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<br />. :!7ti
<br />
<br />CALlFOH1\lA FlSH A1'iD GAME
<br />
<br />when (1) a continuous finfold is present, (2) there are pipment char-
<br />acters different from those of the juvenile, or (3) the fins are absent,
<br />unossified, or developcd to various degrees. It would serve no useful
<br />purpose to add another term. We therefore redefine the postlarva as
<br />the period after the, absorption of the yolk to a stage .,~hen. the fish
<br />resl'mbles the juvenile. 'fhe end of the postlarval conlhtlOr~ III many
<br />marine fishes may bc recognized by a striking transform.atlOn to the
<br />adult-lil.e form or, in most freshwater fishes, by the lo~s o~ most of the
<br />finfohls and the ossification of the rays of the pelVIC fin~. The two
<br />lattcr criteria charac:terize satisfactorily the suckers and mmnows and
<br />most egg laying North Ameril~an f"resh~v~ter. fishes, as nearly as we can
<br />detel'lllilH~, An eveIl wore prpl'ise dpfiIlltlOn IS that the postlarva corre-
<br />sponds to developmental stages ~8. to 40 (Balinsky, ~948; p. m~7-838.
<br />sllIlunarizcd below) in the Cyprlllldae and Catostolllldae, ] n tllls way
<br />all aeCllrate definition of the lal'val stages is estahlis\j('d, rl'hei'it~ stages
<br />probably do not dcviate 'greatly in most other families t~f freshwa~er
<br />fishes. 'fhe lIiodontidae, Corc'gonidae. Esocidae, Catostonudae, Cyprm-
<br />idae Pt'rcopsidae, Centrarchidae, Pcn:idae. Cottidac, and othe:rs ~ave
<br />a pl:stlan'al period. 'fhis is absent in the Salmonidae and AmelUrldae.
<br />~\]] gronps ll3ve the earlier prolarva, whieh corresponds to stages 27
<br />to :~2 (sPl' ht,low).
<br />'I'ht, distinetion of tbl' postlarval sta~e serves two purposes. From
<br />the s\'strmatic standpoint, it eharaeterizes a period wIlen most, if. not
<br />all, sjlecitic characters uscd for ide~;tificati~n ar~ at lea~t sup,er~clan.y
<br />diffrrent from thOSl' of the adult, F rom a functIOnal pomt of VIew, It
<br />is a ullique pl'l'iod when the rniNohahitat,. feedin~,. sensitivity to en-
<br />ViI'OII1l11'ntal t1uetulltions, amI other lwhavlOral tllfferellces are often
<br />quite ditfercut from those of the adult. ,
<br />\Ve have folltnwd the tl'rmillology :,tiven b~- Ralinsk~' (1948), WIth
<br />W'l'Y few modifications and additions. lIe divided the chromatophores
<br />int~ four horizontal series:
<br />1. The d01'sal pigmc1d linc. which consists of pigment rowS or scat-
<br />tel'ed pigment along the tlorsal edges of the llIyotomes and/or
<br />the dorsal integumentary pigmrnt. . '
<br />2, '1'he lateral pi{JlHcnt linc, which comprises the rows of plgment
<br />alon" the side. These are divisible into (a) pigment on the myo-
<br />mer;'" and (b) a single row of eells alon~ the horizontal m~o-
<br />septum. The latrral pigment line should not be eon fused WIth
<br />the lateral line (as was evidently done b~' .J<'ish (19a2)), a sense
<br />orcran that does not coincide with the horizontal myoseptum,
<br />3. '1'1~e 'V(:ntro-visceral In'{JlIIent line, which is internal, lying along
<br />the intestine.;t
<br />4. 'fhe 'unpaired llIidt'entral line, 'which may be internal, external, or l~
<br />both. ", ',.
<br />Additionally, we subdivide the dorsal head pigment into the occipital,t~
<br />the interorbital, the narial, and the upper lip pigment. ~ome of t~e;,',
<br />differences bctween Balinsky's usage and ours are explamed by hIS
<br />utilization of live, transparent material, whereas our specimen~ a~e ~
<br />preserved. 'fhe employment of .inte:nal ~har8:cters with live materIal,1I
<br />generally impractical for routme IdentJfi~atJon. ' ,
<br />Thirteen measurements taken on a senes of the postIarvae of eachi
<br />species failed to show diagn~stic differences within the Cyprinidae or'
<br />
<br />
<br />N A'rIVE POSTLARV AL FISHES
<br />
<br />~77
<br />
<br />Catostomillae. SOlUe features were found to separate the two families;
<br />the most reliable one was used in the key. (See also Table 1.)
<br />For each species over 100 specimens were aVll:ilable, except that oul~'
<br />17 of 1'iaro{Ja cobitis were secured. ]<'ew juvelllles of Catosto7llus Iah-
<br />pinnis were obtained, but a large eollection with all st~~es from t~e
<br />Green River, \Vyoming (U. M. M. Z. No. 92248), was utlllzed. We dId
<br />not collect postlarval stages of Ptychocheillls 11/cill,~, a species now rare
<br />in the lower Colorado River system,
<br />
<br />Developmental Stages
<br />
<br />Balinsky (19.J.H) ~a\'e a table of de,'elopmental sta~es for the Cyprin-
<br />idae that was modified from Oppenheimer's (El37) table for F'l/ "till-
<br />Ius heteroclitus (l~innaeus). Such an arrangement of diagnostic stages
<br />makes it possible to compare eorrespondin~ stages of different species.
<br />Comparisons bllsrd on the alternative eriteria of equal lengths and
<br />eqnal ages are usually unsatisfadory. Howe\'e~, it ~s useful to, know
<br />the lengths of the specimens and also whether sIze dlfferences eXIst be-
<br />tween species at equal developmental stages. Balinsky did not give the
<br />length of his fish or state whether the species were of different sizes
<br />at similar stages of development, Variations in the time of appearance
<br />of some of the larval characters of the species studied by us are shown
<br />in Table 1.
<br />It seems worthwhile to briefly summarize the cyprinid stages worked
<br />out by Balinsky, These define the limits of the postlarval period and
<br />eall attention to a useful method for future studies of the la.-val stages
<br />of North American fishes.
<br />
<br />Table of Normal Stage. of Deyelopment of Cypt',inld Fi,he.
<br />(Condew,ed from Balillsk~' (HH8 l )
<br />Stlll,(e 1. l'nfertilized egg.
<br />~tages 2-27. Den]opment of fertilized egg. HlItching <)('Curs lit about stage 27.
<br />Hlages 28-:12. ProluJ'\'1I1 stage with yolk sue.
<br />Ht.al,(c :'\3. Y Olli is ussimilated; 110 cauda I fin rays presl'nt.
<br />Htage 34. End of notochord suaight; caudal fin with 3-1 rll~-S; no trace of
<br />dorsal or unal fin.
<br />Ht.al,(" 3G. En<l of noloehord Ul)turlll'd; caudill fiu wilh 7-!l rll~'S; elevated fin
<br />IIIl'lIIhralH' at site of future dOI'sal and aual fins,
<br />Htal,(e 3G. Dorsal and anal w~tb rudimental'S, cartiluginoull rays; caudal fin
<br />1''''1I1<1ed, llI.arly cOlllplet.., with IG--17 ra~'s. .\ir Madder suhdividing.
<br />Ht.al,(c 37. Hays of dorsal and anal fins partl~' ossifi..d; cnudul emal'ginnte, with
<br />IH Ilrineipal r'Q's; rudiments of pelvics appear. .\ir bladder subdivided into two
<br />"arls.
<br />:';lag-e 3R. Pel\'ic fins in t.he form of crescentic fol<.ls,
<br />Hta/(e all, Pelvic tius ill tbe form of 1)lIddles, with uo trn('(' of rays,
<br />Hta/(c 40. p..lvie tins with t'udinJt'nt"r~', unossitiP<1 rll~'S,
<br />~tlll-:e 41. Pelvic rays purtly oH8ified. Coutinuous fiufold reduced.
<br />Htages 42-4G. Finfold l~st. scnles de\'eloJl. and Interlll-line cullnl forllls.
<br />
<br />'l'he embryo occupies stages 2 to 27, or to hatching if it occurs in
<br />some other stage. The prolarval or non feeding period is from stages 28
<br />to 82 and the postlarval or feeding larva is from stages 33 through 40.
<br />The five cyprinids we studied follow the above stages rather closely, and
<br />these stages can also be used as a basis of comparison for the Catos-
<br />tomidae. The first loop of the intestine in the suckers forms in stage
<br />:17, whereas the mouth descends to a normal ventral position between
<br />stages 39 and 40. In stage 37 some of the dorsal rays ossify before tbe
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