Herdmania Momus Research Articles

Solitary ascidians as predators of invertebrate larvae: evidence from gut analyses and plankton samples

Gut analyses of five ascidian species from the San Juan Islands, Washington, Chelyosoma productum Stimpson, Pyura haustor (Stimpson), Ascidia callosa Stimpson, Boltenia villosa (Stimpson) and Styela gibbsii (Stimpson) and five species from the Atlantic coast of Florida, Herdmania momus (Savigny), Ascidia curvata (Traustedt), Ascidia nigra (Savigny), Molgula occidentals Traustedt and Styela plicata (Lesueur), indicate that solitary ascidians consume a variety of invertebrate larvae. Analysis of plankton samples collected near aggregations of live ascidians and near mimic aggregations, however, indicate that the ascidians are not significantly depleting the local supplies of larvae. Temporal and spatial patchiness in larval supply combined with selective feeding by the ascidians and escape responses of larvae are invoked to explain the lack of small scale depletion effects.

RQ of benthic marine invertebrates

This study investigated an incubation method which employed simultaneous measurement of CO2 production and O2 consumption rates to calculate the RQ (respiratory quotient; CO2 production rate: O2 consumption rate) of individual benthic marine invertebrates. Carbon dioxide production rates were calculated from changes in CO2 concentration determined using seawater pH. O2 consumption rates were calculated from changes in O2 concentration with a correction applied for O2 flux across the air/water interface due to gaseous exchange. Species examined were Triphyllozoon sp. cf. moniliferum (MacGillivray 1860), a bryozoan; Herdmania momus (Savigny), a solitary ascidian; Poneroplax albida (Blainville 1825), a chiton; and Haliotis roei (Gray 1826), an abalone. Six individuals of each were collected on 14 November 1985 from the limestone walls of a cave in a nearshore reef off Marmion, Western Australia. After acclimation for 6 h in experimental conditions, rates of CO2 production and O2 consumption were measured. A minimum period of 4 h was required to obtain consistent RQ values for each species. The standard error (SE) of the (calculated) RQ ratio was 14 to 33% of the mean in incubations of 4 h, and less than 14% in incubations of 4 to 12 h. The RQ is commonly used as an indicator of unknown catabolic substrates by comparing it with biochemically determined limits for known substrates. This study provides a strong argument against using the RQ of individual animals to draw any conclusions about catabolic substrates. Unexplained variation in the components of the RQ of an individual, measured over short time periods, and the potential involvement of stored reserves in catabolism, over longer time periods, obscure the relationship between the RQ of individual animals and the ratio's biochemically determined limits.

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 animal's life. The tunic spicules are about one tenth the length of the body spicules. They have 20-40 rows of unidirectional nonoverlapping fringing spines and a mace-shaped spiny base that anchors them at the tunic surface. They form quickly in individual spicular envelopes inside the tunic blood vessels over a 4-5-day period. Each tunic spicule then leaves its surrounding envelope and blood vessel, passes into the tunic, and ultimately protrudes through the outer surface of the tunic. An organic covering inside the envelope closely adheres to the tunic spicules and stains with toluidine blue. Dissolution of the CaCO3 mineral phase by EDTA or EDTA-cetylpyridinium chloride-formaldehyde reveals an intricately patterned organic matrix within or upon which the spicules develop.

Protein binding of iron in blood plasma of the ascidian Herdmania momus

Blood of the ascidian Herdmania momus var. grandii (Kott, 1952) has typically a low cell haematocrit volume, <1% with a cell density of 12 000 to 15 000 cells mm-3. Non-dialysable solids in the plasma are 105±10 mg%. Iron-binding in the plasma has been investigated by fractionation of 59Fe-labelled plasma, using gel chromatography and electrophoretic procedures. Three fractions, identified as I, II and III in the order of their elution from a G-150 column, bind 59Fe in the ratio 60:15:15. The dominant fraction, I, was shown by electrophoresis on polyacrylamide gels to consist of two components in the ratio of ca. 80:20 and with similar electrophoretic mobilities. Dissociation of Fraction I by mercaptoethanol and sodium dodecyl sulfate gave on electrophoresis three components of molecular weights 17 000; 32 000 and 66 000. Fraction 1 contained 10% carbohydrate by weight as determined by the l-cysteine/sulphuric acid assay. These data are compared with other iron-binding systems such as transferrin and the siderophores. Phylogenetic aspects of the study are also discussed.

Vaterite: a mineralization product of the hard tissues of a marine organism (Ascidiacea).

X-ray diffraction and infrared absorption spectra show that the spicules of the common tropical ascidian, Herdmania momus, are mineralized with vaterite. These are the first strictly marine organisms known to normally precipitate vaterite. The biomineralization of vaterite may constitute another link between the urochordates and vertebrates. The vaterite of ascidian spicules immersed in natural seawater remains mineralogically unchanged for 1 year, which indicates that vaterite may be preserved transiently in marine sediments.

THE EFFECTS OF ACTINOMYCIN D ON MUSCLE CELLS OF ASCIDIAN EMBRYO.

The effect of actinomycin D on muscle cells development of the ascidian, Herdmania momus was studied ultrastructurally. No myofilament was formed when the drug was given at any stage before early tail-bud stage (stage 3). Some aggregates of myofilaments in various size were formed when the treatment was started at stage 4 (4.5 hr after fertilization at about 28°C). Above 60% of myofibrils of fully differentiated muscle cells were formed when the treatment was initiated at stage 5 (5 hr after fertilization). Muscle cells of the tadpoles treated from stage 7 (6 hr after fertilization), at which myofilaments were first detectable in normal development, differentiated almost normally. It is therefore suggested that most mRNAs for muscle proteins are synthesized preceding the onset of myofilament formation and are relatively stable. It is also suggested that mRNAs for myosin, actin and Z band materials are almost simultaneously synthesized. One of the characteristic features of the muscle cell development of the ascidian embryo is almost synchronous differentiation of relatively small numbers of cells (about 54-60 cells). The significance of these results is discussed in relation to mosaic natures of the muscle development.

Nitrogen Excretion in Ascidiacea

ABSTRACT The evidence for the occurrence of storage excretion in ascidians is reviewed. Most species probably store uric acid or purine bases in some form. The renal concretions of Ascidia nigra and Phallusia mammillata contain 50-60 % uric acid, the remainder of the concretion is unidentified but is non-nitrogenous and is not calcium carbonate. In Ascidiella aspersa the concretion is predominantly composed of calcium carbonate and there is no significant quantity of uric acid or purine base. Uric acid is also identified in Molgula manhattensis, Polycarpa obtecta, Pyura vittata and Herdmania momus. Storage excretion probably results from a deficiency in the uricolytic enzyme system. It is concluded that while protein metabolism is ammonotelic, purine meta-bolism is uricotelic or xanthotelic.