TECHNICAL REPORT NO. 1973 FISHERIES RESEARCH BOARD OF CANADA Technical Reports FRB Technical Reports are research documents that are of sufficient importance to be preserved, but which "for some reason are not appropriate for primary scientific publication. No restriction is placed on subject matter and the series should reflect the broad research interests of FRB. These Reports can be cited in publications, but care should be taken to indicate their manuscript status. Some of the material in these Reports will eventually appear in the primary scientific literature. Inquiries concerning any particular Report should be directed to the issuing FRB establishment which is indicated on the title page. FISHERIES RESEARCH BOARD OF CANADA TECHNICAL REPORT NO. 420 MARINE AND BRACKISH WATER OLIGOCHAETA by R. O. Brinkhurst This is the sixty-fourth FRB Techpical Report from the Fisheries Research Board of Canada, Biological Station, St. Andrews, N. B. 1973 MARINE AND BRACKISH WATER OLIGOCHAETA by R. O. Brinkhurst Biological Station, St. Andrews, N.B. ABSTRACT While there are marine and brackish representatives of most families of oligochaetes, the majority of species are to be found in the Tubificidae and Enchytraeidae. Zoogeographic distribution varies from cosmopolitan to highly endemic, with other patterns (pan-Atlantic; pan-American; European including Mediterranean and Black Sea for example) that may prove to be of significance. Ecologically, most oligochaetes tolerate wide ranges of temperature and salinity. Some correlations between worm distribution and particle size can be observed. Oligochaetes are usually found in multi-specific clumps, and recent work demonstrates positive interactions in which mixed cuItures move and respire less, eat and grow more than the same individuals in isolation. Niche discrimination is probably related to specific food requirements, often the faeces of other worm species being a preferred food source. -2- Systematics In my classification of the oligochaetes (Brinkhurst and Jamieson 1971) two of the three orders contain no salt­ water species (Moniligastrida, Lumbriculida) but the larger Haplotaxida has several families with brackish and marine species. Some representatives of families such as the Haplotaxidae and Phreodrilidae occur in coastal or insular situations where one suspects that some salt tolerance is possible, but the original descriptions make only passing reference to the nature of the localities - often mentioning only the name of the nearest settlement. These families in particular include ground-water species which may also be tolerant of water laden with various salts. In the large aquatic families, the Nai~idae and Tubificidae, many cosmopolitan species may penetrate slightly brackish water (Chaetogaster spp., Uncinais uncinata~ Nais communi8~ N. val'iabilis~ N. elinguis~ Stylal'ia lacustris~ Dero pectinata~ Pristina plumaseta~ Limnodrilus hoffmeisteri) but many species are restricted to brackish water and marine localities. Most subfamilies of the Tubificidae contain saltwater species, but the Pha11odri1inae and C1itellinae are predominantly saltwater forms. The largest genus in the Tubificidae (Peloscole%~ Tubificinae) contains several saltwater species, and the genus Monopylephol'us (Rhyacodrilinae) is dominantly but not exclusively marine or brackish. Guides to the identity of marine oligochaetes include publications by Brinkhurst 1966, 1971a,b; Cook and Brinkhurst 1973, and -3- In press. Recent studies on the Enchytraeidae have expanded the list of saltwater species in that family considerably (Lasserre 1971a,bl. For the purposes of this paper I have ignored the small number of aquatic megadriles (Suborder Lumbricina) • Zoogeography and Ecology of the Tubificidae and Enchytraeidae The true zoogeography of many saltwater and estuarine Tubificidae has yet to be determined as most are minute and easily overlooked when much of the invertebrate fauna is large and conspicuous. One can feel fairly certain that species such as Tubifex costatUB and Thalas8odrilu8 prostatu8 are restricted to Europe, whereas Pelo8colex heterochaetus, P. benedeni, Clitellio arenariu8# C. arenicolu8, Tubifex pS8udogaster,l T. nerthus (if T. newfei is a synonym), Pha 1,. z.odri z.us monospermathecus,l Spiridion insigne among the tubificids are circwm-north Atlantic and may extend into the Mediterranean and the Black Sea. Other species are only known from N. America, and whereas some are recorded only on the east coast (Tubifex Zongipenis,l Isochaeta hamata,l Pez.oscoZex dukei,l P. intermedius,l P. acu z.eatus,l Pha 1,. z.odri z.us coe z.opros tatus,l P. parviatriatus,l P. obscurus,l Adez.odriz.us anisstosus), others seem to be pan-American (Pez.oscoz.ex apeotinatus,l P. nerthoides,l P. gabrieHae). Three species of Monopylephorus (N. rubroniveus,l M. parvus and H. irroratus) are, in my view, cosmopolitan -4- as the supposed differences between species originally reported from Europe, America, Africa, Asia and Australia become insignificant when enough material is examined. Detailed studies of saltwater oligochaetes will undoubtedly reveal more of these errors in the future. Records of families other than the Tubificidae may suffer even more from lack of detailed attention. Recent work by Lasserre on the Enchytraeidae of the east coast of N. America demonstrates that many common European forms can be found elsewhere. Eleven of thirteen species reported were previously known only from Europe. The two other species, both hitherto undescribed, were found in the collections from Cape Cod but they were not found in the North Carolina material. While the older literature on saltwater oligochaetes is full of firm statements about the distribution of various species in relation to salinity, few if any of these claims have been substantiated experimentally and the salinity ranges quoted for a given species in different localities do not always coincide. More recent work suggests that oligochaetes can withstand wide ranges of ecological conditions. Lasserre (197la) has shown that Marionina (Enchytraeidae) species have temperature and salinity tolerance ranges of at least 25° and 15%0 and oxygen consumption was constant in two of these cosmopolitan forms over their normal range of these factors. However, zonation in the distribution of meiobenthic species -5- has been demonstrated (Lasserre 1971b) and while one LumbricittuB species demonstrates a salinity preference in the laboratory, a second one shows no preference across a range from distilled water to 150% sea water of osmotic pressure 22.5 atmospheres (Tynen 1969). Quantitative approaches to the delineation of associations of benthic species are now being used extensively. In freshwater studies, Johnson and Brinkhurst (1971) demonstrated four widely overlapping communities in a part of the St. Lawrence Great Lakes system using the measures of coefficient of community and percentage similarity of community. In a similarly intensive and extensive survey of Cape Cod, Cook (1971) mapped oligochaete distributions in relation to particle size and depth and detected two nonoverlapping species associations (i) the fine sand/silt group (Peloscolex intermedius and Limnodriloides medioporus) and (ii) a coarse sand group of eight other species. Within association (i), analyses of sediments in terms of percent sand, silt and clay, were compared with the distributions of P. intermedius and L. medioporus, considerable overlap in the distributions of the two species being observed. In the other group, two species are thought to burrow freely whereas six are small interstitial species. Aquatic oligochaetes characteristically form multispecific clumps in natural sediments and this has been investigated in detail using the freshwater assemblage of -6- worms found in Toronto Harbour, Canada. The three common tubificid species found there interact in the laboratory, so that mixed species cultures respire less (probably moving less) but feed more and hence grow much faster than pure species cultures under the same conditions. Worms can detect water-borne molecules produced by other species as demonstrated by shifts in respiration of one species in the presence of culture water from other species (Chua and Brinkhurst 1973). The worms feed on bacteria, selectively digesting the various strains available and they may even ingest selectively. These three species certainly pick the richest particles from sediment but evidence of different selectivity by different species is lacking. It would seem that one oligochaete species in isolation spends much of its time seeking its preferred food, which may well be the recolonised faeces of another oligochaete species. When mixed together, the worms spend more time feeding, less time burrowing in search of food. In tests of this hypothesis, a significant increase in feeding rate and absorption efficiency was noted in mixed cultures. Moreover, L. hoffmeisteri selected faeces derived from T. tubifex in preference to their own faeces or mud from their native environment. This could provide an explanation of the tight clumping of oligochaetes in natural populations. In multispecific clumps, worms share the resources available, and as they utilize more of the energy content than they do in isolation, one species clearly processes the sediments for the next species t benefit. Highly specific food -7- preferences may reveal more about niche discrimination of worms than continued emphasis on chemical/physical parameters, especially where these are nonspecific