[Onanist (OP)]

now admittedly, it has been some time since i last slept, and this may be having an adverse effect on my logical faculties, but i think this one is a monster of a question.

you know flat fish? like plaice for instance?

well i have observed, both in aquariums, and on dinner plates, that it is possible to determine by the position of their fins, top and bottom, whether both of their eyes are positioned on their left or their right sides.

furthermore, i have observed that in the same species of fish, and indeed even in the same shoal (or tank in the aquarium), it is possible to find fish with their eyes on either side.

on my last visit to the london aquarium, having spent several sleepness nights worrying about this, and several drunken conversations in the pub expressing my concerns, i intentionally checked to see which way up the flatfish were swimming, and was delighted to see there was a variety, but also a majority sided fish. unfortunately i cannot remember which side the majority of the fish had their eyes on.

now my question is this:

why is there a variety, and what determines which side the flatfishes eyes will migrate to?

is it genetic, or is it determined by enviromental factors? is it gender specific? does anybody even know? am i the only person ever to have thought about this?

i apologise for the length, and the rambling nature of this post.

[Onanist (OP)]

do any scientists actually post here by the way?

i found the place by accident.

i imagine real life marine biologists are probably far too busy, and indeed wet, to spend very much time at their computers posting on internet forums.

[neilep]

do any scientists actually post here by the way?

i found the place by accident.

i imagine real life marine biologists are probably far too busy, and indeed wet, to spend very much time at their computers posting on internet forums.

Yes...yes they do !...however, they are outnumbered by us non scientific peeps !!

Welcome to the site by the way !!

How did you ind us by accident ?..and are you a scientist ?

[Onanist (OP)]

do any scientists actually post here by the way?

i found the place by accident.

i imagine real life marine biologists are probably far too busy, and indeed wet, to spend very much time at their computers posting on internet forums.

Yes...yes they do !...however, they are outnumbered by us non scientific peeps !!

Welcome to the site by the way !!

How did you ind us by accident ?..and are you a scientist ?

i'm most definately not a scientist. just an extremely curious layman.

which answers your first question. i found the site because i was up all night googling things.

which is only slightly less perverse than it sounds.

[neilep]

do any scientists actually post here by the way?

i found the place by accident.

i imagine real life marine biologists are probably far too busy, and indeed wet, to spend very much time at their computers posting on internet forums.

Yes...yes they do !...however, they are outnumbered by us non scientific peeps !!

Welcome to the site by the way !!

How did you ind us by accident ?..and are you a scientist ?

i'm most definately not a scientist. just an extremely curious layman.

which answers your first question. i found the site because i was up all night googling things.

which is only slightly less perverse than it sounds.

Well it's nice to have you aboard !!...lets hope a passing left-handed-flat-fish expert passes by and answers your question !!

[Onanist (OP)]

i hope so.

i'm aware there are some left sided, and right sided species of flatfish, but nobody seems to be able to tell me why some species seem to be either/or.

[SquarishTriangle]

Excerpt from:
C. A. Bergstrom and A. R. Palmer. (2007) Which way to turn? Effect of direction of body asymmetry on turning and prey strike orientation in starry flounder Platichthys stellatus (Pallas) (Pleuronectidae). Journal of Fish Biology 71:3, 737–748:

Asymmetry, or lateral bias in trait expression, is a common phenomenon of life. Divergence in form between left and right versions of a character is often associated with functional specialization between them, and as such, selection for asymmetry may occur if this specialization incurs greater fitness to the individual. Ear positional asymmetry in owls (Norberg, 1978), claw shape asymmetry in lobsters (Govind & Pearce, 1986; Pratt & McLain, 2002), wing pattern asymmetry in male speckled wood butterflies (Windig & Nylin, 1999), and hemispheric brain asymmetry in vertebrates (Bisazza et al., 1998) all are examples of specialization of function between left and right sides that have ecological and adaptive importance.

At the population level, asymmetry can exhibit lateral monomorphism, where all individuals are biased in the same direction, or lateral polymorphism, where conspicuous morphological asymmetry is present in both left-biased and right-biased forms in various proportions. In both cases, there may be adaptive significance to the asymmetry regardless of the direction of bias. However, cases of lateral polymorphism raise the issue of the significance of direction: why are both left- and right-biased individuals occasionally present in the same species? Does the direction of bias affect ecological interactions? To date, there is little understanding of the evolutionary and developmental mechanisms resulting in lateral polymorphism or of the importance of the actual direction of asymmetry (but see Palmer, 2004).

In general, polymorphisms are maintained by frequency-dependent selection or by variable selection causing specialization of each morph to a specific micro-niche (Fisher, 1930; Maynard Smith, 1989). The importance of frequency-dependent selection (Gross, 1985; Sinervo & Lively, 1996; Rainey et al., 2000) and variable selection (Cain & Sheppard, 1954; Hedrick, 1986; Smith, 1993; Sandoval, 1994; Reimchen, 1995; Smith & Skúlason, 1996) in maintaining variation within species is widespread across taxa. In the case of lateral polymorphisms, negative frequency-dependent selection is a plausible mechanism that maintains variation in human handedness (Raymond et al., 1996; Billiard et al., 2005), direction of bill crossing in crossbills (Benkman, 1996), and mouth twisting direction in scale-eating cichlids (Hori, 1993), but examples of ecological segregation between lateral morphs and variable selection (frequency independent) maintaining lateral polymorphisms are rare.

Platichthys stellatus (starry flounder), a pleuronectid flatfish found in the north Pacific, demonstrates a remarkable geographical pattern in body asymmetry, and is an excellent species with which to study the evolutionary mechanisms maintaining lateral polymorphism. Platichthys stellatus, like all flatfish, exhibits conspicuous lateral asymmetry in numerous traits; most obvious of which is the migration of one eye to the other side of the head during metamorphosis (Fig. 1a). Additional changes related to eye migration include asymmetrical pigmentation (Fig. 1b), and a behavioural shift from larvae that exhibit upright, open-water swimming to juveniles and adults that lie on the ocean floor, eyed side up (Norman, 1934). Platichthys stellatus is unusual in that it exhibits lateral polymorphism for the side of the body on which the eyes lie, dextral fish having both eyes on the right and sinistral fish having both eyes on the left (Fig. 1c). The evolution of lateral polymorphism in flatfish is rare (seven of approximately 715 species), and occurred independently throughout the order Pleuronectiformes (Munroe, 2005). Of these seven polymorphic species, only P. stellatus exhibits a large-scale geographical cline in the proportion of dextral and sinistral morphs across its range. A polymorphic congeneric, P. flesus, also exhibits geographical variation in this proportion throughout Europe (Fornbacke et al., 2002) but this is much less than the variation seen in P. stellatus.

In the early 1900s, reports of the relative frequency of sinistral and dextral morphs of P. stellatus demonstrated a remarkable shift from equal numbers of both morphs in central California, to 75% sinistral morphs in Alaska and 100% sinistral morphs in Russia and northern Japan (Hubbs & Kuronuma, 1942).

[Onanist (OP)]

so the short answer is, nobody knows exactly why, or what the mechanisms are that dictate whether a fish will be left or right sided?

i suppose similar to the way nobody knows exactly why a similar variance in right and left brain hemisphere dominance exists in humans.