Photograph 1: N.virgatus from Fula A Zarga, Western Kordofan, Sudan, wild male raised from eggs encapsulated in mud collected by Mohamed Abdu Ibrahim on November 21st 1998. - {Photograph: Mich De Mey}
	Figure 1: Nothobranchius virgatus, Holotype male 45.0 mm SL from Jebel Megeinis, Southern Kordofan, Sudan {J. Chambers; J. Fish. Biol. (1984) 25, 508}

virgatus = Derived from the Latin word "virgatus", meaning "striped".

Chambers, J. - 1984 - A new Nothobranchius species (Teleosti, Cyprinodontiformes, Aplocheilidae) from the Sudan - J.Fish.Biol. (1984) 25, 505-513, 1 tab., 2 figs.

The presence in the Sudan of a Cyprinodont belonging to the genus Nothobranchius originating from Jebel Megeinis in Kordofan Province was first noted by H. Sandon in an addendum to his book "Fishes of the Sudan" (Sandon, 1950). In 1981, R. Bailey of the University of London collected specimens in the Sudd swamps, which appeared to Chambers (1984) to be conspecific with those from earlier samples.

The discovery of N.virgatus in Sudan, and more specifically in and around the White Nile River system considerably extends northwards the northern distribution boundaries of this genus in sub-Saharan Africa (Figure 3).

1. Hafir (=large manmade water reservoir for the storage of rain and run-off water for the dry-season) N° 1 & 2 at Jebel Megeinis, Kordofan Province (presently Northern Kordofan State), Sudan, 11°57'N-32°06'E.
2. Khor Morung, Kordofan Province, Sudan, 10°32'N 31°03'E (presently probably in Southern Kordofan State).
3. Waterhole at Rigr el Fula (probably Rahad el Fula for Chambers (1984), 11°38'N 28°28'E, in present Northern Kordofan State).
4. Roadside ditches near Maar, north of Bor, Sudan, 6°45'-7°00'N 31°25'E (presently in Jonglei State).
5. Rain fed roadside pools between Jalle and Kongor, Sudd, Jonglei State, Southern Sudan (Bailey & Hickley, 1985).
6. Rest-pools at Fula A zarga and Khor Mahada Mulaha about 15-km southeast of Rijl el Fula, Western Kordofan State, Sudan.

Counts and measurements made by Chambers (1984) during the original description of the species yielded following data:

Meristic data as published by Chambers (1984) are presented in Table 3.

According to Chambers (1984), N.virgatus belongs to the group of species having a pale to white submarginal caudal band (recent material collected from Fula A Zarga showed it to be sky-blue) and are recognised by Radda (1969) to belong to the subgenus Zononothobranchius. This group also includes N.rubroreticulatus (Blache & Miton, 1960) which occurs in Lake Chad Basin and a group of species represented by N.taeniopygus (Hilgendorf, 1891), which is widespread in Uganda, Lake Victoria drainage and the White Nile drainage system. Wildekamp (1980) points out that the position of the dorsal fin origin over that of the anal fin or slightly in front of it, is characteristic of the species relation to N.taeniopygus and, according to Chambers (1984), it is undoubtedly with these species that the affinities of N.virgatus lie.

The description by Chambers (1984) is based on a holotype and 45 specimens, half-originating from the Sudd and half from Kordofan Province. Specimen sizes range from 24.00 to 54.00-mm SL. Ancient specimens are deposited in the British Museum (Natural History), London; recent material is deposited in the Koninklijk Museum voor Midden Afrika, Tervuren, Belgium.

Male of 45.0-mm SL collected from hafir No.2 at Jebel Megeinis, Kordofan Province, Sudan, 11°57'N-32°06'E, collected by P. Howell in January 1950. BMNH 1983.4.7.3

According to Chambers (1984),

• Four males, 35.5 to 45.0-mm SL collected from Hafir No.2, locality and collection details as holotype. BMNH 1983.4.7.4-7.
• One female, 41.0-mm SL, locality details as holotype, collected H. Sandon, December 1956. BMNH 1983.4.7.8.
• Two males, both 44.0-mm SL, two females 44.0 and 48.0-mm SL collected from Hafir No. 1, locality details as holotype, collected December 1950. BMNH 1983.4.7.9-12.
• One male, 54.0-mm SL, one female, 29.0-mm SL collected from Hafir No. 1, locality details as holotype, collected 1950. BMNH 1983.4.7.13-14.
• One male, 40.0-mm SL, Hafir No. 1, locality as holotype, collected 1950. BMNH 1983.4.7.15.
• One male, 39.0-mm SL, Hafir No. 1, locality as holotype, collected 1950. BMNH 1983.4.7.16.
• One male, 35.0-mm SL, Khor Morung, Kordofan Province, Sudan. 10°32'N 31°03'E, collected by Irwin 1950. BMNH 1983.4.7.17.
• One male, 31.0-mm SL, Khor Morung, locality and collection details as above. BMNH 1983.4.7.18.
• Two males, 30.5 and 35.0-mm SL, Khor Morung, collected by Irwin, 19 July 1951. BMNH 1983.4.7.19-20.
• Three males, 27.5, 28.0 and 32.0-mm SL, two females 25.5 and 32.0-mm SL, water hole at Rigr el Fulla (probably Rahad el Fula) 11°38'N 28°28'E, collected by C. Amirthalingam, 22 November 1965. BMNH 1983.4.7.21-25.
• Nineteen males, 25.0 mm to 33.0-mm SL, and five females 24.0 to 31.0-mm SL, from roadside ditches near Maar, north of Bot, Sudan, 6°45'-7°00'N 31°25'E, collected by R. Bailey, 1981. BMNH 1983.4.7.26-49.
• Other material: two specimens recovered from the stomachs of birds caught at Jebel Megeinis, Hafir No.1, April 19, 1953. The fish were too distorted and eroded to take counts and measurements from, but the colour pattern was still recognisable.

According to Chambers (1984), N.virgatus presents a typical relict distribution in that it is known from six localities having no direct connections with each other. Two of the localities are located in and around the foothills of the Nuba Mountains. Two others are located far more to the East and two others are some 800 kilometres more south, in the Sudd swamp, through which the White Nile flows (Figure 3).

According to Chambers (1984), the disrupted nature of the distribution of N.virgatus can best be explained on the grounds that the White Nile was, in the past, at a higher level than at present so that the localities where the species occurred were connected. Wickens (1975) proposes that, during a period from 12.000 to 7.000 years BC, rainfall in the central Sudan was 2 to 3 times greater than at present and that lakes were formed on the White Nile below Khartoum, possibly impounded by Blue Nile sediments at the confluence of both rivers. Berry (1976) reported that two terraces, at 386-m and 382-m, relicts of ancient lakes, occur on both banks of the White Nile in this region. Tributary watercourses would have fed these lakes, rising as a result of increased rainfall on the Nuba Mountains. They probably would however not have been extensive enough to physically join the various N.virgatus localities. Khors in this region, now seasonal, might have been more permanent, so that links between parts of the area where N.virgatus was found would have been possible.

However, fishing trials carried-out in various Hafirs provided us with additional field observations, which could help explain the present distribution pattern of N.virgatus in central Sudan. Drying hafir silt/mud glued firmly onto hooves and hair of drinking cattle and sheep herds, which move from one waterhole to the next during their annual east-west migratory movements. Cattle and wild animals can easily ferry hafir mud, and thus Nothobranchius eggs, over vast areas. There is thus apparently no need, at least in the dry Sudanese savannah plains, to rely on possible water connections in order to explain the present distribution pattern of Nothobranchius species.

The survival of Nothobranchius populations is made possible by the development of a resistant chorion around the egg, which enables it to resists not only to a certain level of desiccation during the dry season but also to withstand the pressure exercised by the contracting and cracking silt/mud. Also the ability of the embryo to enter into a phase of arrested development at a stage in ontogeny, in response to environmental conditions, plays a role in this survival struggle. The seasonal nature of the life-cycle means that no more than temporary water is required at the breeding localities.

The progressive reduction of average annual rainfall, in northward direction along the White Nile, can be red from Table 1. This table indicates that a relation between rainfall and N.virgatus occurrence in Sudan could possibly be established. The area north of Renk offers only very limited opportunities for naturally occurring habitats, which can keep water long enough for the species to thrive. Between Renk and Malakal, and more even so further south, the more abundant rainfall also provides for more opportunities and it is this northern region that the type specimens of N.virgatus where collected in the fifties. Recent pronounced drought periods (seventies and early nineties) in Sudan and Ethiopia must have altered the distribution pattern, pushing its northern limits more southwards.

From Table 2, it is also apparent how far extreme air temperatures (during the dry season period) in this area can be. The values occurring in the area located between Kosti and Bor could possibly be considered as the natural temperature range for N.virgatus in central Sudan.

Year-in year-out, the water in the Hafirs is exposed to the burning Sudanese sun. There is hardly any protective vegetation cover over these plains. During the winter months (December-February) temperatures can also drop significantly whilst during the months preceding the rains, May to July, temperatures can easily reach above 40°C (Table 2). Only the rainy season, from August to November, brings some nicer weather.

The more northerly collected specimens came from Jebel Megeinis, at 11°57'N 32°06'E, in former Kordofan Province (since 1984, provinces have received the status of state within the Republic of the Sudan). Jebel Megeinis is a 150-m high hill located at the three-state junction point where the present States of Northern Kordofan, Upper White Nile and Southern Kordofan meet. It is situated some 175-km south-west, or after a 3 and 1/2 hour sandy and bumpy road drive, from the town of Kosti. The location is notable for its hydrological isolation. It lies in the middle of a large topographically blank space in the Sudan; "there is no feature important enough to be mapped neither between the Nile and Nuba Mountains nor for a great distance north or south except the hill or Jebel itself" (Sandon, in litt.).

The collecting sites at Jebel Megeinis consisted of two hafirs or tanks excavated to catch the torrents that come off the 150-m high hill and the surrounding land. Sandon wrote of Hafir N°1 that "it gets its water from Khor Baida which has its main source far away in the Nuba Mountains near Jebel Tisia". Using the 1949, 1: 250000 scale map of the Anglo-Egyptian Sudan, sheet 668, Chambers (1984) found no trace of such a water-course nor of any drainage in the area and believed it to be more likely that Howell (in litt.) was correct in attributing the source of the water in Hafir N°1 to the hill Jebel Megeinis itself. Howell also reported that Hafir N°2 catches water from the Tegali Hills, but Chambers was also unable to trace this source-locality.

Hafir N°1 was dug in early 1949 and already filled with water during the rainy season of that year. In November 1949, it was found to be stocked with small fish. These form the subject of the addendum to Sandon's "Fishes of the Sudan"(l950) in which he wrote "Two further fish, both Cyprinodonts, occur locally. Cyprinodon dispar, common on the Asiatic side of the Red Sea, has been established for many years at Khor Arba'at, near Port Sudan. Recently a hitherto unknown species of Nothobranchius ('Fundulus') has appeared in a next Hafir near Jebel Megeinis, its natural home being presumably somewhere in the Nuba Mountains"(Sandon, 1950)". In 1951, the fish had disappeared from Hafir N°1 but some were present in Hafir N°2 from which Howell collected several specimens.

On 18th March 1998, we were able to visit Jebel Megeinis, the type locality of N.virgatus. Along an earthen track, leading from Kosti to Jebel Megeinis, we found after about 45 minutes driving, in the vicinity of the abandoned village of Etieshana ("Thirsty village" in Arabic) the first, yet completely dried, Hafir (Figure 8, Figure 9). Further on our way we passed the villages of Ribeish, Birka, Akaf and finally reached Jebel Megeinis.

Ribeish and Birka (Arabic for "depression") are localities, which both are characterised by the presence of a 1,000 to 1,500 m long and 25-50 m wide ancient and partially filled meandering depression (=Khor). They lie in the shadow of 15 to 20-m high green Acacia sp. trees under which cattle were hiding against the burning mid-day sun. This luxurious vegetation contrasted sharply with the overgrazed naked surroundings. The bottom of these depressions consisted of the same clay layer found in all visited Hafir's. In Ribeish, herdsmen also extracted water from the depression through a waterhole. Signs are that during the rainy season, a 1-à 2-m thick water layer in which possibly N. virgatus could thrive covers these depressions. However, our visit coincided with the dry season.

On the way to Jebel Megeinis, but also on several other occasions during our field visit, we observed small twisters during the hot mid-day hours. Such a twister happened to blow right through the first visited Hafir. It collected and carried reasonable amounts of bottom material and blew it up in the air, over a distance of several kilometres. From cysts hidden in mud samples collected in two different dried hafirs we obtained freshwater Artemia-like creatures. Similar creatures were obtained, some 20 years earlier, in a rain-pool in Senegal, on the other side of the African continent, between Mbour and Joal, at Nyaning. Twisters must thus represent a second manner by which eggs/cysts possibly get distributed over vast areas and from one water location to the next. However, with this dispersal method, chance plays a much more important role than attached to hooves and hair of drinking herds.

In 1952, the collecting site at Jebel Megeinis consisted of two hafir's, about 100 (l) x 75 (w) x 6 (d) m, which served to collect the run-off water from the hill. The Sudanese irrigation department, which has the responsibility to dig and regularly maintain drinking sites, estimates that Hafirs and depressions collect annually some 10 to 15-cm silt and mud from run-off and soil erosion. Over the passed 46-years period, a mud layer of between 4,6 to 7-m could thus have been added to the Hafir's bottom. In addition, the plains in the immediate vicinity of Jebel Megeinis are used for agriculture (sorghum, millet and sesame - Figure 10) which also favours soil erosion. The depression around Birka must thus have been deeper in earlier years.

Figure 11: The first Hafir, located at the right site on entering the town of Megeinis had already dried-up. From this Hafir soil samples were collected; March 1998 {Photograph: Bellemans}

Our observations indicate that Hafir N°1 and 2, both directly receive their water from run-offs of the hill itself as they were build close to the village (which is presently separated by only about 700-m from the foot of the hill). The depression at Birka, 9 km before reaching Jebel Megeinis, can not be considered as the source of the water in the Hafirs as it lies somewhat lower. Inhabitants and elders of Jebel Megeinis confirmed this. However, the question remains as to how, in the past, lungfishes (Protopterus aethiopicus) and Nothobranchius got into these 2 Hafirs. Above-mentioned explanation on the ancient existence of larger flood areas in the region could account for this.

The village of Jebel Megeinis has continued to grow and in March 1998, 46 years after Howell, there are now 5 Hafirs; a first but also small one (Hafir N°5), located on the right side of the road when entering the village, had already dried-up (Figure 11). In our excitement of having reached the place, some bottom soil samples were collected. The other four hafirs, under which hafir N°1 and 2 reported by Sandon and dating back to the early fifties, lie on the south-eastern edge of the settlement and hill.

Hafirs N°1 and 2 were partially filled with silt and less deep. They were already completely dry (Figure 12) whilst Hafir N°3 (dug out in 1970) and N°4 (constructed in 1992) presented respectively very limited and plenty of water (Figure 13, Figure 14).

Both recent hafirs had also been interconnected to each other through a pipe system running underneath the separating earthen dike. In this way they can fill simultaneously but will empty one after the other. Because of its limited depth, Hafir N°3 contained in March 98 only a water flake of about 5-m² and 4-cm deep. Only a couple of water scorpions and water bugs could still survive. Also from this Hafir we collected some humid cracking bottom silt, in the hope to collect hypothetical Nothobranchius eggs (Figure 13).

Hafir N°4, constructed in 1992, was about 150-m in length, 100-m in size and 15 to 20-m deep. It still contained about 2 to 2.5-m of water, enough to provide men and herds with sufficient water until end of Mai. The water was murky and brownish with a 5-cm transparency. It was relatively fresh, I estimate between 20 and 22°C, because of the important evaporation under hot and windy conditions (Figure 14, Figure 15).

This hafir was fished with a 50-m long but only 1-m deep net. Only about fifteen 60 to 70-mm long black carnivorous water insects [giant Hemipteran Lethocerus sp.] came to the surface. Because of the presence of floaters on the net's headrope, it could not reach the bottom of the reservoir. If somewhere in Jebel Megeinis there are still N.virgatus occurring after the drought periods of the seventies, which also had disastrous results in neighbouring Ethiopia, it will probably be in this Hafir. Local people pretend that even during these drought periods, the hafirs in Jebel Megeinis always contained some water. One will thus have to retry once luck in times of lower water level or with a deeper net. People in Jebel Megeinis didn't know about the occurrence of these little blue-greenish fish in the reservoir. However, they mentioned the existence of lungfishes, Protopterus sp. (="Um Quru" in Arabic), in the reservoir which they used to throw out. They were also not used for human consumption. However, we did also not discover mosquito larvae in the Hafir.

Another locality, Jebel Morung, at 10°32'N 31°03'E, where flows Khor (temporary watercourse) Morung, supplied several specimens of N.virgatus collected by Irwin in January 1950 and July 1951, together with Clarias sp. and Protopterus sp. but not from the same bodies of water. No other locality details are directly available but sheet 66E of the mentioned map reveals a number of small pools and watercourses.

The third locality, recorded by Sandon's colleague at the University of Khartoum, the late Pakistani C. Amirthalingam, as "Rigr el Fulla" (meaning "leg" (Rigr) or "end of waterpool" (Fula)"), at 11°48'N 28°24'E, could not be traced by Chambers and, according to my Sudanese colleagues, does presumably not exist because of the improper and insignificant meaning. On sheet 65C of the above map, however, Chambers found, much more to the west, at 11°38'N 28°28'E, the place named Rahad el Fula. He further wrote, "there are khors at this site and that in addition the word "Rahad" means "stagnant pool". Amirthalingam collected in 1965 several specimens from this uncertain "Rigr El Fula" in 1965.

Our Sudanese colleagues stated that the locality of "Rigr El Fula", most probably corresponds to the locality of "Rahad El Fula", which can be found much less far to the west of Chamber's locality 11°48'N 28°24'E. This "Rahad El Fula", also named "Rahad" or "Er Rahad", locality is in addition less isolated from possible water connections or waterways.

The "Rahad El Fula" or "Er Rahad" locality that we managed to visit during our February 1998 trip lies about 12°08'N-30°40'E, also somewhat more northerly and, in addition, along a very long depression (Figure 16). The Abu Habl Khor depression runs along the northern flank of the Nuba Mountains and runs eastwards until it reaches and joins the White Nile. Somewhat northeasterly of the place Tendelti, the depression fades away and it course disappears in the sandy bottom where it displays a temporary character. Only during years of abundant rainfall (as in December 1998) the connection with the White Nile is filled with water. Khor Abu Habl finally joins the White Nile near the town of El Fashashoya.

On March 19^th, 1998, we could visit this interesting depression which brought us to about 30 km of the foot of the Nuba Mountains. Khor Abu Habl depression crosses the road leading from Kosti to El Obeïd on two occasions, the first at Tendelti (Figure 16) and the second in Rahad (Figure 16). We drove over a dry desiccated, at times sandy, but still bushy plain until we reached Tendelti (Figure 17, Figure 18). This hafir had been excavated in the bedding of Abu Habl depression, about 300-m on the right side of the bridge over khor Abu Habl, in the direction of Rahad. Fishing in this hafir was left for the return trip, but as will appear, this was not a judicious choice. On the way back from Rahad to Kosti, about 375 km, we had an exploded front tyre. Reparations took the necessary time and on arrival at Tendelti's hafir, it was already dark and too late to throw the net.

In Rahad we visited the freshwater reservoir build somewhere in the late fifties by damming the upper part of khor Abu Habl. This site was visited in connection with the possibility of improving the fishery on the reservoir after the introduction of Tilapia nilotica during the sixties. According to one of my counterparts who was stationed in Rahad as veterinarian during the seventies, the most common species caught during those years in the Khor comprised lungfish (Protopterus sp.) and catfish (Clarias sp.). They were hardly any other species present in this previously temporary depression. The occurrence of these species is typical for waters with a pronounced intermittent character and with a temporary connection with the White Nile (Figure 19, Figure 20).

The consequences of damming the depression are still visible in the numerous tree trunks still sticking out of the water surface in the middle of the reservoir. These trunks belonged to giant Acacia nilotica trees as one can find along most depressions and aquifers in the area. The Rahad reservoir contains water during the entire year and has thus lost its intermittent character, although important changes in water levels can be observed as the seasons pass by.

There is evidence that khor Abu Habl depression constitutes the area in which Amirthalingam collected his specimens of N.virgatus in 1965. During that period the tarmac road to El Obeïd had not yet been completed, only the portion up to Rahad. During the late fifties/early sixties part of Khor Abu Habl was also impounded near Rahad in order to retain drinking water for the town and for migrating herds coming from western Sudan. Already in those days, some thoughts were given to the introduction of new species into the newly formed reservoir in order to improve on the poor initial species diversity and to increase production of edible species. It must then have happened that Amirthalingam paid a visit to this area in order to study the actual species and evaluate the possible impact of introducing new species.

An additional reason to accept that this could be the area where Amirthalingam collected N.virgatus can be found in the possible distribution of Nothobranchius eggs. As mentioned in an earlier part, the numerous twisters which occur around the Nuba Mountains and the sticky mud which glues eggs to hooves and hair of herds which move from one hafir to the next, could possibly account for the dispersal of Nothobranchius in the area. In relative terms and in bird's flight Jebel Megeinis is also not that far away from khor Abu Habl (Figure 16).

The sites from which Bailey collected in 1981 extend from 6°45' to 7°00'N 31°25'E, north of the town of Maar (itself north of the much larger town of Bor - Figure 3) and consist of a series of roadside ditches containing turbid water. These specimens were collected by electro-fishing.

The fifth area from where N.virgatus was collected in 1982 (Bailey & Hickley, 1985), between Jalle and Kongor, north of Jonglei in southern Sudan, comprises rain fed pools and roadside ditches created by human intervention. These collecting sites were associated with the drying-up and embankment of roads, earth extractions in support of more permanent installations. Bailey & Hickley (1985) mention that the shape and size of these pools differed greatly together with their aptitude to retain water. In 1982, the heavy rains started in April and some waterpools appeared in May and June. Many were however subject to a partial or total desiccation before reaching, in July, a more stable phase, which lasted until December or January 1983 (Bailey & Hickley, 1985).

Amongst these habitats, N.virgatus presented an unequal distribution. It was absent from those habitats which developed thick emerging vegetation, but were present in those pools which had an open central area and grassy shores. Water characteristics at capture time were (Bailey & Hickley, 1985): milky coloration; very high turbidity with values of 235-560 units of formazine turbidity, compared to 38-79 units in the Nile at the same period; conductivity of 118-132 µ-Siemens per cm at 25°C, which is relatively low compared to other habitats in the Sudd swamps; pH of 6.5 to 6.9, generally lower than in pools receiving water from the Nile river where values of 8 were recorded.

These pools were rich in Rotifers and small planktonic crustaceans. Invertebrates encountered in these Nothobranchius pools included the Anostracoïd Branchiopod Branchinecta sp., molluscs and various insects, dominated by Hemipterans and Coleopterans. With the exception of a few lungfishes (Protopterus) and juvenile catfishes (Clarias), no other fish was captured in these pools. However, larvae of Amphibians were very common (Bailey & Hickley, 1985).

According to Bailey & Hickley (1985), in the Sudd area in southern Sudan, N.virgatus appears to be absent from pools with an annual or a direct link to the main Nile River system. They could only be found in habitats with variable hydrological regimes and situated next to the main riverbed. In 1982, these habitats were exclusively filled with rainwater. Pools linked to the main riverbed tend to develop dense vegetation and, when the water recedes, do contain numerous fish species amongst which several piscivorous such as Polypterus, Clarias and Channa. These habitats are also subject to heavy predation from waterfowl, rendering these habitats inhospitable to Nothobranchius.

Even in the isolated pools, N. virgatus was far from common and one rarely could find any other fish species in them. The giant Hemipteran Lethocerus sp., which reached a length of 70-mm, is here probably the most notorious predator of N. virgatus.

A sixth collecting site of N.virgatus in central Sudan was discovered during our third 1.5-month's mission (October-December 98), which coincided with the end of a very abundant 1998 rainy season. The locality of Rijl El Fula was discovered on a recent map issued in 1995. As a consequence of having subdivided previously large provinces into smaller units and of having raised them to the status of State within the Federal Republic of Sudan, the state of Western Kordofan was created with state capital the very small dwelling of Rijl El Fula.

Since we could not obtain the necessary permits to visit the area of Rijl El Fula, in Western Kordofan State, which according to Chambers (1984) supposedly represented the place where Amirthalingam collected 3 males and 2 females of N.virgatus in 1965, it was decided to send Mohamed Abdu Ibrahim, one of our Sudanese co-workers to visit the area and to search for N.virgatus.

Mohamed Abdu reached after 2 days minibus-travel Ar Rahad, west of Kosti, where he caught the once-per-15-days train to Nyala. After 2 additional days of very slow train journey from Ar Rahad to Rijl El Fula he could get down. The road between Ar Rahad en Rijl El Fula is not very safe these days due to activities of cattle thieves and rebels (these days nearly everyone in Sudan is armed). He had just 4 days to catch the return train.

Mohamed Abdu brought back 64 formalin preserved specimens (30 males and 34 females), collected in different quantities, from next to each other situated rest-pools. He also succeeded in bringing-back one live couple to Khartoum. This couple died however hours before we could intervene as it had suffered too much from the heat and from the far from ideal transport conditions. He also brought back some soil samples of hardened bottom mud from one of the pools.

Mohamed Abdu was sent back to the area in February 1999, only 3 months after he had collected the live N.virgatus specimens. He was then asked to collect some additional bottom mud and to make pictures from the area of collection with a disposable camera we had provided him with [figures 22 to 36].

Figure 24: The general area and the road leading to Fula a Zarga near Rijl El Fula. - February 99 {Photograph Mohamed Abdu }

The description of the collecting site where Mohamed Abdu caught N.virgatus in 1998 is given as: Fula (= rain pool) A Zarga (= blue), about 15 to 20 km south of Rijl El Fula, Western Kordofan state, in the district of Arragab Al Zarga (= blue neck) in an area overgrown with large trees and thorny bushes, in various rest pools situated near a larger meandering depression Khor Mahada Mulaha, on 21, 22 and 23 November 1998. According to the collector, this khor has no direct link with Wadi (= seasonally flooded riverbed) Al Ghalla that is drawn on the map (Figure 21).

Figure 25: Fula a Zarga area, large trees and high grasses on the drier parts and meandering depression without any vegetation cover in the lower parts. February 99 {Photograph Mohamed Abdu }

Figure 26: Fula a Zarga area - February 99 {Photograph Mohamed Abdu }

Figure 27: Fula a Zarga - February 99 {Photograph Mohamed Abdu }

Figure 28: Fula a Zarga, collecting site of N.virgatus February 99 {Photograph Mohamed Abdu }

Figure 29: Fula a Zarga, collecting site of N.virgatus in the undeep meandering depression without vegetation cover - February 99 {Photograph Mohamed Abdu }

Figure 30: Fula a Zarga, collecting site of N.virgatus in the undeep depression without vegetation cover - February 99 {Photograph Mohamed Abdu }

Figure 31: Fula a Zarga, collecting site of N.virgatus in the shadow of the trees February 99 {Photograph Mohamed Abdu }

Figure 32: 3 months earlier N.virgatus was caught here February 99 {Photograph Mohamed Abdu }

Figure 33: Some N.virgatus specimens were caught under these roots 3 months earlier. - February 99 {Photograph Mohamed Abdu }

Figure 34: Depression running into Khor Mahada Mulaha which takes the form of a channel. - February 99 {Photograph Mohamed Abdu }

Figure 35: Deeper part of the channel (Khor Mahada Mulaha) from where also bottom soil was collected. - February 99 {Photograph Mohamed Abdu }

Figure 36: Collecting soil in the Khor Mahada Mulaha in the hope to obtain N. virgatus eggs. - February 99 {Photograph Mohamed Abdu }

As accompanying species he collected various 12-cm long and with external gills equipped young Protopterus sp. of which one thrives in my tanks. There where also frogs present in the rest pools, which had a diameter of about 10-meters and a depth of 15 to 50-cm. The fish species in khor Mahada Mulaha comprised cichlids (Bulti), Protopterus sp. (Um Quru), Polypterus sp. (Debit El Hut), and Clarias sp. (Garmout).

Male: The description of alcohol preserved specimens, as given by Chambers (1984), indicates that male N.virgatus are characterised by about 12 russet-red stripes running obliquely backward and downward along every second to third transverse scale-row. These stripes do not always extend over the whole depth of the body and frequently they are also absent from the back and the belly. Close to dorsal and anal fins, the stripes run onto them. In several specimens from the Sudd, in the opercular and caudal peduncle regions there are shorter additional bars that form chevron patterns with the regular bars, as observed in males of N.cyaneus Seegers, 1981 and N.eggersi "blue" Seegers, 1982. The body is pale, almost white, with a dusting of melanophores. The pre-dorsal and occipital regions are spotted with brownish-black. The dorsal and anal fins are strongly barred with reddish-brown; the pelvic fins with a red bar proximally, black distally. The pectoral fins are pale. The operculum is barred with red and black. The caudal fin is pale with a thin dusky margin and submarginal white band. The belly is pale to white. There is a short vertical, dark bar through the eye; this is visible in very few specimens from the older, Kordofan, collections. The stripes are a little faded in specimens from Kordofan province though other pigments may have been more fugitive. The distal part of dorsal and anal fins of N.virgatus males are studded with contact organs.

According to Chambers (1984), the ground colour in fishes from Hafir N° 2, Jebel Megeinis is described (Howell, in correspondence with Sandon, 28 January 1950) as ranging from mackerel-green to paler green, but no trace of green is now apparent. The ground colour of live specimens collected by Bailey is a light buff-yellow. However, the colour of the water in which Howell collected is described by him as "a very bright greeny-blue", whereas Bailey says that his specimens were caught in murky water.

A colour photograph from freshly caught specimens collected between Jalle and Kongor, Southern Sudan, is presented in Bailey & Hickley (1985). These authors describe male specimens from the south as having a bleak brown-green to light yellow base colour. There are between 10 and 14 thin red obliquely and distally running lines over the sides, and irregular and shorter stripes forming chevron-like drawings over the operculum. Dorsal and anal are heavily spotted or red-brown barred. The caudal fin has a marginal black band on the apex and presents a central and submarginal lens-shape whitish spot. Pelvic fins are red with black spots. Pectorals are transparent. In both sexes, a vertical black stripe crosses the eye.

As we could observed from the last couple that died a few hours too earlier, the colour pattern of living specimens from the Fula A Zarga population appeared to be slightly different.

N.virgatus Males from the Fula A Zarga population possesses a body coloration that is of a general gold-bronze to very light mackerel green. Over the entire body, there are between 12 and 14 obliquely backwards running thin stripes. There is no black vertical band running though the eye. Some males present a hump-like structure at the height of head-body transition, others present a concave bend. There are numerous golden-yellow reflections on the scales over the flanks. The distal end of the operculum displays an orange to gold-bronze spot. The anal fin presents a spotted pattern comprising orange red, somewhat regularly placed spots. The distal part of the anal fin presents a yellow-orange extremity. The dorsal fin has a brown-red striped pattern. The thin red-brown stripes are separated from each other by whitish to yellow-golden bands. Along the distal part of the fin, these stripes go over into a stopped pattern. According to Mohamed Abdu who captured the live specimens, living males presented at the caudal fin extremity an incomplete submarginal light sky-blue band followed by a very thin red to dark red marginal band.

The females of the Fula A Zarga population are, like in most other Nothobranchius species, rather colourless, ranging from grey-brown to light brown over the backside with a few silver reflections along the lighter flanks. The ventral part is lighter. All fins are transparent. There is a light dusting of melanophores over the body. In some specimens, as in males but more light and less pronounced, there are a few backwards and obliquely running short thin bars.

All the Fula A Zarga specimens showed signs of heavy infestation with parasitic cysts over the entire body and the fins.

Bailey & Hickley (1985) analysed the stomach content of 30 specimens (8 juveniles and 22 adults) caught between Jalle and Kongor in 1982. From their investigations, it appeared that juveniles prey nearly exclusively on Copepods and Ostracods. The latter, together with Cladocerans, form the principal components of the digestive tube in adults. In general however, adults appear to have a more varied diet: 16 of them contained remnants of aquatic insects, mainly Dipteran larvae, Coleopterans and Hemipterans, and in 8 adults, insects formed the bulk of the digesting material.

Bailey & Hickley (1985) reported that from 24 mm TL onwards, all specimens could easily be sexed. Ovaries of 12 females, ranging from 27 to 39 mm total length (TL), were examined and showed to contain 1-mm diameter eggs and eggs at different stages of development, implying a fractional egg-laying process over an extended period. The total number of eggs ranged between 87 and 360 with an average of 175, highest numbers were found in larger females.

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