parvu­lus

P. parvulus Tangkiling  Foto: Olivier Perrin“

First descrip­tion:Ein neuer Labyrinth­fisch von Bor­neo — Parosphromenus parvu­lus nov. spec. Das Aquar­ium 13 (120):247250.

Char­ac­ter­is­tics: total length max. 3.5 cm. Dor­sal struc­ture: X-​XI, 56, total 1517, anal fin: VIII-​IX, 1011, total 1820. Much leaner, with a less high back com­pared to the other species, with the excep­tion of P.ornaticauda, which can be regarded as a “twin species”. Adults appear to have a wide, rather then high, oval cross-​section, seen from the front. Like ornat­i­cauda it dif­fers also in behav­iour and col­oration. The ♂ shows char­ac­ter­is­tic, nagyi–like body col­oration in breed­ing coloura­tion: lower half of the body very dark to black, upper half yel­low to yellow-​brown. Also the pat­terns of the unpaired fins dif­fer, like those of P.ornaticauda, from the typ­i­cal pat­terns in this species: dor­sal and anal fin are black with red spots.

Depend­ing on the local­ity, there are var­i­ous degrees of very lumi­nous white iri­des­cent edges. The ven­tral fins are trans­par­ent, the cau­dal fins are almost colour­less or dark-​blackish. Nup­tial coloura­tion is shown often, but not as con­tin­u­ously as by P.ornaticauda. The species-​typical striped pat­terns can be seen some­times in sex­u­ally mature males, but mainly in tran­si­tion to breed­ing colours. The female shows the striped pat­terns most of the time, and unlike ornat­i­cauda, never an appear­ance which is almost iden­ti­cal with the nup­tial colours of the male. Regard­ing vari­a­tion within of the species, please refer to “Distribution/​Occurrence”.

Sim­i­lar species: in males con­fu­sion is not pos­si­ble; it can be dis­tin­guished by colour and pat­terns from the struc­turally sim­i­lar species P.ornaticauda In females in nor­mal dress, the fish can be con­fused with P.ornaticauda. Small fry are almost indis­tin­guish­able. Due to the body struc­ture, the risk of con­fu­sion with other species of licorice gouramis is low.

Occur­rence /​Dis­tri­b­u­tion: South­ern Cen­tral Bor­neo: Kali­man­tan Ten­gah, in the area of Ban­jar­masin. First dis­cov­ery took place 250km NW of this city near Palan­gan in the catch­ment area of the Mentaya-​River. Later ex pedi­tions have shown that the species has a much wider dis­tri­b­u­tion thanwas assumed. So it was found by H. Linke and J. Knüp­pel in 1988 in Palangkaraya; it was already clear then that the area of occur­rence is much big­ger as orig­i­nally thought. Later fur­ther local­i­ties were found, among oth­ers by Linke and O. Per­rin. Thus P.parvulus turned out to be the licorice gourami with the (so far) largest known area of distribution.

How­ever the fish caught there showed a small but sig­nif­i­cant vari­a­tion, espe­cially con­cern­ing the pat­terns of the fins. So the fish from the vicin­ity of Tangk­il­ing had the clear­est white lumi­nous edges in dor­sal and anal fin and also a sig­nif­i­cant red dot pat­tern mainly in the dor­sal fin, while the pop­u­la­tion, exist­ing near Babu­gus has a more mod­est coloura­tion (both col­lected by H. Linke).

Threat: Even P. parvu­lus is highly endan­gered today by relent­less destruc­tion of its habi­tats, despite the fact that more loca­tions are known than at the time of its dis­cov­ery. While some of the older local­i­ties have already dis­ap­peared, many of the lat­terly dis­cov­ered places have become more or less affected by human activ­i­ties. The ongo­ing progress of for­est destruc­tion increas­ingly threat­ens for­merly unaf­fected remain­ing wet­lands, which are prone to trans­for­ma­tion to short-​term use as farmland.

Discovery/​First import:dis­cov­ered near Palan­gan and­brought to Europe by Edith Korthaus and Dr. Wal­ter Foer­sch in 1978. The first descrip­tion was made in Ger­many in con­nec­tion with this first import.

Trade:before 2005 P. parvu­lus was not seen in trade at all. The few fish, which were then in the aquar­ium stock, orig­i­nated from pri­vate imports or were bred from these. From 2006 onwards, some exports or imports were known and mean­while this species is some­times avail­able in trade. Com­pared to ornat­i­cauda it is only offered in small num­bers in pet shops, but – because the fish is very unim­pres­sive there – they are doomed even faster then its twin species.

Care /​Breed­ing: con­cern­ing care the fish dif­fers lit­tle from P.ornaticauda, but some­times it seems to be less pre­car­i­ous. How­ever, breed­ing this species is still a mys­tery, as reli­able breed­ing (and car­ing) cou­ples are not the rule. Also this species prefers caves with a small diam­e­ter, in which they can lay their often small clutches (825 eggs). Also for parvu­lus a low germ den­sity is the pre­req­ui­site for the sur­vival of the eggs. For this rea­son breed­ing suc­cess has often occurred only after a drop of the pH value to 4 or even less. G. Kopic reports of breed­ing suc­cess at pH 2.7. But this exper­i­ment should not be repeated with­out any good rea­son. Kopic also reports that lar­vae had dif­fi­cul­ties free­ing them­selves from the egg shells. This is why arti­fi­cial breed­ing with­out the car­ing male poses even more risk than it usu­ally does. With nat­ural care by the male at higher pH val­ues, com­plete clutches often dis­ap­pear overnight, but there have been suc­cess­ful broods at pH 6.0 and more. Low germ den­sity often, but not always, cor­re­sponds with low pH val­ues. Also the con­duc­tiv­ity has to be low, prefer­ably below 35 microSiemens/​cm, because oth­er­wise the clutches would not stick to the caves’ ceil­ings, and the eggs would fall down and per­ish. Like P.ornaticauda, P. parvu­lus is not a beginner’s fish.

Behav­iour /​Par­tic­u­lar­i­ties:like its twin species, P.parvulus per­forms a head-​up courtship. Caves are accepted at the bot­tom, near the sur­face or in suit­able posi­tions at any place in the plant lay­ers. Also here, as for its twin species, the area of its activ­ity is much greater than other licorice gouramis, because the P.parvulus male does a spec­tac­u­lar courtship dance, which we have already described for the other species: first the male presents its flut­ter­ing fin edges and then zig-​zags around a female. How­ever the strik­ing colour approx­i­ma­tion of the females to the male´s nup­tial plumage, which can be recog­nised dur­ing the courtship behav­iour of P.ornat­i­cauda, does not take place with P.parvulus. Still, both species stand out clearly as twins within the genus, due to their struc­tural and behav­ioural par­tic­u­lar­i­ties. Even­tu­ally they may form a spe­cial group, together with the slim form of P.sumatranus, which would indi­cate an evo­lu­tion­ar­ily closer relationship.

Parosphromenus parvu­lus ‘Tangk­il­ing’ pho­tographed by Olivier Perrin

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