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Notes: Abstract We investigated recruitment of the herbivorous gastropodLacuna vincta (Montagu, 1803) in the canopies ofMacrocystis integrifolia andNereocystis luetkeana beds in Barkley Sound, Vancouver Island (British Colombia), from 1987 to 1989. Four factors influencing intensity and patterns of recruitment were studied: (1) seasonality of oviposition, (2) larval abundance, (3) growth of larvae in the field and (4) larval settlement. Egg masses were abundant on low intertidal algae but were scarce in kelp canopies. Although egg masses could be found almost year-round, a distinct and intense period of oviposition occurred during winter and spring. Intracapsular development lasted 2.5 to 3.5 wk before planktotrophic veligers emerged. The duration of the planktonic period, 7 to 9 wk, was determined through an in situ study of cohorts ofLacuna spp. larvae present in the plankton between January and June 1988. The general timing of the onset of the spring peak recruitment period was predicted from these cohorts. Primary periods of recruitment ofL. vincta in the canopy occurred in April–May (average density up to 383.9 juveniles m−2 blades), with a second period of lower intensity in the late summer—fall period. We observed similar trends between abundance of advanced larvae (〉 500µm) in the plankton and recruitment rates in kelp canopies. Although adults were occasionally observed in the canopy, newly metamorphosed juveniles consistently dominated the habitat. The persistance of small juveniles (0.7 to 1.5 mm), rapid declines in density shortly after recruitment, and SCUBA observations of drifting individuals suggest that juveniles migrate to the under-canopy or low intertidal area after a brief period of growth on kelp blades.

Notes: Abstract Mortality factors most likely to constitute substantial selective pressures for early juvenile gastropods on temperate rocky shores were identified by examining the vulnerability of hatchlings of an intertidal snail, Nucella emarginata, to heat stress, desiccation, and predation in 1992 and 1993. The highest temperature of substrata measured at tidal heights colonized by N. emarginata in Barkley Sound, British Columbia, Canada, was 28.5°C. This temperature was not lethal to hatchlings in laboratory tests. In laboratory and field desiccation experiments, all hatchlings died within 6 h of emersion. Early juveniles could not survive direct exposure to even moderate drying conditions for the duration of a low tide. Hence, intertidal microhabitats which dry up even for short periods during low tides would prove lethal. Of 45 intertidal animal species to which hatchlings were exposed in the laboratory, small decapod crustaceans were the only organisms to cause substantial hatchling mortality. Of these, Pagurus hirsutiusculus and Hemigrapsus nudus were by far the most abundant in the field, and are probably the only important predators of early juvenile N. emarginata at most sites. Total predator densities in the field were as high as 438 individuals m−2, suggesting that predation pressure may be intense. Desiccation and predation by decapod crustanceans appear to be the most significant threats to early juvenile N. emarginata. These factors commonly occur on most temperate rocky shores and undoubtedly constitute major selective agent influencing population parameters and shaping life-history strategies and early juvenile traits of intertidal invertebrates.

Notes: Abstract Rostanga pulchra MacFarland, a small (1 to 2 cm) dorid nudibranch, lays an average of 7000 eggs in the laboratory during a period of 30 days in the summer. The veligers hatch 15 to 16 days after oviposition and it takes another 35 to 40 days to become competent for metamorphosis at a temperature of 10° to 15°C. Larval cultures were maintained initially at a concentration of 500 veligers per 100 ml of filtered sea water (antibiotics added). During the planktotrophic phase of development, the veliger grows from 150 to 300 μm in shell length. Although the veligers are generalists in their food preference, the best result (faster growth) was achieved by feeding them with a combination of Monochrysis lutheri and Isochrysis galbana. The concentration of food cells was kept at 104 cells per ml of culture media and was supplied every 2 to 3 days. A veliger which is competent to metamorphose is identifiable morphologically by its propodium, eyespots, rhinophores, and spiculated dorsal papillae. The entire metamorphic process lasts 24 h when a suitable substrate such as the food sponge Ophlitaspongia pennata is provided. The competent veliger is able to delay metamorphosis for at least 3 weeks. Juveniles were kept in the laboratory for 70 days and, during this period, grew to a length of 4.5 mm.

Notes: Abstract Substratum selection experiments were carried out in situ with larvae of the holothurian Psolus chitonoides Clark in the rocky subtidal of the San Juan Islands, Washington. The experiments indicated, in agreement with laboratory findings, that pentactula larvae settle gregariously, either on the adult, or (when the bivium is obscured by epizooites) by clustering around the margin of the adult sole. Late larvae and early juveniles are strongly photonegative. Following metamorphosis, juveniles migrate from the adults into nearby shaded habitats, where they may take up residence indefinitely. Although adults retain the capacity to move, they relocate only when their living conditions become unsuitable; in most circumstances they are effectively sessile. Small-scale spatial pattern of the adults, which was documented quantitatively on subtidal rock walls, boulders and cobbles, correlates well with microtopographical features. The aggregation observed in the field is primarily due to post-settling migration rather than larval substratum choice at settlement.

Notes: Abstract Known reproductive patterns in the polychaete family Sabellidae include: (1) broadcasting of gametes, (2) depositing of benthic egg masses, (3) brooding outside the lip of the tube, and (4) brooding within the tube. There is little information for sabellids in the third category; there-fore we have studied the reproductive biology of Sabella (=Demonax) media (Bush), one of the few species known to brood its early developmental stages outside the tube. A total of 32 adults of S. media with egg cocoons were collected from the surfaces of compound ascidians (Aplidium sp. and Didemnum sp.) and from holdfasts of a brown alga (Hedophyllum sessile) at Eagle Cove, San Juan Island, Washington, USA, from June 1981 through June 1982, between tidal levels of 0.0 and 0.6 m. The donutshaped cocoons, each containing over 1 000 eggs, are deposited just outside the tube aperture from April through September. Larval development takes place within the cocoon through the 3-setiger stage, at which time the larvae emerge (about 8 d after egg deposition). The newly hatched larvae are demersal and swim near the bottom of the culture dish for 1 d before settlement. Metamorphosis takes nearly a week, and initial formation of the tube is also gradual. The reproductive patterns within the family Sabellidae are discussed, and the adaptive significance of extratubular brooding considered.

Notes: Abstract Reproduction and development of two psolid sea cucumbers in waters of the San Juan Archipelago, Washington, were studied from April 1981 through August 1984. Spawning inPsolus chitonoides Clark andPsolidium bullatum Ohshima in the laboratory and in the field waters of the San Juan Archipelago, Washington, occurred from February through may, with heaviest spawning in April and May. The egg ofPsolus chitonoides was bright red in color and 627µm in diameter;Psolidium bullatum released eggs that were golden yellow in color and 330µm in diameter. Maximum measured fecundities (spawned eggs) forPsolus chitonoides andPsolidium bullatum were 34 700 and 3 074, respectively. Developmental schedules were similar in both species. Early cleavages were equal, radial, and holoblastic; slightly subequal cleavage was common inPsolus chitonoides. The gastrula elongated to form a uniformly ciliated larva and the vestibule first appeared as a ventral crescent-shaped depression, after which the larva decreased in length and formed three posterior ridges that encircled the early doliolaria. Just prior to settlement, there was loss of cilia between the three ridges and on the posterior end of the early doliolaria, leaving three ciliary rings that are characteristic of the dendrochirote doliolaria larva. Vertical swimming ensued, and five primary tentacles protruded through the vestibule, with occasional attachment to the substratum using the primary tentacles. Upon settlement, two primary podia emerged and all external ciliation was lost except among tentacular papillae and on the end of tube feet. Timing of appearance and of loss of ciliary rings suggest that the rings function in vertical swimming and substratum selection behaviors. Metamorphosis involved the following simultaneous events: (1) resorption of the preoral lobe, (2) formation of large, dorsal, calcareous ossicles, (3) flattening of the trivium, and (4) proliferation of ventral tube feet on Ambulacral Radii B and E to form the sole. Reproduction in the family Psolidae is reviewed. The large proportion of brooders in this family appears to be related to small size, the possession of protective armor and sole, and geographic distribution (mainly in Antarctica). Lecithotrophic doliolaria larvae with three ciliary rings are produced by large northern psolids.

Notes: Abstract The effect of bryozoan colonization on inorganic nitrogen acquisition by Agarum fimbriatum Harv. and Macrocystis integrifolia Bory., collected from the west coast of Vancouver Island, British Columbia, Canada, was examined in laboratory experiments during June and July 1992. Pieces of kelp blades that were completely covered on one side by the bryozoans Lichenopora novae-zelandiae Busk or Membranipora membranacea, L., or uncolonized (clean treatment), were used to estimate the rate at which nitrate and ammonium were removed from the surrounding seawater. In addition, the rate of ammonium excretion by bryozoans isolated from their associated kelp was measured and also estimated from the results of the uptake experiments. Values obtained were used to estimate the contribution of ammonium excreted by bryozoans to the total amount of inorganic nitrogen available to the associated kelp. Both bryozoan species reduced the ability of the associated kelp to remove nitrate and ammonium from seawater but provided a source of ammonium to the kelp through excretion. The nitrogen status of colonized and clean kelp disks was determined from the ratio of total particulate carbon to total particulate nitrogen (C:N ratio). The C:N ratios for A. fimbriatum colonized with either L. novae-zelandiae or M. membranacea were similar (C:N=12 to 14), and differences between colonized and clean treatments were not significant. For A. fimbriatum, therefore, the C:N ratio indicates that this species was not nitrogen limited at the time of the present study. In contrast, both colonized and clean disks of M. integrifolia were nitrogen limited, but colonized disks (C:N=19) were significantly less limited by nitrogen than clean disks (C:N=29). Results are discussed in relation to the different environments inhabited by both kelp species and are consistent with the hypothesis that ammonium excreted by bryozoans was an important source of inorganic nitrogen to M. integrifolia, but not to A. fimbriatum, at the time of the study.

Notes: Abstract Reproduction in the viviparous apodid sea cucumber Leptosynapta clarki was examined in Grappler Inlet, Bamfield, Vancouver Island, Canada from July 1989 through July 1991. The reproductive cycle of L. clarki is annual with gonad growth during the summer months. Male sea cucumbers spawn during November and December and internally fertilize, through as yet undetermined means, the oocytes within the ovary. Embryonic development is rapid, so that within 2 wk fertilized eggs reach the pentactula stage. Pentactulae have an open mouth and anus and actively move in the ovarian tubules feeding on droplets and fluid derived from the resorption of unfertilized eggs. Histological examination of gametogenesis shows similar development to that found in non-brooding holothurians. However, the protandric sex change observed in some male L. clarki after spawning and changes to the overian wall structure prior to fertilization are previously undescribed in sea cucumbers.

Notes: Abstract The spermatozoa of four species of the patellogastropod family Lottiidae (Lottia pelta, L. digitalis, L. strigatella, Tectura scutum) and one species of the archaeogastropod family Fissurellidae (Diodora aspera) were examined in 1990 using transmission electron microscopy. All have primitive or ect-aquasperm, typical of invertebrates using external fertilization. Sperm of the lottiid limpets are characterized by a 5 to 9 μm-long head composed of a conical acrosome which constitutes 〉50% of the head length, and a cylindrical nucleus. The acrosome of all species of lottiids is differentiated internally, and has a posterior invagination ≈0.9 to 1 μm in depth, into which an elongate acrosomal lobe protrudes. Between the posterior acrosomal lobe and the nucleus, the subacrosomal material is aggregated as a fibrous column. The midpiece of the sperm has a ring of 4 to 5 spherical mitochondria of ≈0.6 μm diam, posterior to which is a collar of cytoplasm ≈1 μm long, which sheaths the anterior portion of the axoneme. The size and morphology of the acrosome and large cytoplasmic collar clearly distinguish the spermatozoa of the Lottiidae from other families of Patellogastropoda. The sperm of D. aspera (Fissurellidae) is typical of the family of archaeogastropod; the head has a length to breadth ratio of 4:1, and the cylindrical nucleus is capped by a small acrosome, 〈25% of the total head length, which is deeply invaginated.

Notes: Abstract Opsonins, a group of serum proteins present in vertebrates, are known to bind to the surface of many kinds of pathogens and tag them as targets for phagocytosis. Opsonin-like molecules have been suggested to exist in several invertebrates. In this paper, we report the discovery of a new opsonin-like molecule in the coelomic fluid of the sea cucumber Holothuria leucospilota. Opsonic activity in cell-free coelomic fluid was characterized by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, two-dimensional electrophoresis and gel filtration. Phagocytic uptake of yeast cells and latex beads by amoebocytes was quantified by microscopic analysis. It was found that a 20 kdalton protein bound to and enhanced phagocytosis of heat-killed yeast cells. The results of Western blot analysis suggest that both amoebocytes and spherule cells produce this opsonin-like molecule.