The South Australian Museum and the Fiddler Rays: A taxonomic riddler

The South Australian Museum and the Fiddler Rays: A taxonomic riddler

  • By Admin
  •  September 10, 2015
  •  Tags:  Blogs & news Collections

The striking black and white patterned Magpie Fiddler Ray, has been long listed as one of South Australia’s rarest fishes, but there has always been doubt that this was a separate species from the more common and widespread sandy and brown coloured Southern Fiddler Ray. The colours and patterns were clearly different, but with just two other minor differences in their appearance, the scientific community had its doubts.

Visually different but what about genetically? Top: Southern Fiddler Ray specimen (SAMA F13961: Trygonorrhina dumerilii (Castelnau 1873)) Bottom: Magpie Fiddler Ray specimen (SAMA F13928: Trygonorrhina melaleuca Scott 1954)

Visually different but what about genetically?
Top: Southern Fiddler Ray specimen (SAMA F13961: Trygonorrhina dumerilii (Castelnau 1873))
Bottom: Magpie Fiddler Ray specimen (SAMA F13928: Trygonorrhina melaleuca Scott 1954)

Given that the Magpie Fiddler Ray is listed as threatened by the IUCN Red List, and immature male fiddlers are common in prawn trawl bycatch, it was important to clear this up. Clarifying whether it was a different species would have an impact on its conservation status and approach to management.

Conservation management of naturally rare or seldom encountered fish can be tricky, as documenting changes to abundance can be a challenging task. The Magpie Fiddler Ray was considered to be genuinely rare, not just hard to observe, because all known specimens were found in shallow waters of the well-populated and frequently trawled coastlines of the Gulf of St Vincent and Kangaroo Island.

DNA analysis would have resolved the issue once and for all. However scientists were thwarted by a lack of specimens suitable for DNA analysis and its apparent rarity as the Magpie Fiddler Ray was known, until recently, from only a single specimen deposited in the South Australian Museum over 60 years ago.

Scientists couldn’t wait 60 years for another Magpie Fiddler Ray to show up, so the South Australian Museum turned to the citizen scientist community for help. From 2001 it issued calls through the media and recreational fishing websites for people to watch out for specimens of this elusive but easily recognised species.

Those calls were successful, with two specimens and three new photographic records of the Magpie Fiddler Ray coming through from the recreational fishing community between 2001 and 2013. Surprisingly, most were from the Adelaide suburban coast and the Port River.

Magpie Fiddler Ray

A fisherman rarely catches a Magpie Fiddler Ray: on the line and in a photo! Photo courtesy of John Marsh

This gave the team enough material to work with. They used the latest DNA sequencing technology to compare the genome of these new Magpie Fiddler Ray specimens with 50 specimens of the Southern Fiddler Ray. They also analysed examples of the Eastern Fiddler Ray, to provide a ‘yardstick’ for the between species. All comparative samples were drawn from the South Australian Museum’s phenomenal Australian Biological Tissue Collection, the largest in the southern hemisphere, with more than 138,000 animal tissues available for genetic analysis collected over five decades.

Genetic analysis of the specimens showed very clear results. The Southern and Eastern Fiddler Rays were clearly highly distinct, and in contrast the two Magpie Fiddler Ray specimens were obviously members of the Southern Fiddler Ray gene pool.

Scientists simultaneously re-examined the appearance of these rays, including their shape, length and skin features but found no significant differences apart from the colour pattern. The strongly black and white pattern of the Magpie Fiddler Ray could be attributed to ‘leucism’, a condition that results in loss of pigmentation that isn’t uncommon in many kinds of fishes and other vertebrates.

And so the team was able to demonstrate that the Magpie Fiddler Ray, isn’t its own species at all, but is a colour variation of the common and widespread Southern Fiddler Ray. They published their results in the scientific journal “Zootaxa” in July 2015. Distribution maps of the Fiddler Ray species based on museum collection records from all over the country, are available through the Atlas of Living Australia.

Professor Steve Donnellan, Chief Research Scientist at the South Australian Museum’s Evolutionary Biology Unit commented that “this is the sort of science that museum researchers love doing, it involves interested members of the public to solve long-standing mysteries and of course we couldn’t do it without the efforts of many people over many decades accumulating invaluable specimens, tissues and records in our museums. It’s this sort of approach involving focused public partnerships that we like to use increasingly to solve issues in our fish research program.”