Biology and infestation rate ofCorallonoxia longicauda,

an endoparasitic copepod of theWest Indian reef coral

Meandrina meandrites

by

Maureen E. Butter

Institute of Taxonomic Zoology, University of Amsterdam, The Netherlands

&

Caribbean Marine Biological Institute (Carmabi), Curasao, Netherlands Antilles

Abstract meandrites with its copepod parasites

the of Corallonoxia of During 1½ year biology longicauda, as an object investigation during my stay at a copepod endoparasitic in the stony coral Meandrina mean- the Caribbean Marine Biological Institute (Car- drites was studied in Curaçao, Netherlands Antilles. mabi), Curasao, from December till The infestation rate of the corals as well as the numbers 1, 1975

of parasites present were investigated at several depths and June 1, 1977.

in several stations. The parasites proved to be distributed This investigation was meant to elucidate the in a spatial pattern inside the colony. This pattern appeared between host and be and relation parasite (harmfulness to correlated with current exposure. It is postulated that the numerical distribution of the for the reef, propagation and distribution, role in differs from copepods in the corals, which markedly a normal the skeleton formation of the coral, bathymetric of and distribution, depends on the way proliferation settling and possible other environmental In this of the parasites. This offers also an explanation for the factors).

remarkable inside the spatial pattern colony. context transplantation experiments were carried The results of the comparison of the biomasses of host and which corals out, during live were moved from parasite indicate that the parasite must be rather harmless 30 m depth to 10 m and vice versa. Furthermore, to its host, and that no significant influence of its metab- skeleton of be taken olism on the formation the coral is to samples were from locations where the

expected. orientation of the reef slope towards the current

differs from the the latter INTRODUCTION principal station, being

more or less representative of the general situation Stock (1975) recorded the first endoparasitic at the S.W. coast of Curasao. copepods in West Indian stony corals. These It is that a well-known fact some coral , with copepods, ten new species, were classified which also among Meandrina, expell spontane- two new genera, Corallovexia and Corallonoxia is ously (that without apparent reason) their of the new family Corallovexiidae. zooxanthelles. The possibility that parasites form In Curasao three species are particularly abun- this in a major cause for was considered; that case dant, viz. Corallovexia brevibrachium Stock, 1975 "bleached" corals should contain parasites more in Diploria labyrinthiformis (Linnaeus, 1758), frequently and in larger quantities than specimens C. longibrachium Stock, 1975 in areolata capable of maintaining their zooxanthelles. This (Linnaeus, 1758) and Corallonoxia longicauda assumption was also tested. Stock, 1975 in (Linnaeus,

1758). The latter species was sometimes met with CHARACTERISTICS OF THE RESEARCH in such extraordinary large quantities that it seem- AREA ed not improbable that these parasites exercise an important influence on the metabolism of their Curasao belongs to the Dutch Leeward Islands. host. It was this assumption that made me choose Because of the constant trade winds the current is

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Fig. 1. Location of the sampling stations 1 to 6; occurrence of Corallonoxia longicauda in Curaçao (scale 1 : 960000).

from East to West for most of the time (fig. 1). Station 1 has the following characteristics:

The reefs at the leeward S.W. coast usually show constant current from Southeast to Northwest;

in the station — other S.W. cross section profile as drawn for 1 compared to locations at the coast

(fig. 2A). Station 1, situated in front of Rifwater, the water is a bit murky because of the effluent

the East of Piscadera, is by far our most important of nearby situated freshwater distilling sampling point. For comparison, samples have plant and the outflow of muddy water from

in been taken from station 2, front of the Holiday Rifwater, a salty lagoon;

Inn Hotel, and the stations 3 to 6 at the N.E. Meandrina meandrites is abundantly present coast of Curasao (fig. 1). at all depths where I was sampling (3-33 m),

In but abundant between and samples from station 1 we determined: (1) most 3 5 m. the rate of infestation at various depths, (2) the — the general physiognomy of station 1 is shown biomass of host and parasites, (3) the rate of in table I.

infestation of the rate of young colonies, (4)

of "bleached" and the Station in front has infestation Meandrina (5) 2, of Holiday Inn, a double

spatial distribution of the parasites inside the reef parallel to the shore, a cross section of which colonies. Also the transplantation experiment was is shown in fig. 28. Samples were taken from the carried out here. inner slope, which lies faced to the shore and thus

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Table I — the assemblage of corals on the inner slope

Percentages of coverage at station 1. does not differ from that on the outer slope

station at 2, or at station 1. 4!/2 m 12 m 22 m 30 m

(%) (%) (%) (%) Stations situated the N.E. 3 to 6 are at coast (fig.

Meandrina meandrites 6.4 3.9 all round to the 19.9 3.8 1). They are year subjected strong Agaricia 1 2.2 3.2 4.8 5.5 sp. trade wind (average velocity 7.2 m/sec). So Montastrea 9.6 17.7 sp. 3.0 15.1 violent is the water movement that diving is most Rock, sand, algae 57.0 67.4 72.1 69.6

2 Other 17.7 7.8 9.6 3.3 of the time impossible and always dangerous. The

reef differs in several from that on the 1 respects Mostly A. agaricites (Linnaeus, 1758) in shallow waters S.W. Near the shore there and almost exclusively A. lamarcki Milne Edwards & Haime, coast (cf. Bak, 1975).

below 20 1851, m. is a vehement water movement, the terrace slopes 2 of Madracis An important part hereof (6.6%) is constituted down and for distance of about very gradually a mirabilis (Duchassaing & Michelotti, 1861), at the other is with depths this species is entirely absent. 200 m from the shore it densely covered

and with Sargassum other algae, now and then reversed to the current and as flat discs of fire coral Mille- exposition compared large sponges or (

to the situation in station 1. this of about pora). Beyond 200 m, at a depth

20 m, the begins. Here the corals have Further characteristics of station 2 are: a different shape than at the S.W. coast, they are — the current is from Southeast to Northwest, but and Like the larger flatter. on S.W. coast, Mont- bit often quite a stronger than in station 1; is dominant the astrea the species, Meandrina on

other hand is rather scarce. The cross section

profile of the stations 3 to 6 is drawn in fig. 2C.

METHODS

— with Collecting. Collecting was done

the aid of SCUBA Corals gear. of about the same

size were jerked loose from the substratum with

divers' and the orientation with a knife respect

the reef marked with in to slope was small cuts

the of the edge colony. Next the coral was put into

numbered a plastic bag, and number and depth

noted formica. were down with pencil on a piece of The corals, still in their plastic bags, were trans-

ferred into a bucket of seawater and in this manner

transported to the laboratory for furthertreatment.

— With the Sawing. a diamond-saw colony

sawed into 4 4 was cubes (approximately X cm

colony surface), which could be examined for

parasites or tissue weight.

Isolation of the parasites. — Es-

sentially the method of Stock (1975) was fol-

little lowed, a simplified.

(a) Using decomposed corals:

The coral in piece of is incubated seawater or tap-

it with water. After 2 or 3 days is squirted off a

water 2. Profiles the section. pick (method: Johannes & Wiebe, 1970), Fig. of sampling stations in cross

10

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after which the tissue and mixture tube is into water, parasite put a porcelain cup, subsequently

is filtered through a fine mesh cloth (mesh size: dried, weighed, ashed and weighed again, after

In this the of the coral which it is calculate the ash-free 0.2 mm). way major part possible to dry

tissue, which has become more or less liquid, weight.

the but the chitinous passes cloth, not parasites. Freshly isolated parasites too can be dried,

and I did for males and Disadvantage: if, by chance, eggs are present, weighed ashed. so females

with this and and they are lost method remain un- separately used the results to convert numbers

noticed. Nor is it possible to determine the biomass of parasites into units of ash-free dry weight, for

of the parasites thus isolated. comparison with the dry weight of the colony in

(b) Using fresh corals: which they were found. Without previous incubation the living coral is T — ransplantations. Corals from 10 m off, the water filled with sea- squirted pick being collected and marked the usual depth were way water. Filtering renders living parasites surrounded and transported to 30 m, where they were cemented by pieces of coral tissue. Sometimes ovigerous to plastic grills with Marine Tex (method: Bak, females sometimes also or are present, single eggs 1973). Care was being taken to keep the corals in clusters of eggs. the in same orientation towards the slope as their Disadvantage: the coral can not be cleaned original site at 10 m. The grills were well anchored thoroughly. Besides, the counting of the parasites to the substratum with nylon lines. The same is a laborious and lengthy job, because they are procedure was followed with corals from 30 m hardly distinguishable between the pieces of coral when transferring them to 10 m. After six months tissue. the transplants were examined for parasites.

Superficies determination. — Both

numbers of parasites and tissue weights foundwere

related to the projected surface, that is the surface

formed by connecting the farthest protruding

the the edges of rows of septae of living part of

This be measured the the colony. can by covering

with aluminium colony as accurately as possible

foil, which is weighed afterwards. For small pieces of for biomass determination. Fig. 3. Sawing scheme a coral with the of coral a reasonably flat surface I applied P, cubes of which parasites are counted; W, cubes of which ash-free dry weight is determined. following system: a piece of mosquito net, by

with means of coloured thread provided a lattice

2 2 2 1 cm 0.5 cm and 0.1 cm is over denoting , placed Biomass determination. — A fresh

the surface to be measured, next the coral is shown From compartments sawn into pieces as in fig. 3. are counted. This method is more accurate and the cubes marked P the parasites are counted, much faster than the aluminium foil method, from the cubes marked W ash-free tissue weight that the are not too large. is determined. For this after provided pieces purpose, immediately

the cube in is into sawing question put a plastic RESULTS AND DISCUSSION

with little has bag a bit of seawater. This to be Occurrence 1. of the parasite on the Curaçao reefs frozen quickly. After subsequent thawing it is

II possible to remove all tissue with the water pick. Table gives the numbers of Corallonoxia longi-

The liquid tissue mixture resulting is centrifuged cauda found during the present study in the sta-

for 15 minutes at 500 is tions 1 to 6. 1 shows all the localities where rpm (filtering impossible Fig. because of the slimy consistence of the liquid). C. longicauda ever has been found. Both Stock's

filtered results indicate that The supernatant is through a previously (1975) and my own findings

dried and filter with known ash C. is the entire S.W. weighed rest. longicauda very common on

This with the together the deposit from the centrifuge coast. Apparently it is much rarer on N.E.

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Table II

Occurrence of Corallonoxia longicauda at the different sta-

of tions. The figures in the last column are the result com-

2 puting the number of parasites per 100 cm coral for each

and these for the number separate colony averaging (N)

of colonies examined.

station depth N coral % average (m) colonies infested parasite

examined density

1. Rifwater 3-5 9 100 27.9

10-12 27 74.1 190.0

15-22 18 55.6 16.6

27-33 19 63.2 10.5

2. Holiday Inn 15-22 11 54.5 46.3

3. Sintjoris 15-22 4 75 13.5

4. Boca Grandi 15-22 2 0 0

5. Santu Pretu 15-22 2 0 0

6. San Pedro 15-22 6 0 0

of Sint that lies 4. Corallonoxia Difference in of coast, with the exception Joris Fig. longicauda. A, aspect dead and alive difference in of assumed the males, (5 X); B, aspect closest to the large population on dead and alive females, (5 X); C, a sequence of positions S.W. coast. adopted by a male, in a petri dish (2 X); D, a sequence of

From Boca Santu Pretu two a female, in Grandi and only positions adopted by a petri dish (2 X).

it is this is corals were collected, true, but due to 2.2 Movements the great scarcity of Meandrina in these locations: Under the the bright light of a microscope lamp in station 1 at least seven or eight colonies could

of parasites make several sorts of movements. Adult have been collected during a dive comparable males are the most active and mobile, small juve- length. niles (<1.5 mm) do not move. The males are At Sint Joris the reef characteristics do not differ

the of and the meta- from the rest of the N.E. coast, including capable contracting expanding and of the the of the some twisting urosome. They move scarcity Meandrina, so parasites occurring the cephalic appendages as well as caudal rami, there most probably originate from the S.W. coast. the latter be curved The This indicate that the larvae of this can (fig. 4C). principal may parasite

movements are: of the meta- have short at all. bending cephalosome, either a very pelagic stage or none and with some urosome respect to each other and

in various directions. 2. Observations in vivo on the parasite Usually the caudal rami are

fixed on the the bottom of the coral it kept spot (on petri By squirting off a living with seawater which dish), from point a contraction wave isolate In passes was possible to living parasites. seawater with the through the body, strongest emphasis on they could sometimes be kept alive for a couple of the articulation between urosome and metasome. hours, but usually they live shorter. The females can curve their body in the ventro-

2.1 Appearance caudal plane. Usually they only move their lateral

Parasites obtained this differ in trunk with to each other way markedly prolongations respect

of corals that have and the appearance from parasites out to body (fig. 4D). Females seem to be far

for while. than been left macerating a They are more less mobile males, possibly they are more

swollen and in males the articulation between uro- sensitive to the change of environment and die

and is less visible neither some metasome clearly (fig. sooner. However, males nor females

devoid of limbs. In worth 4A). Juvenile females seem managed to move (in a dish) a distance juveniles of the size in which the male urosome mentioning, despite the sometimes quite violent has not out it is not to movements. Still be of yet grown always possible they might capable moving see the difference between the sexes. through the coral tissue inside the colony.

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Zooxanthelles the about 20-40 2.3 on abdomen, eggs per package, in multiserial (fig. 5). Some parasites had zooxanthelles in their skin arrangement In coral colonies with females in the below ovigerous some- and layer the skin as well. These

times loose were found, similar in size and correspond in size and shape to the host's zoo- eggs to the of Corallonoxia. xanthelles. Some of them looked shrunken and general appearance eggs

These that were surprisingly mobile, rotating deformed. This is a strong indication the eggs also in clusters of 2-5 The loose feed the coral's tissue. The zoo- constantly, eggs. parasites upon with were provided a ciliated ridge, xanthelles, being quite indigestible, are excreted eggs spiral

whereas the in the did not have this. through the skin. eggs packages

It is not of that the loose sure, course, eggs are

the later parasite's, but they some 2.4 Eggs may represent let the in the stage. Attempts to eggs hatch labora- Some coral colonies contained ovigerous females tory were not successful. Part (only found in fresh material). of a colony

full of ovigerous females was left in a tray of 3. Population dynamics Al- fresh water and squirted off the next day.

females trace of 3.1 Infestation rate in relation to though many were present, no

could be observed and size eggs anymore. depth colony

in There is a difference appearance between Table III gives the numbers of parasites, the ovigerous and non-ovigerous females. The latter superficies of the coral colony and the rate of slimmer and lateral are definitely the body ap- infestation the number (as expressed by of para- less in pendages are curved. Whenever a colony sites 100 2 coral for per cm any given colony), all adult ovigerous females were present, other at four different depths at station 1. females carried or least had the same eggs too, at

3.1.1 Relation between size and infestation appearance as the ovigerous ones. colony

The 0.4-0.7 in rate. — The in table III do indicate eggs measure mm diameter, they figures not a

in size and the number are rich in yolk. They are carried two packages correlation between colony

of the parasites per colony: at 3-5 m depth

correlation coefficient is 0.57, at 10-12 m 0.07,

and at 15-22 m -0.28 at 27-33 m 0.11. There are

correlation. The older two reasons to expect such a

it will the coral, the more parasites contain, because

it has been exposed to possible infestation for a

longer period. The larger the colony, the more

chance for a free-swimming larva to "hit" it and

settle in this particular colony. Apparently the

differences in size within the examined range

2 (about 100-300 cm ) are not large enough to

show the effect of either mechanism.

3.1.2 Relation between infestation rate and depth.

— Evidently the average parasite density per

colony (defined as the sum of the last column of

table III divided by the number of observations,

has maximum 2/N) a at 10-12 m depth. At 3-5 m

this is much but still average lower, considerably

higher than below 15 m. If we take as null hypo-

thesis that the parasites are equally abundant in Fig. 5. Ovigerous females of Corallonoxialongicauda (12 X) the corals of all we based on the Packages of eggs are attached to the ventral side. depths, may,

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Table III

Number of Corallonoxia longicauda ( N parasites), superficies of coral colony and density of the parasites (= parasites per

2 100 cm coral), at station 1.

depth N surface parasites depth N surface parasites

2 2 2 2 100 cm (m) parasites (cm ) per 100 cm (m) parasites (cm ) per

3-5 3 113.7 2.6 15-22 0 205.2 0

14 102.5 13.7 0 191.7 0

17 156.3 10.9 0 174.4 0

21 182.9 11.5 0 169.2 0

35 163.3 21.4 0 143.6 0

35 118.2 29.6 0 136.0 0

67 254.6 26.3 0 128.2 0

117 159.9 73.2 0 104.7 0

134 217.5 61.6 1 294.8 0.3

2 166.5 1.2 mean 49-2 163.2 27.9

4 212.4 1.9

6 209.0 2.9

10-12 0 268.1 0 17 109.8 15.5

0 212.3 0 18 115.3 15.6

0 203.6 0 38 179.7 21.2

0 184.4 0 48 242.3 19.8

0 128.4 0 83 145.7 57.0

0 125.3 0 164 98.3 166.8

0 116.9 0 mean 21.2 168.1 16.8

6 126.8 4.9

8 150.8 5.3 27-33 0 199A 0

54 110.0 49.1 0 197.4 0

64 175.0 36.6 0 148.1 0

122 160.3 76.1 0 124.9 0

124 211.7 58.6 0 124.0 0

139 153.7 90.4 0 102.7 0

145 130.0 111.5 0 77.2 0

223 104.3 213.8 4 193.3 2.1

240 103.7 231.4 4 163.6 2.4

258 113.6 227.1 9 210.1 4.3

308 95.5 322.5 9 136.8 6.6

312 209.7 148.8 9 125.8 7.2

364 140.3 259.4 11 172.5 6.4

405 188.0 140.6 11 99.9 11.0

409 246.1 166.2 19 133.0 14.3

472 55.8 845.9 20 154.5 12.9

1411 161.4 874.2 27 143.8 18.8

1423 121.0 1176.0 67 231.5 28.9

2240 211.7 1058.1 102 122.6 83.2

mean 32}.4 1593 190.0 mean 15.4 155.9 10.5

data from table III. construct a synopsis (table Table IV

The between the values found IV). discrepancy Expected and observed densities of Corallonoxia longicauda and in IV is that the different 1. expected table so evident, at depths at station

2 -test is much X as as unnecessary. parasites parasites

the conditions at 10 m are much more 2 2 Obviously depth per 100 cm per 100 cm N

favorable for the parasites than elsewhere. This (m) coral found coral expected colonies

favorable difference one or more may depend on 3-5 27.9 80.5 9 of the factors: better chances of following (1) 10-12 190.0 80.5 27 life for the parasites inside the colony; (2) greater 15-22 16.6 80.5 18

27-33 10.5 80.5 19 possibilities for free-swimming parasite larvae to

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inside the infest; (3) greater reproductive success

colony (or greater possibilities of re-infestation of

the same colony by the progeny).

3.1.3 Distribution over the colonies. — The

graphs (fig. 6) represent the frequency distribu-

tions of the parasite densities over the colonies,

arranged in four depth classes. None of them

the normal with corresponds to distribution, pos-

from the sible exception of the colonies 3-5 m,

number of observations being too small to be

decisive. Anyway, all distributions are skewed to

the right: many with zero or few, relatively very

few with the of the class average density depth

concerned, and a considerable number with a

relatively high density.

The ratio between the number of colonies with-

with out parasites and the ones one or more

indicator chance parasites can serve as an for the

infestation Because of a primary from the water.

of the low infestation rate on the N.E. coast and

of the also because large yolk-rich eggs, we may

that larva assume the of Corallonoxia longicauda

with is a highly developed one, without or a very

short pelagic stage. It will therefore settle in the

vicinity of the colony where it originated from,

If or perhaps even in its own colony. this as-

is the sumption true, chance of a primary infesta-

tion will depend on: (1) the density of Meandrina

of the meandrites on the spot, (2) the magnitude

local parasite population, determining the amount

of larvae that are released into the water, (3)

colony size, in view of the chance to be "hit" by

a larva, (4) possible other factors facilitating or

the of the water hampering settling a larva, e.g.

movement, or the behavior of the larvae. As far

as these factors are known they can be arranged

in tabular form as given in table V.

Table V

Density of Meandrina meandrites and Corallonoxia longi-

and of coral colonies cauda, average superficies at different

depths at station 1.

average density

of of Corallonoxia depth % coverage average colony 2 (m) of Meandrina per colony surface in cm

3-5 19.9 49.2 163.2

10-12 6.4 323.4 159.3

15-22 3.8 21.2 168.1 Fig. 6. Distribution of the parasites over the coral colonies at 27-33 3.9 15.4 155.9 different depths.

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On account of the in table V is figures we can bility a situation whereby initially the larvae are

formulate the following expectations: released into the seawater, but are caught back

partially by their own colony. This second (A) 3-5 m compared to 10-12 m: indecisive. pos- the fact The sibility offers an explanation for apparent density of the host is higher at 3-5 m, that this mechanism is not equally effective the parasite population, on the other hand, every- where is smaller. on the reefs.

Whatever the nature of the mechanism, the (B) 3-5 m compared to 15-22 m and 27-33 m:

will only start functioning after the more infested colonies in the shallow waters, self-support

both parasite population has reached a certain threshold because the host population and the value. Until that moment the size of the population parasite population are larger. will the from the 10-12 to largely depend on supply sur- (C) m compared 15-22 m and 27-33 m: rounding water and the life of the parasites. more infested colonies at 10-12 m for the span

As soon as thethreshold is reached, the same reasons. demographic

determinants become different: the factor "birth", (D) 15-22 m compared to 27-33 m: no difference. in is case of a cycle entirely inside the coral, In the next tabulation, concerning the numbers dependent on the number of fertile females and of infested and uninfested colonies at several the of sufficient number of males presence a per depths (table VI) the figures are derived from 2 in 100 cm coral; case of larvae being released table III. The differences the in between groups and partially caught back it is, in addition, de- table VI are in accordance with the expectations pendent on factors facilitating or impeding the given above. The significance of these differences catch-back, like the size and shape of the colony, can be tested with Fisher's test. With a confidence the water movement and the behavior of the larvae. of 95% can be stated that the difference between in The figures the next table (table VII) are 3-5 m and 15-22 m and the difference between derived from table III. The chosen density of 20 3-5 m and 27-33 m are significant indeed, the 100 2 is somewhat but parasites per cm arbitrary, differences between the other groups are not. must be "above the threshold" I believe, owing to the factor Apparently "density of the host" is a the shape of the frequency distribution of the very important one. densities. Furthermore, we only consider infested

colonies because the aim is to examine the Table VI here,

the Numbers of infested and effectivity of "self-supporting mechanism" at uninfested colonies, and percentage of infested colonies at station 1. different depths.

depth N colonies N colonies % Table VII (m) uninfested infested infested

Infested coral colonies: colonies with and more colonies with

3-5 0 less than 20 100 2 9 100 parasites per cm coral, at station 1.

10-12 7 20 74.1

colonies with 15-22 8 10 55.6 less colonies with more

than than 27-33 7 12 63.2 depth 20 parasites 20 parasites

100 2 2 (m) per cm per 100 cm

Now the form of the distribution of the parasites 3-5 4 5 is 10-12 2 18 partially elucidated. Still the frequency of heavily 15-22 6 4 infested colonies and the absence of a middle 27-33 10 2

infestation remain group (with average rate) to be explained. Especially at 10-12 m we find ex- According to Fisher's test (95% confidence) ceedingly densities. This of high suggests a mecha- the group 10-12 m has significantly more nism of by means which an colonies with 20 100 2 existing parasite parasites or more per cm

its own with than the population supplies colony new deeper categories. Compared to 3-5 m

exist There a the difference is it if progeny. may reproduction cycle not significant (but is, we inside completely the host; an alternative possi- compare the number of colonies with 40 parasites

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100 2 The of the The corals that to shallower or more per cm ). efficiency were transplanted environ- mechanism is highest at 10-12 m, below 15 m waters reacted very favorably to their new

most colonies probably do not reach the threshold, ment. At the end of the six months' period they

the infestation rela- all seemed have as chances on a primary are were very healthy, they to grown

this be the for and left of the small at the tively small. At 3-5 m cannot case, no trace was damages

here is the chance on a primary infestation probably edges that had served to mark their orientation.

the Pre- The corals did same or even better than at 10-12 m. transplanted to the deep not so

A weeks sumably the failure of the catch-back is due to the well. few after the transplantation some

this them started water movement, which is rather violent at of to show white spots. The more

because the larvae their Some depth of the surf action, so are convex shape the more they suffered. ;

washed from their own of them died off the and at the end away quickly colony. along edges

of the six months' period 3 of the 30 had com-

3.2 Transplantations died and had died off pletely many partially.

VIII Table records the rate of infestation, the Considering the infestation rate no difference

living colony surface as well as the part of the can be demonstrated between the corals trans-

that died six colony since the transplantation planted from 10 to 30 m and the corals per-

months before. manently growing at 10-12 m (table III), neither

in infested in percentage nor density of the para- Table VIII sites. The from 30 to 10 group transplanted m Transplantations executed at station 1, results after six in did not show a difference infestation percentage months. The column “ead surface” records the coral surface with the But that has died after the transplantation. control group growing at 27-33 m.

the transplanted colonies did have significantly surface dead surface N living parasites per more colonies with 20 or more 2 2 2 parasites 100 Corallonoxia (cm ) (cm ) 100 cm coral per

2 cm This is indication that somehow the catch- . an

from 10 m transplanted to 30 m: back works more at in that effectively 10 m, case 0 74.9 0 0 the difference in between the 0 84.1 11.4 0 parasite density

6 103.2 0 5.8 corals from 10-12 m and 27-33 m is not entirely 12 190.4 0 6.3 the fact that it due to at 10-12 m is easier to reach 37 125.7 1.7 29.4 the threshold value for 45 99.7 12.5 45.1 self-support.

51 82.3 0 62.0 Furthermore the results that the suggest para- 80 103.7 24.5 77.1 after in sites, settling the colony, have a fairly long 152 120.3 10.7 126.4 life. One would that the 209 60.4 0 346.0 expect group transplanted

222 188.4 2.2 117.8 to shallower waters would count more infested

632 55.1 112.0 1147.0 six colonies after months. Apparently, even at 985 137.7 37.9 715.3

10 m the chance on a infestation is small, mean 187.0 109.7 200.1 primary which the life implies that span of the parasite to 10 from 30 m transplanted m: must be fairly long in order for the population as 0 214.4 0 0

whole to 0 190.8 0 0 a be maintained. Also the fact that the

0 124.3 0 0 parasite density in the colonies transplanted to the 0 122.3 0 0 deep did not drop steeply despite the deterioration 0 114.0 0 0

0 of the is indication of life 103.0 0 0 host, an a long span.

0 75.3 0 0

3 116.7 2.6 0 3.3 Infestation rate in very young 5 133.4 0 3.7 colonies 17 73.1 0 23.3

47 114.4 0 41.1 Very young colonies composed of one to four 70 101.7 0 68.8 examined for the polyps were presence of para- 85 139.1 0 61.1 sites. With the aid of data collected Bak 194 118.8 0 163.3 by &

mean 32.4 124.4 26.0 in Engel (preliminary results, preparation) con-

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meandrites Table X cerning the growth rate of Meandrina

of this of the corals in Numbers and of males, females and juveniles at format, the age question percentages station 1. in was estimated. The results are summarized

table IX. parasites

100 2 N N N depth per cm % % %

(m) coral s $ 9 9 juvs. £ 8 9 9 juvs. Table IX

colonies of Meandrina 100 0 Infestation rate and age of young 3-5 2.6 0 3 0 0

meandrites at station 1. 10.9 15 2 0 88.2 11.8 0

4.8 11.5 17 3 1 81.0 14.2 diameter estimated N age parasites depth 13.7 12 2 0 85.7 14.3 0 (cm) (months) 9 9 $ $ juvs. (m) 21.4 22 6 7 62.9 17.1 20

26.3 52 15 0 77.6 22.4 0

1.8 12-28 — 18 29.6 24 10 1 68.6 28.6 0

— 1.0 5-12 — — 15-20 61.6 72 62 0 53.7 46.3 0

1.7 11-26 — — — 15-20 40.2 73.2 68 47 2 58.1 1.7

1.4 8-20 — _ — 15-20 mean 63.7 33.9 2.5

—. — 15-20 1.6 10-24 — total 282 150 22

1.9 13-30 _ — _ 15-20

— 1.4 8-20 — — 12 10-12 5.3 4 0 4 50 0 50 1.0 5-12 — 7 — 12 58.6 100 24 0 80.6 19.4 0

1.0 5-12 — — — 12 90.4 98 40 1 70.5 28.8 0.7

— — 8 1.0 5-12 — 140.6 341 64 0 84.2 15.8 0

1.0 5-12 — — — 8 166.2 238 97 74 58.2 23.7 18.1

— 8 0.7 3-8 — — 4.4 845.9 685 664 62 48.5 47.1

874.2 1146 231 46 80.5 16.2 3.2

114 75.7 5.2 that these colonies do 1058.1 1696 430 19.2 It is clear young usually mean 69.9 25.2 4.9

not have so there must exist parasites, something total 4308 7550 301

like distribution of the a capacity parasite, to cause

15-22 0.3 1 0 0 100 0 0 the higher infestation rate in older colonies. 1.2 2 0 0 100 0 0 is males in Remarkable the finding of seven one 1.9 3 1 0 75 25 0

of these small corals; perhaps the larvae (or eggs) 2.9 4 2 0 66.7 33.3 0

15.5 14 3 0 82.4 17.6 0 attach to the planula of Meandrina, the latter being 15.6 13 5 0 72.2 27.8 0 than the Corallonoxia-egg s considerably larger 19.8 24 23 1 50 47.9 2.1

2-3 0.4-0.7 thus it could 0 (planula mm, eggs mm), 21.2 37 1 0 97.4 2.6 4 4.8 in is born with 57.0 73 6 88.0 7.2 be possible that some cases a coral 166.8 145 17 2 88.4 10.4 1.2 its parasites. mean 82.9 15.2 1.8

total 316 58 7

3.4 Ratio males, females and juve- 27-33 2.1 1 3 0 25 75 0 niles 2.4 2 2 0 50 50 0

4.3 6 2 1 66.7 22.2 11.1 In a number of colonies the males, females and

6.4 6 5 0 54.5 45.5 0 these numbers juveniles were separately counted, 6.6 7 2 0 77.8 22.2 0 and the in table X. At percentages are given all 11.0 9 2 0 81.8 18.2 0

45 45 found three times males 12.9 9 9 2 10 depths we two to as many 18.8 21 4 2 77.7 14.8 7.4 that the and as females. Assuming espe- 28.9 50 12 2 74.6 17.9 3.0 the females mobile within the cially are not very mean 69.8 25.8 4.4

total 41 colony, this could be functional. 222 7

The small number of juveniles in the samples

either short duration of the few that from suggests a juvenile none or very juveniles (those came

low birth rate. We do have the stage, or a reason surrounding water), or a complete new genera-

believe that all adult females in will tion The to a colony produced from own stock. highest per-

in other is procreate simultaneously (see § 2.4), centage found was 20% juveniles, that 1.17

words to find in either descendants female. the number one can expect a colony per Considering

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is in this of female to this not where there are not too eggs per (40 80), very many parasites;

much. Apparently the rest leaves the colony or case we do not find overdispersion either; (b) in

does not develop. colonies from the reef plateau, where both light

conditions and water movement differ from those within the 4. Spatial distribution colony find on the reef slope. Here we do overdispersion,

and After examination of different cubes cut from the but no regular pattern (more than one cluster

same colony, some cubes appeared to have striking- no special side of preference).

ly more parasites than other ones. In order to The colonies from station 2 originate from a

find if this reef which station out was some systematic phenomenon, slope lies, compared to 1, op-

that each cube was numbered according to its place in posite to the current. The two colonies con-

the null tained the the colony. According to hypothesis, any a sufficient number of parasites show

cube, regardless of its place, will have the same parasites' preference for the off-slope and down-

parasite density. As long as the expected number stream side of the colony as well (fig. 7, below).

of cube is not smaller than the In the from the N.E. likewise from parasites per 5, samples coast,

discrepancy between expected and observed fre- a differently oriented reef, the number of parasites

be 2 -test. From 18 too small allow check quencies can tested with a x the present was to for a on

colonies fulfilling the above condition, 14 had a their orientation.

random A made distribution differing significantly from a few night dives were to see if the corals

distribution with confidence of at when the would a 95% or more, nighttime, polyps are expanded, the remaining four were not significant. The latter show some particularities that could explain the were either colonies with rather few parasites or observed asymmetry in the distribution of the colonies sawed into four or less pieces. Some parasites. Nothing was found. colonies have been in As be correlated with diagrammatically pictured overdispersion appears to

fig. 7. The +, + +, 0, — and indicate the large densities, it is suggestive that there might magnitude and direction of the deviations of the be a connection with the self-supporting mecha-

the effect this average. nism, to that mechanism also causes

the remarkable in distribution spatia.1 pattern the

in If this is of the parasites the colony. true, we

have to decide in favor of a mechanism whereby

and the larvae (or eggs) leave the colony are

caught back partially, and not for a reproductive

cycle taking place entirely within the colony. As

the greatest concentration of parasites is off-slope,

that the larvae deliber- we may assume (or eggs)

in the ately move that direction. Either light attracts

them, or the zone with the greatest water move- Fig. 7. Colonies of Meandrina meandrites, diagrammatically ment. The latter seems more probable, for one represented, showing the spatial distribution of its parasites:

would an that is = less + = above to 0 more or average; distinctly average; expect going creep

= far above distinctly below less The + + average; — = average; inside a coral to be more or photophobic.

— — = far below Top row; colonies from station 1; average. slowest swimmers then carried are away only a from bottom row: colonies station 2. and very short distance with the current land

Most colonies had a cluster of parasites at one downstream of their parents in the same colony. side of the colony. From 13 colonies the orienta- On the reef plateau, especially in the shallower tion is known: in 8 colonies the greatest con- part, the water movement is more vehement and

of is the the centration parasites at the side away from irregular than on the reef slope. Presumably

and 3 colonies slope downstream, more have most larvae are here washed away easily from their own

at the side but but parasites off-slope not definitely colony, they have more chance to hit a neigh- downstream. This pattern is absent (a) in colonies bouring colony, because the density of Meandrina

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If is so high. The phenomenon of clustering at these weight and parasite weight in these corals. the

depths is explained by the fact that the entire parasites eat tissue, it seems that they do so quite

surface of most will not have Another is that the tissue a colony probably moderately. point gross

and 2 an equal chance of being hit there may be weight per cm proves to vary considerably. This

certain where larvae wash is there notable areas the easily up. not beyond expectation, for are

in size of differences the and form the septae,

5. rate and biomass Infestation which are left out of account in the measure

XI tissue Table gives gross weight (ash-free dry "projected surface".

weight in mg), that is the total biomass, composed 6. Infestation rate of “bleached” corals of coral tissue, Corallonoxia and possible other

In It that parasites. addition the table includes the density is a well-known fact some corals, including

of Corallonoxia in the corals in question and their Meandrina, under stress expell their zooxanthellae,

and thus tribute to the total biomass, computed from the gain a white aspect. On the Curasao reef

number males and observe sometimes white of females found in these one can corals amongst

corals and their viz. non-bleached The reason these average weight per sex, congeners. why

86.6 3 for and 3 X lO" mg the female 22.9 X 10 corals did expell their zooxanthelles remains a for the male. of discussion. in the of mg matter Could, case Mean-

drina meandrites in Curasao, Corallonoxia be a

Table XI XII such white major cause? Table lists a few of

Biomass and 2 coral parasites per cm at station 1.

Table XII

tissue Corallonoxia depth gross N parasite weight Parasite density in white corals at station 1. in m weight (observed) (computed)

2 2 cm coral in 2 inmg/cm per mg/ciri 100 2 2 parasites per cm parasites per 100 cm

at 10-12 at 15-22 coral, m depth coral, m depth 12-15 32.5 0 0

31.3 2.31 0.107 0 0 22.7 1.46 0.051 0 0 22.6 3.47 0.077 0 0 19.2 2.27 0.079 322.5 15.6 17.8 0 0 845.9 166.8 14.7 0 0 1176.0 14.7 2.14 0.069

27-33 33.1 0 0 corals and their density of Corallonoxia longicauda.

23.9 0.86 0.036 It is clear that some of the white corals do have

23.6 0 0 a few but in most of the white 23.5 0 0 quite parasites,

21.0 0 0 corals examined, Corallonoxiacould not be blamed

19.5 3.22 0.162 for the I bleaching. Besides, found some perfectly 11.1 0.65 0.037 normal-looking colonies similar num- 10.8 0.41 0.023 containing

10.1 0.04 0.001 bers of parasites.

8.8 0 0

CONCLUSION

Even in heavily infested colonies, The model for the of containing suggested parasites' way for instance 2 10 parasites per cm the in , parasite propagation (diagrammatically represented fig.

weight will be no more than about 0.5 mg per 8), together with some subsidiary assumptions

cm2 That is . not a very significant portion (1.5 to concerning the larvae, explains both the spatial of the total biomass, which that 5.7%) means the distribution of the parasites within the colony and CO of the a production parasites cannot play a the distribution of densities over the colonies. One role of in the calcification of the any importance implication is that the parents, as compared to the coral. speed with which their offspring populates the

Neither is there correlation between tissue do any colony, not move over a considerable distance

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model for of of Fig. 8. Suggested the parasite’s way propagation. A, Development a spatial pattern through self-infestation.

(1) Infestation from the surrounding water. Few parasites, randomly distributed. (2) Procreation starts, larvae are released and and direction. of back and move in downstream off-slope (3) Part the larvae are caught settle in the same colony.

larvae. (4) Many parasites, clustered together at one side of the colony, producing large quantities of

the the B, Distribution of coral colonies, parasites and larvae at the plateau and on slope. (1) Situation at plateau. A high

of colonies. Self-infestation is the and density Meandrina, many infested, larvae-producing hampered by strong irregular water movement (but probably still takes place), infestation from the surrounding water is facilitated by the high host

available data indecisive the low density. The are as to which process prevails. (2) Situation at slope. A comparatively density of the host and an accordingly lower infestation from the surrounding water, resulting in a relatively large number of Self-infestation works colonies without or with very few parasites. particularly well, resulting in exceedingly high densities in relatively few colonies.

inside the coral host. The question arises whether vious suffering; secondly the parasites are not

I distributed they are able to move at all. would say they are, evenly over the colony. The most for from the discrepancy between the number of heavily parasitized part will die off first, so that corals with 20 100 2 and at least of the will survive. or more parasites per cm a part colony Thirdly, the less infested conclude the of is densely corals, one can offspring every new generation produced that propagation starts to function at densities well closer to the edge of the colony and will have less

2 below 20 100 cm which, chance to settle in the same This is of parasites per , considering colony. also the for ratio males/females appears to point to a course favorable the dispersal of the species. certain in order to fertilization. The overall shows well mobility assure picture a parasite very

its in in The number of descendants is small, the fraction adapted to host, harmfulness as well as

their inside life and of Even in contributing to own population growth span speed reproduction. places

is the the host it is the colony even smaller. Still, after a time, this where density of is not so high, growth will by far exceed the growth of the host. possible for the species to survive, as long as there

The danger that the host will die under heavy are a few coral colonies of such shape and location

is with several mecha- that rich be built parasitic pressure coped by a parasite population can up, nisms. In the first place the coral can harbour an producing large quantities of larvae during a long amazingly great number of parasites without ob- period.

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duced. Most Summary probably the larvae are highly

developed, without a pelagic stage, they will move Corallonoxia has been found along a longicauda the substratum. swimming or creeping along S.W. of from large part of the coast Curaçao In view of the frequency distribution of the Santa Marta to Cornelis Baai. Probably it occurs parasites over the different colonies it is probable along the entire S.W. coast. On the N.E. coast that the reproduction cycle does not take place it has thus far only been found at Sint Joris. inside the but that of the entirely coral, some eggs Near Piscadera Baai it is most abundantat 10-12 or larvae released are caught back by their own is m. The percentage of infested corals highest at colony. This mechanism can very well be responsi- where its Meandrina is 3-5 m, host, meandrites, ble for the spatial distribution of the parasites the abundance of C. most abundant, greater longi- within the and the difference in colony average cauda 10-12 due the at m being to higher average of the parasite density colonies living at 3-5 m parasite density in the colonies infested. and 10-12 m. We will have to assume then, that The first infestation of the corals is brought the larva moves actively in the direction with the about by eggs or larvae from the surrounding from the greatest water movement, away slope. for be water. The chance a colony to hit by such a The stronger the current or water movement, the is but settled in the the larva small, once colony more larvae will be taken or eggs along, although parasites live very long. of them in their some manage to stay own colony. Their spatial distribution inside the colony is

in the is not random, some places density higher ACKNOWLEDGEMENTS than in other lower. In corals expected, places This research has been made possible by grants from the

Instituut Taxonomische growing on the reef slope there is even a distinct voor Zoologie (ITZ), Amsterdam, the WSO Foundation, The Hague, and the Treub Maat- found the pattern: most parasites are to be at off- schappij, Utrecht, The Netherlands. and downstream side of the in the slope colony, Furthermore, the cooperation of the Caribbean Marine other directions the concentration slopes down Biological Institute and its director, Dr. I. Kristensen, for housing, laboratory accomodation, equipment and diving gradually. facilities is acknowledged. The author is indebted to Prof. The of various kinds of copepods are capable Dr. J. H. Stock, Dr. R. P. M. Bak and Drs. J. Dieleman for movements, especially the males, but it is not clear help and advice. Diving assistance was rendered mostly by Mr. Lionel Maria, Mr. de Mr. Oscar if Humphrey Windt, they are able to move around inside the coral Mr. Frank Isabella and Mr. Tiel. Thanks Frank, Aubrey are Most coral colonies contain two to three colony. due to Mr. Carol Cardose for assistance in technical questions

the other hand and to the entire staff as well as visitors of times as many males as females, on the Caribbean for Marine Biological Institute many other services during the female weighs about three times as much as the period of the author's stay in Curasao. the male. There are not many juveniles, pointing

REFERENCES to a long life span.

Bak, R. P. M., 1973. Coral increment in situ. A Compared to the host’s, the parasite’s biomass weight new method to determine coral growth. Mar. Biol., Berlin, is small. of the coral its very Overburdening by 20: 45-57. in infested parasites, even heavily colonies, 1975. Ecological of the distribution of reef very , aspects could not be established incontestably. corals in the Netherlands Antilles. Bijdr. Dierk., 45 (2): 181-190. The female few The produces relatively eggs. JOHANNES, R. E. & W. J. WIEBE, 1970. A method for the does efficiency of the propagation not depend on determination of coral tissue biomass and composition. the of Limnol. 822-824. number eggs, but on the reproductive strat- Oceanogr., 15:

STOCK, J. H., 1975. Corallovexiidae, a new family of trans- egy: through self-infestation a colony can become formed copepods endoparasitic in reef corals. Stud. full of that so parasites larvae can be many pro- Fauna Curasao, 47 (155): 1-45.

Received: 16 June 1978

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