556 MARIYO F. WATANABF. ET AL.

Oi*hi, S. &• VVatanal>r, M. F. 1986. Acute toxuily of \SicrocyUifofTuginoM and it* cardiovascular effect*, tmiron. Kfs. 40:518-24.

Reynolds, C. S. 1973. Growih and buo>ancy <if ,\fifron.i/n ncru*girioitt Kut/ emend Klenkin in J shallow cutrophic lake. PTIH:Sof. Lend. B 184:29-50.

RrynoltlvC, S.Jawornki.J. M. H.. Cmicch, H. A.S: Leedale. G.F. 1981. On the annual cycle ofthe IjUic-nrrcn al^^ ,Vfirro-rMfti ofruginosa Kutz. rmrnd Elenkin. Phil, Tram. Royal. Soc.Lond. B 293:419-77.

Satnikarn. S,. Wiltiamn. D. H.. Smilh, R. J.. Hammond. S. J, &B«ilen. D. P.. ruinman. A., Wei%eli., P. L.. \'ilj<>en, C. C. &Kruger, H, 1983. A pariial Mructurr for ihe toxin BE-4from the blue-green alf;a Mtrrnr\\ti.\ afrughiota. J. Chrm. Sor.Chfm. Commun 652-4.

Schwimmer, D. &Schwimmer. M. 19(i8. Mcdital aspects olphy-coloKy tn JackHin, D, tEd.) Ateiif, Mfin und thr Environmrnt.Syracu%c Univer*ily Pre«. SyracuK", pp. 270-3r>8.

. S c o n , W . E , , B a r l o w . D . J . & H a u m a n . J . I I , 1 9 8 1 . S l u d i e * o nthe erolojfy. ^iiwih and phy*ir»l(»}{) of loxir Sticrocystw atru-

in Situth Alriti). / i Carmichaei. W, W, jF-d.) fhf Water

Eniironmfnt. .Mgal Toxins nnd Itfallh. Plenum Press, New York,pp. 49-69.

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/ Phycot. 22, 556-559 (1986)

NOTE

DESMID ZYGOTES IN EAST TEXAS'

Betsy B. Smilh$520 WindMjr, Nacogdochei, Texas 75961

ABSTRACTIn an extensive survey for desmids in 217 lakes and

ponds in 27 counties of east Texas, desmid zygotes wereinfrequently encountered. A list is given of zygotes of 22ipectes tn 9 genera. Two zygotes prei'iously unobsertrdare described and illustrated in photographs and cameralucida drawings.

Key index words: Chlomfthyta; desmids; sexual repro-duction; Zygnematales; zygotes

Reproduction in desmid genera is usually by asex-ual cett division followed by generation of new"semicelts" by eacb parent semicetl. Sexual repro-duction occurs infrequently in nature (West 1899,Smitti 1950, Kaltio 1953. Starr 1955. Coeset 1974a)and is possibty seasonal (Beijerinctt 1926. Smith1950).

Sexuat reproduction in tbis group of atgae isachieved by the process of conjugation. As describedby Smith (1950), mature celts form a common ge-tatinous sheath, align at right angtcs or paratlet. andbreak at the isthmus, allowing protoptasts to migratetoward each other. However, in the Mesotaeniaceae

Acffptfd: t-fjuty 1986.

and in certain filamentous Desmidiaceae, conjuga-tion tubes, within which protoplast.s migrate and join,grow from each cett.

The zygospores, or zygoies. formed by union ofprotoplasts from two cells (between cetts. in conju-gation tubes or, occasionalty. within one of the oldcetl walls), possess three cctt wait taycrs. The innerlayer is thin and colortcss and the outermost celtu-lose cell wati may be smooth or ornamented withspines, warts or bifurcated butbous processes and issometimes hetpful in species identification (Prescott1948). Prescott (1948) has suggested that moreprimitive genera possess smooth-walled /ygotes,whereas the more highty evolved ones conjugate tessfrequently and produce /ygotes with more elaborateornamentation. Sexual reproduction usually occursbetween futly mature cetts. although conjugation be-tween juvcnites has been reported in Micrasteriasangulosa, M. denticulala, Closterium ehrenbergii, C.moniliferum (Lipport 1967). and Penium didymocar-pum (Smith 1950).

The difficulty of obtaining sexually reproducing-cultures of desmids renders genetic research diffi-cutt (Kallio 1953. Brandom and Codward 1965).Zygospores are rarety foutid in nature and most des-mid cultures are steritc- (Brandom and Godward1965). Starr (1955). Cootc (1963). Biebel (1964). and

DESMID ZYGOTE.S 557

I. Dnmid sprdrs for which iygolrs wfrf found. Rrfrrrncr ismadr in pnrfnihfirs to othfr litfraturf sourcn in which information mayhf found about zygotft of iomr spfnes.

.S'ffriitm diptuf (Ehrenb.)ll/ig«>n & koihe(Ponhoff 1928, Cron-blad 1957. Biebel1964)

"iClostfrium calosftorumWittr(Kli (Prescott etal, 1975. PI. XXXVl,f.7)

C. roitatum Corda (Pres-cott et al, 1975, PI.XXXII)

C. kuftzinpi Breb. (Pres-a i t t r t i i l . 1975, PI.XXXI. f. 14)

C. roftratum F.hrcnb.(Kreiger 1937. PI. 33.r, 6-7)

C. strmlatum Ehrenb.(Prewott et al. 1975,PI. XXVM)

Kuailrum rrnsnum' (Breb.)U'lITi,fVtIllh

E. nvlutum (Nordst,)West & West

E. pitmatum' Ralfi

E. vrntricosum Lund.(Prescoti et al. 1977.PI. LXII, f. 7-12)

Xticrastrrias futiacfa Bailey"iCosmar^Hm omatum Ralfs

(Wesl& West 1908. PI.LXXVIIl. f. 9)

Cosmanum sp.Xanthidtum antiloparum

(Brcb.) Kut/.X armatum Breb. ex

RalfsArthrotifxmui sp.

}Stauraslrum nnatinumCooke & Wills

Staurastrvm dickifi Ralfs

S. furcigfrum Berb. (Prcs-ctitt, Biiudo & Vinyard1982, PI. S47,f. 8)

Dfimidium hailfyi (Ralfit)Nordsi,

D. caarctntum Nordst.(ScotI & Gronblad1957, PI, XXXVl. r.4-6)

D. su'artui Agardh (Raits1884, PI, IV. f. a-0

tll«llll)UII<>l1*

Jas|>er(April 1980)

Nacogdixhcs

Panola(April 1977)

Morris (April 1977),Hardin (March1975)

Jasper(June 1978)

Jasper (April 1980)

NacogdiKhes

Jasper(April 1980)

Jasper(April 1980)

Newton (June 1979)San Augustine

(August 1975)

NacogdochesNacogdoche*

Panola (April 1975)Jasper (April 1980)

Nacogdoche*(November 1975)

Jasper(April 1980)

Nacogdoches(October 1976)

'Tyler(January 1976)

Nacogdtxhes (April1978)

Jasper(April 1980)

Nacogdoches(March 1978)

T\f,inc dumrrrr*

90

56 X 42

U5

72 K 53

35 X 20

55

112

84"

76-85.'62.5-65"

87.5.'

3256.' 37"

9056

67.5

25.' IB-*

75.' 32.5"

83.' 55-'

57,' 34''

35-40 x22.5

40-50

20

• County in Texas and date of observation in parentheses,'' Diameter or range of diameters or dimensions in iim,* Zygotes of these sf>ecies not reported previously.• Wiihoul spines.' Wilh spines.

Ling and Tyter (1972) have presented methods forinducing conjugation in culture. Factors which ap-pear to aid in induction are the omission of nitrogenfrom the growth medium (Biebel 1964) and increas-

Etcs, 1 - 3 . Camera lucida drawings of dntnid vegetative cellsand 7ygoie. Vxc. 1, Eua.\trum ptnuatum vegetative cell, FtC. 2,Eua.\trum crasium vegetative cell. Fit;, 3. E. pinnatum zygote sur-rounded by setnirells. Bar - 20 fum-

ing COj concentration of the medium (Starr 1955).conditions which may be present at the shallow edgesof ponds with changing water levets.

Little has been published about factors involvedin the induction of conjugation in nature, althoughSmith (1950) stated that these factors are probablynot exctusively environmental. Coesel (1974a, b)proposed that it is low or absent sexuat potential,rather than environmental factors, which is respon-sible for the infrequent occurrence of sexual repro-duction in desmids in nature. That there are eco-togicat factors at work under natural conditions,wtNich influence the conjugation pnKess. was sup-ported by the observations of Homfetd (1929) andof Coesel (1974a) of sample sites which yietd zygo-spores of several concurrently conjugating species.

An extcnsi\-e desmid survey was made of 217 lakes and pondsin 27 rounticso! the Oak-Hickory-Pine EoreM \'egrtation Regionof east Texas (Smith 1980). Sample site* were randomly selectedto include as many types of standing water bodies as possible.

at Tsv li SMI HI

t inn| c ) ( ) ' . K i t . I ) , /•,

., 4, humltum I»v , 100 "-mo • . FM;. 7. *- 4(10

rc;. '>. /-, f'tiiii'ilin'i<>) l>;iis ^;ivcii m

nm mmrlcrs

t; M,l < ;it l i n t •ml ,il I M M H A< I r-\M()lf to<;iri'Mts l i \ ntt-.ili'>»>) J "V'l pt.nikl' i l i (irr Vl.ilcil.il Mr,i[»cfl f t i im rln- Mirl . i i r ol^iil)ti)(-r^r(l hiuh'-i .nfiiiilK piaiiiv and OTIK-I dh j i i i v vs.i Mlir-ii;nliir<l lo ihc s.uiipl'-\ I ivmn OI^.IMIMIIS wf tc rx . in i in id wtu-u

[liiwililr' ,IM<I .ill IVt'lf- pri-VfTM-fl lot l.lTcl lll<-|inlll.ltl>)TI 111 4 ?^liir«-r.ili lrti\(lr h i i l l c i t i l In | i l l (i I i l r i i l itic .ilions writ- m,i'lr pi >'iiiJiiilv Milli thr :iiil <)l K,ilt\ l IKIH), I Diisi i lnci l Tiiihiv '<> )>c l) '^M,iiliiiv; |HH(ii I'lr lilt- urmip, W C M ami \\<-si (I'.HM I'Jj, U'cvl rt

DESMID ZYCOTES 559

III. (1923). Smilh (1924). Imicf-Maric (1939). Krie-Kcr and Ger-li.n"(190'2-6<J).Jackson(l97I). I'rcscott cl al. (1972, 1975. 1976.1977). Many shorter and oftt-n more rccctil works were utilisedfor verification and for elucidation of new

The present study comprises the first comprehen-sive desmid survey in Texas or in its neighboringstates. Accordingly, the known ranges of all taxatherein were extended. The information in Smilh(1980) also identified some members of an impor-tant group of organisms in the ecologically distinc-tive area known as the Big Thicket. Confirmed wasthe premise that the acid waters of east Texas area highly suitable habitat for desmids. The elucida-tion of desmid species in this large part of Texaswill facilitate the conducting of ecological researchand encourage extension of survey data to otherparts of the state.

Ill the course of this study, few actively conjugat-ing species populations or desmid zygotes werefound. At one ofthe sample locations, zygosporesof six species were obtained. Zygotes positively iden-tified represent nine genera and twenty-two species(Table I). Two of the zygotes—those of Euastrumpinnatum and of £. crassum—have not been reportedpreviously.

The zygotes of Euastrum crassurti is spherical withnumerous short, bluntly rounded papillae evenlydistributed over the surface; that of E. pinuatum isalso spherical, bui with bluntly rounded spinous pro-jections. Both are similar to the zygotes of othermembers of the genus Eunatrum; consequently,drawings of the vegetative cells of both species arepresented in Figures I and 2, with drawings andphotographs of the zygotes in Figures 3-7.

Biebel. P. 1964. The sexual cycle of \ftrium digitus. Am. J. Bot.51:697-704.

Bcijf-rinck. W. 1926. Over versprcidinR en periudliiteit van de/octwatcrwicrcn in Drenlschc hcidcplasscn. V>r/i. Kon Sfd.Aknd. Wftfmch.. Afd. .S'afunrk.. Tuffiir Sfcf. 25:5-211. /M COC-wl, P. F. M. 1974. Notes on sexual reproduction in desmids.I, Zygospore formation in nature (with spcciul reference tosome unusual rrcords of zypoics). Acfa Bat. Xffrl. 23:361-8.

Brandom. P. K. & Codward. M. B. E. 1965. The inheritance ofmatitiR type in desmids. Xnf Pbytol. 64:428-35.

Coesel. P. F, NI. 1974a, Noteson sexual reproduction in desmids.1. ZygosfMire formation in nature (with s xxrial reference tosome unusual records of zvRoles). Acta Bot. Xffrl. 23:361-8.

• 1974b. Noie on sexual repnxluction in desmids. II. Ex-|>rriences with conjugation experiments in uni-algal cultures..ictn Bot. Xffft. 23:603-11.

CtKtk. P. W, 1963. Variaiion in vegetalive and sexual morphol-ogy among the small curved sjjecies of C/tw/*Tmm. Ph\colopa3; i - l8 .

Gronhlad, R. 1957. Obser\'ations on the conjugation in Xrtriumdigitui. Bot. Xot. |IO;468-72.

Homfeld. H. 1929. Beitrag /ur Kenntnis der DesmidiacrenNordwestdcuischlands, besondere ihrer Zygoten. PJfanzm-

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Ircnce-Marie. Fr, 1939. Ftorr Drsmtdialrsdf la Rrgtondf Montreal.La Prairie, Canada. 347 pp.

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Prestott. C. W. 1948. Desmids. Bo(. Wn-, 14:644-76.Prescott, C.\V..CnMsdale.H,&:Vinyard.\V.C. 1972. Desmid-

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1975. A Synopsis oJ Xorih Amrnfatt Drsmidf.. Part II. Dfi-midincfaf: Placodfnnaf Sfft. 2. L'niversity of Nebraska Press.Lincoln. 413 pp.

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1977, A SynopM.\ of Xorth Amrnrati Dftmtd.\. Part tt. Dn-mtdtacfar: Placodrrmaf Srct. 4. L'nivemity of Nebraska Press.Lincoln. 700 pp,

Ralfs. J, 1848. Thf British Dnmidifat. Reeve, Bcnham. and Reeve,London. 226 pp,

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