Charles C. Lambert

Alien species and other notable records from a rapid assessment survey of marinas on the south coast of England

Arenas, F., Bishop, J.D.D., Carlton, J.T., Dyrynda, P.J., Farnham, W.F., Gonzalez, D.J., Jacobs, M.W., Lambert, C., Lambert, G., Nielsen, S.E., Pederson, J.A., Porter, J.S., Ward, S., Wood, C.A. (2006). Alien species and other notable records from a rapid assessment survey of marinas on the south coast of England. Journal of the Marine Biological Association of the United Kingdom, 86, (6), 1329-1337. Sponsorship: National Science Foundation grant IOB 0407527; Esme Fairbairn Foundation ALIENS project

Rapid Assessment Survey for exotic organisms in southern California bays and harbors, and abundance in port and non-port areas

In recent decades, the world has witnessed an array of harmful invasions by exotic marine organisms. To provide the public and policymakers with better information on the status of exotic species in southern California waters, and to assess differences between port and non-port areas, a Rapid Assessment Survey of selected habitat types in sheltered waters between San Diego and Oxnard was conducted in the summer of 2000. The objectives included comparing the prevalence of exotic species among habitats and regions and between recent and past surveys; obtaining reference data for future assessments of changes in invasion status and the effectiveness of prevention or control efforts; detecting new invasions; and documenting significant range extensions. Twenty-two sites were sampled to include the three major commercial port areas in southern California, non-port-area marinas and lagoon sites. Sampling included dock fouling and adjacent soft-bottom benthos, nearby intertidal sites, and selected subtidal lagoon habitats. Samples were collected by a variety of manual techniques. Sixty-nine of the species collected are exotic, including representatives from two algal divisions and six invertebrate phyla. Ascidians are especially well-represented (14 exotic species) and widely occurring, and some bivalves and bryozoans also occur very widely. The numbers and proportions of exotic taxa were not significantly greater in port areas than in non-port areas.

Tunicate Eggs Utilize Ammonium Ions for Flotation

Unlike most solitary ascidians, Corella willmeriana retains its eggs and embryos well past hatching. The early stages float to the top of the enlarged atrium from which they cannot escape. Ammonium ions replace other more dense substances in the cell sap of the float cells surrounding the embryo. Energy derived from glycolysis but not mitochondrial processes supports this process.

Fertilization-induced modification of chorion N-acetylglucosamine groups blocks polyspermy in ascidian eggs☆☆☆

Sperm bind to the chorion (vitelline envelope) of Ascidia nigra, which has many exposed N-acetylglucosamine (Glc Nac) groups. The Glc Nac-binding lectin wheat germ agglutinin (WGA), and p-nitrophenyl N-acetylglucosaminide block sperm binding as does N-acetylglucosaminidase digestion. Thus chorionic Glc Nac is an important component of the sperm receptor. Sperm bind to the chorion in increasing numbers during the first minute after fertilization, then bound sperm fall off to reach a low level by 2 min. Sperm unbinding is blocked by Glc Nac but not other sugars. Chorion binding of fluorescent WGA is also depressed after fertilization. Supernumerary sperm which have unbound from chorions gain a WGA binding site at the tip of the head, demonstrating the transfer of a Glc Nac group from chorion to sperm upon release. Glycerol-extracted eggs bind sperm during the first minute but fail to show the decline seen with living eggs. Supernatant obtained after fertilization of a dense egg suspension contains a trypsin-sensitive factor which modifies glycerinated eggs so that sperm binding is greatly inhibited. The block to polyspermy forms with the same kinetics as sperm unbinding, and is also sensitive to Glc Nac. This suggests that release of a chorion modifying factor removes Glc Nac residues from the chorion, releasing extra sperm and preventing polyspermy.

Mechanism of the block to hybridization and selfing between the sympatric ascidians Ciona intestinalis and Ciona savignyi

The solitary ascidians Ciona intestinalis and Ciona savignyi co‐occur in southern California harbors, but no hybrids have been recognized in nature. Numerous differences in their egg morphology were detected. Homologous (normal outcross) fertilization yielded 96–99% cleavage, where autologous (self) fertilization showed 3% and heterologous (hybrid) fertilization showed 0–1%. Acid treatment (pH 3.2) removed the block to selfing (P < 0.0001) but not hybridization for both species. Heterologous sperm bind to the vitelline coat (VC), but fail to penetrate. Enzymatic removal of the VC resulted in 91–97% cleavage with autologous and heterologous sperm (P < 0.0001). The vitelline coats of the two species differ in lectin binding to surface glycosides. Fertilization in both species is significantly inhibited by the lectins, fucose binding protein (P < 0.0001) and concanavalin A (P < 0.0001), and wheat germ agglutinin inhibits fertilization in C. intestinalis (P < 0.0001) but is without effect on C. savignyi fertilization. Self and hybrid blocks employ different mechanisms including glycoside composition and acid sensitivity. Mol. Reprod. Dev. 55:109–116, 2000.

Sperm Binding and Penetration during Ascidian Fertilization

Introduction In order for the sperm to enter and fertilize the egg it must first bind to the egg vestments, a step that is usually quite species-specific. Then, the sperm must penetrate several barriers to reach the egg surface where gamete fusion finally takes place. Most of the research into the mechanisms of these processes have involved the gametes of sea urchins and mammals. Ascidians, which come from near the base of the evolutionary lineage of chordates are, nevertheless, invertebrates, sharing the deuterostome heritage of the echinoderms. Given their intermediate evolutionary position we would expect that a study of fertilization in ascidians would be similar to mammals and sea urchins in some respects, but unique in others, yielding new ways of looking at the overall process. Ascidian eggs are unusually well-guarded by coverings which are barriers to the sperm arriving at the egg surface. The sperm first encounter a layer of follicle cells which function in egg flotation in some species (37) and are necessary for fertilization in others (26, 9). After passing through the narrow clefts between these cells, the sperm binds to the surface of the vitelline coat (VC) or chorion. Sperm then pass through the VC and the perivitelline space before they finally fuse with the oocyte plasma membrane. (Within the perivitelline space are the test cells). These coverings are everybit as complex as those of the mammalian egg, yet the sperm is among the simplest known. In this review we consider how this seemingly simple sperm manages to arrive at the surface of such a well-guarded egg.

Ascidian eggs block polyspermy by two independent mechanisms: One at the egg plasma membrane, the other involving the follicle cells

Many ascidians live in clumps and usually release sperm before the eggs. Consequently, eggs are often spawned into dense clouds of sperm. Because fertilization by more than a single sperm is lethal, ascidians have evolved at least two successive blocks to polyspermy: the rapid release of a glycosidase that inhibits sperm binding to the vitelline coat (VC) and a subsequent change in membrane potential that prevents supernumerary sperm–egg fusion. This paper shows that (1) these two blocks can be uncoupled by the use of suramin, and (2) most of the glycosidase appears to be from the follicle cells, which are accessory cells on the outside of the egg VC. Phallusia mammillata eggs initially bind numerous sperm but, after the glycosidase is released, only a few additional sperm bind. Intact eggs in 20 μM suramin release glycosidase, but the electrical response is inhibited; sperm swim actively and bind to the VC but fail to penetrate. Suramin treatment is completely reversible; intact eggs exhibit the electrical response an average of 11 minutes after the drug is washed out. Sperm must contact the follicle cells before passing through the VC; eggs with the VC removed and fertilized in the presence of 20 μM suramin show the electrical response 35% of the time, thus VC removal enhances sperm entry. Like the intact eggs, 100% of the naked eggs respond electrically to fertilization after the drug is washed out. Follicle cells that are isolated by calcium magnesium free seawater and then returned to complete seawater release N‐acetylglucosaminidase activity in response to sperm. Thus, these eggs have two blocks to polyspermy that operate in sequence: an early first block resulting from enzymatic modification of the VC by N‐acetylglucosaminidase released primarily from follicle cells and a second electrical block operating at the egg plasma membrane level and requiring sperm–egg fusion. Mol. Reprod. Dev. 48:137‐143, 1997.

Spicule formation in the solitary ascidian, Herdmania momus

Two types of calcareous spicules occur abundantly in Herdmania momus, a solitary pyurid ascidian with a worldwide warm water distribution. The large spindle‐shaped body spicules are 1.5–2.5‐mm long and are located primarily in the mantle, siphons, and branchial basket. Each body spicule possesses 100 or more rows of overlapping, unidirectional fringing spines. Numerous body spicules occur regularly spaced within a long common sheath of complex structure, and there are many sheaths per animal. Between neighboring body spicules and overlying the fringing spines are the tightly connected pseudopodial sclerocytes. Spine formation is hypothesized to occur within these cells. The body spicules apparently continue to increase in size throughout the animals life.

The role of actin and myosin in ascidian sperm mitochondrial translocation

Fertilization-related sperm mitochondrial movement occurs at a rate comparable to other actin-myosin-driven movements and is inhibited by cytochalasin B and N-ethyl maleimide in Ascidia ceratodes sperm. F-actin was demonstrated in the tails and mitochondria using NBD-phallacidin fluorescence. Both actin and myosin were also detected on the mitochondrion and in the tail by indirect immunofluorescence. Western blot analysis verified the presence of these proteins. Boltenia villosa and Cnemidocarpa finmarkiensis also have mitochondrion and tail localized actin and myosin. In the tails of all 3 species the fluorescence takes the form of discrete spots 0.25-0.5 micron apart. Boltenia and Cnemidocarpa sperm have additional actin at the tip of the head and additional myosin at the base of the head. The presence of actin and myosin on the mitochondrion and in the tail supports a means by which the force for mitochondrial movement is generated.

Molecular properties of Tunicate DNA.

Abstract DNAs from primitive chordates, the ascidians (Class Ascidiacea, subphylum Urochordata) have been characterized. Base compositions were inferred from thermal denaturation profiles and analytical CsCl pycnography. Base sequence complexity was estimated for DNA from one species, Ciona intestinalis. While average DNA base compositions were similar to those observed for other chordates (37–42 % guanine plus cytosine), considerable variation within the class was observed in density-satellite components. Renaturation kinetics verified that the haploid genome of C. intestinalis contains a minimum DNA mass of 9 · 1010 daltons. This compares well with chemical values determined previously35. From this correspondence we conclude that about 70 % of DNA in Ciona sperm is present as single copy sequences. The remaining 30 % renatures with rapid kinetics observed for other eukaryotic DNAs.