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.