Valve Mantle Research Articles

Examination and comparison of Fragilaria candidagilae sp. nov. with type material of Fragilaria recapitellata, F. capucina, F. perminuta, F. intermedia and F. neointermedia (Fragilariales, Bacillariophyceae)

Fragilaria candidagilae Almeida, C. Delgado, Novais & S. Blanco is a new araphid diatom species, described from samples collected in central and southern Portugal (SW Europe). Fragilaria candidagilae has linear-lanceolate valves with strongly capitate apices, without spines, and alternate punctate striae. This taxon presents siliceous plaques on the valve mantle edge, two apical pore fields in the poles and siliceous depositions on the outer areolar openings in the form of rounded floating disks. The morphology of the new diatom species is documented by light and scanning electron micrographs and discussed in detail, including a morphological comparison with the type material of similar taxa such as Fragilaria recapitellata, F. capucina, F. intermedia, F. neointermedia and F. perminuta to confirm it as a new species. Statistical comparison of morphometric characters and valve shape analysis were based on at least 20 valves. Ecological notes were also included. Considering morphology and morphometry, together F. candidagilae is clearly different from other species.

Two new species of Mastogloia Thwaites ex W. Smith (Bacillariophyceae) from Sawa Lake, southern Iraq

Two new species of the genus Mastogloia are described. Mastogloia sawensis sp. nov. and M. vestigiostriata sp. nov. were encountered as epiphytes on Chara sp. which covers the sediment of Sawa Lake, an isolated saline water body in southern Iraq. Mastogloia sawensis belongs to the section Lanceolatae and is closely similar to M. lanceolata but differs in raphe curvature, areolae shape and arrangement, and the presence of rounded pores at the junction of the partecta. Mastogloia vestigiostriata resembles under light microscopy to M. lyra and M. braunii but shows differences in several features including valve mantle structures, H-shaped lateral hyaline area, siliceous flanges and partectal formation. This study gives morphological details on the ultrastructure of the new species and provides a detailed comparison with all related taxa.

Staurosirella acidophilasp. nov., a New Araphid Diatom (Bacillariophyta) from Southeastern Brazil: Ultrastructure, Distribution and Autecology

Abstract A new diatom species, Staurosirella acidophila, is described from surface sediments and phytoplankton samples from tropical reservoirs in Sao Paulo, Brazil. Description of the new taxon is based on morphological characteristics observed using light (LM) and scanning electron microscopy (SEM). The new species is characterized by having rhombic-lanceolate valves with acuminate to rostrate ends, striae uniseriate, uninterrupted from valve face to valve mantle and areolae elongated, slit-like. Double line of incipient spines is for the first time reported for the genus Staurosirella. It belongs to the group of species morphologically related to Staurosirella pinnata sensu auct. non null. and shares some resemblance with species currently belonging to the genus Punctastriata. Comparison with similar species currently ascribed to the genera Punctastriata, Staurosira and Staurosirella are provided. The new species is described from sites that represent good ecological status (low nutrient concentrations...

A morphometric diagnosis using continuous characters of Pinnunavis edkuensis, sp. nov. (Bacillariophyta: Bacillariophyceae), a brackish-marine species from Egypt

Pinnunavis edkuensis is reported as a new diatom species from Egypt from brackish and marine habitats. Its description and diagnoses focus on 12 continuous morphological characters: valve breadth, valve mantle shape and surface area, axial-central area shape and surface area, axial area breadth, distal and proximal interstriae distances, striae slopes, magnitude and position of maximal slope along a semivalve transect, and inter-raphe distance. These characters are considered along their ontogenetic trajectories, using a size vector, by means of regression analyses. Shape was assessed using geometric morphometric methods. Diagnostic comparisons of P. edkuensis were made with P. yarrensis, for which a lectotype was chosen and Grunow’s unpublished description and drawings presented, and P. zalatii, a new name replacing the illegitimate name, Navicula aegyptiaca. P. edkuensis was demonstrated to be a distinct group compared to these two similar species using 11 of the 12 characters. The diagnoses emphasize species recognition by means of anova, regression and randomization analyses and specimen determination primarily by means of regression-based prediction intervals. Additional comments are made on the statistical nature of gaps associated with characters described by discrete or continuous variables, the importance of reporting sample sizes as part of diatom diagnoses and other comparisons, and the role of size in specimen comparability and taxon identification. The generic distinctness of Pinnunavis and Pinnularia is discussed based on a preliminary cladistic analysis of morphological characters.

Nupela troglophila sp. nov., an aerophilous diatom (Bacillariophyta) from the Bossea cave (NW Italy), with notes on its ecology

Nupela troglophila sp. nov. is described from epilithic and epiphytic samples collected around the artificial lighting system in the Bossea cave, SW Alps (NW Italy). The morphological features of the new species are described and documented through light microscopy and scanning electron microscopy analysis. A comparison with morphologically similar taxa is provided. Nupela troglophila belongs to the group of the small, elliptical-lanceolate species of the genus Nupela. The key feature that distinguishes it from all the other taxa belonging to this genus is the shape of the distal raphe fissures, always laying on the valvar surface, strongly deflected on the same side, but never reaching the valve mantle. The ecological preferences of the most abundant diatom species are explored through the ecological optimum calculation and the Outlying Mean Index (OMI) analysis. Within the Bossea cave, N. troglophila seems to prefer humid and warm sites. The highest abundance was reached on wet walls characterized by low light conditions. Nupela troglophila was generally associated with Humidophila pyrenaica that showed the same pattern of distribution in the cave and similar relative abundance. On the contrary, N. troglophila showed its lowest densities when Humidophila contenta was abundant. Until now, N. troglophila has been recorded only in the type locality.

Morphology and phylogeny of four species from the genus Bacteriastrum (Bacillariophyta)

:Four colonial species of the multipolar centric diatom genus Bacteriastrum – B. furcatum, B. hyalinum, B. jadranum and B. mediterraneum – were investigated using field samples from the Adriatic Sea and cultured strains obtained from these samples. Morphology and frustule ultrastructure were examined using light and electron microscopy, and nuclear-encoded large-subunit (LSU) rDNA sequences were obtained from the strains. The description of B. jadranum has been emended based on a novel mechanism of colony formation in Bacteriastrum in which cells are joined through an organic cell jacket which holds together cells in chains. Descriptions for two of the three other species were supplemented; vegetative cells of B. hyalinum have short Y spinules on the fused part of the setae and T-shaped outgrowths, and the spores of this species possess a ring of puncta and a granular surface on the exterior side of the primary valve mantle. Specific for B. furcatum is the location of pores scattered around the setae bases. No unique ultrastructural character was found for B. mediterraneum. Phylogenetic results grouped the sequences of the four species in a clade in which B. furcatum (section Sagittata) and B. hyalinum (section Isomorpha) formed a clade as sister to a clade with B. jadranum (section Isomorpha) and B. mediterraneum (section Sagittata). Apparently, neither section was monophyletic, and the supposed defining features of isomorphic terminal setae in Isomorpha and dimorphic ones in Sagittata were not synapomorphies. Nonetheless, the genus Bacteriastrum itself remained monophyletic.

Scanning electron microscopic investigation of Vanhoeffenus antarcticus Heiden from type material

Vanhoeffenus antarcticus was described by Heinrich Heiden from a net sample taken from 385 m depth by the Gauss expedition (First German Antarctic Expedition) while frozen in pack ice near the Antarctic continent in the austral summer of 1902–3. Valves of this peculiar diatom have only ever been observed in preparations from this locality and only using light microscopy, but an electron microscopy study of this taxon has become possible now that some surviving material from the Gauss expedition has been recovered. Our scanning electron microscopy observations show the presence of a radially arranged system of marginal chambers, connected to hollow radial rays and continuing through unusually long processes to the inside of the cell. Another unique characteristic of this taxon is a marginal ring of pillars bearing hooks rising from the valve mantle–valve face boundary, previously interpreted (based on light microscopy) as a ring of T-shaped spines. However, despite the improved understanding of its valve structure, the systematic position of this taxon and its biology remain enigmatic.

Aulacoseira veraluciae sp. nov. (Coscinodiscophyceae, Aulacoseiraceae): a common freshwater diatom from Brazil

Examination of samples from different aquatic environments from Brazil revealed the presence of a new Aulacoseira species. Aulacoseira veraluciae Tremarin, Torgan & T. Ludwig is described and illustrated with light and scanning electron microscopy, and its morphology compared with that of similar species, such as A. muzzanensis (Meister) Krammer, A. granulata (Ehrenberg) Simonsen and A. agassizii (Ostenfeld) Simonsen. The new species is characterized mainly by the straight pervalvar rows of areolae, morphology of the linking spines, shape and position of the rimoportulae on the valve mantle, deepness and thickness of the ringleiste.

Molecular Phylogeny of Amphora sensu lato (Bacillariophyta): An Investigation into the Monophyly and Classification of the Amphoroid Diatoms

Amphora sensu lato encompasses a large group of raphid diatoms, diverse in both form and ecology. The defining feature of this group has been an extreme asymmetry of the valve mantle and girdle bands, bringing both faces of the cell onto a single plane. Although this 'amphoroid' structure has long been the diagnostic feature and thus considered 'conservative' for the group, many have argued that the diversity of forms presently assigned to Amphora likely does not represent a monophyletic group. With the exception of several taxonomic transfers and the recent elevation of Halamphora to the level of genus, much of Amphora classification has remained unchanged for over 100 years. This study presents a phylogenetic analysis of Amphora s.l. based on a concatenated molecular alignment including the nuclear marker SSU rDNA and the chloroplast markers rbcL and psbC. These results are discussed within the framework of the current classification system of Amphora and Halamphora and lay the groundwork for a taxonomic revision of the group based on monophyly. The results of this analysis demonstrate that the genus Amphora is polyphyletic and that lineages assigned to the genus are distributed widely across the raphid diatom tree of life. The feature of amphoroid symmetry appears to have evolved independently several times. We discuss the nature of conservative characters in the raphid diatoms and their usefulness as a guide to phylogenetic relationships.

Syvertsenia iberica (Cymatosiraceae): a new estuarine diatom genus characterized by the position of its process

Diatom assemblages were studied along an intertidal transect in the lower Guadiana River Estuary (South-Eastern Portugal). The analyses of the assemblages by means of light and scanning electron microscope revealed a new diatom genus and species, Syvertsenia iberica. Syvertsenia was found in three out of eighteen of the samples analysed in the transect. The proposed new genus belongs to the family Cymatosiraceae, which is characterized by the presence of two distinct ocelluli. In common with other genera belonging to the subfamily Cymatosiroideae, the new genus shows heterovalvy and morphological similarity to Cymatosira, Campylosira and Plagiogrammopsis. In terms of ultrastructure, the features which identify these diatoms as a new genus are its linear valve outline, protracted to distinctly set off apices and also the distribution pattern of areola. Furthermore the position of the tubular process on a valve mantle extension, allows an easy distinction from other Cymatosiroideae. Syvertsenia iberica is a benthic epipsammic diatom whose ecological and geographical distribution requires more investigation.

Diatoms (Bacillariophyceae) from the Bolivian Altiplano: three new araphid species from the Desaguadero River draining Lake Titicaca.

Three new araphid diatom species, Pseudostaurosira decipiens E. Morales, G. ChĂĄvez et Ector, P. sajamaensis E. Morales et Ector and Staurosira kjotsunarum E. Morales, Novais et Ector are described from a single sample taken from the Desaguadero River in the Bolivian Altiplano. These species clearly belong in their respective genera as evidenced by their morphological features studied using light (LM) and scanning electron microscopy (SEM). Pseudostaurosira decipiens is unique in its genus because of the combination of lanceolate-shaped valves with central area, well-developed spines lacking ligulae, siliceous deposits on outer and inner areolar openings similar to flaps, and the inner rounded structure of the apical pore fields. Pseudostaurosira sajamaensis is different from other species of Pseudostaurosira due to its elliptic to lanceolate valves bearing a wide central sternum, spines with developed ligulae and bilobed flaps, robust volae and reduced or absent apical pore fields. Staurosira kjotsunarum is unique within Staurosira in having elevated costae on both external and internal views, narrowly spatulate spines that hold onto areolae of neighboring valves along a chain, and striae composed of round poroids underneath the apical pore fields on the valve mantle. The three species are compared with morphologically similar taxa and a brief analysis of the richness found in the studied sample in the context of previous publications on diatoms from the Andes and contiguous regions is presented.

Cavernosa kapitiana (Bacillariophyceae): biogeography and morphology of the different life cycle stages

The monospecific diatom genus Cavernosa is known from only two locations: Kapiti Island off the west coast of New Zealand and Ile de la Possession, Crozet Archipelago, in the southern Indian Ocean. Cavernosa kapitiana Stidolph is a chain-forming diatom with cylindrical frustules having an elongated valve mantle. We provide a description of the different life-cycle stages (normal frustules, globular initial cells, bell-shaped initial cells, first daughter cells of initial cells) of C. kapitiana based on examination of new material from Ile de la Possession and material from the type locality on Kapiti Island. The most remarkable morphological features include the complex valve face structure composed of pores, granules and ridges, the subdivision of the valve interior into marginal caverns, the complex structure of the mantle and girdle, and the presence and morphology of rimoportulae. The study concludes with an emended species description of C. kapitiana.

Marine necklace‐chain Fragilariaceae (Bacillariophyceae) from Guam, including descriptions of Koernerella and Perideraion, genera nova

SUMMARYLight microscopy (LM) and scanning electron microscopy (SEM) studies of necklace‐chain forming colonial diatoms from benthic habitats in Guam revealed five species. Bleakeleya notata (Grunow in Van Heurck) Round is widespread and well‐known. Asterionella notata var. recticostata Körner has been reported only twice before; we describe the plastids for the first time. On phylogenetic grounds we assign A. notata var. recticostata to a new genus, Koernerella, and emend the description of Bleakeleya. Three new species belonging in a new genus, Perideraion, are described as P. montgomeryi, P. decipiens and P. elongatum. Cultures from single‐cell isolates yielded four gene sequences for three of these taxa. The genera are easy to identify in the LM and SEM. Perideraion differs from Bleakeleya and Koernerella in having two large H‐shaped plastids, as reported for Asterionellopsis and Asteroplanus, and is further distinguished from all these genera by the following character set: a distinct rim around the basal field of circular pores, an apical rimoportula laterally on the valve mantle, pores in the valves that are unlike those in the basal pore field, and absence of apical slits. Although the basal pole attachment and colony morphology seem synapomorphic, molecular evidence suggests that the Bleakeleya‐Koernerella‐Perideraion clade is separate from the Asterionellopsis‐Asteroplanus clade and these five genera do not form one monophyletic group. It remains to be seen whether they are part of a somewhat larger group at the base of the araphid grade or if the genera we studied are truly separate.

Pliocaenicus tanimurae, a new Pliocene diatom species from Aguni Island, Okinawa Prefecture, southwestern Japan

Pliocaenicus tanimurae sp. nov., from Early Pliocene sediment of the Fudenzaki Formation, Aguni Island, Okinawa Prefecture, southwestern Japan is described here. The new species is round to elliptical with a slightly tangential undulated valve face. Valve face of the elliptical valves are more elliptical than the valves themselves. Several valve face fultoportulae in the valve center form a circle. Costae alternate thicker (sometimes slightly recessed) and thinner with mantle fultoportulae located on slightly recessed thicker costae. Both valve face and mantle fultoportulae have three satellite pores. Alveoli have centrifugal ‘roofing over’. One rimoportula is located near the edge of the marginal area of the valve face at the base of a costa. The new species is shown in light microscopy and scanning electron microscopy photographs and compared with similar taxa of P. costatus (Loginova, Lupikina & Khursevich) Flower, Ozornina & A.I.Kuzmina, P. seczkinae Stachura-Suchoples, Genkal & Khursevich and P. omarensis (Kuptsova) Stachura-Suchoples & Khursevich.

Ultrastructure and distribution of Aulacoseira gessneri

Aulacoseira gessneri (Hustedt) Simonsen has been mentioned rarely in the literature and its ultrastructure has not yet been investigated. The species was originally described from an Amazonian river, and its occurrence is still restricted to Brazilian environments. Specimens, found in Pantanal of Mato Grosso eutrophic lakes, were described and illustrated using optical and electron microscopy, and its morphology compared with similar species, A. distans (Ehrenberg) Simonsen and A. muzzanensis (Meister) Krammer. Aulacoseira gessneri presented the following diacritical characteristics: long filaments joined by small connection spines, elongated separation spines, valve mantle ornamented by straight striae composed of areolae usually round, ringleiste poorly developed, and row of sessile rimoportulae near the collum. The species reached high biomass (11–12 mg L−1) both during the high and low water periods in Pantanal lakes.

THE STUDY ON MORPHOLOGICAL TAXONOMY OF <I>PSEDUO-NITZSCHIA PSEUDODELICATISSIMA</I> COMPLEX

Increasing evidence show that cryptic and pseudo-cryptic species are widespread in several diatom taxa. This is the case with the genus Pseudo-nitzschia, which includes chain-forming pennate diatoms that bloom both in coastal and open ocean waters. In the last years, up 10 new species have been described on the basis of morphological and mo-lecular investigations, and some of them are only distinguishable on the basis of minute ultrastructural features of their siliceous frustulae. This is the case of P. pseudodelicatissima complex. It has been confirmed that P. pseudodelicatissima complex was a kind of pelagic diatom species which distribute commonly in Chinese coastal waters. Because of few subtle morphological features which just could be observed under electronic microscope (EM) among P. pseudodelica-tissima complex taxa, it is greatly difficult to reach accurate identification and there are many debates at present. For clarifying the species diversity of P. pseudodelicatissima complex and its dominant species in Daya Bay, water and net samples were collected from six stations in summer (August), 2007. All samples were fixed with Lugo’s solution in situ and brought back to the laboratory. Then, they were concentrated to a final volume about 2—10 mL by settlement over-night for several times. These samples could be observed and analyzed under light microscope. For observation under transmission electron microscope, subsamples were taken and treated through several steps. Firstly, after dropped into same volume of concentrated H2SO4, these samples were boiled in the water bath for about 15—20 minutes to remove the organic materials. Secondly, these samples should be washed to neutrality with distilled water for several times. Then, these samples could be observed, identified, photographed and counted under transmission electron microscope. Including six species, P. caciantha Lundholm, Moestrup Hasle, P. calliantha Lundholm, Moestrup Hasle, P. cus-pidata (Hasle) Lundholm, Moestrup Hasle, P. mannii Amato Montresor, P. pseudodelicatissima (Hasle) Lundholm, Hasle Moestrup and P. sinica Qi Wang, P. pseudodelicatissima complex were found. And P. caciantha, P. callian-tha, P. mannii were identified as three newly recorded diatom species for China. Along with LM and TEM photos, the detailed morphological description, habits and ecological distribution of these six species were given in this paper. Si-multaneously, the taxonomic comparison among resembling species were made. The six species described in this paper have morphological features in common: the long and slender valves, the present of a larger central interspace, the uniseriate striae, the similarity of the structure of the valve face and the valve mantle, and the hexagonal perforation pattern of the poroid hymen. However, several other features such as structure of the poroid hymen, density of fibulae and striae, the width and shape of valves, and the structure of the cingular bands differed among the species and could be used for differentiating these six species from each other. After investigation of the cell abundance of each species, it is concluded that the most common species distributing in Daya Bay is P. calliantha, not P. pseudodelicatissima which has been reported formerly.

Description ofConticribra tricircularis, a new genus and species of Thalassiosirales, with a discussion on its relationship to other continuous cribra species ofThalassiosira Cleve (Bacillariophyta) and its freshwater origin

A new diatom genus Conticribra is erected to accommodate C. tricircularis, described from a freshwater Pliocene deposit in Trout Creek, Oregon (USA). The genus accommodates species possessing: (i) loculate areolae with (semi-) continuous cribra; (ii) non-plicated valve face; (iii) rimoportula located on the valve mantle, replacing a fultoportula. Conticribra tricircularis has no valve face fultoportulae and can easily be distinguished by its marginal fultoportulae with four satellite pores arranged in three rings. Three species are transferred to the new genus from Thalassiosira sensu lato. Using evidence from the fossil record and recent molecular data, a hypothesis concerning the freshwater origin of Conticribra is discussed.

Comparative Morphology of the Concave Mirror Eyes of Scallops (Pectinoidea)*

The unique, double-retina, concave mirror eyes of scallops are abundant along the valve mantle margins. Scallops have the most acute vision among the bivalve molluscs, but little is known about how eyes vary between scallop species. We examined eye morphology by immunofluorescent labeling and confocal microscopy and calculated optical resolution and sensitivity for the swimming scallops Amusium balloti (Bernardi, 1861), Placopecten magellenicus (Gmelin, 1791), Argopecten irradians (Lamarck, 1819), Chlamys hastata (Sowerby, 1842), and Chlamys rubida (Hinds, 1845) and the sessile scallops Crassadoma gigantea (Gray, 1825) and Spondylus americanus (Hermann, 1781). We found that eye morphology varied considerably between scallop species. The eyes of A balloti and P. magellenicus had relatively large lenses and small gaps between the retinas and mirror, making them appear similar to those described previously for Pecten maximus (Linnaeus, 1758). In contrast, the other five species we examined had eyes with relatively small lenses and large gaps between the retinas and mirror. We also found evidence that swimming scallops may have better vision than non-swimmers. Swimming species had proximal retinas with inter-receptor angles between 1.0 ± 0.1 (A. balloti) and 2.7 ± 0.3° (C. rubida), while sessile species had proximal retinas with inter-receptor angles between 3.2 ± 0.2 (C. gigantea) and 4.5 ± 0.3° (S. americanus). Distal retina inter-receptor angles ranged from 1.7 ± 0.1 (A balloti) to 2.8 ± 0.1° (C. rubida) for swimming species and from 3.0 ± 0.1 (C. gigantea) to 3.6 ± 0.2° (S. americanus) for sessile species, but did not appear to correlate as strongly with swimming ability as proximal retina inter-receptor angles did. Finally, we found that optical sensitivity differed between species, measuring from 3 ± 1 (A. balloti) to 21 ± 10 µm2 · sr (C. hastata) for proximal retinas and from 2 ± 1 (C. gigantea) to 8 ± 5 µm2 · sr (C. hastata) for distal retinas. These differences, however, did not appear to correlate with ecological factors such as a scallop species' swimming ability, preferred substrate type, or range of habitat depth. In light of these and previous findings, we hypothesize that scallop distal retinas may perform tasks of similar importance to all species, such as predator detection, and that proximal retinas may perform tasks more important to swimming species, such as those associated with the visual detection of preferred habitats.

New species of the diatom genus Fryxelliella (Bacillariophyta), Fryxelliella pacifica sp. nov., from the tropical Mexican Pacific

SUMMARYDuring phytoplankton monitoring of coasts off Salina Cruz, Oaxaca, in the tropical Mexican Pacific, a new species, Fryxelliella pacifica sp. nov., was found and is described in this paper. The species is solitary, with cells of medium size, discoid with three relatively large ocelli on the valve face, located close to the margins (3–5 areolae from the margins) and placed symmetrically. Significantly, it possesses the morphological characters that distinguish the genus Fryxelliella from related genera: the presence of the ‘circumferential marginal tube’ (siphon marginalis), the external subcircular or subtriangular apertures at the valve margins, and the ‘juxtaposed rectangular plates’ in the valve mantle. The species that appears to be the most closely related is Fryxelliella floridana Prasad, an extant species and the type of the genus. However Fryxelliella pacifica differs from it (i) the size and shape of the cell; (ii) the size, location and structure of the ocelli (which additionally are not elevated); (iii) the shape and density of the subcircular to subtriangular marginal apertures; (iv) the external morphology of the rimoportulae (short process, two concentric tubes with the outer tube tip as a crown); and (v) it is marine rather than brackish. Externally the rimoportulae have a rather complex structure of two concentric tubes: the exterior tube has a tip divided like a crown. In spite of the fact this species was found in plankton samples, it is considered to inhabit sandy sediments (epipsammic) or as tychoplanktonic.

Scallops visually respond to the size and speed of virtual particles

The unique eyes of scallops are abundant along the right and left valve mantle margins. These eyes form images by reflection off a concave spherical mirror, and give scallops an angular resolution of around 2 degrees , far better than the 13-40 degrees angular resolution provided by the eyes of other bivalves. It has been argued that bivalve mantle eyes primarily act as predator detectors, but behavioral studies have suggested that vision may serve additional purposes in scallops. By placing specimens of the bay scallop Argopecten irradians (Lamarck 1819) in a tank with 5-10 cm s(-1) flow, showing them simulated images of moving particles, and recording their behavior, we tested whether visual cues may influence feeding behavior in these animals. We found that scallops opened their anterior mantle gapes significantly more often when they were shown 1.5x1.5 mm virtual particles (with angular sizes of 3.4 degrees ) than when they were shown 0.6x0.6 mm particles (1.4 degrees ; P<0.001) or no particles at all (P<0.05). We also found that scallops opened their anterior mantle gapes significantly more often when they were shown virtual particles moving at 2.5 cm s(-1) (P<0.01) or 5 cm s(-1) (P<0.05) than when they were shown particles moving at 10 cm s(-1). Because scallops must open their anterior mantle gapes to feed, our findings suggest that these animals may visually detect the size and speed of moving particles and use this information to help identify favorable feeding conditions.