The Japanese mudskipper is a small fish that lives in burrows in mudflats and has several adaptations that allow it to survive both in and out of water. It is light brown or gray with white spots and has a whitish underside. It can breathe through its skin and mouth, stay out of water for over a day, and hear sounds out of water through an unknown organ. Males dig burrows and attract mates with behaviors like tail waving; they guard the eggs until the larvae hatch and disperse.

1. By: Sarah Payne Japanese Mudskipper ( Periophthalmus modestus)

2. Organization Body Color- light brown or gray Small whitish spots on the cheeks and opercula, also a few blackish dots on their flanks The abdominal plane is whitish and its head is also ventrally white They are a light brown to grey color, with small whitish spots on the cheeks and opercula, and a few small blackish dots on the flanks It is whitish on the abdominal plane and its head is also ventrally white It may have several dorsal, dark brown saddle-like bars visible

3. Adaption They have a complex network of capillaries just under their skin that lets oxygen diffuse into their blood carbon dioxide, (cutaneous respiration.) They also have special mucous that protects their skin and reduces water loss. When out of water they breather mostly through their mouths and throats which are wide, moist, and lined with capillaries; like a lung. When they swallow the air they seal their gill chamber with this special valve to lessen water loss and expand their gill covers so their throat and mouth are as large as possible. By adapting to some conditions that are so extreme they have lost some of the abilities that normal fish have. They can stay out of water for 22-60 hours that is when they are moist. Their eyes can be retracted to keep them moist, because they have fluid filled dermal cups below the orbits that the eyes like roll back into.

4. Adaptations (cont.) They can also hear and react to sounds out of water. No one knows what organ they use to hear these sounds. To adapt to a higher water temperature they will leave the water and let their body cool down through evaporation. Before it gets too dry it goes back into the water to get moist again, if there is no water pool it will roll over in wet mud. They paddle just below the waterline with their eyes above the water, otherwise they’ll just skim across the surface. On land they can climb, jump, or “crutch” along. They dig deep burrows that they lay their eggs in. The males guard the eggs. They also go to their burrows to stay safe from predators and harsh conditions.

5. Adaptations (cont.) They aren’t very good at breathing underwater so they spend most of their time in their water-filled burrows while brooding their eggs or during high tide. The water in their burrows has really low oxygen levels so they have to gulp air and then they carry it down into their burrows where they release it into special chambers. When the eggs are ready to hatch the male floods the chamber (with the eggs in) so they can leave the nest during high tide. They have sharp teeth to grab their prey while their pharyngeal jaws grip the prey and pull it down into their esophagus. In winter they hibernate in their burrows.

6. Growth they can grow up to ten cm use their large mouths to dig tunnels underground where the eggs are kept after they are born from eggs they are larvae they remain in the tunnel until they are fully grown mudskippers

7. Reproduction First the male digs a burrow on an empty mud flat. Then he changes his body color to a light grayish pinkish color to attract females, then he raises and waves his tail to make perpendicular jumps with his fins outspread. When a female approaches, the male gets her into his burrow by slow wiggling movements. These burrows have two to three narrow openings with no turrets, and a sub-vertical shaft that ends into an upturned track, where they lay their eggs. After spawning the female leaves the nest. The male guards the nest for about a week, going to the surface at low tide and gathering mouthfuls of air and then releasing the air into the chamber with the eggs, always staying near to the nest. When the eggs are developed the male floods the chamber so that the larvae can leave the nest when high tide comes. The larva floats around in the water 30-40 days after hatching.

8. How it meets its needs to survive Habitat- They live in burrows on mudflats as shown in the picture. They go on land, in their water filled burrows and they swim on the surface of the water. They have been found in Hong Kong, Korea, Japan, the Yangtze River, and other areas. Eating- They eat animals like crabs by attaching on to them and ripping them apart with (The rest of the information that fits in this category is in the adaption section)

9. Links http://www.youtube.com/watch?v=zGqae7vuUWo http://www.mudskipper.it/SpeciesPages/mode.html

10. Diagram of a Japanese Mudskipper’s Burrow Shows monitoring device positions: O 2 electrode (O), endoscope camera (E), tube for gas injection (G), stainless-steel electrodes (S) for impedance measurement (I), and pressure transducer tube connection (T). Thick dotted line above egg chamber shows the level of burrow excavation required for instrumentation. Thin broken line under the egg chamber shows approximate position of the air–water interface. The mud pellets in its burrow make it unique.

11. Diagram of a Japanese Mudskipper’s Eye C= Cornea, L= Lens, R= Retina, ON= Optical nerve, D= Dermal Cup, Red Arrow= Retinal area (where the optic nerve fibres are spread out)

12. Japanese Mudskipper during courting The first picture is of the male. In the second picture the male is the lighter colored one, he changes color to impress the female.

13. Diagram of a Japanese Mudskipper

14. Mudskipper with its eyes retracted