Branchial Muscles of Five Eel Families — Nelson 
363 
jaws and apparently constitute, with the pharyn- 
geal jaws, an advancement or specialization in 
the feeding mechanism. 
The common course and attachment of the 
retractors, both ventral and dorsal, to the ver- 
tebral column in morays are evidence that the 
muscles act together, simultaneously retracting 
both upper and lower tooth plates. Indeed, the 
construction of the plates and their supporting 
bones prohibits independent movement of the 
ventral and dorsal plates. Protraction probably 
occurs through the contraction of the sub- 
pharyngealis and the dorsal muscles joining 
the cranium and gill arches. Protraction and 
retraction probably succeed one another during 
the swallowing of prey. It is likely that, in 
the morays, the pharyngeal jaws and the mus- 
cles attached to them enable these forms to 
transport relatively large prey from the jaws 
into the esophagus, a distance which in eels 
is secondarily lengthened (Nelson, 1966). 
Thus, these structures appear to be adapted to 
the known predatory habits of the morays. 
SUMMARY 
1. Branchial muscles are described for six 
genera representing five eel families: Conger 
(Congridae), Anguilla (Anguillidae) , Morin- 
gua (Moringuidae) , Kaupichthys (Xenocon- 
gridae), Uropterygius and Gymnothorax 
(Muraenidae) . 
2. In the examined forms, muscles as well 
as gill arches suggest stages in an evolutionary 
sequence, with the Congridae being the most 
primitive and the Muraenidae being the most 
advanced. 
3. Dorsal and ventral retractor muscles oc- 
cur in all species examined. In eels of the sub- 
family Muraeninae they acquire secondarily an 
attachment to the vertebral column. 
4. Gill arch muscles and pharyngeal jaws 
of muraenids are adaptations probably enabling 
these fishes to swallow large prey. 
REFERENCES 
Bertmar, G. 1962. On the ontogeny and evo- 
lution of the arterial vascular system in the 
head of the African characidean fish Hep- 
setus odoe. Acta Zool. 43:255-294, 12 figs. 
Dietz, P. A. 1912. Vergelijkende Anatomie 
van de Kaak- en Kieuwboogspieren der 
Teleostei. Leiden. 196 pp., 25 figs. 
• 1914. Beitrage zur Kenntnis der 
Kiefer- und Kiemenbogenmuskulatur der 
Teleostier. I. Die Kiefer- und Kiemen- 
bogenmuskeln der Acanthopterygier. Mitt. 
Zool. Stat. Neapel 22:99-162, 45 figs. 
1921. Uber die systematische Stellung 
der Gadidae. Zugleich Nr. 2 der "Beitrage 
zur Kenntnis der Kiefer- und Kiemenbogen- 
muskulatur der Teleostier.” Mitt. Zool. Stat. 
Neapel 22:433-457, 14 figs. 
Edgeworth, F. H. 1935. The Cranial Muscles 
of Vertebrates. Cambridge Univ. Press, 
viii -j- 300 pp., 841 figs. 
Greene, C. W., and C. H. Greene. 1913. 
The skeletal musculature of the king salmon. 
Bull. Bur. Fish. 33:25-59, 14 figs., 2 pis. 
Kesteven, H. L. 1943. The evolution of the 
skull and the cephalic muscles. A compara- 
tive study of their development and adult 
morphology. Part I. The fishes {continued') . 
Mem. Austral. Mus. 8:63-132, 69 figs. 
Holstvoogd, C. I960. The importance of the 
retractores arcuum branchialium for the 
classification of teleostean fishes. Bull. Aquat. 
Biol. 2:49-50. 
1965. The pharyngeal bones and 
muscles in Teleostei, a taxonomic study. 
Proc. Konikl. Nederl. Akad. Wetens., Ser. 
C, 68:209-218, 12 figs. 
Nelson, G. J. 1966. Gill arches of teleostean 
fishes of the order Anguilliformes. Pacific 
Sci. 20:391-408, 58 figs. 
1967. Branchial muscles in some gen- 
eralized teleostean fishes. Acta Zool. [In 
press.] 
Petukat, S. 1965. Uber die arteriellen Gefass- 
stamme bei den Teleostiern. Zool. Beitr. 
11:437-515, 34 figs. 
Vetter, B. 1878. Untersuchungen zur ver- 
gleichenden Anatomie der Kiemen- und 
Kiefermusculatur der Fische. Jena Z. Natur- 
wiss. 12:431-550, pis. 12-14. 
