Gobiodon Citrinus, One of the "Coral Gobies" Most Popular Text & Photos: José María Cid Ruiz

Gobiodon citrinus, one of the "coral gobies" most popular Text & photos: José María Cid Ruiz

The genus Gobiodon (Perciformes, Gobiidae), comprises 31 species 1 of small gobies distributed over wide tropical areas of the Indian and Paciﬁc oceans. They are small species (between 3 and 6.5 cm in total length), with aracvev e colour paerns. These gobies typically live aachedhe d to brbran-an- ches and nooks of diﬀerent corals both "hard"ha rd" (e.g. Acropo-Ac ropo- ra spp ) as 'so' (e.g. Sarcophyton sppsp p.),.) , which rarely leave.

Like all gobies, these specieses have merged its pelvic fins, ini n this way transformeded intoi nt o an organ of aachment, which allows them to remainr em ain strongly adhered to the surfacesurfac e of the coral, eevenve n in areas of strong current. They area re sseden-ed en - tary fifishessh es with limited radius of acon,aco n, whichw hi ch basicallb as ic al lyy ccon-on - sisistsst s in goingg oing ("jumping" rather thant ha n swimming)sw im mi ng ) fromfr om a ccoralor al brbranchan ch tot o anotheran other secon. TheseThes e gobiesgo bi es rarelyr ar el y leave its coral hostho st forf or venturingv en tu ri ng intoint o openop en waters.w at er s. TheyT he y are knoknownwn po- pupularlyla rl y as "coral"c or al gobies".g ob ies". is located in placespl ac as far apart as in northern and southern Japan, Samoa, Micronesia and AustraliaAu st ra (both south and north, in the Great Barrier Reef). G. citrinus present a small sizesi ze (6.5( 6. cm the larger specimens). Juveniles have bright yellowish tones (with some dar- GobiodonGo bi odon ccitrinus,it ri nu s, bbiologyio lo gy aandnd aacclimazaoncc li ma zaon to aquariumaquarium ker variaons according to geographic origin of the populaon in queson). With the age Onee of the speciess pe ci es mostm os t commonlyco mm only keptk ep t in aquariuma qu arium is GoGo-- their color darkens. In aquarium, somemes they show a pale colour, due to any lack of biodonon citrinusc it ri nu s (Rüppell,(R üp pe ll, 1838).18 38 ). It is a species with largel ar ge dis- carotenoids in the diet, which does not provide the yellow pigment. tribuonon areasa reas including:i nc lu di ng: southernso ut he rn Red Sea (Eritrea,(Er it re Ethio- The species show no appreciable sexual dimorphism with a naked eye. In nature, found pia) , the enren re easte as t cocoastast of AfricaA fr ic a borderedbord er ed by the Indian in pairs or small groups. Ocean to Mozambique.oz am bi qu e. Addionally,Addionally , in the Pacific Ocean, it

Field studies 2 have shown that these groups are led by a specimen that stands by their larger sizeze (a male) and several somewhat smaller specimensec im ens (all females). The species produces a toxicto xi c mucus 3 that covers its body and protectss themth em from being eaten by large predatory ﬁshsh species.

As already menoned,ne d, its acvity is concentrated around coral hosth os t in which they live (mainly of the genus AcAcroporaro pora ), rarely venturing into oopenpe n wa-wa - tersrs ((itit iiss a species that has absolutelyabsol ut el y no swims wi m blbladder).ad de r) . It isi s debated whether itsit s relaonshipre la o ns hi p wiwithth thet he coralc or al isi s a symbiosissy mb io si s (arguing(a rg ui ng thatt ha t repelsre pe ls spspeciesec ie s whosewh os e feedfe ed isi s based on coralc or al polypsp ol yps and alalsoso wasw as verifiedv er ifi ed thatt ha t in thet he stomachsto ma ch contents of some sspeciespe ci es ooff thisth is genusg en us theret he re was filamentous alalgaega e whicwhichh wouldwo ul d haveha ve injuredi nj ur ed tot o theth e coral). But othershe rs authoauthorsrs believeb el ie ve thatt ha t it is a mildmi ld formf or m of pa- rasisms m (due tot o theyth ey foundf ou nd remainsr em ains ofo f coralco ra l polyps anda nd coralc or al mucusm uc us in itsit s stomachst om ach contents). Its bathymetricym etric distribuondi st ri bu on4 rangesra ng es ffromrom 2 to 20 meters. Addionally, keep in mind that this is a vulnerable species when compeng with others species for food, since they rarely go to mid -waters in search of food. Therefore, it is very appropriate its ma- When planning itsit s maintenancema in te nance in capvity,c ap we intenance on aquariums dedicated to invertebrates, reef aquariums, aquariums with small and must remember ththatat tthishi s is a plankvorousp la spe- quiet benthic species or directly keep them in specific aquariums targeted to its reproducon. cies and as such, requiresqu ir es a frequent feeding in small amounts. Some individuals may refuse to Regarding the size of the aquarium and despite its modest size and peaceful behavior towards accept frozen food ( Artemia, Mysis, Daphnia ) or others species, do not underesmate its intraspecific aggressivity, because is common in small flake and requires a period of adaptaon of seve- aquariums, watch aggressions by geng the best territories with corals placed strategically. ral weeks, during which you mix these foods with live crustaceans ( Artemia salina mainly).

Aquariums of 150 liters can accommodate a couple or a threesome properly. The aquarium should contem- plate living coral, preferably genus Acropora , or coral skeletons or arficial corals, definitely an environment and a relief that reflect their natural habitat.

Breeding in capvity G.citrinus is a hermaphrodic species. In nature, when a group loose its lider male, one of the females (generally the biggest) evolves into a male and starts lead the group again. This feature of their biology is useful for breeding in capvity, because if we acquirree a pair or trio, once well acclimated to the aquarium,ua ri um, iitt is highly likely that one of the specimens evolvee vo lve ttoo male, while the others remain as females.em al es.

The reproducve paern thatt ha t I have followed for this species was based on placingp la ci ng two groups of 6 specimens in two specificec ifi c aquariumsaq ua ri um s 30030 0 and 400 l respec-resp ec - vely. The evoluonvo lu on of bothb ot h groupsgr ou ps wasw as similar,s im il ar , beingbe in g CohabitaonCo ha bi taon was stable in both groups over severalsever al montm hs without any casuales took place. formed aer ababoutout a momonthnt h a coupleco up le ini n bothbo th tankstan ks However, it was noceable certain level of sstresstr es in specimens living on the periphery of terri- (largest specimensme ns with brightbr ig ht colorful:c ol or fu l: reddishr ed di sh head tories defended in each aquarium by ononee of the couples. and lemon yellow tonest on es ono n flanks).fla nk s) . BothBo th couplesc ou pl es con-c on - - In aquarium, if they are well acclimatedac cl im and their quality of life is high, it is not uncommon to trol a preferenal area,re a, wwherehere ttheyhe y ininteractte ra ct ttogether.og et he r. watch spawnings. My two couplesco began to make their first spawnings at about the same me, The relaonship betweenee n the componentsco mp on en ts ofo f eachea ch fourfo ur monthsm onths aer thet he iniali ni formaon of the two groups. The species spawns on a branch of pair is large tolerance. Fromro m the epicenterep ic en te r of theirt he ir tte-e- theth e liliveve or arficialar fi ci al coral which is the center of their territory. The female deposits the eggs in rritories, each pair is projectedte d to pursuep ur su e otherothe r speci-ec i- rows of circularci rc ul outline, in an area that has previously been cleaned by the male. The male then mens, but in all cases were notno t long oro r obsessiveob se ssive perpe r-- proceedspr oc ee ds to ferlize the eggs and cares about its surveillance unl hatching. secuon, as have been observeded in ototherhe r species.sp ecies.

In my tanks despite the abundant corals and rocks providedde d (perhaps due to a failure in choosing the elements over the boom), they have oen done the spawnings on the walls of the aquarium. Usuallyua ll y they have chosen lile bit visi-vis i- ble and accessible locaons next to the centerce nt er of thetheirir territory (they have co- me to spawn on the curved glass of thet he heater). The ccoupleouple located in ththee aquarium of 300 liters has performeder fo rmed spawnings with an average ooff 101000 to 115050 eggs, while the couple placedp la ced in the 400 liters aquaraquariumium got ana n averageav er ag e bebet-t- ween 60 and 80 eggsgg s by spawning. Spawning iss franklyfr ankly hard to be observed, due to thatth at the ccouplesou pl es dod o not chan-ch an - ge itsts bbehavioreh avior or coloraon in the preliminaryprelim in ar y days.da ys . OnOncece sspawningpawnin g occurs,oc cu rs , we can see how one of the specspecimensim en s (male)(m al e) alwaysa lw ay s staysst ays taking carec ar e ababoutou t ththee egeggs,gs, while the other (f(female)em al e) aassumesss um es tthehe rroleole ofof keeping out thet he othero th er gogobies.bi es . adhesive filaments. The male with its pectoral fins, is fanning ThThee eggseg gs aarere aaacheda ched to ththee susubstratebs tr ate by one of its twtwoo poles, through a set of connuously the eggs. He is also dedicated to effecvely remo- ve inferle eggs (in my couples, the inferle eggs average was around 5%). The egg, observed microscopically, has an ellipcal outline and very similar appearance to the eggs of Amphiprion (Pomacentridae) , but is much smaller, almost half (Lt: 1.1 -1.2 mm). Males of the two couples bite with determinaon the "syringe" I use to suck eggs. Embryonic development has had an average duraon of four days at 26.5 ° C. The eggs were extracted at the end of the third day in a proporon of 80%, leaving a poron of it to the care of the male unl hatching. Extracted eggs were placed in an incu- bator of eggs (conical) with sea water passed through sterilizer and a mild dose of bactericidal under moderate aeraon.

The pelagic larvae of G. citrinus are really ny, not exceeding 2.4mm Lt aatt birth andan have a very small yolk sac whi- sh. In my experience, it was not possible to develop the hatchedhe d larvaela rvae in my tankst an ks with Brachionus plicalis rofers "type -L" (300 μ). Probably higher chance of success cann be achieved with smallsmallerer rofers as B. rotundiformis or Colurella adriáca (150 μ) or nauplii (60 μ) of calanoidd copepodsco pepods as those belonging to thet genera Oithona and Par- vocalanus , among others. Copepod cultures requireeq ui re proper nutrnutrionion with unicellular algaeal ga e Isochrysis sp. and rofers should be enriched with phytoplankton,on , mixing tthehe two unicellular algae IsocIsochrysishr ys is sp.s p. anand Nannochloropsis sp. in the right proporon to achieve an intakei nt ake of essenal omega-3 fafayy acidsa cids DHAD HA anda nd EPAE PA in a raora of 2: 1. ©

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Trabajos citadosad os

1: “FishBase”is hB as e” andan d “ CaCatalogtalog of Fishes” (A.(A . of SciSciences,en ce s, CaliforniaC al if or ni a U.),U. ), review April,2014April, 20 14

2: Debelius H. 2001 “Coral Gobies” Rev. Today’sToda y’ s AquariAq ua ri um 232 3-25

3: Randall, J.E. and M. Goren,Go re n, 1993.1 99 3. “A“ A reviewre vi ew ofo f theth e gogobioidbioid ﬁshes of thet he Maldives”M al di ve s” . Ichthyol. Bull. J.LJ.L.B..B. SmithSm it h Inst. Ichth yol. (58):1 -37

4: Baensch, H.A. and H. Debelius,D eb el iu s, 1997.1 99 7. MeerwasserM ee rw asser atlas. Mergus VeVerlagrl ag GGmbH,mbH, Posach 86, 4930249302,, MeMelle, Germany. 1216 p. 3rd edion.