|
21-25 of 25 messages
|
Previous
Page 3 of 3
|
|
RE: head sizes correlated to prey size?
|
Reply
|
|
by theemojohnm on December 24, 2009
|
Mail this to a friend!
|
To a certain extent, within an absolutely pre-determined gap.
Take Care,
-John Mendrola.
|
| |
|
RE: head sizes correlated to prey size?
|
Reply
|
|
by FSB on December 24, 2009
|
Mail this to a friend!
|
|
I dunno, Terry... I'm pretty sure that if I quit smoking and started lifting weights in a gymn everyday I'd probably drop dead... On the other hand, since the only access I have to the web at home is my 10-year old's DSi, I AM developing a certain degree of skill at typing with this little stylus thingie on a touch screen, but my son obviously possessed that gene in spades long before I ever had it to pass on, so how does that work? Computers have messed everything up... oh well - Merry Christmas to all, and thanks for such a fun thread [and the fact that the DSi can't handle facebook].
|
| |
|
RE: head sizes correlated to prey size?
|
Reply
|
|
by CAISSACA on December 27, 2009
|
Mail this to a friend!
|
Here are a few published studies on this:
Does prey size induce head skeleton phenotypic plasticity during early ontogeny in the snake Boa constrictor?
Author(s): Schuett GW, Hardy DL, Earley RL, Greene HW
Source: JOURNAL OF ZOOLOGY Volume: 267 Pages: 363-369 Part: Part 4 Published: DEC 2005
Abstract: Diet was manipulated in juveniles of the snake Boa constrictor(Serpentes: Boidae) to test the hypothesis of whether prey size induces phenotypic plasticity of the head skeleton. Additionally, the onset of sexual size dimorphisms (SSDs) was determined under a feeding schedule where total prey mass consumed by snakes was held constant. Twenty-three neonatal B. constrictor from a single-sired litter were placed into two treatment groups but maintained under identical environmental conditions. Group 1 (small-food treatment) was fed weanling mice throughout the entire study; group 2 (large-food treatment) was fed weanling mice, followed by rats of increasing size as the size of the snakes increased. At the termination of the study, group 1 consumed more meals but both groups consumed an equivalent mass of rodents. The snakes were measured twice during the study (5 weeks and 58 weeks). All measurements were obtained while the snakes were under general anaesthesia. Linear measurements of the head skeleton (premaxilla-basioccipital (rostrum-occipital) length, ROL; mandible length, ML) were derived from radiographs. The remaining measurements were snout-vent length (SVL), body length (BL), tail length (TL), and body mass (BM). Treatment effects between groups were equivalent, with the exception of BM and TL (group 1 > group 2), and interactions between main effects were not statistically significant. Between-group differences in ROL and ML were not significant; thus, prey size did not exert an influence on growth of the head skeleton. In contrast, significant sex effects on SVL and BL (females > males) and TL (males > females) were detected, and sex effects on BM (females > males) approached significance. Because SSDs emerged during early ontogeny under conditions where prey mass consumed was held constant, a genetic role is implicated..
So, in a nutshell, no effect of prey size on skull shape in Boa consrtictor
Plastic vipers: influence of food intake on the size and shape of Gaboon vipers (Bitis gabonica)
Author(s): Bonnet X, Shine R, Naulleau G, Thiburce C
Source: JOURNAL OF ZOOLOGY Volume: 255 Pages: 341-351 Part: Part 3 Published: NOV 2001
Abstract: Repeated measurements of captive-born Gaboon vipers Bitis gabonica from an inbred stock examined the degree to which an animal's size and shape are affected by food intake. We also used the level of asymmetry in dorsal coloration as an index for possible genetic (inbreeding?) effects. Both of these factors, and the interaction between them, affected phenotypes of the young snakes. Snakes raised with abundant food differed from their less well-fed siblings not only in size, but also in body mass relative to snout-vent length, head length relative to snout-vent length, head width relative to head length, and fang length relative to jaw length. Hence, our data show that body proportions (including the feeding apparatus) can be influenced by the environment after birth.
Here, looking at the paper itself, the authors showed that snakes fed frequently (high food intake) had shorter, broader skulls than snakes fed infrequently (low intake), which had longer, narrower skulls - so food intake did affect head size and proportions.
Overall, there is no major a priori reason why differences in food size eaten by juveniles should not affect head size or shape in later life in snakes. Most characters are partly controlled by your genes, and partly by environmental effects. All it takes is some way for environmental influences to feed back either to gene expression or to growth through resource limitation. Indeed, one could hypothesise that it would be selectively advantageous to have such a feedback system so that growth can be adjusted to the available diet.
This is a totally different issue from that of Lamarckian evolution - this would require the characteristics acquired as a result of environmental effects to become genetically transmissible, for which there is of course no evidence.
|
| |
|
RE: head sizes correlated to prey size?
|
Reply
|
|
by theemojohnm on December 27, 2009
|
Mail this to a friend!
|
Thanks Wolfgang!
Expression of a trait triggered by environmental factors, EARLY in development seems to occur frequently, though usually in small amounts.
I, just as other have previously stated, seen a few atrox with HUGE heads, even in proportion to "normal" body, length and girth.
However, in your opinion, how accurate is it to say that one of these huge-headed atrox may have come once from a "normal-sized" animal? Certainly small differences are expressed, but such a dramatic development surely could not occur in the short time before that single animal matures, and stops developing?
Can't say that I have ever seen a retic with all that big a head (at least in contrast to "normal-large-constrictor" head/body proportions).
But I have seen C. atrox, A. contortrix, and N. sipedon with exceptionally large heads, dramatic even.
These animals surely could not have been born in "normal" proportion, and accomplished such a dramatic curve in development, before maturity was reached, and development slowed. Especially in a cold-blooded animal, I don't see it. I'm sure there are some exceptions. I can think of a few, but they still seem, a great deal, based on locality-specific populations genetics.
Very interesting info. Thank you for the links. I tried to pull something from Science Daily with relevance to this topic, but came up... unsuccessful. LOL.
Have something to send you actually. Maybe I'll shoot you an email. If you have time and would mind scanning through it, I would greatly appreciate it.
Thanks & Happy Holidays.
Take Care,
-John Mendrola.
|
| |
|
RE: head sizes correlated to prey size?
|
Reply
|
|
by CAISSACA on December 29, 2009
|
Mail this to a friend!
|
Hi John,
Sorry, late reply.
I really have no idea how plastic or heritable head size (and other characters) are in snakes, and what might impact on the final product. There is a lot of cool work to be done there, and the papers I listed really only just start to scratch the surface. I don't doubt that many differences we see between populations will be genetically encoded, but how tight that control is, we don't really know for sure.
By all means send me what you mentioned, will be happy to take a look at it and make any suggestions that spring to mind.
Have a great New year,
Wolfgang
|
| |
|
Email Subscription
You are not subscribed to this topic.
Subscribe!
My Subscriptions
Subscriptions Help
Check our help page for help using
, or send questions, comments, or suggestions to the
Manager.
|
