Higher Invertebrates Research Articles

Diet composition and trophic levels of marine mammals

Standardized diet compositions were derived for 97 species of marine mammals from published accounts of stomach contents as well as from morphological, behavioural and other information. Diet was apportioned among eight categories of prey types (benthic invertebrates, large zooplankton, small squids, large squids, small pelagic fishes, mesopelagic fishes, miscellaneous fishes and higher invertebrates). Trophic levels were estimated for each species of marine mammals and compared with published estimates derived using stable isotope ratios. Trophic levels ranged from 3.2–3.4 in baleen whales and sea otters, to 3.8–4.4 in most pinnipeds and odontocete whales, to 4.5–4.6 in killer whales. Such information can be used for ecosystem modelling and related studies.

Metabolic and membrane-altering toxins, molecular differentiation factors, and pheromones in the evolution and operation of endocrine-signalling systems.

The endocrine systems of vertebrates and higher invertebrates may have evolved functionally from as far back on the evolutionary scale as bacteria and early multicellular organisms and their biological communities, which have been shown to produce a variety of cyclic nucleotides, peptides, fatty acids, prostaglandins and sterols with endocrine-altering effects in primative as well as more highly evolved species.

Cloning of a putative voltage-gated sodium channel from the turbellarian flatworm Bdelloura candida.

The neuromuscular sodium currents of early invertebrates such as platyhelminths display distinctive kinetic and pharmacological properties. We have cloned a cDNA from the horseshoe crab flatworm Bdelloura candida that encodes a protein homologous to the primary subunit of voltage-gated sodium channels. The B. candida protein, named BdNa1, exhibits amino acid identity of 40-47% to sodium channels of vertebrates and higher invertebrates. BdNa1 has the multidomain structure characteristic of sodium channels, and is most highly conserved in the hydrophobic transmembrane segments and the regions that form the pore of the channel. Northern blot analysis confirms the presence of a 5.4 kb BdNa1 transcript in B. candida tissue. The information provided by analysis of the BdNa1 sequence offers insight into the physiology of platyhelminth sodium currents.

CHARACTERIZATION OF A SEROTONIN RECEPTOR IN THE CNIDARIAN RENILLA KOELLIKERI: A RADIOBINDING ANALYSIS

Serotonin (5-HT) binding sites in membrane preparations from the sea pansy Renilla koellikeri were identified using [3H]5-HT as radioligand and unlabelled 5-HT as displacer of specific binding. Saturation and kinetic studies revealed a mixed population of [3H]5-HT binding sites which as a whole displayed slow association kinetics, saturability, negligible dissociation and low affinity. The dopaminergic antagonist trifluoperazine specifically displaced the non-dissociated binding sites, allowing the characterization of a homogenous population of saturable sites exhibiting faster association and full dissociation. Scatchard analysis of this population revealed a KD of 23–34 nM and binding site density (Bmax) of 8.5–20.6 pmol/mg protein depending on body region. The pharmacological profile of the dissociable [3H]5-HT binding sites could not be categorized with that of any of the existing vertebrate and invertebrate 5-HT receptor subtypes in the current nomenclature. Especially noteworthy was the absolute inability of LSD, a ligand of choice for all hitherto identified invertebrate 5-HT receptors, to compete for the binding sites in sea pansy membrane preparations. It is proposed that these binding sites represent an evolutionary forerunner of the primordial 5-HT receptor that diversified as multiple subtypes in higher invertebrates and vertebrates. © 1997 Elsevier Science Ltd

Regulation of motility of cells from marine sponges by calcium ions

Sponges are known not to contain muscle and nerve cells. Since sponge cells are characterized by high motility we determined the effect of intracellular calcium ion concentration ([Ca 2+] i) on their motility. Addition of the Ca 2+ ionophore ionomycin to dissociated cells from the marine sponge Suberites domuncula caused in Ca 2+-containing artificial seawater (ASW) an increase in motility from 0.2 μm/min (absence of the ionophore) to 3.7 μm/min (presence of ionomycin). When the experiments were performed in Ca 2+-free medium, no effect of ionomycin could be observed. In parallel experiments the changes of [Ca 2+] i, using the dye Fura-2 were measured. The experiments revealed that ionomycin causes an influx of Ca 2+ into the cytosol of cells suspended in Ca 2+-containing artificial seawater. In contrast, if cells were suspended in Ca 2+-free artificial seawater, no increase of [Ca 2+] i occurred. Incubation of cells in the presence of inhibitors, specific for endoplasmatic Ca 2+-ATPase in mammals such as thapsigargin, cyclopiazonic acid, or 2,5 di-t-butylhydrochinone, did not influence the [Ca 2+] i if cells were suspended in Ca 2+-free artificial seawater. From these data we conclude that the [Ca 2+] i is primarily regulated through channels in the plasma membrane. In addition we summarize experimental evidence indicating that the [Ca 2+] i is involved in the control of cell motility. From the marine sponge Geodia cydonium a partial sequence of the myosin cDNA has been cloned. The deduced amino acid sequence comprises highest homology to nonmuscle myosin type II found in higher invertebrates and vertebrates. Taken together, these data show that the [Ca 2+] i level in sponge cells can be modulated by incubation with ionomycin. An increase of the Ca 2+ level parallels with higher motility of cells, suggesting an activation of Ca 2+-dependent protein kinases of myosin type II. Investigations on the ionomycin-activated influx of Ca 2+ into the cytosol revealed that predominantly the Ca 2+ channels in plasma membrane control the level of [Ca 2+] i.

Animal Mitochondrial DNA: Structure and Evolution

Publisher Summary This chapter describes structural features and evolution of metazoan mitochondrial DNA (mtDNA) molecules. Throughout the evolution of metazoa, gene content of mitochondria-genomes is highly conserved, as has the close packing of genes. Most of the occasional sequence expansions that have occurred, by way of either repeated or noncoding unique sequences, are found in the control or putative control region, rather than being dispersed between genes. Of the 13 open reading frames recognized in the human mtDNA molecules, four (COI, COII, COIII, and Cyt b) are originally identified in regard to the proteins they encode, from similarities of their predicted amino acid sequences to known amino acid sequences of bovine proteins, and predicted amino acid sequences of yeast mt-protein genes. Among mtDNAs of vertebrates and higher invertebrates, there are genes that overlap. Some overlaps are among the 3′ ends of two genes that are encoded in opposite strands of the molecule. The extent of size reduction within metazoan mitochondrial-transfer RNA (mt-tRNA) gene sets strongly correlates with the degree to which the more variable secondary structure element-forming regions of mt-rRNA genes are lost.

Morphology of Glial Blood‐Brain Barriers

Glial cells, in certain situations in the CNS, may become modified to form the structural basis of the blood-brain barrier. This occurs in more primitive vertebrates, such as the elasmobranch fish, and in some higher invertebrates. In the latter, the outermost glial sheath, often called the perineurium in avascular ganglia, substitutes functionally for the vascular endothelium of higher organisms. The intercellular junctions between the lateral borders of these modified glial or perineurial cells may be of several types. In nearly all cases, adhesive and communicating (gap) junctions are found together with an occluding junctional structure. The latter is assumed to be the morphologic basis of the observed blood-brain barrier. It varies in nature and may be one in which the adjacent cell membranes fuse, partially or completely, to form a classical tight junction, or it may be one in which the cell membranes remain separated by a distinct intercellular cleft. If the latter, the cleft may be straddled by columns or septal ribbons, between which a charged matrix substance may be found. Restrictive linker junctions, recently found to be the basis of the interglial barrier in cephalopod CNS, as well as that of myriapods, are characterized by cross-striations or columns which, in combination with charged residues, inherent either in them or in the associated extracellular matrix, slow down the entry of exogenous molecules. Septate junctions, which occur between glial cells in certain other invertebrates, exhibit intercellular septal ribbons, which do not prohibit paracellular transport of all substances but may slow down the passage of some by virtue of charged moieties. There is an association of cytoskeletal components with these septate, linker, and tight junctions; the role of the cytoskeleton in tight junctions, which can be seen by freeze fracture to be based on simple ridges in insects or a more complex network of them in arachnids, may also be important in the regulation of paracellular permeability. The structural details of the junctions in different groups are summarized and their physiologic implications discussed.

The Elementary Nervous System Revisited

Parker's theory of the origin of the nervous system is discussed along with later interpretations. Attention today has shifted from the cellular to the molecular level, and it has become clear that many of the molecules and mechanisms thought of as typically neuronal have homologs or counterparts in non-nervous cells and unicellular organisms. This applies to signalling chemicals, receptors, second messenger systems and ion channels, and also to the production of electrical events. Parker's view of sponges as a group lacking nerves but possessing independent effectors is still acceptable, but some sponges (and also higher animals) employ non-nervous signalling pathways to coordinate their effectors. Thus, nerves are not always necessary for coordinated behavior. Cnidarians like hydra have seemingly simple, two-dimensional nervous systems with little or no centralization, but even such systems can be surprisingly complex, and the more advanced cnidarians show neurophysiological specializations as sophisticated as those of many higher invertebrates. Examples of ingenious cnidarian solutions to behavioral problems are given. No existing animals have ‘elementary’ nervous systems if that term implies the existence of crude or inefficient functional adaptations

Isolation of L-3-phenyllactyl-Leu-Arg-Asn-NH2 (Antho-RNamide), a sea anemone neuropeptide containing an unusual amino-terminal blocking group.

Using a radioimmunoassay for the carboxyl-terminal sequence Arg-Asn-NH2, we have purified a peptide from acetic acid extracts of the sea anemone Anthopleura elegantissima. By classical amino acid analyses, mass spectrometry, and 1H NMR spectroscopy, the structure of this peptide was determined as 3-phenyllactyl-Leu-Arg-Asn-NH2. By using reversed-phase HPLC and a chiral mobile phase, it was shown that the 3-phenyllactyl group had the L configuration. Immunocytochemical staining with antiserum against Arg-Asn-NH2 showed that L-3-phenyllactyl-Leu-Arg-Asn-NH2 (Antho-RNamide) was localized in neurons of sea anemones. The L-3-phenyllactyl group has not been found earlier in neuropeptides of vertebrates or higher invertebrates. We propose that this residue renders Antho-RNamide resistant to nonspecific aminopeptidases, thereby increasing the stability of the peptide after neuronal release.

O-acetylation and de-O-acetylation of sialic acids: Sialic acid esterases of diverse evolutionary origins have serine active sites and essential arginine residues

We and others have recently described 9-O-acetyl-sialic acid esterase (9-O-Ac-SA esterase) activities that appear to be specific for removal of O-acetyl esters from the 9-position of naturally occurring sialic acids. We have now examined a variety of species for such enzymes and found them in vertebrates and higher invertebrates, but not in plants or in lower invertebrates. This evolutionary distribution correlates well with that of the sialic acids themselves. All of the 9-O-Ac-SA esterase activities tested were inhibited by diisopropyl fluorophosphate (DFP) in a dose-dependent fashion. This indicates that each of these enzymes has a serine active site similar to the well known serine esterases and serine proteases. Methyl esterification of the carboxyl group of 9-O-acetyl-N-acetylneuraminic acid significantly reduced the activity of all of the 9-O-Ac-SA esterases against the O-acetyl group. This indicates that each of these enzymes may recognize the negatively charged carboxyl group of the sialic acid. Enzymes that recognize anionic substrates frequently have an essential arginine residue (Riordan, J. F., McElvany, K. D., and Borders, C. L., Jr. (1977) Science 195, 884–886). We therefore studied the effects of the arginine-specific modifying reagents 2,3-butanedione and phenylglyoxal on 9-O-Ac-SA esterase activities from influenza C virus, human erythrocytes, rat liver, starfish gonads, and sea bass brain. All of these enzymes were inhibited in a dose-dependent fashion by both reagents, under conditions previously known to avoid nonspecific modification. In contrast, the typical serine proteases trypsin and kallikrein and the serine esterase acetylcholinesterase were not significantly affected, even by the highest concentrations of these reagents used. These data indicate that five 9-O-Ac-SA esterase activities from evolutionarily distinct origins all have serine active sites and essential arginine residues. We postulate that the arginine residue is involved in substrate recognition via the negatively charged carboxyl group of the sialic acids. Thus, these 9-O-Ac-SA esterase activities may be members of a previously undescribed class of serine esterase.

Ecological and Evolutionary Aspects of Integumentary Respiration: Body Size, Diffusion, and the Invertebrata

SYNOPSIS. Most animal phyla lack specialized respiratory surfaces and all phyla contain groups that, for some part of their life history, depend entirely upon integumental diffusion of respiratory gases. Animals that are diffusion-limited, yet function aerobically are generally small with large surface areas and there has been convergence for this among all phyla including the coelomate invertebrates. Acoelomates lack specialized respiratory structures but have highly modified integuments, functional specializations, and features ranging from symbioses to air gulping that compensate for diffusion limitation. The diversity of structures functioning for integumentary respiration is much greater among invertebrates than vertebrates. Among the higher invertebrates with respiratory surfaces, accessory integumentary O2 uptake is usually 20 to 50% of total respiration. The high diffusion constant of O2 in air minimizes boundary effects on gas transfer and permits larger body size, although this is limited by dry conditions. Terrestrial annelids and flatworms, both confined to moist habitats, are larger than aquatic forms which often have accessory gills. Size differences between terrestrial forms in these two phyla reflect the presence of a circulation in the annelids. Ontogenetic transitions from skin breathing to other respiratory structures occur among marine invertebrates and vertebrates. Vertebrates apparently exercise greater integratory control over integumental respiration through adjustment of ventilation and perfusion; however, it is not known if these processes occur in some invertebrates.

Comparative pathology of inflammation in the higher vertebrates (reptiles, birds and mammals)

Metchnikofrs original treatise and subsequent comparative studies of inflammation in animals established that the complexity of the inflammatory process increased with phylogeny (Dobberstein, 1960; Messow, 1960; Metchnikoff, 1891; Zwart, 1963). Inflammation in lower invertebrates is a localized response; in sponges and jellyfish, primitive mesodermal cells (amoebocytes) capable of phagocytosis are mobilized to the point of injury; healing is accomplished with collagen fibril proliferation and ectodermal hyperplasia. In earthworms, pathogens too large to be phagocytosed (e.g. metazoan parasites) are surrounded by coelomocytes and encapsulated in the coelomic cavity. Higher invertebrates, such as molluscs, react to noxious and infectious agents with granuloma-like lesions to which some of the participating leucocytes migrate from closed circulatory systems (Cooper, 1986; Sparks, 1985). This tendency for universal granuloma formation carries over to the vertebrates. Fish respond to most types of micro-organisms with granulomas (Wolke and Stroud, 1978); reptiles and birds appear to react to a wider spectrum ot infectious agents with granulomas than do mammals (Frye, 1981 b; Jortner and Adams, 1971). This article will deal with morphological comparisons of inflammation in the higher vertebrates (reptiles, birds, and mammals). Leucocyte morphology and function will be reviewed and the gross and microscopic appearances and relationships of inflammatory cells will be examined in reptiles and birds with emphasis on granuloma formation.

Conjugation of Organic Pollutants in Aquatic Species

Aquatic organisms can take up organic pollutants from their environment and subsequently excrete the pollutant or its biotransformation products (metabolites). Phase II (conjugation) biotransformation products are almost always less toxic than the unmetabolized organic pollutant. For many organic pollutants, the extent to which conjugates are formed is extremely important in determining the rate of excretion of the pollutant. This is because most conjugates (glycosides, sulfates, amino acid conjugates, mercapturic acids) are organic anions which are readily water-soluble and are rapidly excreted by fish (and probably higher invertebrates) by a combination of glomerular filtration and tubular transport. In this paper, each major conjugation pathway is discussed with respect to what is known about its occurrence in fish and aquatic invertebrates, both from in vivo and in vitro data. Although limited data are available, this paper also considers what is known about how each conjugation reaction affects the toxicity and potential for renal and biliary excretion of organic xenobiotic substrates.

Conjugation of organic pollutants in aquatic species.

Aquatic organisms can take up organic pollutants from their environment and subsequently excrete the pollutant or its biotransformation products (metabolites). Phase II (conjugation) biotransformation products are almost always less toxic than the unmetabolized organic pollutant. For many organic pollutants, the extent to which conjugates are formed is extremely important in determining the rate of excretion of the pollutant. This is because most conjugates (glycosides, sulfates, amino acid conjugates, mercapturic acids) are organic anions which are readily water-soluble and are rapidly excreted by fish (and probably higher invertebrates) by a combination of glomerular filtration and tubular transport. In this paper, each major conjugation pathway is discussed with respect to what is known about its occurrence in fish and aquatic invertebrates, both from in vivo and in vitro data. Although limited data are available, this paper also considers what is known about how each conjugation reaction affects the toxicity and potential for renal and biliary excretion of organic xenobiotic substrates.

87:6577 Conjugation of organic pollutants in aquatic species: James, M.O., 1987. Environ. Hlth Perspect., 71:97–103

Aquatic organisms can take up organic pollutants from their environment and subsequently excrete the pollutant or its biotransformation products (metabolites). Phase II (conjugation) biotransformation products are almost always less toxic than the unmetabolized organic pollutant. For many organic pollutants, the extent to which conjugates are formed is extremely important in determining the rate of excretion of the pollutant. This is because most conjugates (glycosides, sulfates, amino acid conjugates, mercapturic acids) are organic anions which are readily water-soluble and are rapidly excreted by fish (and probably higher invertebrates) by a combination of glomerular filtration and tubular transport. In this paper, each major conjugation pathway is discussed with respect to what is known about its occurrence in fish and aquatic invertebrates, both from in vivo and in vitro data. Although limited data are available, this paper also considers what is known about how each conjugation reaction affects the toxicity and potential for renal and biliary excretion of organic xenobiotic substrates.

Evaluation Techniques for Individualized Instruction: Revision and Summative Evaluation

The initiation of an information delivery system that differs from the typical lecture-laboratory format of a course always presents concerns for both the instructor and students. The success of a new system can only be measured through a careful summative evaluation process. This article describes the process of the gathering and analysis of summative data for a slide/audio-tape self-instruction program on animal diversity in an introductory zoology course. Included also are some aspects of the continuing process of review and refined revision of the instructional delivery system as it applies directly to summative evaluation. The self-instruction program involves five individual units covering important topics in animal diversity. These topics are taxonomy, animal protists (protozoans), lower vs. higher invertebrates, and chordates.

Problems in the Development of Cognitive Neuroscience Effective Communication between Scientific Domains

Could anything provide a philosophically convincing mark of the mental in simple organisms (Lloyd 1984)? Individual organisms’ capacities to modify behavior adaptively as a result of past encounters with the environment might mark the first step in the phylogeny of minds. The simplest examples of mental representation are likely to be found in the simplest forms of animal learning.The most scientifically rigorous test case of “bottom- up” strategies in cognitive neuroscience is provided by current studies of the cellular and molecular biology of associative learning in higher invertebrates, but particularly gastropod molluscs, snails or slugs (Quinn 1984). For the relevant neurobiological research community (Farley and Alkon 1985; Hawkins, Clark, and Kandel 1986), “Bottom-up” does not just mean letting one’s study of the properties of the nervous system control one’s analyses of animal behavior or cognition.

Neurotensin: Immunohistochemical Localization in Central and Peripheral Nervous System and in Endocrine Cells and its Functional Role as Neurotransmitter and Endocrine Hormone

The present study attempts to compile information on the possible physiologic role of the endogenous peptide neurotensin (NT) as a hormone and/or neurotransmitter. The methodological approach is immunohistochemical localization of NT in the entero-endocrine system as well as in the central and peripheral nervous systems. The results found in the three systems are first related to the pharmalogical and physiological findings in the literature. Subsequently their significance is discussed for each organ separately before attempting a final overall interpretation. Briefly, the present study reveals the following essential findings: The occurrence and distribution of NT-IR entero-endocrine cells (N-cells) in different mammals including man, as well as in representative members of all classes of vertebrates and higher invertebrates, are analyzed and evaluated morphometrically. The NT-IR cells in all investigated species are demonstrated to be of the open type. The innervation of paravertebral and prevertebral ganglia by NT-IR fibers is described; at least a portion of these fibers is thought to originate in NT-IR perikarya of the substantia intermedia of the spinal cord. The involvement of these NT-IR fibers in the regulation of systemic blood flow (hypertension) is suggested. The existence of NT-IR innervation of the gastro-intestinal tract is considered to be a general phenomenon. This notion is reaffirmed by phylogenetic investigation of the NT-IR enteric nerves. The pharmacological effects of NT in different portions of the gastro-intestinal tract, reported in the literature are related to the immunohistochemical localization of NT. In light of the present results, some of the effects of NT which were previously considered to be of an endocrine or paracrine nature - such as contraction of the guinea-pig ileum - are interpreted as effects of NT of neuronal origin. The specific NT-IR innervation of target cells in the exocrine pancreas (vascular smooth muscle, acinar cells) is demonstrated, and participation of NT-IR nerve fibers in regulation of the secretion of pancreatic juice is postulated. The innervation of the heart (coronary vasculature, myocardium, conduction system) by NT-IR fibers is demonstrated in various mammals and for the first time also in man. The cardiac NT-IR nerve fibers are thought to be the cytological substrate for different NT effects on heart action (coronary vasoconstriction, positive inotropy and chronotropy) reported in the literature.(ABSTRACT TRUNCATED AT 400 WORDS)

Muscle Histochemistry of the Planarian Dugesia tigrina (Turbellaria: Tricladida): Implications in the Evolution of Muscle

Muscle Histochemistry of the Planarian Dugesia tigrina (Turbellaria: Tricladida): Implications in the Evolution of Muscle

Molecular biology of learning: modulation of transmitter release.

Until recently, it has been impossible to approach learning with the techniques of cell biology. During the past several years, elementary forms of learning have been analyzed in higher invertebrates. Their nervous systems allow the experimental study of behavioral, neurophysiological, morphological, biochemical, and genetic components of the functional (plastic) changes underlying learning. In this review, we focus primarily on short-term sensitization of the gill and siphon reflex in the marine mollusk, Aplysia californica. Analyses of this form of learning provide direct evidence that protein phosphorylation dependent on cyclic adenosine monophosphate can modulate synaptic action. These studies also suggest how the molecular mechanisms for this short-term form of synaptic plasticity can be extended to explain both long-term memory and classical conditioning.