Soft-bodied Marine Invertebrates Research Articles

Validating a molecular clock for nudibranchs-No fossils to the rescue.

Time calibrated phylogenies are typically reconstructed with fossil information but for soft-bodied marine invertebrates that lack hard parts, a fossil record is lacking. In these cases, biogeographic calibrations or the rates of divergence for related taxa are often used. Although nudibranch phylogenies have advanced with the input of molecular data, no study has derived a divergence rate for this diverse group of invertebrates. Here, we use an updated closure date for the Isthmus of Panama (2.8 Ma) to derive the first divergence rates for chromodorid nudibranchs using multigene data from a geminate pair with broad phylogeographic sampling. Examining the species Chromolaichma sedna (Marcus & Marcus, 1967), we uncover deep divergences among eastern Pacific and western Atlantic clades and we erect a new species designation for the latter (Chromolaichma hemera sp. nov.). Next, we discover extensive phylogeographic structure within C. hemera sp. nov. sensu lato, thereby refuting the hypothesis of a recent introduction. Lastly, we derive divergence rates for mitochondrial and nuclear loci that exceed known rates for other gastropods and we highlight significant rate heterogeneity both among markers and taxa. Together, these findings improve understanding of nudibranch systematics and provide rates useful to apply to divergence scenarios in this diverse group.

Antioxidant and antibacterial activity test on a crude extract of sand (Holothuria atra) in Lemukutan water, Bengkayang District

Sea cucumbers are soft-bodied marine invertebrates from the Holothuroidea class whose habitat is in sandy areas. This study aims to determine the content of secondary metabolites in crude extracts of sea cucumber which have the potential as antioxidants and antibacterials. The type of sea cucumber used in this research is the sand sea cucumber (Holothuria atra). The research was carried out from October 2020-February 2021. Samples were taken using the exploratory method, the sea cucumber samples were processed with 5 treatments, namely cleaning and crushing sea cucumber samples, extraction using the maceration method, evaporation with a vacuum rotary evaporator, and drying using freeze-drying. The bioactive components found in sea cucumbers are alkaloids, flavonoids, saponins, and phenols. The antioxidant activity found in sea cucumbers has an IC50 1194 ppm which is classified as a weak antioxidant. The antibacterial activity found intraday sand sea cucumbers E. coli gave the highest inhibition zone at a concentration of 20% with an inhibition zone diameter of 20.08 mm while S. aureus gave the highest inhibition zone at a concentration of 30% with an inhibition zone diameter of 22.17 mm.

Histochemical detection of free thiols in glandular cells and tissues of different marine Polychaeta.

Either through differentiated glands or specialised individual cells, the coating epithelia of soft-bodied marine invertebrates are responsible for the secretion of a broad span of peptidic substances, from protective mucins to biocides. These secretions are characterised by the presence of cysteine-rich proteins and peptides, rendering a distinct histochemical signature of secretory epithelia. Through a histochemical procedure for fluorescence microscopy in paraffin sections, we performed a comparative assessment of the distribution of thiol-rich compounds in multiple epithelia of different species of intertidal Polychaeta, which revealed distinctive patterns of distribution that closely relate to ecology, morphoanatomy and physiology. The presence of free thiols was notorious in mucocytes and enzyme-plus toxin-secreting cells. Consequently, strong signals were recorded in the mucocytes of the parapodia of Nereis splendida, the epidermis and pharynx epithelium of Mysta picta and the venom glands of Glycera alba. The findings show an investment in mucus secretion in foragers such as Nereis and Mysta, especially the latter, which is not a native burrower, as a protective response and as lubricant for locomotion. Additionally, nereidids are believed to secret integumentary toxins for defence. On the other hand, Glycera is an ambush predatorial burrower whose behaviour entirely revolves around the delivery of venom making use of its four jaws. The results showed that the detection of thiol-rich compounds in histological sections can be a tool to identify potential toxin secretion and delivery structures, with important consequences for the bioprospecting of novel bioreactives from marine invertebrates for the purpose of drug discovery.

ITAG: an eco-sensor for fine-scale behavioral measurements of soft-bodied marine invertebrates

Soft-bodied marine invertebrates comprise a keystone component of ocean ecosystems; however, we know little of their behaviors and physiological responses within their natural habitat. Quantifying ocean conditions and measuring organismal responses to the physical environment is vital to understanding the species or ecosystem-level influences of a changing ocean. Here we describe a novel, soft-bodied invertebrate eco-sensor tag (the ITAG), its trial attachments to squid and jellyfish, and the fine-scale behavioral measurements recorded on captive animals. Tags were deployed on five jellyfish (Aurelia aurita) and eight squid (Loligo forbesi) in laboratory conditions for up to 24 h. Using concurrent video and tag data, movement signatures for specific behaviors were identified. These behaviors included straight swimming (for jellyfish), and finning, jetting, direction reversal and turning (for squid). Overall activity levels were quantified using the root-mean-squared magnitude of acceleration, and finning was found to be the dominant squid swimming gait during captive squid experiments. External light sensors on the ITAG were used to compare squid swimming activity relative to ambient light across a ca. 20-h trial. The deployments revealed that while swimming was continuous for captive squid, energetically costly swimming behaviors (i.e., jetting and rapid direction reversals) occurred infrequently. These data reflect the usefulness of the ITAG to study trade-offs between behavior and energy expenditure in captive and wild animals. These data demonstrate that eco-sensors with sufficiently high sampling rates can be applied to quantify behavior of soft-bodied taxa and changes in behavior due to interactions with the surrounding environment. The methods and tool described here open the door for substantial lab and field-based measurements of fine-scale behavior, physiology, and concurrent environmental parameters that will inform fisheries management, and elucidate the ecology of these important keystone taxa.

Integrative species delimitation in photosynthetic sea slugs reveals twenty candidate species in three nominal taxa studied for drug discovery, plastid symbiosis or biological control

DNA barcoding can highlight taxa in which conventional taxonomy underestimates species richness, identifying mitochondrial lineages that may correspond to unrecognized species. However, key assumptions of barcoding remain untested for many groups of soft-bodied marine invertebrates with poorly resolved taxonomy. Here, we applied an integrative approach for species delimitation to herbivorous sea slugs in clade Sacoglossa, in which unrecognized diversity may complicate studies of drug discovery, plastid endosymbiosis, and biological control. Using the mitochondrial barcoding COI gene and the nuclear histone 3 gene, we tested the hypothesis that three widely distributed “species” each comprised a complex of independently evolving lineages. Morphological and reproductive characters were then used to evaluate whether each lineage was distinguishable as a candidate species. The “circumtropical” Elysia ornata comprised a Caribbean species and four Indo-Pacific candidate species that are potential sources of kahalalides, anti-cancer compounds. The “monotypic” and highly photosynthetic Plakobranchus ocellatus, used for over 60years to study chloroplast symbiosis, comprised 10 candidate species. Finally, six candidate species were distinguished in the Elysia tomentosa complex, including potential biological control agents for invasive green algae (Caulerpa spp.). We show that a candidate species approach developed for vertebrates effectively categorizes cryptic diversity in marine invertebrates, and that integrating threshold COI distances with non-molecular character data can delimit species even when common assumptions of DNA barcoding are violated.

Growth promotion of the juvenile clam, Ruditapes philippinarum, on sugars supplemented to the rearing water

Soft-bodied marine invertebrates are known to have the ability to uptake dissolved organic matter, but actual benefits to growth of these organisms have not been demonstrated. In the present study, the effects of sugars supplemented to the rearing water were tested on juveniles of the clam, Ruditapes philippinarum. Culture water supplemented with glucose at 10 and 100 mg l − 1 significantly promoted soft tissue growth of the clam. In contrast, maltopentaose and pullulan (a polysaccharide composed of maltotriose with average M.W. 10 5) did not show any promoting effect, suggesting that only low molecular weight sugars can be incorporated through the epidermal pathway and contribute to clam growth. Soaking of adult clams in water supplemented with glucose at 100 mg l − 1 for 24 h resulted in 1.5 times higher quantity of total organic acids in the soft tissues compared with clams soaked in water without glucose, suggesting that the absorbed glucose is easily transformed into organic acids through the glycolysis pathway and makes an energetic contribution to clam growth. Here, we suggest a novel clam rearing method with “sugar supplements”, which can be used to promote clam growth through epidermal uptake.

The Evolution of Unpalatability and Warning Coloration in Soft-Bodied Marine Invertebrates

The Evolution of Unpalatability and Warning Coloration in Soft-Bodied Marine Invertebrates

Adaptations by Invertebrate Larvae for Nutrient Acquisition from Seawater

Unlike life on land, animals that live in seawater are surrounded by a medium that contains organic nutrients in dilute solution. Larval forms of soft-bodied marine invertebrates are adapted to take advantage of the fact that most of the organic carbon in their environment is in solution as dissolved organic material (DOM). New evidence for the importance of DOM to metazoans is presented by showing that larval forms can increase in biomass, even in the absence of paniculate foods. Such increases occurred only in those species capable of transporting DOM. The physiological basis for using DOM as an energy source is dependent upon an increased transport capacity for DOM as growth proceeds. Using bivalve larvae, mass coefficients and exponents were determined for (i) alanine transport rates and (ii) metabolic rates. These coefficients were not statistically different when determined over the life span of a larva. Thus, as growth proceeds, these larvae increase their ability to obtain a potential supply of metabolic fuel (DOM) in direct proportion to the increase in their metabolic demand. The percent of this increased transport capacity that larvae could actually utilize in nature will depend upon the substrate concentrations in their environment. Current views on what these concentrations are in seawater may be altered as more attention is given to the fine scale distributions of organic chemicals in the ocean. After DOM has been transported by the animal, its metabolic fate can now be rigorously studied using bacteria-free larvae. Measurements of amino acid synthesis in larvae cultured under axenic conditions suggest that a much greater plasticity may exist in the biochemical requirements of larvae for dietary amino acids.

Integumental nutrient uptake by aquatic organisms.

Integumental nutrient transport is a widespread characteristic of soft-bodied marine invertebrates. These processes, which are qualitatively similar to the Na-dependent transporters of intestinal epithelia, have kinetic and energetic characteristics that make them particularly well suited for accumulating materials from the extremely low substrate concentrations found in seawater. Despite the low concentrations of DOM in natural waters, rates of DOM uptake are large and clearly capable of supporting a significant fraction of the metabolic needs of some species. Indeed, recent studies with larval invertebrates suggest that integumental uptake of DOM may play a pivotal role in animal nutrition. Current and future studies on the mechanism and regulation of these processes, on the metabolic fate of accumulated DOM, and on the distribution of DOM in natural waters, promise to resolve the remaining issues on the role of integumental transport in the nutrition of aquatic organisms.

A Phylogenetic Analysis of Higher Taxa in the Phylum Sipuncula

-Twelve taxonomic characters of the genera in the phylum of marine worms, Sipuncula, are examined and polarities assigned to the various states. A Hypothetical Ancestral Sipunculan is proposed and probable evolutionary pathways are presented. The PHYLIP Camin-Sokal and the PAUP Wagner parsimony programs are used, as well as Dice's similarity coefficient and UPGMA cluster analysis. These provided both cladistic and a hybrid phenetic/ cladistic analyses. Only 5 of the 12 characters are clearly not homoplastic. While monophyly is not demonstrated in all cases, the 17 genera are now grouped into six families, four orders, and two classes as a result of using evolutionary, phenetic, and phylogenetic methodologies. The selective removal of homoplastic characters within the two classes did not significantly alter the composition of the orders or families. The evident congruence among these methods affirms the value of a synthetic approach. [Sipuncula; higher taxa; evolution; phylogenetic; similarity coefficient; cluster analysis.] Systematically, the marine worms comprising the phylum Sipuncula (peanut worms) have had a comnplex history. They have been ranked as a family, order, or class, and have been allied in various combinations with priapulids, echiurans, or annelids. In reviewing the history of sipunculan classification, Hyman (1959) regarded the group as being worthy of separate phylum rank, an idea first forwarded by Sedgwick (1898). The currently accepted spelling of the phylum was proposed by Stephen (1964). As a result of its confused classification, intermediate taxa (orders and classes) have not been developed for Sipuncula. Pickford (1947) suggested the genera should be arranged into four groups, while Akesson (1958) recommended an arrangement of the genera into three groups based on different characters than those used by Pickford. However, neither author forwarded taxon names or ranks for these groupings, and the void was only partially filled when Stephen and Edmonds (1972) erected the four families that are widely used to date. These families were employed by Murina (1975) in her consideration of the evolutionary relationships between sipunculan genera. This present work is an attempt to apply some of the extant phylogenetic methodology and logic to a phylum of poorlyknown, soft-bodied marine invertebrates for which there is no fossil record, an inadequate outgroup comparison on which to root character polarities, and only a modest number of useful characters. This proposed phylogeny is a testable model and can be improved as additional information becomes available. We herein interpret the evolutionary significance of the various taxonomically useful characters in the context of erecting new families, orders, and classes. The ideas outlined below were proposed in a preliminary fashion by Cutler (1980). Since that time efforts have been made to more adequately characterize certain genera and subgenera, such as: Siphonosoma (Cutler and Cutler, 1982); Antillesoma (Cutler and Cutler, 1983); Golfingia (Golfingiella) and (Siphonoides) (Cutler et al., 1983); Thysanocardia (Gibbs et al., 1983); Sipunculus and Xenosiphon (Cutler and Cutler, 1985); and Phascolion and Onchnesoma (Cutler and Cutler, unpubl. manuscript). Consideration of morphological characters useful at the generic level, their plesiomorphic /apomorphic states, and the

Evolution, Predator Avoidance, and Unsuccessful Predation

Commentaires sur les criteres de Vermeij (Ibid., 1982, 120, 701-720) pour l'identification des adaptations liees a la viabilite et, en particulier, aux defenses contre les predateurs

Recent Progress in the Study of “Die Ernährung der Wassertiere und der Stoffhaushalt der Gewässer”

SYNOPSIS. It is now possible to provide direct evidence for net removal of significant amounts of specific amino acids from naturally occurring dissolved organic material by a marine invertebrate. This demonstration serves to focus attention and invite reconsideration of the large body of less direct evidence supporting the general occurrence of this capacity among soft-bodied marine invertebrates.

Bacterial—Invertebrate Interactions in Uptake of Dissolved Organic Matter

SYNOPSIS. AS compared to integumentary uptake systems of soft-bodied marine invertebrates, bacterial systems, in terms of transport constants, are much better adapted to the low concentrations of dissolved organic nutrients encountered in coastal and offshore waters. Bacteria respond to the presence of suitable dissolved organic substrates with induction, uptake and multiplication, maintaining the concentrations of dissolved organic matter (DOM) permanently low. At realistic in situ concentrations, epidermal uptake by pelagic and epibenthic animals proceeds at such low rates that scarcely a substantial proportion of their metabolic needs is provided by absorption. In marine sediments, where the life processes of bacteria and animals are closely interrelated, the macrofauna is sheltered by shells, firm tubes and burrows, which are irrigated by means of overlying water of the water column. Hence, interstitial water with its sometimes higher concentrations of DOM is scarcely available to sediment-dwelling larger metazoans. The meiofauna mainly inhabits the few millimeters of the upper sediment layers and the thin halos surrounding irrigated macrofaunal burrows, where sufficient oxygen is available. Unless the magnitude of horizontal water movement, the amounts of diffusional nutrient supply and the percentages, by which nutrient concentrations are reduced by meiofaunal uptake, are known, estimations of nutritional benefits from uptake of DOM by meiofauna cannot be made. For all infaunal taxa, bacteria appear to represent a major food supply.

A COMPARATIVE STUDY OF THE NET METABOLIC BENEFITS DERIVED FROM THE UPTAKE AND RELEASE OF FREE AMINO ACIDS BY MARINE INVERTEBRATES

A comparative study was undertaken to evaluate the overall significance of free amino acid (FAA) uptake and release in the biology of 21 species of marine invertebrates, representing 7 phyla. Measurements of transport fluxes were made in defined media using the fluorescamine method, corrected for ammonia excretion, and related to measured metabolic rates and natural environmental levels. Except for arthropods, in which net uptake was negligible, all the animals exhibited influx of FAA at rates dependent on media levels, and low, constant efflux. Equilibrium concentrations were always found to be less than the mean minimum bay water concentrations. Thus, all must derive benefit to commonly support at least 3-10% of their metabolism—approximately sufficient to provide for the needs of epidermal and associated tissues, including ciliary pumping over gills, tube feet activity, etc. Certain forms, including a sand dollar and brittlestar, appear to have become particularly adapted to make use of this resource, which may provide them more sustenance than ingested food. Yet other species support lesser, but still substantial, proportions of their metabolic requirements through these mechanisms. It is concluded that net uptake of FAA is an essentially universal property of soft-bodied marine invertebrates, and it plays an important part in their well-being, especially by providing for much of the energy needs of superficial structures and aiding in metabolite retention.

Heavy metal action on transintegumentary absorption of glycine in two annelid species

Absorption of 14C-glycine from ambient sea water across the body surface of the oligochaete Enchytraeus albidus Henle was, after 6 h preincubation, significantly reduced in the presence of 0.1 to 0.15 ppm mercury, 0.25 ppm copper, 1.5 ppm silver, and 2 ppm cadmium. Addition of heavy metal salts reduced maximum uptake rates (Vmax), without affecting transport constants (Kt). Influx of 14C-glycine remained unchanged in the presence of up to 10 ppm aluminium, chromium, iron, lead, molybdenum, vanadium, and zinc. Effects of up to 150 ppm nickel, manganese, cobalt and selenium were negligible. Inhibition of glycine absorption by mercury and cadmium in the polychaete Nereis diversicolor Muller is almost identical with results presented for E. albidus. Transintegumentary solute absorption in soft-bodied marine invertebrates obviously represents a suitable biological function for studies on heavy metal toxicity. The close relationship between rates of heavy metal absorption, inhibition of transintegumentary glycine uptake, and acute toxicity is discussed.

III. Uptake in relation to organic content of the Habitat

Abstract Experimental evidence shows that many soft-bodied marine invertebrates accumulate amino acids, glucose, and fatty acids from dilute solutions by direct uptake through the epidermis. Comparison with what is known of the occurrence of these compounds in marine deposits suggests that some bottom-living animals could take up enough to meet all their metabolic needs as calculated from oxygen consumption. The species with significant rates of uptake include some polychaet worms and small unitentaculate pogonophores. Pogonophores seem capable of obtaining useful quantities of amino acids and glucose from concentrations less than 10-5 Moles/l; for the same uptake polychaets require concentrations of the order of 10-5 to 10-4 Moles/l, whereas tapeworms living in the rich environment of the digestive tract of vertebrates function best at levels around 10-3 Moles/l. These concentrations may possibly indicate the levels of dissolved substances in the normal habitat, and illustrate the degree of adaptation of...

Uptake of organic material by aquatic invertebrates. VI. Role of epiflora in apparent uptake of glycine by marine crustaceans

Soft-bodied marine invertebrates from most invertebrate phyla are capable of taking up amino acids from seawater. Marine crustaceans were originally reported not to accumulate amino acids. Artemia salina, Limnoria tripunctata, Tigriopus californicus, and Corophium acherusicum were examined for their ability to accumulate C14-labelled glycine from dilute solution in seawater. In initial experiments with Artemia and Limnoria the organisms were found to become very radioactive. When animals were preincubated in streptomycin or in a mixture of antibiotics, uptake of the C14-glycine was drastically reduced. Microorganisms associated with the arthropods and in the culture media were found capable of accumulating C14-labelled glycine. Efforts to demonstrate removal of amino acids from seawater by colorimeteric determination of material remaining in the medium were unsuccessful. The microorganisms responsible for the uptake are apparently associated with the exoskeleton of the organisms and not the gut. There is probably no substantial contribution to the nutrition of these crustaceans by the epiflora. Preincubation in the antibiotic mixture depressed the uptake of C14-glucose and C14-acetate by about an order of magnitude. It is concluded that there is no evidence for accumulation or assimilation of small organic compounds by the small crustaceans examined.