Vision Research 40 (2000) 879–890Visual pigments of African cichlid fishes: evidence for ultravioletvision from microspectrophotometry and DNA sequencesKaren L. Carletona,*, Ferenc I. Ha´rosib,1, Thomas D. Kochera,caDepartment of Zoology, Uni6ersity of New Hampshire, Rudman Hall,46College Road, Durham, NH03824-2617, USAbLaboratory of Sensory Physiology, Marine Biological Laboratory, Woods Hole, MA02543, USAcProgram in Genetics, Uni6ersity of New Hampshire, Durham, NH03824, USAReceived 4 June 1999; received in revised form 12 October 1999AbstractWe have found evidence for ultraviolet visual capabilities in a Lake Malawi cichlid fish, Metriaclima zebra. Microspectropho-tometry of single cones revealed a visual pigment with peak sensitivity at 36894 nm. M. zebra also expresses a putative ultravioletopsin gene whose sequence is closely related to the SWS-1 opsin for other fishes. Several other African cichlids have a functionalcopy of this UV gene in their genomic DNA, but do not appear to express this gene as adults. These results suggest thatultraviolet vision is important for some cichlid fishes. UV wavelengths should therefore be included in future studies of cichlidvision, behavior and color patterns. © 2000 Elsevier Science Ltd. All rights reserved.Keywords:Opsin; Visual pigment; Ultraviolet vision; Cichlidae; Microspectrophotometrywww.elsevier.com/locate/visres1. IntroductionThe cichlid fishes of the East African Rift lakes areone of the best known examples of rapid vertebrateradiations. In Lake Malawi, an estimated 500–1000species have arisen in the last 1.5 million years (Fryer &Iles, 1972; Lewis, Reinthal & Trendall, 1986). Malesdisplay bright breeding coloration and this color pat-tern is a key distinction between closely related species,as has been demonstrated from taxonomic (Ribbink,Marsh, Marsh, Ribbink & Sharp, 1983), behavioral(McElroy & Kornfield, 1990), and genetic work (Al-bertson, Markert, Danley & Kocher, 1999). Speciationof these fishes may be driven by sexual selection forthese male traits based on female preferences(Dominey, 1984).Several lines of evidence suggest that vision is impor-tant in cichlid mate choice. Behavioral experimentsshow that females correctly choose conspecifics whenvisual cues are available (Kellogg, 1997; Seehausen &van Alphen, 1998), but choose non-assortatively whencolor differences are masked (Seehausen, van Alphen &Witte, 1997; Seehausen & van Alphen, 1998). Malecolor pattern is therefore an important character usedby females to recognize and choose mates. Recenttheories on sexual selection suggest that male colorpatterns may evolve to better stimulate female visualsystems (Ryan, 1990; Kirkpatrick & Ryan, 1991;Endler, 1992). To understand this evolution, it is neces-sary to determine the spectral sensitivities of the cichlidvisual system.Several studies have examined the visual systems of afew African cichlid species including Haplochromis bur-toni from Lake Tanganyika (Fernald & Liebman, 1980;Fernald, 1981, 1984) and several haplochromines fromLake Victoria (van der Meer & Bowmaker, 1995).These species have well defined retinal mosaics com-posed of double cones and one type of single cone. Theabsorption maxima for the cones from all of thesespecies are similar. Single cones have a short wave-length sensitive pigment (455– 465 nm) and doublecones contain medium (520–540 nm) and long (560–600 nm) wavelength sensitive pigments.The survey of fish visual pigments by Levine andMacNichol (1979) include two species from Lake* Corresponding author.1Present address: Division of Natural Sciences, New College of theUniversity of South Florida, 5700 N. Tamiami Trail, Sarasota, FL34243-2197, USA.0042-6989/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.PII: S0042-6989(99)00238-2K.L. Carleton et al./Vision Research40 (2000) 879 – 890880Malawi: the rock dwelling Pseudotropheus zebra (nowMetriaclima zebra (Stauffer, Bowers, Kellogg &McKaye, 1997)) and the sand dwelling predatorHaplochromis compressiceps (now Dimidiochromiscompressiceps (Eccles & Trewavas, 1989)). Absorbancedata were taken only for double cones, but there weremarked differences between the two species. The peakabsorbances of D. compressiceps pigments were 536 and569 nm, while those of M. zebra were 488 and 533 nm.The considerable blue shift of the cones of M. zebrarelative to D. compressiceps suggested that M. zebramight have ultraviolet sensitive single cones.A variety of fish species have ultraviolet sensitivecones (Ha´rosi & Hashimoto, 1983; Bowmaker, 1990,1995; Hawryshyn & Ha´rosi, 1991, 1994) which areintegrated into their color opponent system (Ha´rosi &Fukurotani, 1986; Hashimoto, Ha´rosi, Ueki & Fukuro-tani, 1988; Douglas & Hawryshyn, 1990; Jacobs, 1992;Tovee, 1995). The UV sensitive fishes studied to datetypically have four visual pigments, one of which is UVsensitive and found in an additional corner cone in theretinal mosaic (Bowmaker, 1995). UV sensitivity maybe lost (Bowmaker & Kunz, 1987) or even regained(Beaudet, Novales Flamarique & Hawryshyn, 1997)with age.Visual pigments are composed of an opsin proteinbound to a chromophore, where the chromophore ismost commonly either 11-cis retinal (A1) or 3-dehy-droretinal (A2) (Bowmaker, 1995). There are five pri-mary classes of vertebrate opsins: the rod opsin, RH1,and four cone opsins: SWS-1 (ultraviolet sensitive),SWS-2 (short wave sensitive), RH2 (mid wavelengthsensitive and similar to rod opsin), and LWS/MWS(mid to long wavelength sensitive) (Okano, Kojima,Fukada, Shichida & Yoshizawa, 1992; Hisatomi,Kayada, Aoki, Iwasa & Tokunaga, 1994; Chang, Cran-dall, Carulli & Hartl, 1995; Yokoyama 1994, 1995,1997). Each of these classes has distinctly differentamino acid sequences with certain key sites controllingthe peak absorption (Chang et al., 1995; Yokoyama &Radlwimmer, 1998). Because each of the five opsinclasses diverged prior to the evolution of jawed fish, theclass to which a particular opsin belongs can beuniquely determined from short (200 bp) segments ofDNA sequence obtained with the use of degenerateprimers (Hisatomi et al., 1994).Sequences for complete cone opsins are available foronly a handful of fish species including a blind cavefish,Astynax fasciatus (Yokoyama & Yokoyama, 1990a,b,1993; Register, Yokoyama & Yokoyama, 1994), agoldfish Carassius auratus (Johnson, Grant, Zankel,Boehm, Merbs, Nathans et al., 1993; Hisatomi, Satoh,Barthel, Stenkamp, Raymond & Tokunaga,