You wouldn’t exactly expect to attend a workshop organized by ichthyologists (scientists specializing in the study of fish) and hear someone referring to peculiar phalluses, fangs or rapid mating.
But the world of miniature fish really does include species with mind-boggling anatomies and exotic mating practices.
If you think that minuscule organisms are insignificant because megafauna are so much more awesome, take a moment from your busy day to look at this intriguing (okay, slightly terrifying) suite of creatures:
If you’re hoping that protrusion on Image B is a strangely warped fin of some kind, or a mysterious yet useless appendage, give up hoping now.
Yes, that is a penis and it includes a rod and a hook that comes in handy when the male needs to grip the female during sex.
All fishes in the Phallostethidae family have the same specialised anatomical features (penis, hook, rod); named “priapium” fish after Priapus, the god of fertility, it turns out we have two species of this family of fishes in Singapore’s mangrove areas. They are Neostethus lankesteri and Neostethus bicornis.
Phallostethus cuulong can be found in Vietnam’s Mekong Delta and the female’s genital opening is also located at her throat. Unlike most fish, this species’ eggs are fertilized inside the female. So that hook and rod are actually practical tools to ensure that fertilization takes place.
Two more useful nuggets for you to contemplate:
As painful as it all sounds, these priapium fish (a more polite and scientifically accurate way of referring to that useful apparatus) actually take their time with the mating. In summary, Phallostethus cuulong – a species that has head-to-head sex – are marvellously efficient procreators while they’re at it.
And in contrast…
Then there’s Paedocypris progenetica. Found in peat swamps in Sumatra, this translucent fish is one of the smallest vertebrates in the world, with females measuring at just 7.9mm.
Paedocypris progenetica have unique pelvic fins and enlarged (hypertrophied) muscles in the pelvic girdle – picture a muscular torso. They use it to position themselves upside down on the underside of leaves to attract females. Females then approach them and also position themselves upside down in order to begin mating.
For reasons as yet undetermined, it is an incredibly quick encounter – even quicker than the expression “at the blink of an eye” attempts to communicate.
So far, despite using the best technology available, scientists haven’t been able to clearly capture the actual mating process.
Found in a stream in northern Myanmar, the aptly named Danionella dracula, a close relative of the zebrafish which is often kept in home aquariums, is the only one of 3,700 species in the Cypriniformes (carp-like fishes) group to have these unique, fang-like projections of the jaw bones.
However, measuring a mere 17mm, this almost transparent fish can only really inflict damage on fellow males. Having studied the behaviour, researchers believe the fangs are used by males to spar with each other during aggressive mating displays.
This might not be a question keeping you awake at night, but after you spend a little time with Dr Ralf Britz, an ichthyologist at the Natural History Museum (London), you will want to learn more about miniature fishes.
“I have a weak spot for the weird fish and small things fascinate me, so I focus on them,” he tells me. “They are more difficult to study. At a microscopic level you have huge anatomical complexity.”
He has also been studying another species from the eel family (Chaudhuriidae). “They are very strange fish. They are modified anatomically with very tiny skulls. They’ve lost a lot of bones, the skull shape is odd. They live burrowing in the banks of a river.”
That weird part about lost bones and modified anatomy (all very X-Men Wolverine, yes) is an evolutionary process called “developmental truncation”.
It basically means that those crucial final stages of development that exist in the ancestor do not exist in the descendant. So, you end up with species like Danionella dracula or Paedocypris progenetica that resemble a larva (immature form of an animal before it undergoes maturity), but are nonetheless sexually mature. If you need a mental picture, here it is: a baby fish with mature sex organs. It sounds far worse than it is. Most of these creatures are actually quite lovely.
Every year when the haze makes its way to Singapore from Sumatra, words like “deforestation”, “palm oil”, “peat swamps” and “carbon sink” turn into popular hashtags. If you pay attention to the impact of the haze on wildlife in both Sumatra and Borneo (and not just humans), then orangutans are likely the first species you think of.
But maybe now you’ll think of weird and wonderful miniature fish too.
Ranging from 7.9mm to 17mm, these tiny creatures have managed to evolve in remarkably complex ways to survive in the most unexpected environments (a cave; a stream; brackish water; acidic peat swamps), even though we are doing untold damage to those very habitats.
If you’re still not convinced, consider this: peat swamp forests weren’t thought to be rich in biodiversity. Now we know that they support stenotopic organisms (i.e. an organism that is able to tolerate a restricted range of habitats or ecological conditions). So the peat swamps in our region are not just rich carbon sinks. They are microhabitats and support a range of interesting species.
If we lose them, we lose a large number of remarkable examples of what evolution has produced over millions of years. This is our evolutionary heritage. Prioritizing conservation action is not always about selecting the charismatic and the large over the nondescript or minuscule. It is about appreciating the fact that evolutionarily, the orangutan and the Paedocypris are unique events. While some events seem weirder than others, or too small to be noticed, they are not without value.
The Sundaic Freshwater Fish IUCN Red List Workshop was held at Wildlife Reserves Singapore (WRS) from February 24th – 27th. Wildlife Reserves Singapore Conservation Fund (WRSCF), in collaboration with the Lee Kong Chian Natural History Museum (LKCNHM) and the Department of Biological Sciences (DBS), National University of Singapore (NUS), brought together local and international experts to assess species in the Sunda region, perform Red Listing according to IUCN guidelines, and propose future conservation plans for vulnerable species.