Nemertea inhabiting the Haploops (Amphipoda) community of the northern Øresund with special reference to the biology of Nipponnemertes pulcher (Hoplonemertea)

Abstract

The densities of nemerteans and associated fauna on a soft-bottom sampling station (27-30 m deep) in the 0resund were determined from 47 cores (each 135 cm2 in cross-section; 20 + cm deep) collected from September to December 1989; these data were compared with 14 cores taken from the same location in December 1982. Nine species of nemerteans were identified from cores and dredge samples: Palaeonemertea -Callinera-like sp.; Heteronemertea -Cerebratulus fuscus, C. marginatus, Lineus bilineatus, Micrura fasciolata, M. purpurea; Hoplonemertea -Amphiporus bioculatus, A. dissimulans, Nipponnemertes pulcher. Mean numbers of heteronemerteans were 32 and 10 rn-* in 1982 and 1989, respectively, and hoplonemerteans were 90 and 7 1 m-2, respectively. Only one palaeonemertean was collected during both years. Mean densities of the dominant species, N. pulcher, were similar for the two years, 74 and 68 m -*. The dominant groups of macrofauna (n rn-') in 1989 were ostracods (1028), amphipods (618), polychaetes (514), and ophiuroids (449). Amphipods (> 90% Huploops spp.) and polychaetes (at least 30 spp.) are the major potential prey for hoplonemerteans and heteronemerteans, respectively. Laboratory feeding experiments with N. pulcher revealed that it consumed amphipods (Haploops tenuis and H. tubicolu) at a rate of 2.6 worm-' d-' during the first 12 hours, but after 36 hours and beyond the rate was maintained at approximately 0.2 worm-I d-'. Beyond 12 hours this nemertean showed a tendancy to only partially evacuate its prey. It was demonstrated experimentally that N. pulcher has a supply of toxin capable of killing six amphipods in approximately one hour. Limited tests showed that N. pulcher fed on the cumacean Diastylis tumida, but not on the amphipod Maera loveni or the ostracod Philomedes globosus, and that Amphiporus dissimulans readily attacked Haploops spp., but not Maera or Philomedes. Although the results of laboratory experiments are tentative, they do suggest that suctorial hoplonemerteans can exert a potentially significant effect on benthic communities. Employing seven species of polychaetes as prey for Cerebratulus fuscus and Micrura fasciolata, only the latter responded positively to one of them, Glyceru alba. The hermit crab Pagurus bernhardus violently rejected N. pulcher in all feeding trials.

Investigating isotopic functional indices to reveal changes in the structure and functioning of benthic communities

“…1). This result agrees with previous investigations showing that high densities of amphipods host larger abundances (and biomass) of macrofaunal predators such as polychaetes or large nemerteans (McDermott 1993). Some dissimilarity emerged between biomass-weighted (Hull biom ) and unweighted equivalent indices (IFRic and SEAc).…”

Reproduction ofAmphiporus lactifloreus (Hoplonemertini) on tidal flats: implications for studies on the population biology of nemertines

“…Densities may be as high as 250 individuals / m 2 within these micro-habitats (Thiel & Reise, 1993). The average food requirement of an adult individual A. lactifloreus was estimated from laboratory experiments to be about 0.15 amphipods / day (Thiel, 1992), a value which corresponds with values provided by McDermott (1984McDermott ( , 1993 for another hoplonemertine feeding on amphipods of a size similar to those preyed upon by A. lactifloreus.…”

“…Nemertines are important endobenthic predators in estuarine ecosystems (Roe, 1970(Roe, , 1976(Roe, , 1993Reise, 1985;McDermott, 1984McDermott, , 1993Ambrose, 1991). They may have a significant predation effect on their prey populations (Roe, 1976;Nordhausen, 1988;Rowell & Woo, 1990), or they may provoke prey movements within tidal fiats (Thiel & Reise, 1993).…”

Morphological adaptations of the Cratenemertidae (Nemertea, Enopla, Hoplonemertea) to the epipelagic habitat and lifestyle

“…This substrate provides a firm base from which to push the body forward, making it possible to thrust the armed proboscis forward to stab and immobilize prey (see the elegant feeding studies of McDermott (1975McDermott ( , 1984McDermott ( , 1987McDermott ( , 1993 and McDermott and Roe (1985)). In contrast, the free-floating epipelagic forms have no firm surface against which to push.…”