms, and many others, all evolved from a common ancestor. Other proof that whales have evolved over time lies in Egypt in the Valley of Whales, where over 400 fossils of whales currently lie. The desert used to be a large sea that was home to a few kinds of whales. In the Valley of Whales, Gingerich discovered the Basilosaurus, which had small hind legs, toes, and a mobile knee and lived 35-41 million years ago. This fossil is considered to be a transitional fossil, since it ha...
Stark, William S. Ph.D. 2004. Human Diving Response. Department of Biology, saint Louis University. Retrieved from starklab.slu.edu/PhysioLab/Diving.htm. April 18, 2011.
The debate of whether dinosaurs were cold blooded or warm blooded has been ongoing since the beginning of the century. At the turn of the century scientists believed that dinosaurs had long limbs and were fairly slim, supporting the idea of a cold blooded reptile. Recently, however, the bone structure, number or predators to prey, and limb position have suggested a warm blooded species. In addition, the recent discovery of a fossilized dinosaur heart has supported the idea that dinosaurs were a warm blooded species. In this essay, I am going to give supporting evidence of dinosaurs being both warm and cold blooded. I will provide background information on the dinosaur that was discovered and what information it provides scientists.
The Axolotl, a crucially endangered neotenous species of mole salamander, has adapted to fit its environment so it can easily catch food and evade predators. The Axolotl’s habitat is the lake system of Xochimilco that is near Mexico City, Mexico. This shallow, fresh water lake complex has a temperature range of 6- 20°C and a pH of 7- 12. The complex also has the Axolotl’s primary food sources of mollusk, insect larvae, and other crustaceans. However, with the introduction of foreign species such as the Asian Carp and the African Tilapia, the Axolotl now has predators that may eat and threaten it, and it has competition for the animals it usually eats. Fortunately, the Axolotl has developed adaptations that aid it in catching food and evading predators. To help it catch food the Axolotl’s teeth are shaped like cones, so that its “vacuum” action of sucking in as much water in order to also eat food is aided by the shape of the teeth, which allow it to grip, rather than chew. To aid them in avoiding predators they are able to metamorphose so that they use their lungs more than their gill, which allows them to leave very toxic waters and the predators within. Another adaption that helps them deflect any predator is that they are able to regenerate body parts that have been lost, allowing them to stay as strong as possible. Axolotl’s have adaptations that aid their survival from predators in the lake complex Xochimilco that they reside in.
The discoverer of the titanic, Dr Robert Ballard famously referred to the deep sea as ‘far more alien than going to mars or the moon.’ The deep sea is one of the largest virtually unexplored ecosystems on the planet; it is found at a depth of 1000 fathoms [1] and is subject to adverse changes in temperature, pressure and light penetration amongst other factors. Therefore as expected fish decrease in abundance, and species diversity. This trend is prominent as in order to survive the harsh conditions of the deep sea, fish need a number of specific adaptations. Allowing them to ultimately survive, feed, and reproduce.
Hutchinson, John R., Garcia, Mariano “Tyrannosaurus was not a fast runner.” Nature 28 Feb 2002: 1018-1021
The most unique feature of the platypus is the soft and pliable bill. The bill surface is perforated with openings that contain nerve endings, which allow the animal to locate food and aid movement under water. These pores contain two types of sensory receptors: mechanoreceptors, which respond to tactile pressure, and electroreceptors, which respond to electric fields. The eyes and ear openings are located behind the bill in a muscular groove, which contracts and closes as the platypus dives (Griffiths, 1998). The nostrils are positioned towards the tip of the bill and are slightly elevated upwards to allow breathing whilst the body is beneath the surface (Figure 1).
This essay discusses the evolution of amphibians. Amphibians are classified into three orders (anura, caudata and apoda) and are in the superclass tetrapoda (Kolesova, et el, 2007). The Apoda is comprised of organisms with no legs, and these organisms normally live in barrows. Tretrapods are comprised of vertebrates with four limbs; and examples of tetrapods are reptiles and amphibians (Kolesova, et el, 2007). Tetrapods were the earliest vertebrates to be able to walk on land and that was during the Devonian period about 360-370 million years ago (Kolesova, et el, 2007). Before the existence of amphibians almost all vertebrates lived in water (Kolesova, et el, 2007).