MYANMAR CATFISH 



21 



Distribution 



Rita sacerdotum appears to be distributed widely through the 

 Ayeyarwaddy River basin of My anmar. Specimens examined during 

 this study were all from the lower portions of the basin, but I 

 observed a few large individuals in markets as far upriver as Manda- 

 lay. In addition, Rita is seen occasionally in the Myitkyina market (U 

 Tun Shwe, pers. comm.). Outside of the Ayeyarwaddy basin and its 

 extensive delta, there is one record of specimens from the Sittoung 

 River (BMNH 1891.1 1.30.242-243), and two from the Bago River 

 (BMNH 1998.3.11.1 and CAS 99210). 



Natural History 



Little is known about Rita sacerdotum. While small specimens, up to 

 about 25 cm, are routinely found in markets of Yangon and smaller 

 delta villages, at least during the rainy season (April to September; 

 U Myint Pe, pers. comm.), large specimens are only rarely seen in 

 markets. All of the specimens examined during this study appear to 

 be juveniles and there is no published indication of the size of 

 maturity for this species. 



Individuals as small as 22 mm were obtained from the tidal rivers 

 in the vicinity of Yangon in November, 1997. The presence of these 

 tiny individuals in the lower course of the river suggests that Rita 

 may reproduce in the estuarine part of the river and disperse more 

 widely throughout the river at a larger size. This idea is supported by 

 anecdotal reports that large numbers of large Rita appear at an island 

 pagoda, in the middle reaches of the Ayeyarwaddy River, for a short 

 period of time during monsoon season (U Nyi Nyi Lwin, pers. 

 comm.). This may be indicative of a spawning migration. 



Examination of the gut contents of a few specimens revealed that 

 Rita sacerdotum feeds on a variety of aquatic and terrestrial inverte- 

 brates. Several specimens contained fragments of small glass prawns, 

 and others contained pieces of winged insects. A comprehensive 

 study of the food habits is not possible at this time due to the 

 relatively small number of specimens available and the fact that the 

 specimens in collections represent only juveniles. 



KEY TO SPECIES OF RITA 



1 . Dorsal surface of head, between eyes and occipital spine, covered with 

 thick layer of muscle; pelvic fin black 



Rita gogra (rivers of the Deccan region of peninsular India) 



Dorsal surface of head covered only with skin; pelvic fin pale 2 



2. Eye small, 10-13% HL 3 



Eye large, 30-40% HL 4 



3. Dorsal-fin spine as long, or longer than length of head, adpressed spine 

 extends to or beyond adipose-fin origin (in specimens greater than 100 

 mm); palatal teeth in two elliptical patches, not meeting at midline; 

 teeth on posterior extent of lower jaw and palate molariform, much 

 larger than anterior teeth 



Rita rita (Ganges River basin) 



Dorsal-fin spine no longer than head minus snout, adpressed spine not 

 reaching adipose-fin origin; palatal teeth in a single crescent patch that 

 extends across midline of palate; teeth on palate more or less uniform in 



size (Figure 1A) 



Rita sacerdotum (Myanmar: Ayeyarwaddy and Sittoung River basins) 



4. Palatal teeth in slender patches along lateral margin of palate, no larger 

 than teeth in upper jaw and not meeting at midline (Figure IB), dorsal- 

 fin spine smooth anteriorly, except for few serrae basally 



Rita kuturnee (rivers of Deccan region of peninsular India) 



Palatal teeth in large quadrangular patch that covers most of palate; teeth 

 large and molariform in middle of patch, smaller laterally; dorsal-fin 

 spine with single row of antrorse serrae, for at least basal 2/3 of spine 



length 



Rita chrysea (Mahanadi River and nearby tributaries in Orissa) 



ACKNOWLEGEMENTS. Examination of specimens forthis study was facili- 

 tated by David Catania and William Eschmeyer (CAS), Darrell Siebert and 

 Oliver Crimmon (BMNH), and Richard Vari (USNM). Tyson Roberts pro- 

 vided valuable insights during early stages of this study. The photograph of 

 the holotype of Rita sacerdotum was arranged by Darrell Siebert and taken by 

 Phil Hurst (BMNH). Al Leviton provided the photographic reproduction of 

 the published illustration of Rita sacerdotum, from his personal copy of 

 Anderson (1878 [1879]). Molly Brown drew figure 1 and Alison Schroeer 

 drew figure 5. Travel to Myanmar was undertaken as part of a series of 

 consultancies for the United Nations Food and Agriculture Organization. 

 Kent Carpenter and Dora Blessich of that organization were instrumental in 

 making these trips possible. Collection of specimens in Myanmar was made 

 possible by the Myanmar Department of Fisheries; several individuals, 

 including U Hla Win. U Nyi Nyi Lwin, U Myint Pe and U Mya Than Tun, 

 provided me with assistance and valuable information. Financial support to 

 travel to London and to examine specimens at The Natural History Museum 

 was provided by TWA and the Inhouse Research Fund of the California 

 Academy of Sciences. Without the help of all of these persons and organiza- 

 tions, this study could not have been undertaken The manuscript was 

 improved by comments from James Atz, Nigel Merrett, Darrell Siebert and 

 Richard Vari. 



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