Free-swimming trophonts of a sessiline peritrich ciliate were discovered in plankton samples from the Rhode River, Maryland, and main-stem Chesapeake Bay. Cultures revealed that the species comprises both free trophonts that swim with their peristomial cilia and sessile trophonts that attach to substrates with a contractile, helically-twisted stalk. Trophonts with a short, rigid stalk or no definite stalk also were seen in culture. Binary fission of free-swimming trophonts usually produced a pair of trophonts attached scopula to scopula by a short, rigid stalk. These persisted for some time as distinctive, spinning doublets before their stalks broke and they separated. Binary fission of free-swimming trophonts also yielded trophont-telotroch pairs that stayed together for only a short time. Telotrochs from these pairs were presumably the source of attached trophonts. Conjugation occurred in both free and attached trophonts. Formation of microconjugants involved at least 2 successive divisions of a trophont. Possession of a helically-twisted, contractile stalk placed the peritrich in the family Vorticellidae, but its unique combination of life-cycle stages marks it as a new genus and species, Planeticovorticellu ,finleyi. The morphology and life cycle of P. Jinleyi raise questions about the present classification of sessiline peritrichs and suggest that it may be at least partly artificial. Stalkless planktonic peritrichs that swim with their oral cilia as do trophonts of P.Jinleyi may have evolved from sessile ancestors by an alteration in the life cycle that created unstable clusters of trophonts on a single parental stalk. Free-swimming trophonts would originate from breakup of these clusters.

Rotifera and Acanthocephala are generally regarded as separate phyla sharing a basal position among triploblast protostomes. This paper presents the first molecular phylogenetic examination of the relationship of Acanthocephala to all three rotifer classes, Seisonidea, Monogononta, and Bdelloidea. Inclusion of Acanthocephala within Rotifera, probably as a sister-taxon to a clade composed of Bdelloidea and Monogononta (the Eurotatoria), is strongly supported by both parsimony and distance methods, using a region of the nuclear coding gene hsp82. Previous molecular evidence for the inclusion of Acanthocephala in the Rotifera suggested that Acanthocephala is a sister-taxon of Bdelloidea, forming the clade Lemniscea. No support is found for this clade, and evidence is presented that the monogonont rotifer used in those analyses, Brachionus plicatilis, may be evolving in an anomalous manner.

Two fluorescent calcium indicators, Calcium Green AM (CG) and Fura Red AM (FR), were used in conjunction with confocal microscopy to monitor hemocyte calcium dynamics following exposure to digenetic trematode larvae or relevant bioactive compounds. Changes in intracellular calcium levels, as measured by fluctuations in the CG/FR ratio, were correlated with hemocyte morphological changes. Hemocytes exposed to culture medium remained spread and had few calcium transients. However, following exposure to sporocysts, sporocyst secretory-excretory products, or small rediae of Echinostoma puruensei in culture medium, significantly more hemocytes both rounded up and exhibited calcium transients, though some hemocytes showed one response or the other but not both. Hemocytes did not respond significantly to large rediae, to sporocysts of another digenean (Schistosomamansoni), or to bacterial lipopolysaccharides. Exposure to either zymosan particles or mannose BSA provoked responses similar to those seen with sporocysts of E. paraensei. Caffeine caused rounding but no calcium transients, and phorbol myristate acetate provoked calcium transients but no rounding. The results show that sporocysts and small rediae of E. paruensei have pronounced effects on hemocyte rounding and calcium dynamics, and that these two events can occur independently of one another. This suggests that parasites may influence hemocytes in at least two separate ways.

Haplotremu concavum, a carnivorous land snail, responds differently to the same prey when hunting versus when transporting food. The ability of these animals to distinguish between fresh, unmanipulated or uneaten prey and manipulated or partially eaten prey was tested by switching prey items while the predator was in the process of transporting the prey. Predators responded to a switch from a manipulated egg of Anguispiru ulternata to an unmanipulated egg by suspending transport behavior while the new egg was manipulated. Seven of ten predators responded to a switch from an egg of A. alternata to a conspecific (H. concavum) egg by stopping transport and abandoning the less-preferred food. Predators responded to a switch from partially eaten hatchlings of A. ulternata to fresh but injured hatchlings by stopping transport after the retrieval stage to eat the new hatchling, after which transport was resumed. Predators which were not engaged in transport behavior attacked rather than retrieved fresh, injured hatchling prey. These results suggest that by manipulating its prey, the predator alters the sensory stimulus of the prey by marking the prey with predator mucus which, in turn, elicits the transport behavior by the predatory snail.

The reproduction and development of symbiotic polynoid polychaetes in the genus Arctonoe were examined with light and electron microscopy. Around San Juan Island, Washington, the 3 described Arctonoe spp. have very similar reproductive periods and ontogenies. Free-spawned eggs 80 pm in diameter fuse with sperm and develop into planktonic, feeding larvae that bear a prototroch, but no metatroch or food groove cilia. Larvae begin feeding only after the development of episphere ciliary bands and an oral brush, consistent with the hypothesis that these structures are involved in particle capture and handling. Metamorphosis occurs in the laboratory in the absence of hosts after 6–12 weeks of feeding and growth. Juveniles begin feeding using the pharyngeal jaws several days after metamorphosis is complete. In the laboratory, worms reach sexual maturity 4–6 months after metamorphosis. The long planktonic larval period of Arctonoe spp. probably leads to high dispersal, suggesting that geographic differentiation in host preferences is unlikely except over large spatial scales. Naive juveniles of Arctonoe spp. can now be obtained from laboratory cultures to test the hypothesis that genetically based host preferences are important in determining host-use patterns in these symbionts.

Both larval and adult fan worms capture particles with opposed bands of cilia. While the larvae use one of the opposed bands (the prototroch) for both feeding and swimming, the sessile adults rely partly on ambient currents to bring food particles to the ciliary bands. The scaling of length of prototrochal cilia with larval body size contrasts with scaling of the opposed latero-frontal cilia with adult body size. In the larva of the serpulid Hydroides elegans, the length of prototrochal cilia increased from 28 to 42 µm in early to late-stage larvae. In contrast, latero-frontal cilia did not increase in length (23 µm) during postlarval development of H. elegans. Among adults of 5 fan-worm species, lengths of latero-frontal cilia ranged from 22 to 35 µm and were weakly correlated with body size. The total area of ciliary filter nevertheless increased with increasing body dry weight of worms with an allometric exponent similar to exponents reported for gill and lophophore areas vs. body weight within species of suspension-feeding bivalves, brachiopods, and gastropods. The similar scaling was remarkable given the striking differences in distribution and function of the ciliary filters. In adult fan worms, increases in filter area depended largely on increases in number and length of radioles; differences in branching of radioles had little effect. Radioles were commonly in 2 or more rows in series, implying refiltration in still water by downstream radioles. Since the allometry of worms' filter area with body size depends on filters in series, it depends on ambient currents that overwhelm ciliary currents.

We tested the hypothesis that hooked setae function as anchors in three species of tubiculous polychaetes (Eudistylia vancouveri, Schizobranchia insignis, and Oweniafusiformis). All maintained position within their tubes when exposed to high pressures (up to 100-200 kPa) applied from the posterior direction (where it would tend to cause the tips of hooks to embed in the tube wall). When pressure was applied in the opposite direction, where hooks would not tend to embed in the tube wall, the worms were expelled from their tubes at lower pressures (30-100 kPa). The ability of these worms to maintain their position within their tubes was independent of body size. On the basis of these findings we made three predictions. First, worms that use their hooked setae as anchors should have those hooks located on the body in greatest number and size on the segments associated with greatest worm diameter. Second, as worms increase in size, setal armory should increase in a predictable way. The force that can be applied to extract worms from their tubes by suction feeding fish or wave action would increase as the area subject to suction increases (proportional to the cross sectional area of the tube). Therefore, we predict that setal armory should also increase as a squared function. Third, hooks or uncini should show patterns of wear or loss and/or the worms' bodies should show scars or wounds where the setae are most used (e.g., where worm diameter is at its maximum). All of these predictions were supported by the data and indicate that hooked setae function as anchors for tubiculous polychaetes. This is important for understanding the biology of these animals and has implications for using hooked setae as characters in phylogenetic analyses.

The enchytraeid Grania amrricana has a dorsal statocyst within the peristomium. It is connected to the anterior end of the cercbral ganglion. Transmission electron and light microscopy were used to study this region of the head. The statocyst is divided into four membrane-bound chambers; each contains an electron dense statolith surrounded by numerous sensory cilia, so that it is a multi-chambered or compound statocyst. Cilia within the statocyst possess a 9 × 2 + 0 microtubule arrangement, with one of the doublets in a central position. All cilia that were observed in the statocyst and in the cerebral ganglion had this arrangement of microtubules. This is the first description of a statocyst in the Clitellata. The statocyst of G. americana is compared to those described in polychaetes and may provide useful information for phylogenetic and taxonomic studies of the genus, of clitellates, and of annelids.

Although the oesophageal appendages in the four enchytraeids Erichytrueus crypticus, Fridericiu strinta, Buchholziu apperzdiculata, and Achaetu sp. are quite different from one another in shape and position, their histology and ultrastructure are basically the same. These are intestinal appendages, the lumina of which distally end blind and proximally open into the oesophagus. Almost all of the few cells in their single-layered epithelium have a microvillous, cilia-free border at the apex, facing towards the lumen, and basally comprise an extremely extensive labyrinth. The presence of the latter, composed of very thin cell processes, and of numerous mitochondria identifies the organs as energy-producing and -consuming, transport-active stnictures. Their possible function as a food-moistening organ or osmoregulatory organ is discussed, and they are compared with other intestinal appendages in enchytraeids and other oligochaetes.

Tertiapatus dominicanus n.g., n.sp. (Tertiapatidae n.fam.) and Succinipatopsis balticus n.gen., n.sp. (Succinipatopsidae n.fam.) (Lobopodia: Onychophora), the first Tertiary fossils of the Lobopodia, are described from Dominican and Baltic amber, respectively. Both families are characterized by the presence of simple legs lacking foot portions with claws and pads. Tertiapatidae is further characterized by soluble body pigments and oral papillae shorter than the legs. Succinipatopsidae is characterized by non-soluble body pigments and oral papillae longer than the legs. Nomenclatural changes include the erection of the class Udeonychophora n.nom. for terrestrial onychophorans with a ventral mouth, the order Ontonychophora n.nom. for extant onychophorans possessing legs with a differentiated “foot” portion, and the family Helenodoridae n.nom. for the genus Helenodora from the Carboniferous. The biogeographical significance of these fossils and their phylogenetic relationship with previously described onychophorans are discussed.

Members of Tigriopus californicus, an harpacticoid copepod, live in small, shallow tidepools in the upper spray zone where they cannot avoid the full effect of visible and ultraviolet (UV) radiation. Field experiments using ambient light show that individuals of T. californicus aggregate in areas of lower radiation at midday, yet have no preference at dawn and dusk. In lab experiments, individuals of T. californicus show no preference between areas exposed only to photosynthetically active radiation (PAR) or shade, but aggregate in the shaded portion of a tank when exposed to UV-B. Light detection in T. californicus is presumably by the nauplius eye, which is described at the histological and ultrastructural levels. Microvilli of the photosensitive rhabdomere are regularly packed at noon, dusk, and midnight. Processes suggesting rhabdomere synthesis, including vesicles and tubules binding to the base of microvilli, are observed at these times. At dawn, the rhabdomere shows areas of degeneration and coated pits and multivesicular bodies are common at the base of the microvilli. Comparison with previous studies show a wide variety of nauplius eye complexity in copepods.