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| Pseudomugil signifer- photo© Günther Schmida |
Kner, 1865
Pacific Blue-eye
Description
Due to the wide geographical range of this species the colours and markings on the body and fins can be variable. Southern populations have a body colouration of translucent to olive-greenish above, canary yellow below; the caudal peduncle tinged with red. There is sometimes a broad dark band from pectoral to tail. First and second dorsal spines long and white though blackish at base - rest of the fin olive-green. Second dorsal with front and exterior margins black'; rest of fin scarlet; anal similar to second dorsal. Caudal scarlet, the outer rays, tips of lobes, and sometimes central rays blackish. Pectorals olive-green, with upper rays black. Ventrals bright yellow. As the name indicates, the eyes are a beautiful blue. Females are less colourful; have smaller rounded clear dorsal and anal fins with a dark line on the anterior edge of the second dorsal fin.
Male specimens from north Queensland populations have extremely long extended filaments on both the dorsal and anal fins. They have a silvery to yellowish body, with the elongated parts of fins blackish, also margins of second dorsal and anal fins. Edges of upper scales dark, and often a dark stripe along the side. The young are yellowish-brown with dark spots on dorsal and caudal fins. A black band along middle of sides with a similar but shorter dark band above and below it on the caudal peduncle. About six rows of dark spots along the scale rows, fading out posteriorly. Spawning males display a coppery-gold body colouration.
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| Pseudomugil signifer [Ross River, Townsville] - photo© Günther Schmida |
First discovered at Sydney in the 1860's by an Austrian expedition, they were the first blue-eye species to be scientifically described. A few years later specimens collected from north Queensland were given various scientific names finally being known as Pseudomugil signatus. In 1979, researchers using electrophoretic analyses and a large sample of specimens taken from 14 localities along the east coast of Australia determined that all populations were scientifically indistinguishable from one another. Although they did recognise that there were genetic, morphological and osteological differences. However, it would be apparent that further work is warranted on the taxonomic status of the Pseudomugil signifer populations. There are two major geographical populations - those north and south of the Herbert River, with an intermediate form in the Townsville area.
Peter Unmack proposed that areas north and south of the Burdekin River were probably two separate biogeographic regions, which is similar to the area known as the Burdekin Gap by biologists studying terrestrial fauna. The genetic break between northern and southern populations of Pseudomugil signifer is remarkably consistent with the Burdekin Gap, and it may be that this area has been a long term isolating barrier between northern and southern groups.
Distribution
Pseudomugil signifer has a widespread distribution along the east coast of Australia. They have been recorded from just north of Eden on the southern coast of New South Wales to the Olive River, Cape York Peninsula. They have also been reportedly found in the Mission River near Weipa on the western coast of Cape York Peninsula.
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| Pseudomugil signifer [Ross River, Townsville] - photo© Neil Armstrong |
Habitat & Ecology
Pseudomugil signifer inhabit freshwater to fully marine conditions, being found in mangrove areas, salt marshes, and several offshore islands such as Lizard Island, Hinchinbrook Island and in mangrove habitat on the Low Isles. They inhabit waters with a temperature range of 15-28° Celsius, and pH 5.5 to 8.3. They may reach a maximum size of 6 cm (northern populations), but usually less than 4 cm (southern populations). Two dorsal fins, very close together, the first much smaller than the second.
In their natural environment spawning usually occurs from October to January. An egg-scatterer, generally spawning amongst aquatic plants and grasses. Females usually shed 1 to 2 eggs each spawning and up to 9 eggs may be laid a day at peak of breeding season. Eggs have adhesive filaments that attach to vegetation. Eggs will take around 12 to 17 days to hatch at a temperature range of 22 to 28° Celsius. Rapid development of larvae means larvae reach maturity within 6 months. Males exhibit territorial behaviour guarding the spawning site from intruding conspecifics. In captivity prespawning behaviour is initiated adjacent to the spawning site by the male raising his fins and swimming in a zigzag pattern to block the female's retreat. Spawning usually occurs in late morning and early afternoon with the female entering the spawning site first, followed by the male. After spawning, the male will continue to display, defending his territory and thus the fertilised eggs.
Remarks
Pseudomugil signifer has been maintained in the aquarium hobby for many years, and were first introduced to the international hobby in 1932.
© Copyright Adrian R. Tappin
Updated January, 2007.
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