Aquatic Botany, 16 (1983) 251--267 251 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

THE BRAZIL IAN SEAGRASSES

EURICO C. de OLIVEIRA F., JOSE R. PIRANI and ANA M. GIULIETTI

Departmento de Bot~nica, Universidade de S. Paulo, C. Postal 11461, S~o Paulo, SP (Brazil)

(Accepted for publication 25 January 1983)

ABSTRACT

Oliveira F., E.C. de, Pirani, J.R. and Giulietti, A.M., 1983. The Brazilian seagrasses. Aquat. Bot., 16: 251--267.

Based on a critical review of the literature, and on abundant material recently col- lected along the coast of Brazil, a synthesis of the occurrence and distribution of the Brazilian species of seagrasses is presented. Two species of Hydrocharitaceae, namely Halophila baiUonii Aschers. and H. decipiens Ostenf., and three species of Potomogeton- aceae, Halodule ernarginata den Hartog, H. wrightii Aschers. and Ruppia maritima L. s.s., were found. Ruppia maritima was found all along the Brazilian coast, from about 3 to 32S latitude, in brackish water ponds and lakes, with salinities varying from 0.3 to 28]00. The other species are restricted to normal seawater (35/00), although Halodule wrightii was also found in hypersaline waters (45/oQ). This last species is the most common seagrass in Brazil. The species of Haiophila are restricted to warmer waters and were not found further south than Rio de Janeiro State, being especially common on the NE coast at depths down to 62 m. During the course of these studies, Halophila baillonii was found for the second time in Brazil since its original collection in 1888. A critical comparison of a large number of plants leads us to the conclusion that Halodule brasiliensis Lipkin cannot be distinguished from H. wrightii, and H. lilianae den Hartog cannot be distinguished from H. emarginata. Reproductive structures of H. emarginata are described for the first time.

INTRODUCTION

In a recent paper about the seagrasses o f Braz i l , den Har tog (1972) em- phas izes that " there is hard ly anyth ing known about the occur rence o f seagrasses in South Amer ica" and that "one wonders whether these p lants are ext remely rare or absent ... or have been over looked by botan is ts" . In an extens ive survey a long the coast o f Braz i l , we conc luded that the la ter hypothes is is the cor rect one , as these p lants can fo rm the dominant vegetat ion in large areas o f the l i t to ra l zone . Th is omiss ion has probab ly occur red because the ang iosperm exper ts are ch ie f ly te r res t r ia l and wander in land ra ther than a long the sea border , wh i le the "mar ine botan is ts" are phyco log is ts , and are more in teres ted in the a lgae that g row on the leaves o f the seagrasses than in the i r subst ra tes .

0304-3770/83/$03.00 1983 Elsevier Science Publishers B.V.

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This paper gives a large number of new localities for the seagrasses oc- curring along the Brazilian coast, in addition to some primary informa- tion about their ecology and a critical analysis of former references. An identification key plus selected figures of diagnostic characteristics are also presented to stimulate further research.

Although some authors do not consider Rupp ia to be a seagrass (den Hartog, 1981), this genus is included here as it is also found in waters of variable salinity and subjected to tidal fluctuation,

KEY TO THE SEAGRASSES FROM BRAZIL

Leaves linear, ligulate, with tannin cells; ovary uniovulate ................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P O T A M O G E T O N A C E A E

Plants with hermaphrodite flowers, protandrous. Leaf blades tapering towards the acute, pointed tip. Carpels long stipitate in fruit ...........

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RUPP IA- R. maritirna Plants dioecious. Leaf blades of uniform width or slightly tapered; leaf- tip bi-tricuspidate, obtuse or emarginate. Carpels subsessile . . .HALODULE

Leaf-tip bicuspidate to tricuspidate, often with 2well

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stipitate in fruit; stipes 8--14 mm long. Fruitlets drupaceous, dorsally rounded, 1.5--2.0 mm long and ca. 1.5 mm wide, beak 0.4--1.0 mm long; podogynes 8--14 mm long.

Material studied: PIAUI: Amarra~o, col. Andrade Lima 54-1888, 17-VII-1954 (IPA). CEAR.~: No brejo, col. Freire Allena~o 1472 (R). PERNAMBUCO: Tanque de Alevina- gem, 16/0a, Ilha de Itamarac~, col. Oliveira F. 27-V-1980, 29-IV-1981, 21-VII-1981 (SPF). ALAGOAS: Lagoa do Mundau, Macei6, col. Andrade-Lima & A.M. Lima, 26-VL 1970 (IPA). RIO DE JANEIRO: col. P. Schwacke (R);Praia do Leblon, Rio de Janeiro, col. J.R. Pirani 114 & I. Cordeiro, VII-1980 (SPF). SAO PAULO: Ilha Diana, Santos, col. A. C.H. Miranda, 3-V-1981 (SPF). SANTA CATARINA: Praia Braba, Itajai', col. L.B. Smith & R. Klein 7296 (R); Lagoa da Concei~o, Florian6polis, col. E. Tremel, 30-IX- 1979 (SPF). RIO GRAN DE DO SUL: Saco da Mangueira, col. U. Seeliger, 12-XII-1977 (SPF).

References to Brazil: Alagoas, Rio de Janeiro, Tijuca, Laguna de Freitas (Schumann, 1894); Lagoa Rodrigo de Freitas (Hoehne, 1948). Rio Grande do Sul: Lagoa dos Patos (Cafruni et al., 1978; Capitoli et al., 1978).

The distinction of the infrageneric taxa in Ruppia is by no means clear. Verhoeven (1979) has made a systematic review of Ruppia, where he con- siders two possibilities: recognition of a single species in the genus, R. maritima L. s.1.; or 2 species, R. maritima L. s.s. and R. cirrhosa (Pet.) Grande (syn. R. spiralis L. ex Dumort.) distinguished by the length of the inflorescence peduncle and by its degree of spiralling.

The separation of the 2 varieties of R. maritima L. s.s., based on the length of the podogyne (viz. longer than 5 mm= R. maritima var. maritirna; shorter than 5 mm = R. maritima vat. brevirostris Agardh) is, as Gamerro (1968) has pointed out, purely conventional, since it is a very variable characteristic, showing intermediate forms within the same inflorescence.

As is depicted in our map, R. maritima is distributed practically all over the Brazilian littoral. Although we do not have references to the northern- most provinces, its occurrence there can be predicted as it is present in the Caribbean and northwards.

The specimens studied showed consistently narrow leaves (0.3--0.5 mm) and short and straight peduncles. However, the plants from north- east Brazil presented long beaked fruitlets (beak up to 0.8 ram), while in plants from the south they are shorter (beak less than 0.5 mm) (Fig. 25).

Cafruni et al. (1978) refer to the occurrence of R. maritima var. curvicarpa (A. Nelson) Fern. & Wieg. at Lagoa dos Patos, with long and spiralled peduncles that would correspond to R. cirrhosa. However, those authors do not indicate specifically the studied material, and that variety is not quoted in more recent papers such as those of Gamerro (1968) and Verhoeven (1979). The material we studied from Lagoa dos Patos had only fruits with straight and short peduncles, with vegetative character- istics agreeing perfectly with the usual concept of R. maritima L. s.s. There- fore, we refer the Brazilian material to R. maritima L. s.s.

The occurrence of plants with short peduncles all along the Brazilian

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coastline, and of others with longer peduncles restricted to the extreme south of Brazil, would support the remarks of den Hartog (1981) about the distribution of this genus.

The reference to R. maritima as the only seagrass occurring in the vicin- ity of S~o Paulo, as given by Diaz-Piferrer (1967), may be a mis-indentifica- tion of the species of Halodule that are very common in that area.

In Brazil, R. maritima seems to favour sheltered areas with brackish waters and fine muddy--sandy substrate. We collected plants in fish ponds in northeastern Brazil with salinities ranging from 8 to 28% 0 during the year. Cafruni et al. (1978) found it in Lagoa dos Patos (32S), at salinities ranging from 0.30 to 26.440/0o. There are no references to the species in waters of full marine salinity (36% 0), on the sea-shore. Extensive sub- mersed prairies of this species occur in shallow areas of Lagoa dos Patos, in the southern part of Brazil, where it is the dominant vegetation during the summer months (Capitoli et al. 1978; Cafruni et al., 1978).

2. Halodule wrightii Aschers. Sitzber. Ges. Naturf. Fr. Berlin p. 19, 1868 Figures 8--12 H. brasiliensis Lipkin, Rev. Brazil. Biol. 40, p. 86, 1980 Rhizomes 0.2--2.0 mm in diameter; internodes 0.4--3.5 cm long. Leaf-

sheath 1--4 cm long; leaf-blade (2--) 12 (--22) cm long and (0.2--) 0.4 (--1.0) mm wide, narrowed at the base, midrib usually excurrent in a small tooth, lateral nerves inconspicuous, but often ending in a narrow tooth usually longer than the median tooth, apex bicuspidate to tricuspidate, inner side of the lateral teeth more or less concave, sometimes with a few, very small, irregular serrations. Staminate flowers on a stalk 1.0-2.4 cm long; anthers slender, the lower one ca. 3.5 mm long, the upper one 4.0 mm long, coloured red by numerous tannin cells. Carpellate flowers with an obovoid or globose ovary, ca. 1.5 mm long, with a lateral or terminal style 1.0-2.6 cm long, ovary and style coloured red by tannin cells. Fruit obovoid, slightly compressed, ca. 2.5 mm long, with a persistent lateral style or a very short rostrum.

Material studied: RIO GRANDE DO NORTE: Maracajau, col. Oliveira F., 16-II-1976 (SPF); Muriu, col. Oliveira F., 29-V-1980 (SPF). PARAIBA: Ponta do Bessa, Jo~o Pessoa, col. F. Carvalho, 9-X-1977 (SPF). PERNAMBUCO: Praia de Nossa Senhora do O, Paulis- ta, col. Andrade-Lima 57-2815, 24-XI-1957 (IPA); Praia da Ilha de Itamarac[, col. Andra- de-Lima 58-3285, Praia de Jaguaribe. ]]ha de Itamarac~, col. Oliveira F., 8-XII-1980 (SPF); Prala Forno de Cal, ]]ha de Itamarac~, col. Oliveira F., 10-XII-1980 (SPF); Praia do Pilaf, ]]ha de Itamaracil, col. Oliveira F., 21-VII-1981 (SPF). ALAGOAS: Praia de Paju~a- ra, Macei6, col. Oliveira F., 18-VII-1981 (SPF). BAHIA: Praia Coroa Vermelha, Sta. Cruz Cabralia. col. J.R. Pirani Ill, L. Rossi & I. Cordeiro, 28-I-1980 (SPF);Mar Grande, Ilha de Itaparica, col. Oliveira F., 16-VII-1981. RIO DE JANEIRO: Restinga eta Marambaia, col. Oliveira F., 28-IX-1977 (SPF); Monsuaba, col. Oliveira F., 19-XI-1979 (SPF); Lagoa de Araruarna, col. Oliveira F., 8-V-1981 (SPF); Canal da Lagoa de ArartLama, col. Oliveira F., 8-V-1981 (SPF); Praia Rasa, col. Oliveira F., 28-VIH-1981 (SPF). SAO PAULO: Praia do Cod6, Ubatuba, col Oliveira F. & E.J. Paula, 21-XI-1979, 30-I-1980 (SPF), col. I. Lude-

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wigs, 15-V-1980 (SPF), col. Oliveira F., 10-VI-1980 (SPF), I0-IX-1980 (SPF), col. E. Plastino, 21-XI-1980 (SPF).

Additional material studied: PUERTO RICO, col. P. Ascherson 3357, 23-I-1886 (K); salinas de Cabo Rojo, 6-II-1895 (K). CUBA: col. C. Wright 3720, 1-1869 (K). TRINI- DAD: Chacachecare, col. N. Simmonds 15033, 2-I-1954 (K). SAO DOMINGOS: Prov. Bahona, prdx. Ponta Inglesa, col. Pe. Miguel Freitas, V-1911 (K). HAITI: lie de la Tortue, col. E.L. Ekmar, 2-VI-1925 (K).

References to Brazil: Paracuru (den Hartog, 1972). Pernambuco: (Andrade-Lima, 1960; Laborel-Deguen, 1963); Ponta de Pedra, Suape (den Hartog, 1972). Paraiba: (Laborel-Deguen, 1963). Bahia: Mar Grande, Ilha de Itaparica, Salvador (den Hartog, 1972). Espirito Santo: Praia do Sacrd-Coeur, Vitoria (den Hartog, 1972).

In the numerous populations of Halodule wrightii that we have studied, particularly those from the states of Pernambuco, Paraiba and Rio Grande do Norte, we have found a tricuspidate leaf-apex, which recalls Halodule beaudettei (den Hartog) den Hartog. On the other hand, specimens from populations collected in the states of Rio de Janeiro and S~o Paulo show a bicuspidate, rarely tricuspidate leaf-apex (Fig. 25). Lipkin (1980) de- scribed a new species of Halodule, H. brasiliensis, based on leaf-tip mor- phology of a sample collected at Fortaleza in NE Brazil. He concluded that the new species was very close to H. beaudettei, and could even be a form of this species, differing in having an obtuse, rather than acute, median tooth, usually shorter than the lateral ones. However, according to Haynes and Wentz (1975) and to Eiseman (1980), H. beaudettei should be included under H. wrightii, as the leaf-tip variation within a single pop- ulation encompasses the morphological ranges of the 2 taxa. The plasticity of leaf-tip morphology in Halodule spp., and therefore its unsuitability as a criterion to erect new species, was further demonstrated by McMillan and Phillips (1979) and McMillan (1980). This is in agreement with our observations (Fig. 9).

This species has a broader distribution and is much more frequent than the other species of Halodule, H. emarginata den Hartog, found on the Brazilian coast. It grows on sheltered to moderately sheltered sandy-- muddy shores, usually from about Low Water Spring Tide (LWST) to a depth of about 3 m. Plants exposed at low tides have shorter leaves com- pared with those permanently immersed. The species was collected in waters with salinities varying from 30 to 40o/00. Although it goes as far south as Ubatuba (2330'S), it is much more abundant towards the north, in warmer waters. On the northeast coast of Brazil, it forms extensive beds on large areas behind the reef edges, being associated with several species of algae, particularly Siphonales, Dictyotales and Ceramiales. In some places, such as Ilha de Itamarac~, drifted leaves of H. wrightii pile on the beaches in large quantities.

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3. Halodule emarginata den Hartog Blumea 18, p. 65, Fig. 1, 1970 Figures'13--18 H. lilianae den Hartog, Acta Bot. Need. 21, p. 514, Fig. 3, 1972 Rhizomes 0.7--2.0 mm thick, internodes 0.4--4.0 cm long. Leaf-sheath

1.5--3.0 cm long; leaf-blade (3--) 8 (--11) cm long, and (0.8--) 1.2 (--1.5) mm wide, narrowed at the base; midrib widened at the apex; leaf-tip obtuse, emarginate or rounded, slightly spinulose or entire, with 2 inconspicuous lateral teeth, sometimes absent. Staminate flowers with 1.0--2.5 mm long stalk; anthers slender, the lower one ca. 3.5 mm, the upper one ca. 4.0 mm long, coloured by numerous tannin cells. Carpellate flowers with an ovoid or globose ovary, ca. 1.7 mm long, with a lateral style up to 3 cm long. Fruits were not found.

Material studied: BAHIA: Prala Coroa Vermelha, Sta. Cruz Cabralia, col., J.R. Pirani 112, L. Rossi & I. Cordeiro, 28-1-1980 (SPF). ESPIRITO SANTO: Ilha do Boi, 20-XII- 1981 (SPF), col. Oliveira F. RIO DE JANEIRO: Restinga da Marambaia, col. Oliveira F., 28-IX-1977 (SPF). S~O PAULO: Praia de Ara~a, I. de S~o Sebasti~o, col. J.A. Petersen, 15-X-1969 (Type, L); Bairro de S~o Francisco, ~o Sebasti~o, col. Oliveira F. & E.J. Paula 13-XII-1977 (SPF); Praia Barreiro, ]]ha Bela, S~o Sebasti~o, col. Oliveira F. XII- 1977 (SPF); Praia Cabelo Gordo de Dentro, S~o Sebasti~o, col. Oliveira F., 5-XI-1979 (SPF), col. Oliveira F. & E.J. Paula, 21-XI-1979 (SPF), 13-XII-1979 (SPF), col. Oliveira F., 4-I-1980 (SPF), col. F.S. Berchez, 31-I-1980 (SPF), col. Oliveira F., 11-]]-1980 (SPF), 23-IV-1980 (SPF), 20-VII-1980 (SPF), 16-II-1981 (SPF); Praia do Cod6, Ubatuba, col. Oliveira F., 7-IX-1979 (SPF), col. Oliveira F. & E.J. Paula, 21-XI-1979 (SPF), col. Olivei- ra F., 10-VI-1980 (SPF), 10-IX-1980 (SPF), 5-XI-1980 (SPF), col. E. Plastino, 21-XI- 1980 (SPF).

References to Brazil: Bahia: Mar Grande, Ilha de Itaparica, Salvador (den Hartog, 1972, as H. lilianae). S~o Paulo: Praia de Ara~, Ilha de S~o Sebast~o, (Type locality -- den Hartog, 1970b; 1972); Saco da Ribeira, Ubatuba; Siriuba Beach (den Hartog, 1972).

Den Hartog (1972) recognized 3 species of Halodule (H. wrightii, H. emarginata and H. lilianae) from the coasts of Brazil, which are differen- tiated by the leaf-tip morphology. According to him, H. lilianae differs from H. ernarginata by its obtuse leaf-tip, while that of the latter is emar- ginate. However, he points out that both are "very closely related" species, and that "in the future they may turn out to be only forms of one species".

Studying abundant material collected in various seasons of the year, we found that the leaf-tip morphology, as well as the width of the leaves, presents a wide range of variation among populations (Figs. 15 and 16). It seems obvious that we are dealing with only one species when we com- pare the width and apex morphology of the leaves from one single spec- imen (Fig. 14). It also seems that the wider leaves, which also have obtuse leaf-tips, are produced on young shoots. For these reasons, and since both H. emarginata and H. lilianae have been described from sterile material, we have concluded that the last species should be included under H. emar- ginata.

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Typical populations of H. wrightii and H. emarginata can usually be easily recognized. However, in some places such as Praia do Codd (SP) and Restinga da Marambaia (RJ), there are specimens with mixed charac- teristics between the two species, making identification difficult. Perhaps this is a similar situation to the one referred to by Phillips et al. (1974) for H. wrightii from the Gulf of Mexico, wherein the authors interpret the morphological variation as clonal. The usage of leaf-tip morphology and anatomy to separate species of Halodule has been criticized by Phillips (1967) and others. However, as the typical forms are more frequent, and until we know more about their relationship, we preferred to consider both names as distinct taxa.

Halodule emarginata has been collected only along the southeast coast of Brazil, from central Bahia to the northern part of S~o Paulo states (13--23S).

It grows on sheltered shores, on fine sediment substrate, in salinities around 35%o. Several populations are known in the area between Ubatuba and S~o Sebast~o. In this last locality, at Praia do Cabelo Gordo de Dentro, it is the dominant benthic species, extending from extreme LWST to 5 m depth. The population is perennial and its density seems to be related to the grazing pressure of a species of sea-urchin, Lytechinus variegatus (Lamarck). The sea-urchin eats the leaves, but the rhizomes persist, buried in the mud.

Some species of seaweeds are characteristically associated with the pop- ulations of Halodule emarginata, among them, Avrainvillea nigricans Dec., Caulerpa sertularioides (Gruel.) Howe, Acetabularia calyculus Quait & (~alm., A. schenckii Moeb., Rosenvingea sanctae-crucis Boerg. and Hypnea cer- vicornis J. Ag. are noteworthy, growing on the sediment. A large number of animals and algae are found as epiphytes on their leaves, such as Poly- siphonia gorgoniae Harv., Ceramium dawsoni Joly, Goniotrichum alsidii (Zan.) Howe, Fosliella sp. and several species of diatoms.

Specimens with flowers were found only in November (1979) and in January (1980).

4. Halophila decipiens Ostenf. Bat. Tidsskr. 24, p. 260 with fig., 1902 Figures 19--23 Plants monoecious. Rhizome fragile, 0.3--0.6 mm in diameter at each

node with 2 scales, 1 root and a very short erect stem bearing 2 leaves, internodes 1--3 mm long; scales transparent keeled, 3--4 mm long, base amplexicaule. Petiole 4--10 mm long. Leaf-blade oblong--obovate, apex obtuse, cuneate at the base, bright green on both sides with short uni- cellular hairs, 10--25 mm long and 2.5--7.0 mm wide; margin finely serru- late, bracts 2, overlapping, membranous, ovate; acuminate, transparent, 3--4 mm long, keeled, its keel covered with fine serrulate teeth, sparsely hairy on the outside, containing 1 staminate and 1 carpellate flower; the

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bract which encloses the carpellate flower embracing the other one. Stam- inate flower with pedicel 1--2 mm long; tepals oblong--elliptic, obtuse, convex, ca. 1.2 mm long; anthers ca. 1 mm long; after anthesis the complete flower breaks off. Carpellate flower subsessile; ovary ovoid, unilocular, ca. 1 mm long; styles 3, linear, 1.5--2.0 mm long. Fruit globose, 2.5--3.0 mm long., ca. 2.5 mm wide; pericarp membranous, transparent; beak ca. 1 mm long. Seeds numerous, ovoid.

Material studied: RIO GRANDE DO NORTE: Projeto Alga -- SUDENE, dredged at several places around 440'S and 3640'W, at depths varying from 14 to 30 m, 27--29-III- 1980, col. F.R. de Lima (SPF), col. G.C. Teixeira (SPF). PARAIBA: Ponta do Bessa, Jo~o Pessoa, col. F.A.F. Carvalho, 18-II-1977 (SPF). PERNAMBUCO: Pau Amarelo, Paulista, col. Andrade-Lima 56-2529, 14-XI-1956 (IPA, E.S.A.), col. S.M.B. Pereira & Veloso, 19- III-1968 (UFRPe); S'~o Jos~ da Coroa Grande, Barreiros, col. S.M.B. Pereira & Veloso; 26- III-1968 (UFRPe); Praia da Piedade, Jaboa~o, col. S.M.B. Pereira & Veloso, 4-V-1966 (UFRPe); Recife, from 17.5 to 62 m (SPF); Praia do Pilar, ]]ha de ItamaracA, col. Oliveira F., 21-VII-1981 (SPF). BAHIA: Praia Coroa Vermelha, Sta. Cruz Cabr~dia, col. J.R. Pira- ni 113, L. Rossi & I. Cordeiro, 28-I-1980 (SPF); Fundo Grande, Salinas, col. Oliveira F., 15-VII-1981 (SPF). RIO DE JANEIRO: Niter6i, col. D. Marques Lisboa, 31-VIII-1931 (RB, R); Jurujuba, NiterSi, col. R.F. Oliveira 102, 6-II-1965 (R), 23-V-1964 (R).

Additional material studied: PUERTO RICO: BoquerSn, col. M. Dias-Sierra, 19-II-1967 (SPF). VENEZUELA: La Luisa de Morrocoy, Edo Falc6n, col. A.C. Gonzalez 373, 28-VIII-1974 (SPF).

References to Brazil: Paralba. (Laborel-Deguen, 1963). Pernambuco: (Laborel-Deguen, 1963); Ponta de Pedra (den Hartog, 1972). Rio de Janeiro: Niter6i (den Hartog, 1972).

According to den Hartog (1970a), Halophila decipiens "is the only sea- grass that can be considered to be pantropic", being widely distributed in the tropical parts of the Pacific and Indian Oceans and in the Caribbean region. The same author, in 1972, has cited its occurrence at two points on the Atlantic coasts of Brazil.

Den Hartog (1970a) refers to H. decipiens as a sciaphilous species, oc- curring down to a depth of 85 m. We have examined material collected at depths ranging from 0 to 62 m below LWST level. When found among the extensive populations of Halodule wrightii, the species forms very dense, but small, colonies.

5. Halophila baillonii Aschers. in Neumayer Anl. Wiss. Beob. Reisen ed. 1, p. 367, 1875 Figure 24 Plants dioecious. Rhizome rather rigid, 2.0--2.8 mm in diameter, with

1 root at each node; internodes 10--25 mm long; scales at the base of the lateral shoots scarious, apex obtuse. Stem 4--30 mm long, erect, bearing about its median portion 2 obovate, keeled, glabrous, 4--6 mm long scales, and at the tip 4 leaves placed in a pseudo-whorl. Petiole 2--3 mm long. Leaf-blade oblong, ovate or obovate to elliptic; apex obtuse; base cuneate; margin finely serrulate. Flowers and fruits were not seen.

Material studied: PERNAMBUCO: Recife, dredged at 927'50"S and 3517'45"W, depth 31 m (SPF).

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Fig. 24. Halophila ba~Tlonii Aschers., habit.

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References to Brazil: Pernambuco: (Setchell, 1934); strait between Ilha de Itamarac~ and the mainland (den Hartog, 1970a, 1972).

Halophila baillonii is widely distributed in the Caribbean and occurs along the Pacific coast of Panama (den Hartog, 1972). The only reference to this species in Brazil was given by Setchell (1934), based on material

264

collected at Pernambuco state, Ilha de Itamarac~, by G.A. Ramage, in 1888, as referred to by den Hartog (1970a, 1972). The material now col- lected at Recife (Pernambuco) is, therefore, the second record of H. baillonii in Brazil, but it is represented by a single specimen, without either flowers or fruits. Nevertheless, the species is easily recognized and clearly distinct from H. decipiens, and from H. ]ohnsonii Eiseman; this one having been recently described from Florida (Eiseman and McMillan, 1980).

Den Hartog (1970a) refers to Halophila baillonis Aschers. ex Dickie in Hook f., J. Linn. Soc. Bot. 14:317 (1874). However, this name seems to be a nomen nudum, as there is no description or illustration in the given reference. Moreover, the specific epithet is an orthographic error. The name, as Halophila baillonii Ascherson in Neumayer (1875, p. 367), was validly published in accordance with Index Kewensis (1895).

This species seems to be rare at Ilha de Itamarac~ as, although the site has been revisited several times by us, we have had no success in finding more material.

DISCUSSION

With the exception of Ruppia maritima, which tolerates a wider range of temperature and favours brackish waters, the other species seem to be restricted to warmer areas and usually to salinities above 25%0.

Figure 25 shows that the distribution of the species presents discon- tinuities. As it grows only in areas with a particular condition of water movement, salinity, transparency and substrate, the discontinuities could be a reflection of the lack of the right conditions in some stretches of the coast. However, we must admit that some of the gaps in the distribu- tion are due to incomplete survey, and are likely to be covered in the future.

These submerged prairies are very productive (Odum and Odum, 1959), and are the habitat of many animals, including species of economic value that use them as food or shelter. In spite of this, their ecology in Brazil remains largely unknown. With the exception of papers by Cafruni et al. (1978), who consider the distribution of Ruppia maritima at Lagoa dos Patos, and by Laborel-Deguen (1963), who provides information on the distribution of Halodule wrightii and Halophila decipiens on the coasts of Pernambuco and Paraiba, there is hardly any further ecological infor- mation.

The similarity of conditions between the Caribbean region and the trop- ical coast of Brazil, associated with their physical continuity, is certainly responsible for the large affinity between their phycological floras (Oliveira F., 1977). This paper shows that the same is true for the species of Halodule and Halophila occurring in both regions. Halodule beaudettei is considered to be endemic to the Caribbean and Gulf of Mexico, continuing north up to North Carolina (den Hartog, 1970a). However, we found plants in Brazil, here identified as H. wrightii, which could be confused with H. beaudettei.

265

BA

PR f

5C

SP

RJ

."

H. emarginata

, ,.. ..,.,"" .'/

oo" o,

Z: i .." / ; 1/2 - H dec ip iens

R. mar i t ima

Fig. 25. Map showing the distr ibution of seagrasses along the Brazilian coast. - - -, dis- tr ibution according to the literature; , material studied; . . . . , places of possible occurrence.

The similarity of both species had already been noticed by Haynes and Wentz (1975) and Eiseman (1980).

Considering (1) the infrequency of fruits and seeds in the genus Halodule (even unknown in some species); (2) the high potential of vegetative re-

266

production of the rhizomatous habit; and (3) the need of a particular set of conditions for the establishment of these plants, the populations tend to be isolated from each other. This would favor genetic drift, and conse- quently the high morphological variability among different populations. So the existence, in the warmer areas of the American Atlantic, of a species endemic to Brazil (H. emarginata) and one endemic to Bermuda (H. bermudensis den Hartog), both very close to the more widely distributed H. wrightii, could perhaps represent two extremes of morphological varia- tion. It would be interesting to check the relationship of these taxa through approaches such as cultivation under similar conditions, chromosome num- ber and isozymes, such as used by McMiUan and Williams (1980) for species of Halophila.

It is curious that species of Syringodium and Thalassia, that have a gen- eral distribution in the Caribbean area, have not yet been found in Brazil. The actual dispersion of diaspores through coastal waters is certainly limited by the Amazon River. The other genera could have migrated during more favourable conditions prevailing in ancient times. As the sublittoral vege- tation of the coast of Maranh~'o to the northwest is still poorly known, there is a possibility that these plants will be found there in the future.

ACKNOWLEDGEMENTS

Raymond M. Harley kindly corrected the English, and Carolyn J. Bird reviewed the manuscript. This work was partially supported by FAPESP. Final revision and typing was completed at the Atlantic Research Labo- ratory, Halifax, during a cooperative program supported by NRC, Canada, and CNPq, Brazil, to the first author.

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