The Hyopalatine Arch Of A 25 Mm Larva Of Synbranchus And Homology Of The Single Pterygoid In The Synbranchidae (Teleostei : Synbranchiformes)

4 Pages·2003·2.6 MB·English

by  R Britz

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
116(2):337-340. 2003.
mm
The hyopalatine arch of a 25 larva of Synbranchus and
homology of the single pterygoid in the Synbranchidae
(Teleostei: Synbranchiformes)
Ralf Britz, Sandra Favorito, and G. David Johnson
(RB) Division Of Fishes, National Museum of Natural History, Smithsonian Institution,
Washington D.C. 20560, U.S.A., and Lehrstuhl fiir Spezielle Zoologie, Universitat Tubingen,
Auf der Morgenstelle 28, 72076 Tubingen, Germany, e-mail: [email protected];
(SF-A) Universidade de Sao Paulo, Museu de Zoologia, Caixa Postal 42594, Sao Paulo, SP,
04299-970, Brazil, e-mail: [email protected];
(GDJ) Division Of Fishes, National Museum of Natural History, Smithsonian Institution,
Washington D.C. 20560, U.S.A., e-mail: [email protected]
—
Abstract. Identity of the single pterygoid bone in Synbranchidae is eval-
mm
uated based on a 25 larva of Synbranchus. Two hypotheses have been
proposed as to its homology: it is 1) the endopterygoid or 2) the ectopterygoid.
We show that the bone in question develops in the position of the ectopterygoid
and therefore represents the homologue of this bone in other teleosts. Thus
synbranchids lack the endopterygoid, an observation that invalidates a previ-
ously proposed synapomorphy of this family and the channids (snakeheads).
Synbranchidae, or swamp eels, are a both, channids and synbranchids. The sin-
family of highly derived eel-like acantho- gle pterygoid of synbranchids was consid-
&
morphs, comprising 17 species (Bailey ered an ectopterygoid by Regan (1912),
Gans 1998) from fresh and estuarine waters Rastogi (1964), Rosen and Greenwood
of Middle and South America, Cuba, West (1976), Gosline (1983), Travers (1984), and
Africa, Asia, and the Indo-Australian Ar- Britz (1996), and an endopterygoid by Lau-
chipelago (Nelson 1994). Several species der & Liem (1983). However, none of these
are well known for their amphibious habits authors specifically addressed the problem
and the presence of accessory air breathing of the homology of this bone with respect
&
organs (see e.g., Rosen Greenwood 1976, to the ectopterygoid or endopterygoid of
Liem 1987, Munshi et al. 1989) that enable other teleosts. In the present paper we de-
mm
them to undertake extensive overland ex- scribe the hyopalatine arch of a 25 lar-
cursions. val specimen of Synbranchus sp., to resolve
There are two hypotheses about the re- the identity of the synbranchid pterygoid.
lationships of the Synbranchidae to other
acanthomorph taxa: 1) synbranchids are the Material and Methods
&
sister group of channids (Lauder Liem
A
1983) and 2) synbranchids are the sister cleared and double stained larval Syn-
group of mastacembeloids (= mastacem- branchus sp. (USNM 372713) of 25 mm
belids plus chaudhuriids) (Travers 1984a, total length was studied. A Zeiss Tessovar
& &
Johnson Patterson 1993, Britz Kottelat was used to photograph the specimen. Ad-
2003). ditional comparative material comprised:
One of the characters cited as support for Mastacembelidae; all cleared and stained:
& AMNH
Lauder Liem's (1983) hypothesis is the Mastacembelus erythrotaenia:
presence of an enlarged endopterygoid in 42129 (1, 277 mm); Mastacembehts sp. (as
338 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
AMNH
Macrognathus aculeatus) 097654 perichondral ossification is present, the de-
(1, 158 mm); Macrognathus pancalus: veloping quadrate, with the usual poster-
AMNH
217414 (8, 4.5-36 mm). oventral process of membrane bone. The
Synbranchidae; cleared and stained: Ma- developing metapterygpoid is present as a
MCZ
crotrema caligans: AlXOl (2, 172— thin lamina of perichondral bone surround-
178 mm), Ophisternon aenigmaticum: ing the posterodorsal corner of the pars
AMNH
31573 (1, 72 mm); Synbranchus quadrata et metapterygoidea. The pterygoid
AMNH
marmoratus: 30213 (1, 142 mm), extends anteriorly as an elongate thin lam-
AMNH MCZ
74541 (1, 47 mm), 52376 (3, ina of bone ventral to the anterodorsal cor-
65-140 mm; 1, disarticulated); Monopterus ner of the pars quadrata (Fig. lA, B). The
AMNH
albus: 41579 (1, 167 mm); dry elongate cartilage of the pars autopalatina
skeletons: Ophisternon aenigmaticum (as sits more anteriorly in the roof of the mouth
USNM
Synbranchus marmoratus): 111347 and bears a long anterolaterally directed
(1, partial skeleton); Monopterus sp. (as process, the distal tip of which articulates
AMNH
Synbranchus bengalensis): 220023 with the lacrimal. Ventral to this cartilage
(1, ca. 550 mm). is a small splint of bone, the developing
Terminology for the cartilaginous parts dermopalatine (Fig. lA). The lower jaw
&
of the hyopalatine arch follows Arratia consists of the long Meckel's cartilage, its
Schultze (1991). anterior part covered laterally by the den-
tary, which bears a few teeth, and its pos-
Results terior part by the angular. The retroarticular
is present as a small ossification at the most
mm
The 25 larva of Synbranchus sp. still posterior tip of Meckel's cartilage, but the
has a large yolk sac and prominent pectoral articular is not yet developed.
fins. The hyopalatine arch is largely carti-
laginous (Fig. lA). The hyosymplectic car- Discussion
tilage articulates with the otic capsule ofthe
chondrocranium. In the area around the fo- In most actinopterygians, two dermal
ramen for the hyomandibular branch of the bones, the endopterygoid and the ectopter-
facialis, there is a perichondral ossification, ygoid, cover the medial face of the devel-
the hyomandibular, which bears a conspic- oping palatoquadrate between the pars
&
uous process of membrane bone that ex- quadrata and pars autopalatina (Arratia
tends ventrally between the body of the car- Schultze 1991). Usually, the pars quadrata
tilage and the pars metapterygoidea of the and the pars autopalatina are connected by
palatoquadrate. A thin perichondral ossifi- a thin strip of cartilage during at least some
cation, the symplectic, surrounds the anter- period in early development. The endopter-
oventral process of the hyosymplectic car- ygoid ossifies dorsomedial to this cartilage
tilage. The opercle, which articulates with and the ectopterygoid ventromedial to it
&
a posterior process of the hyosymplectic (see e.g., Arratia Schultze 1991:figs. 14,
&
cartilage, and the remaining three opercular 15; Britz 1996:figs. 3-5; Britz Johnson
bones are present as thin platelets of bone. 2002:figs. 4, 5). Even when the cartilagi-
The palatoquadrate comprises two uncon- nous connection between the pars quadrata
nected parts, the posterior pars quadrata et and the pars autopalatina is resorbed during
metapterygoidea and the anterior pars au- ontogeny, a small projecting tip on the an-
topalatina (Fig. lA). The former is a rough- terodorsal face of pars quadrata usually re-
ly triangular cartilage, the ventral tip of mains for some time and can be used as a
which articulates with the lower jaw. landmark. Such a stage is shown for a mas-
Around this articulation and the lower third tacembelid species in Britz (1996: Fig. 5).
of the pars quadrata et metapterygoidea a This landmark is also useful for taxa in
VOLUME NUMBER
116, 2 339
exoccipital
frontal
first vertebra
nasal
mesethmoid
vomer
opercle
premaxilla
pars autopalatina
dermopalatine
maxilla
dentarv
A angular / nA quadrate
Meckel's cartilage retroarticular
B
lateral ethmoid
mesethmoid
hvomandibular
palatine
c quadrate mm
0.5
Fig. 1. Synbranchus sp., 25 mm: A, Skull and anterior two vertebrae, lateral view, cartilage white, bone
light grey; B, Photograph ofthe hyopalatine area, lateral view, arrow points to ectopterygoid; C, S. marmorotus.
47 mm, hyopalatine arch and anterior part of neurocranium, lateral view, modified from Britz (1996), cartilage
white, bone light grey.
340 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
—
which the pars quadrata and the pars auto- within osteichthyans. Journal of Morphology
208:1-81.
palatina are never connected by cartilage.
mm Bailey, R. M., & C. Gans. 1998. Two new synbranchid
The pterygoid bone of the 25 Syn-
fishes, Monopterus roseni from PeninsularIndia
—
branchus is located ventromedial to the and M. desilvai from Sri Lanka. Occasional
projecting anterodorsal corner of the pars Papers ofthe Museum ofZoology University of
Michigan 726:1-18.
quadrata.
Britz, R. 1996. Ontogeny of the ethmoidal region and
Thus, the position of the developing pter-
hyopalatine arch in Macrognathus pancalus
ygoid in Synbranchus is identical to that of (Percomorpha, Mastacembeloidei), with critical
Macrognathus (Britz 1996: fig. 5) or other remarks on—mastacembeloid inter- and intrare-
teleosts (see e.g., Arratia & Schultze 1991: lationships. American Museum Novitates
& 3181:1-18.
figs. 14, 15; Britz Johnson: figs. 4, 5) and &
G. D. Johnson. 2002. "Paradox Lost":
clearly demonstrates its homology with this S,keletal ontogeny ofIndostomusparadoxus and
bone. During subsequent development the its significance for the phylogenetic relation-
ectopterygoid of Synbranchus enlarges ships of—Indostomidae (Teleostei, Gasterostei-
greatly and bears numerous strong teeth. It formes). American Museum Novitates 3383:
1-43.
becomes the dominant element of the adult & M. Kottelat. 2003. Descriptive osteology of
,
synbranchid palatoquadrate (Fig. IC, see the family Chaudhuriidae (Teleostei, Synbran-
also Regan 1912:plate IX, fig. 1; Rastogi chiformes, Mastacembeloi—dei), with a discus-
1964:figs. 1-3; Rosen & Greenwood 1976: sion of its relationships. American Museum
figs. 60, 61; Gosline 1983:fig. 3B; Travers Novitates (in press).
Gosline, W. A. 1983. The relationships of the masta-
1984:fig. 10; Britz 1996:fig. 9C). Although —
cembelid and synbranchid fishes. Japanese
we have no developmental information on Journal of Ichthyology 29:323-328.
&
the pterygoid of other synbranchids, it is Johnson, G. D., C. Patterson. 1993. Percomorph
reasonable to assume that it also represents phylogeny: a —survey of acanthomorphs and a
new proposal. Bulletin of Marine Science 52:
the ectopterygoid, given its identical ap-
554-626.
pearance and position to the other bones of Lauder, G. V., & K. F. Liem. 1983. The evolution and
the hyopalatine arch. This homology falsi- int—errelationships of the actinopterygian fish-
fies Lauder & Liem's (1983) interpretation es. Bulletin of the Museum of Comparative
Zoology 150:95-197.
of this bone as the endopterygoid and thus
Liem, K. F. 1987. Functional design of the air venti-
invalidates one of their putative synapo-
lation—apparatus and overland excursions by tel-
morphies uniting the Synbranchidae and the eosts. Fieldiana 1379:1-29.
Channidae. The wider phylogenetic impli- Munshi, J. S. D., G. M. Hughes, P Gehr, & E. R.
cations of our finding are beyond the scope Weibel. 1989. Structure of the air-breathing or-
of this paper and will be discussed in a gans—of a swamp mud eel, Monopterus cu-
chia. Japanese Journal of Ichthyology 35:
forthcoming publication reevaluating the 453-465.
additional evidence for both hypotheses of Nelson, J. S. 1994. Fishes of the world. John Wiley &
synbranchid relationships. Sons, New York, 600 pp.
Rastogi, M. 1964. The head skeleton of Amphipnous
—
cuchia (Ham.). Acta Zoologica 46:283-292.
Acknowledgments
Regan, C. T. 1912. The anato—my and classification of
Financial support of RB by a 'visiting the synbranchoid eels. Annals and Magazine
of Natural History, series 8, 9:387-390.
scientist' fellowship of the Division of Rosen, D. E., & P. H. Greenwood. 1976. A fourth neo-
Fishes, National Museum of Natural His- tropical species of synbranchid eel and the phy-
tory, Smithsonian Institution, Washington log—eny and systematics of synbranchiform fish-
es. Bulletin of the American Museum of Nat-
D.C. is greatly acknowledged.
ural History 157:1-69.
Travers, R. 1984. A review of the Mastacembeloidei,
Literature Cited a suborder ofsynbranchif—orm teleost fishes. Part
II: Phylogenetic analysis. Bulletin of the Brit-
Arratia, G., & H.-P. Schultze. 199L Palatoquadrate and ish Museum of Natural History (Zoology) 47:
its ossifications: development and homology 83-150.