New and interesting Gomphonema (Bacillariophyceae) species from East Africa

14 Pages·1991·4.9 MB·English

by  John Patrick Kociolek

Marine Biological Laboratory
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CALIFORNIA ACADEMY O ',
Vol. 47, No. 9, pp. 275-288, 59 figs. December 10, 1991
NEW AND INTERESTING GOMPHONEMA
(BACILLARIOPHYCEAE) SPECIES
FROM EAST AFRICA
By
John P. Kociolek
DepartmentofInvertebrateZoologyandGeology, CaliforniaAcademyofSciences,
GoldenGatePark,SanFrancisco, California94118
and
Eugene F. Stoermer
CenterforGreatLakesandAquaticSciences, UniversityofMichigan,
2200BonisteelBoulevard,AnnArbor,Michigan48109
Abstract: ThetaxonomyandultrastructureoffiveGomphonemaEhrenb.speciesfromEastAfrica,including
twodescribedasnew,arepresented.UltrastructureofEastAfricanspeciesiscomparedwithcongenersand
showntodifferinseveralaspects.GomphonemaafricanumWest,G.aequatorialeHust.,G.kilhamiisp.nov.,
andG.paddockiisp.nov.areendemictotheregionandappeartobecloselyrelatedbyvirtueoftheunusual
structureoftheirstigmataandlackofpunctaocclusions.ThesespeciesofGomphonemamayalsobeclosely
allied to Gomphocymbellabeccari(Grun.)Forti, which hasasimilar, elongatestigma. Gomphonemaclevei
Fricke, which also appears to be endemic to East Africa, resembles Reimeria sinuata(Greg.) Kociolek &
Stoermerwithregardtostigmamorphology.Thesystematicpositionofthisputativegroupisunclear.
ReceivedJanuary10, 1991.AcceptedMarch20, 1991.
Introduction
Despite the attention East African Gompho-
Alarge body ofinformation on diatoms from nema species have received, questions remain
East Africa has accumulated over the last cen- regardingcircumscriptionoftaxa.Reportsonthe
tury, includingthe worksofFricke (1902), Miil- morphologyanddistributionofG. cleveiFricke,
ler (1905), West (1907), Hustedt (1949), Chol- forexample, vary greatly (compare Fricke 1902
noky(1954), Kufferath(1956), Monteira(1963), withKrammerand Lange-Bertalot 1986). Valve
and Gasse (1986). These important floristic ultrastructure ofmost East African Gomphone-
works, and others (see Ross 1983; Gasse 1986 ma species is unknown; the only published ob-
for extensive bibliographies) indicate Gompho- servationsarethoseofGasse(1980)foradiatom
nema Ehrenb. species are an important com- identified as G. africanum West. Additionally,
ponentofthe region'sdiatom flora. Ross (1983) corematerialwehaveinspectedfromLakeTan-
hasnotedGomphonemaspeciesoftheregionare ganyika contains specimens that appear to be
unique and has listed five species he considers new to science.
endemics. In this report we consider the taxonomy and
[275]
276 PROCEEDINGSOFTHECALIFORNIAACADEMYOFSCIENCES,Vol. 47, No. 9
ultrastructureoffive Gomphonemaspeciesfrom
East Africa.
Materials and Methods
Observations were made on material from
several sources. Cleaned material from cores
taken from Lake Tanganyika was supplied to us
by John Kingston (Queen's University). The
originalsourceofthismaterialwasTomJohnson
(Duke University). Samples from Lake Rudolf
weretakenbyRobertRoss(TheNaturalHistory
Museum, London), and material utilized in this
BM
studyincludes 1367, 1368, 1370, 1371, 1396,
1397, and 1398. This material, as well as the
holotype slide for G. africanum from Lake Tan-
ganyika,waskindlyprovidedbyDavidWilliams
ofThe Natural History Museum, London.
Material from these sources was boiled in ni-
tric acid and alternately rinsed and settled in
distilledwatertoremoveoxidationby-products.
Cleanedmaterialwasair-driedontocoverglass-
esandmountedontomicroscopeslideswithHy-
rax® Lightmicroscopicobservationsweremade
.
withReichartPolyvar,OlympusOH-2,andLeitz
Ortholuxmicroscopes.Forscanningelectronmi- 1
croscopy (SEM), cover glasses containing air- Figures 1-3. Gomphonema africanum. "clavate" type.
dried material were mounted onto aluminum Figure 1. Specimen from holotype slide, BM 78079, "Tan-
stubs and coated with approximately 20 nm of ganyika26-viii-'04,Cunnington79."Figures2,3.Specimens
gold-palladium. Material was viewed on JEOL from LakeTanganyika,core,station 10, 100cm.Scalebar=
10Mm.
T-lOO and Hitachi H-520 SEMs.
wideraroundcentralarea.Striaedistinctlypunc-
Results
tate and uniseriate. Striae radiate along most of
Gomphonema Ehrenberg 1832 lengthofvalve,stronglyradiateatfootpole. Stri-
Gomphonema africanum West ae8-12/1 ^lmandconsistentlyfineratfootpole.
Smallseptumandpseudoseptumpresentateach
(Figs. 1-21,26)
pole.
Valves 70-230 /um long, 14-25 nm wide, and In the SEM, external stigmal openings oblong
highly variable in outline. A number ofdistinct relativetoroundedpuncta(Figs. 14, 15). Puncta
morphologiescanbeidentified.Onegroup,which unoccluded, but this may be caused by preser-
includesspecimens fromthe holotype slide(BM vation problems on the subfossil specimens,
78079), is strongly clavate, broadest near the which show other signs of valve degredation/
headpole, and has "turris"-like/apiculate head- dissolution (Fig. 16). External proximal raphe
poles (Figs. 1-6). A second group (Figs. 7-9) is ends terminate close to one another (Fig. 15).
lanceolate-clavate and broadest at the center of Internally, central nodule bears recurved proxi-
thevalve,whileathirdgroupislinear-lanceolate mal raphe ends (Figs. 17, 18). Central nodule
(Figs. 10-13).Aprominentapicalporefield(APF) eccentric to raphe slit and stigmata project
positionedatfootpoleandonelargespinevisible obliquelyfrom nearpunctaonto it (Figs. 20,21,
atheadpole(Fig. 11). Raphelateralandstraight. 26). Pseudosepla visible at poles (Figs. 17, 19),
One to several stigmata have external openings and marginal lamina runs length ofvalve (Figs.
nearpuncta, makingthem somewhat difficultto 18, 26).
observe. Axial area narrow, becoming slightly Comments.—These observations on general
KOCIOLEKANDSTOERMER: GOMPHONEMA FROMEASTAFRICA 277
Figures7-9. Gomphonemaafricanum,"lanceolate"type,
specimens from Lake Tanganyika, core, station 10, 100 cm.
Figures 4-6. Gomphonema africanum, "clavate" type, Scalebar= 1 iim.
specimens from Lake Tanganyika, core, station 10, 100 cm.
Scalebar= 10nm. TypeLocality.—Lake Tanganyika, core, sta-
tion 10, 100 cm.
valve morphology agree well with the original In the SEM, puncta appear dash-like or nar-
descriptionofWest(1907)and Hustedt's(1949) rowlytear-dropshaped(Figs. 27, 29, 30). Exter-
detailed treatment. The size range reported here nal proximal raphe ends dilated and stigmal
iswiderthanpreviouslyrecognized. Formaltax-
onomicrecognitionofthedifferentmorphologies
describedhereawaitsadditionalobservationson
shape variability, particularly of larger speci-
mens.
Foged's(1966)illustrationsofthisspeciesfrom
Ghana are more reminiscent ofG. gracilis var.
turris Hust. than G. africanum.
Gomphonema kilhamii, Kociolek & Stoermer,
sp. nov.
(Figs. 22-25,27-31)
—
Description. Valves trullate in outline, 70-
180 MHi long, 12-21 )um broad, headpole acute,
footpole rounded and broader than headpole.
Striaeparallel-radiate,distinctlypunctate, 9-10/
1 MHiatmid-valve, 11-13/10/umatpoles.Axial
area straight, narrow, and contains laterally ex-
panded raphe. Isolated stigma conspicuous, lo-
catedclosetostriae.Internalproximalrapheends
distinct. Small pseudoseptum present at each
pole.
—
HoLOTYPE. Light microscopic preparation
216039, CAS—(Fig. 23). Figures 10-13. Gomphonema africanum, "linear" type,
IsoTYPES. Light microscopic preparations, specimens from Lake Tanganyika, core, station 10, 100 cm.
ANSP and BM. Scalebar= 10/urn.
PROCEEDINGSOFTHECALIFORNIAACADEMYOFSCIENCES,Vol.47,No. 9
278
KOCIOLEKANDSTOERMER: GOMPHONEMAFHOMEASTAFRICA 279
Opening irregular and larger than puncta (Fig.
30).APFbisectedbydistalrapheend,producing
different-sized lobes ofAPF. Porelli round and
extendaroundrapheendalongmantle(Fig. 29).
At headpole, puncta slit-like and raphe curves
ontomantlebeforereachingvalveterminus(Fig.
27). Deflectionofdistalrapheendpriortovalve
terminus is unique among gomphonemoid dia-
tomsstudiedthusfar. Smallprojectionoccursat
headpole(Fig. 28). Internally, stigmalopeningis
an elongate slit, terminating on central nodule.
Proximal raphe ends recurved. Pseudoseptum
prominent and helictoglossa visible at headpole
(Fig. 31).
Comments.—This presumably extinct mem-
beroftheLakeTanganyikafloraisdistinguished
by the angled, trullate shape of the valve. Al-
though not abundant in the core material, spec-
imensareeasilyrecognizedbythesizeandshape
ofthevalves.Gasse'sillustrationidentifiedasG.
africanum (1980: pi. 50, Figs. 25, 26) resembles
G. kilhamii. This speciesis dedicatedto the late
Peter Kilham, in honor ofhis work on African
lakes.
Gomphonema paddockii, Kociolek & Stoermer,
sp. nov. Figures 22-25. Gomphonema kilhamii, specimens from
(Figs. 32, 33;41,42) LakeTanganyika,core,station10, 100cm.Scalebar= 10^ni.
Description.—Valvesbroadlylanceolate-cla-
vate, 94-103 ^ni long, 20-21 uta broad. Wide IntheSEM, recurvedinternalproximalraphe
axialarea,extendingbeneathstriae,containsex- ends terminate on the edges ofcentral nodule.
panded, straight raphe. Striae radiate, strongly Internal stigmal opening elongate and ends on
radiate at the footpole, 10/10 nm at mid-valve, central nodule (Figs. 41, 42).
13-14/10 jum at poles. Stigma prominent, elon- Comments.—This taxon is, like G. kilhamii,
gate, runs from central nodule towards striae. presumedextinct,sinceitisconspicuousbutnot
HoLOTYPE.—Light microscopic preparation previously reported in the many studies ofRe-
#216040, CAS. cent diatoms from Lake Tanganyika. This spe-
IsoTYPES.—Light microscopic preparations, ciesisnamedinhonorofT.B.B.Paddock,former
ANSP and BM. Curator ofDiatoms at the British Museum, for
TypeLocality.—LakeTanganyika, core, sta- his excellent work on diatom taxonomy, ultra-
tion 10, 100 cm. structure, and systematics.
Figures 14—21. Gomphonemaafricanum, SEM, specimensfromLakeTanganyika,core, station 10, 100cm. Figures 14,
15.Externalviewoflinearcentralareawithelongatedstigmalopeningsandround,unoccludedpimcta.Scalebars= 2^mand
2.8Mm,respectively.Figure 16.Externalviewoffootpoleshowingraphebisectingapicalporefield.Scalebar=2.8nm.Figure
17. Internalviewofvalveshowingcentralnoduleandpoleswithpseudosepta.Scalebar= 10tim. Figure 18. Internalviewof
central noduleto headpole showingmarginal lamina (arrow) and large helictoglossa. Pseudoseptum is visiblenearheadpwle.
Scale bar = 5 /xm. Figure 19. Internal view offootpole showing pseudoseptum and large helictoglossa. Scale bar = 2 ^ni.
Figures 20, 21. Internal viewsofcentral nodulewith recurvedproximal rapheendsand elongateinternal stigmalopenings.
Scalebars = 2^m.
PROCEEDINGSOFTHECALIFORNIAACADEMYOFSCIENCES,Vol.47,No. 9
280
Figures 26-31. Gomphonema spp., SEM, specimens from Lake Tanganyika, core, station 10, 100 cm. Figure 26^ G.
ab3fa5rncu=amn1umMF,imgiunFrtieergn2ua7rl.evG2i.8e.kwiElsxhhtaoemrwiniia.nlgevxctieeenrwtnraaollfvhnieoeadwduplooeflwehiestahhdoprwoeilcneugrsvshleoidwt-iplnirkgoexrpiaumpnahcletarcauaprnhvdeinsegmnaodlsnl.topMramoratgnritunlsaeilobnelfaatomrivenaaltveiersme^in'nd^u.'sbSlocef^alvSeaclabvlaeer.b-SacraJl.se
KOCIOLEKANDSTOERMER: GOMPHONEMA FROMEASTAFRICA 281
Gomphonema aequatoriale Hustedt areanarrowatpoles, becomingbroadertowards
(Figs. 34-^0,43^7) center ofvalve. Single stigma present.
Valves lanceolate-clavate 25-60 ^m long, 8- In the SEM, puncta have external flaps and
10 Mm broad, with headpoles squared-off and punctaopeningsappearslit-Ukeorc-shaped(Figs.
55-57).Externalproximalrapheendsdilatedand
footpoles rounded. Striae punctate, parallel at
stigmalopeninground,positionednearproximal
headpole,becomingradiatetowardscentralnod-
rapheends(Fig. 55). Distal rapheendsdeflected
Mulme.nSetariraemirda-divaatleven,ea1r0-fo1o3t/p1o0le^.mStraitaepo8le-s1.0/E1x0- onto valve mantle (Figs. 55, 57). Porelli ofAPF
round,unoccluded,andphysicallyseparatedfrom
ternal opening ofsingle stigma positioned close puncta by unomamented area. In girdle view,
to end ofa median stria. Raphe lateral, slightly
each valve has two open, punctate girdle bands
undulate. Prominent septa and pseudosepta
(Fig. 56). One band closed at headpole, other
present at poles.
closedatfootpole. Eachcingulumhassmallsep-
In the SEM, puncta oblong, nearly circularor
tum. Pseudosepta and helictoglossae present at
tear-drop shaped and usually uniseriate, al-
though they may occur in rows oftwo. Occlu- poles (Fig. 58). Raised central nodule bears re-
curved proximal raphe ends and round stigmal
sionslackinginpuncta. Externalproximalraphe
opening (Fig. 59).
ends dilated and stigmal opening round (Figs.
43, 44). Atheadpoledistalrapheendcurvesand Comments.—The taxonomy of G. clevei is
tdiesrtmailnartaepsheonenmda.ntTlweo(Filgo.be4s4).ofAAPPFFbipsoercetleldiboyf tpooocrolnyfuusnidoenrrsetgoaorddianngdittshdiisstarpipbeuatriosn.toKhraavmemleerd
and Lange-Bertalot (1986) suggest that G. clevei
differentsizes (Fig. 45). Porelli round, similarin
shape to puncta but much smallerin size. Pseu- gisrcoouspmoopfolEiatsatn.AfFrriiccakne(s1p9e0c2i)meinlslu,str1a4t.e5d-a27smMalml
doseptapresentatpolesandhelictoglossaeoffset longand 4.5-6.5 Mm broad, with 9-13 striae per
fromrapheslitinternally(Fig. 46). Recurvedin- 10 Mm, and recent figures by Gasse (1986) are
ternal proximal raphe endsandan elongate stig-
similar to Fricke's original illustrations. Miiller
mal openingpresentoncentral nodule(Figs. 46,
(1905) described G. brachyneura, a linear-lan-
47).
— ceolate species also from East Africa, as 16-34
Comments. Hustedt (1949)described G. ae-
quatoriale as being 50-100 Mm long and 12-16 Mm long, 4-5 Mm wide, and having 13-15 striae
Mm wide. Hustedt's measurements are almost in 10 Mm; and Cholnoky (1954) considered G.
cleveiand G. brachyneuraconspecific. Hustedt's
exactly twice the values recorded for the popu-
(1938) concept ofG. clevei from Java, Bali, and
lationsfromLakeRudolfexaminedinthisstudy.
Sumatra appears to be different from Fricke's
Simonsen's (1987: pi. 527, Figs. 16-20) illustra- (Krammer and Lange-Bertalot 1986), in that
tionsofHustedt'sspecimensrangefrom30-57.5
Mm in length. Hustedt apparently erred in his Hustedt's figures have a more linear valve out-
line and broader axial area (Hustedt 1938; see
illustrationsanddescriptionofthisspecies. Oth-
also Krammer and Lange-Bertalot 1986). Hu-
erwise, populations described here are in accor-
stedtalsodescribedG. cleveivar.javanicaHust.,
dance with Hustedt's (1949) observations.
which differs markedly from the nominate va-
Gomphonema clevei Fricke riety in shape of the valve and striae pattern
(Hustedt 1938; Simonsen 1987). Subsequentre-
(Figs.48-59) portsofG. cleveimadefromEurope(Foged 1977,
Valveslanceolate-clavatewithbroadlyround- 1979), America (Patrick in Patrick and Reimer
edorprotractedheadpoleandroundedfootpole, 1975;Cambumetal. 1978)andAustralia(Foged
15-39 Mm long, 4-8 Mm broad. Radiate striae 1978)appearto foUow Hustedt'sconceptofthis
12-14/10Mm. Raphelateralandundulate. Axial species.AreconsiderationofthematerialofHus-
fim.Figure29.Externalviewoffootpoleshowingbilobedapicalporefield,withlobesbeingofdifferentsizes.Porelliareround
andextendarounddistalrapheendonvalvemantle.Scalebar= 2nm. Figure30. Externalviewofcentralareashowingtear
dropshaped puncta, roundedstigmal opening, anddilatedproximalrapheends. Scalebar= 2^m. Figure 31. Internal view
ofheadpoleshowingprominentpseudoseptum.Scalebar= 3.5^m.
282 PROCEEDINGSOFTHECALIFORNIAACADEMYOFSCIENCES,Vol.47,No. 9
Figures 32-40. Gomphonemaspp. Figures 32, 33. G. paddockii. specimen from LakeTanganyika, core, station 10, 100
cm.Figures 34-40. G. aequatoriale. specimensfromLakeRudolf Scalebar= 10tim.
KOCIOLEKANDSTOERMER: GOMPHONEMAFROMEASTAFRICA 283
Figures 41-45. Gomphonema spp., SEM. Figures 41, 42. G. paddockii, specimensfrom Lake Tanganyika, core, station
10, 100cm, internalviewsofcentralnodule showingrecurvedproximalrapheendsandelongatestigmalopening. Scalebars
= 10 tim and 2 ^m, respectively. Figures 43^5. G. aequatoriale, specimensfrom Lake Rudolf, external views. Figure 43.
Valveviewshowingoutline,narrowaxialareaanddilatedproximalrapheends.Scalebar= 5.5^m.Figure44.Centralnodule
toheadpole,withslit-likestriae,roundstigmalopening,anddistalrapheendextendingontovalvemantle. Scalebar= 2^m.
Figure45.Footpolewithbilobedapicalporefield.Porelliareroundandsmallerthanpuncta.Scalebar= 1.3 ^m.
284 PROCEEDINGSOFTHECALIFORNIAACADEMYOFSCIENCES,Vol.47,No. 9
Figures 46-47. Gomphonema aequatoriale, SEM, specimens from Lake Rudolf, internal views. Figure 46. Valve view
showingpseudosepta and helictoglossaeat poles and internally raised central nodule. Scale bar = 5 tim. Figure 47. Central
nodulewithbroadlyrecurvedproximal rapheendsandelongatestigmalopening. Scalebar= 1 ^m.
tedt, Foged,andothersisnecessarytodetermine ence to the need to lookat "entire populations"
ifCf. cleveiisindeedcosmopolitanorjustacom- (1987) to make "correct identifications" ofSu-
plex ofsuperficially similar taxa. Such a recon- rirella species is equally applicable to Gompho-
siderationmayalsodetermineifFricke'sspecies nema species.
is limited to East Africa.
Krammer and Lange-Bertalot (1986: pi. 164,
Discussion
Figs. 17-19) suggest intermediate morphologies
existbetween G. angustatum Agardh (=G. intri- Fourofthe five Gomphonema speciesconsid-
catum Kiitzing, Kociolek and Stoermer in press ered here appear unique relative to other pre-
c),G. rhombicumFricke,andG. clevei. Thespec- viously investigated members of the genus on
imens illustrated by Krammer and Lange-Ber- the basis of valve morphology. Gomphonema
talotdonotappeartoustoresembleoneanother africanum, G. aequatoriale, G. kilhamii, and G.
except in outline ofthe valves. The individuals paddockii all have elongated internal stigmal
are small(allabout 20 ixm), although it hasbeen openings and lack siliceous occlusions in the
well-documentedthat small specimensofdiffer- puncta. Most "typical" Gomphonema species
enttaxatendtoconvergeon similarshapesdur- haveshort,slit-likeinternal stigmalopeningsthat
ing size diminution (Geitler 1932). With refer- residemainlyonthecentralnodule(e.g.,Dawson
ence to groups of Surirella Turpin species, 1972, 1973)andhavesiliceousocclusionsonthe
Krammer and Lange-Bertalot (1987) have stat- exterior or interior ofthe puncta (Kociolek and
ed, "... ifthe smaller stages are examined . . . Stoermer 1990a, in press). These East African
thegeneraluniformityinvalveoutlineandvalve speciesareapparentlyendemictotheregionand,
surface hardly allows the two groups to be sep- consideringtheirmorphological similarities, may
arated." Krammer and Lange-Bertalot's refer- represent a distinct clade. These East African