Updating the Paratilapia polleni log (the Italian side of the story).

In the beginning there were (here in Rome) simply 22 - almost dull in colour – tiny fishes. At that size – as with almost all fishes – they could be “everything” .. but these miniatures where clearly showing the tilapine spot! So, they were definitely Paratilapia polleni “small spot” (from the East Cost of Madagascar). Having said that (more details are available here) let’s return to present days. I will just tell you in advance that 5 of these beauties, after being frown up a bit, were donated to my friend Marco Isidori (an experienced aquarist and our team-mate in the 1999 visit to Lake Malawi).

Lets focus now on the fishes remaining in my tanks. Since it was no longer possible to keep all fishes in the two grow-out tanks they were (after some arrangements which included the donation of many Malawi cichlids which caused me a great sorrow) separated into two groups:

Nine fish were moved in the 750 liters tank which has NO plants because of the two big plecos still living there in the hope that ample space would keep aggression at bay. The remaining six specimens were moved in a 125 liter tank. My plan is to donate or sell them once I can find an owner whose skills I can trust. Those six fishes live in a tank with a lot of plants since the only tankmates are a pair of Ancistrus! Things went on happily (except for spawning: no REAL signs till today!) and once the small fishes had turned into magnificent fishes some differences became very evident. The  fishes which remained in the 125 liter tank are consistently smaller in size (compared to the ones kept in the 750 liter tank). However, the only known spawning attempt (unsuccessful) happened in the small tank, a finding which was also observed in George's tanks.

Paratilapia polleni in the 125 lt tank, possibly it’s a female.

 Right now I’m in the process of setting up an outdoor 200 liter tank to house the small pair outside during spring/summer and see what comes out. However, life in the large tank (OK bigger since LARGE is ONLY George’s 1300 lt tank!) showed some remarkable facts:

Paratilapia polleni in 750 lt tank.

 Beyond the fact that differences in the shape of fins are clearly visible (they are reported to be - along with nuchal humps, size, and differences in colours – sexual distinctive characteristics) another remarkable point to look at is the, so called, “lateral line”. The lateral line is a sensory apparatus found on all fishes (that only in cichlids is – as far as I know - divided in two parts) that allows fishes to move safely, in absolute darkness (without hitting on the rocks for example). The lateral line allows both the predator to hunt (at night) and the pray to hide, is related to the ability of the fish to keep its balance and the correct swimming position as well as other forms of interaction of the fish with its surroundings! The question is why is the lateral line of P. polleni so clearly visible ? Is it because Paratilapia polleni are “crepuscular hunters” (which makes sense to me since I’ve noticed, in my tanks, these fishes eagerly feeding ALSO with lights “off”!) and therefore need a better developed / larger lateral line when compared to a “daylight prowler” ? Why is it not that visible in smaller specimens (regardless of size / decoration of the tank hosting them) ? This question needs an answer which I don't have..

 

Finally – to make my point more clear - take a look at the (slightly blurred) picture above. Would you believe that this fish comes from the same batch with the fish shown in the photo over it ? I can tell you it is – even if it is hard to believe - since they both grew in my tanks in which all fishes were introduced at the same time and almost at the same size. My larger specimens are now almost 15/18 cm in size and this given fish hardly reaches 4/5 cm (even though sometimes it shows more intense colors than the larger ones). Moreover, some of the specimens kept in the much smaller 125 lt tank are larger than this one. During the last months, this “dwarf” P.polleni had to be rescued (it was a member of the crew that were introduced in the Big One, aka 750 lt tank, at the beginning) and moved to a back-up tank having been heavily bullied! Once it regained a minimal physical strength it was returned to the main tank and managed to get on well (despite its smaller size). The fish is still doing well but it simply seems to “refuse to grow” and is a bit shy. Maybe it is also afraid of the larger fishes in the tank - and I am not referring to the other P. polleni only.. ?

Again a question comes up in my mind, generated by the following statements / observations :

1. In every batch of fry there are different growth rates resulting in dominant / subdominant specimens, sex differences and more. I have come to consider this fact as “normal” (and may possibly happen in the wild, too).
2. Fishes kept in smaller quarters may end up with unnaturally reduced growth, undue aggression, being too prone to illness, and more ...

Then: how comes I’m facing the following, in some way, strange situation:

·        Largest fish developed in the bigger tank and carry on growing even though there is NO sign of spawning activity (all my fishes are aged about one and a half years old).

·        Medium sized fishes live in the smaller unit, seem to have stopped growing and, although shy, seem to have started some kind of breeding attempts.

·        The smallest fish (amongst all the fishes I have)  lives in the bigger tank, feeds happily, shows good colors and temper ... it is just used to stay hidden most of the time (does the fish – actually - realize their relative size ?).

OK Folks, things listed above are in a mess and are not reported in a “scientific” way but despite something like thirty years of fish keeping behind me I’m a bit puzzled. Something strange seems to take place here. Maybe future parts of this “never ending” log will reveal more details and give us a solution / explanation. For the time being I have no answer to those questions ...

This update is over, for the time being. Maybe either George of I will revert on those topics in the future, if we have more observations or information to add. Now I will finish this update with a close up of a “smiling” Paratilapia polleni.

Paratilapia polleni close-up, again in my 750 l tank.