Abstract
Through their evolution, monotremes have developed several characteristics that make them unique from most other mammals. The focus of this paper lies on the electroreceptive capabilities of monotremes. Electroreception of monotremes is partially comparable to that in fish. The bill of the platypus, Ornithorhynchus anatinus, and the beaks of the echidnas, Tachyglossus aculeatus and Zaglossus bruijni, all contain three types of receptors: push-rod mechanoreceptors, serous gland electroreceptors, and mucous gland electroreceptors. The information collected by these receptors is sent to the somatosensory cortex. The platypus, whose electroreceptive system is more complex than that of the echidna, uses electroreception to capture prey and is the only mammal know to so. (It is not yet known if the echidna uses electroreception to capture prey.)
Introduction
Monotremes have fascinated scientists since their discovery in 1799 (Moyal 4). The isolation of monotremes in Australia has allowed monotremes to evolve several unique characteristics. One newly discovered mystery of these animals is their electroreceptive capability. This discovery brings up many questions. How did monotremes evolve this elaborate sensory system? What do these electroreceptors look like, and how do they function? How do monotremes perceive this "sixth sense?" This paper will attempt to address these questions.
Monotreme Diversity
Order Monotremata is split into two families and three species. Ornithorhynchus anatinus, commonly called the platypus, can be found in eastern Australian rivers and creeks from Queensland all the way down the coast and across the Bass Strait into Tasmania (Moyal 18). The platypus is not a large animal. Males, which can weigh 2.35 kg and reach .56 m in length, are larger than the females (Dawson 9-10). The platypus swims with its mouth, ears, and eyes shut (Dawson 10). O. anatinus sifts the bottom for food, which is mainly non-insect invertebrates, crustaceans, worms, some vertebrates, and benthic larvae of various insects (Dawson 10).
The two other surviving species of monotremes are Tachyglossus aculeatus, the short-beaked echidna, and Zaglossus bruijni, the long-beaked echidna. Echidnas range throughout Australia and New Guinea as well as islands adjacent to both land masses (Collins 17). Both species have characteristic modified hairs that function as spines (Dawson 10-12). T. aculeatus is a stocky animal (3-5kg) with a small head and pointed snout (Dawson 10-11). Z. bruijni is larger than T. aculeatus (~10kg) and has a downward curving snout (Dawson 11-12). The snouts and tongues of T. aculeatus and Z. bruijni are ideal for diets of termites, ants, and earthworms (Dawson 10-12).
Cephalopods are known to be exceptionally intelligent by invertebrate standards and in some respects even rival “higher” vertebrates. These animals have many highly evolved sensory and processing organs that allow them to gain a greater understanding of their environment and their place within it. Due to their advanced structures, many of which are analogous to vertebrate structures, and abilities they have been widely studied. Their methods of learning have been of prime interest and many experiments have been conducted to determine the different ways in which octopuses can learn. From these experiments four main kinds of learning have been identified in octopuses: associative learning, special learning,
The Harlem Renaissance was an intellectual and literary period of growth promoting a new African American cultural identity in the United States. The decade between 1920 and 1930 was an extremely influential span of time for the Black culture. During these years Blacks were able to come together and form a united group that expressed a desire for enlightenment. This renaissance allowed Blacks to have a uniform voice in a society based upon intellectual growth. The front-runners of this revival were extremely focused on cultural growth through means of intellect, literature, art and music. By using these means of growth, they hoped to destroy the pervading racism and stereotypes suffocating the African American society and yearned for racial and social integration. Many Black writers spoke out during this span of time with books proving their natural humanity and desire for equality.
The Texas horned lizard can be distinguished by a large flattened body, two large spines on their heads, two rows of fringed scales on their sides, keeled scales on their backs, abdomen, and sides, a white stripe down their back, and brown lines near their eyes (Pianka & Hodges 1995). It inhabits arid environments and preys on small insects, but primarily ants (Oklahoma 1996). The Texas horned lizard is most anatomically similar to the Australian thorny devil, (Moloch horridus), which is most likely due to convergent evolution (Pianka and Parker 1975). Both species of lizards have different phylogenies and lineages, but appear to share common morphological and ecological adaptations due to similar habitats and ...
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...C3Rs - Primate sensory capabilities and communication signals: implications for care and use in the laboratory. NC3Rs - National Centre for the Replacement, Refinement and Reduction of Animals in Research. Retrieved November 17, 2011, from http://www.nc3rs.org.uk/news.asp?id=187
At first glance platypuses seem to be an amalgamation of mammals, birds, and everything in between. In fact, their reproduction biology also has much in common with a variety of animals—reptiles, birds, placentals and marsupial mammals. Platypuses belong to a group of animals called monotremes. These egg-laying mammals have been a mystery to researchers since their discovery by Westerners over 200 years ago. The first specimens of platypuses brought back to England were thought to be hoaxes similar to mermaids (Moyal, 2001). Found only in and around Australia, there are only three living species of monotremes: the platypus (Ornithorhynchus anatinus) and two species of echidnas (Tachyglossus aculeatus, and Zaglossus bruijni).
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Fox, R. 2001. Invertebrate Anatomy OnLine: Artemia Franciscana. Lander University. http://webs.lander.edu/rsfox/invertebrates/artemia.html, retrieved February 13, 2011.
Gould, Edwin, George McKay, and David Kirshner. Encyclopedia of Mammals. San Francisco, CA: Fog City, 2003. Print.
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