Cyphonautes Larvae Research Articles

Planktonic Duration of the Bryozoan Cyphonautes Larva and Limits on Growth Rate Imposed by Its Form-Limited Maximum Clearance Rate.

AbstractThe form of the cyphonautes larva of bryozoans changes little during development. The ciliated band that generates the feeding current increases nearly in proportion to body length, so that the maximum rate of clearing planktonic food from a volume of water becomes increasingly low relative to body protein. This development is unlike the other larvae that produce a feeding current with bands of simple cilia. The cyphonautes' growth rate has therefore been predicted to be unusually low when food is scarce. As predicted, cyphonautes larvae of a species of Membranipora starved at concentrations of food that supported growth of pluteus larvae. Comparisons between the cyphonautes and plutei of a sand dollar were for growth from first feeding to metamorphosis, with a mix of two algal species. Another comparison was for growth of cyphonautes at an advanced stage and plutei of a regular sea urchin at an early stage, with food in seawater at a reduced concentration. The low maximum clearance rate did not prevent rapid growth and development of some cyphonautes from egg through metamorphosis when food was abundant. Twenty-nine days for development to metamorphosis in the laboratory with abundant food was close to Yoshioka's estimate of larval duration from the time lag between adult zooid density and larval abundance in a population in the Southern California Bight. Despite individual variation in growth rates and other physiological and environmental influences, simple measures of larval form predicted the differences in larval performance: scarce food extended larval duration for the cyphonautes more than for plutei.

Diversity of zooplankton in Kadalundi-Vallikunnu Community Reserve, North Kerala, India

Zooplankton samples collected from ten stations covering the entire stretch of the Kadalundi-Vallikunnu CommunityReserve, Kerala, south India, for a period from July 2018 to June 2019 were studied. Twenty eight groups of zooplankton viz. copepods, foraminifera, medusae, chaetognaths, siphonophores, ctenophores, ostracods, cladocera, Lucifer sp., amphipods, isopods, appendicularia, Balanus nauplii, cyphonautes larvae, polychaete larvae, echinoderm larvae, ephyra larvae, brachiopod larvae, alima larvae of squilla, aquatic insect larvae, prawn larvae, crab zoea, crab megalopa larvae, bivalve larvae, pteropods, gastropod larvae, fish eggs and fish larvae were recorded. Among these, copepods formed the major portion of 43%. An average of 18330 nos. per 100 m3 was noticed from the study area. The maximum and minimum density of zooplankton was observed at Station 1 and 10 respectively and a decreasing trend in abundance was recorded from barmouth towards upstream stations. Seasonal studies indicated a maximum of 52% during pre-monsoon, followed by 36% during post-monsoon and a minimum of 12% during monsoon. Different indices of diversity, dominance plot, dendrogram and Multi Dimensional Scaling (MDS) plot are presented and discussed. Keywords: Biodiversity, Estuary, PRIMER, Primary consumers, Seasonality

Studying Cyphonautes Larvae of Hislopia prolixa(Bryozoa; Ctenostomata) in Temperate Fresh Water

Studying Cyphonautes Larvae of Hislopia prolixa(Bryozoa; Ctenostomata) in Temperate Fresh Water

Spatiotemporal patterns and impact of a cyclone on the zooplankton community structure in a brackish coastal lagoon

Zooplankton communities in response to hydrological (salinity, turbidity, water temperature, nitrate, phosphate, silicate) and biological (phytoplankton density) variables were studied in the Asia’s largest brackish water lagoon, Chilika (India). Water samples were collected from 13 stations on a monthly frequency between July 2014–June 2015. A total of 141 species of holoplankton including Ciliophora, Foraminifera, Rotifera, Rhizopoda, Gastropoda, Cladocera, Copepoda, Ostracoda, Malacostraca, Chaetognatha, Chordata, Nematoda, and 18 types of planktonic larvae were identified. Copepods were the most dominant and diverse zooplankton in terms of their species richness, numerical abundance, and widespread distribution in the lagoon. The major holoplanktonic taxa were Acartia sp., Acrocalanus gibber, Acrocalanus gracilis, Acrocalanus longicornis, Euterpina acutifrons, Lecane sp., Oithona sp., Pseudodiaptomus serricaudatus, and Tintinnopsis tubulosa. The dominant planktonic larvae were bivalve veliger, copepod nauplii, cyphonautes larvae, gastropod veliger, and protozoea of lucifer. Canonical correspondence analysis showed that distribution of zooplankton assemblages was influenced by salinity, turbidity, and phytoplankton density. Indicator analysis demarcated 26 indicator zooplankton taxa. Of these, the most prominent indicator zooplankton such as Belzebub hanseni, Mesopodopsis orientalis, Chydorus sphaericus, and Corycaeus catus were characteristic to salinity gradient in southern sector, sediment resuspension in central sector, eutrophic conditions in northern sector, and tide-induced intrusion of marine forms in outer channel, respectively. Hudhud, a category 4 cyclone resulted decline in the abundances of zooplankton population. Copepod nauplii and copepodites were dominant during post-Hudhud and their succession was linked to the increased phytoplankton density due to an upsurge in the nutrient level in the northern sector of the lagoon. The present study provided a comprehensive detail on the zooplankton composition and their environmental drivers including the impact of a tropical cyclone from a tropical coastal lagoon system.

Electra vs Callopora: life histories of two bryozoans with contrasting reproductive strategies in the White Sea

ABSTRACT The life histories of two common boreal-Arctic bryozoans – Electra pilosa and Callopora craticula – living on kelps in the White Sea are described for the first time using colony mapping. Colony functional dynamics (sexual, feeding, budding and rejuvenation) was traced seasonally via recording zooidal states. During the ice-free season the population of the zygote spawner E. pilosa was represented by three generations – overwintered (maternal) and two young ones (daughter and granddaughter). The overwintered colonies exhibited two-phased reproduction and the ‘early’ daughter colonies reproduced just once. ‘Late’ colonies, together with the granddaughter generation, remained sterile. Four generations are described for the brooder C. craticula, three of which continuously produced larvae. While the two species co-exist on the same substratum, reproduction in E. pilosa started almost 1 month later (in late June), which could be explained by the insufficient abundance of phytoplankton in early summer to support the start of oogenesis and feeding cyphonautes larvae. The estimated maximal colony lifespan is 13 months in E. pilosa and 15 months in C. craticula. The broad comparison of bryozoan reproductive ecology in the White Sea showed that their life histories are much more diverse, complex and evolutionarily flexible than previously acknowledged.

New genus for a unique species of Indo-West Pacific bryozoan

Larval type, larval morphology, ancestrular morphology and colony astogeny have great systematic value in the cheilostomate bryozoans, but for most species these characters are undocumented. Whilst most cheilostomate bryozoan species produce lecithotrophic coronate larvae; a minority of species produce planktotrophic cyphonautes larvae, all belonging to genera within the superfamily Membraniporoidea. Biflustra laboriosa Tilbrook, 2006 nominally belongs to a membraniporid genus whose species are otherwise characterised by having a twinned ancestrula. The production of a single ancestrula from a cyphonautes larva and overall zooidal morphology excludes B. laboriosa from the Membraniporidae and its zooidal characters are alien to any other membraniporoidean genus. Accordingly, Tarsocryptus n. gen. is erected to accommodate it, resulting in the new combination Tarsocryptus laboriosa n. comb. Its reassignment here to the membraniporoidean Electridae is tentative.

Physical forcing of distributions of bryozoan cyphonautes larvae in a coastal embayment

In shallow rocky subtidal ecosystems in the western North Atlantic, outbreaks of the nonindigenous encrusting epiphytic bryozoan Membranipora membranacea cause defoliation of laminarian algae, facilitating a phase transition from native kelp beds to meadows of invasive algae. We quantified spatial (m [depth] to km [sites]) and temporal (hourly to monthly) patterns in the abundance of larvae of M. membranacea, and a morphologically similar native species, Electra pilosa, in relation to physical structure (temperature, salinity, density) of the water column in St. Margarets Bay, Nova Scotia, Canada, on 8 dates from September to November 2007. During the study period, the water column ranged from strongly stratified to well mixed, and cross-shore movements of water masses (wind-driven upwelling and downwelling) were indicated by shoaling of the isoclines. When a strong pycnocline was located between the 2 sampled depths (4 and 12 m), larvae of both species were more abundant in the shallower, warmer, fresher layer. The linear relationship between strength of stratification and the relative abundance of larvae between depths was significant over 2 temporal (hourly, weekly) and 1 spatial (km) scale examined for M. membranacea, but not for E. pilosa. Highest abundance of larvae of both species in the warm fresh surface layer suggests onshore transport during wind-driven downwelling events. Dissimilar patterns in size-frequency distributions between the indigenous and nonindigenous bryozoan larvae suggest that species-specific characteristics of larvae of M. membranacea may be a contributing factor to its success as an invader in the western North Atlantic.

Structure and occurrence of cyphonautes larvae (bryozoa, ectoprocta)

We have studied larvae of the freshwater ctenostome Hislopia malayensis with scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and LM of serial sections. Some additional observations on larvae of M. membranacea using SEM and CLSM are also reported. The overall configuration of muscles, nerves, and cilia of the two larvae are identical. However, the larva of H. malayensis is much smaller than that of M. membranacea, which may explain most of the differences observed. Although all major nerves and muscle strands are present in H. malayensis, they are generally composed of fewer fibers. The H. malayensis larva lacks the anterior and posterior intervalve cilia. Its pyriform organ is unciliated with only a small central depression. The adhesive epithelium is not invaginated as an adhesive sac and lacks the large muscles interpreted as adhesive sac muscles in the M. membranacea larva. The velum carries two rows of ciliated cells, though the lower "row" consists of only one or two cells. Both rows of ciliated cells are innervated by nerves, which have not been detected in the M. membranacea larva. The ciliated ridge of H. malayensis lacks the frontal cilia. The planktotrophic cyphonautes larvae in a number of ctenostome clades and in the "basal" cheilostome clade Malacostega (and probably in the earliest cheilostomes) support the idea that the cyphonautes larva is the ancestral larval type of the Eurystomata. It may even represent the ancestral larval type of the bryozoans (= ectoprocts).

Settlement behavior of cyphonautes larvae of the bryozoan Membranipora membranacea in response to two algal substrata

Abstract. Settlement is an important process in the biphasic life histories of many marine invertebrates. Little is known regarding the fine‐scale behavioral mechanisms for finding and attaching to a suitable substratum, particularly under conditions that may impose a potential challenge, such as flow. In this study, we examined the settlement behavior of cyphonautes larvae of the bryozoan, Membranipora membranacea, in response to two different algal substrata. Larvae showed a strong preference for settling on the kelp Nereocystis luetkeana over the red alga Mazzaella splendens. We then tested whether the behavioral mechanisms used by larvae to attach to these algae differed when presented with the challenge of flowing water during settlement. We found that larvae exhibited different behaviors on the two species of algae in flowing water. Larvae were more often observed in direct contact with the preferred alga (N. luetkeana) exhibiting fine‐scale active search behaviors. On the less preferred alga (M. splendens), larvae were less frequently observed in direct contact with the alga, and appeared to be exhibiting broad‐scale passive search behaviors along the surface of the blade. Our results suggest that cyphonautes larvae alter their behavior in response to their preferred settlement habitat.

Ultrastructure of mesoderm formation and development in Membranipora membranacea (Bryozoa: Gymnolaemata)

Mesoderm origin in Bryozoa is largely unknown. In this study, embryonic and early larval stages of Membranipora membranacea, a bryozoan exhibiting a planktotrophic cyphonautes larva, are investigated using mainly ultrastructural techniques. Shortly after the onset of gastrulation, an ectodermal cell, which is situated centrally at the prospective anterior pole of the larva, can be recognized by its constricted apical surface and enlarged basal part. It is also distinct from other ectodermal cells by the composition of its cytoplasm. In later stages, it has left the epidermis, lost its epithelial character, and is situated subepithelially, between the basal sides of the ectodermal and endodermal sheets. A blastocoelic cavity is not present at this stage. This cell divides and gives rise to a group of cells forming a muscular and neuronal strand at the anterior side of the larva. The majority of the larval musculature originates from this ingression. Despite this evidence for an ectodermal origin, additional sources of mesoderm can so far not be excluded. The literature on mesoderm origin in Bryozoa is reviewed and the results are compared to known data from other metazoan taxa.

Loss and gain of the juvenile rudiment and metamorphic competence during starvation and feeding of bryozoan larvae

In many animals, larval structures and juvenile rudiments develop independently. One advantage of this independence is that juvenile rudiments can be expended as a nutrient reserve or for energy conservation. When bryozoan cyphonautes larvae were starved, structures required for settlement and metamorphosis shrank. When the larvae were again fed, these structures grew back. Starvation reduced the size of both the internal sac, a rudiment of postlarval juvenile structures, and the pyriform organ, which functions in sensing and crawling on the substratum at settlement. In contrast, starvation affected neither the size of the larval shell nor the lengths of the ciliary bands used in swimming and feeding. Starved larvae that had reduced the pyriform organ and internal sac did not metamorphose in response to stimuli from a laminarian alga. The laminarian alga did stimulate metamorphosis of the same larvae after renewed feeding, when the larvae had regrown these structures. Thus starved larvae expended body parts needed for settlement and metamorphosis when food was scarce while retaining structures for feeding, swimming, and defense. Starved larvae thereby retained the capacity to regrow structures needed for settlement and metamorphosis when they again encountered food. Advantages from expendable juvenile rudiments may enhance selection for their being developmentally distinct from structures for larval swimming and feeding.

Influence of contrasting larval developmental types upon the population-genetic structure of cheilostome bryozoans

For many sedentary or sessile benthic marine invertebrates the planktonic duration of the larval stage is believed to be a key determinant of the magnitude of genetic differences between populations. An obvious dichotomy in dispersal potential exists within cheilostome bryozoans that develop from either (1) a cyphonautes larva that spends several weeks in the plankton or (2) a brooded coronate larva that settles soon after release from the adult colony. This study characterises the pattern of variation at allozyme loci among British populations of four species of bryozoan—two species with cyphonautes and two with coronate larvae. There is some variation in the estimates of genetic differentiation among similarly separated populations that may be a consequence of non-equilibrium genetic conditions arising from sporadic migration, possibly through dispersal by rafting on macroalgae by mature colonies. Despite this, however, both the level of genetic differentiation between populations and the pattern of migrant exchange correlate with the larval developmental mode. Bryozoan species that brood coronate larvae show higher levels of genetic heterogeneity between populations and significant isolation by distance genetic structure while, by contrast, distance has little or no effect upon the amount of genetic differentiation among populations of bryozoans with cyphonautes larvae. For cheilostome bryozoans, therefore, it appears that genetic differentiation between populations is directly associated with the type of larval development. These data are discussed also with respect to levels of gene diversity and the geological pattern of cheilostome bryozoan species diversity.

Versatile ciliary behaviour in capture of particles by the bryozoan cyphonautes larva

AbstractCyphonautes larvae of a bryozoan, Membranipora membranacea, used several ciliary mechanisms to capture algal cells upstream from the lateral band of cilia that produces a feeding current. (1) Lateral cilia changed beat and a backcurrent occurred at the time and place that particles were retained. (2) Algal cells were sieved and held stationary at the upstream (frontal) side of a row of laterofrontal cilia that were not beating. (3) Localized extension of cilia toward the inhalant chamber, coincident with particle captures, indicated that laterofrontal cilia flick toward the inhalant chamber. These flicks may aid transport of captured particles toward the mouth. Thus my earlier report that larvae only sieve, in contrast to the adults (which have an active ciliary response) was in error. The similar ciliary bands in adult and larval bryozoans and in other lophophorates (brachiopods, and phoronids) suggest that these animals share a core repertoire of ciliary behaviours in the capture and concentration of suspended food particles.

A new cheilostome bryozoan with gigantic zooids from the North-West Pacific.

Gontarella gigantea gen. et sp. nov. is described from two stations, one in the Sea of Okhotsk and the second on the Pacific side of the Small Kuril Arc. This membraniporiform anascan cheilostome bryozoan has very large zooids, the largest known among extant sheet-like encrusting anascans. Comparative data on similar sheet-like cheilostomes gathered from the literature shows that the new species represents a conspicuous outlier in size, with the surface area of the zooid being approximately twice that of the next largest species. Skeletal evidence, including the lack of ovicells, indicates that G. gigantea belongs within the malacostegan family Electridae. The gigantic ancestrula suggests that the species has a cyphonautes larva about 1 mm in maximum dimension.

Ciliary filter‐feeding structures in adult and larval gymnolaemate bryozoans

Abstract. Ciliary filter‐feeding structures of gymnolaemate bryozoans—adults of Flustrellidra hispida and Alcyonidium gelatinosum, larvae of Membranipora sp.—were studied with SEM. In F. hispida and A. gelatinosum, the distal part of each tentacle has a straight row of stiff laterofrontal cilia which carry out “ciliary sieving” to capture suspended food particles that are subsequently transported downward towards the mouth by tentacle flicking; both structure and function resemble those of stenolaemate tentacles. The proximal part of the tentacle and of the ciliary ridge of a cyphonautes larva have strikingly similar structures, except that the laterofrontal cells are monociliate in the adults and biciliate in the larvae. The laterofrontal cells of the tentacles are arranged in a zigzag row and their cilia form two parallel rows, a frontal and a lateral row. The latter probably forms the sieve of stiff filter cilia in front of the water‐pumping lateral cilia, whereas the frontal row appears to be held close to the frontal ciliary band of the tentacle. The biciliate laterofrontal cells of the cyphonautes larva have the cilia arranged in similar rows. The detailed morphological similarities between the ciliary bands of adult and larval filtering structures suggest that the feeding mechanisms are similar, contrary to what has been previously thought.

The Phylogenetic Position of Entoprocta, Ectoprocta, Phoronida, and Brachiopoda

Ectoprocts, phoronids and brachiopods are often dealt with under the heading Tentaculata or Lophophorata, sometimes with entoprocts discussed in the same chapter, for example in Ruppert and Barnes (1994). The Lophophorata is purported to be held together by the presence of a "lophophore," a mesosomal tentacle crown with an upstream-collecting ciliary band. However, the mesosomal tentacle crown of pterobranchs has upstream-collecting ciliary bands with monociliate cells, similar to those of phoronids and brachiopods, although its ontogeny is not well documented. On the contrary, the ectoproct tentacle crown carries a ciliary sieving system with multiciliate cells and the body does not show archimery, neither during ontogeny nor during budding, so the tentacles cannot be characterized as mesosomal. The entoprocts have tentacles without coelomic canals and with a downstream-collecting ciliary system like that of trochophore larvae and adult rotifers and serpulid and sabellid annelids. Planktotrophic phoronid and brachiopod larvae develop tentacles at an early stage, but their ciliary system resembles those of echinoderm and enteropneust larvae. Ectoproct larvae are generally non-feeding, but the planktotrophic cyphonautes larvae of certain gymnolaemates have a ciliary band resembling that of the adult tentacles. The entoprocts have typical trochophore larvae and many feed with downstream-collecting ciliary bands. Phoronids and brachiopods are thus morphologically on the deuterostome line, probably as the sister group of the "Neorenalia" or Deuterostomia sensu stricto. The entoprocts are clearly spiralians, although their more precise position has not been determined. The position of the ectoprocts is uncertain, but nothing in their morphology indicates deuterostome affinities. "Lophophorata" is thus a polyphyletic assemblage and the word should disappear from the zoological vocabulary, just as "Vermes" disappeared many years ago.

The identity of two species of cyphonautes larvae (Bryozoa: Cheilostomata) from Lizard Island, Great Barrier Reef, Australia

Two species of bryozoan cyphonautes larvae are described and illustrated from plankton tows made among coral heads in shallow waters at Lizard Island, Great Barrier Reef, Australia. Individuals of both species settled and metamorphosed, and their ancestrulae and early astogeny are also described and illustrated. One is recognized as a formerly unknown species of Conopeum, C. ponticum sp. nov., the other is attributed to Biflustra reticulata.

Tentacle structure and filter-feeding in Crisia eburnea and other cyclostomatous bryozoans, with a review of upstream-collecting mechanisms

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 168:163-186 (1998) - doi:10.3354/meps168163 Tentacle structure and filter-feeding in Crisia eburnea and other cyclostomatous bryozoans, with a review of upstream-collecting mechanisms Claus Nielsen1,*, Hans Ulrik Riisgård2 1Zoological Museum (University of Copenhagen), Universitetsparken 15, DK-2100 Copenhagen, Denmark 2Research Centre for Aquatic Biology (Institute of Biology, Odense University), Hindsholmvej 11, DK-5300 Kerteminde, Denmark *E-mail: cnielsen@zmuc.ku.dk ABSTRACT: The upstream-collecting filter-feeding mechanisms occurring in many aquatic organisms are not adequately described. Tentacles of Crisia eburnea and other cyclostome bryozoans, with only lateral and laterofrontal ciliary bands, are among the least complicated upstream-collecting systems among metazoans. SEM and TEM revealed that the tentacles have 2 rows of very closely set lateral cilia and 1 row of stiff laterofrontal cilia on each side. The shape of the basal membrane and the longitudinal muscles indicate that the tentacles are specialized for flicking movements directed towards the centre of the tentacle crown. Video observations of C. eburnea feeding on Rhodomonas cells showed characteristic velocity gradients around the tentacle crown. Particles in the central current gain the highest velocity at the entrance to the tentacle crown from where the speed decreases to zero in front of the mouth. Usually the path of a particle deviates from the downward course to a more outwards directed course (between the tentacles), where they may be trapped by the filter formed by the stiff laterofrontal cilia; the tentacle then makes a flick that brings the particle into the central current and further down towards the mouth. A survey of the literature shows that a similar mechanical filter mechanism occurs also in gymnolaemate bryozoans and their cyphonautes larvae, but that the particle-collecting mechanism of larvae and adults of phoronids, brachiopods, pterobranchs, and enteropneusts is different. The differences in structure and function between the tentacles of ectoprocts and those of phoronids, brachiopods and pterobranchs support the idea that the 2 types of tentacle crowns are not homologous. KEY WORDS: Ectoproct feeding · Ciliary filter · Sieving · Bio-fluid-mechanics · Video observations · Ultrastructure · Phylogeny Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 168. Publication date: July 09, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

SETTLEMENT IN FLOW: UPSTREAM EXPLORATION OF SUBSTRATA BY WEAKLY SWIMMING LARVAE

Exploration may play a crucial role in habitat choice by larvae of benthic organisms. Experiments testing exploratory behavior of larvae in flow were conducted with cyphonautes larvae of the bryozoan Membranipora membranacea. The response of the larvae to two flow parameters—flow direction and shear (i.e., velocity)—was examined by using two different substratum morphologies (flat plate and cylinder), which induce distinct flow patterns. Settling cyphonautes larvae possess a mechanism of locomotion, in addition to swimming, which may facilitate exploration in flow conditions that otherwise would sweep the larvae away. The results show that cyphonautes larvae are able to explore substrata in all directions in flow velocities that are much faster than their locomotion speeds, and that their preferential motion is upstream. This behavior has been largely ignored to date despite its potential ecological importance. For instance, upstream exploration may enable larvae to locate specific, obligatory settlement sites by tracking waterborne chemicals to their sources.

Comparative fertilization biology of gymnolaemate bryozoans

Locations and oogenic stages of eggs at the time of sperm-egg fusion were determined for nine gymnolaemate species exhibiting different reproductive strategies with respect to site of embryonic development (e.g., water column, introvert, embryo sac, or ovicell) larval type, and zooid sexuality. Ovarian, coelomic, and recently spawned oocytes obtained from freshly collected colonies between 1988 and 1995 were stained with aceto-orcein and examined for the presence of a sperm nucleus. All nine species are shown to have a similar fertilization biology in which sperm fuse with eggs in or near ovaries and egg activation is delayed until eggs are spawned. In species such as the etenostomeAlcyonidium sp. and the cheilostomeElectra pilosa (Linnaeus, 1767), which produce marierons oocytes that are spawned into the water column and have cyphonautes larvae, sperm fuse with late growth stage ovarian oocytes after germinal vesicle breakdown (GVBD) at or near ovulation. In species that produce few oocytes, brood embryos, and release coronate larvae, sperm fuse with late growth stage ovarian primary oocytes before GVBD, as in the ctenostomeBowerbankia gracilis Leidy, 1855, or with very early growth stage ovarian primary oocytes, as in the cheilostomesCribrilina corbicula (O'Donoghue, 1923),Dendrobeania lichenoides (Robertson, 1900),Hippodiplosia insculpta (Hincks, 1882),Schizoporella serialis (Heller, 1867),T ricellaria gracilis (Smitt, 1867), andWatersipora arcuata Banta, 1969. Fertilization success was high in all nine species, with 83 to 100% of oocytes at an appropriate oogenic stage containing a sperm nucleus or early male pronucleus. Gymnolaemate bryozoans may maintain high levels of fertilization success by: (1) concentrating spawned sperm from the water column using colony feeding currents; (2) localizing sperm-egg encounters in or near the ovary, (3) using sperm when available by permitting sperm to fuse with early growth stage oocytes; and (4) selfing.