On the Identity of Spongocladia and Cladopboropsis'

GEORGEF. PAPENFUSS2

IN THEIR TREATMENTS of the green algaein Engler and Prantl's "Die N ariirlichenPflanzenfamilien," Wille (1 911 : 119 ) andPrintz (1927 : 282) consider 'SpongocladiaAreschoug (1853 ) as a genus of question­able merit. This belief was founded upon theobservation of Weber-van Bosse (1890) thatexamples of Struvea delicatu la which livedin association with the sponge Halichondriabore a great resemblance to Spongocladiavaucheriaeformis, the type species of thegenus Spongocladia. ,

However; in a later 'work, W eber-van Bosse(1913 : 86) not only maintained Sponge­cladia but emphasized that she had not dem­onstrated that S. vaucheriaeformis actuallywas a form of Struvea delicatula living inassociation with a sponge, and that there con­sequently was no justification for the state­ment of Wille (loc. cit.}: , "Nachdern es vonA. Weber v. Bosse nachgewiesen worden ist,dass die typische Art: S. vaucheriaeformisAresch. nur eine durch Symbiose mit einerSpongie (Halichondria) umgebildete Struvea­Art darstelle, muss auch die Stellung der 2iibrigen Arten : Spongocladia dichotoma(Zanard. ) Murr. et Boodle, sowie S. neocale­donica Grun. als sehr zweifelhaft angesehenwerden."

Even though there probably is no partic­ularly close relationship between Sp ongocla­dia and Struvea Sonder (1845), both of whichbelong to the order Siphonocladales, but tothe families Siphonocladaceae and Boodlea­ceae, respectively, I haveon a number of oc-

' This study was made during the tenure of aGuggenheim Fellowship.

' Department of Botany, University of Califor­nia, Berkeley, Californi a. Manuscript receivedFebru ary 1, 1950.

casions been struck by the agreement in thepublished descriptions and illustrations ofSpongocladi« and Cladopboropsis Bergesen(1905), both memb ers of the family Sipho­nocladaceae. The purpose of the present arti­cle is to assemble the published facts and to

record my own observations in support of thecontention that these two genera of essen­tially tropical and subtropical marine algaeactually are identical, a conclusion whichBergesen (1948) has also reached. Finally,Cladophoropsis,which is the better knowngenus, is proposed for conservation againstSpongocladia.

The genus Spongocladia was erected by].E. Areschoug in 1853 upon a new species,S. oaucberieeiormis, which he received fromMauritius . The plants grew upon encrustingcorallines, forming a horizontal spongiosemass, from .which issued erect, more or lessdichotomously divided, spongiose growths.Both the horizontal and the erect port ions ofthe thallus were composed of irregularlybranched, septate, uniseriate filaments and, asshown in Areschoug's figure 3, the branchesof the filaments lacked a cross wall at thebase. Reproduction appeared to be by swarm­ers, many of which germinated within thecells in which they were produced. The thal­lus contained an abundance of sponge spic­ules, especially at the terminal ends of theerect portions.

Thirty years later the known geographicdistribution of Spongocladia vaucheriae formiswas extended to Singapore by Hauc k (1884 ).His study of the plant led him to the signif­icant conclusion that systematically it be­.Ionged in the immediate vicinity of Siphono­cladus, a genus which had been founded afew years previously by Schmitz ( 1879) to

[ 208 J

Spongocladia vs. Clad oph oropsis-PAPENFUSS

accommodate two species, one of which wassubsequently removed to Cladopboropsis byB¢rgesen ( 1905) "

In 1888 Murray and Boodle published anaccount of the genus Spongocladia basedupon a study of material of S. vaucheriae­[ormis from Mauritius and New Guinea andof two additional species from the south Pa­cific. They pointed out for the first time thatthe genus Spongodendron of Zanardini(187 8), which was based upon two species(S. crassum Zanard. and S. dicbotomum Za­nard .) from New Guinea, was indistinguish­able from Spongocladia. Spongodendron

-crassum. was found to be identical with Spon­gocladia vaucheriaeformis whereas Spongo­den dron dichotomum could be maintained asa distinct species under the binomial Sponge­cladia dichotom a (Zanard.) Murray et Boodle.In addition , Murray and Boodle gave a briefaccount and the formal diagnosis of a newspecies from New Caledon ia, Spongocladianeocaledonica Grunow, which differed fromthe others in having a compact thallus.

. Up to the present no additional species ofSpongocladia appear to have been described,but our knowledge of the genus has been en­larged in certain respects and the known geo­'graphical range of two of the species has beenextended.

Heydrich (1894) reported S. vaucheriae­formis .and S. dicho toma from the RyukyuIslands, south of Japan. He was the first tobring attention to the fact that the thalli werenot composed of a single plant but of a largenumber of individual Cladophora-like plants.In agreement with the observations of Zanar­dini and Murray and Boodle, he found thatthe filaments composing the thallus producedattachment organs, or tenaculae, by means ofwhich they anastomosed with near-by fila­ments, forming a kind of network.

Heydrich was .also the first to give.an ac­count of the method of formation of the so­called aplanospores (or coniocysts, as theyhad been called by Zanardini ). He regarded

209

Sp ongocladia as essentially a unicellular alga ,which, like Valonia, formed aplanosporeswhich produced daughter individuals that re­mained attached to the mother-plant. As wenow know, the aplanospores of Heydrichwere protoplasmic masses formed in conse­quence of segregative division, a characteris­tic feature of the order Siphonocladales. LikeHauck, Heydrich placed Spongocladia nearSiphonocladus.

In 1913 Weber-van Bosse recorded S. vau­cheriaef ormis from Makassar and neighbo r­ing islands in the Dutch East Indies. She ex­pressed the opinion that Spongocladia prob­ably represented special forms of algae knownotherwise by different names.

Okamura in 1916 recorded the occurrenceof S. vaucheriaeformis at Ponape and Saipanin the Caroline and Marianas Islands, respec­tively. In a later work ( 1928) , he confirmedthe observation of Areschoug regarding thegermination of spores (?) within the cellsin which they were formed. He also saw andfigured stages in their germination on theoutside of filaments of the thallus. Theger­mination of spores ( ?) within the reproduc­tive structures was later observed by Yamada( 1934-) also. Heappears to have been thefirst to have noted pores In the walls of thefertile cells, which suggests that the spores (?)are motile and that those which had beenseen within the cells had merely failed toescape, as is so often true in the algae.

Although Okamura ( 1928) does not seemto have been fully aware of it, he clearly ob­served (see pI. 250, fig. 11 ) septation of thefilaments by segregative division, thus con­firming the observation (in the light of pres­ent knowledge ) of Heydrich.

As far as I am aware, Dickie (1875 ), Jadin(1934), Lucas (1935) , and Bergesen (1940,1946, as well as 1948) are the only authorsin addition to those already mentioned whohave studied Sp ongocladia. Dickie, Jadin,and Bergesen included S. vaucheriaeformis intheir ,lists of algae from Mauritius , whence

210

the species was first described, and Lucas re­ported it from Lord Howe Island.

In summary, then, a synthesis of the ac­cumulated knowledge concerning the generaimorphology of Spongocladia reveals the fol­lowing features as most characteristic of thegenus:

1. The thallus is in the form of a pros­trate, spongiose growth, which remains as acompact mass in S. neocaledonica or produceserect, branched, Codium-like processes in S;uaacberiaeiorm is and S. dichotoma.

2. The thallus, is composed of intertwin­ing, branched, septate filaments, with thecells arranged in a single series.

3. The branches of the filaments are notseparated by across wall at the point of june­ture with the parent filament.

4. Septation of the filaments is by segre­gative division.

5. The filaments form attachment organs ,or tenaculae, by means of which they anas­tomose with other filaments, forming a kindof network.

6., Reproduction is by swarmers whichare produced in the unmodified cells' of thefilaments.

These characters, with the possible excep-.tion of the first one listed above, indicate thatSpongocladia Areschoug (1853) is identicalwith Cladopboropsis, a genus which was seg­regated from Siphonocladus Schmitz (1879 )by Bergesen in ',1905. This conclusion issupported by my own observations .(partic­ularly in regard to the absence of a cross wallat the point of attachment of the branchesto the parent filaments ) upon a species ofSpongocladia (seemingly S. vaucheriaeformis)from the Philippine Islands and by those ofBergesen (1946, 1948) uponS. uaucberiae­formis from Mauritius. The agreement inthe general appearance of the filaments com­posing the thallus in Spongocladia and Clado­pboropsis is shown in Figure la and b, re­spectively, which are reproductions "of illus­trations by Bergesen from material gathered

PACIFIC SCIENCE, Vol. IV, July, 1950

in the type regions of the type species of thetwo genera.

The observations of B~rgesen in this con­nection are especially significant inasmuch asthey were made, not only upon 'topotype ma­terial of the type species of Spongocladia, butby the author of Cladopboropsis. In 1946(p. 17) he remarked: "According to myobservations of the alga (S. vaucheriaeformisJ ,it seems to me very like Cladopboropsis, forinstance, Cl. Zollingeri ..." and in 1948(p. 24) he said, "the alga, ' being the biontof the sponge, is quite like that found in theformerly examined specimens, and thus inmy opinion is a Cladopboropsis" ,

Seemingly, the only difference betweenSpongocladia and Cladopboropsis lies in thegeneral habit of the two genera. In Clado­pboropsis the thalli are in the form of cush­ions, turfs , or tufts whereas in two of thespecies of Spongocladia (S. vaucheriaeformisand S. dichotoma) the basal prostrate systemordinarily produces erect, Codium-like por­tions. However, these differences are notconstant and appear to be of a specific ratherthan a generic nature. Support for this con­tention is furnished by two facts: <,1 ) InS;' neocaledonica the thallus is in the form ofa compact, barely branched growth, some­what comparable to that of Cladopboropsismembranacea (Bergesen, 1913: 43 and 47)and certain other species in which the thallusis in the form of dense cushions or turfs.(2 ) Even in S. vaucheriaeformis the thallusmay at times, according to Bergesen (1948 :23), be in the form of an extensive prostratemat, with the erect portions reduced to con- ,ical growths of only 2-3 ern. in height.

Since the time that Bergesen (1905)erected Cladopboropsis, and transferred to 'itseven species which had previously beenplaced in SiphoilOcladus, the genus has beenfound to be well represented in tropical andsubtropical waters, and to contain a few spe­cies which are known only from temperateregions. A search through the literature re-

Spongocledi« vs. :Cladophoropsis- PAPENFUSS 211

a

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the past 45 years as contrasted with Sponge­cladia, which has been referred to in a com-

. paratively small number of publicat ions, itwould be advantageous to reject . the lattername in favor of the former, and it is ac­cordingly proposed that Cladopboropsis beconsidered for conservation.CLADOPHOROPSIS Bergesen ( Siphonoclada­ceae ) , K. Danske Vidensk. Selsk. Forhandl.1905 : 288, 1905. .

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FIG. 1. a, Spo ngocladia vaucheriaeforntis: filaments from the uppe r part of the thallusof a plant from Mauritius. X 45. b, Cladopboropsis memb ranacea: a part of the cushion­like thallus of a plant from the Virgin Islands . About X 5. (From Bergesen, 1948 and1905, respectively.)

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212

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Spongocladi« V5. Cladophoropsis- PAPENFUSS

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