Xenotilapia tenuidentata Poll, 1951
text and photos: Magdalena i Przemysław Mirek (www.suephoto.com)

     This article, though so short, cost us no little effort and time, and finding information about Xenotilapia tenuidentata proved to be a challenge. It quickly became clear that few aquarists hosted so far, "tenuidentata" in their tanks (therefore the residual data on the network). There are also no professional literature, and "pulling" information from the authorities, experts of the lake, or those involved in trapping the fish, usually ended in a fiasco. Despite all the adversity, we decided to write this article. It is an attempt to collect and systematise available information on this unpopular among aquarists cichlid from the Lake Tanganyika. We would also like to share with Readers our first experience of breeding.

Holotype (up) and paratype (down) of Xenotilapia tenuidentata (Takahashi, 1997)

Systematic interpretation
     Xenotilapia tenuidentata was caught by Poll in Vua Bay (another name is M'vua) in the Democratic Republic of Congo (formerly Zaire) 12 March 1947, then in 1951 first described. Holotype: MRAC 109884, sex unknown, 49.0 mm SL. Paratypes: MRAC 109885-904 (20), 48.7 - 53.7 mm SL, then harvested as holotype, BMNH 1960.9.30.7998-8014 (17); IRSNB 315 (17).
     In 1986 Poll created a new genus of Microdontochromis and classified to it "tenuidentata" as the only species. This separation was based on morphological and anatomical analysis. In 1997, Takahashi, Yanagisawa and Nakaya classified to this genus newly described species Microdontochromis rotundiventralis (now Xenotilapia rotundiventralis). In 2003, Takahashi joined microdontochromises to genus Xenotilapia  (tribe Ectodini). According to Koblmüller (2004) "tenuidentata" is the closest relative of Xenotilapia spiloptera, and not as it seemed to Xenotilapia rotundiventralis, which represents an independent line in the radiation tree of genus Xenotilapia. 
     The name "tenuidentata" comes from the words tenues dents, which are small teeth . Besides the name Xenotilapia tenuidentata (accepted name), are also common synonyms: Microdontochromis tenuidentatus, Xenotilapia tenuidentatus.
     International Union for Conservation of Nature (IUCN) has listed  X. tenuidentata to the Red List of Threatened Species, as  LC (least concern), which is least endangered (2006).

Place of occurrence
     "Tenuidentata" is endemic species for Lake Tanganyika. Widespread on the west bank of the Democratic Republic of Congo. According to Thomas Andersen (cichlids.akvariefisk.dk) it can be found throughout the DR Congo, Burundi and parts of Tanzania. However, according to Konings (2005) and Mierzenska (2009) this species occurs in whole lake area. These differences can probably explain the constant migration of fish, and seasonal occurrence of species in some locations (information obtained from M. Buckland).
     There are no known geographical variations Xenotilapia tenuidentata. In the photos in "Back to the Nature", we can admire the specimens from Cape Tembwe (DR Congo) and Mzwema (Zambia). Sample locations can also be found in scientific studies: Vua Bay (DR Congo), Katoto and Mpulungu (Zambia).
     "Tenuidentata" creates large (from 500 to 2500 individuals), single species, slow-moving shoals. We believe that, as in the case of "rotundiventralis" about 40% of the group are incubating females (Takahashi, 1997, information provided by E. van Ammelrooya and R. Krütera). X. tenuidentata occurs in the water column (at depths from 5 to 20-30 m) over sandy or muddy bottom. You can also find information about the occurrence over grassy bottom of the lake, in the transition zone or in the shallows. According to Takahashi (1997) "tenuidentata" (like "rotundiventralis") never settles on the bottom, at least during the day. But at night they are lying on the sand or on the rocks (information provided by E. van Ammelrooy).

Xenotilapia tenuidentata - female

Xenotilapia tenuidentata - male

Physique
     Tested by Poll individuals achieved sizes from 4.87 to 5.37 cm. According to Konings (2005), males reach 8 cm and females 6 cm. Floating in our tank adults are about 7-8 cm (the difference in size of male and female is insignificant). Lack of sexual dimorphism. Body of "tenuidentata" is highly elongated. Upper and lower head profile is slightly pointed. Eyes small (34-39% head length), round. Snout is short with a mouth subterminally mannered, slightly curved upwards. The jaws have only one row of teeth. There are two lateral lines.

Table1.The most important dimensions of Xenotilapia tenuidentata (Takahashi, 1997)     

Table 2. X. tenuidentata in comparision to X. rotundiventralis

*according to Konings (2005)
**according to destin-tanganyika.com

     There are several features that distinguish X. tenuidentata and X. rotundiventralis (see Table 2), but the most visible is the difference in coloration of the body. "Tenuidentata" has silver-gray body with a delicate bluish dots lines and dark markings (colored dark brown and even black). Markings can occur throughout the body of fish and have a different form - spots or vertical stripes. The most characteristic is the spot located at the base of the tail and second, relatively large, appears in the middle of the length and height of the fish. These markings can appear and disappear depending on the mood of the fish. All "tenuidentata" fins are transparent. On the dorsal fin there are stripes, and their color depends on lighting if the angle of light can be orange, brown or black. The first two stripes run along the dorsal fin to about 2 / 3 of its length and then bend toward the base of the fin. One of them is located halfway of the fin height and the other in the outermost part of it. The remaining stripes are located at the rear of the fin (1 / 3 of its length), and are much shorter and take the shape of the arc. Similar markings may appear on the tail fin. Other fins don't have patterns. Pelvic fins have soft white border. The outer part of the anal fin has a bluish tint. On the opercolo is a shimmering point, which can change color from silver to blue glow, through orange, and black (on the body of the fish appear three distinctive dark spots on the opercolo, in the middle of the trunk and base of tail).

Xenotilapia tenuidentata - courting

Reproduction
     Xenotilapia tenuidentata species is monogamous. According to Fitzpatrick (2009) is a representative of mouthbrooder (ie the species which incubate spawn and fry in its mouth; mouthbrooder), buccal fertilization (the female takes the eggs to the mouth and there it is fertilized) and biparental care ( for care are responsible both parents). To minimize the chance of cannibalism during the incubation of juveniles, female prefers well-nourished males. Incubation lasts about 3 weeks. According to Takahashi (1997) to the size of 6 mm only female incubate fry, and then both parents. Young during the incubation can take food. After released from the mouth the fry creates a nursery of young of other species such as Perissodus microlepis, Lepidiolamprolous elongatus (we think that there is no difference from the "rotundiventralis"). These groups operate much closer to the ground than adults.
     In scientific publications (Koblmüller, 2004), in books (Konings, 2005) and network (tanganyika.ru), you can also find information about that X. tenuidentata, is a species belonging to the maternal mouthbrooder, for which the care of offspring and fry has only female. It seems that this statement is not true.

Nutrition
     According to Poll "tenuidentata" feeds on small crustaceans, larvae, and unicellular and filamentous algae . Sturmbauer (1993) claims that it only gets zooplankton, while Konings (2005) says that it feeds both zoo and phytoplankton (as distinct from X. rotundiventralis, which according to the author feeds only on zooplankton). In the network it s often referred to as an omnivorous species. RIL (the length of the intestine to the total body length) 0,6:1.

Tank
     Aquarium for group X. tenuidentata should have a significant area of ??open water and minimum dimensions of 100 x 50 x 50 cm. In our view, a smaller tank can be suitable only when holding a selected pairs. In the case of this species is important not only the surface of the bottom, but the height of the tank, because they are not typically bottom fish. The occurrence of rocks and plants is neutral. Water parameters typical for fish from Lake Tanganyika.

Company for X. tenuidentata
     This is a very peaceful fish. They do not show aggression within their own species, and interspecies. They can stick with many representatives of Tanganyika, among others: grammatotria, lestradea, cardiopharynx, cyathopharynx or ophthalmotilapia. At Tropheus Tanganika company they swam in the aquarium with Reganochromis calliurus, Tylochromis polylepis, Gnathochromis permaxillaris, Xenotilapia nigrolabiata "Red Princess", Xenotilapia caudofasciata. In our tank, "tenuidentata"; swims with Limnochromis auritus, A. sp. "Compressiceps Shell" and Paracyprichromis brieni Kitumba. We do not recommend the connection of active floating tropheus and petrochromises. 

Xenotilapia tenuidentata - mouthbrooding female

Breeding experience
     Buying group of wild caught Xenotilapia tenuidentata we expected that most of the time they spend in the water column. However it soon proved that as they readily spend time in water column, they also reside in the depths of the sand, both day and night. Gerd in the forum cichlidae.com described similar behavior in his tank. According to him, "sat" on the bottom is characteristic for "tenuidentata" as opposed to the representatives of "rotundiventralis". Here is the first non-compliance with the available information on this species.
     Fish do not have problems with the collection of food, both from the depths, as well as from the ground. They willingly eat the plankton, artemia, cyclop, daphnia, and also artificial food with sufficient granularity (remember that their mouth is small).
     Shortly after arriving in our tank males "tenuidentata" began to present its strengths against females. Sailed with outstretched fins, inflated dewlaps, outdistanced competitors. After a while one of the females chose a male and began to respond to his advances, just picked a couple. Unfortunately we hadn't an occasion to watch the spawning, but from the information that can be found on the web, we know that probably nobody saw it. Most likely, spawning took place on the sand, and eggs were fertilizated in females mouths. For the first few days the eggs and fry were incubated by female. Every day we watched her expanding throat. One day the female started to draw nourishment from the ground. We thought that babies were eaten, but quickly noticed that they were simply given to male. Since then, nearly every day, parents passed the fry, and sometimes it was also possible that some kids wore female and part male. In this way another myth about this species has been overturned, and the information provided by Koblmüller (2004) and Konings (2005) revised. An interesting observation described Estelle on the forum cichlidae.com - parents when passed kids "mistake" and instead each other they pass another part of the juvenile other female of the group. This behavior is common in nature, but it does not seem purposeful action, but rather a "mistake" of fish. In our tank we did not observe such behavior. Incubation lasted for about 3 weeks and then the young were released. We are not able to give a specific number of kids, and the data that can be found in the literature and on the Internet vary widely - from 5 (Konings, 2005) to 20 (cichlids.akvariefisk.dk). It seems that as always the truth lies somewhere in the middle.   
     Another information about the X. tenuidentata that required verification, concerned the number of "tanuidentata" in the tank. According to Konings (2005), this species can be kept in pairs or small groups in an aquarium with a capacity of 100 l. We decided to compare the behavior of fish in aquariums of various capacity. Initially, the group of these fish went up to 375 l aquarium, where they swam with  Limnochromis auritus, A. sp. "Compressiceps Shell" and Paracyprichromis brieni. Fish had no problem with acclimation, did not show aggression inside and outer-specific, matched pair held a series of spawnings. Because in this multi-species tank there was no chance for rear the offspring, we decided to move a pair "tenuidentata" to 112 l, monospecific tank. Although the fish is still regularly coming up to spawn, we can not fully observe their behavior. The male did not adore so intensely females, the patterns on its fins were less visible. Often on the whole body of fish appeared dark marks, showing considerable stress. Fish did not swim around the tank, usually held in the rear. These behaviors have changed again after returning the fish to 375 liter aquarium. Our observations indicate that X. tenuidentata best kept in groups of at least 6-8 pieces. However, do not forget that in nature they occur in depths in large groups, so the bigger tank and more individuals in the shoal, the better.
     We hope that this article will encourage further fishkeepers to breeding X. tenuidenata at home biopsies of Tanganyika.

Xenotilapia tenuidentata - a couple

Acknowledgments
    We wish to thank Evertowi van Ammelrooyowi and Marta Mierzeńska for providing information about X. tenuidentata.

References

Fitzpatrick J. L., Montgomerie R., Desjardins J. K., Stiver K. A., Kolm N., Balshine S., 2009, Female promiscuity promotes the evolution of faster sperm in cichlid fishes, PNAS 106(4): 1128-1132 (SI Methods).

Koblmüller S., Salzburger W., Sturmbauer C., 2004, Evolutionary Relationships in the Sand-Dwelling Cichlid Lineage of Lake Tanganyika Suggest Multiple Colonization of Rocky Habitats and Convergent Origin of Biparental Mouthbrooding, J. Mol. Evol., 58: 79-96.

Konings A., 2005, Back to Nature. Przewodnik po świecie pielęgnic z Tanganiki, Fohrman Aquaristic AB – Tigra System Polska, Piaseczno.

Mierzeńska M., 2009, Rodzaj Xenotilapia Boulenger, 1899, Subtelne królowe stref dnnych, Tanganika MAGAZYN 6: 8-22.

Sturmbauer C., 1993, Meyer A., Mitochondrial Phylogeny of the Endemic Mouthbrooding Lineages of Cichlid Fishes from Lake Tanganyika in Eastern Africa, Mol. Biol. Evol. 10(4): 751- 768.

Takahashi T., Yanagisawa Y., Nakaya K., 1997, Microdontochromis rotundiventralis, a new cichlid fish (Perciformes: Cichlidae) from Lake Tanganyika, Ichthyol. Res., 44 (2): 109-117.

Websites

http://www.fishbase.com/summary/SpeciesSummary.php?id=8640
http://www.cichlidae.com/gallery/species.php?s=1966
http://www.cichlidae.com/forum/viewtopic.php?f=23&t=3402
http://www.tanganyika.ru/fishdesc.php?&fid=215
http://myfish.akvamalawi.com/fish_show.php?type=current&idfish=307&idvariety=0&povod=search
http://cichlids.akvariefisk.dk/species/show/?Name=Xenotilapia_tenuidentata
http://www.destin-tanganyika.com/Galerie/page-xenotilapia- tenuidentata-microdontochromis.htm