Rhodeus fangi has been described as Pararhodeus fangi by Miao in 1934 from the southern part of Jiangsu Province, China. Arai & Akai then provided a taxonomic revision of the subfamily Acheilognathinae in 1988 and placed this species in the genus Rhodeus.
I have previously misidentified this species as Rhodeus suigensis (Mori, 1935).
Male Rhodeus fangi show attractive coloration, especially when the tank is exposed to sun beams.
Distribution and habitat
Rhodeus fangi is native to eastern Chinese provinces like Liaoning, Jiangsu, Shandong, Hebei (including the municipalities of Beijing, Tianjin and Shanghai) and Zhejiang.
They inhabit standing or slowing moving waters necessarily in coexistence with mussels of the genera Unio, Cristaria, Anodonta and Sinanodonta. All habitats have a sandy or muddy bottom or a silt up gravel-sand mixture frequently covered by a layer of leaf litter. Submerse vegetation is abundant. The water reacts alkaline and possess medium to high hardness, since mussels require a certain level of carbonates for shell formation.
Rhodeus fangi is a smaller sized bitterling that thrives in planted tanks with low current
Maintenance in aquaria
Rhodeus fangi is a small sized bitterling featuring appealing coloration and - common to all bitterlings - a very interesting way of reproduction. I obtained my fishes in March 2008. I bought around 80 feeder fishes from a local aquarium store for my shoal of Opsariichthys bidens, all of them possessing a total length between 15 to 30 mm. Usually these kind of feeder fishes are composed of Pseudorasbora parva (almost 80%), Rhodeus ocellatus and rarely Oryzias latipes. They are sold as a dragon fish snacks. After introduced the feeder fishes into the tank I noticed that there are ‘somewhat strange’ bitterlings (in total 4 individuals) among the common Rhodeus ocellatus shoaling together to build a protective bulk against the deadly Opsariichthys. Since I am always on the hunt for extrordinary species I netted them out and placed them into another tank for a closer look.
After a couple of days of identification they turned out to be Rhodeus fangi. I had 1 male and 3 females. The male possesses a nice coloration easily distinguished by the grey-blackish abdomen. Secondarily there is light red lipstick and a submarginal red band in the anal fin. Females possess a paler coloration and carry an ovopositor. When not spawning the ovopositor reaches the basal end of the anal fin. As they were in good conditions the male started to court the females after a short while chasing them throughout the boundaries of the tank, stretching all unpaired fins demonstrating his superiority and power.
water parameter (May 2008)
Temperature
19
ºC
pH
7.4
Conductivity (EC)
220
µS/cm
Total Dissolved Solution (TDS)
110
ppm
I am maintaining the bitterlings in a 70x50x40cm tank. There is a 3-4 cm high layer of 3 mm gravel as bottom, some Anubias and a large wooden root. I use one flourescent tube for lightning, thus lightning is not bright. The water is filtered according to the HMF principle using air. The generated current is minimal. The only tank mate was a single Traccatichthys pulcher which I introduced into the tank for taking some pictures, but never removed. There was no sign of disharmony between these two species when kept together. In May 2008 I removed the loach and introduced 6 mussels (Sinanodonta woodiana [Lea, 1834]).
The freshwater mussel Sinanodonta woodiana is frequent in China and thus is easily available for Chinese hobbyists.
I placed all 6 mussels, 3 smaller and 3 bigger, in the middle of the tank. The mussels instantly started to move using their food. The next morning a found some of them in the posterior part of the aquarium, which is a little weird, because they must have moved through a very narrow path aside the big wooden root towards the back. During the next days all mussels changed their positions and locations again and again. There was only one big mussel (77 mm in length, 49 mm in width) which did not move at all, it just changed its relative position. This specific mussel died some weeks later. The decaying mussel made a massive water change necessary to remove all its parts including the gravel around the body which seemed to be contaminated.
At this time my bitterlings reached a SL of 25 to 35 mm. The male was slightly bigger than the females. They showed immediately interest in the introduced Sinanodonta. The females seemed to inspect and check the mussels thoroughly for their capability as a potential egg host; a female stands close to a mussel (around 10 mm distance) opening and closing the mouth, swimming closer and away, in some cases this behaviour took more than a minute. It seems they want to desensibelize the mussel by doing this. After a while the mussel’s closing reflex reception seems to be mitigated. Interestingly I never saw a female interested into the mussel not moving and dying some weeks later. Apparently the females are able to evaluate the mussels fitness. Only healthy individuals are chosen as a potential egg host.
Female Rhodeus fangi permanently carry an ovopositor, an egg laying tubular organ. When it comes to spawning it is extended and is steered by a special conical muscle. The muscle can be seen during the spawning only.
So far I did not find any released young, but I am confident to do so after a couple of weeks. According to different sources the bitterlings young stay at least 4 weeks within the mussel. BAENSCH & RIEHL (1997) state the fry overwinter in the mussels. A wing-like extension of the yolk sac prevent a too early ejection of the fry by the mussel. Egg carrying mussels are supposed to suffer in fitness. ZENG, LIU & SHEN (2006) call the bitterling-mussel relationship simbiotic. But in fact the mussel seem not to have any advantage from carrying bitterling eggs, therefore this kind of relationship should be called parasitism.
Marco Endruweit, 2008-06-08, modified 2011-03-29
Literature:
Arai, R. & Y. Akai 1988: Acheilognathus melanogaster, a senior synonym of A. moriokae, with a revision of the genera of the subfamily Acheilognathinae (Cypriniformes, Cyprinidae). Bulletin of the National Science Museum Series A (Zoology) v. 14 (no. 4): 199-213.
Miao, C. P. 1934: Notes on the fresh-water fishes of the southern part of Kiangsu I., Chinkiang. Contributions from the Biological Laboratory of the Science Society of China. (Zoological Series) v. 10 (no. 3): 111-244.
