The Gill-Arch Musculature of Protanguilla, the Morphologically Most Primitive Eel (Teleostei: Anguilliformes), Compared with That of Other Putatively Primitive Extant Eels and Other Elopomorphs

Victor G. Springer; G. David Johnson

doi:10.1643/CI-14-152

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Article Contents

MATERIALS AND METHODS
ANATOMICAL ABBREVIATIONS WITH DEFINITIONS AND DISCUSSIONS
DESCRIPTIONS OF BRANCHIAL MUSCULATURE IN ANGUILLIFORM TAXA
CONCLUSIONS
ACKNOWLEDGMENTS
LITERATURE CITED

Editorial Type:

Article Category: Research Article

Online Publication Date: 20 Aug 2015

The Gill-Arch Musculature of Protanguilla, the Morphologically Most Primitive Eel (Teleostei: Anguilliformes), Compared with That of Other Putatively Primitive Extant Eels and Other Elopomorphs

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Page Range: 595 – 620

DOI: 10.1643/CI-14-152

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The gill-arch musculature and associated aspects of the skeleton of the anguilliforms Protanguilla, Conger, Anguilla, and the synaphobranchids Synaphobranchus and Simenchelys are described, illustrated, and compared. We identify nine anguilliform synapomorphies, seven myological and two osteological and all but two reported for the first time. We also describe one myological and one osteological synapomorphy of the Anguilliformes minus Protanguilla. Our study strongly corroborates the monophyly of the Anguilliformes, which has never been seriously challenged by morphological evidence, and is also supported by molecular analyses. Furthermore, it offers additional morphological support for placing Protanguilla as the sister group of all other eels. The condition of many gill-arch skeletal and muscular features are also treated in other elopomorphs and, occasionally, osteoglossomorphs and more primitive actinopterygians. For comparison, we also include the description of the gill-arch muscles of a specialized eel species of the family Serrivomeridae and discuss analyses of its closest family relationships as indicated by several molecular studies.

Fig. 1.

Cladogram showing suprageneric taxa referred to in the present study extracted from the molecular study of Betancur et al. (2013), of which the lower part agrees with morphological evidence of Grande (2010) and the upper part with Arratia (1999, 2000a, 2000b, 2010, etc.). For clupeocephalan intrarelationships see Springer and Johnson (2004:fig. 3).

Fig. 2.

Protanguilla palau, USNM 396051, dorsal (A) and posterior (B) views of gill-arch musculature.

Fig. 3.

Protanguilla palau, USNM 396051, ventral view of ventral gill-arch musculature.

Fig. 4.

Conger cinereus, USNM 115969, dorsal gill-arch musculature (from S&J:pl. 21). (A) Dorsal view: right-side TPb3-Eb4 and Od4 cut away and ligamentous sheet removed to reveal underlying muscles; (B) left side posterior view; (C) lateral view of right side fourth gill-arch reversed; (D) C. triporiceps, ANSP 106182, left-side gill arches with gray areas indicating muscle insertions based on C. cinereus.

Fig. 5.

Conger cinereus, USNM 311286, ventral view of ventral gill-arch musculature; right-side R4Cm bisected to reveal overlying R4; Bb1 truncated.

Fig. 6.

Anguilla rostrata, USNM 340815, dorsal gill-arch musculature (from S&J:pl. 22; with labels GF1 and GF2 re-interpreted and re-labeled as Ad1 and Ad2). (A) Dorsal view (left side LE4 should pass lateral to LI1; right-side LI1 deflected medially to reveal MPb2-Eb1, some levators truncated); (B) left side, posterior view; (C) left-side dorsal gill-arch skeleton with shaded areas to show muscle insertion positions.

Fig. 7.

Anguilla rostrata, USNM 190998 (with additions for damaged muscles) from USNM 314441, ventral view of ventral gill-arch muscles; right-side R4Cm bisected to reveal overlying muscles; Bb1 truncated; enlarged small inset drawing at upper left, to show position of ObV3 (broken lines) dorsal to R4.

Fig. 8.

Synaphobranchus sp., USNM 316662, dorsal gill-arch musculature (from S&J:pl. 23); ER present, but not shown in any view. (A) Dorsal view: left-side OD3-4 bisected to expose underlying muscles, MPb2-Eb2 not shown (see C); (B) lateral view, right side reversed, SO not shown; (C) S. kaupii, VIMS uncataloged, cleared-and-stained, left-side dorsal gill-arch skeletons, with MPb2Eb2 and insertion position of LI2 from USNM 316662 indicated.

Fig. 9.

Synaphobranchus kaupii, USNM 396609, ventral view of ventral gill-arch muscles; AntCh and Hyh truncated.

Fig. 10.

Synaphobranchus kaupii, USNM 396609, dorsal view of ventral gill-arch muscles; AntCh truncated.

Fig. 11.

Simenchelys parasitica, USNM 372009; (A) dorsal view of dorsal gill-arch muscles; right-side OD4 bisected to show insertion of LI2 and unilateral attachment of TPb4 to UP4; (B) left side, posterior view.