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The protractile apparatus of the mouth of the catastomid fishes.

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THE PROTRACTILE APPARATUS O F THE ALOUTH
O F THE: CATBSTORIID FISHES
S I X FIGURER
INTRODrCTION
The famil>- (’atastomitlac (suckers) is among the bestknown and most easily recognized of the fresh-water fishes.
They are cliara(~terizeC111)- the prcsence of a protractile mouth,
fieshp, sucker-like lips, aiid toothless jaws, tlie mouth being
protrusible to a greater extent tliaii iii other fishes.
‘I’hey are bottom feeders, liviiig chiefly upon vegetation,
smaller Nollusea, Entomostraca, worms, larvae of aquatic
iiisects, eggs of various kinds, aiid mud, wliicli they doubtless
ingest f o r the organic matter it coiitaiiis. 111 tlie act of fcccling, the mouth is drawn tlownward aiitl foi-w\-artl from the
uiiderside of tlie head like a spout. Food is taken into the
mouth by sucticm, t o 11-hiclitlieiy protractile months a i d fleshy
lips a r e peculiarly adapted. According t o Konleiigcr ( ’04),
“tlic sliape, size and character of the mouth aiitl jaws, tlie
extciit t o which they can protrude and retract largely depend
upon cliffcrciices of liabit and f oocl. ’ ’
A review of tlic literature has rerealed iiotliiiig relative to
the details of the modus opcraiidi of the protrusible mouth
of tlic Catastomithe beyolid what is geiicrally recognized for
fishes with protractile premaxillaries.
At the suggestion of T’rof. Raymond C. Oshrii, tlie writer
niidertook a study of the anatomy of the jaws and methods
of feeding of tlie Catastomiclae in order t o determine the
factors irivolved in the chai-acteristic protrusion of the mouth.
2.57
T H E 4N41’031IC1L
ItICOlll), \ O L
,$$,
NO
4
M A T EIZI41, A XI) i
V ET 11 0 1 IS
The piwblem was attacked with the idea iri miiicl of finding
0 1 -arrnitgcmetit of miisclcs or hoiics which
liatl lwcome modified to hriiig about the characteristic moremcnts of the mouth. Three methods were employed-that of
tlissectiori, tlie preparation of longitudinal aiid cross-sectioiis
of tlic lil)s for microscopic cxamiiiatioii, a i d tliat of electrical
stimiilatiori. In ortlei* to make comparisons with tlie skeletal
t>lcments aiitl jam mixsculatiire of teleosts in general, tlie
skiills of a iiuml)er of species in other families were dissected.
r 1
1 I i c i i , iii view of maltiiig closer comparisons, the skulls of
t l i ~ c a i y (C'ypi-iiiiis mrpio, Liiiiiaeus) aiid a millno\\( ('ampostoma anomalum, Rnfinesqixe) ~vei'e dissected, llotli
of wliicli have sucking mouths, lint less modified.
h i studying the mec*lt;inism of tlic protrusion of the mouth,
tlie licatls of the following species of suckers were dissected :
t l i c cwmmoii snclrer (('atostomiis commersoiiii, Lac6pktle) , the
Iiogsuckci~ (C"atostomus nigricans, L e Suenu), tlie c o m m ~ i t
i~vl-liorse( \loxostoma aureolum, T,e Snenr), the white-nosed
silc~kcr ( Nosostoma aiiisuriim, Itafiiiesquc), the spottetl
siicltei. (hliiiytiwna mclaiiops, Xafinesqne) and the clinhS I I C ~ ~ I( .bhimyzon siicetta obloiigiis, Rlitchill).
The general
: ~ i ~ i i i g e m ct ~ofi i tlic bites arid muscles was tlie same througltont except in miiior tlctails, a s will l w scc~iiin tlic follo~viiig
t liscnssion.
home special set
AS .I
TO bl Y O F 1'11 E J A 1VS
rl'llc mterior margin of thc uppc.1- jaw is formecl 1))- the
1)1~cmnsillary( I ' M . , figs. 1 to 5), which terminates a h v e in a
iiasal process o r premaxillary spine ( F ' w . ~ . ) .
In most
t eleosts this process pro.jects hackwai~lalmost a t riglit ;mgIc~s
to tltci rest of tlic h i i e into a groove oii the etlimoicl ( E t h . ) ,
t hiis allowiiig a forwaid gliding motioit. However, iri the
('wtastomidae the premasillary spiiie, iiisteacl of gliding 011 the
~ t l i m o i d is
, attached to the preetlimoid or rostra1 process ( I > ( , . ,
figs. 2 aii(1 3 ) 1 3 ~ 7 means of an elastic ligameiit (Li.q.1).
Fnrtlicrmore, the spine is flesiblr, so tliat, wlieii the j a ~ wa r e
PROTRACTILE APPARATUS O F T H E N O U T H
0
>
I
J
E
259
rcti*actccl, it is beiit clownvvartl almost t o a vertical positioii
the ligameiit is lax (fig. 2). l)uring protraction, howcl\-cr, it assumes ail almost liorizontal position (fig. 3). T l i ~
ligi1melit permits the fi-ec protrusion of the 1)remaxillar.y to
tlie full extent of its length. 111 tlie various species of siickers
wilt1
tlie montli is protrusiblc t o varying degrees, correspoiitliiig
to tlic length of the spine as well as the ligament coiiiiecting
it to the cmiiium. Tlie premaxillary is not attached to the
i d a t i n e s , as is true of most Telcostei, and tliiis allo\vs for
g - e a t e r freedom of movement of tlie upper jaw.
The premaxillary is attached below by meaiis of a tencliitous ligament (Lig.2) to tlie ventral tip of the maxillary
(LWux.). The maxillary is a flattened hone lying laterally and
slightly posteriorly t o the premaxillarj-. The dorsal eiids of
the maxillary meet and form a groove in whicli the premaxillary spine glides. A posterior coiidylc at this end of
tlie maxillary is inserted into a cartilaginous rod ( P.Y.,
figs.
2 and 3) which connects the maxillary witli the romer ( TTo.).
Tliis rod is well developed i i t tlie ('atastomidae a i d affords
b'ig. 3 Lateral \ i e w of tlie jaws, with stliiie parts rcinorril as in figure 2 ,
sliowmg the position of thc ~~reiriaxillarp
and rclatcd parts in protraction. Thtprciiiaxi1l:iry spine a m l ligament 1 assume a n almost horizontal position.
a more or less movable joint. The maxillary is also attached
to the palatiiies by meaiis of a ligament, and its ventral tip
is coiiriected with the mandible in a similar manner. This
coiiiiectioii is a t the angle of the mouth, and, as will be esplaiiied later, serves to pull the upper jaw d o m i v w d and
forward when the mandible is depressed.
The palatiiic (PaZ.) js a triangular (iiiequilateral) bone
which flanks the vomer on either side. I n the perch, which
may be considered a commoii representative of the Teleostei,
a n anterior process of the palatine projects forward to
articulate with a coiicavity in the maxillary. Hoa ever, as
iiitlicatecl ahove, tlicre is 1 1 0 direct coiiiiectiori n i t h the maxill a r y esccyit hy meaiis of a ligament, thus allowing more
fiwtlom of movemcwt of the upper jaw.
‘l’lie posterior hordci. of tlic palatilie artionlates x ith the
mcscry)tcrv~:oid(Jfs.gtg., fig. 1) and its outer angle with the
ptcrygoitl ( P f g . ) . TATiiig heliintl the former aiicl articulating
with it, is the metaptcrygoid (J1t.ptk9.), and l ~ e l o wthe latter
is tlic ciuatlrate ( Q d . ) , which in t i u ~ articulates
i
with the lowcr
j?I\\-
.
The upper jaw liws 110 coiiiiectioii with the cwiiiium cJsce1)t
:iiiteriorly where tlic palatilie abuts agaiiist tlie vomer. . i n
at tnclimewt is partly effected posteriorly by meaiis of n s t i s ~~hiisorinm
formed hy two boiics-the 11)-omaiidibular ( H i / / ) . )
;tii(l symplcctic ( N y n , . ) .
Tlie liyomanclibular articu1;itcs t l o 1 . sally with the pterotic ( P t r . ) a i i d spiieiiotic ( S p . ) a i i t l is
joined vciiti*nlly hy ti c.artilnginous bar. with the symplectic.,
which i i i t n n i fits iiito a groove i n the qnaclratc aiid melri1)tcIrygoitl.
’l’lic lo\vei* jan. oi’ rnaiiclible cwiisists of two mmi, riglit >uid
loft, joiiietl iii fiwiit 1 ) a~ movahle symphysis. ‘l’lie anterior
Iwrtlcr of the maiic1il)lc is formed 1)y the toothless tlciitai*y
( I l i t . ) . 13eliiiitl this is tlie articulai’ ( A r t . ) , at tlic lo.\\-c.r aiiglc
i ) f nliic*Ii is tlic small ;uigalai. (A/t<q.). ‘l’he ai-ticular has ;I
decyly (wiicave sui*facc iit its Itostcrior extremity f o r articulatioil with tlie quaclrritc. Tlic latter thus serves as ;t I)e(liclc
For the nttaclimeiit of tlie lowci*j a w and enables it to caomliiiir.
its moremetits witli those of the upper jaw. ,4s O\veii (’66)
))oilits out, “the npper atid lon-el. jaws are st) eoi~icc.tec1in
)sscwm Fishes tliut oiic c~~iiiiot
be moved witiiont aff’wtiiig
the other and both tire alike movahle. J’rotrusioti a i d r e t n c t i i ) i i affect them equally.”
I lie sliapc of t h c mmitlihle is peculiar, especially as compared with siicli tcleosts as tlic perch. 111 the latter tlic
rriaiitlil)lc esteiicls Iiorizoiitally forward from its pcdicle,
\\,litlrens in tlie (’atastomidae it exteiids horizontally forward
t o tlic a~ig~ilnr.
where it turns almost at riglit aiigles tct pass
r 7
PROTRACTILE APPARATUS O F T H E MOUTH
263
a
id
Y
da$
f y
,
a
Fig. 5 Lateral view of the heacl, showing the deep musculature of the jaws with the cut ends of addurtor
rnnndibulae 1 and 2. Adm.3, adductor mandibulae 3 ; L.u.~.,levator arcus palatini ; Ph., protractor hyomandibular.
,dm.2.
-Adm.l
PROTRACTILE BI’L’AHATUS
O F THE MOUTH
265
vertically upward, eiidiiig in the overliangiiig dentary. This
type of maridible thus permits greater movemciit of the jaws
aiid subsequently more proiiouiiccd protrusion, as will be
explained later.
Fig. 6 Ventral yirw of the head, showing the inusculaturc of t h e n~and1bleand
liyoid region. G l i . , geniohyoideus; Itii., intcriiiantlihularis; Sh., stcrnohyoideus ;
Sy., s>-mpliysisof the mandible.
The muscles either directly or indirectly concerned in the
protrusion of the mouth arc the geniohyoideus, sternohyoidcus, and protractor hyomandibularis (figs. 4 to 6).
The geniohyoideus (GJi.) is a paired muscle lying on the
ventral side of the licatl. It arises on the ceratoliyal, each
266
LINDEN P.
EDWAHnS
muscle exteiidiiig obliqnely forward to meet its fellow of the
opposite side. These, in tnrn, continue for~7\rard,passing
i i h w e the iiit.ermandibula.ris t:o their insertion on the t.ip of
the mandible near the symphysis. The contractioii of this
~
by depressing the mandible.
miiscle opens t . 1 mouth
111 it.s act.ioii a.s a depressor of the ma.ndible the genioliyoid~.'iisis assisi.eii hy tEic st,eriiohyoideus (A'?(.), which is tlie
maiii rct.ract.or of t.he hyoid. This is a paired muscle 1ia.ving
it H origin on t.he pec4ot-d girdle, from which it extends hackwai;d i l s the vent.ral abdominal muscles. The fibers of this
m i d o exteutl forwa.rd longitudinally, to be iiiserted above
t 1 1 ~ 1geniohyoi.dcus on t.lw basihyal. By t,he contraction of this
miiscila thc liyoid is drawn downward and bac.k\vard. This
motioii is, in turn, tra.nsferred to t,he ma.ndiblc thmugli
t I i c acrt.iori (Jf the geiiiohyoideus, which accelerates and
i I i c I'C*R s(:s it,.
When t.he mandible is depressed the premasil1ai.y i s c h ~ ~ \ v i i
i.Iowiwml and forwa.rd because of the tension on tlie ligainelit cwnnecting the upper a i d lower jaws a t the angle of the
mouth. 'lY1e protrusion of the jaws is facilitakl by the following factors : First, t,Eie general looseness of the attachmelit of the premauiIla.ry to the ethmoid (ligament 1.) \diich,
as previons1-y expla.iiietl, allows grca.t. freedom of mcircmen t.
S.itrcondly,the peculiar charac?t.erof the mandible which permits
i i more proiiounced prot.rusion. Thircll?-, thc action of the
'1 )1*0tractor ~ i ~ ~ ) m a ~ ~ ~ l (iPlk ~
r .,i figs.
i I a r4i and
~ 5) which aids in
t1irrist.in.g forward 1)ot.h t.he upper a.nd lower jaws. This
muscle arises 011 t.hc sphcnotic. and is iriserted on the outer
.fac!c of tlic liyomandilniilar. M7h.en it. contracts it teiicls to
t '1~ 'IT
a tlic ]Iy omaritlihiilar 0-tit,u7ard ai id forwa r d , wlii ch , in
trirn, thrusts for.c\.ard t.he izppcr mid lower jaws. 'I!liis occurs
t)wwiiscL the Iiyomantlibnlar serves as thc suspeiisorium for
1:)ot.h the npper aiid lower ,ji1~7s,as has 1:)eeii prerionsly
iq)laincil.
Tlic muscle which retraots the jaws 1):- closing the mouth
is tlie ndduct.or mantlibulae (-4dm., figs. 4 and 5). This musvlc lies on either sick of tlie head and is differentiated ii1t.o
three fasciculi. In tlie perch, according t o Oweii ( ’66), it
arises “from the tympanic petlicle ant3 anterior border of
the preoperculum, and is inserted by the upper fasciculus into
the maxillary; by a lower faseiculus into the mandible beliiiid
tlic coronoitl process ; and by an aponeumsis into the mem1)aiie uniting the two jaws iiear the angle of the mouth.”
I11 the Catastomidae the above description of the iiisertioii
of this muscle does not hold true. Adductor 1 (Atlin.1) arises
from the anterior border of the preopercular, aiicl, ext endiiip
horizoiitallp forward, is inserted upon the outer face of the
maxillary; adductor 2 ( A d i n . 2 ) ,lying anterior and ventral t o
atlductor I, arises 011 the preopcrcnlar and mandible and,
lmssing npward aiid forward, is inserted upon the masillary,
its teiidoii overlapping diagonally that of adductor 1; adductor
J), which is covered by tlie preceding fasciculi, arises
from the quadrate and metapterygoid regions, its fibers exteiiclirig forward to be inserted by a crescent-shaped tendon
iil)on the mandible near the angle of the mouth. The action
of adductor 1 is to retract the upper jaw by drawing the
maxillary posteriorly. This, in turn, retracts tllc prcmasillary, for, its previously clescrihed, the ventral tip of tlie premaxillary is attached to the ventral tip of tlie maxillaq- hy
rneaiis of a ligament. Arlclixctor 3 assists in retracting the
jaws hy pulling the angle of the mouth post eriorly, d i e r e a s
adductor 2 closes the mouth.
As previously stated, food is talicii into tlic moutli bj- suction. This is brought about h ) ~the alternate enlargement
and coiistrictioii of the oral cavity. Thc oral ( ~ a ~ i tih
> -enlarged by expanding its walls laterally arid hy (tpeniiig the
month. The muscles involved in this a r e the protractor hpomandihularis, geiiiohyoidcus, sternoliyoideus, and the lei-ator
arcus palatiiii. A s already explained, the protractor lipomandibularis pulls the Iiyomanclibiilar f orward ;iad ontivartl,
tlius eiilarging the cavity. Likewisc, the geniohyoideus and
sternohyoicleus have been described as the depressors of the
mandible, tlius opening the moutli. Tlic l e ~ a t o arcus
r
pala tini
( L a p . , fig. 5) exteiicis outn.ard across the floor of the or1)it.
268
LIKDER F. EDWAlIDS
A\iisiiig011 tlie pnrasplicrioid (Z’s.), the fibers pass laterally
to he iiisertctl upon the outer face of tlic mesoptei*ygoid aiicl
~nctwpter~-goicl.The actioii of this muscle is to elevate tlie
palatinc~rtyioii, thus assistiiig in tlie dilation of the oral
cavit?.
rt’litb01x1csarity is cwiistrictvd by tlic lateral cwiitrartioii of’
its \mils arid by thcl closing of tlie month. This is hronght
a h i t 1)y the coiitractiou of the adductor hyomwndibularis,
i I i t P ram a lit1 ibn 1a r i s , a lid t 11 e a tldu c t o 1‘ ma iicl i b nl a e . X s a 1re ad y
( lc sc 1.i he (1, 1lie a tlcluct o r ma 11tli ba la e closes t lie mo 11t 11.
T1I c
acltliictoi- lryom~iic~ihularis,
wliich lies on the iiiterior of tlie
sknll, takcs its origin from the parasplienoid ant1 primtic. It
ostencli. Iatcrnlly f r o m its origiii to he inscited upon tlie iiiiiri.
fwc*c~of the h!-omaiitlibul~~r. A s the name implies, its actioii i h
t o atltluct the Ii;r-omaiitlibular, thus decreasing the sizcl of the
ot’a1 cavity. T l i ~iiitcrmaiiclil)ularis (1117., fig. 6) is a i i 1111p a i w t l muscle lying 011 tlic ventral side of the licad. I t ])asst’s
t ~.;iiisvcmelyfrom oiie i’ami~sof the mandihle to tlic othei.,
t(lii(1iiiq to draw t1ic.m togetlicr after they 11avci 1)c~cit
cl i r a 1-ic’a t ed.
15 S 1’E It1R3 E N T A 1, I N V EST I(; A T 1 0 s
111 order to clemoiistrate that these muscles are iiir.ol\-cd i i i
tlicn olwiiiiig aiicl closing of the jaws aiid the coiisequeiit prot rxctioii niitl rcitractioii of tlic pi*emaxillarj-, live fish i ~ t x i
stimulated 1)y means of the current from iiii iiiductioii coil.
1 1
lhcb stimnlus w:is applied first to the siicltcr-like lips, hot11
IwforcL aiicl after severiiig the trigemiiial iierve. So appai’eiit
~ ) r o t r ~ i ~ sof
i o rthe
i month resulted. ‘I’his tciidecl t o tlemoiisti.;itc~
that iio muscle fibers were Imseiit in the l i p to aid iii tlie
charactcristic protrnsioii of the mouth. Upon stimulatiiig tlicb
geiiioliyoitlens and sterirohyoidcus, the prcmaxillai*>- was
thrust d o \ ~ i i \ ~ \ - aaiid
~ * t lfor\vi11”d. 011 tlie other hand, \~liciltlic
acltlnctor maiidihnlac was stimulated the jaws were retractetl.
~
PROTBACTILE APPARATUS O F T H E MOUTH
269
HISTOLOGICAL INVESTIGATION
Sections were made of tlie lips of the various species of
suckers, to determine if any muscle fibers could be detected
ancl which would be likely to aid in their characteristic moremcnts. Botli longitudinal aiid cross-sectioiis were prepared,
some of which were stained mith Delafield's hematosylin and
counterstained with eosiii, mliile others were treated with Van
Giesen's stain. The latter is ail excelleiit cliffereiitial stain,
rcvealiiig the presence of muscle fibers, etc. Hou-cver, no
muscle tissue could he detected by this method.
COKCLTTSIONS
It is evident, therefore, that protrusion of the mouth in the
Catastomidae is broiiglit about by tlie same movements, vhich
serve in other fishes to ope11 the jaws. The lnoiies arc. anatomically identical, hit. differ morphologically, nliile the miiscles differ but little except in attachment. The protrusion is,
therefore, effected by the pulling do\vii\varcl atid forward of
the prclmaxillai-y wlicn the maitdihle is clepressed.
SUMMARY
1. The premaxillary spiiie of the Catastomidae is clistinctive in that it is attached to the preethmoicl by mcaiis of a lax
ligament.
2. There is 110 ligament attaching the pi.emaxillary to the
palatine, thus wllowing more f recdom of morement.
3. The maxillary is not articulated with thc palatine R S is
true of most Teleostei.
4. A cartilaginous rod coniiects the maxillary with the
vomer, t h i s affording a more or less movable joint.
,j.The mandible is peculiarly modified and permits greater
protrnsion of the mouth.
6. The adcluctor mandibulae is peculiarly adapted to the
type of jaws.
7. The protrusion of the premaxillary is brought about by
the lowering and subsequent protraction of the mandible
which increases the tension on the ligament connecting the
lower and upper ja\t's a t the angle of the mouth.
270
LINDEN F. EDWARDS
8. Stimulating the muscles involved in the opening and
closing of the jaws verified the above results.
9. Stained preparations of the lips failed to reveal the presence of muscle fibers in them.
BIBLIOGRAPHY
ADAXIS, L. A. 1919 A memoir on the phylogeny of the jaw muscles in recent
and fossil vertebrates. Annals N. Y. Academy of Science, vol. 28.
ALLIS, E. P. 1897 The cranial muscles and cranial and first spinal nerves in
Amia calva. Jour. Morph., 1701. 12.
BOULENGER,
G. A. 1904 Fishes. Cambridge Natural History, vol. 12.
BRIDGE,T. W. 1904 Fishes. Cambridge Natural History, vol. 12.
FORBES,
S. A., AND RICHARDSON,
R. E. 1908 The fishes of Illinois. Natural
History Survey of Illinois, vol. 3.
GUNTHER1880 Introduction to the study of fishes.
JORDAN,
DAVIDSTARR 1904 Guide to the study of 'fishes.
JORDAN, I). S., AND EVERMAN,
B. W. 1916 American food and game fishes,
vol. 8.
OSBURN,R. C. 1901 Fishes of Ohio.
OWEN,RICIIARD 1866 Anatomy of vertebrates, vol. 1.
PARKER,
T. J., AND BETTANY,
G. T. 1877 The morphology of the skull.
PARKER,
T. J., AND HASWELL,
W. A. 1910 Textbook of Zoology, vol. 2.
SAGEMEIIL1891 Beitrage zur vergleichenden Anatomie der Fische. Morph.
Jahr., Bd. 17.
TEUTLEBEN,
E. VON 1874 Ueber Kaumuskeln und Kaumechanismus bei den Wirbelthieren. Archiv. fur Natur.
VETTER,B. 1874 Untersuchungen zur vergleichenden Anatomie der Kiemen und
Kiefermusculature der Fische. Jena Zeits. fur Natur.
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