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Sexual dimorphism and potential horm...

Cagle, Mark D.

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Sexual dimorphism and potential hormonal modulation of feeding mechanics in Siamese fighting fish, Betta splendens.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Sexual dimorphism and potential hormonal modulation of feeding mechanics in Siamese fighting fish, Betta splendens./
Author:	Cagle, Mark D.
Description:	69 p.
Notes:	Source: Masters Abstracts International, Volume: 53-05.
Contained By:	Masters Abstracts International53-05(E).
Subject:	Endocrinology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=1563854
ISBN:	9781321137484

Sexual dimorphism and potential hormonal modulation of feeding mechanics in Siamese fighting fish, Betta splendens.
Cagle, Mark D.

Sexual dimorphism and potential hormonal modulation of feeding mechanics in Siamese fighting fish, Betta splendens. - 69 p.

Source: Masters Abstracts International, Volume: 53-05.

Thesis (M.S.)--Northern Arizona University, 2014.

This item is not available from ProQuest Dissertations & Theses.

Prey capture of the Siamese fighting fish, Betta splendens, involves ram (swimming toward and encompassing the prey) and suction (entraining prey in a flow field and pulling both water and prey into the mouth) components. To capture prey, B. splendens produce a coordinated suite of movements of the bony elements of the skull and jaws, including: lower jaw depression, hyoid depression, mouth-gape, cranial rotation, and premaxillary protrusion. Because male B. splendens also utilize their jaws in aggressive encounters with other males and to build bubble nests for the eggs, sexual selection may have produced gender-specific modifications of the head and jaws to facilitate reproductive behaviors. Modifications to the male head or jaws could present an evolutionary trade off: a decrease in suction feeding ability, beneficial for prey capture, for an increase in bite force, a trait correlated to reproductive success. Variation in skull or jaw morphology could lead to differences in the kinematics of prey capture between males and females. Prey capture mechanics were compared between males and females to determine if they produce different prey capture movements. We hypothesized that sexual dimorphism would be exhibited in feeding kinematics, with males demonstrating kinematics that should enhance biting performance, but may decrease suction-feeding performance.

ISBN: 9781321137484Subjects--Topical Terms:

610914
Endocrinology.

Sexual dimorphism and potential hormonal modulation of feeding mechanics in Siamese fighting fish, Betta splendens.
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020 $a 9781321137484
035 $a (MiAaPQ)AAI1563854
035 $a AAI1563854
040 $a MiAaPQ $c MiAaPQ
100 1 $a Cagle, Mark D. $3 3175744
245 1 0 $a Sexual dimorphism and potential hormonal modulation of feeding mechanics in Siamese fighting fish, Betta splendens.
300 $a 69 p.
500 $a Source: Masters Abstracts International, Volume: 53-05.
500 $a Adviser: Alice C. Gibb.
502 $a Thesis (M.S.)--Northern Arizona University, 2014.
506 $a This item is not available from ProQuest Dissertations & Theses.
506 $a This item must not be sold to any third party vendors.
520 $a Prey capture of the Siamese fighting fish, Betta splendens, involves ram (swimming toward and encompassing the prey) and suction (entraining prey in a flow field and pulling both water and prey into the mouth) components. To capture prey, B. splendens produce a coordinated suite of movements of the bony elements of the skull and jaws, including: lower jaw depression, hyoid depression, mouth-gape, cranial rotation, and premaxillary protrusion. Because male B. splendens also utilize their jaws in aggressive encounters with other males and to build bubble nests for the eggs, sexual selection may have produced gender-specific modifications of the head and jaws to facilitate reproductive behaviors. Modifications to the male head or jaws could present an evolutionary trade off: a decrease in suction feeding ability, beneficial for prey capture, for an increase in bite force, a trait correlated to reproductive success. Variation in skull or jaw morphology could lead to differences in the kinematics of prey capture between males and females. Prey capture mechanics were compared between males and females to determine if they produce different prey capture movements. We hypothesized that sexual dimorphism would be exhibited in feeding kinematics, with males demonstrating kinematics that should enhance biting performance, but may decrease suction-feeding performance.
520 $a Androgens and estrogens (sex steroid hormones) are the likely basis for sexual dimorphism in B. splendens. Hormonal mechanisms generate gender-specific differences in morphology and behavior that facilitate the different mating roles of the two sexes. While females use their trophic apparatus for feeding and respiration, males must also utilize their skull and jaws for aggressive displays and for tending the eggs. This study attempted to modulate prey capture mechanics by treating male fish with17beta-estradiol (E2). Adult male B. splendens were exposed to 10, 100, and 10,000 ng E2/L H2O. Using high-speed digital photography, feeding events were recorded in all treatment groups and gape, hyoid depression, cranial rotation, lower jaw depression, and premaxillary protrusion were measured. It was hypothesized that males treated with the estrogenic compound would exhibit a more female-like pattern of feeding kinematics post-treatment, based on the assumption that gape size may be behaviorally modified.
520 $a When feeding behavior was compared between males and females, male B. splendens have greater cranial rotation, gape, and lower jaw depression. Females were observed to be able to pull in prey from 1.5 gape-lengths away whereas males could only pull from one gape-length away. Thus, the larger magnitude cranial movements in males appears to reduce suction ability, potentially allowing elusive prey types to escape. These larger magnitude cranial movements could result from changes to the opercular linkage, a series of bones and muscles used to drive agonistic displays with other males and movements of the lower jaw.
520 $a It is possible that the contraction of two opercular muscles, the levator operculi and the dilator operculi, control opercular flaring and generate lower jaw depression and intraoral volume. Thus selection for one behavior may contribute to increased mouth-gape during feeding in males. It is also possible that variation in gape size and cranial movements could potentially be a naturally occurring phenomenon to prevent male and female Betta from competing for the same type of prey in the wild. On the other hand, captive males, unlike wild caught males, have been selectively bred over generations for aggression and bite performance, potentially resulting in the exaggerated cranial movements. Future studies with wild caught Betta males are necessary to assess this possible role of feeding dimorphism.
520 $a When the control and treatment groups were compared following hormonal exposures, the treatment groups were not significantly different from control males. This result suggests that adult exposure to estradiol does not alter prey capture mechanics, which implies that this trait is not directly controlled by sex steroids in adults. However, treatment with 10,000 ng E2/L H2 O induced a marked loss of color in 85 % of the males sampled, which suggests that sexually dimorphic color is a plastic trait. Female Betta appear to regard color intensity as a sign of fitness, and males may deepen their coloration during agonistic encounters. A loss of color as exhibited by 10,000 ng E2/L H2O treated males in this study would likely decrease the male's attractiveness to females and lower their success in besting a healthy male in competition---lowering their mating probability overall.
590 $a School code: 0391.
650 4 $a Endocrinology. $3 610914
650 4 $a Zoology. $3 518878
650 4 $a Aquatic sciences. $3 3174300
690 $a 0409
690 $a 0472
690 $a 0792
710 2 $a Northern Arizona University. $b Biological Sciences. $3 2104382
773 0 $t Masters Abstracts International $g 53-05(E).
790 $a 0391
791 $a M.S.
792 $a 2014
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=1563854