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Anatomical Comparison of the
Cephalic Musculature of Some
Members of the Superfamily
Myliobatoidea (Chondrichthyes):
Implications for Evolutionary
Understanding
Gonzalez-Isais M. 2003. Anatomical Comparison of
the Cephalic Musculature of Some Members of the
Superfamily Myliobatoidea (Chondrichthyes):
Implications for Evolutionary Understanding. The
Anatomical Record Part A 271A: 259-272.
Background Information:
© Tracy Clark
http://www.divebums.com/FishID/Pages/butterfly_ray.html
Myliobatoidea
Myliobatoidea Species Studied:
Gymnura marmorata
(GMA)
California Butterfly Ray
http://www.fishbase.org.ph/Summary/SpeciesSumm
ary.cfm?id=2578
Gymnura micrura
(GMI)
Smooth Butterfly Ray
http://filaman.uni-kiel.de/Summary/SpeciesSummary.cfm?ID=257
Aetobatus narinari (AN)
Spotted Eagle Ray
http://www.fishbase.org
Mobula munkiana
(MM)
Munk’s Devil Ray
http://www.fishbase.org
Mobula thurstoni (MT)
Bentfin Devil Ray
http://www.fishbase.org
Myliobatis californica (MC)
Bat Eagle Ray
http://www.fishbase.org
Myliobatis longirostris (ML)
Snouted Eagle Ray
http://www.fishbase.org
Rhinoptera steindachneri (RS)
Pacific Cownose Ray
Http://www.fishbase.org
Muscles of the Dorsal Cephalic Region
• Precranial muscle (PM)
• Ethmoideo-parethmoidalis muscle (EPE)
• *Dorsal longitudinal bundles (DLB)
• Levator hyomandibulae muscle (LHM)
• Levator spiracularis muscle (LS)
• Superficial dorsal constrictor muscles 1-5
(DC1-DC5)
• Constrictor hyoideus dorsalis (CHD)
• *Cucullaris muscle (CC)
Muscles of the Cephalic Ventral Region
• Depressor rostri muscle
• Coracohyomandibularis
•
•
•
•
•
•
•
(DR)
*Superficial transverse
(ST) muscle and superficial
ventral constrictors (VC1VC5)
Coracoarcualis muscle (CA)
*Coracomandibular
muscle (CM)
Suborbitalis muscle (SB)
Adductor mandibulae
medialis muscle (AMM)
*Mandibular adductor
muscles (AM, AML1, and
AML2)
•
•
•
•
•
•
•
muscle (CHM)
*Depressor
hyomandibulae (DH)
Constrictor hyoideus
ventralis (CHV)
Coracobranchiales muscles
(CB)
*Y muscle (Y)
*Z muscle (Z)
M muscle (M)
Coracohyoideus muscle
(CH)
*Quadratomandibularis
ventral (QV)
Objective of the Study:
• The researchers attempted to describe the
anatomy of the cephalic dorsal and ventral
musculature of myliobatoids, as a basis for
future phylogenetic genus research.
Methods:
• Specimens were collected from areas
along the Gulf of Mexico, Gulf of
California, and the Pacific Ocean
• Larger specimens were dissected in the
field
• Smaller specimens were fixed in
formaldehyde 10% to be transported to a
laboratory and dissected at a later time
Methods:
• Conventional techniques were used for dissection,
focusing on dorsal and ventral cranial musculature
Dorsal View
Ventral View
Methods:
• For each muscle the following
characteristics were analyzed:
1. form disposition
2. fiber orientation
3. origin-point of attachment of a
muscle; end not easily
movable
4. insertion-point of attachment of a
muscle; end that is easily movable
Results:
Dorsal Musculature
• Overall, all taxa was fairly consistent with
the exception of some variation in two of
the muscles analyzed:
1. Dorsal Longitudinal Bundles
2. Cucullaris Muscle
Results:
Dorsal Longitudinal Bundles (DLB)
G. Micrura
and G. marmorata
Results:
Dorsal Longitudinal Bundles (DLB)
M. Californica
M. munkiana
Results:
Cucullaris muscle
M. longitostris
A. narinari
*Absent in A. narinari, M. thurstoni, and M. munkiana
Results:
Ventral Musculature
• Variations were found in the following muscles:
1.
2.
3.
4.
Depressor hyomandibulae
Quadratomandibularis muscle
Mandibular Adductor
Dorsal and Ventral Superficial Constrictor
Muscles
5. Coracomandibular Muscle
6. Y muscle
7. Z muscle
Results:
Depressor hyomandibulae
Reduced in: MC, ML, and AN; Absent in: MM, MT
G. micrura
M. californica
Results:
Quadratomandibularis Muscle
• Found only in
GMi and GMa
– Plesiomorphic
Characteristic
G. marmorata
*Absence of Quad. Muscle considered derived characteristic
Results:
Mandibular adductor muscles
• Increased size in ML, MC, AN, and RS
M. californica
G. micrura
Results:
Superficial Constrictor Muscles
• Reduced in MT and MM
• Fused in AN, MC, and ML
– Considered synapmorphy
G. Marmorata
M. Californica
M. munkiana
Results:
Coracomandibularis Muscle
-In MC, Ml, AN, and RS the muscle originates in the pectoral
girdle
-In GMI, GMA, MT, and MM the muscle originates in the
membrane where the coracoarcualis muscle inserts
A. narinari
M. munkiana
Results:
Y muscle and Z muscle
• These muscles were found in MC, ML, AN, and
RS
M. californica
Discussion:
• Differences in the ventral musculature are
related to feeding habits:
– AN, MC, ML, and RS hard-shelled mollusks
and crustaceans
– MM and MT are filtering species that feed
mainly on small crustaceans
Discussion:
Phylogenetic Studies
Previous Phylogenies
Discussion:
Phylogenetic Studies
Myliobatids
Rhinoptera
Mobula
Proposed Phylogeny
from data of this
paper
Conclusions:
1. Rhinoptera is the myliobatids’ sister group.
2. The results from this study alone are too
3.
general to base a phylogeny on, but the results
should be used for future phylogeny research.
Overall, a phylogeny can change drastically
depending on what aspect(s) of the specimen
a specific study is analyzing.