130 COPEIA, 1994, NO. 1

haviourand copulationin Dracodussumieri Dum. & REYES,A. Y. 1968. Food habits of Draco volans Lin- Bib. (Reptilia: Sauria).J. Bombay Nat. Hist. Soc. naeus. SillimanJ. 15:353-356. 64:112-115. ROSE,B. 1981. Factorsaffecting activityin Sceloporus -. 1967b. Activity rhythm and thermoregula- virgatus. Ecology 62:706-716. tion in the South Indian flying lizard, Draco dus- SCHMIDT,K. P. 1935. Notes on the breeding behav- sumieriDum. & Bib.J. Anim. Morphol. Physiol. 14: ior of lizards. Zool. Ser. Field Mus. Nat. Hist. 20: 131-139. 71-76. MXGDEFRAU,K. 1991. Haltung, Verhaltenbeobach- SMITH,M. A. 1935. The Fauna of British India, in- tungen und Zuchtversuche von Draco spilopterus cluding Ceylon and Burma. Reptilia and amphibia. (Wiegmann, 1834). Herpetofauna 13:29-34. Vol. II. Sauria. Taylor and Francis Ltd., London, MARTIN,P., AND P. BATESON. 1986. Measuring be- England. haviour: an introductory guide. CambridgeUniv. STAMPS, J. A. 1977. Social behavior and spacing pat- Press, Cambridge,England. terns in lizards, p. 265-334. In: Biology of the Rep- MORI, A., AND T. HIKIDA. 1993. Natural history ob- tilia. Vol. 7. Ecology and behavior. A. C. Gans and servationson the flying lizards,Draco volans suma- D. W. Tinkle (eds.). Academic Press, London, En- tranus (Agamidae, Squamata)from Sarawak,Ma- gland. laysia. RafflesBull. Zool. In Press. MUSTERS, C. J. M. 1983. of the Draco L. (Agamidae, Lacertilia, Reptilia). Zool. DEPARTMENT OF ZOOLOGY, FACULTY OF SCIENCE, Verhandelingen No. 199:1-120. KYOTO UNIVERSITY, SAKYO, KYOTO, 606-01 P. 1962. Parades et terri- PFEFFER, comportement JAPAN.Submitted 5 Sept. 1992. Accepted 29 torial chez trois especes de Dragons-volants(Agam- Jan. 1993. Section editor: W. J. Matthews. idae) d'Indonesie. Terre Vie 109:417-427.

Copeia, 1994(1), pp. 130-135

Why Swim Upside Down?: A Comparative Study of Two Mochokid

LAUREN J. CHAPMAN, LES KAUFMAN, AND COLIN A. CHAPMAN

Some catfishes in the genus and its allied genera (family Mochok- idae) swim upside down and exhibit reverse countershading. We demonstrate a potential respiratory function for this behavior through laboratory observations of upside down () and right side up () exposed to low PO2. Both species used aquatic surface respiration (ASR) at the air-water interface when PO, was <15 mm Hg. With decreasing PO,, S. nigriventris increased the percentage of ASR time spent upside down, did not emerse its body during ASR, and had very modest surface activity levels. Syn- odontis afrofischeri used a vertical posture for ASR that caused emersion of its snout and required constant swimming to maintain position; it used active for- ward motion during ASR at very low PO, and made repeated trips to the bottom. The vertical posture and increased swimming activity associated with ASR by S. afrofischeri is probably less efficient than the inverted ASR of S. nigriventris.

M ANY catfishes of the family terning may allow the fish to merge with their are benthic in habit, feeding on bottom- background of light when their ventral surface dwelling organisms or detritus with their ven- is directed upward. Apparently, swimming with tral mouths (Lowe-McConnell, 1975). A few the ventral surface uppermost is used in a feed- species, however, can be found swimming in- ing context, facilitating the exploitation of verted, a habit often associated with exploita- plankton and fine detritus from the surface wa- tion of the water surface. Although similar mor- ters (Bishai and Abu Gideiri, 1963; Holden and phologically to the other mochokids, some Reed, 1972; Lowe-McConnell, 1975). Howev- species that exhibit upside down habits, such as er, a respiratory function has also been ascribed Synodontis nigriventris and Hemisynodontis mem- to this unusual behavior (Holden and Reed, branaceus, are characterized by reverse coun- 1972; Roberts, 1975). tershading (Daget, 1948; Poll, 1971). This pat- Many fish species use aquatic respiration at

? 1994 by the American Society of Ichthyologists and Herpetologists CHAPMAN ET AL.-WHY SWIM UPSIDE DOWN? 131 the surface (Aquatic Surface Respiration, ASR; species, an experimental tank (90 x 30 x 37 Kramer and Mehegan, 1981) when inhabiting cm, maintained at 32 cm of depth) was divided hypoxic waters. ASR works because diffusion into two major compartments (36 x 30 x 37 from the atmosphere provides a thin, well-ox- cm) using a screen partition that limited visi- ygenated microlayer of surface water, even bility and eliminated fish movement between though deeper waters may be hypoxic (Gee et compartments but permitted some water ex- al., 1978; Kramer and McClure, 1982; Kramer, change. Two additional partitions divided the 1983). The upside down habit of certain mo- major compartments from the two ends of the chokid fishes could also provide surface access tank. These smaller end compartments con- for purposes of ASR, an activity that would oth- tained heaters and air stones. Each major com- erwise be difficult for a fish having a ventral partment contained a box filter and two pieces mouth. There is little quantitative data on the of cover that consisted of strips of plastic con- respiratory responses of the upside down cat- nected to a small plexiglass tube. The two spe- fishes to hypoxia or their use of ASR. cies were placed in separate compartments, Here we compare the behavioral responses maintained at 23-26 C, and fed Tetramin food to hypoxia of two mochokid (Synodontis flakes. nigriventris and Synodontis afrofischeri). Unlike Fish were exposed to various concentrations S. nigriventris, S. afrofischeridoes not habitually of oxygen between 0.15 and 8.3 mg/L at 23- swim upside down and, thus, may not respond 26 C (3-154 mm Hg). Twenty-one trials were to hypoxia by swimming ventrally at the surface. conducted over 16 days, with the level of oxy- The percentage of time spent at the surface and gen concentration selected randomly from pre- the behavior of both species is described in re- determined values. No more than two trials were lation to PO2. In addition, we examine behav- conducted each day, with an average of 3 h ioral parameters related to efficiency of respi- between trials on the same day. Fish were main- ratory use of the surface layer. tained at normoxia overnight, and PO2 was re- turned to normoxic levels between trials con- ducted on the same day. Fish were starved for METHODS several hours before a trial to ensure that trips to the surface were not associated with feeding Study species.-Wild-caught S. afrofischeri were at the surface. PO2 was reduced by bubbling N2 obtained from Old World Exotics of Florida through an air stone in each of the two end from a private collector who works on the compartments. To create extreme hypoxia (<1 northern shoreline of Lake Victoria between mg/L), small amounts of sodium sulfite were Entebbe andJinja. The four smallest individuals added to the water (Lewis, 1970; Kramer and were captive spawned from the wild-caught Mehegan, 1981; Gee and Gee, 1991). Oxygen group in the exhibit at the Frank- content was measured (?0.1 mg/L) with a YSI lin Park Zoo, Boston, Massachusetts. Synodontis (Model 57) 02 meter and converted to P02 us- nigriventris used in this work were purchased ing standard tables (Davis, 1975). For each trial, from Metro Pets, New Jersey. oxygen concentration was reduced over 40-90 Synodontisafrofischeri occurs in the Nile basin, min. Fish were then allowed to acclimate for 30 primarily in Lake Victoria and its affluent riv- min. ers; the Victoria Nile; and lakes Nabugabo, The average amount of time spent at the sur- Kyoga, and Ihema (Greenwood, 1966; Poll, face was determined for each species by an ob- 1971). It is benthic, retains a normal orienta- server who sat behind a blind 0.5 m from the tion, feeds on larvae and molluscs (Cor- tank. The blind was necessary to prevent dis- bet, 1961), and rarely attains a total length of turbance that would result in fish retreating to over 15 cm. Synodontis nigriventris reaches a cover. A continuous record was kept of the maximum total length of 9.6 cm and occurs in number of fish and their orientation at the sur- streams and rivers of the central Congo (Poll, face for 30 min. Video recordings were used 1971). It has reversed countershading related for assessment of posture, positioning of the to its habit of routinely swimming inverted. barbels, and emersion of the snout. Gill ventilation rates/15 sec were determined The effectofPO2.-Four small S. afrofischeri(mean in relation to the method of ASR employed by Total Length = 64.9 + 4.7 mm) and four S. the fish. Oxygen was lowered slowly. Gill ven- nigriventris (mean Total Length = 64.3 ? 4.1 tilation rates were recorded four times on each mm) were selected from a stock aquarium (59 fish just prior to the ASR threshold level and x 37 x 39 cm, 23-26 C). To determine the after ASR was initiated for each species in dif- effect of hypoxia on the behavior of the two ferent postures. 132 COPEIA, 1994, NO. 1

100 individuals at the surface) was significantly high- er for S. nigriventris (mean = 116 sec) than for S. = 22 sec, t-test, t = 80- Synodontisnigriventris afrofischeri(mean paired 3.80, P = 0.005). 60 Respiratory behavior.--Synodontis afrofischeriwas 40 * never observed to swim on its back. ASR was achieved by positioning the body nearly per- < 20 pendicular to the surface (Fig. 2A). Active movements were required to maintain this pos- I 0 ture. ASR was performed in two ways. The first 100 was to perform ASR while hovering in a vertical position against the wall of the aquarium. We 80 refer to this as "pump ASR," because water .- Synodontis afrofischedr passing over the gills is pumped by mouth and S60 opercular movement. Pump ASR was more common at the initiation of ASR and at higher 40 oxygen levels. The second way was to perform ASR in a vertical posture while swimming back 20 and forth across the tank (Fig. 2A). Although the fish actively ventilated their gills while mov- 0 -m- m 33 3 3* across the tank buccal and 0 20 40 60 80 100 120 140 160 ing through oper- cular movement, this method presumably forc- OXYGENTENSION (mm Hg) es more well-oxygenated surface water over their than could be achieved active Fig. 1. Relationship between the percentage of gills by respira- time engaged in aquatic surface respirationand sub- tory movements in a static position. By con- surface PO2 (mm Hg) for Synodontisnigriventris and stantly moving along the water surface, the fish Synodontisafrofischeri. continuously exposes the buccal area to a new region of the surface layer. Forward motion RESULTS may also contribute to lift. Active movement across the tank during ASR was greater when Relationship betweenPO, and low PO2, PO2 was low (<6 mm Hg). We postulate that ASR.--At both S. nigriventris and S. afrofischeriused ASR. 02 uptake enhancement via forward motion is There was no evidence for regular inspiration obligate at very low PO2s in this species and of atmospheric air. On very rare occasions, S. tentatively refer to this as "ram-assisted ASR" afrofischeriwas observed to take a bubble into (Fig. 2A). Although ram-assisted ASR was used its mouth. Although this behavior may have more when oxygen was very low, mean gill ven- been used to adjust buoyancy (Gee and Gee, tilation rates showed no significant increase over 1991), it was not a regular event associated with pump ASR rates (no./15 sec: ram-assisted ASR. Nor were bubbles regularly released when ASR-43.1, pump ASR-41.6, t = 1.3, P = fish left the surface after ASR. 0.19), suggesting that ram-assisted ASR may fa- PO2 had a very strong effect on the amount cilitate more efficient use of the surface layer. of time both species spent using ASR. ASR was The use of either method resulted in a decrease initiated in both species at approximately 15 in gill ventilation rates from prethreshold levels mm Hg, and the occurrence of this activity in- (no./15 sec: pump ASR-41.6, prethreshold- creased rapidly with decreasing PO2 until ASR 59.9, t = 10.9, P < 0.001; ram-assisted ASR- occupied most of their time (Fig. 1). Synodontis 43.1, prethreshold-59.9, t = 9.8, P < 0.001). nigriventris spent an average of 98% of their Only the single pair of maxillary barbels were time engaged in ASR at 3-10 mm Hg. For S. in contact with the surface when S. afrofischeri afrofischeri, the percent of time at the surface performed either method of ASR. The two pairs averaged only 83% at 3-10 mm Hg (Fig. 1). of mandibular barbels were generally held to- During ASR, S. afrofischeri made frequent gether approximately 2-3 mm under the sur- short trips to the bottom. This was reflected in face of the water forming a scoop that may have frequent changes in the number of individuals aided in directing water into the mouth (Fig. at the surface. For S. nigriventris, ASR was less 2A). The snout was often emersed during ASR, frequently interrupted by trips to the bottom, increasing the weight of the fish. This may ac- and group composition remained stable over a count to some degree for the activity necessary longer period. Over the nine trials where both for maintenance of position during ASR. For species used ASR, mean bout length (time at S. afro-fischeri,movement toward the surface was the surface without a change in the number of often a slow upward creep in close proximity to CHAPMAN ET AL.-WHY SWIM UPSIDE DOWN? 133

100

z so

w1 60 i 50 A 40 30 * 20 10

0 20 40 60 80 100 % TIMEAT SURFACE Fig. 3. The relationshipbetween the percent time Synodontisnigriventris spends inverted during ASR and the percent time at the surface (ASR).

decreasing PO, (r = -0.93, P < 0.001), pro- ducing a strong correlation between the time B spent upside down during ASR and the time spent at the surface (r = 0.94, P < 0.001, Fig. 3). At the lowest oxygen level (<3 mm Hg), S. Fig. 2. Postures used by Synodontisafrofischeri (A) nigriventris 100% of its time at the surface and Synodontisnigriventris (B) during ASR. spent swimming upside down, supporting the hypoth- esis that inverted swimming is used to increase a side of the compartment. External stimuli (e.g., the efficiency of oxygen extraction from the a hand moving across the tank) generally pro- surface waters. Although the inverted posture duced a quick diving response. When PO, was was used more when the PO, was very low, gill very low, the fish returned to the surface within ventilation rates remained the same as those in seconds. the vertical posture (no./15 sec: vertical pos- Synodontis nigriventris exhibited two patterns ture-42.7, inverted posture-43.1, t = 0.3, P of ASR. It was common to find S. nigriventris = 0.79), again suggesting that the inverted pos- swimming inverted at the surface using ASR, ture facilitates more efficient use of the surface with all sets of barbels in contact with the sur- layer. In S. nigriventris, both postures were char- face (Fig. 2B). Often, the fish remained mo- acterized by only modest activity and could be tionless, floating inverted for several seconds, classified as "pump" ASR. As with S. afrofisch- with no active movement necessary for contin- eri, movement toward the surface was often slow ued use of the surface layer. This was periodi- and secretive. cally followed by the fish swimming slowly up- We used a simple procedure to assess relative side down to a new location, where, again, the differences in buoyancy between the two Syn- fish might stay for several seconds in the same odontis species. Four S. afrofischeri and four S. position. Pelvic fins were used in maneuvering nigriventris that were resting at the bottom of and maintenance of position. The second pos- the stock aquarium maintained under normoxic ture was similar to S. in afrofischeri that S. ni- conditions were removed from the tank, quickly griventris would also hang in a vertical position anesthetized with MS-222 (tricaine methane- against an upright structure (glass or divider) sulfonate), and gently placed back in the surface using ASR, with only the maxillary barbels at waters of the aquarium. All four S. afrofischeri the surface. However, unlike S. afrofischeri, S. were negatively buoyant and quickly sank. Three often in nigriventris remained the vertical posi- S. nigriventriswere only slightly negatively buoy- tion without active movement. The use of ei- ant, sinking very slowly, whereas one fish was ther posture resulted in a decrease in mean gill positively buoyant. Within the limits of this pro- ventilation rates from prethreshold levels (no./ cedure, this suggests that S. afrofischeriis more 15 sec: vertical posture-42.7, prethreshold- negatively buoyant than S. nigriventris. t = P < 62.9, 12.4, 0.001; inverted posture- Frequent trips to the bottom during ASR = < 43.1, prethreshold-62.9, t 11.0, P 0.001). bouts by S. afrofischeri, even at low PO2, and At PO2s below the threshold for ASR, the qualitative observations of this species' behavior percentage of time that S. nigriventris swam up- during ASR suggest that respiration in the sur- side down during ASR increased rapidly with face waters is energetically expensive. Synodontis 134 COPEIA, 1994, NO. 1 afrofischericlearly works at maintaining its ver- ceus and Brachysynodontisbatensoda in dry season tical position at the surface, which may reflect pools also suggest that inverted surface swim- both negative buoyancy and difficulties associ- ming may be used in a respiratory context (Rob- ated with maintenance of the posture. As an erts, 1975; Holden and Reed, 1972). Green index of energetic cost, we recorded the num- (1977) notes that, for H. membranaceus,the habit ber of strong beats of the caudal peduncle in of swimming upside down in the open water 30-sec intervals for each of the species during while feeding on plankton close to the surface ASR. Although S. nigriventris used delicate also tends to keep the fish in well-aerated water. movements of the caudal fin and pectoral fins There are a variety of behavioral and mor- at times when at the surface, distinct, strong phological features of various fishes that are beats of its caudal peduncle were far fewer than viewed as adaptations to permit or increase the in S. afrofischeri(S. nigriventris: mean = 6.0, n = efficiency of ASR. Lewis (1970) demonstrated 26; S. afrofischeri:mean = 44.2, n = 20, Mann- how the dorsally oriented mouth and dorso- Whitney test, z = -5.5, P < 0.001). ventrally flattened head of fishes such as Fun- dulus, Poecilia, and Gambusiaare adaptations for ASR. The dermal protuberances of the lower DISCUSSION lip that develop in certain Amazonian characids are viewed as adaptations to facilitate ASR by Because most fishes rarely turn upside down, reducing mixing between the oxygenated sur- the question of why some mochokids are com- face film and the hypoxic water beneath (Braum monly found swimming inverted has been of and Junk, 1982; Winemiller, 1989). Gee and interest for some time. That reversed counter- Gee (1991) found that nine species of benthic shading is often associated with the inverted negatively buoyant gobies held a bubble in the behavior suggests that there has been selection buccal chamber during ASR, which appeared for traits minimizing for fish assum- to function in providing lift to the head or body, ing the upside down posture. There are labo- facilitating ASR and potentially adding oxygen ratory and field observations, and stomach con- to buccal water prior to gill ventilation. tent data, demonstrating that inverted For Synodontisnigriventris, Hemisynodontis mem- swimming is an adaptation for feeding on sur- branaceus, Brachysynodontisbatensoda, and other face plankton (Bishai and Abu Gideiri, 1963; mochokid catfish that are habitually inverted, Poll, 1971; Lowe-McConnell, 1975). Hemisyn- a combination of behavioral and morphological odontismembranaceus has been observed feeding features seem to be related to their utilization on micro-organisms from the surface waters with of ASR. The inverted behavior places the sub- its ventral surface uppermost (Poll, 1971; Lowe- terminal mouth in a position to efficiently pump McConnell, 1975). In Hemisynodontismembrana- surface water over the gills. The placement of ceus and Brachysynodontisbatensoda, both invert- all three pairs of barbels in contact with the ed swimmers, the gill rakers are longer and more surface, which was observed in S. nigriventris, densely placed than those of other benthic feed- may function in an analogous manner to the ing mochokids, producing an efficient sieving characid dermal protuberances. Reversed organ for the exploitation of plankton (Bishai countershading potentially minimizes the threat and Abu Gideiri, 1963). Both of these species of predation during time at the surface. are surface feeders, but they will readily feed The comparative study of S. afrofischeri,a spe- on bottom food when surface food is not avail- cies that retains a normal orientation, and the able (Bishai and Abu Gideiri, 1963). upside down catfish, S. nigriventris,provides fur- Although it is clear that swimming upside ther support for the respiratory function of in- down has advantages for feeding, this does not verted swimming. In S. afrofischeri,emersion of preclude a respiratory function, nor is it nec- the snout during ASR, constant swimming to essarily the case that feeding at the surface pre- maintain position at the surface, the use of ram- disposed these species to use inverted swimming assisted ASR at very low PO2, and repeated trips for efficient ASR. Our study provides several to the bottom during ASR suggest that the ver- lines of evidence consistent with the idea that, tical posture and associated ASR performance for S. nigriventris, inverted swimming increases by S. afrofischeriis less efficient than the inverted the efficiency of ASR for a fish with a subter- strategy of S. nigriventris. At low PO2, ram-as- minal mouth. These include the use of inverted sisted ASR may be necessary to maintain lift swimming for ASR at low PO2, no emersion of and to extract sufficient oxygen from the sur- the snout, an increase in the percentage of sur- face layer because the position of the mouth is face time spent upside down with a decrease in not flat against the surface layer. Positioning of PO2, and only modest activity when using ASR. the mandibular barbels in a scooplike formation Field observations of Hemisynodontismembrana- under the water surface could facilitate more CHAPMAN ET AL.-WHY SWIM UPSIDE DOWN? 135

directed flow of the upper water layer toward for surviving in oxygen deficient waters. Int. Rev. the mouth. The vertical posture, in combina- Ges. Hydrobiol. 67:869-886. tion with the subterminal position of the mouth CORBET, P. S. 1961. The food of non- fishes in the Lake Victoria with remarks on in S. afrofischeri,often results in emersion of the basin, their snout ASR. This both increases the evolution and adaptation to lacustrine conditions. during Proc. Zool. Soc. London 136:1-101. of fish and increases the stim- weight potentially DAGET, 1948. Les a uli for aerial J. Synodontis (Siluridae) polarite predators. pigmentaire inversee. Bull. Mus. Natl. 20:239-243. Whether inverted at the surface feeding pre- DAVIS,J. C. 1975. Minimal dissolved oxygen require- disposes upside down mochokid catfish to more ments of aquatic life with emphasis on Canadian efficient utilization of the well-oxygenated sur- species: a review. J. Fish. Res. Board Canada 32: face waters, or whether the original adaptation 2295-2332. was to low oxygen, is not clear. However, our GEE,J. H., ANDP. A. GEE. 1991. Reactions of gobioid fishes to results do suggest that inverted swimming may hypoxia: buoyancy control and aquatic sur- face 1991:17-28. increase the efficiency of ASR for fishes with a respiration. Copeia , R. F. TALLMAN, AND H. SMART. 1978. Re- subterminal mouth, permitting exploitation of J. actions of some great plains fishes to waters or survival in such progressive hypoxic prolonging hypoxia. Can. J. Zool. 56:1962-1966. habitats. We believe that the contro- apparent GREEN,J. 1977. Haematology and habits in catfish versy over the primary function of inverted of the genus Synodontis.J. Zool. London 182:39- swimming, i.e., feeding versus respiration, is 50. moot. To the inverted catfishes, the water's sur- GREENWOOD,P. H. 1966. The fishes of Uganda. face is just another substratum. The cluster of Uganda Society, Kampala. morphological and behavioral traits exhibited HOLDEN, M., AND W. REED. 1972. West African freshwater fish. by upside down catfishes reflects an extension Longman, London, England. of mochokid and more siluroid KRAMER,D. L. 1983. Aquatic surface respiration in simple generally the fishes of Panama: distribution in relation to risk adaptations to life at structural interfaces. Sur- of hypoxia. Env. Biol. Fish. 8:49-54. face and surface hand in feeding respiration go , ANDM. MCCLURE.1982. Aquatic surface res- hand, as and from just feeding refuge predators piration, a widespread adaptation to hypoxia in do in benthic environments. Nonetheless, it is tropical freshwater fishes. Ibid. 7:47-55. odd that so few benthic fishes exploit surface , ANDJ. P. MEHEGAN.1981. Aquatic surface waters and that they may exist only in Africa, respiration, an adaptive response to hypoxia in the despite the high diversity of catfishes of similar guppy, Poecilia reticulata (Pisces, Poeciliidae). Ibid. morphology in South America. The answer to 6:299-313. LEWIS,W. M., 1970. the first question may lie in the high risk of JR. Morphological adaptations aerial The restriction of of cyprinodontoids for inhabiting oxygen deficient predation. apparent waters. 1970:319-326. down catfishes to Africa is more Copeia upside puz- LOWE-MCCONNELL,R. H. 1975. Fish communities zling. in tropical freshwaters. Longman, London, En- gland. ACKNOWLEDGMENTS POLL, M. 1971. Revision des Synodontis Africains (Famille Mochocidae). Annales. Mus. R. Afr. Cent. Funding for this research was provided by the 191:1-497. New England Aquarium, NSERC (Canada), Pew ROBERTS,T. R. 1975. Geographical distribution of African freshwater fishes. Zool. Linn. Soc. Foundation, and an NSF grant to L. Kaufman J. 57: and K. Liem. We would like to thank D. Kramer 249-319. K. 0. 1989. of and M. for comments on this WINEMILLER, Development dermal Pagel helpful proj- for surface in ect. R. McAndrews care. lip protuberances aquatic respiration provided expert South American characid fishes. Copeia 1989:382- We thank the Franklin Park Zoo (Boston, Mas- 390. sachusetts) and Old World Exotics for speci- mens of S. afrofischeri from the Lake Victoria (LJC) MUSEUM OF COMPARATIVE ZOOLOGY, Fishes Captive Breeding Program. HARVARD UNIVERSITY, CAMBRIDGE, MASSA- CHUSETTS 02138; (LK) EDGERTON RESEARCH LAB, NEW ENGLAND AQUARIUM, CENTRAL LITERATURE CITED WHARF, BOSTON, MASSACHUSETTS 02110- AND PEABODY BISHAI,H. M., ANDY. B. ABU GIDEIRI.1963. Studies 3309; (CAC) MUSEUM, HAR- VARD on the biology of Genus Synodontisat Khartoum. II. UNIVERSITY, CAMBRIDGE, MASSA- Food and feeding habits. Hydrobio. 26:98-113. CHUSETTS 02138. Submitted 25 March 1992. BRAUM,E., AND W. J. JUNK. 1982. Morphological Accepted 9 Jan. 1993. Section editor: G. R. adaptation of two Amazonian characoids (Pisces) Ultsch.