Rey. Biol. Trop., 39 (1): 41-46, 1991

High levels of gene variation and the population structure of Bunodosoma caissarum (: )

C.A. de Moraes RussoJ.2 and A.M. Solé-Cava2 1 Departamento deGenetica, Instituto de Biologia, Universidade Federal doRío de Janeiro, Bloco A, CCS, Dha do Fundao, 22.000-Río de Janeiro-RJ, Brazil. 2 Departamentode Biologia Geral, Universidade Federal Fluminense. C.P. 100.183,24000 - Niteroi, Río de Janeiro, Brazil.

(Rec. 2O-1V-I990. Acep. 14-IX-I990)

Abstract: High levels of gene variation bave been recently reported for coelenterates and sponges from temperate waters. These levels are supposedly related to tlteir particular life histories,ecolog ical conditions and populationsizes. However, few studies bave beenmade so faron tropical populations. Herewe reportan analysis of 20putative isozyme lociin threepopulations of Bunodosoma caissarum, a Brazilian actiniid anemone extremely abundant in tite intertidal zoneof rocky shores along Río de Janeiro. Heterozygosity levels were high (between 0.284 and 0.299),as in tite anemones fromtite tem­ perate zone. This suggests tbatlatitude-related variables are not necessary conditions for high heterozygosity levels. A low level of gene differentiation (1 = 0.954) was observed between populations up to 200 km apart, indicating a high homogeneity for the population. Theevolutionary age of tite groupand tite high population sizes presentin these organisms may be respon­ sible for the high levels of gene polymorphism observed in tlteirpopulations.

Key words: Actiniaria,heterozygosity, Bunodosoma, genetics, population

The Brazilian endemic sea-anemone species help to clarifying problems in Bunodosoma caissarum Correa, 1964 is widely (Carter & Thorpe 1981, Haylor et al. 19840, distributed along the Sao Paulo and Rio de Solé-Cava & Thorpe 1987) and reproductive Janeiro coasts (Correa 1976, Maggs et al. 1979, biology (Orr et al. 1982). Populations of Gouvea et al. 1985, 1989). B. caissarum is an Actinia show a moderately high level of gene exclusively sexually reproduciog actiniid ane­ variation (Solé-Cava & Thorpe 1987, 1989), mone (M.J. Belem, personal communication, and a high differentiation between allopatric 1989) which.is particularly abundant io pollu­ populations (Solé-Cava 1986). Similar results ted waters where it can reach population densi­ were obtained for anemones of the genus ties of up to 150 individuals/square meter (un­ Sargatia (Shaw et al. 1987). On the other hand, published results). Because of its abundance, low levels of gene differentiation were obser­ this·anemone has been used for the e�traction ved within sub-tropical Bunodosoma of biologically active compounds (Kelecom et (McCommas & Lester 1980), and temperate al. 1982), and as a radioactivity biomonitor Metridium (Bucklin & Hedgecock 1982), (Gouvea et al. 1985, 1989). However, the po­ Anthopleura (Smith & Potts 1987), and pulation dynamics and genetics of this ecologi­ Urticina (Solé-Cava et al. 1985) species. The cally important sea-anemone are still unknown. contrast between the population strUctures in The genetic study of coelenterate popula­ those anemone species could be related to dis­ tions has given a better iosigbt ioto their eco­ persal capabilities and �e balance between se­ logy, systematics, and reproductive biology. In xual and asexual reproduction. . Actinia equina, an European species ecologi­ The aim of this work was to estimate the ba­ calIy similar to Bunodosoma caissarum, for sic genetic parameters of three populations of éxample, population genetics has been used to Bunodosoma caissarum and relate them to those 42 REVISTADE BIOLOOIA TROPICAL

reported for coelenterates from temperate wa­ for carotenoproteins in Urticina felina (Solé­ terso Cava et al. 1985), which also belongs to the Actiniidae. CarQtenoproteins are common in MATERIAL ANDMETHODS marine invertebrates (Cheesman et al. 1967) and carotenoids have been described for Samples (approx. 30 in each site) of Bunodosoma granulifera (Leboef et al. Bunodosoma caissarum were collected in the 1981a,b). The polymorphic cathodic bands oh­ intertidal zone of two sites in Guanabara Bay served in B. caissarum were thus interpreted as . (Urca 22°47'S; 43°1O'W, and Bananal 22°57'S, the expression of a di-allelic locus codifying 43°1O'W, State of Río de Janeiro) and one site for a monomeric carotenoprotein. Further stu­ outside the bay (Forno ·Beach, 22°58'S; dies on this putative carotenoprotein are neces­ 42001'W). The anemones were transported in sary. ice to the laboratory, where they werekept at The gene frequencies of the 20 loci analyzed -20 "C until electrophoresis. All samples were are presented in Table 1. From the total of 47 analyzed within one month after the collection. loci studied, three (Pgm-Arraial, Pgd-Urca and The samples were homogenized using a Sod.l-Arraial) exhibited significant (chi-squa­ glass rod on an acrylic plate, with a maximum red test, 0.01

TABLEl

Genefrequenciesfor20 proteinloci of Bunodosomacaissarumfrom in 31ocations RiD deJaneiro. n - numberof alleles sampledfor each locus. Ho and He - Observedand Hardy-Weinberg expecfed (unbitued estimare.Nei 1978) heterozyg08itylevelsfor each sample

LOCU8 ALLELES URCA n ILHA n ARRAiAL n

1.000 Acp 1 10 � 0.870 46 0.857 56 2 0.000 0.130 0.148

BluPtn 1 0.464 56 0.389 36 2 0.536 0.611

Cat 1 0.063 16 0.361 36 0.167 12 2 0.625 0.444 0.500 3 0.313 0.194 0.333

D-Est 1 0.976 42 0.971 34 1.000 46 2 0.024 0.029 0.000

Gdh 1 0.300 40 0.139 36 0.167 12 2 0.700 0.806 0.750 3 0.000 0.OS6 0.083

Got 1 0.083 24 0.000 28 0.083 12 2 0.667 0.429 0.2S0 3 0.2S0 0.571 0.667

Hbdh 1.000 26

HIt-1 1 0.071 28 0.000 10 2 0.357 0.300 3 0.571 0.700

HIt-2 1 0.857 28 1.000 10 2 0.143 0.000

Lap 1 0.130 46 0.022 46 2 0.696 0.848 3 0.087 0.022 4 0.087 0.109

Mdh-l 1 0.889 36 1.000 36 1.000 10 2 0.111 0.000 0.000

Mdh-2 1 0.000 36 0.083 12 2 0.944 0.833 3 0.056 0.083

Me 1 0.933 30 2 0.067

Mpi 1 0.071 28 0.200 10 2 0.321 0.300 3 0.000 0.100 4 0.357 0.400 5 0.214 0.000 6 0.036 0.000

Pep 1 0.200 30 2 0.800

Pgd 1 0.237 38 0.417 36 0.000 10 2 0.579 0.528 0.900 3 0.184 0.OS6 0.100

Pgi-I 1 0.425 40 0.200 10 2 0.575 0.800

Pgm 1 0.200 10 0.000q. 36 0.054 56 2 0.800 0.694 0.714 3 0.000 0.083 0.125 4 0.000 0.222 0.127

8od-1 1 1.000 10 1.000 38 0.929 56 2 0.000 0.000 0,071

Sod-2 1 0.020 SO 0.000 38 0.036 S6 2 0.980 1.000 0.964

Ro 0.290 0.299 0.284 He 0.289 0.294 0.266 44 REVISTA DE BIOLOGIATROPICAL

TABLE2 the stability of the effective population size th­ rough geological time, or from the lower level Gene ldentity (abovethe diagonal - Nei 1972j amisimila­ rity (below the diagonal- Thorpe 1979) indices between of homoeostaticcapability that these organisms the threepopulations of Bunodosomacaissarum studied might present. Bunodosoma caissarum exhibits large popu­ REGION URCA aHA ARRAIAL lation sizes, being particularly abundant in po­ lluted places (Gouvea et al. 1985, 1989, perso­ URCA 0.960 0.954 tíal observations). This might be helped by the ILHA 0.847 0.969 ARRAIAL 0.840 0.874 high resistance of these anemones to anoxia (Ellington1982) and to osmotic stress(Howard their populations (Francis 1979, Shick et al. et al. 1987). It has been suggested that, in ma­ 1979, Bucklin 1987, Smith & Potts 1987). rine polluted areas, high levels of genetic varia­ Although the asexual mode of reproduction do­ tion can be adaptive (Nevo et al. 1984). It es not produce, per se, any change in the ge­ would be tempting, thus, to try to relate the notypicproportions of the population, it enhan- high abundance of Bunodosoma in polluted . ces any disturbances caused by selection (e.g. places to adaptation through high levels of he­ Shick et al. 1979) or by genetic drift (e.g. Black terozygosity in its populations. However, the & Johnson 1979). relationship between levels of pollution and ge­ The very high levels of gene identity found netic variation has not been confIrmed, at least between samples up to 180 km apart of in some benthic organisms (Fevolden & Garner Bunodosoma caissarum indicate thatthese ane­ 1986), and, thus, altemative explanations based mones must have high dispersal (or low diver­ solely on high population sizes (Kimura 1983) gence) rates. Adult and gamete dispersal are cannot be excluded. Interestingly, thetwo ge­ unlikely to be important along large geographi­ netically most polymorphic sea-anemone gene­ cal distances in sea anemones. The larvae of ra, Anthopleura and Urticina (Smith & Potts B. caissarum are still unknown but they are 1987, Solé-Cava et al. 1985) are also very possibly long-lived, since the suitable substrata abundant where they occur. Selectionist and for this species are not continuous along the neutralist factors could thus be equally evoked Río de Janeiro coast. to explain the results observed in B. caissa­ The high levels of gene variation found in rumo It is not unlikelythat a bi-directional inte­ Bunodosoma caissarum are comparable lo tho­ raction exists between genome and environ­ se found in other sea-anemone species ment, and that drift and selection probably pla­ (McCommas 1982; Bucklin 1985; Solé-Cava & yed different roles during the evolution of each Thorpe 1987, 1989; Shaw et al. 1987; Smith & group of organisms (Wright 1978, Levins & Potts 1987). The high heterozygosity levels ge­ Lewontin 1985). nerally observed in marine organisms have be­ en often associated with ecological (Selander & ACKNOWLEDGEMENTS Kaufman 1973, Karlin & Levikson 1974, Valentine & Ayala 1974, Solé-Cava 1986) or The authors thank R. Borojevic, A. random stochastic phenomena (Johnson & Kelecom, L.B. Klaczko and M. Ward for co­ Black 1982, 1984, Kimura 1983, Solé-Cava rrections to the manuscript. M. Klautau and 1986). High levels of gene variation have also E.P. da Silva provided invaluable help in the been related to the antiquity or conservative­ electrophoresis and in the collection of sam­ ness (Soule 1972, Gorman & Kim 1977) of or­ pIes. This work was supported by grants ganisms. Coelenterates are usually considered 802132-87.1 and 406672-87.3 from the "primitive" due to their apparent structural Brazilian National Research Council (CNPq), simplicity. The reasons for the primitivenes­ and is part of a Master of Sciences dissertation s/heterozygosity relationship, however, are far by C.A.M. Russo at Departamento de Genética, from clear, since it may be explained both by UFRJ. RUSSO & SOLE: Gene variationand population of Bunodosoma 45

RESUMEN Carter, M.A. & J.P. Thorpe. 1981. Reproductive, genetic and ecological evidence that Actinia equina varo m e­ sembryanthemumand varofragacea are noteonspecific. Recientemente se ha informado sobre altos J. Mar.Bio!. Assoc. U.K. 61: 79-83. niveles de variación génetica en celenterados y esponjas de aguas templadas. Se presume que Cheesman, D.F., W.L. Lee. & P.F. Zagalsky. 1967. Carotenoproteins in invertebrates. Biol. Rev. 42: 132- tales niveles se relacionan con sus modos de vi­ 160. da, condiciones ecológicas y tamaños de pobla­ ción. Sin embargo, se sabe muy poco sobre las Correa, D.D. 1976. The present situation of the taxonomi­ cal study of Brazilian seaanemones. Anais Acad. Bras. poblaciones de anémonasmarinas tropicales. Cienc. 47: 143-144. Aquí se analizan 20 supuestos loci isoenzi­ máticos en tres poblaciones de Bunodosoma Ellington, W.R. 1982. Metabolic responses oC the sea ane­ mone Bunodosoma cavernata (Bose) lO declining oxy­ caissarum, una anémonaactinida del Brasil que gen tensions andanoxia. Physiol. Z001. 55: 240-249. es muy abundante en la franja intramareal de las costas rocosas de Río de Janeiro. Los nive­ Fevolden, S.E. & S.P. Gamer.1986. Population genetics of Mytilus edulis (L.) from Oslofjorden, Norway, in oil­ les de heterocigosis son altos (0.284-0.299), al pollutedand non oil-polluted water. Sarsia 71: 247-257. igual que ocurre en especies de zonas templa­ das. Esto sugiere que los factores dependientes Francis, L. 1979. Contrastbetween solitary and clonal Ií­ de la latitud no son indispensables para los al­ festyles in the sea anemone Anthopleura elegantissi­ ma. Amer. Zool. 19: 669-681. tos niveles de heterocigosis. Se observó un ni­ vel bajo de diferenciación génica (1 = 0.954) Gorman, G.C. & Y.J. Kim. 1977. Genotypic evolution in entre poblaciones separadaspor hasta 200 km, fue face of phenotypíc eonservativeness. Abudefduf (pomaeentridae) from the Atlantic and Pacific sides of lo que indica una alta homogeneidad poblacio­ Panarna.Copeia 1977: 694-697. nal. La edad evolutiva del grupo y las grandes poblaciones de esta especie son causas facti­ Gouvea, R.C., P.L. Santos. & V.A. Gouvea. 1985. Contaminaeao radiativa de Bunodosoma caissaru m tan bles para altos niveles de polimorfismo gé­ Correa, 1964 (Cnidarla, Actinidae) sob condieoes con­ nico. troladas.Rev. Bras. Biol. 42: 101-104.

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