Phylogenetic Position of Siphonocladiales Author(S): Mohammed Nizamuddin Source: Transactions of the American Microscopical Society, Vol

Phylogenetic Position of Siphonocladiales Author(s): Mohammed Nizamuddin Source: Transactions of the American Microscopical Society, Vol. 83, No. 3 (Jul., 1964), pp. 282-290 Published by: Wiley on behalf of American Microscopical Society Stable URL: http://www.jstor.org/stable/3224738 Accessed: 18-01-2018 15:18 UTC

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This content downloaded from 132.248.28.28 on Thu, 18 Jan 2018 15:18:43 UTC All use subject to http://about.jstor.org/terms 282 G. T. RIGGIN, JR. length, 336336 ,u; ,u; pharynx, pharynx, 52.8 52.8 ,u ,uin inlength, length, 24.0 24.0 , in , width;in width; primary primary claw clawbranch, branch, 13.6 ,u,u inin length;length; basal basal claw, claw, 10.8 10.8 , in , inlength. length. NEW RECORD:RECORD: Furman Furman University, University, Greenville Greenville Co., Co., S. C., S. Aug.C., Aug. 22, 1960.22, 1960.

SUMMARY

Thirteen species of tardigrades were collected primarily from the Appalachian Mountains of North and South Carolina. A few collections from Virginia and Ver- mont are included also in the study. Additional collection records are cited for Echiniscus (Echiniscus) virginicus, Pseudechiniscus suillus, Macrobiotus richtersi, M. echinogenitus, M. harmsworthi, M. intermedius, M. hufelandi, Diphascon angustatus, D. pinguis, and Milnesium tardigradum. Collection data and descrip- tions are given for Pseudechiniscus novaezeelandiae, Macrobiotus dispar, and Hypsibius (Hypsibius) zetlandicae, which have not been reported previously from the United States.

LITERATURE CITED

BAUMANN, H. 1960. Beitrag zur Kenntnis der Tardigraden in Nord-Amerika. Zool. Anz., 165: 123-128. BOUDRYE, M. R. 1960. Notes on the Tardigrada of Minnesota. Proc. Minn. Acad. Sci., 25: 195-199. CURTIN, C. B. 1948. The tardigrade fauna of the District of Columbia. Jour. Wash. Acad. Sci., 38: 251-255. 1957. Studies on the tardigrades. II. Some tardigrades from Maryland. Penn. Acad. Sci., 31: 142-146. HIGGINS, R. P. 1959. Life history of Macrobiotus islandicus Richters with notes on other tardigrades from Colorado. Trans. Amer. Microsc. Soc., 78: 137-157. 1960. Some tardigrades from the piedmont of North Carolina. Jour. Elisha Mitchell Soc., 76:29-35. MATHEWS, G. B. 1938. Tardigrada from North America. Amer. Mid. Nat., 19: 619-626. RAMAZZOTTI, G. 1956. Tre nuove specie di tardigradi ed altre specie poco comuni. Atti Soc. Ital. Sci. Nat., 95: 284-291. 1957. Due nueve specie di tardigradi extraeuropi. Atti Soc. Ital. Sci. Nat., 96: 188-191. RIGGIN, G. T. 1962. Tardigrada of southwest Virginia: with the addition of a new marine species from Florida. Tech. Bull. 152, Va. Agric. Exper. Sta., Blacksburg, Va., 145 pp.

PHYLOGENETIC POSITION OF SIPHONOCLADIALES

MOHAMMED NIZAMUDDIN Department of Botany, University of Karachi, Pakistan

In discussing Siphonocladiales three orders, Cladophorales, Dasycladales, and Siphonales, are relevant. The siphonaceous algae were known as Siphoneae (Greville, 1830) and later changed as Siphonales by Oltmanns (1904). The order Siphonocladiales was established in 1878 as Siphonocladiaceae (Schmitz, 1878). Goebel (1882) and Schmitz (loc. cit.) considered Cladophora of Siphonocladiaceae as an intermediate form between Confervoideae and the Siphoneae; Siphono- cladiales resembles the latter in the character of the protoplasm with its many nuclei, but their thallus is multicellular. Siphonocladiales, as the name indicates, shows resemblance with both Siphonales as well as with Cladophorales and was first established by Blackman and Tansley (1902) as Siphonocladeae but later changed into Siphonocladiales (Oltmanns, loc. cit.). According to Oltmanns, the

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order Siphonocladiales includes Cladophoraceae, Siphonocladiaceae, Valoniaceae, and Dasycladaceae. The order Cladophorales was known to the early phycologists as Conferveae (Harvey, 1849; Hassal, 1845). West and West (1897) and Boerge- sen (1903) considered it as order Cladophoraceae but later in 1904 it was changed into order Cladophorales by West (1904). Schussnig (1935) also has proposed distribution and composition of the Cladophorales and the Siphonocladales. Blackman and Tansley (loc. cit.) included all the Chlorophyceae with coenocytic cells capable of vegetative division in Siphonocladiales. Boergesen (1913) explained the meaning of the vegetative division characteristic of this order and termed as segregative cell division. Heydrich (1894) reported the formation of aplanospores (coniocysts of Zanardini) in Cladophoropsis Boerg. (= Spongocladia Aresch.) which produced daughter individuals that remained attached to the mother plant. These aplanospores of Heydrich were protoplasmic masses formed in consequence of segregative cell division-now a distinguishing feature of the Siphonocladales. Oltmanns (1922), Printz (1927), Smith (1933), Taylor (1928), and Tilden (1935) agreed with Boergesen that the vegetative division in Siphonocladiales is segregative cell division and included three families, Cladophoraceae, Dasycladaceae, and Valoniaceae, in this order. Affinities of this order were discussed by the earlier workers who linked it on one hand with Ulotrichales through Cladophoraceae and, on the other hand, with the Siphonales through Valoniaceae. Recently there has been discussion on the validity of the order Siphonocladiales by Chapman (1954), Egerod (1952), Feldman (1938), and Fritsch (1947). West and Fritsch (1927), Fritsch (1935), and Smith (1933) regarded Siphono- cladiales a grouping of two families, Cladophoraceae and Sphaeropleaceae, which are related to the Ulotrichales with two families, Dasycladaceae and Valoniaceae, whose phylogenetic relationships seem to be with the Siphonales. Smith (1938) suggested a solution by restricting the order Siphonocladiales to two families, Dasycladaceae and Valoniaceae, related to the Siphonales. Soon the order Siphonocladiales gained much importance as a disputable one, because some authors tried to amalgamate it either with Siphonales or with Cladophorales, while others retained it as a separate order. Fritsch (1935) placed the members of the Siphonocladiales under the family Valoniaceae of the order Siphonales retaining Dasycladaceae under the latter order because of their superficial resemblances, i.e., coenocytic condition and vesicular nature in the embryonic stage. Fritsch (1935) falsifies the work of Oltmanns (1922) by his word- ings, "I believe, however, that the majority of the facts speak for removal of the Cladophorales from the Siphonales to which they show in my opinion only superficial resemblances. They appear to be a group of septate forms which have developed along the line of their own." Thus, Fritsch excluded the Cladophoraceae from the Siphonocladiales but retained it as a separate order because of septations that are present both in the main axis and at the base of each branch, quite distinct from the Ulotrichales and the Siphonales. Multinucleate structure without any exhibition of segregative cell division also speaks for its removal. Cell wall with thick striation is also a chief character that can differentiate it from other orders. Wille (1907) included Cladophoraceae, Valoniaceae, and Dasycladaceae in the Siphonocladiales. Pascher (1921) agreed with Wille and added Siphono- cladiaceae in the order. Setchell and Gardner (1920) and Setchell (1926) also agreed with Wille and Pascher by including the members of the Cladophoraceae in Siphonocladiales. Boergesen (1934, 1936) accepted the inclusion of Cladopho- raceae and Dasycladaceae in the Siphonocladiales. Boergesen (1948) and Iyengar (1951) agreed with West by recognizing the order Cladophorales. Iyenger fol- lowed Fritsch in considering Dasycladaceae and Valoniaceae as families of the Siphonales.

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Feldman (1938) reestablished the order Siphonocladiales, suggesting relationship on one hand with Ulotrichales through Chaetomorpha and Ulothrix and on the other hand with Siphonales through Halicystis and Valonia. His views were also supported by Egerod (1952) but differ from Feldman by retaining Cladopho- raceae as a separate order. Chapman (19'54, 1962) also classified Cladophorales as family Cladophoraceae in the order Siphonocladiales, showing relationship with Ulotrichales. In addition to the Cladophoraceae, Chapman (1954) included Boodleaceae, Anadyomenaceae, Siphonocladiaceae, and Valoniaceae in the Sipho- nocladales. Smith (1938, 1955) retained the order as such but excluded the family Cladophoraceae and agreed with G. S. West (1904) in forming the order Cladophorales. Smith (1955) separated Dasycladaceae from Siphonocladiales and agreed with Pascher (1931) in establishing the order Dasycladales. Thus, in fact, Smith separated three orders-Cladophorales, Dasycladales, and Siphono- cladales-from the Siphonales. The order Dasycladales was known to the phycologists as Dasycladeae (Endlicher, 1843) and later on was changed into Dasy- cladaceae by Cramer (1888). Pascher (1931) raised the family to the rank of an order Dasycladales. Gilbert (1959) and McLean and Cook (1958) also included Cladophoraceae in the Siphonocladales. Fritsch (1947) and McLean and Cook (1958) regarded the genus Cladophora as the most advanced among the family Cladophoraceae. Chapman (1954, 1962) disagrees with the exclusion of the Cladophoraceae from the Siphonocladiales because of inadequate justification and he is also of the opinion that there is more or less orderly sequence of evolution from Cladopho- raceae leading to Valoniaceae. He argues further on the relationship between Cladophora and Microdictyon on the one hand and Cladophora and Cladophorop- sis on the other. According to Chapman (1954), the primitive family is Cladopho- raceae and that Valoniaceae represents the final stages in reduction and elimina- tion of septae within the order Siphonocladiales. Feldman (1952) has argued that the life cycle with regular alternation of generations is the most primitive. Studies on the life cycle of Microdictyon (Iyengar and Ramanathan, 1940) and Anadyomene (Iyengar and Ramanathan, 1941) have shown that there is regular alternation of generations in the life cycle of the species of these two genera. Cladopihora represents the most advanced type in the order Cladophorales and relationship lies more with Rhizoclonium, Lola, and Chaetomorpha than with any other form of Siphonocladiales. Following are the salient features on which Cladophoraceae may be excluded from Siphonocladiales, and the order may be retained as Cladophorales. Cladophora in contrast to Cladophoropsis has a septum at the base of the branch, which arises somewhat a little below the septum on the main axis. There is also no septation near the base of the young branches in Cla- dophora. Pseudoparenchymatous structure occurs in Siphonocladus as a result of segregative division whereas a uniseriate thallus occurs in Cladophorales. Microfibrils of cellulose crossing each other at right angles in three orientations occur in Cladophora and Spongomorpha but such fibrils are lacking in Siphonocladiales (Nicolai and Preston, 1959). In Valonia nuclei are somewhat longer than the chloroplast and lie internal to them, which is quite unlike the Cladophoraceae. In Valonia utricularis (Roth.) C. Ag. the formation of gametes is preceded immediately by meiosis, whereas in Cladophora meiosis occurs before zoospore formation. An alternation between morphologically identical diploid and haploid genera- ations occurs in marine Cladophorales and cytological alternation of

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generations occurs in freshwater Cladophorales, whereas only multicellular or coenocytic diploid generations occur in Dasycladales, Siphonales, and Siphonocladiales, and in which the gametophyte has been eliminated. Segregative cell division is unique in Siphonocladiales but not in Cladophorales where septations arise from outer layers and develop inward, thus, leaving a triangular-shaped space on each side of the wall to be filled in by folded lamellae. The mode of septations in Dictyosphaeria and Valonia, because of segregative cell division, is markedly different from that of Cladophorales. In contrast to the members of Siphonocladiales, the branching in Cladophora produced by a process known as evection or pseudodichotomy. In Siphonocladiales the zygote first germinates to form a vesicular structure and this ultimately divides by segregative cell division to form a filamentous habit whereas in Cladophorales the zygote generally germinates directly into a filamentous habit.

Although there are differences between Cladophorales and Siphonocladiales, they resemble each other in the following characters: In Cladophoropsis filaments are compactly or loosely arranged so as to form a ball-like or pad-like cushion which resembles subgenus Aegagropila of Cladophora. Cladophoropsis resembles Cladophora in filamentous structure with its uni- lateral branching and lack of mucilage. Filaments in the members of the Siphonocladiales are composed of coenocytes or multinucleate cells. The continuity of the main axis, unlike Siphonales, but like Cladophorales, breaks down by the presence of septations which lie always above the point of emergence of the branch. Occurrence of annular constriction in Chamaedoris, Ernodesmis, Siphono- cladus, and Struvea is comparable to Chaetomorpha. According to Nicolai and Preston (1952), there is similarity in wall structure between Dictyosphaeria, Siphonocladus, and Valonia and species of Cla- dophora. There is remarkable resemblance between the Cladophora type of thallus and that of Microdictyon mutabile (Chapman, 1954). Cell structure of the Siphonocladiales and Cladophorales is more or less similar, e.g., the presence of crispy wall and cytoplasmic lining. In Siphonocladiales the structure of the chloroplast-a single reticulum with numerous pyrenoids-is more nearly identical with that of Cladophora. In both Siphonocladiales and Cladophorales the vegetative growth is initiated by an apical cell. Food reserve is starch-like bodies in Siphonocladiales as well as in Cla- dophorales. Division of labor does not occur either in Siphonocladiales or in Cladophorales. Every cell acts as gametangium or sporangium except the rhizoidal cell. Mode of formation and liberation of zoospores and gametes is similar in Siphonocladiales and Cladophorales. Members of Cladophorales and Siphonocladiales reproduce asexually by means of bi- or quadriflagellate zooids which are produced in an unmodified cell which may escape singly and swarm freely. These two orders reproduce sexually by means of iso- or anisogametes but isogamy is more common. Isomorphic alternation of generations in Anadyomenaceae is identical with that of marine Cladophora and meiosis precedes zoospore formation (quadriflagellate) in Microdictyon.

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Cladophora crispata shows microscopical resemblances in septation to Cla- dophoropsis. The order Siphonocladiales also shows resemblances with Dasycladales and Siphonales. Their affinities and differences are described separately to demon- strate the phylogenetic relationship between them. Dasycladales and Siphonocladiales resemble each other in the following characters: Cysts or aplanospores develop in situ in both orders. Thalli of both are diploid. Sexual reproduction is generally isogamous in both orders. Members of both orders produce biflagellate gametes (rarely quadriflagellate gametes in Siphonocladiales). Reduction division occurs during gametogenesis in both orders. Siphoncladiales differ from Dasycladales in the following characters: Dasycladales possesses a whorled arrangement of lateral branches and inde- pendent disc-like plastids whereas the Siphonocladiales has multicellular thalli and reticulate plastids. The members of Dasycladales possess uninucleate cells but multinucleate in the Siphonocladiales. In Dasycladales the sigle large nucleus breaks up in the rhizoid and the frag- ments, which may change, move up the siphon into the gametangia, whereas in Siphonocladiales the nuclei remain in situ. Reproductive organs are apically or laterally specialized in Dasycladales but not in the Siphonocladials (Cladophoropsis). Extensive calcification is exhibited in Dasycladales but not Siphonocladiales. Siphonocladiales resembles Siphonales in the following characters: Septation in Siphonocladiales may be compared with that which occurs during reproduction in the Siphonales. Coenocytic nature of the cell occurs in both the orders. Occurrence of nuclei internal to the chloroplasts in some species of Valonia shows superficial resemblance to the members of the Siphonales. Reduction division occurs during gametogenesis, and the thallus in both the orders is diploid. In Siphonocladiales the cysts (aplanospores) develop in situ instead of outside the parent plant in Siphonales. Zygote on germination gives rise to a vesicle-like structure in Valonia as well as in Cladophoropsis and such structure is one of the characteristic features of Siphonales. Siphonocladiales and Siphonales are distinguished from each other in the following characters: Production of uninucleate, multiflagellate zoospores in Derbesia (Halicystis) is of common occurrence in contrast to biflagellate (rarely quadriflagellate) zoospores in Siphonocladiales. Reproductive organs are specialized in Siphonales whereas they develop in unmodified cells in Siphonocladiales. There is calcification in some members of the Siphonales (Codiaceae and Udoteaceae), whereas it is lacking in the Siphonocladiales. Dasycladales, Siphonales, and Siphonocladiales are purely marine and found in tropical as well as in subtropical seas but few genera, and few species of Cla- dophora occur in fresh as well as in brackish water. The observations on Dasycladales, Cladophorales, Siphonales, and Siphono-

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SIPHONALES

DASYCLADALES

Valonia

SIPHONOCLADIALES A \ Protosiphon Prasinocladus

CLADOPHORALES \ A Characium

ULOTRICHALES -Chlorosphaera -CHLOROCOCCALES

VOLVOCALES

Tetrasporaceae Palmellaceae > alacCHLAMYDOMONAD TYPE (Motile)

FIG. 1. Diagram showing the interrelationship among the orders.

cladiales show that they may be retained as separate orders. Among these four orders Cladophorales and Siphonocladiales are very confusing ones. The family Anadyomenaceae, which includes Anadyomene and Microdictyon, is primitive with an isomorphic alternation of generations and the formation of quadriflagellate zoospores. In this family there is septation and absence of segregative division. These characters bring this family nearer to Cladophorales but the presence of tenaculae in this family is a Siphonocladiales character. It is evident that the Anadyomenaceae is intermediate between Cladophorales and Siphonocladiales and is regarded here as the primitive family of Siphonocladiales. It is now considered necessary to discuss the evolution among these orders. Generally there are two accepted views on chlorophycean evolution. One view is that the Palmellaceae is the primitive family of the Protococcales (Chodat, 1897), whereas the other view is that the Chlamydomonadaceae is the most primitive group (Blackman, 1900) and in due course these motile unicells aggregate to form spherical colonies culminating in Volvox. A third view held by Thompson (1958) is that Chlorophyceae have had their origin in the multinucleate aggregates through Synchytrium, a fungus. According to Thompson, the Dasycladales and Siphonocladiales are offshoots from Siphonales which is derived from multinucleate aggregates. West and Fritsch (1927), Smith (1938, 1955), and Thomp- son (1958) have suggested that Cladophorales is an offshoot from Ulotrichales. Dr. M. A. F. Faridi1 holds that the Cladophorales is an offshoot from Siphonales and not from Ulotrichales. In agreement with Blackman (1900) the Chlorophy- ceae have evolved from uninucleate motile Chlamydomonas which is primitive and the multinucleate aggregates are advanced. 1 Personal communication from Dr. M. A. F. Faridi.

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Blackman (1900), Chapman (1962), and Oltmanns (1904) agree that the Siphonocladiales are derived from uninucleate groups such as Ulotrichaceae, by repeated division of the nucleus rather than from the Siphonales. Papenfuss (1951) holds that Cladophorales, Dasycladales, Siphonales, and Siphonocladiales are derived from the Chlorococcales independently. The coenocytic habit is well- developed among the Cladophorales, Siphonales, and Siphonocladiales except Dasycladales. This habit is of common occurrence in the Chlorococcales, especially in the mature cells before reproduction. This tendency may have led to the evolution of the Siphonales through Protosiphon and of Cladophorales through Prasinocladus or through Valonia from Siphonocladiales. Siphonales is probably "a reduction from forms like Cladophorales." This reduction may be possible through dendroid forms like Prasinocladus. Siphonocladiales probably have evolved by reduction of septum at the base of the branches from the Cladophorales through Cladophora. The order Dasycladales has originated from the Siphono- cladiales through Chamaedoris which bears a whorl of branches at the apex of the stalk. In Dasycladales the single nucleus primary by subsequent division gives rise to the multinucleate condition as in Acetabularia and Neome'ris. This feature also shows that Siphonales probably have derived from the Dasycladales. A suggested diagrammatic scheme (Fig. 1) shows the interrelationships among the orders of the Cladophorales, Dasycladales, Siphonales, and Siphonocladiales.

SUMMARY

Cladophorales, Dasycladales, Siphonales, and Siphonocladiales are retained as separate orders and their distinguishing features and interrelationships are discussed. A suggested scheme of interrelationship among these orders has been made.

ACKNOWLEDGMENT

The author is highly indebted to Dr. A. K. M. Nurul Islam, Department of Botany, University of Dacca, and to Dr. M. A. F. Faridi, Department of Botany, University of Peshawer, for criticism and suggestions in the manuscript.

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GASTROPOD LARVAE FROM THE BROOD POUCH OF AN ARCTIC SHRIMP'

JAMES E. MCCAULEY Department of Oceanography, Oregon State University, Corvallis

Gastropods are known to attach their egg capsules to many living creatures, especially to the surface of plants and snail shells. Lebour (1937) reported certain species that laid their eggs within sponges and compound ascidians. Holthius (1941) found eggs of a gastropod of the genus Epistethe on the pleopods of a stomatopod crustacean, Gonodactylus chiragra. This paper reports the first record, to my knowledge, of attachment among ovigerous shrimp eggs. While examining specimens collected in the Chukchi Sea, I found two ovigerous shrimp, Argis lar (Owen, 1839), which had gastropod egg capsules among their embryos. The capsules contained larvae in various stages of development, from freshly deposited egg capsules to well-developed embryos with a shell of two whorls. The identity of the snails could not be ascertained, but the shape of the shell and the structure of the operculum are similar to Buccinum. Two specimens of Buccinum polare (Gray, 1839) taken in the same collection appear to have the same general shell pattern as the larvae. The nuclear regions of the adults are badly eroded however, and the shell cannot be compared satisfactorily to the shells of the embryonic snails. On the other hand, the egg capsule is thin-walled and transparent and unlike known Buccinum egg capsules, which are horny and usually deposited in large masses (Lebour, 1937). Our knowledge of larval stages of marine gastropods is quite incomplete. Thorson (1946) reviewed the field and included the important literature. A study of all available life history stages in the literature has not revealed the 1 Research supported in part by a grant from the Office of Naval Research under contract Nonr 1286(02).

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