From a land down under, stripeys swim across the equator

Juvenile Microcanthus strigatus
Juveniles stripeys photographed at Shelly Beach, Manly, New South Wales, Australia. Juveniles are often seen seeking shelter in rock pools. Image: E. Schlogl
© E. Schlogl

If you’ve snorkelled around Shelly Beach or Clovelly in Sydney, odds are you’ve seen the beautiful and aptly named stripey (Microcanthus strigatus) – named after its eponymous pattern in brilliant yellow and black. Stripeys are often seen in large schools, marauding around jetties and harbours in the company of other sub-tropical species. They form part of a small family of mostly Australian fishes called footballers. Outside of eastern Australia, stripeys also occur along the Western Australian coast, East Asia, and Hawaii.

Microcanthus strigatus - stripeys
A large school of stripeys photographed at Fly Point, Port Stephens, New South Wales, Australia. Image: E. Schlogl
© E. Schlogl

Despite their global distribution, these populations are largely disconnected from each other, with the equator serving as a major barrier between populations from each hemisphere. Interestingly, this anti-equatorial pattern is documented for a variety of distantly related fishes, suggesting that historical dispersal events may have shaped the distribution of present day fishes.

Microcanthus strigatus, Yakushima Island, Japan
A school of stripeys photographed in Yakushima Island, Japan. Stripeys from Asia have an additional bent stripe just before their anal fin, as well as a series of spots on the chest. Image: S. Harazaki
© S. Harazaki

Recent studies have shown that these populations are deeply divergent, splitting from each other some half a million to a million years ago during the last Pleistocene glacial cycle. By reconstructing ancestral ranges, we were able to show support for an unusual dispersal pattern, with the ancestral stripey originating along eastern Australia, moving south across the Bass Strait to Western Australia, and then northward to Asia across the equator.

One of the type specimens of Microcanthus
One of the type specimens of Microcanthus collected from Shell Harbor, New South Wales. This specimen was collected in the early 1900s and is stored in the Australian Museum’s Ichthyology Collection. Image: Y. K. Tea
© Y. K. Tea

While the relict populations of stripeys today are no longer mixing, several of these populations still carry genetic signatures that echo a historical connection across the oceans. Studies like these highlight the importance of addressing widespread species and the impact they may have towards species conservation and biodiversity management, particularly if populations are genetically distinct.

Stripeys belong to the family Microcanthidae, which feature mostly Australian fishes commonly known as footballers. The other genera are Tilodon (A), Neatypus (B), and Atypichthys (D). Image: S. Schulz (A), C. Mark (B), and E. Schlogl (C & D)
© S. Schulz (A), C. Mark (B), and E. Schlogl (C & D)

The Australian Museum has a large repository of species such as the stripey that are housed in the collections. Specimens like these have the potential to shed light on historical processes, opening a window through time in which to study how life on earth has evolved.

Yi-Kai Tea, AMF/AMRI Postgraduate Award recipient

More information

  • Tea, Y.K., Van Der Wal, C., Ludt, W.B., Gill, A.C., Lo, N. & Ho, S.Y.W. 2019. Boomeranging around Australia: Historical biogeography and population genomics of th anti-equatorial fish Microcanthus strigatus (Teleostei: Microcanthidae). Molecular Ecology, doi:10.1111/mec.15172.