Regards,
Bruce.
Bruce Hansen, ANGFA, caring for our aquatic ecosystems.
Please visit us at http://www.ozemail.com.au/~fisher/angfa.htm
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> From: Jimmy Gaulden <jgaulde at ibm.net>
> To: bhansen at ozemail.com.au
> Subject: Male or Female Kubutu Rainbowfishes (Melanotaenia lacustris)?
> Date: Thursday, 12 March 1998 17:05
>
> INTRO: I have two Lake Kubutu Rainbowfishes (Melanotaenia lacustris).
> One is larger than the other. I call the small one Little Blue and the
> large one Big Blue and shall refer to them by these nicknames in this
> letter.
>
> I am reasonable sure Little Blue is a male.
>
> But what sex Big Blue is the question. Big Blue is another story. It has
> the physical and visible characteristics of a female Melanotaenia
> lucustris but can display the neon-like silver stripe like a male. I
> have a paradox. Big Blue has the physical and visible characteristics of
> a female and yet can produce the neon-like silver stripe that is a male
> characteristic. I am reasonable sure Little Blue is a male because he
> has all the characteristics
>
> According to Dr. Gerald R. Allen's book, from "Rainbowfishes In Nature
> and in the Aquarium", there are several attributes to use in identifying
> Rainbowfishes. A list of the attributes follows:
>
> 1.) "Males generally have brighter colors and longer dorsal fins (which
> are pointed posteriorly as opposed to rounded in females)."
> opposed to rounded in females)." YES Little Blue. NO Big Blue.
>
> 2.) "The length of the first dorsal fin is usually a reliable indicator.
> The first dorsal of males is longer and generally overlaps the beginning
> of the second dorsal fin when it is laid back." YES Little Blue. NO Big
> Blue. Little Blue has an overlapping dorsal fin. It is pointed too. Big
> Blue's dorsal fin barely reaches the a small portion of the base of the
> second dorsal fin. I never seen it laid back and overlapping the second
> dorsal fin. However, Little Blue's first dorsal fin definitely overlaps
> the second dorsal fin when laid back. There is a gap between Big Blue's
> first dorsal fin and the second dorsal fin. Even if it was laid back it
> would barely touch the leading edge of the second dorsal fin.
>
> 3.) "In females this first dorsal fin is much shorter and fails to reach
> the beginning of the second dorsal fin." NO Little Blue. YES Big Blue.
>
> Spawning behavior of Rainbows:
> 4.) "Males of most species also display a bright neon-like stripe on
> the forehead. The display continues for several minutes before the males
> succeeds in luring a partner to the selected site." YES Little Blue. YES
> Big Blue.
>
> On March 10, 1998, I saw Big Blue and Little Blue at the same time (at
> 6:55 p.m.) this evening with the neon-like silver stripe. First Big Blue
> produced the neon-like stripe and then, approximately thirty seconds
> later, Little Blue produced the neon-like silver stripe. And Both of
> them at this time displayed the spawning ritual by nudging each other
> near the pelvic fin.
>
> Little Blue has displayed the neon-like stripe more frequently than Big
> Blue. I have seen Big Blue display no more than four times.
>
> Is Big Blue's ability to produce a stripe on its forehead the exception
> to the rule or is it unknown that some female Rainbowfishes can produce
> the neon-like stripe on their forehead? That is the question twirling in
> my head.
>
> Any light you could shed on this contradictory and paradoxical situation
> would be appreciated. Jimmy.
>
>