dotti90 Posted July 21, 2010 Share Posted July 21, 2010 what is a white knight? i seen them at my lfs and they are pretty damn expensive and does anyone know of any online pics of them Link to comment Share on other sites More sharing options...
Adam_J Posted July 21, 2010 Share Posted July 21, 2010 what is a white knight? i seen them at my lfs and they are pretty damn expensive and does anyone know of any online pics of them bleach Link to comment Share on other sites More sharing options...
Adam_J Posted July 21, 2010 Share Posted July 21, 2010 http://www.google.com.au/images?q=white+kn...ved=0CDUQsAQwAw Link to comment Share on other sites More sharing options...
mathobes Posted July 21, 2010 Share Posted July 21, 2010 controversial. Only read a little bit of this thread but it should help you. http://www.qldaf.com/forum/viewtopic.php?f=12&t=30740 Link to comment Share on other sites More sharing options...
mcloughlin2 Posted July 21, 2010 Share Posted July 21, 2010 These guys are still a pretty hot debate. There is much uncertainty as to what they are. The main though behind them is they are either a morph of electric blue cichlid or a hybrid between an electric blue and some variant of peacock. Personally I now believe these guys to be an albino or melanistic variant of the electric blue cichlid. Reason I give tw possibilities as to what they are is the fish out there appear to either have red eyes (Charactoristic of albino) or black eyes (A characteristic of melanistic animals) Perhaps someone with more knowledge regarding these can chip in. If your after pictures do a search on google. Plenty there. Also do a search of this forum. This topic has come up before. Link to comment Share on other sites More sharing options...
dotti90 Posted July 21, 2010 Author Share Posted July 21, 2010 yea none of them have red eyes thats why i belive they arnt albino and they look far more beautiful then what google images shows them as ill get some pics for you guys Link to comment Share on other sites More sharing options...
intern1 Posted July 21, 2010 Share Posted July 21, 2010 I have seen them a few times on a occasion but am warry like most people are, the lack of red in the eyes therefore im not sure if they a true albino Link to comment Share on other sites More sharing options...
mcloughlin2 Posted July 21, 2010 Share Posted July 21, 2010 From the ones I have seen I believe they are electric blues. If the opportunity came around I wouldn't hesistate to breed them. They would make a great contrast in any african cichlid tank to break up the colour. Link to comment Share on other sites More sharing options...
Pilly Posted July 21, 2010 Share Posted July 21, 2010 Its funny you said they were expensive as bay fish recently ran a front page special on them and you could pick them up for a couple of bucks wholesale. Link to comment Share on other sites More sharing options...
brandt Posted July 21, 2010 Share Posted July 21, 2010 What are the chances of finding some in Newcastle? I think they look nice and would like some. Brandt Link to comment Share on other sites More sharing options...
Pilly Posted July 21, 2010 Share Posted July 21, 2010 What are the chances of finding some in Newcastle? I think they look nice and would like some. Brandt Ask one of the local shops to order you some in. They should be able to give you retail price before they order them so you knowwhat you are up for. Link to comment Share on other sites More sharing options...
superbad0417 Posted July 22, 2010 Share Posted July 22, 2010 how much do these normally go for in the pet shops ?? Link to comment Share on other sites More sharing options...
Pilly Posted July 22, 2010 Share Posted July 22, 2010 how much do these normally go for in the pet shops ?? $30 ish retail. I have an assurance from Bay Fish they are a melalin deficient Sciaenochromis fryeri not a hybrid. Link to comment Share on other sites More sharing options...
Foti Posted July 22, 2010 Share Posted July 22, 2010 does anyone have any ? im going to add a wtb add if not il order some ? Link to comment Share on other sites More sharing options...
firthy13 Posted July 22, 2010 Share Posted July 22, 2010 i believe that they are a true melanistic deficient electric blue. i have a colony of these a while back, there personality, movements and physical shape were absolutely identical to an electric blue. i read somewhere that konings does recognise them as Sciaenochromis species. he stated that he observed a melanistic deficient electric blue at a specific location(around maleri is., nankoma is., nakantenga is. i think ).he also noted that it did not have red eyes. ill try and find where i read that for you's.. my colony disappeared, sold them to a bloke and requested his contact details so i could get some fry back at some stage in the future. i went to ring him and the number he gave me had been disconnected.. so who knows. if you do find some, i would love a male but.. Link to comment Share on other sites More sharing options...
M.H Posted July 22, 2010 Share Posted July 22, 2010 I wouldnt mind a male for my display tank their not a bad looking fish Link to comment Share on other sites More sharing options...
ctaylor Posted July 22, 2010 Share Posted July 22, 2010 There's a guy near me that was breeding them, I'll try contact him and see if he's got any fry... Link to comment Share on other sites More sharing options...
mrsmack Posted July 24, 2010 Share Posted July 24, 2010 I just had my lfs order some for me, picked up a male and 2 females around 5/6cm for $23 each. They look great in contrast with the malawi I have (Mangano, Rusty's E.Y's, Peacocks) and there are no aggression problems in the tank. I really like them despite the controversy. Zoe Link to comment Share on other sites More sharing options...
Ant Posted August 14, 2010 Share Posted August 14, 2010 Sorry to bring up an old thread but none of us can be sure of any electric blue we have here in Aus, unless you have kept your Ahli and fryeri separate since there introduction to Aus, or unless you have had them imported in. I did once here of someone in WA who has the two species in separate tanks. But the likely hood is that most out there have been crossed at some point. It has been discussed before..i'll pull up the thread when I find it. Link to comment Share on other sites More sharing options...
Ant Posted August 14, 2010 Share Posted August 14, 2010 Here is the thread. Not long but a few people validate my thaughts. As Andy (Vis) states it hasn't been proven though. http://www.aceforums.com.au/index.php?show...=Sciaenochromis Link to comment Share on other sites More sharing options...
highlucks Posted August 23, 2010 Share Posted August 23, 2010 I dont get on these forums much but here is the little I know. Apparently as I was told by an LFS owner here in Perth these guys were line bread from the Scianochromis Fryeri "Maylandi" too achive the light powder blue colour that these guys have. Here are a couple of pics of the ones that I used to have BTW they are much cheaper here. Around $11-16 for 6-8cm fish. Male Male and Female Holding Female Link to comment Share on other sites More sharing options...
pennywise Posted August 31, 2010 Share Posted August 31, 2010 if any1 is interested in the white knights let me know as i have a heap of fry from 3-8cm i stoped breeding them as i cant keep up with the sales of males lol im getting 85%females and 15%males out of my breeders (3m22females ) i have tryed hight p.h low p.h hight temps. low temps all the same Link to comment Share on other sites More sharing options...
intern1 Posted August 31, 2010 Share Posted August 31, 2010 I found a review article the other day because i was interested in sex determination of fish Review article Sex determination and sex differentiation in fish: an overview of genetic, physiological, and environmental inf luences by Robert H. Devlin a,*, YocraPaka Nagahama This is what the article states in regards to temp and other factors In mammals and birds, embryonic development at the time of sex determination occurs under controlled temperature conditions. However, fish are poikilothermic, and embryonic development proceeds in full exposure to the external physical environment where rela- R.H. Devlin, Y. Nagahama / Aquaculture 208 (2002) 191–364 269 tively large temperature alterations can occur. While fish have evolved wide tolerances for such temperature effects to allow development of viable embryos, evidence is accumulating that effects on sex determination may occur. Temperature effects on sex have been now observed in at least eight families of jawed fishes, as well as one Agnathan species. Sex determination is controlled by the actions of a variety of biochemical pathways involving many different proteins (e.g. transcription factors, steroidogenic enzymes, receptors and second messenger systems, etc.). Since it is well known that temperature can dramatically influence the structure and function of proteins and other macromolecules, temperature fluctuations as are encountered by fish in different habitats could alter sex-determination pathways and influence the probability that development would be male or female. Temperature-dependent sex determination has been extensively studied in reptiles, where exposure to elevated temperature results in female development in some species (Bull and Vogt, 1979; Vogt and Bull, 1982). These temperature-dependent effects appear to be mediated in part by influencing aromatase activity and estradiol synthesis in females, and by steroid receptors in both sexes (Crews and Bergeron, 1994; Crews, 1996). Such effects may also occur in fish: Estradiol secretion has been shown to range as much as 20-fold over just a 5 jC temperature range in common carp (Manning and Kime, 1984), and temperature also affects steroid production testis in trout, carp and tilapia (Kime and Hyder, 1983; Manning and Kime, 1985; Kime and Manning, 1986). In Nile tilapia (O. niloticus) and Japanese flounder (P. olivaceus), elevated temperatures (which cause masculinization) are associated with reduced aromatase mRNA levels and lower estradiol levels (Kitano et al., 1999; D’Cotta et al., 2001), and treatment with an aromatase inhibitor is able to counter the masculinizing effects of high temperature (Kwon et al., 2000). In the Atlantic silverside M. menidia, incubation of larvae at higher temperatures increases the proportion that differentiate as males (Conover and Kynard, 1981). The temperature-sensitive period was during the mid-larval stage, and subsequent temperature fluxes had no effect on sex ratio, suggesting a switch-type mechanism operates to control sex in this species (Conover and Fleisher, 1986). The temperature responsiveness of M. menidia also has a genetic component since progeny from different females respond differently to temperature influences (Conover and Kynard, 1981), and different sires also can have a strong effect on temperature responsiveness (Conover and Heins, 1987a). In nature, ocean temperatures are suspected to affect sex ratio in Menidia species such that females are produced from earlier, colder spawning conditions, allowing additional time for ovarian growth (Conover, 1984; Middaugh and Hemmer, 1987). This temperature responsiveness is affected by latitude (Conover and Heins, 1987b), such that northern populations from Canada do not respond to temperature, whereas those from South Carolina do (Lagomarsino and Conover, 1993). These genetic differences allow distinct populations of M. menidia to adjust sex ratios appropriately at different latitudes to maximize fitness. Low temperature is also capable of biasing sex differentiation toward females in two other atherinids, O. bonariensis and Patagonina hatcheri. The two species show distinctive responses to temperature: O. bonariensis sex ratio is influenced without threshold over a broad range of temperatures, whereas P. hatcheri sex is only influenced at temperature extremes and otherwise has genetically determined sexes (Stru¨ssmann et al., 1996b,c). The temperature-sensitive period for O. bonariensis (Stru¨ssmann et al., 1997) was during the first few weeks posthatching, similar to that seen for Menidia. 270 R.H. Devlin, Y. Nagahama / Aquaculture 208 (2002) 191–364 In the loach M. anguillicaudatus, elevated temperature has been shown to skew sex ratios towards male (Nomura et al., 1998). Masculinization was also induced by elevated temperatures in genetically female (gynogenetic) diploids, although interestingly, some males also rarely appeared in certain control crosses as well, suggesting that other factors such as aneuploidy or autosomal sex factors may also influence sex differentiation in this species. In the synchronous hermaphrodite R. marmoratus, low temperature incubation (20 vs. 30 jC) increased the proportion of primary males from 3.8% to 74.5%, whereas other physical variables such as salinity and illumination had no consistent effect (Harrington, 1967; Harrington and Crossman, 1976). Recently, the lack of effect of salinity on sex differentiation was confirmed in O. niloticus (Abucay et al., 1999). In a comprehensive survey of temperature and pH effects on sex determination among 39 teleost species, 33 cichlid species in the genus Apistogramma (bred from field-collected specimens) and Poecilia melanogaster (from a laboratory stock) were found to be significantly affected by larval incubation temperature (Roemer and Beisenherz, 1996). In most but not all cases, increasing temperature (range 23–29 jC) elevated the percentage of males in broods. The effect of pH was less pronounced, but, in general, high pH conditions reduced the proportion of males, in some cases to less than 10% (in A. caetei). In contrast, pH has been found to have a significant effect on sex ratio within broods of Pelvicachromis pulcher, P. subocellatus, P. taeniatus, Apistogramma borelli, A. caucatoides, and X. helleri, where low and high pH produce male and female-biased broods, respectively (Rubin, 1985). Although sex determination in tilapia species is known to be controlled polygenically by major and minor factors on the sex chromosomes and autosomes (see Section 5.5), temperature influences on sex ratio have also been detected (Baroiller and D’Cotta, 2000). In Oreochromis mosambicus, genetically female groups (derived from crosses between sex-reversed XX males and regular females) exposed to low temperature (19 jC) incubation during early development resulted in 89% males (Mair et al., 1989). In a similar study, O. mosambicus exposed to a range of temperatures (20–32 jC) in early development displayed an increasing proportion of males with elevated temperature (Wang and Tsai, 2000). In O. aureus (which has primarily a ZW system), warm temperatures (32 jC) induced differentiation of 20% females compared to 3% observed in controls (Mair et al., 1989), whereas more males (98% vs. 63% in controls) have been observed at higher temperatures in other experiments (Desprez and Melard, 1998b). Fluctuating temperature regimes also can induce masculinization, but less effectively than a constant high (35 jC) temperature (Baras et al., 2000). In O. niloticus, elevated temperature generally has a masculinizing effect that is affected by, and can override, genetic influences on sex determination (Baroiller et al., 1995, 1996; Baras et al., 2001), but a feminizing effect has also been observed in all-male and YY strains of O. niloticus, particularly in inbred vs. outbred strains (Abucay et al., 1999). Environmental conditions are anticipated to have variable effects on sex differentiation depending on the genetic background and developmental stability of different strains. These observations imply that sex determination is very labile in different tilapia species and that, depending on the exact combinations of genetic modifiers present in different strains, environmental effects on sex determination may be variable in strength and direction, and may also be very sensitive to the level of inbreeding and consequent developmental stability within a strain (Purdom, 1993; Abucay et al., 1999). Temperature lability may provide evolutionary advantages to R.H. Devlin, Y. Nagahama / Aquaculture 208 (2002) 191–364 271 tilapia species by providing higher numbers of males with increased capacity for dispersal (Baras et al., 2000), but would also be expected to affect the establishment of sex chromosomes with complete control over the sex determination process and would also result in the accumulation of balancing autosomal genetic factors. Genetic effects on temperature responsiveness have also been detected in Poeciliopsis lucida, a viviparous species: Exposure of embryos from a sensitive strain to elevated rearing temperatures before parturition can bias the sex ratio towards males (Schultz, 1993). Analysis of F1 progeny derived from reciprocal crosses between responsive and nonresponsive strains also showed that this effect arises primarily from the genotype of the progeny rather than from maternal influences. Recently, elevated temperature has been shown to have a masculinizing effect on sex determination in the honmoroko, Gnathopogon caerulescens (Fujioka, 2001), a species with primarily an XX/XY system of sex determination. In this study, intersexes could be sex-reversed. XX males were positively identified by progeny testing, and significant family effects were found to influence sex ratios at normal temperatures as well as the response to masculinizing effects of elevated temperatures. In Anguilla, low-temperature incubation did not affect sex ratio in A. rostrata (Peterson et al., 1996), whereas male-biased sex ratios appear to be slightly enhanced by elevated larval incubation temperatures (Holmgren, 1996) in A. anguilla or by high stock densities in both species (Roncarati et al., 1997; Krueger and Oliveira, 1999). Based on field studies of lamprey (where gonadal differentiation can change during development; Lowartz and Beamish, 2000), environmental factors may influence sex ratio such that elevated temperatures reduce the incidence of males under high-growth conditions or lower population densities (Beamish, 1993; Docker and Beamish, 1994). In other fish where temperature influences on sex ratio have been specifically examined, no effects have been observed, including northern populations of F. heteroclitus and Cyprinodon variegatus (Conover and Demond, 1991), the mosquitofish (G. affinis) (Bennett and Goodyear, 1978), and the bloater (Coregonus hoyi) (Eck and Allen, 1993). In other fish, indications of temperature-dependent sex determination have been suggested. In channel catfish Ictalurus punctatus, sex is normally determined genetically by an XY system, but high temperature extremes applied during the critical period for sex determination result in female-skewed sex ratios, which indicate influence by environmental factors as well (Patino et al., 1996). In sockeye salmon (Oncorhynchus nerka), a temperature elevation occurring during embryonic development has been associated with a female-biased sex ratio (Craig et al., 1996), and similarly, elevated temperatures are associated with female-biased sex ratios in Epiplatys chaperi (Van Doorn, 1962) and G. aculeatus (Lindsey, 1962). At normal rearing temperatures (25 jC), the sex ratio of sea bass (D. labrax) populations is normally male biased, but low-temperature incubation (15 jC) during the labile period of gonad development results in all-male populations (Bla´zquez et al., 1998b; Pavlidis et al., 2000). In contrast, in hirame P. olivaceus, high temperature reduced the numbers of females (Tabata, 1995; Yamamoto, 1999), and in the barfin flounder V. moseri, a difference in rearing temperature from 14 to 18 jC near the time of gonadal differentiation results in equal sex ratios in the former to all male progeny in the latter (Goto et al., 1999). In marbled sole, Limanda yokohamae, masculinization has also been shown to be induced by elevated (25 vs. 15 jC) temperatures (Goto et al., 2000a), as have goldfish and black rockfish S. schlegeli (Goto et al., 2000b; Lee et al., 272 R.H. Devlin, Y. Nagahama / Aquaculture 208 (2002) 191–364 2000). Some temperature effects on sex determination may be quite subtle (e.g. in atipa Hoplosternum littorale), detectable only by careful examination of intrafamily responses that are otherwise masked in populations by genetic variance among different families (Hostache et al., 1995). A discussion of other factors (day length, radiation, water quality, crowding, fertilization timing) reported to influence sex ratio has previously been presented (Chan and Yeung, 1983). The above studies clearly reveal that sex determination can be influenced by external physical variables such as temperature in most fish families examined. In some cases, the species utilize these influences as a strategy to improve reproductive success, whereas in others, the effects on sex determination may not occur naturally, and may arise from disruptions of normal sex-determination processes under extreme environmental conditions. Indeed, the viability of germ cells of two species of fish (O. bonariensis and P. hatcheri) have been shown to be sensitive to elevated temperatures (Stru¨ssmann et al., 1998), suggesting that pathological effects on gonadal development may indeed occur. Similarly, temperature has been found to influence expression of a SRY-related Sox gene in a reptile (Western et al., 1999). cheers John Link to comment Share on other sites More sharing options...
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