BULLETIN OF MARINE SCIENCE, 45(2): 406-414, 1989

OBSERVATIONS ON SPAWNING BEHAVIOR OF EUPOLYMNIA NEBULOSA, AND COMPARISONS WITH LANICE CONCHILEGA (ANNELIDA, POL YCHAETA, TEREBELLIDAE)

Ralph 1. Smith

ABSTRACT Observations of the spawning behavior of the terebellid polychaete Eupolymnia nebulosa (Montagu) are reported and discussed in comparison with that of Lanice conchilega Pallas. Eupolymnia produces a mucoid egg mass attached to its tube, its larvae lack statocysts, and settle after at most a short planktonic life. Males and females showed synchrony in a spawning peak, but no pairing behavior nor interactive sexual behavior. In contrast, Lanice is a free spawner, its larvae possess statocysts, and pass an extended period planktonic in a mucoid tube before settling.

The polychaete family Terebellidae shows great diversity in reproduction, both in respect to spawning behavior and larval ecology, and to the morphology of the nephromixia that serve in the shedding of gametes. The anatomy of Lanice was beautifully illustrated by Eduard Meyer (1887) a century ago. Internally, Lanice has 4 pairs of highly specialized reproductive nephromixia, those on each side sharing a capacious common duct with a posterior reservoir (Figs. lA, B). Eu- polymnia nebulosa, like Lanice is a typical terebellid, but differs from Lanice in having three genital nephromixia on each side (Figs. 2A, B) with no reservoirs, instead of the four united organs of Lanice. A discussion of the morphology detailed in Figures 1 and 2 and reproductions of Meyer's illustrations will be found in Smith (1988). It is remarkable that systems sharing the same function should be so different in members of the same sub-family. Although Meyer (1887) did not describe the spawning behavior nor the adult nephromixia of Eupolymnia, he followed the development of the larval proto- nephridia and the early stages of the definitive genital nephromixia. Kessler (1963) has beautifully described the embryonic and larval development of Lanice. The present paper reports observations of the spawning behavior of Eupolymnia ne- bulosa, thus helping to fill a gap in our knowledge. Ongoing studies by Bhaud and Gremare (in press) will undoubtedly provide a more complete picture of the reproduction of this species.

MATERIAL AND METHODS

Observations of Eupolymnia nebulosa were carried out in April and May 1986, at the Laboratoire Arago, Banyuls sur Mer, on the Mediterranean coast of France, in the laboratory and with the advice of Dr. Michel Bhaud. Egg masses and specimens of Eupolymnia in their loose, sandy tubes were collected under stones in a shallow, protected, essentially tideless, area near the laboratory, and were maintained in the laboratory in running seawater (SW) under ambient temperature and light conditions. Adult worms of both sexes and all sizes were placed in a large white container supplied with running SW. Worms were distributed randomly into petri dishes, each supplied with a few ml of coarse sand and sheltered by a piece of broken tile. In order to facilitate observation and sampling a more natural habitat was not simulated. In addition to the worms associating freely in the tank, several groups of females alone and females plus a male were isolated in jars of SW changed daily. Further details will be mentioned under "Observations" which, being of a general nature, are necessarily somewhat discursive. Comparative observations of Lanice conchilega. in connection with a study of gameto- genesis, were made at the Dove Marine Laboratory of the University of Newcastle upon Tyne,

406 SMITH: SPAWN INO OF EUPOLYMNJA AND LAN/CE 407

Common d~'~t An'tenor \. t...... '.... .'.....;...... ;./. ".. '."·'c·;-,,,.,.-·.;·',...... " F' •.•.,.... . •...... '~ w~~~h 1. A, Lani" w"hi/, ...... p' - pairs of coelomostomes (CST)~a,. o",nod do=lly •• d _ ostenor '" ,hawo'reproductiveVM no.h'Om"",ymg,adon tthe d0=1 ma~al"arepmned outM' got rem,,"" to ,b 'igh"'.' G,"otrnl t"''' re"~o' ),th, io'a". I ow tbd,iat of . mawa;~' a:',. B,•••Lao'''' di'grn m,~0r(WthirdR), ofandwbicl>fourthonly ';:0.'e antenorof th, partsfont nephromixial units A

Coelomostomes Dorsal muscle (Dorsal parts) V

IV-VI

Figure 2. A diagram of the three reproductive nephromixia of Eupolymnia nebulosa. showing the extensive coelomostomes and the small nephromixial sacs (IV, V, VI). The non-reproductive, inflated, third nephromixial sac (III, function unknown) has been reflected forward. B, frontal section of Eupolymnia through the ciliated funnels (F) of nephromixia V and VI of right side, the sacs of nephromixia IV and V, and the greatly inflated sac of non-reproductive nephromixium III lying in its normal position between reproductive nephromixia and the gut. LMG, lateral thoracic mucous glan- dular epithelium; CST, coelomostomic component of ciliated funnels; NST, nephrostomial component of same; 0, oocyte in coelom; Gut, gut lumen; SB, notosetal bases. SMITH: SPAWNING OF EUPOLYMN1A AND LAN1CE 409

Northumberland, northeastern England, from January through July 1986, unfortunately without spawning being observed.

OBSERVATIONS General. -Female Eupolymnia nebulosa approaching maturity, prior to the pro- duction of the mucoid egg mass, can be readily recognized by the development of a thick white jacket of mucous glands on the sides of the thoracic region. After spawning, the white is largely lost, and the glandular epithelium assumes a trans- lucent grayish appearance. At Banyuls sur Mer, Eupolymnia exhibits several peaks of spawning activity each spring, well-documented by Bhaud and Gremare (in press), and appears to follow the pattern of continuous iteroparous or semi- continuous reproduction, in the terminology of Olive (1984). Jelly masses con- taining orange eggs start appearing, always at night, in "the dark of the moon," or period following full moon, and extending through the third into the fourth quarter. The periodicity is reported by Bhaud to be not quite lunar, successive peaks tending to lag as the season progresses. My observations included one such period, from 27 April to 5 May 1986 (Fig. 3). During daylight hours the worms largely remained concealed but at night wan- dered freely, rather than remaining in their tubes, and also tended to aggregate in groups of two to five, apparently randomly in respect to size, sex, and reproductive readiness. It is not known if they wandered more or less than in nature. Eupo- lymnia glides purposefully by means of its extensive orange, ciliated, tentacles, and faster than any other terebellid I have seen. Worms in the tank were drawn upon for dissection and other observations, an unknown number escaped through leaks in the drain system, and the group was replenished by several fresh collections over the period of observations. At anyone time about 35-40 worms occupied the tank, and were essentially a sample of the local population, under fairly normal day and night illumination and ambient sea temperature. Production of egg masses in the laboratory showed a clear peak corresponding closely to that observed simultaneously in the field by Dr. Bhaud (Fig. 3), indicating that conditions were not too "unnatural." Egg Production and Interaction of the Sexes. -All egg masses produced in the common laboratory tank prior to 4 May contained fully fertilized eggs, but there was no necessary direct pairing or interaction of the sexes at spawning. Exami- nation of fresh egg masses showed active spermatozoa in the jelly, apparently produced by males in the tank the same night. The white bottom and the flowing SW made direct detection of sperm emission impossible. However, one male isolated in a jar with two ripe females did spawn massively one night before midnight, although neither female spawned in response. That the presence of a male is not necessary for female spawning is indicated by the fact that, the same night, an egg mass was produced in another group of three females isolated in a jar without a male, and not supplied with running seawater; these eggs were, naturally, not fertilized. Mr. Antoine Gremare tells me that the spawning of females under field conditions is preceded by the building of a short terminal section of sand-tube directed upward, that no male need be close at hand, that fertilization can occur by sperm in the local water mass, and that males may spontaneously emit sperm in the field without the necessary close presence of a female. My own observations are consistent with those of Gremare and Bhaud. As observations of the laboratory population continued, the proportion of "spent" males and females necessarily increased, despite periodic replenishment from the field (where the same process was occurring). Termination of spawning in the 410 BULLETIN OF MARINE SCIENCE, VOL. 45, NO.2, 1989

.c 70 ~ 7 Lab •

DISCUSSION The production of mucous egg masses by Eupolymnia, provided for by the thoracic epidermal mucous glands, the mobility of males and females that enables them at least potentially to be in proximity at spawning, and the short planktonic or mainly benthic habit of the larva are all consistent with its life in quiet subtidal or tideless waters. Eupolymnia lacks statocysts, and its juveniles emerging from the egg mass soon settle to the bottom (even in the running SW of the laboratory) and construct sand-tubes, much like those of Lanice, but not preceded by plank- tonic life. It should be noted that, according to Bhaud et al. (1987), Eupolymnia SMITH: SPAWNING OF EUPOLYMNIA AND LAN1CE 411

A

Figure 4. Planktonic juvenile of Lanice. living, in mucoid tube, with an empty tube; B, head of same juvenile; C, optical section ofa clean, empty tube, showing layered structure; D, sand tube of juvenile a day after settlement. 412 BULLETIN OF MARINE SCIENCE, VOL. 45, NO.2, 1989

Figure 5. A, frontal section of adult Lanice; S, paired statocysts; NF, ciliated funnels of first pair of non-reproductive nephromixia; I, sacs of same. B, left statocyst, enlarged; C, right statocyst; D, planktonic juvenile of Lanice, showing statocyst (arrow); E, detail of same, the inclusions kept in active motion by cilia lining the cyst. SMITH: SPAWNING OF EUPOLYMNIA AND LANICE 413

nebulosa in the English Channel differs from its Mediterranean presumed con- specific in not producing a mucoid egg mass, but is reported to release its eggs freely into the sea in a single spawning peak. The development of the planktonic juvenile of Lanice in a tube, initially of detritus, then mucoid, has been fully described by Kessler (1963). However, her figure of the mucoid tube does not show the characteristic concentric layering (Figs. 4A-C). The planktonic juvenile is well known and, perhaps derived from elsewhere, is commonly taken off Northumberland from May through September (Romimohtarto, 1980), with a minor peak in June and a major occurrence in August-September. In 1986, juveniles were taken by Dr. Frank Evans on 23-24 June. These were at the three to five tentacle stage, with about 20 setigerous segments, and so may represent a late fall spawning of the previous season. That the occurrences on the 2 days were derived from different stocks is suggested by the fact that the collection of 24 June coincided with a sudden drop in seawater temperature from 10.2 to 8.1°C, and that the largest of the juveniles of the second lot were twice the size of the largest taken on the previous day. They were ap- parently held in the plankton by turbulence, as they sank immediately in still seawater and, when provided with a little sand from a Lanice habitat, at once settled and constructed tubes (Fig. 4D). In all cases the new sand-tube was started by attaching grains to one or other end of the tapered mucoid tube. In La nice, and also in Loimia (Wilson, 1928), but not in other terebellids, a pair of statocysts lies immediately anterior to the first pair of nephromixial funnels (Fig. SA-E). The statocysts of these and other polychaetes were well-described by Fauvel (1907) as "otocystes," and were noted in adult Lanice by Meyer as "Ge- horbUischen." Kessler (1963) figures the larval statocysts of Lanice. Statocysts in polychaetes are generally regarded as indicative of a long planktonic larval life (e.g., Thorson, 1946). In contrast to Eupolymnia, Lanice inhabits strong, fringed, sandy, V-shaped tubes intertidally or sub-tidally on wave-swept beaches, where it would not be expected to leave its tube and, indeed, it shows no locomotory ability. Its juvenile has a long planktonic life, correlated with the possession of statocysts. The role of its large ventral thoracic mucous glands is that of tube-building, a process well described by Seilacher (1951) and Ziegelmeier (1952). There is no evidence that Lanice forms a mucous egg mass. Rather, it releases both eggs and sperm into the water, presumably depending upon synchrony of spawning (Kessler, 1963) to effect fertilization.

ACKNOWLEDGMENTS

This paper is dedicated to the memory of Donald P. Abbott, a student from whom I learned more than he ever did from me. I am grateful for the facilities afforded me at the Laboratoire Arago at Banyuls sur Mer, and most particularly to Mr. A. Gnlmare and Dr. M. Bhaud, without whose advice and helpfulness the study of Eupolymnia would not have been possible. To the staff of the Dove Marine Laboratory, Cullercoats, of the University of Newcastle upon Tyne, I am grateful for much help and cooperation, especially from Dr. F. Evans who supplied Lanice juveniles and from Dr. P. Garwood who shared photographic facilities. To the Department of Zoology at that University I am also grateful, to Mr. R. Hewitt for help with photography and, most of all, to Dr. D. Golding, whose hospitality and assistance were unfailing. This paper has benefited greatly from the critical suggestions of two anonymous referees. The work was partly supported by a faculty research grant and by sabbatical leave from my Department of Zoology, University of California, Berkeley.

LITERATURE CITED

Bhaud, M. and A. Gremare. In Press. Reproduction and development of Eupolymnia nebulosa (Polychaeta, Terebellidae) in the western Mediterranean Sea. Proc. Second Internal. Polychaete Conference, Copenhagen, J. B. Kirkegaard and M. E. Petersen, eds. E. J. Brill, Leiden. 414 BULLETIN OF MARINE SCIENCE, VOL. 45, NO.2, 1989

---, ---, F. Lang and C. Retiere. 1987. Etude comparee des caractt:res reproductifs du Ter- ebellien Eupolymnia nebulosa (Montagu), Annelid Polychete, en deux points de son aire geo- graphique. C. R. Acad. Sci. Paris, Ser. lll, 304: 119-122. Fauvel, P. 1907. Recherches sur les otocystes des Annelides Polychetes. Ann. Sci. Nat. Zool., Ser. 9, Vol. 6: 1-149, PI. I-III. Kessler, M. 1963. Die Entwicklung von Lanice conchi/ega (Pallas) mit besonderer Beriicksichtigung der Lebensweise. Helgol. Wiss. Meeresunters. 8: 425-476. Meyer, Eduard. 1887. Studien iiber den KOfPerbau der Anneliden, I-lll. Mitth. Zool. Station, Neapel. 7: 592-741, PI. 22-27. Olive, P. J. W. 1984. Environmental control of reproduction in Polychaeta. Fortschr. der Zool. 29: 17-38. Romimohtarto, K. 1980. Seasonal and year to year variability in the planktonic larval stages of benthic communities off Northumberland. Ph.D. Thesis, University of Newcastle upon Tyne. 140 pp., PI. I-X. Seilacher, A. 1951. Der Rohrebau von Lanice conchilega (Polychaeta). Ein Beitrage zur Deutung fossilcr Lebensspuren. Senckenbergiana Biologica. 32: 267-280. Smith, R. I. 1988. Mixonephridia or nephromixia in terebellid polychaetes? A clarification. Compo Biochcm. Physiol. 91C: 265-272. Thorson, G. 1946. Reproduction and larval development of Danish marine bottom invertebrates. Medd. Komm. Danmarks Fisk. Og Havunders., Ser. Plankton 4: 1-523. Wilson, D. P. 1928. The post-larval development of Loimia medusa Sav. J. Mar. BioI. Assoc. U.K. 15: 129-148, PI. I-II. Ziegelmeier, E. 1952. Beobachtungen iiber den Rohrenbau von Lanice conchi/ega (Pallas) im Ex- periment und am naturlichen Standort. Helgol. Wiss. Meeresunters. 4: 107-129.

DATEACCEPTED:August 12, 1988.

ADDRESS: Department of Integrative Biology. University of California, Berkeley, California, 94720.