Fishtail acupuncture

Stimulated by Gu et al 2021.[1]

Visual abstract from Gu et al.[1]

fishtail – the rearmost fish fin or caudal fin
zebrafish – (Danio rerio) a freshwater fish belonging to the minnow family
eleutheroembryo – a free-floating embryo of a fish
IF – impact factor
hpf – hours post fertilisation
FTW – fresh tap water
hpa – hours post acupuncture

key to terms and acronyms

As far as I can tell, this is an entirely novel use of acupuncture, so I thought I should share it here. Acupuncture is in the title of the paper, so naturally it popped up on my searches the other day. But that was about the only thing I was familiar with from the title. The terms zebrafish eleutheroembryo and caudal fin acupuncture were both quite new, whilst they do allow for a fairly accurate guess at the actual meaning.

I obviously had to check that caudal fin acupuncture was in fact a form of acupuncture applied to the tail fin of a fish rather than something entirely different.

I also search for ‘trigger point’, which occasionally turns up unexpected papers that have nothing whatsoever to do with myofascial pain. The same does not normally happen with ‘acupuncture’, but I was suspicious in this case.

caudal fin acupuncture

Well, caudal fin acupuncture did indeed turn out to be an intervention quite like acupuncture applied to the tail fin of a zebrafish embryo using a needle-like projection drawn out from a fine glass (capillary) tube.

What on earth were these researchers doing by applying acupuncture to the tail of a fish embryo? Well, the clue is in the title of the journal – Science of the Total Environment (IF 5.90). They were using an acupuncture intervention to stimulate immune activity and create a model that might be more sensitive to change when exposed to environmental pollutants.

I guess the fact that these researchers were based in Hangzhou meant that the idea of using acupuncture was closer to home than might otherwise have been the case. I have mentioned Hangzhou on the blog a couple of times before – in March 2021 and May 2019.

The zebrafish embryos hatch from 48 to 72 hours post fertilisation (hpf). At 72hpf they were anaesthetised by adding tricaine to the water at a specific concentration. Then each fish was placed onto an agar plate to perform the micropipette acupuncture in the tail fin at the end of the notochord. The fish were then transferred into beakers of fresh tap water (FTW). The control fish were treated in the same way apart from the tail fin piercing.

I was pleased to see that survival was not significantly different in either group, and was 98 to 99%, so the intervention they labelled as acupuncture was not measurably traumatic.

A variety of immune factors were measured over the subsequent 72 hours post acupuncture (hpa), and broadly speaking you can see an immediate proinflammatory response followed by a longer more modest anti-inflammatory effect in the acupuncture group compared with controls.

The same process was repeated with a new set of zebrafish eleutheroembryos, and exposure to 3 different concentrations of beclomethasone dipropionate. The concentrations differed by 1 and 2 orders of magnitude, ie equivalent to doses of x1, x10 and x100.

Zebrafish reproduce quickly, have large broods and are translucent

Zebrafish are convenient models for a number of reasons, not least of which is that they reproduce quickly, have large broods and are translucent. Whilst their immune system is considered primitive compared with that of higher vertebrates, it is distributed throughout all tissues and includes both innate and adaptive components.

There is significant overlap between zebrafish and mammalian genetics and physiology, and 70% of human genes have equivalent versions in the zebrafish.

70% of human genes have equivalent versions in the zebrafish

Looking down the list of immune factors measured I recognised most of them, in particular TNFα and the interleukins IL1β, IL6 and IL10. The first 3 of this list being potent proinflammatory mediators and the last being an anti-inflammatory mediator.

In thinking about the relevance of fishtail acupuncture to human acupuncture interventions we need to consider two aspects: the trauma and the signalling components. The cells including nerve cells in small creatures have rather similar dimensions to those in larger animals, apart from the length of some neurons of course. So, whilst using a similar sized acupuncture needle on a small and large creature may intuitively seem to be a bigger dose for the small one, the difference at a cellular level may not be so obvious. The main difference is likely to be the relative volume of tissue affected by the needle insertion. Inserting a needle into ST36 in a mouse tibialis anterior will create a larger proportion of tissue disruption relative to the entire muscle volume compared with doing the same in a human. To complicate matters, we tend to use slightly finer needles in rodents and insert them shorter distances. If the effects we are measuring are via neural stimulation rather than a reaction to tissue disruption, this difference may be reduced somewhat although a different proportion of total nerve endings stimulated may be different.

This all makes interpretation of the immune response of a zebrafish to micropipette acupuncture rather difficult. But that is not the point of the paper of course. That is just me still trying to get my head around translation from animal modes to clinical practice following Ari’s great talk on Saturday in the second of our Scientific Meeting Series lectures for 2021.


1          Gu L, Peng S, Zhang J, et al. Development and validation of an activated immune model with zebrafish eleutheroembryo based on caudal fin acupuncture. Sci Total Environ 2021;785:147288. doi:10.1016/j.scitotenv.2021.147288

Declaration of interests MC