African Bullfrog

I really enjoy winter time. It’s not my favourite season but I usually prefer winter over summer. The main reason for this is because I feel like I can do more do keep myself warm than I can do keep myself warm. When it’s really cold I can add more and more layers and curl up under blankets to stay warm. However, when it’s hot I try to wear as little clothing as possible. Unlike my method, the African bullfrog (Pyxicephalus adspersus) has a different approach to staying cool that involves forming a cocoon with many layers.

The African Bullfrog lives in desert areas and will form a cocoon to hibernate in to reduce water loss. The cocoon is made from the epidermal cell layers that the frog will shed. In six weeks 26 cocoon layers can accumulate around the frog. When the frog emerges it consume the cocoon (Withers, 1995). Before initiating the formation of the cocoon the African bullfrog will remain dormant for 20-30 days. The cocoon has been proven to beneficial early in its development. The rate of water lost by the frog inside the cocoon quickly declines and each cocoon layer increases resistance to evaporation (McClanahan et al., 1983).

The formation of this cocoon is a response caused by dehydration stress. By forming these cocoons the frog is able to survive long periods of seasonal desiccation while they are buried underground (Loveridge & Withers, 1981). Many other desert-dwelling frogs have similar formations of cocoons to survive harsh conditions (Lee & Mercer, 1967). Because a similar adaptation can be found in other species it is likely that convergent evolution occurred because of similar environmental conditions.

 Here's a video of the African Bullfrog helping its tadpoles survive during dry periods:

References:

Lee, AK & Mercer, EH 1967, ‘Cocoon surrounding desert-dwelling frogs’, Science, vol. 157, no. 3784, pp. 87-88, doi:10.1126/science.157.3784.87.

Loveridge, JP & Withers, PC 1981, ‘Metabolism and water balance of active and cocooned African bullfrogs Pyxicepalus adspersus’, Physiological Zoology, vol. 54, no. 2, pp. 203-214, <http://www.jstor.org/stable/30155821>.

McClanahan, LL, Ruibal, R & Shoemaker, VH 1983, ‘Rate of cocoon formation and its physiological correlates in a Ceratophryd frog’, Physiological Zoology, vol. 56, no. 3, pp. 430-435, <http://www.jstor.org/stable/30152608>.

Withers, PC 1995, ‘Cocoon formation and structure in the estivating Australian desert frogs, Neobatrachus and Cyclorana’, Australian Journal of Zoology, vol. 43, no. 5, pp. 429-441, doi:10.1071/ZO9950429.

The Gerenuk

Height is a characteristic that is commonly asked about as we grow up. However, not everyone grows to be the height that they originally want to be. I am one of those people. Even though I’m short the only time it really bothers me is when I need to reach for something in a grocery store or something in the top cupboard. In order to get the item I want I have learned that I will need to either climb onto something or find a spatula so I can extend my reach. In north-eastern Africa the gerenuk (Litocranius walleri) will stand on its hind legs in order to reach food.

Gerenuk Standing up
 (Miller, 2005)

The gerenuk has long, slender limbs and an elongated neck which separates it from other gazelles. There are many other herbivores living in the same arid conditions resulting in more competition for food in these areas. To reach higher food sources the gerenuk will stand on its hind legs to reach food that other herbivores are unable to reach. This adaptation also helps them in the arid conditions of Africa (Leuthold, 1978a). By standing on their hind legs they are able to reach food sources that contain more water. Their diet has been found to consist mostly of leaves and the tips of shoots. No herbs or grasses were found in their diet suggesting that they rely more on food sources that are higher up (Leuthold, 1978b).

Even though this adaptation helps the gerenuk reach higher food sources and gives it an advantage over species that can’t reach as high, its legs are fragile. If the gerenuk feels threatened and has to run across uneven ground it is more likely to injure its leg. This can be considered a trade-off between its ability to escape and its ability to continuously get food which affects the cost of survival and costs for future reproduction (Steams, 1989). The costs of not getting enough food most likely outweigh the costs of having fragile legs in gerenuks.

Here’s a video of a gerenuk giving birth and the calf taking its first steps:

References:

Leuthold, W 1978a, ‘On social organization and behavior of the gerenuk Litocranius walleri (Brooke 1878)’, Ethology, vol. 47, no. 2, pp. 194-216, doi:10.1111/j.1439-0310.1978.tb01831.x.

Leuthold, W 1978b, ‘On the ecology of the gerenuk Litocranius walleri’, Journal of Animal Ecology, vol. 47, no. 2, pp. 561-580, doi:10.2307/3801.

Miller, R 2005, Gerenuk standing up, Photo, PBase, <http://www.pbase.com/millerr/image/53997572>

Stearns, SC 1989, ‘Trade-offs in life-history evolution’, Functional Ecology, vol. 3, no. 3, pp. 259-268, doi:10.2307/2389364.

Lyrebird Song

Do you enjoy singing? I think it’s really fun to sing even if I’m not the most talented singer. However, I prefer to sing when nobody is around or when you can’t distinguish my voice in a crowd of people. My attitude towards singing is a lot different from bird species, such as the lyrebird (Menura novaehollandiae), that sing to attract mates.

Lyrebirds have amazing mimicry abilities. They are able to mimic the songs of different birds they have heard and incorporate it into their own song. However, they aren’t limited to songs of other birds. Male lyrebirds will incorporate other sounds they have heard in the forest into their song in order to have a unique song that will attract females. When mimicking songs they will maintain the complex structure of songs but will not repeat elements of the songs as originally heard. There is a trade-off between the accuracy of mimicry and versatility. It has been found that there is strong selection on males that imitate accurately (Dalziell & Magrath, 2012).

When a male is trying to attract a mate it will perform a spectacular display on carefully tended mounds. They will choose positions that give them a good acoustical advantage and in cooler areas, covered in dense ground cover that is cleared for the display (Robinson & Frith, 1981). Even though the song of the lyrebird is considered to be part of its mating ritual that isn’t the case for all birds. The songs of birds can have other purposes such as being territorial. However, Murie (1962) proposed that birds, and other animals, may sing because it is aesthetically pleasing. He argued that as humans we enjoy the beats and melodies of music, not just the lyrics. With this being the case we can assume that this enjoyment can have evolutionary roots and therefore that animals may sing because it is pleasing to the ear. What do you think? Do you think that the enjoyment of music is limited to humans or do animals sing their songs because they enjoy it?

Here is a video of the lyrebird’s song:

References:

Dalziell, AH & Magrath, RD 2012, ‘Fooling the experts: accurate vocal mimicry in the song of the superb lyrebird, Menura novaehollandiae’, Animal Behavior, vol. 83, no. 6, pp. 1401-1410, doi:10.1016/j.anbehav.2012.03.009.

Murie,OJ 1962, ‘Why do birds sing?’, The Wilson Bulletin, vol. 74, no. 2, pp. 177-182, <http://www.jstor.org/stable/4159044>.

Robinson, FN & Frith, HJ 1981, ‘The superb lyrebird Menura novaehollandiae at Tidbinbilla, ACT’, Emu, vol. 81, no. 3, pp. 145-157, doi:10.1071/MU9810145.

Hippos Sweating Blood

I am not from an area with a particularly warm climate. In the summer it can be really warm but the heat doesn’t last for a long time. Whenever it‘s super warm I normally hide in the shade or the air conditioning. If I’m going to be outside for a long time I need to put sunscreen on and I know I’m going to be sweating, both of which are necessary but annoying. The hippo (Hippopotamus amphibious) has adapted in a way that when it sweats it is protected from ultraviolet rays.

When a hippo sweats it looks like it's sweating blood. However, when hippos are hot the substance they produce is not strictly sweat. Hippos will secrete a substance that is a thick clear liquid that changes to a red-brown colour after a few minutes. Two chemicals have been extracted from this liquid each having its own pigment, one red and one orange. The red pigment acts as an antibiotic protecting the hippo from infection. The orange pigment blocks a good portion of ultraviolet and visible spectrum rays (Saikawa et al., 2004).

Sweat glands are found only in the skin of mammals and appear to be controlled by the nervous system. They have different functions including thermoregulation, protection against frictional damage, acting as scent glands, and bacterial actions (Jenkinson, 2006). Hippos are native to central Africa which is constantly under direct sunlight and heat (Gowland, 2004). With the chemical with the orange pigment in their skin hippos are able to withstand being out in the sun for long periods of time. Male hippos are also aggressive towards each other in order to mate with a female. Because of this sexual competition, the ability of the red pigment in their sweat helps the hippos avoid getting infections and allows them to continue to search for mates.

Here’s a video with hippos sweating and some other fun facts:

References:

Gowland, F 2004, ‘Hippos lead the way in multipurpose sun screen’, Journal of Experimental Biology, vol. 207, no. 19, pp. 4-7, doi:10.1242/jeb.01196.

Jenkinson, DM 2006, ‘Comparative physiology of sweating’, British Journal of Dermatology, vol. 88, no. 4, pp.397-406, doi:10.1111/j.1365-2133.1973.tb07573.x.

Saikawa, Y, Hashimoto, K, Nakata, M, Yoshihara, M, Nagai, K, Ida, M & Komiya, T 2004, ‘Pigment chemistry: The red sweat of the hippopotamus’, Nature, vol. 429, no. 363, doi:10.1038/429363a.

Spanish Ribbed Newt

Whenever I think about ribs I’m normally thinking about where I can find the best prime ribs for dinner or that I appreciate how they protect the important organs in my body. I consider my ribs to be pretty good at defence, especially when I accidentally walk into something or somebody. However, the simple defence that my ribs accomplish is nothing compared to how the Spanish ribbed newt (Pleurodeles waltl) uses its ribs for defence.

A) Area of high secretion B) Posture
when extending ribs (Heiss et al. 2009)

The Spanish ribbed newt has spear-shaped ribs that can be forced through its body wall when it is feeling threatened by a predator. In order to project their spines through their skin, the newt will bend its body to a maximum angle of 92°. A two-headed joint had to be developed in order for the ribs to be protruded.  The areas where the ribs penetrate are beneath lateral orange warts which provide a potential aposematic signal to predators. These areas also lack permanent pores despite penetration happening multiple times (Heiss et al. 2009).

Not only can the ribs defend against predators but their skin secretions are also toxic. When the rib tips go through the skin the secretion coats them. Therefore, if a predator attacks it won’t only be stabbed by the ribs but the poison on the skin of the newt will also harm the predator (Nowak & Edmund, 1978). If the predator attacks the newt using its mouth the poison will be injected into the mouth and will cause pain or death. Even though the skin of the newt is damaged it likely has a remarkable ability to repair skin and peptides that protect it against pathogens (Zasloff, 1987). Even though the newt harms itself in order to avoid being eaten the harm that it causes to itself doesn’t seem to hinder its ability to continue surviving.

I couldn't find a video of it using its ribs for defence so this video is just it walking around:

References:

Heiss, E, Natchev, N, Salaberger, D, Gumpenberger, M, Rabanser, A & Weisgram, J 2009, ‘Hurt yourself to hurt your enemy: new insight on the function of the bizarre antipredator mechanism in the salamandrid Pleurodeles waltl’, Journal of Zoology, vol. 280, no. 2, pp. 156-162, doi:10.1111/j.1469-7998.2009.00631.x.

Nowak, RT & Brodie, ED 1978, ‘Rib penetration and associated antipredator adaptations in the salamander Pleurodeles waltl (Salamandridae)’, Copeia, vol. 1978, no. 3, pp. 424-429, doi:10.2307/1443606.

Zasloff, M 1987, ‘Magainins, a class of antimicrobial peptides from Xenopus skin: isolation, characterization of two active forms, and partial cDNA sequence of a precursor’, Proceedings of the National Academy of Sciences of the United States of America, vol. 84, no. 15, pp. 5449-5453, < http://www.pnas.org/content/84/15/5449?tab=author-info>.

Basilisk Lizard

I am a land animal. I understand that very clearly. Even though I enjoy spending time in the water, I know that if I met a hungry predator I would be doomed. My body is not built in a way for me to advantageously move through the water like a fish. I can run on land faster than I can swim in the water. However, if I could run on water I would have a better chance of surviving. Although I can’t run on water the basilisk lizard (Basiliscus plumifrons) can, but how is this tetrapod able to run on water bipedal?

The way a basilisk lizard runs on water has three main steps: slap, stroke, and recovery. During the first step the lizard slaps the water surface after swinging in through the air cavity. The lizard then strokes downwards allowing air to rush in behind the foot and produce an air cavity. In the last step the lizard will prepare for the next step after lifting its foot upwards within the air cavity (Glasheen & McMahon, 1996). The mode that basilisk lizards use for bipedal locomotion is different from legged running. The typical bipedal form of running consists of the hind limbs acting like a spring. However, in these lizards the hind limbs act more like a piston which only generates force during a step (Hsieh & Lauder, 2004).  The tail of the lizard is thought to be used mostly for counterbalance and may also produce some thrust (Hsieh, 2003).

The three steps of the basilisk lizard (Hsieh & Lauder, 2004).

The main reason they can run on water is likely to avoid predators both in the water and on land. To avoid terrestrial predators they will leave the land. By running on the water they are to able avoid aquatic predators. Even though they can swim well and hide under the surface of the water, they can move more quickly by running on the surface of the water than swimming in it (Rand & Marx, 1967). The lizards that are faster have a higher chance of survival than those that are slower.

Watch this lizard run on water:

References:

Glasheen, JW & McMahon, TA 1996, ‘A hydrodynamic model of locomotion in the basilisk lizard’, Nature, vol. 380, pp. 340-342, <http://www.life.illinois.edu/ib/426/handouts/Basilisk_Glasheen_%20McMahon.pdf>.

Hsieh, ST 2003, ‘Three-dimensional hindlimb kinematics of water running in the plumed basilisk lizard (Basiliscus plumifrons)’, Journal of Experimental Biology, vol. 206, pp. 4363-4377, doi:10.1242/jeb.00679.

Hsieh, ST & Lauder, GV 2004, ‘Running on water: Three-dimensional force generation by basilisk lizards’, Proceedings of the National Academy of Sciences of the United States of America, vol. 101, no. 48, pp. 16784-16788, doi:10.1073/pnas.0405736101.

Rand, AS & Marx, H 1967, ‘Running speed of the lizard Basiliscus basiliscus on water’, Copeia, vol. 1967, no. 1, pp. 230-233, doi:10.2307/1442206.

Sea Cucumbers

I never enjoy getting sick, especially if it’s a sickness like the flu in which vomiting is a normal occurrence.  It is one of the most unpleasant feelings I think I’ve experienced. If I could never vomit again I would be one of the happiest people alive. It’s easy to understand why I would hate to be a sea cucumber, which basically vomits as defence mechanism.The sea cucumber Holothuria forskali will expel Cuvierian tubules when they are irritated. These tubules will then lengthen, become sticky and immobilize organisms (Vandenspiegel et al., 2000) by entangling the predator. These tubules are connected to the small and large intestines in the posterior part of the animal. Not only do they entangle the predators but they are also toxic which is effective against non-specialist predators (Dyck et al., 2011).

Normally when an organism loses an organ it is unlikely to survive. However, after the sea cucumber expels these tubules they will regenerate. Regeneration occurs immediately when many tubules have been expelled, but if only a few tubules were expelled there is a short period before regeneration occurs. Even though the tubules are regenerated it takes five weeks for them to be totally regenerated (Vandenspiegel et al., 2000). This brings up the question as to whether or not it is worthwhile to expel these tubules. In most cases when an organism is being preyed upon there is a flight or fight response. In the case of the sea cucumber it can’t run away very quickly but it doesn’t have a traditional method of fighting either. It doesn’t have to expel all of its tubules at one moment and as long as it has some tubules to expel, the sea cucumber has a method of fighting predators. Since the tubules do regenerate it isn’t losing its ability to fight either.

Here's a video about the sea cucumber:

References:

Dyck, SV, Caulier, G, Todesco, M, Gerbaux, P, Fournier, I, Wisztorski, M & Flammang, P 2011, ‘The triterpene glycosides of Holothuria forskali: usefulness and efficiency as a chemical defense mechanism against predatory fish’, Journal of Experimental Biology, vol. 214, pp. 1347-1356, doi:10.1242/jeb.050930.

Vandenspiegel, D, Jangoux, M & Flammang, P 2000, ‘Maintaining the line of defense: regeneration of cuvierian tubules in the sea cucumber Holothuria forskali (Echinodermata, Holothuroidea)’, The Biological Bulletin, vol. 198, no. 1, pp. 34-49, < http://www.biolbull.org/content/198/1/34.short>.