Pseudotropheus Demasoni Sp. Nov: a Sexually Monomorphic Cichlid from the Tanzanian Coast of Lake Malawi

ResearchGate See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/237091715 Pseudotropheus demasoni sp. nov: a sexually monomorphic cichlid from the Tanzanian coast of Lake Malawi ARTICLE ■ JANUARY 1994 DOWNLOADS VIEWS 74 124 1 AUTHOR: j£~’ Ad Konings ^ El Paso Community College 30 PUBLICATIONS 572 CITATIONS SEE PROFILE Available from: Ad Konings Retrieved on: 08 July 2015 MALAWI CICHLIDS Pseudotropheus demasoni sp. nov.: a sexually monomorphic cichlid from the Tanzanian coast of Lake Malawi Ad Konings Summary noted. Although it is obvious that the Ruhuhu River delta forms an impassable barrier to the Pseudotropheus demasoni sp. nov. is described from a small rocky reef in the Tanzanian part of Lake Malawi. Both northward spread of the cichlids at Pombo male and female exhibit a colour pattern consisting of dark Rocks, to the south the reef is separated from the blue bars on a light blue background. Such a coloration is not rocks at Lundu by a sandy beach a mere 6 km in known to occur in other female Mbuna. length. Nevertheless the communities at Pombo Rocks and Lundu differ considerably. Introduction Pombo Rocks is a rather small area (estimated at a few hundred metres in diameter) with a In October and November 1993 a preliminary maximum depth of 7 metres. In several places the survey was undertaken to inventory the rock- rocks break the surface, but most of the reef is dwelling cichlids of the Tanzanian coast of Lake submerged and lies about 500 metres offshore. Malawi. In Tanzania and in Mozambique this One of the species endemic to Pombo Rocks is lake is still called Lake Nyasa (sometimes written the subject of this formal description. It is a small as Nyassa), the old name given by Dr. David Mbuna which is readily noticeable when snorkel Livingstone. ling over the reef. It is, however, not abundant, Several fishes collected in the Tanzanian part of and therefore collection of this very desirable this large lake have already been described. In (aquaristically speaking) cichlid should be re 1925-26 Fulleborn collected specimens near Alt stricted to those specimens deemed necessary for Langenburg (now called Lumbila) and these its propagation in captivity. were described by Ahl in 1927. Staeck (1976) de The measurements were made in accordance scribed Pseudotropheus fainzilberi from M atema in with Barel et al. (1977), except for the depth of the Tanzania. Recently several exporters have col preorbital bone, which is taken as the length of a lected fishes for the aquarium trade in Tanzanian line from the centre of its orbital edge, practical waters and have made available most of the spe ly bisecting the bone (Trewavas, 1935; Eccles & cies that were seen during our survey (Lepel, Trewavas, 1989: 20, fig.3). 1993; DeMason, 1993). Although some Tanzanian rock-dwelling species are also found in Mala Pseudotropheus demasoni sp. nov. wian waters, most seem to be restricted to a northeastern distribution. Etymology Pombo Rocks, a shallow rocky reef about 15 km south of the Ruhuhu River delta, was found This species is named in honour of Mr. Laif to be inhabited by many different rock-dwelling DeMason (Homestead, Florida) without whom cichlid species, several of which were not found our preliminary survey could not have been at any other location along the Tanzanian coast. completed. Mr. DeMason, importer, exporter, As well as the few allegedly endemic species and breeder of cichlids, has greatly stimulated some geographical variation in other species was the keeping of cichlids in the USA. 24 The Cichlids Yearbook, volume 4 (1994): 24-27 © CICHLID PRESS Material examined Holotype: Koninklijk Museum voor Midden Afrika, Tervuren, No. 94-12-P-1. Male, 62.5 mm standard length (total length 77.3 mm); Pombo Rocks, Lake Malawi, Tanza nia; collected 7-11-1993 by author. Paratypes: Koninklijk Museum voor Midden Afrika, Tervuren, Nos. 94-12-P-2 to -5. Three males, standard lengths: 52.6, 57.7, and 63.4 mm (total lengths respectively: 62.8, 71.4, and 78.5 mm) and a female, standard length 44.3 mm (total length 55.0 mm); Pombo Rocks, Lake Malawi, Tanzania; collected 7-11-1993 by author. Diagnosis A small species of the genus Pseudotropheus with a unique coloration in females: blue-black bars on a light blue background. The colour pattern of males and immatures is indistin guishable from that of females. The species resembles Ps. saulosi (males only) in coloration and size but differs in having only four dark bars below the dorsal fin Pseudotropheus demasoni sp. nov. in its natural habitat at Pombo Rocks, Tanzania. © CICHLID PRESS The Cichlids Yearbook, volume 4 (1994): 24-27 25 whereas Ps. saulosi males have five or six. Moreo peduncle depth 1.1 to 1.3 times in its length. ver female and immature Ps. saulosi have a bright The gut length of an unregistered specimen (SL yellow-orange colour. Other species with four 49.9 mm) was 205% its standard length. bars below the dorsal (Ps. livingstonii, Ps. elegans, Ps. microstoma, Ps. lombardoi, and Labidochromis Distribution zebroides) are easily distinguished from Ps. demasoni on the basis of obvious differences in Ps. demasoni is endemic to a small rocky reef, morphology or coloration. L. zebroides has uni Pombo Rocks, approximately 15 km south of the cuspid teeth whereas the teeth of Ps. demasoni are Ruhuhu River delta. The reef may be the exposed bicuspid or tricuspid. Ps. livingstonii and Ps. part of a much larger rocky offshore area most of elegans do not exhibit the dark blue coloration which is now covered by sand and sediment. The seen in Ps. demasoni. The m outh of Ps. microstoma rocky reef was circumnavigated during SCUBA is placed in a ventro-terminal position whereas diving and appeared not to extend beyond the that of Ps. demasoni is terminal. Ps. lombardoi fe shallows (maximum depth approximately 7 me males exhibit a much lighter blue colour and lack tres). the blue-black colour seen in the lower fins of Ps. demasoni. Description D epth of body 2.9 to 3.4, head length 3.1 to 3.4, times in standard length. Snout 2.7 to 3.0, eye diameter 3.0 to 3.1, interorbital w idth 3.4 to 4.2, lower jaw 2.9 to 3.3, pre- m axillary pedicel 3.4 to 4.4, and depth of preorbital 3.5 to 6.0 times in head length. Depth of preorbital bone 1.3 to 2.2 times in snout length. Mouth positioned terminal ly with upper jaw slightly protruding. Teeth closely set in 4 to 6 rows in upper and 5 to 6 rows in lower jaw. The outer row contains bicuspid teeth whereas those of the in ner rows are tricuspid. Lower pharyngeal bone w ith fine bi cuspid teeth. 11 to 12 gill-rakers on the lower part of the anterior arch. Bottom two to three rakers reduced, merely knob-shaped; other rakers slender and simple. Five to six rows of scales on the cheeks; 31 to 32 scales in a longitudinal series. Dorsal XVII 8-9. Anal III 7 8. Pectoral 4.2 to 4.9 times in s ta n d a rd length, 1.3 to 1.6 times in head length. C audal peduncle 6.5 to 7.6 times in standard length, The holotype of Ps. demasoni (live coloration). Photo by Martin Geerts. 26 The Cichlids Yearbook, volume 4 (1994): 24-27 © CICHLID PRESS Ecology female with a standard length of 42.5 mm had ripe eggs in her ovary suggests that Ps. demasoni Ps. demasoni inhabits the upper three to four matures at a very small size. Immatures with an metres of the rocky habitat. It was seen regular estimated length of 15 to 20 mm were seen which ly but almost all sightings involved solitary indi exhibited a coloration pattern indistinguishable viduals. It seems that this species is evenly from that of adults, according with the normal spread throughout the habitat, each individual Mbuna pattern of identical coloration in females having a feeding area about two metres in diam and juveniles. eter. Such feeding areas normally include a large rock or the upper face of a boulder. Ps. demasoni Acknowledgements is generally ignored by other species, but chased from some areas occupied by breeding males of 1 would like to thank Laif DeMason, Fredrick more boisterous species. The occupation of such Wolff, and Erling Johanson of the Lake Nyasa relatively large feeding areas may imply that African Fishes company (LANYAFI), and Martin suitable food is not abundant and one might ex Geerts for their support during my stay in Tan pect fierce competition to exist among con- zania. specifics, resulting in aggressive behaviour tow ards their own kind. In the event two or three References individuals were found close together, no hint of intraspecific aggression was noted. In fact Ps. AHL, E. (1927) Einige neue Fische der Familie Cichlidae aus demasoni behaved remarkably peacefully to dem Nyasa-See. Sitzungsber. Ges. naturf. Fr. Berlin, No. 1 wards all species including its own. 10, pp 51-62. BAREL, C.D.N., M.J.P. van OIJEN, F. WITTE & E.L.M. Ps. demasoni feeds on algae attached to rocks. It WITTE-MAAS (1977) An introduction to the taxonomy bites the algal strands from the substrate, and and morphology of the haplochromine cichlidae from feeding sites seem to be visually selected (as is Lake Victoria. A manual to Greenwood's revision papers. the case with most herbivorous Labidochromis). Neth. J. Zool., 27 (4); pp 333-389.

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