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Neil
Aschliman
Research Training Program, 2004
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Introduction Beloniformes is a teleostean order comprising the needlefishes (Belonidae), sauries (Scomberesocidae), halfbeaks (Hemiramphidae), and flyingfishes (Exocoetidae). Rice fishes are a recent basal addition. Tibbetts' (1992) study of the pharyngeal jaw apparatus (PJA) and a total evidence analysis including nuclear and mitochondrial genes by Lovejoy (2000) strongly suggested paraphyly of Hemiramphidae. Both studies indicated that the five genera of internally fertilizing Indo-West Pacific (IWP) halfbeaks (Zenarchopteridae) are more closely related to needlefishes and sauries than to other halfbeaks and flyingfishes. Additional comparisons between the herbivorous Hemiramphidae and the carnivorous IWP halfbeak genus Zenarchopterus revealed important differences in the PJA. Lovejoy noted that the morphological component of his study is relatively small, and no sauries were included in Tibbetts' analysis of the PJA. Sauries are valuable commercial fishes and are important in the epipelagic food chain. There are two genera, each consisting of a large and a dwarf species.
The PJA of the Pacific saury (Cololabis saira) and the Atlantic saury (Scomberesox saurus) was examined to expand Tibbetts' 40-character data matrix and determine if sauries are more closely related to the needlefishes, to the IWP halfbeaks, or to the hemiramphid halfbeaks and flyingfishes.
In addition to analyzing the pharynx of sauries, we confirmed Tibbetts' (1992) coding of the 40 characters in a needlefish (Belone belone), halfbeak (Arrhamphus sclerolepis), and IWP halfbeak (Zenarchopterus buffonis). Dissection, light microscopy, and scanning electron microscopy were used to determine character states. Fourteen osteological pharyngeal characters were evaluated, including dentition, as were 12 myological characters. Other aspects of the morphology and life history, such as jaw length, fin shape, and the mode of fertilization were included in the matrix.
Additional species such as a flyingfish (Fodiator acutus) were examined to resolve ambiguities. Several characters in the matrix warranted comparison between the large and the dwarf (C. adocoetus and S. simulans) saury species.
Character 15, third pharyngobranchial bone association, was found to be problematic. The bones in Hemiramphus are suturally united, not fused as reported in Tibbetts (1992). Except for those confirmed by cross section, states for taxa previously described as fused were changed to "?". The matrix of 40 characters and 17 taxa was analyzed with PAUP* using the heuristic search algorithm. All characters were unweighted and unordered. Decay indices were calculated with TreeRot. A flyingfish (Parexocoetus) was used to root the ingroup analysis because of its strongly supported basal position within the Beloniformes (Lovejoy 2000).
PAUP* yielded eight equally parsimonious trees (70 steps, consistency index = 0.814, retention index = 0.938). A strict consensus describes a polytomy obscuring the structure of the externally fertilizing halfbeak group. Monophyly of the sauries and of the IWP halfbeaks is well-supported, as is monophyly of the two examined needlefish taxa. Pairing of the saury + needlefish and IWP halfbeak clades is strongly supported (decay index = 19, bootstrap = 100).
The origin of the retractor dorsalis muscle begins more posteriorly in all sauries than in the other examined taxa. Instead of beginning on vertebra two or three, it begins on vertebra six in the large species and four or five in the dwarfs. The caudal-most row of teeth on the fifth ceratobranchial of S. saurus is hooked posteriorly. Tibbetts (1992) described this as autapomorphic for Tylosurus. A new state was defined for orientation of teeth on the second pharyngobranchial of large saury species. Medial teeth are hooked antero-medially in these species.
Differences within saury genera may be due to size reduction in dwarfs, such as a less pronounced displacement of the retractor dorsalis origin due to a reduction in the number of vertebrae.
The authors thank many individuals at the USNM. V. G. Springer and G. D. Johnson lent materials and their vast knowledge of the PJA, and L. R. Parenti with staining protocols. S. D. Whittaker provided training and coated samples for SEM. T. Orrell assited with PAUP*, and S. J. Raredon with photography. Thanks to Battelle for their donation to and support of marine science in the RTP. Funding for this study was provided by a grant from the Alice Eve Kennington Endowment.
Lovejoy, N. R. 2000. Reinterpreting recapitulation: systematics of needlefishes and their allies (Teleostei: Beloniformes). Evolution 54:1349-1362. Tibbetts, I. R.
1992. The trophic ecology, functional morphology and phylogeny of the
Hemiramphidae (Beloniformes). Unpublished Ph.D. dissertation, University
of Queensland, Brisbane, 370 pp. Want to ask a question? Visit the Message Board Virtual
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