Cnidae of the Brazilian Mussidae (Cnidaria: Scleractinia) and Their Value in Taxonomy

BULLETIN OF MARINE SCIENCE, 51(2): 231-244, L 992 CORAL REEF PAPER

CNIDAE OF THE BRAZILIAN MUSSIDAE (CNIDARIA: SCLERACTINIA) AND THEIR VALUE IN TAXONOMY

Debora 0. Pires and Fabio B, Pitombo

ABSTRACT The cnidae of four species of Mussidae are described and illustrated, Both Weill's (1934) nematocyst nomenclature, later modified by Carlgren (1940), and Schmidt's (1969; 1972; 1974) were used, Three species belonging to the endemic Brazilian genus Mussismilia Ort- mann, 1890, M. hispida (Verrill, 1902), M. hartti (Verrill, 1868) and M. braziliensis (Verrill, 1868), and one belonging to the world wide genus Scolymia Haime, 1852, S. wellsi Laborel, 1967, were studied. Specimens from different localities of the Brazilian coast were observed, Qualitative analysis of their cnidae showed that all the species studied present the same types and distributions of nematocysts, Five types were observed (sensu Schmidt): spirocysts, holotrichs I, holotrichs II, b-rhabdoids, and p-rhabdoids D. Some types presented morphological varieties considered as sub-types. Four structural regions were examined: coenosarc/ edge zone, acrospheres, stomodaeum and mesenterial filaments. The nematocysts of a planula of S. wel/si were also observed. Qualitative and quantitative size analysis of cnidae showed differences at generic level only. The qualitative difference observed was that Mussismilia presents two size classes of p-rhabdoids D in the mesenterial filamcnts, while in Scolymia there is only one. Quantitative size analysis was performed using nested analysis ofvariancc (ANOV A) and the procedure ofStudent-Newman-Keuls (Sokal and Rohlf, 1979). These tests suggested that the size of three types of nematoeysts ean differentiate the two genera: b-rhabdoids from stomodaeum and holotrichs I and II from the mesenterial filaments. The importance of morphometries in the study of eoral cnidae is supported.

Different types of nematocysts generally have been considered as one of the useful characters in the taxonomy of different orders of Cnidaria (Weill, 1934; Tischbierek, 1936; Papenfuss, 1936; Russell, 1938; 1939; 1940; Carlgren, 1940; 1945; 1949; Hand, 1961; Werner, 1965; Schmidt, 1972; 1974). There has been significant development of knowledge of nematocysts of some groups. Calder (1971; 1974; 1975; 1977; 1983) has examined the cnidom in many species of Scyphozoa and used the differences in their cnidae to distinguish them. The nematocysts of Hydrozoa have also been examined in detail and many studies emphasized their utility in taxonomy (Ostman, 1979a; 1979b; 1982; 1983; 1987; 1988; Bouillon, 1985; .Watson, 1985; Cornelius and Ostman, 1987; Gravier- Bonnet, 1987 and others). In Actiniaria the study of the nematocysts is at a more advanced stage, as the procedure of giving data on the cnidae distributions and sizes of nematocysts has become conventional in actinian taxonomy (Fautin, 1988). However, in Scleractinia non-skeletal features have figured in the characteriza- tion of only a few species (Lang, 1984) and classical taxonomy has been based primarily on skeletal morphology. Matthai (1914; 1928) was one of the earliest researchers to establish the presence of different types of nematocysts in corals. He used them in the identification of some species. Several other papers mentioned coral nematocysts and suggested their use in systematics (although with very different treatments) (Weill, 1934; Abe, 1938; Best, 1968; Schmidt, 1972; 1974; Wafar, 1974; Den Hartog, 1980; Song, 1988; 1991). Developmental studies of sweeper tentacles of some coral species have contributed to the knowledge of nematocyst types occurring in these structures (Den Hartog, 1977; Hidaka and Miyazaki, 1984; Hidaka and Yamazoto, 1984; Hidaka et aI., 1987). Nematocysts

231 232 BULLETIN OF MARINE SCIENCE, VOL. 5], NO.2, 1992

of some corals were also well reported by Thomason and Brown (1986). They studied the cnidom of 10 Indo-Pacific and Caribbean corals to explain their relative aggressive proficiencies. There are reports of successful identification of coral species using the cnidom alone (Thomason 1986a; 1986b; Tilbury and Cameron, 1989). Here we describe the nematocysts of the Brazilian species of the family Mussidae Ortmann, 1890, previously identified only by skeletal morphology. We also ver- ified qualitative and quantitative analysis of cnidae as a possible instrument to the systematic study of the group. The three species belonging to the Brazilian endemic genus Mussismilia Ort- mann, 1890: M. hispida (Verrill, 1902), M. hartti (Verrill, 1868) and M. braziliensis (Verrill, 1868), and one belonging to the world wide distributed genus Scolymia Haime, 1852, S. wellsi LaboreI, 1967, were studied. According to Laborel (1969), M. hispida is divisible into two geographical subspecies: M. hispida hispida (from the State of Bahia to Sao Sebastiao, Sao Paulo) and M. hispida tenuisepta (to the north of the Sao Francisco River outlet) (Fig. 1).

MATERIALS AND METHODS

The material studied is deposited in the Cnidaria Collection of the Museu Nacional (Col. enid. MN), Rio de Janeiro. Codes indicated in parentheses after collection number refer to studied polyps as described in the results. All the specimens were collected by Fabio Bettini Pitombo in the following localities (Fig. I): M. hispida.-Arquipelago dos Abrolhos, BA, 05/Apr/89, n. al711 (Mhil.l and Mhi 1.2); Porto de Galinhas, PE, 06/Mar/90, n. 01718 (Mhi2); Ilha Grande, RJ, 31/ Apr/90, n. 01719 (Mhi3). M. hartti.-Arquipelago dos Abrolhos, BA, 04/Apr/89, n. 01707 (Mhal.l and Mha1.2) and 05/ Apr/89, n. 01709 (Mha2); Morro de Sao Paulo, BA, 14/Mar/90, n. 01746 (Mha3). M. brazi/iensis.- Arquipelago dos Abrolhos, BA, 03/Apr/89, n. 01704 (Mbl.l and Mb1.2) and 05/Apr/89, n. 01717 (Mb3); Morro de Sao Paulo, BA, 14/Mar/90, n. 01710 (Mb2). S. we/lsi.-Arquipelago dos Abrolhos, BA, 06/Apr/89, n. 01713 (Swl), 01714 (Sw3) and 01716 (Sw2); Parcel dos Abrolhos, BA, 08/0ct/87, n. 01198 (Sw4). The material was collected by snorkel and SCUBA diving at depths from 2 to 17 m. Specimens

were anaesthetized in the dark, using a I: I solution of 8.0% MgCI2 and sea water. They were fixed in Susa of Heidenhain (Pantin, 1948) or 4% formalin, and stored in 4% formalin. For the identification of skeletal characters, part of each colony of Mussisrni/ia species and single polyps of S. wellsi were bleached with I: I sodium hypochlorite solution. Colonies of M. hispida were maintained alive in the laboratory for observation of discharged nematocysts. Illustrations of discharged nematocysts were prepared for this species only. It is the only one occurring near our laboratory (i.e., in the same State). Decalcification of the skeleton was obtained using a solution of 10% formic acid and 5% formalin (J. Thomason, pers. comm.). Nematocysts were examined in squash preparations of small portions oftissue from different structures of living and preserved polyps. The identification and measurements of the different types were made under phase contrast microscopy (1,250x), with an eyepiece micrometer. The measurements of length and width were taken at random from undischarged capsules. Measurements were made on every nematocyst type in each structure (edge zone/coenosarc, acrospheres, stomodaeum and mesenterial filaments) for each species. Coefficient of variation was used to test the preciseness of mea- surement techniques (Heller, 1968). For all species each nematocyst type was illustrated using camera lucida. A whole mount of planula of S. we/lsi was also prepared. Both Weill's (1934) nematocyst nomenclature, later modified by Carlgren (1940), and Schmidt's (1969; 1972; 1974) were used, The quantitative study (using capsule lengths only) was done using the nested analysis of variance (ANOV A) and the procedure of Student-Newman-Keuls (SNK) (Sokal and Rohlf, 1979). The former demonstrated the occurrence of significantly different means and the latter determined which means differed. A significance level of P < 0.05 was used for the statistical tests. This study was executed in two steps. FIRST STEP.- This stage was done as a first evaluation. It allowed the elimination, in the next analysis, of nematocyst types that did not present significantly different means at least in one species. In the first step two polyps from one specimen of each of the three species of Mussisrnilia and from two specimens of Scolyrnia, all from the same locality (Arquipelago dos Abrolhos), were used. Twenty nematocysts of each type were measured per polyp. PIRESANDPITOMBO:CNlDAEOFBRAZILIANCORALS 233

1 BRAZIL

~4 ATLANTIC OCEAN

Figure 1. Map showing collecting sites of specimens; numbers indicate localities: I-Porto de Gal- inhas, Pernambuco; 2-Morro de Sao Paulo, Bahia; 3-Abrolhos area, Bahia; 4-I1ha Grande, Rio de Janeiro; • Sao Francisco River.

There were two possible results for each nematocyst type from each structure: A-Means were not significantly different among the four species studied. B-Means were significantly different, at least in one of the studied species. Only types that gave result B were subjected to the second step of analysis. SECONDSTEP.-Another analysis of variance was performed for each nematocyst type. Other specimens of the same and different localities were added to improve the analysis. From the data used in the first step (N = 20), the required sample size "n" was found (Southwood, 1978: 21). The data obtained in the first step from each of two polyps from the same specimen were chosen randomly, up to the new sample size (N = 10).

Table I. Nematocyst categories observed in the species studied

sensu Weill, 1934, modified by Carlgren, 1940 sensu S<:hmidt, 1969, 1972, 1974 holotrichs isorhizas holotrichs I homotrichs anisorhizas (?) holotrichs II (?) micro basic b-mastigophores b-rhabdoids micro basic p-mastigophores p-rhabdoids 0 234 BULLETIN OF MARINE SCIENCE, VOL. 51, NO.2, 1992

Table 2. Distribution and size of cnidae. A = Mussisrnilia hispida; B = M. hartti; C = M. braziliensis; D = Scolyrnia wellsi; SP = species; x = mean; SD = standard deviation; R = range; NT = total number of capsules measured; NP = number of polyps observed. All measurements are in ~m

Length Width Structure Cnida type Sp x SD (R) x SD (R) NT NP Fig Coenosarc spirocysts A 23.2 5.0 (18-50) 3.5 0.7 (2-5) 40 2 3A B 17.6 2.6 (12-23) 3.0 0.5 (2-4) 40 2 4A C 18.8 1.8 (15-24) 3.2 0.5 (2-4) 40 2 5A D 18.4 2.1 (15-23) 3.8 0.6 (3-5) 40 2 6A p-rhabdoids D(3) A 18.6 1.6 (16-24) 4.3 0.7 (2-6) 40 2 3B B 20.3 2.7 (15-27) 4.2 0.7 (3-6) 40 2 4B C 18.9 2.1 (15-23) 4.3 0.8 (3-6) 40 2 5B D 17.4 2.1 (14-23) 5.4 0.7 (4-7) 40 2 6B Acrospheres spirocysts A 42.9 7.7 (22-58) 4.0 0.8 (2-6) 40 2 3C B 31.0 8.7 (18-45) 3.7 0.6 (2-5) 40 2 4C C 31.7 6.5 (18-46) 3.2 0.7 (2-4) 40 2 5C D 33.8 9.0 (21-53) 3.3 0.8 (2-5) 40 2 6C b-rhabdoids (I) A 29.2 2.4 (20-43) 3.2 0.8 (2-5) 40 2 3D B 31.8 3.4 (26-44) 3.6 0.6 (2-5) 40 2 4D C 25.8 3.8 (18-33) 2.7 0.6 (2-4) 40 2 5D D 27.6 3.5 (21-35) 3.6 0.7 (3-5) 40 2 6D p-rhabdoids D(I) A 57.2 5.6 (45-68) 5.3 0.6 (4-7) 60 4 3E B 44.0 4.0 (44-64) 5.6 0.6 (4-7) 60 4 4E C 51.3 4.2 (44-60) 4.8 0.6 (4-6) 60 4 5E D 59.0 5.2 (50-70) 6.0 0.7 (4-7) 60 4 6E Stomodaeum holotrichs I A 53.8 3.7 (48-62) 12.8 1.4 (8-16) 40 2 3F B 48.9 3.3 (40-54) 12.6 1.4 (10-16) 40 2 4F C 46.2 3.1 (39-53) 11.8 1.7 (10-16) 40 2 5F D 57.1 4.5 (50-68) 16.0 2.1 (10-20) 40 2 6F b-rhabdoids (I) A 27.5 3.5 (21-36) 3.7 0.6 (2-5) 60 4 3G B 27.3 2.4 (20-32) 3.6 0.6 (3-6) 60 4 4G C 24.0 3.1 (18-35) 3.5 0.5 (3-5) 60 4 5G D 32.4 3.5 (22-43) 4.7 0.6 (4-6) 60 4 6G Filaments spirocysts A 27.5 7.9 (14-32) 3.0 1.0 (2-5) 60 2 3H B 23.6 7.2 (16-38) 3.1 0.9 (2-5) 12 2 4H C 18.9 1.4 (18-22) 3.0 0.2 (3-4) 17 2 5H D 24.3 4.9 (17-36) 3.9 0.2 (3-4) 17 2 6H holotrichs I A 44.0 2.8 (38-50) 11.3 1.3 (9-14) 40 2 31 (small) B 39.8 4.9 (31-54) 10.4 1.0 (8-13) 40 2 41 C 38.7 4.3 (28-48) 10.5 1.2 (8-14) 28 2 51 D 51.4 4.2 (43-58) 14.8 2.0 (11-20) 19 2 61 holotrichs I A 80.6 10.3 (56-96) 13.1 1.4 (9-16) 60 4 31 (large) B 73.2 3.1 (66-79) 13.6 1.7 (8-18) 60 4 41 C 63.5 4.1 (44-72) 12.9 1.4 (10-16) 60 4 51 D 115 7.2 (100-134) 18.6 2.2 (12-24) 60 4 61 holotrichs II A 11.6 l.l (9-14) 3.0 0.5 (2-4) 60 4 3K B 12.3 0.9 (10-14) 3.3 0.5 (2-4) 60 4 4K C 12.0 1.0 (9-15) 3.3 0.6 (3-5) 60 4 5K D 18.3 1.7 (15-23) 4.6 0.7 (3-6) 60 4 6K b-rhabdoids (2) A 9.2 1.2 (6-12) 2.1 0.3 (2-3) 40 2 3L B 9.6 0.9 (7-11) 2.1 0.3 (2-3) 40 2 4L C 10.0 0.8 (8-13) 2.0 2.0 (2-2) 40 2 5L D 9.7 1.6 (7-14) 2.2 0.4 (2-3) 40 2 6L PIRES AND PITOMBO: CNIDAE OF BRAZILIAN CORALS 235

Table 2. Continued

Length Width Structure enida type Sp it SO (R) SO (R) NT NP Fig

p-rhabdoids D(2) A 28.4 1.9 (24-32) 6.1 0.3 (6-7) 40 2 3M (small) B 26.8 2.1 (22-33) 5.8 0.5 (5-7) 40 2 4M C 29.6 1.6 (27-34) 5.6 0.6 (4-7) 40 2 5M D* 37.2 6.0 (30-53) 7.5 1.4 (5-11) 60 4 6M p-rhabdoids D(2) A 57.8 4.4 (49-60) 8.0 1.0 (6-12) 60 4 3N (large) B 49.7 4.1 (38-58) 7.4 0.3 (6-9) 60 4 4N C 53.0 4.2 (43-62) 7.0 0.8 (6-9) 60 4 5N p-rhabdoids D(3) A 19.6 2.6 (14-24) 5.0 0.7 (4-6) 40 2 30 B 18.7 1.8 (15-25) 4.6 0.7 (4-6) 40 2 40 C 19.4 2.3 (15-20) 4.3 0.8 (3-6) 40 2 50 D 19.8 2.0 (15-24) 5.8 0.4 (5-7) 40 2 6N

• S. wells; actually presents only one size class ofp.rhabdoids 0(2) in the mensenterial filaments, intennediate between the two occurring in the Mussismi/ia species. It was included in the small class, for convenience.

REsULTS Qualitative Results. -Spirocysts and four types of nematocysts were recorded in all species studied (Tables 1, 2; Figs. 3-6). In the proximal part of the tentacles of all studied species there are only spirocysts. This type was common in the polyps of all specimens observed. They are constant in the tentacles and coenosarc and in some specimens may be present also in the stomodaeum and filaments (Table 2). Spirocysts were not included in the statistical analysis due to their variable sizes.

60 en ~ :z::: C) 50 z UJ ...J 40 « c z 30 U

A B c o Figure 2. Length ofp-rhabdoids D(2) from mesenterial filaments; A = Mussismilia hispida; B = M. hartti; C = M. braziliensis; D = S. wellsi. Narrow bars = range; wide bars = standard deviation. Measurements are in ~m. 236 BULLETIN OF MARINE SCIENCE, VOL. 51, NO, 2,1992

G c

J '·'t .., . ':1 ",,' 11"'1 1,.:::~

J N

Figure 3, Cnidae of Mussismi/ia hispida: A, B coenosarc; C-E acrospheres; F, G stomodaeum; H- o mesenterial filaments. A, C, H-spirocysts; B, O-p-rhabdoids D(3); D, G-b-rhabdoids (I); E- p-rhabdoids D(I); F, I, J-holotrichs I; K-holotrichs II (?); L-b-rhabdoids (2); M, N -p-rhabdoids D(2). PIRES AND PITOMBO: CNIDAE OF BRAZILIAN CORALS 237

A G c D

H M Figure 4. Cnidae of Mussisrnilia hartti: A, B coenosarc; C-E acrospheres; F, G stomodaeum; H-O mesenterial filaments. A, C, H-spirocysts; B, O-p-rhabdoids D(3); D, G-b-rhabdoids (I); E- p-rhabdoids D(I); F, I, J -holotrichs I; K-holotrichs II (?); L-b-rhabdoids (2); M, N -p-rhabdoids D(2).

Two distinct size classes of holotrichs I were observed in the mesenterial filaments of all studied species (Table 2; Figs. 31, J; 41, J; 51, J; 61, n. These size classes were significantly different. The smaller one was seldom observed. A sat- isfactory sample size to include it in the quantitative analysis was not obtained. In this study, we were unable to confirm if the holotrichs II observed actually belong to this category, because of the optical resources utilized. It is small (9- 23 ~m), slightly translucent, and difficult to make discharge (Figs. 3K, 4K, SK, 6K). We noticed some varieties of b-rhabdoids and p-rhabdoids D as undischarged capsules. The following varieties are constant and occur in the four species studied. B-rhabdoids: (1) Relatively large capsules, many dense turns of spines (Figs. 3D, G; 4D, G; 5D, G; 6D, G); (2) Very small capsules, few obvious turns of spines (Figs. 3L, 4L, 5L, 6L). Both with very distinct shafts. P-rhabdoids D: (1) Shaft with obvious turns of spines-less than ]13 of capsule length, relatively large capsules [compared to (3)], capsule wall normal (Figs. 3E, 4E, 5E, 6E); (2) Shaft with obvious turns of spines- 1/2 of capsule length, relatively small [compared to (1)] or large capsules [compared to (3)], capsule wall normal (Figs. 3M, N; 4M, N; SM, N; 6M); (3) Thin shaft [compared to (1) and (2)]-112 of capsule length, relatively small capsules [compared to (1)], thin walled, almost transparent (Figs. 30, 40, 50, 6N). The p-rhabdoids D(2) are present in the mesenterial filaments in two signifi- 238 BULLETIN OF MARINE SCIENCE, VOL. 5 I, NO.2, 1992

o c

Figure 5. Cnidae of Mussismilia braziliensis: A, B coenosarc; C-E acrospheres; F, G stomodaeum; H-O mesenterial filaments, A, C, H-spirocysts; B, O-p-rhabdoids D(3); D, G-b-rhabdoids (I); E-p-rhabdoids D(l); F, I, J-holotrichs I; K-holotrichs II (?); L-b-rhabdoids (2); M, N -p-rhabdoids D(2). cantly different size classes in the three species of Mussismilia (Table 2; Figs. 2; 3M, N; 4M, N; 5M, N) and as only one in S. wellsi (Table 2; Figs. 2; 6M). Rounded shape p-rhabdoids D(3) occur occasionally in the stomodaeum of S. wellsi. In Mussismilia species they are rare in this structure and the capsules present one tapering tip, exactly like those from the filaments. This similarity and small quantity observed suggested to us possible contamination. No significant differences were observed between the cnidae of the two subspecies of M. hispida suggested by Laborel (1969). Both present the same distribution of types and there are no significant differences among their sizes. Discharged nematocysts were observed and illustrated only from M. hispida hispida (Fig. 3). Apparently there is no variation among the types of the other species studied, since in undischarged condition they present the same structural details as observed in M. hispida. Spirocysts, holotrichs I, b-rhabdoids (1) and p-rhabdoids D(2) were observed in the planula of S. wellsi. Except for the holotrichs I, that are smaller, the cnidae are similar in size to those of adult specimens.

Quantitative Size Analysis. - FIRSTSTEP.- The following nematocysts types showed result A-means were not significantly different-b-rhabdoids (1) from acrospheres (Table 3); p-rhabdoids D(3) from coenosarc (Table 3); and b-rhabdoids PIRES AND PITOMBO: CNIDAE OF BRAZILIAN CORALS 239

o c

Figure 6. Cnidae of Scolymia wellsi; A, B coenosarc; C-E acrospheres; F, G stomodaeum; H-N mesenterial filaments. A, C, H-spiroeysts; B, N-p-rhabdoids 0(3); 0, G-b-rhabdoids (I); E- p-rhabdoids 0(1); F, I, J-holotrichs I; K-holotrichs II (?); M-p-rhabdoids 0(2).

(2), p-rhabdoids D(2) (small) and p-rhabdoids D(3) from mesenterial filaments (Table 3). The following nematocyst types presented the result B- means were significantly different-p-rhabdoids D(1) from acrospheres-separated M. braziliensis from the other species studied (Tables 3, 4); b-rhabdoids (1) from stomodaeum-sep-

Table 3. Summary table of F values among species in the nested analysis of variance (first step) for capsule length of cnida types of Mussismilia hispida. M. hart/i. M. braziliensis and Scolymia wellsi

Structure Cnida type Among species Coenosarc p-rhabdoids 0(3) F[3,4] = 9.98 F= 2.]5 Acrospheres b-rhabdoids (]) F[3,4] = 9.98 F = 1.07 Acrospheres p-rhabdoids D(]) F[3,4] = 9.98 F = 13.65* Stomodaeum b-rhabdoids (I) F[3,4] = 9.98 F = 2]8.67* Stomodaeum holotrichs I F[3,4] = 9.98 F = 100.62* Filaments b-rhabdoids (2) F[3,4] = 9.98 F = 1.48 Filaments p-rhabdoids 0(2) small F[2,3] = 16.0 F = 1.68 Filaments p-rhabdoids 0(3) F[3,4] = 9.98 F= 0.84 Filaments holotrichs I large F[3,4] = 9.98 F = 106.78* Filaments holotrichs II F[3,4] = 9.98 F = 166.50* Fi]aments p-rhabdoids 0(2) large F[2,3] = 16.0 F = 16.68*

• Slatistically significanl (P < 0.05). 240 BULLETIN OF MARINE SCIENCE, VOL. 51, NO.2, 1992

Table 4. Student-Newman-Keuls Procedure ofcnida types with significantly different means among species in the nested analysis of variance (first step). Mhi 1.1 = M. hispida colony I polyp I; Mhi 1.2 = M. hispida colony I polyp 2; Mha 1.1 = M. hartti colony I polyp I; Mha 1.2 = M. hartti colony I polyp 2; Mb 1.1 = M. braziliensis colony I polyp I; Mb 1.2 = M. braziliensis colony I polyp 2; Sw I = S. wellsi specimen I; Sw2 = S. wellsi specimen 2

Acrospheres-p-rhabdoids O( I) Mbl.l Mb1.2 Mhal.l Mha1.2 Sw2 Mhil.l Mhi1.2 Swl Stomodaeum - b-rhabdoids (I) Mbl.l Mb1.2 Mhal.2 Mhal.l Mhil.l Mhi1.2 Swl Sw2 Stomodaeum-holotrichs I Mbl.l Mb1.2 Mhal.l Mhal.2 Mhil.l Mhil.2 Swl Sw2

Filaments-holotrichs I large Mbl.l Mbl.2 Mhal.l Mha1.2 Mhi1.2 Mhil.l ~ Sw2 Filaments-holotrichs II Mhil.2 Mhil.l Mhal.l Mbl.l Mb1.2 Mhal.2 Swl Sw2 Filaments- p-rhabdoids 0(2) large Mhal.l Mha1.2 Mb1.2 Mbl.l Mhil.2 Mhil.l arated all species studied (Tables 3, 4); holotrichs I from stomodaeum-separated M. hispida and S. wellsi from the other two species studied (Tables 3, 4); holotrichs I (large) from filaments-separated all species studied (Tables 3, 4); holotrichs II from filaments-separated S. wellsi from the other species studied (Tables 3, 4); and p-rhabdoids D(2) (large) from filaments-separated all species of Mussismilia (Tables 3, 4). S. wellsi was not included here, since it has only one size class of this type of nematocyst in the mesenterial filaments (Fig. 2). SECOND STEP.- The following nematocyst types showed result A: p-rhabdoids D(1) from acrospheres (Table 5); holotrichs I from stomodaeum (Table 5) and p-rhabdoids D(2) (large) from filaments (Table 5). The following nematocyst types showed result B: b-rhabdoids (1) from stomodaeum-separated S. wellsi from the other species studied (Tables 5, 6); holotrichs I (large) from filaments-separated S. wellsi from the other species studied (Tables 5, 6); and holotrichs II from filaments-separated S. wellsi from the other species studied (Tables 5, 6).

DISCUSSION In his preliminary notes, Den Hartog (1980) introduced an interesting discussion about scleractinian cnidae. He compared the distribution of Penicilli E (=holo-

Table 5. Summary table ofF values in the nested analysis of variance (second step) for capsule length of cnida types of Mussismilia hispida, M. hartti, M. braziliensis and Scolymia wellsi

Structure Cnid. type Among species Acrospheres p-rhabdoids 0(1) F[3,8] = 5.42 F = 1.66 Stomodaeum b-rhabdoids (1) F[3,8] = 5.42 F = 8.73* Stomodaeum holotrichs I F[3,8] = 5.42 F= 5.18 Filaments holotrichs I large F[3,8] = 5.42 F = 26.55* Filaments holotrichs II F[3,8] = 5.42 F = 30.69* Filaments p-rhabdoids 0(2) large F[2,6] = 5. 14 F = 1.30

• Statistically significant (P < 0.05). PIRES AND PITOMBO: CNIDAE OF BRAZILIAN CORALS 241

Table 6. Student-Newman-Keuls Procedure of cnida types with significantly different means among species in the nested analysis of variance (second step). Mhi I = M. hispida colony I; Mhi2 = M. hispida colony 2; Mhi3 = M. hispida colony 3; Mhal = M. hartti colony I; Mha2 = M. hartti colony 2; Mha3 = M. harlti colony 3; Mb 1 = M. braziliensis colony I; Mb2 = M. braziliensis colony 2; Mb3 = M. braziliensis colony 3; Swl = S. wellsi specimen I; Sw3 = S. wellsi specimen 3; Sw4 = S. wellsi specimen 4

Stomodaeum - b-rhabdoids (1) Mb3 Mhi3 Mbl Mhi2 Mha3 Mb2 Mhal Mha2 Mhil Sw4 Sw3 Swl

Filaments-holotrichs I large Mhi3 Mb3 Mbl Mb2 Mha3 Mhal Mhi2 Mha2 Mhil Swl Sw3 Sw4 Filaments-holotrichs II Mhi2 Mhil Mbl Mhal Mha3 Mb3 Mha2 Mb2 Mhil Sw4 Sw3 Swl

trichs I, sensu Schmidt, 1972; 1974) in the main organs (except the stomodaeum) of 33 species of coral. He included in the study four species of Mussidae showing this type of nematocyst in the mesenterial filaments. We confirmed the presence of this type in the filaments of Brazilian Mussidae (Figs. 31, J; 41, J; 51, J; 61, 1) and added its occurrence in the stomodaeum of these species (Figs. 3F, 4F, SF, 6F). We did not record in this category the abrupt end of the tube into a vestigial thread (the reason why Den Hartog considered them as penicilli). As indicated by Schmidt (1974), we noticed a gradual tapering of the tube (Fig. 3J). We doubt ifholotrichs II occur in the mesenterial filaments. It was not possible with light microscopy to discern to which category this nematocyst belongs. It seems that the same type is common in the sweeper tentacles of some species of corals (Den Hartog, 1977; Hidaka and Miyazaki, 1984; Hidaka and Yamazoto, 1984; Hidaka et aI., 1987). This type has been occasionally confused since different authors used different terms to name it (Hidaka et aI., 1987). Thomason and Brown (1986) have also recognized morphological varieties of p-mastigophores (=p-rhabdoids D, sensu Schmidt, 1972; 1974) in Montastrea (Faviidae). Two of the three varieties observed by them are structurally similar to those occurring in the Brazilian Mussidae. Four different types of nematocysts were considered as valid taxonomic characters for the studied genera. A qualitative difference was observed in the p-rhabdoids D(2) from the mesenterial filaments. They occur in Mussismilia in two size classes (Table 2; Figs. 2, 3M, N; 4M, N; 5M, N), while in Scolymia there is only one (Table 2; Figs. 2; 6M). Quantitative size differences were observed in three types of nematocysts: b-rhabdoids (1) from the stomodaeum (Tables 5, 6); holotrichs I and holotrichs II from the mesenterial filaments (Tables 5, 6). Schmidt (1972) commented on the diagnostic significance of the variation of sizes and shapes of scleractinian nematocysts. On the other hand, the types of nematocysts occurring in the different suborders of Scleractinia show little variation regarding to their distribution (Pires, in prep.). The results here reported support the importance ofmorphometrics in the study of coral cnidae.

ACKNOWLEDGMENTS

We are grateful to field facilities offered by the staff of Parque Nacional Marinho dos Abrolhos, Bahia, Brazil. Special thanks to Dr. C. B. Castro, Museu Nacional, Rio de Janeiro, for his assistance 242 BULLETIN OF MARINE SCIENCE, VOL. 51, NO.2, 1992 in the preparation of this manuscript. We thank Dr. P. S. Young, Universidade do Estado do Rio de Janeiro who provided advice in statistics and assisted in the analysis of data. We thank L. A. A. Costa for the final version of the figures. The authors are grateful to Drs. E. Robson, E. Schlenz, S. D. Cairns and F. L. Silveira for critically reading the manuscript and for helpful comments. This paper was partially funded by Conselho Nacional de Desenvolvimento Cientifico e Tecnol6gico, Brazil, through Dr. M. J. C. Belem, who encouraged this study, and through a graduate fellowship to F. B. Pitombo.

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DATEACCEPTED: October 28, 1991.

ADDRESS: Departamento de Invertebrados, Museu Naciona/IUFRJ, Quinta da Boa Vista, sao Cris- t6vao, 20942, Rio de Janeiro, RJ, Brasil.