Long time no see – that’s why I wanted to share with you a shot of what I think is one the most intriguing European freshwater fishes. The photo shows two males of the Greek endemic and unfortunately also critically endangered killifish Valencia letourneuxi. If you thought the European freshwater fauna is drab and dull, think again. Courting and battling males of V. letourneuxi are just one of the most stunning things you’ll ever see.
Two sparring males of Valencia letourneuxi from southern mainland Greece
This is a shot of an ~18 days old Economidichthys pygmaeus larva. While I didn’t spend much time post-processing the photo, I’m kind of proud that it still turned out quite nicely, especially given the fact that this little fishlet is merely a few millimeters in size. It was taken with an old manual focus Revuenon lens reverse-mounted with a set of extension rings to a Lumix GX1. Diffused lighting was achieved by mounting an external flash above the aquarium.
Economidichthys pygmaeus larva, 18 days old
I’ve had somewhat of a tough time breeding this species; this was mostly due to the female re-entering the spawning cavity for a second time after she had deposited her eggs, this time devouring what she should actually leave to the male’s custody. Removing the female directly after the spawning act did the trick. Raising the tiny larvae doesn’t seem like rocket science either, they already started feeding on baby Moina after a couple of days.
This is a courting male of Economidichthys pygmaeus, a tiny freshwater species of the sand-goby complex. This Greek endemic prefers broken reed stems for spawning. I also took some video footage of the courtship and spawning, so if anyone’s interested, I could post it here as well.
Did you know that Europe is extraordinarily rich in cave fauna? Particularly the Dinaric Karst of the Western Balkans is ranked high among the global hotspots of hypogean biodiversity. Everyone knows the Olm, Proteus anguinus, a highly adapted troglobiontic amphibian species endemic to this area. But there’s an incredible number of other cave-dwellers, most of them hardly known to us people above the surface, and probably just as many are still to be discovered.
Monolistra pretneri, strikingly carrying two aquatic beetle larvae on its back
To me, one of the most fascinating and diverse elements of the European underworld are the aquatic crustaceans. You might be familiar with Niphargus, an extremely widespread genus of Gammarus-like freshwater scuds of the family Niphargidae, occuring in cave and spring habitats throughout (not only) Europe.
Much more striking is Sphaeromides virei, a comparatively large, predatory troglobiontic freshwater isopod that is, like most true troglobionts, blind and unpigmented. It is very reminescent of the marine giant isopods of the genus Bathynomus and actually belongs to the same family, Cirolanidae, even though it doesn’t grow quite as big. Another genus of freshwater isopods with marine origin, Monolistra, belongs to the family Sphaeromatidae. Related genera like Sphaeroma typically occur in coastal marine and brackish water habitats, while Monolistra is restricted to subterranean freshwater bodies and springs of the Adriatic drainage. The bodies of many of the currently described 17 species are covered with spines and tubercles. Of the species depictured here, found in a cave near Vransko Jezero in Croatia, there exists a form with spines (M. pretneri ‘spinulosa’) and a smooth-bodied morph. The individual shown belongs to the latter.
I got to tell you about a very special critter that has come to be a favorite of mine recently. As those familiar with the topic will know, some neogobiine fish species lately have been making their “escape from the Ponto-Caspian”, as Matthew Neilson and Carol Stepien put it. Facilitated by intense ship traffic and construction of canals, they are in the process of invading most of (not only) Europe’s waterways. Likewise, the same is happening with other ponto-caspian animal groups, among which especially the gammarids (Amphipoda) are thought to have a noticable impact on autochthonous biocoenosises in other parts of the world. Most of you have probably heard of Dikerogammarus villosus, the infamous “killer shrimp”, that can be quite a predatory little bugger, but all that it can actually be accused of is being highly omnivorous and euryoecious.
Obesogammarus obesus, pair in amplexus
But it hardly is the only gammarid currently on its way west. Members of the genera Echinogammarus, Obesogammarus, Pontogammarus and others have joined it, but while D. villosus is a common sight these days, many of the other species remain cryptic to most people. To pick up from the start, I have a new favorite among these hardly-noticed invaders: Obesogammarus obesus. It has a stocky, robust habitus and seems to spend most of its time burrowed in the substratum under stones, though it isn’t all that shy in the aquarium. But what’s most striking is the way it moves: Unlike most European gammarids, it moves with its back pointing upwards. If it moves, which it doesn’t do a lot, it hardly ever swims; instead, it crawls rather slowly and seemingly thought-through, sniffing here and there, altogether leaving a rather relaxed impression. All this crawling and sniffing, combined with the goldish-white coloration on is back, first made me think of a hamster, but actually it’s much more reminiscent of a badger. So that’s how I came to call it the honey badger scud…
My Rhinogobius rubromaculatus youngsters that hatched in August are about two and a half months old now and have grown quite a lot since their early days. At least one other person in Germany has successfully bred them now and it seems they’re totally unproblematic in just about every aspect. My bunch even takes pellet foods now! So just to show you how they have developed and what colours they’re starting to show, here are some new photos.
Just a quick shot of a Padogobius bonelli from the Tiber drainage in Umbria, Italy, where the species was introduced probably 15 years ago and now threatens the endemic populations of its congener, Padogobius nigricans. The photo shows a juvenile female already sporting a fashionable stripe pattern that not every individual exhibits.
Here’s a little video of my breeding pair of Mogurnda cingulata (M. sp. “Fruata”). The reason I’m putting this up here is that the female exhibits a strange behaviour I haven’t read about before: While the male keeps up his normal job of sticking closely to the eggs, defending and fanning them as well as removing fungused ones, the female still isn’t chased away. Note that the video was shot about 30 hours after the spawning had been finished. She keeps displaying towards the male, even seeking closer contact, without any agonistic behaviour shown by the male. If you observe closely, it actually seems as if she was assisting the male in defending their spawning territory. At least to me, observing this striking behaviour quite reminescent of cichlids, with the female seemingly playing an active part in parental care, was somewhat confusing, but I’m still trying to evaluate if I’m interpreting this behaviour correctly. If anyone has made interesting observations on this, may it be on this or any other Mogurnda species or other eleotrid, I’d be glad to have some feedback.
Meanwhile, I’m back in Vienna. During the last week I spent in Munich, a bunch of Rhinogobius rubromaculatus fry hatched from a spawn that I hadn’t even noticed, so I was really surprised when I discovered the first youngster hopping around among the adults. The offspring is probably a little over 3 weeks old now and they’re growing pretty fast at the moment. They’re consuming loads of Artemia-nauplii and they’re also really quarrelsome, constantly displaying towards and chasing around each other. Note that this behaviour started when they were just a few days old and hardly visible in the tank. They’re real little fighters.
Here’s two photos so you get an impression of what they look like right now – with Artemia-filled bellies.