Skip above the Mud!
Yes, mudskippers do skip above the mud, as implied by their name, but besides that, there are more things about them that make them one of the most unique and fascinating fish that is blog-worthy.
A mind-blowing excerpt from David Attenborough’s BBC Life series episode 04: Fish – Mudskipper (click here to watch) would give you a very nice introduction on the amazing mudskipper and its survival methods.
Mudskippers are members of the subfamily Oxudercinae (genus Periophthalmus), within the family Gobiidae (Gobies).These comical-looking (their baggy, colourful eyes and funny little wobbly nose that twitches every now and then make them look like an animated character) yet fascinating amphibious creatures are uniquely-adapted to live a pretty demanding life in tropical, intertidal habitats. Their huge googly eyes give them an all-round view. To keep their eyes moist when they are on land, they periodically pull in their retractable eyes into the watery eye sac, known as a “dermal cup”. They have dorsal fins on the back and a muscular pectoral fin on each side to crawl over the mud. Like other fish, mudskippers breathe through gills, but they also absorb oxygen through their moist skin and the linings of their mouths and throats. Their enlarged gill chambers, where air bubble is retained, close tightly when the fish is above water, keeping the gills moist and function properly.
Mudskippers dig deep, u-shaped burrows to cool their body down, avoid predators during high tide, and raise their offspring. As the tide comes in and out, the burrow is flooded and requires constant attention to keep it open. To read more about the species of mudskippers that exist in Singapore, click here.
What amazes me about mudskippers is that despite the challenge mating poses, the males strive to attract the females to reproduce in the name of survival (sustaining their species’ existence). By extending their tails against the mud, they perform their highest possible leaps to get noticed by the females. They also use dorsal displays (raising and lowering dorsal fin) and tail stands (standing on the base of their muscular tail with the head and pectoral fins clear of the ground, as practised by bearded mudskipper Scartelaos histophorus), maintaining the entrance pools to their burrows using sinusoidal motion and fighting off competing males through agonistic encounters (which include dorsal display, circling of the competitor and charging with open mouth).
While courtship behaviour may vary among species, most mudskippers have very specific requirements for mating and laying eggs. During the mating season, males may darken their body colour. When a male has attracted a female, the pair enter the burrow to mate. Eggs are laid in an air chamber in the burrow. In some species, both parents guard the burrow (for example Periophthalmodon schlosseri and Scartelaos histophorus) while in other species (for example Periophthalmus modestus and Periophthalmus magnuspinnatus) the male chase the female out of the burrow and take care of the eggs on his own. The guarding parents constantly and painstakingly replenish oxygen in the egg chamber (by repeatedly collecting gulps of air from the surface and depositing them in the chamber) to allow the eggs to develop, because the water trapped in the burrows is normally oxygen-deficient. When embryonic development is complete, the parents expel the air in the egg chamber (by gulps of air) during high tide. This allows the eggs to be submerged in water and hence induces hatching.
A quick comparison with another fish from the same family, red-spotted dwarf gobby (Trimma okinawae) would make us realise that they share pretty similar courtship behaviour. For example, both males would have vibrant colour to attract the females, show off their strength by fighting other males that intrude their territories, and leaping or ‘dancing’ to impress the females. In addition, red-spotted dwarf gobby females may immigrate to the nest of another male and spawn there!
However, they are living in a harsh world. The Giant mudskipper (Periophthalmodon schlosseri), for instance, is consumed in some countries such as Taiwan and is listed among the threatened animals in Singapore, mainly due to habitat loss. While other mudskipper species are not listed as endangered, like other creatures living in intertidal habitats, they are affected by human activities such as land reclamation and pollution. It is very disheartening to see these amazing creatures suffer because of us. It is time for us to protect their habitats and observe or even learn from them.
“Behaviour and sexual dimorphism of the blue mudskipper, Scartelaos histophorus (Pisces: gobiidae),” by Townsend, K.A. & Tibbetts, I.R. Proceedings of the Royal Society of Queensland 112: 53-62. Brisbane. ISSN 0080-469X, 23 May 2005.
(accessed on 9 Apr 2013).
“Lifestyle of Korean mudskipper Periophthalmus magnuspinnatus with reference to a congeneric species Periophthalmus modestus,” by Gun Wook Baeck, Toru Takita & Yang Ho Yoon. The Ichthyological Society of Japan, 21 Dec 2007.
URL: http://link.springer.com.libproxy1.nus.edu.sg/content/pdf/10.1007%2Fs10228-007-0009-y (accessed on 9 Apr 2013).
“Amazing Animals – Mudskipper,” by David Attenborough’s BBC Life series episode 04: Fish – Mudskipper, uploaded by kumeek onto YouTube Channel, 11 Apr 2010.
URL: http://www.youtube.com/watch?v=KurTiX4FDuQ (accessed on 9 Apr 2013).
“A Taxonomic Revision and Cladistic Analysis of the Oxudercine Gobies (Gobiidae: Oxudercinae),” by Murdy EO (1989). Australian Museum. Suppl 11: 1–93, 1989.
URL: http://www.australianmuseum.com/Uploads/Journals/17704/93.pdf (accessed on 9 Apr 2013).
“A Guide to Gobies of Singapore,” by Larson, Helen K and Kelvin K. P. Lim. Singapore Science Centre. 164pp. 2005.
Hosted on WildSingapore: http://www.wildsingapore.com/wildfacts/vertebrates/fish/gobiidae/mudskipper.htm (accessed on 9 Apr 2013).
“Polygynous Mating System of Trimma okinawae (Pisces: Gobiidae) at Kagoshima, Japan with a Note on Sex Change,” by Tomoki Sunobe & Akinobu Nakazono. 1990 Paul Parey Scientific Publishers, Berlin and Hamburg. Ethology, 84: 133–143. doi: 10.1111/j.1439-0310.1990.tb00790.x
URL: http://onlinelibrary.wiley.com.libproxy1.nus.edu.sg/doi/10.1111/j.1439-0310.1990.tb00790.x/pdf (accessed on 10 Apr 2013).