Journal of Coastal Research Fort Lauderdale

Prelitninary Data on the Meroplanktonic Larvae of Polychaeta in the NooDlea Lagoon, South-Western New Caledonia!

Michel Bhaud

Laboratoire Arago, (CNRS, URA 117) 66650 Banyuls-sur-mer, France ABSTRACT _

BHAUD, M., 1986. Preliminary data on the meroplanktnnic larvae of polychaeta in the Noumea lagoon, south-western New Caledonia. Journal ofCoastal Research, 2(3), 297-309. Fort Lauderdale, ,tllllllll,. ISBN 0749-0208. ..•_ ...~ This paper presents preliminary data on Polychaeta Annelida larvae from a coral reef .....- ofNoume~ • lagoon in thearea New-Caledonia. Larvalplanktonisrevealed as a good tool for faunistic investigations. A detailed surveyofbenthic communities shouldproduceas a con­ sequence, sampling ofnew species for the area: 7 species of Spionidae, 3 Chaetopteridae and 1 Sabellariidae. The advantages offered by such a geographically discrete area for the study oflarval spreading are discussed. The use of4 indices(numberofspecies, numberof individuals, diversity index and equitability) allow specificationofthe distanceofthe larval population sampled from its origin. Size comparisons between taxons sampled inside and outside thelagoonshowthatlengthofplanktoniclarval lifeis not an absoluteparameterbut is a function of extemal circumstances linked with water currents which reduce the ten­ dancy ofthe larvae to settlewith the sediment. With regard to seasonalvariations oflarval appearance in the plankto~ this area is not characterized by two groups ofspecies, each havingitsown reproductiveperiod. 88 itisundertemperatelatitudes, butbyonlyone group; the center of the reproductive period being adjusted to March and April.

ADDITIONAL INDEX WORDS: Annelida, lagoon, laroae, New Caledonia, Polychaeta, seasonal variation, sett1emen~ spreading.

INTRODUCTION provided some information It is therefore interest­ ing to compare the results of these investigations This work is partofa comparative oceanographic with data from a new geographic locale such as an investigation and springs from theremarks ofFAGE intertropical lagoon ofthe Western Pacific, located and DRACH (1957) on the comparative biology of in this study near Noumea in south-west New marine species in various areas within their dis­ Caledonia This area is becoming increasingly well tribution ranges. One means of knowing to what researched as evidenced by the results of studies extent and in what ways physiological cycles adjust dealing with geomorphology, hydrology, primary to geophysical factors is to see how these param­ production (DANDONNEAU et al, 1981; ROUGERIE, eters vary in diverse situations in the course of the holoplankton and hyponeuston fauna (BINET, 1984, year and to observe in parallel some biological 1985; CHAMPALBERT, 1982). Investigation of sea­ criterion, such as the time ofyear when larvae are sonal variations of meroplankton, which relate re­ present, the size of oocytes, or the proportion of production ofbenthic adults and settlement period juveniles. 0 bservations already made, especially for young stages, seemed a natural extension of on Polychaete annelids, in temperate (BHAUD, these previous works. 1966a), Indian tropical (BHAUD, 1972), and sub­ antarctic (DUCHENE, 1979, 1980) zones have already MATERIALS AND METHODS

1This work, conductedduringsurvey1979-1) ispartofajointproject This study examins a collection of zooplankton financed by the ORSTOM and the CNRS: IICoral reef and lagoon gathered over several years at several sites in ecosystems in New CakdoniLl' (CNRS - ATP 3393 and 4067. 85037 received 4 November) 1985; accepted in revision 27 Noumea lagoon. The samples were collected by January 1986. researchers at the ORSTOM center andtaken dur- tV co 00

0 N I 22 5/ '\.166°30 E ,0 2 NEW CALEDONIA

1/ 30 " + 4 0 NEW CALEDONIA I Kunie " ~.. Island ~. Q \ ... ", OULARI BAY Boulari Passage --''''- .. _-,' ~

,- , \ , .. ,; , , ~ , I :r' '--' Qj / ,----rJ '-"" t: X Q.. 0 I!Yl [/Maitre Island 0) ® 0 ~o [ill] LAGOON Goelal'ld Island " .. " ,." <:(' C>" \, '. ;: / ' .. ~ ,'. ~(\\ ~ fA"~ ~rt. _t '''J' ~'-'~ ./ ...... / Amedee ,- . ~~'\. 'J0~...e ,...... ,ort. 0 0 lighthouseri1 .' '; ~'~o ~,' ~--~' ---.:::::>' ",'" ~e o9>e r;-;, ~ .~_.., ~ ~~:' ~~- ~~ ~,~---. Q...O. _ ~~~ --, ~~.------~~ ---,- /.)!: ••-:---~--'.-'"::.'" ~ ---:::.' -----: 0<'" '-,' O~(l) '-- , ... _ ... -- ..... -- ~-J .... ----' ...... "-'::=~~/--::::::=:::6f'J...--.... ',,--- - ... --- -- :')'\ ",O~J('\.'lJ <:00 ::; b ",0 ~O'" ~ ~ 0 a...

1660 E 22°305

Jo'igure 1 Map of the reef lagoon, south-west New Caledonia. showing stations where planktonic larvae were collected; (1) stations on the lighthouse Amedee transect; (2) location of 24-hour studies; (3) coastal stations; (4) open sea sampling station in La Sarcelle straits. ing a field trip between March and May 1979, distances and compaction effects. Readings were (Figure 1). Different plankton nets, WP2 and FCO, taken after 24 hours of sedimentation. where used on different occasions, providing rapid In five out of the six samples, the collecting comparison of their catching power. The samples efficiency of net WP2 was greater, by 12% of the were taken during5 or 10 minute hawls at a depthof mean ofthe two measurements. Howeverthere was 1 to 2 m. The greatest depths in the lagoon are cer­ no indication that the differences were the same for tainly as much as 50 m, but around the small coral all the taxonomic groups considered. Thus, from reefs the water was shallower (10 to 20 m) and the precise counting of one particularly well represen­ depth in the sampling zone was often only 4 to 5 m. ted larval category of the family Spionidae, one The boat most often used, particularly around the observed that the WP2 net collected many more small coral islands, was ofthe Zodiac type. with an larvae than a comparisonofbiomass would lead one outboard engine. In this case, to maintain a steady to expect (Table 1B). In particular it retained those bearing it was necessary for the net to be towed size classes to which the larvae of annelids most directly behind the engine. The net was maintained often belong. This class makes up only a small frac­ in this position either by an assistant or by two tion of the biomass, which explains the small dif­ ropes attached to the sides ofthe boat at two points ferences between the comparative results for total forward of the engine. A more powerful boat, the biomass. oceanographic vesselDawa, 11 m long, was used for Although the FCO net seemed to be oflimited use coastal exploration. Inside the lagoon a thirdtypeof for collectingmaterialofaround300Jim, some sam­ boat La Santa Maria, 8 m long, was used for the ples taken.. outside the lagoon produced larger lar­ seasonal samplings of station IV and for com­ vae, up to 2 mm in size, which permitted precise parisons between the two types ofnets. Outside the identification to species level. Because the FCO net lagoon, the oceanographic vessel Vauban, 28 m sampled a wider range of sizes than was gener­ long, was used for a limited number of collections ally encountered in the lagoon, it was very madeinorderto study the mechanisms oflarval dis­ complementary. persion. Identifications in this preliminary study are limited to the family leveL Some larval forms Taxonomic Observations about not previously reported are described, although Polychaete Families their specific identification still remains imprecise Although it is not necessary to comment on each in the absence of cultures. However, in some cases family represented in the various tables, it should the determination was sufficiently precise to allow be noted that the two family names Aphroditidae us to come to some conclusions about the fauna and and Amphinomidae are used in the broad sense the biogeography. (FAUVEL, 1923) in that they are nowadays con­ RESULTS sidered to consist of five and two families, respec­ tively Our data suggest that the collected larvae Comparison of the Collecting Efficiencies belong in the former case to the Polynoidae and in of the Nets the latter case to the strict Amphinomidae as dis­ tinct from the Euphrosinidae. Likewise, the generic Because two different nets were used to obtain designations Prionospio and Polydora refer to the samples [WP2 net with mesh size 200 Jim, 0.57 m Prionospio andPolydora complexes, containingres­ diameter aperture and 2.6 m lonq (UNESCO, 1968) pectively four and six genera; Paraprionospio, and FeO net 300 Jim mesh size, 0.50 m diameter Orthopnonospio, Streblospio, andPrionospio on the and 2.9 m long (BINET, 1984)], a comparison of one hand, and Pseudopolydora, Polydora, Caraz­ their catching power was necessary. For this pur­ ziella, Tripolydora, Boccardiella, and Boccardia pose, both nets were simultaneously towed for 10 (BLAKE and KYDENOV, 1978) on the other. minutes in parallelover part of the transect from Noumea to Amedee lighthouse. Six pairs of sam­ Family Opheliidae ples were obtained at 2 m below the surface at a (A) One very common species was collected in speed of 1.5 m/ s. After each sampling the total the sub-surface plankton samples. Gills present catch was assessed (Table 1A). The results were from the second setiger, ocular spots on the median compared on the basis of the biomass collected in parapodia, a ventral furrow over the whole body, test-tubes, whose diameters were not necessarily and the presence of29 setigerous segments indicated the same, so as to have similar sedimentation it to be Armandia lanceolata Willey 1905,

Journal of Coastal Research, Vol. 2, No.3, 1986 300 Bhaud

Table 1. Comparison of the catching power of the (B) A further observation concerning this family two plankton nets. a concerns the actual presence of Ammotrypane aulogaster in the Noumea lagoon. RULLIER (1972) (A) SS IVb cm3 biomass after 24 hrs f:!.c discovered this species in the collection of Plessis 300 J-Lm (FCO) 200 J-Lm (WP2) and Salvato It could be argued, however, that the -12 A 17 15 animals in question probably do not belong to the B 65 72 +10 C 145 160 +10 species cited, for the following reasons: (a) Accord­ D 42 47 +11 ing to PERES (1959), the distribution, both geo­ E 70 76 + 8 graphic and bathymetric, shows thatA aulogaster F 18 22 +20 is ofcold temperate type, and in the Mediterranean (B) Stations Chaetosphaere larvae it is never littoral; and (b) DAY and HUTCHINGS III 3 180 60 (1979), HUTCHINGS and MURRAY (1984) did not IV 12 600 50 report this species in their list of annelids asso­

3 ciated with New Zealand, Australia and the South­ 8(A) Sedimented volume (cm ) obtained from 6 running com­ parisons. The difference between the nets (f:!. = WP2 - FCO) is Western Pacific. Thus, ifthe geographic and bathy­ expressed relative to their mean value. (B) Number of chaeto­ metric distributions of A aulogaster reflect the sphaeralarval type (Spionidae) counted at stations III and IV, in ecological characteristics as they should, the spe­ the direction of Amedee Lighthouse. bSuccessive samplings at station IV. cies must be excluded from the intertropical littoral cf:!.% = f:!. x 100/(WP2 + FCO/2). zone. Comparison of biogeographic and ecological data must not be overlooked; Laubier commented that annelid material seems able to undergo a real Table 2. Variation during a 24-hour period in collection of the speciation, from ecological and biogeographic cri­ Opheliidae Annandia lanceolata8 teria, which indicates a different range (LAUBIER, Days Hours Abundance 1966, p. 242). 26-ffi-79 19.5 70 26-ITI-79 20 420 Family Chaetopteridae 40 26-m-79 21 RULLIER (1972) reported finding members of 26-ITI-79 21.5 510 26-Ill-79 22 60 this family in samples. His observations, however, 27-Ill-79 6.5 20 were based on onlyone specimen andfour damaged 27-III-79 7 5 fragments of Phyllochaetopterus major Claparede, 20-1II-79 9 0 1868. In the present study we found three categories 3-IV-79 9 0 6-IV-79 9.5 0 oflarvae in the plankton belongingto this family. (a) 6-IV-79 16.5 5 The larvae in the first category possessed9 bundles 6-IV-79 17 5 of enlarged, lancet-shaped bristles, at the distal 8Collected close to Maitre reef; net WP2 towed for 5 minutes to end; the fourth setiger had bristle on the anterior windward region cutobliquely in a triangle with no teethatthe edge. In addition the larvae had two tentacles, a previously pointed out by RULLIER (1972). The two-part ventral glandular shield, a single ciliary largest specimens were 12 mm long, with the most crown, and seven groups of small triangular uncial frequent size between 4 and 6 mm. The large ones plates, reaching 12 p.m at their greatest length. The were therefore similar in size to the seven specimens form ofthe specialized bristle is reminiscent ofthat collected from a benthic survey by SALVAT (1964) of Spiochaetopterus. No further identification was and examined by RULLIER (1972): four specimens possible because no adult forms were collected; of 15 mm, and three of 13,11, and 6 mm, respec­ however, S. costarum (Claparede, 1870) is known in tively. It would be of interest to know why these the Cookand SolomonIslands (GIBBS, 1971,1972). adult individuals had left the bottom in order to (b) The larvae in the second category belonged to follow, at least temporarily, a planktonic mode of the species Mesochaetopterus minutus Potts, 1914, life (Table 2). Such a migration does not seem to be many of whose benthic stages in their sandy tubes related to reproduction, because the individuals were collected near Croissantreefata depthof1 m. were not sexually mature. It seems more likely that This species is known in the Cook Islands (GIBBS, a diurnal behavioralrhythm as described by several 1972) and Hawaii (BAILEY-BROCK, 1979) and from authors (DARO, 1979; OHLHORST, 1982; RENON, Australia to Japan (DAY, 1967; HUTCHINGS and 1985) accounts for these catches. MURRAY, 1984). (c) A third larval category found in

Journal of Coastal Research, Vol. 2, No.3, 1986 JUl

equal numbers inside and outside the lagoon had a fonn known as chaetosphaera, a tenn used for the first specialized bristle on the fourth setiger corres­ time by HAECKER (1898). This tenn applies to lalvae ponding to the form already described (BHAUD, which have a very pronouncedtendencytoroll upinto a 1983) for Phyllochaetopterus verrilli Treadwell, 1943. ball when they are disturbed orintroduced into a fixing bath The bundles of bristles stick out from their Family Terehellidae bodies, which then take on the appearance ofa sphere Only one species of this family was collected in bearing radial spines. A more detailed description can the lagoon, Loimia medusa Savigny, 1818. It was befoundinBHAUD, 1986. Ofthe types described, type well represented by pelagic larvae that strongly 4 was the one for which the largeststages with the most resembled the larva of Lanice conchilega Pallas, segments and well-fonned parapodia bearing definite 1766. In both cases the larvae, which are known as bristles and hooded hooks were collected 'The classi­ aulophores, occupy a transparent funnel, although fication ofthese larvae as members ofthe Spionidae is some differences were evident. 'fhe most fun~ notin doubt However, itis necessary to go further and damental of these was in the shape of the uncial to compare them with 19 genera reported by BLAKE plates. The uncini are avicular with three and then and KUDENOV (1978) off south-east Australia. The seven hooks ofdecreasing size rising above the ros­ relatively small difference in latitude of about twelve trum inL. conchilega but are pectiniform and bear a degrees suggests a markedfaunal relationship between simple series of five or six teeth in L. medusa. This this region and New Caledonia In view of the pros­ difference was clearly visible even in the youngest tomial point definitely observed on four types des­ stages collected with the plankton net. Another dis­ cribed, these can be classified in genera with a pointed tinguishing characteristic was in the shape of the prostomium in the adult Scolelepis, Dispw, Austrolos- primordial tube which had a clearly angular cross­ pio and Aonides. For this last one we have the data of section in the case ofLoimia (Figure 2). The obser­ HANNERZ, (1956) concerning the larval stage, and vations of THORSON (1946) and those of HEIMLER there does notseemto beany correspondence with one (1981) on Lanice failed to detect this. Larvae pos­ or other of the types collected during this program. sessing another shape offunneL namely a gelatinous In the Noumea regio~ HULLIER (1972) reported six barrel secreted around the larva were collected. species of Spionidae: Spio multioculatn Rioja 1918, This portable burrow, larger than the primary one, Spio aequalis Ehlers 1904, NerinE cirratulus Delle is built when larvae are disturbed as HAMNER et aL Chiaje 1828, PrWrwspio caspersi Laubier 1962, ?rio­ (1975) have observed. The shape ofunciniis similar rwspio capensis McIntosh 1885, and Microspio mecz­ to that of uncini of larvae occupying angular tubes. nikowianus Claparede 1868. It should be noted that if Finally, all these larvae, collected in the present the presence ofN cirraflllus is confinned in the lagoon, program and examined with a microscope, posses­ it should be possible to predictthatone ofthe fonns of sed plates with pectiniform characteristics. There­ chaetosphaeratype describedinthe lagoon shouldalso fore, only the species L. medusa is found in the be found in the Mediterranean or the Atlantic Ocean, region. L. medusa is also the only species men­ taking into account the large representation of this tioned by RULLIER (1972) inside the lagoon, while species. While the larval stage of this species is well L. conchilega is collected from several places in the known and has often been described it was not obser­ Pacific Ocean (HUTCHINGS, 1977; DAY and ved in plankton samples from Noumea Furthennore, HUTCHINGS, 1979; HARTMANN-SCHRODER and none of the six species reported by RULLIER in 1972 HARTMANN, 1979). WILSON (1928) showed clearly were found by BLACK and KUDENOV (1978), that both species of Terebellidae with aulophore HUTCHINGS and MURRAY (1984) off south-east Aus­ larvae were present off the coast of Europe. How­ tralia although they recorded 71 species of Spionidae, ever, the form of the tube that he reported for ofwhich 46 were previously undescribed This leads to Loimia does not correspond with that observed in two conclusions. Firstly, the widely distributed species the Pacific and this difference suggests that further are probably less common than old faunal lists suggest observations are required from european coastal and secondly, thata faunal detailed study ofthe lagoon areas. is likely to be particularly rewarding. Family Ctenodrilidae Family Spionidae Some data on a relatively rare fonn of polychaete In this family larval group were ofmajor interest. armelid, the adult fonn of Cterwdrilus paucidentatus The collections of plankton in the Noumea lagoon Ben-Eliahu, 1976 often mistaken for a larval stage, contained six new types of larvae belonging to the were obtained from samples taken at the periphery of

Journal of Coastal Research, VoL 2, No.3, 1986 302 Bhaud

D· 300llm . , ... , ... '.- .t;.... ~ ~; .. 1#'1'" - , -. ~i . (, '". • ;' ." .- • •

Figure 2. Aulophore planktonic I8.IVa ofLounla medusa: morphology of the funnel and of uncial plates. (A) Lengthwise and (B) cross see­ tionofLhe funnel; (C) uncin~ (O) • different morphology ofthe tube not as frequently collected as those shown in A or B; the l8.IVae sheltered in these tubes bear the same uncini as in C; this is a mucous tube with no clear consistency and is probably a substItute lUbe.

•Journal of Coastal Research. Vol. 2. No.3, 1986 Meroplanktonic Larvae, Noumea Lagoon 303

Maitre reef (Table 3). The body was short, 1.5 mm warm season as distinguished by increasing nut­ and wide, 0.3 mm with at most 9 segments. The rients in the lagoon waters and a cold season with blunt, rounded prostomium was ciliated onthe ven­ minimal intake of fresh water. tral surface. The pharyngial bulb was reversible. At this stage of the investigation it is reasonable There were no palpi, gills, or parapodia. The bris­ to say that the region is characterized, not as are tles were simple and all similar, inserted directly temperate zones, by two groups of species with into the tegument. The neuropodial and notopodial their own periods of reproduction, but by a single bristles each had 4 or 5 teeth; the proximal tooth, group of species whose reproduction centers around the one closest to the base of the bristle, was the the months ofMarchand April. The situation there­ strongest; the shaft described a very definite curve. fore resembles that ascribed to the north-west of This description corresponds exactly with that of Madagascar (BHAUD, 1971). Ctenodrilus paucidentatus by BEN-ELIAHU (1976) based on material collected in the GulfofEilat (Red Comparison ofDay and Night Catches Sea). The presentcollection increases considerably This series of samples is part of those obtained the geographical distribution range of this species. close to Goeland reef. Table 5 shows a comparison Besides the annelids, there were two groups well offour daytime and four nighttime samples. There represented in plankton samples. Many brachiopod were no apparent differences between the two types larvae, collected inside the port of Noumea belong of catches in contrast with the findings of other probably to Lingula anatina Lamarck, of which authors (MCWILLIAMS et al., 1981; WILLIAMS et al., large settlements are known in the Dumbea bay 1984; OHLHORST, 1982; ALLDREDGE and KING, (EMIGetal, 1978) and the shore ofNoumea penin­ 1985). This is not particularly surprising when one sula (Thomassin, pers. obs.). Larvae of entoproct considers the shallowness ofthe zone sampled and bryozoa (JAGERSTEN, 1964; NIELSEN, 1971) are the roughness of the water. Any tendances of the collected in substantial numbers reaching up to 50 larvae to rise to the surface during the night or day per standard sample. would have been overwhelmed by hydrodynamic forces. On the other hand, juvenile Opheliidae and Spatial and Temporal Variations adult Armandia lanceolata do display diurnal dif­ ferences. In the lagoon-reef complex it seems es­ Seasonal variations, temporal comparisons over sential to distinguish between benthic fauna which, 24 hours, spatial comparisons for a series ofcoastal at dawn or dusk, is capable of a change of ecosys­ tows, and results from several tows outside the tem, and planktonic fauna which may be concen­ lagoon are examined in this section. trated near the surface or bottom. However, for the later, the tendancyto display this migration is weak, Seasonal Variations considering the limited depth of the water column. These were studied using samples taken with the For future investigations we must take into con­ FeD net300 /lm size mesh, the results may be selec­ sideration thatthe samplingmethod by sub-surface tive insofar as different larval categories may not horizontal tows occuring several times in 24 hours have been retained equally. However, even when a do not allow for vertical migration of larvae, when larval category is poorly represented, some impor­ several parameters such as wind speed, roughness tance may be attached to its presence or absence. of the water and towing level relative to the bottom Thus the data in Table 4 suggest that the year may are unknown. be divided into two parts: from December to June (winter and spring, which is richer with respect to Comparison of Coastal Catches both number of species and individuals) and from Despite the richness in phytoplankton of this July to November (summer and autumn). This internal neritic zone, which may be a major factor in point is confirmed by analysis of the variations in clogging the net, the samples were particularly rich the commonest categories: Poecilochaetidae, Spi­ in larvae with respect to their absolute number and onidae with chaetosphaera larval type and Spioni­ in juvenile stages if one considers their size. How­ dae of the genus Prionospio, which all showed clear ever, the number of larval categories was clearly seasonal modulation, with a decrease in numbers less than generally obtained in the rest of the lagoon from July to October. BINET (1984) in his study on A high number ofjuvenile stages from only a small planktonic copepods of the Noumea lagoon des­ number of families is characteristic of a source zone. cribes this seasonal variation between a rainy and The well represented families, usually in limited

Journal of Coastal Researc~ VoL 2, No.3, 1986 304 Bhaud

Table 3. Catch of Ctenodrilus paucidentatus, close to Maitre Sampling Outside the Lagoon 8 reef; net WP2 towed for 5 minutes to windward The four samples taken on3 and 4 April 1979 in the open sea, La Sarcelle straits, provided categories of Days Hours Abundance latvae that were interesting due to their large sizes. 29-111-79 22 h 2 These lalvae belonged to the families Spionidae, 29-1II-79 22 h 30 2 Terebellidae, and Amphinomidae. Besides the size 6-IV-79 22 h 30 4 30-III-79 8 h 30 8 which was larger than the lmvae inside the lagoon, 6-IV-79 9 h 30 5 development was also more advanced because they

8These adult individuals have no possibilities for swimming. The had many segments, adult bristles had appeared, and collection in the water column and the slight variations are mainly the anteriorregion was well fonned Inreturn, the ven­ due to the roughness of the water and the shallow bottom. tral ciliated rings and the pygidial trochus of the Spionidae were still present and particularly well developed The adult characteristics present allowed numbers at each station, were Sabellariidae, precise identification of one of these types of chae­ Amphinomidae and Spionidae, the last being rep­ tosphaera Such individuals still bore the lmval bristles resented by type 4 chaetosphaera and Prionospio already 0 bseIVed on the type 4 chaetosphaera collec­ larvae. ted inside the lagoon These bristles were dorsal and

Table 4. Monthly distribution of invertebrate larvae in Noumea reef lagoon

Families & Genera Collected JAN FEB MAR APR MAY .JUN JUL AUG SEPT OCT NOV DEC

Ap hroditidae 17 7 12 4 8 4 5 2 2 6 1 18 33 Amphinomidae 2 6 10 4 Nereidae 5 1 2 3 0 0 2 3 0 1 Terebellidae 26 6 2 3 8 6 1 I') 6 5 3 Poecilochaetidae 11 5 20 5 4 8 4 32 17 1 5 1 Magelonidae 18 5 2 5 3 3 3 8 2 5 1 2 Spionidae Microspio 2 12 2 6 4 1 8 2 3 Prionospio 4 8 1 8 4 8 10 6 5 6 1 2 5 4 ChaRtosphaere 150 70 80 70 35 15 2 6 2 6 30 40 14 1~~0 ~JOO 20 75 35 2 11 4 2 75 30 Polydora 2 1 12 14 4 3 10 2 14 5 2 4 20 12 1 6 5 8 Other Spionidae 4 25 14 18 2 8 15 5 2 10 12 5 ~ 15 5 6 13 5 Chaetopteridae MesochaRtopteros 6 10 4 6 0 5 1 2 2 1 7 2 2 1 2 SpiochaetoptRru.', 1 1 4 2 Sabellariidae 2 3 8 2 Other Groups Sipunculida 4 2 6 2 4 3 1 3 2 1 1 2 Nemertini: Pillidium 2 5 Plathelminthes 5 1 4 1

RStation IV; net FeO: 300 J..Lm mesh size; bottom at 25 m and samples taken at the surface. The whole samples were sorted and the figures were not rounded Meroplanktonic Larvae, Noumea Lagoon

Table;L List of Annelid larvae in the diurnal and nocturnal samples taken close to Goeland reef

Abundance of Larvae Night: 9 t.o 10.IV/79 Day: 10.IV.79 Families & Genera Collected 20 h 4f> 21 hl.S o h If) o h 45 11 h 11 h :30 14 h ;~O 15 h

(A) Larvae Ap hroditidae 270 100 25 f> 10 5 10 ;~O Amphinomidae () 6 2f> f) 10 5 10 ;~O Nephtyidae 14 0 0 0 i) 0 0 Phyllodocidae 5 5 0 5 0 5 0 0 Nereidae [j ;) 1 0 2 0 0 0 Hesionidae 0 ;) 2 0 [) 0 0 f) Terebellidae 20 15 ;) f) 15 12 20 ;1f) Poecilochaetidae 25 10 0 :) 10 15 :~S 4;) Magelonidae 0 0 0 0 0 0 ,S Opheliidae 0 0 () 0 0 0 0 Spionidae Microspio I;') 20 f) 0 4 0 ;) 20 Laonice ;) 0 0 () 0 f) 0 0 Prionospio 20 f) 0 2 20 If) 5 !) Chaetosphacre I 50 ;) 10 0 f) f) ;) 0 2 10 () 0 ;) ;') ,S 10 15 4 {)()() 120 20 If) 15 15 IS 15 :l!) 10 20 If) {) 0 If> })olydora 40 If) ;) f> ;) 0 10 25 Other Spionidac 2[) 20 If) 20 20 ;W 20 25 Chaetopteridae Mes()chal'lop{('ru.'i 0 0 () ;) [) 0 0 ;) Spioch(lc!op!eTus 0 () 0 () 1 0 0 !) Sahellariidae 0 () 0 0 0 0 0 0 (B) Juvenile Syllidae ;) 10 ;) )0 0 () ;) 0 Phyllodocidae 0 () () () () 0 ;) 0 Chrysopetalidae ;) 0 0 () 0 0 0 () Opheliidae ;') 10 )0 10 0 0 f> 0 ~ephtyidae 0 S 0 () f) 0 0 0

<1Five minutes of towing; one quarter of t he sample; numbers are rounded up or down to the nearest five. cwved in a wide hook at their distal end Despite the dif­ larva. The length of the planktonic mode of life is ference in arrangement of these bristles, it is highly not an intrinsic character of the species but de­ probable that the type 4 chaetosphaera described pre­ pends strongly on external circumstances. It is not viously is an early stage compared with those collected surprising that there was frequently a marked con­ outside the lagoon In the latter, the following adult trast between the data derived from neritic and characters were recognizable: anteriorly pointed pros­ oceanic regions concerningthetime spent in the lar­ tomium and frrst setigerous segment without gills. Ifthe val phase. The example ofthe Spionidae larvae with genus Aonides, whose larvae were studied by Hannerz a prostomium drawing into a pit was not the only and are different from those described here, is elimj­ one for which large larvae are collected in the open nated, it is possible to considerthe chaetosphaera type 4 sea. The same applies for larvae Rostraria (Amphi­ as belonging to the genus Sco!Rlepis, using the key to nomidae) or the Terebellidae Loimia medusa. This genera of Spionidae given by BLAKE and KliDEl\'OV hypothesis concerning length of planktonic larval (1978). Assuming that the larvae of the open sea do life is not easily reconciled with an adaptative indeed belong to the same species as in the lagoon, such strategy taking into account precompetent and a catch raises the following question, .. Why are the lar­ competent periods of development as suggested by vae collected from the lagoon waters at a less advanced tJACKSO~ and STRATHMA~ (1981). stage of development than those from out~ide?" The Such a spreading pattern is definitely not pecu­ answer probably lies in their likelihood of encountering liar to the meroplankton ofthe lagoon in south-west sedimen~ which is greater inside the lagoon than out­ New Caledonia and suggests the concept of a source side. This being so, metamorphosis seems not to be lin­ zone. It involves spatial, temporal, and taxonomic ked to a particular stage of development reached by a aspects; in a given place there is not only one species

,Journal of Coastal Research, Vol. 2, No.3, 1986 306 Bhaud acting continuously, but different species in re­ variation of individuals between species. Thus, productive phase, producing broadcast larvae at with 4 indices (number of species, number of indi­ differenttimes ofyear. A source zone is marked by a viduals, diversity and equitability index) it is poss­ very strong numerical inequality in the species rep­ ible to specify the distance of the larval population resented in only one sample and total number of sampled from its origin (Table 6). individuals varying markedly from one sample to the other. Further away, there is maximum diver­ sity, with relatively little numerical variation be­ CONCLUSIONS tween species, between and within samples. After this intennediate zone, in the true dispersion zone, This preliminary investigation on material of there is a decrease in the number of species rep­ benthic origin was conductedatthe end ofthe warm resented. These three zones lie in a neritic area. season, during autumn in the southern hemisphere The peripheral zone, in an oceanic area, is charac­ and is therefore not a complete record of seasonal terized by the particularly large size of the larvae, changes in the reproduction of adults. It is difficult with a particularly low number of species represen­ to make valid comparisons between various geo­ ted and in each sample a relatively small numerical graphic areas (several points in the lagoon, or from

Table 6. Comparison of sub-surface sampling plankton from different origins8

Families & Genera Collected Bl B4 BB BI0 Ab Bb StraitsC Aphroditidae 20 10 36 10 Amphinomidae 60 44 26 40 12 Nephtyidae 8 Phyllodocidae 20 10 Nereidae 0 6 Hesionidae 12 6 8 Terebellidae 24 24 12 20 66 6 Paecilochaetidae 180 124 6 Magelonidae 24 8 28 Opheliidae 12 36 Spionidae Microspio 40 80 60 8 Laonice 4 10 Prionospio 64 20 30 320 20 50 Chaetosphaera 88 220 125 164 340 480 Polydora 4 120 260 180 Other Spionidae 40 120 6 124 80 130 15 Chaetopteridae M esochaetopterus 16 16 30 Spiochaetopterus 18 22 Phyllochaetopterus 8 Sabellariidae 160 1,520 18 64 Ctenodrilidae 6 Cirratulidae 8 4 Chrysopetalidae 12 Eunicidae 8 Sipunculida 12 Nemertini: Pillidium 48 140 20 8 Plathelminthes 20 40 36 28 30 Brachiopoda 80 40 2 Bryozoa 60 20 18 24 Tornaria 14

Number of Species: S 10 10 5 12 25 21 9 Number of Individuals: N 532 2,244 201 940 1,198 1,444 102 Diversity Index (Shannon): Is 2.809 1.790 1.644 2.867 3.289 3.409 3.05 Equitability (ls/Log~S): E 0.846 0.122 0.709 0.800 0.709 0.777 0.965 8B1, B4, BB, and BI0 are for the internal neritic zone with a bottom depth lower than 10 m (2 April 1979). bReef Maitre - station located in the center of the lagoon, 20 m depth (6 April 1979: 15 h 30 and 16 h). cLa Sarcelle straits - station in the south-east of the New Caledonia reef (3 April 1979). All figures from five minute tows.

Journal of Coastal Research. Vol. 2, No.3, 1986 Meroplanktonic Larvae, Noumea Lagoon 307 inside to outside the lagoon) or between samples at conditions and water parameters (neritic part with a single point, because only one sampling techni­ soft bottom in the inner lagoon where estuaries and que, horizontal surface towing, was used while two bays open; oceanic part with hard corallian or uncontrolled factors, roughness and depth of the coarse, soft bottom in the outer lagoon) make it water, could cause variations in the quantity of possible to locate source zones for various species. faunal material of benthic origin liable to be collec­ In addition, such a lagoon-reefcomplex may have ted at the surface. In such conditions, oblique tows some use for elucidating the biology ofmeroplankton seem to be most appropriate, despite the dif­ larvae carried outside the lagoon. Two questions ficulties encountered when the depth is not con­ related to larval behavior may be raised. Does the tinuously controlled. This investigation therefore factorofdistance from any neritic zone increase the remains mainly qualitative and the following points duration ofthe planktonic mode oflife? Do such lar­ should be emphasized Examination of larval plank­ vae retain their capacity to metamorphose? The ton appears to be a good technique for studying island situation seems to be ideal for testing such fauna (BHAUD, 1966 b; THIRIOT, 1969). Certainly, hypotheses. In conclusion, its geographical posi­ since FAUCHALD (1976) stressed the need for more tion makes this area a valuable point of comparison intensive investigations on tropical poly­ for understanding certain problems especially those chaetes some progress has been made, e.g. WARD presently under dispute such as the localized or (1981) for Hawaii; BLAKE and KUDENOV (1978), cosmopolitan characterofthe distribution ofspecies, HUTCHINGS and MURRAY (1984) for the south-east the importance of climatic parameters on phe­ of Australia However, information about the marine nomena of reproduction and the degree of intra­ fauna around New Caledonia is still inadequate. By specific variability in reproductive strategy. comparing RULLIER's list (1972) and the present larval survey, it appears that several species are ACKNOWLEDGEMENTS new for the region; for Spionidae: five species ofthe genus Scolelepis or the closely related genera Aus­ I thank B. Thomassin, who organized this col­ tralospio and Dispio; one species ofMicrospio; one laboration, and the local authorities of the ORSTOM species ofLaonice; for Sabellariidae: one species of (Oceanographic department), for the facilities pro­ Sabellaria; for Chaetopteridae, three species: vided before and during the stay. I am grateful to D. Spiochaetopterus costarum (Claparede), Phyllo­ Binet and B. Thomassin for reading this manu­ chaetopterus verrilli (Treadwell) and Mesochaetop­ script and suggesting many improvements, and to terus minutus (Potts), and for Ctenodrilidae: M. Grisley, Aberdeen for his help with preparing Ctenodrilus paucidentatus (Ben-Eliahu). the English manuscript. Some features in our data however, indicate that not all categories of larvae known to exist in the LITERATURE CITED lagoon were actually collected. Certain families, i. e. Aphroditidae, Nephtyidae, Phyllodocidae, and Hesionidae, were absent or very poorly represen­ ALLDREDGE, A. L. and KING, J.M.,1985. The distance ted at the time of sampling. Also, Amphictenidae demersal zooplankton migrate above the benthos: laIVae were not collected when RULLIER (1972) implications for predation. Marine Biology, 84, 253­ 260. noted three species in this family. Thus, itis evident BAILEY-BROCK, J.H., 1979. Sediment trapping by that only three months sampling is too short a period chaetopterid polychaetes on a Hawaiian fringing reef. to give a complete picture of seasonal reproduction Journal ofManne Research, 37(4),643-656. and a thorough study of both benthic and planktonic BEN-ELIAHU, M.N., 1976. Polychaete Cryptofauna from Rims of Similar intertidal Vermitid Reefs on the fauna is still needed. Mediterranean Coast of Israel and in the Gulf of Elat Besides offering further information on the local Sedentaria Israel Journal of Zoology, 25, 121-155. fauna, the Noumea area and its coral reef has cer­ BHAUD, M., 1966 a. Les larves d'Annelides Polychetes tain advantages for the development of models of Banyuls-sur-mer. Ecologie et developpement. These doc. 3eme cycle; Univ. Paris VL 156 pp. multigr. larval dispersion. The low dilution makes it poss­ BHAUD, M., 1966 b. Les larves planctoniques d'An­ ible to obtain much higher concentrations of larvae nelides Polychetes: leur interet pour une meilleure con­ than those found in neritic regions in direct com­ naissance faunistique. Vie et Milieu, 17 (1 B), 435-437. munication with the open sea (BHAUD, 1971; BHAUD, M., 1971. Aspects systematiques et biogeog­ raphiques de l' etude des larves planctoniques d' An­ CAZAUX, 1970; GUERIN, 1972). The asymmetry of nelides Polychetes. These doct. es Sci, Univ. Paris VI: the lagoon with respect to the nature of bottom 464 pp. multigrad.

Journal of Coastal Research, Vol. 2, No.3, 1986 308 Bhaud

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