Showing papers in "The Biological Bulletin in 1990"

A Decapod Hemocyte Classification Scheme Integrating Morphology, Cytochemistry, and Function

Abstract: We have examined the hemocytes of three decapod crustaceans (Homarus americanus, Panulirus interruptus, and Loxorhynchus grandis) and propose a classification of these cells based on morphology, cytochemistry, and studies of cell functions. In all species, hyaline cells and granulocytes were identified. Although we have retained the widely used names for these cells, we show that traditional morphological features alone do not accurately differentiate between these categories. Historically, the term hyaline cell refers to hemocytes that contain no or only a few cytoplasmic granules, whereas granulocytes contain abundant granules. However, the size and number of granules in hyaline cells vary greatly between species and therefore are not useful criteria for identifying these cells. Since morphological identification alone is inadequate and misleading, especially with regard to hyaline cells, a combination of morphological, cytochemical and functional methods is necessary to identify decapod hemocytes. Features of hyaline cells include: a higher nucleocytoplasmic ratio than that of granulocytes, the presence of abundant small ({approx}50 nm), round, electron-dense deposits in the cytoplasm, and their accumulation of trypan blue dye prior to cytolysis. Granulocytes do not take up trypan blue or lyse during a 5-min incubation, and they contain prophenoloxidase and hydrolases. Hyaline cells are involved in the initiation of hemolymph coagulation whereas granulocytes are involved in defense against foreign material by phagocytosis and encapsulation. We propose that these criteria be applied to other crustacean species and expect that they will facilitate our understanding of the physiological roles of their hemocytes.

Ontogenetic Change in Digestive Enzyme Activity of Larval and Postlarval White Shrimp Penaeus setiferus (Crustacea, Decapoda, Penaeidae).

Abstract: Whole specimens of developmental stages of Penaeus setiferus (Linnaeus, 1767) were homogenized and assayed for activities of digestive enzymes. In all developmental stages, activities were present for trypsin, carboxypeptidase A and B, amylase, and non-specific esterase; none for pepsin or lipase were detected. Activities assayed with substrates for chymotrypsin and aminopeptidase are not apparently due to the presence of these enzymes in the gut. Peak activities for all enzymes occurred during late zoeal or early mysis larval stages; low activities occurred at metamorphosis. During postlarval development, amylase activity increased steadily (by a tenfold increase over five weeks), whereas most other enzyme activities were relatively constant until the fifth week of postlarval development. Although it alters enzyme activity, diet does not appear to be the primary effector of ontogenetic change in digestive enzyme activity. Instead, ontogenetic change in digestive enzyme activity may reflect either a devel...

Respiratory responses of the blue crab Callinectes sapidus to long-term hypoxia

Abstract: Blue crabs (Callinectes sapidus) were held in hypoxic (50-55 mm Hg) water for 7-25 days. Postbranchial blood PO2 fell by about 80% within 24 h and then remained unchanged. Postbranchial blood total CO2 increased within 24 h and remained elevated for the duration of the experiment. There was no change in postbranchial blood pH, osmolality, or Cl. Lactate, urate, and Ca+2 all raise the O2 affinity of blue crab hemocyanin; by 25 days, blood lactate and urate had risen slightly, but Ca+2 had increased dramatically. Hemocyanin concentration had also increased by 25 days. At both 7 and 25 days there was an intrinsic increase in hemocyanin-O2 affinity and a change in subunit composition. The highly adaptive homotropic change is believed to be due to an attendant shift in the proportions of two of the three variable monomeric hemocyanin subunits. Thus, both heterotropic and homotropic adaptations enhance blood oxygenation at the gill during long-term hypoxia.

Induction of Metamorphosis of Larvae of the Green Sea-Urchin, Strongylocentrotus-Droebachiensis,by Coralline Red Algae

Abstract: The coralline red algae, Lithothamnion glaciale, Phymatolithon laevigatum, P. rugulosum, and Corallina officinalis, induced >85% of laboratory-reared larvae of Strongylocentrotus droebachiensis to metamorphose. Larvae must contact live L. glaciale or its spores for metamorphosis to occur; the inducer is not sensed in the water column. However, aqueous extracts of L. glaciale can induce metamorphosis, suggesting that the inducing factor is chemical. Neither ashed nor boiled L. glaciale induces metamorphosis, indicating that the factor is heat-labile and that thigmotaxis, per se, is not important in the response. The amino-acid, γ-aminobutyric acid (GABA), which induces settlement of other marine invertebrate larvae, also induces significant rates of metamorphosis of S. droebachiensis at concentrations ≥ 10-4 M. A reduction (with antibiotics) in the number of live bacteria on the surface of L. glaciale does not affect the rate of metamorphosis of larvae.

The Morphology and Mechanics of Octopus Suckers.

Abstract: The functional morphology of the suckers of several benthic octopus species was studied using histology and cinematography. The suckers consist of a tightly packed three-dimensional array of musculature. Three major muscle orientations are found in the wall of the sucker: (1) radial muscles that traverse the wall; (2) circular muscles that are oriented circumferentially around the sucker, including a major and minor sphincter muscle; and (3) meridional muscles that are oriented perpendicular to the circular and radial muscles. The connective tissue of the sucker includes inner and outer fibrous connective tissue layers and an array of crossed connective tissue fibers embedded in the musculature of the sucker. Attachment is achieved by reducing the pressure inside the sucker cavity. We propose the following mechanism to explain this pressure reduction. Contraction of the radial muscles thins the wall and thus increases the enclosed volume of the sucker. If the sucker is sealed to the substratum, however, the cohesiveness of water resists this expansion. Thus, contractile activity of the radial muscles reduces the pressure of the enclosed water. The radial muscles are antagonized by the circular and meridional muscles so that the three-dimensional array of muscle functions as a muscular-hydrostat. The crossed connective tissue fibers of the sucker may store elastic energy, providing a mechanism for maintaining attachment over extended periods.

Host-Zooxanthella Interactions in Four Temperate Marine Invertebrate Symbioses: Assessment of Effect of Host Extracts on Symbionts.

Abstract: Photosynthesis and translocation of photosynthetic products from symbiotic zooxanthellae in four species of temperate-latitude invertebrates were investigated in vivo and in vitro. In vivo, zooxanthellae fixed 14C and translocated a substantial proportion of fixed products to host tissues. In vitro, the effect of host tissue extracts on isolated zooxanthellae varied. Extracts of the soft coral Capnella gaboensis, lysed zooxanthellae after a relatively short exposure. Those of the zoanthid Zoanthus robustus and the nudibranch Pteraeolidia ianthina had little effect on translocation of organic carbon from zooxanthellae. In contrast, host extract of the scleractinian coral Plesiastrea versipora stimulated the release of up to 42% of the total 14C fixed, and the magnitude of release was positively correlated with the protein concentration of the extract. Host extracts had no effect on photosynthetic rates in algal symbionts. The effect of P. versipora extract on isolated zooxanthellae was studied. This extrac...

The anatomy and morphology of the adult bacterial light organ of Euprymna scolopes Berry (Cephalopoda: Sepiolidae)

Abstract: The sepiolid squid, Euprymna scolopes, has a bilobed luminous organ in the center of the mantle cavity, associated with the ink sac. Luminous bacterial symbionts (Vibrio fischeri) are housed in narrow channels of host epithelial tissue. The channels of each lobe of the light organ empty into a ciliated duct, which is contiguous with the mantle cavity of the squid. Surrounding the symbiotic bacteria and their supportive host cells are host tissues recruited into the light organ system, including a muscle-derived lens and thick reflector that appear to permit the squid to control the quality of bacterial light emission.

Consequences of the Calcite Skeletons of Planktonic Echinoderm Larvae for Orientation, Swimming, and Shape

Abstract: How the echinoderm larval skeleton is used for support of larval arms, passive orientation, and swimming was examined by experimentally removing the skeletons of plutei and by comparing feeding larvae from four echinoderm classes. All four types of echinoderm larvae oriented with their anterior ends upward in still water, but removing the skeletons of both live and dead four-armed echinoplutei demonstrated that their skeletons enhanced passive vertical orientation with their anterior ends upward. In comparisons of dead four-armed echinoplutei with and without skeletons, the skeleton contributed more than half of the excess density and sinking speed. In comparisons of all four types of feeding echinoderm larvae, larvae with a greater volume of skeleton and a smaller volume of tissues and body cavity were densest. The calculated work necessary to prevent the plutei from sinking was much less than 1% of the total aerobic energy expenditure. Thus calcite skeletons are not essential for passive vertical orient...

Ontogenetic Changes in Enzyme Distribution and Midgut Function in Developmental Stages of Penaeus setiferus (Crustacea, Decapoda, Penaeidae).

Abstract: Ultrastructure and histochemical distribution of enzymes were examined in the midgut of larval and postlarval stages of Penaeus setiferus. Acid phosphatase and esterase activities were present in all gut tissues at all stages. Protease activity was present in the anterior and lateral midgut caeca, as well as in the anterior portion of the midgut trunk (MGT) of larvae and early postlarvae (PL1-PL4). Amylase activity could not be detected histochemically in larvae or early postlarvae, even though it was detected in assays of whole-animal homogenates. In later postlarvae, both protease and amylase activities were present in the hepatopancreas and anterior MGT, but were absent from the anterior midgut diverticulum. In larvae, alkaline phosphatase activity is present throughout the midgut, suggesting that absorption is widespread. In juveniles, activity is restricted to the hepatopancreas and regions of the MGT within the cephalothorax. The abdominal MGT (or "intestine") is no longer absorptive by the time the...

Circadian Rhythmicity of the Crustacean Hyperglycemic Hormone (CHH) in the Hemolymph of the Crayfish

Abstract: The crustacean hyperglycemic hormone (CHH) is involved in the regulation of endogenous blood glucose metabolism. In this paper we describe the daily rhythmicity in the blood glucose and the blood CHH content of the crayfish Orconectes limosus. Both blood CHH and blood glucose levels increase during the first hours after the beginning of darkness. The bioactivity of released CHH is far higher than that of CHH stored in the sinus gland. Moreover, the released hyperglycemic material shows an affinity for high molecular weight proteins in the hemolymph. Preliminary results suggest that subunits of hemocyanin may act as potential carrier-proteins for bioactive CHH.

Ammonia induces settlement behavior in oyster larvae

Abstract: Oyster larvae exposed to solutions of NH4Cl exhibit stereotypical settlement behavior similar to that which normally precedes cementation and metamorpho- sis. Un-ionized ammonia is the active chemical species. At pH = 8.0, the threshold concentration of NH4Cl (pH = 8.0) for newly competent larvae is 2.5 mM; maximum activity is at 7.9 mM, corresponding to calculated NH3 concentrations of 100 pA4 and 3 10 PUM, respectively. In- duction of settlement behavior is rapid, with >90% of larvae exposed to 310 pA4 NH3 responding within less than 5 min. After 15 to 30 min, larvae become habituated to NH3 and resume swimming so that the percent exhib- iting settlement behavior after 30 min is < 10%. Other weak bases, such as methylamine and trimethylamine, induce similar behavior suggesting that NH3 acts by in- creasing intracellular pH. Evidence that NH3 and L-3,4- dihyrodxyphenylalanine (L-DOPA) induce settlement behavior through different mechanisms is presented. Ammonia may be a natural environmental cue that promotes oyster settlement behavior and, ultimately, recruitment.

A Practical Guide to the Developmental Biology of Terrestrial-Breeding Frogs

Abstract: Many frogs lay their eggs in water; the development of these frogs is well-known. However, many frogs reproduce on land; their eggs are large and have an altered early development. As examples, Gastrotheca riobambae broods its embryos in a pouch on the mother's back, and Eleutherodactylus coqui exhibits direct development with no tadpole stage. We provide practical information on obtaining eggs and embryos from these terrestrial-breeding species and on analyzing their development. Our aim is to make these species more accessible to researchers who are interested in the developmental and evolutionary consequences of terrestrial development.

Laboratory Culture of the Aeolid Nudibranch Berghia verrucicornis (Mollusca, Opisthobranchia): Some Aspects of Its Development and Life History

Abstract: Adult Berghia verrucicornis individuals lay white, spiral egg masses containing zygotes. Egg masses are easily cultured in aerated, Millipore-filtered, seasoned aquarium water. Development proceeds quickly, with the bilobed velum apparent by the end of the second day, and the larval shell appearing at the beginning of the third day after oviposition. Hatching occurs 11 to 12 days after oviposition (23.9 +/- 1.3°C). If egg masses are incubated without aeration, poecilogonous development is observed; both larvae and juveniles hatch from the same undisturbed egg mass. The larvae metamorphose soon after hatching, losing the velum and larval shell. A habitat-specific inducer is not required for metamorphosis; but a factor associated with the sea anemone Aiptasia pallida appears to enhance a larva's tendency to metamorphose. Juveniles begin feeding on A. pallida three to four days after metamorphosis. Reproductive maturity is achieved as early as 47 days after oviposition. Because B. verrucicornis can be cultured, along with its prey A. pallida, at inland facilities, this nudibranch species may be a useful model for laboratory-oriented life history and neurobiological investigations.

Diffusion Limitation and Hyperoxic Enhancement of Oxygen Consumption in Zooxanthellate Sea Anemones, Zoanthids, and Corals.

Abstract: Depending on their size and morphology, anthozoan polyps and colonies may be diffusion-limited in their oxygen consumption, even under well-stirred, air-saturated conditions. This is indicated by an enhancement of oxygen consumption under steady-state hyperoxic conditions that simulate the levels of O2 produced photosynthetically by zooxanthellae in the hosts' tissues. Such hyperoxia in the tissues of zooxanthellate species negates the effect of the diffusive boundary layer, and increases the rate of oxygen consumption; thus, in many cases, the rate of respiration measured under normoxia in the dark may not be representative of the rate during the day when the zooxanthellae are photosynthesizing and when the supply of oxygen for respiration is in the tissues themselves, not from the environment. These results have implications in respirometric methodology and in calculating the rate of gross photosynthesis in energetic studies. The activity of cytochrome c oxidase is higher in aposymbiotic than in zooxanthellate specimens of the sea anemone Aiptasia pulchella, and this may indicate a compensation for the relative hypoxia in the tissues of the former, enhancing the delivery of oxygen to the mitochondria from the environment.

Morphologic and Genetic Verification That Monterey Botryllus and Woods Hole Botryllus are the Same Species

Abstract: To determine whether Monterey Botryllus and Woods Hole Botryllus are the same species, comparisons were made of their morphology, biology, and colony specificity. In addition, matings were carried out to ascertain whether fertile [Monterey x Woods Hole] F1 progeny could be obtained. The morphology and biology of Botryllus colonies from Monterey and from Woods Hole are very similar, and fertile F1 progeny were obtained from interpopulation crosses. Therefore, we conclude that Monterey and Woods Hole Botryllus belong to the same species. However, slight differences were observed in the allorecognition reactions (colony specificity) of these two populations. Although there are some inconsistencies among the descriptions of Botryllus schlosseri and further extensive studies of Botryllus taxonomy are needed, our data indicate that Botryllus from Monterey and from Woods Hole may be designated contingently as B. schlosseri.

Extracellular Hemoglobins of Hydrothermal Vent Annelids: Structural and Functional Characteristics in Three Alvinellid Species.

Abstract: The polychaete annelids Alvinella pompejana, Alvinella caudata, and Paralvinella grasslei are strictly associated with deep sea hydrothermal vents. Each species possesses an extracellular hemoglobin, Hb, which has been studied and compared to that of a common intertidal polychaete, the lugworm Arenicola marina. The four Hbs exhibit very similar quaternary structures and spectral properties, and only small differences appeared in the gross polypeptide compositions after reduction and sodium dodecyl sulfate denaturation of the native molecules. Conversely, by a comparison of the effects of pH (6.6-7.6) and temperature (10-40{deg}C) on their intrinsic O affinities, Bohr factors, cooperativities, and apparent heats of oxygenation, lugworm Hb can be differentiated from that of the alvinellids, and the Hb of A. pompejana from that of A. caudata. The known biology of the lugworm and a further analysis of the data suggest several hypotheses concerning the in vivo O2 transport function of the alvinellid Hbs, the i...

Determination of Alkaline Phosphatase Expression in Endodermal Cell Lineages of an Ascidian Embryo

Abstract: Ciona intestinalis embryos develop a strong histochemical localization of alkaline phosphatase activity in their known endodermal tissues. Such tissues arise solely from the four vegetal blastomeres at the 8-cell stage and six vegetal blastomeres at the 16-cell stage; these vegetal cells inherit an endodermal lineage cytoplasm. Pairs of blastomeres from the bilaterally symmetrical 8- and 16-cell stages were isolated and reared as partial embroys. Only those partial embryos derived from endoderm-containing lineages developed a histochemically localized alkaline phosphatase activity. From the results of such restricted developmental autonomy (self-differentiation), one can deduce that this enzymic expression of endodermal fate could be specified by events of cytoplasmic segregation that occur during the early cleavages. This conclusion offers additional support to the theory that specification of cell fate in ascidian embryos involves an early differential segregation of histodetermining egg cytoplasmic mat...

Adaptations to the Deep-Sea Oxygen Minimum Layer: Oxygen Binding by the Hemocyanin of the Bathypelagic Mysid, Gnathophausia ingens Dohrn

Abstract: The bathypelagic mysid, Gnathophausia in- gens Dohrn, lives aerobically at oxygen partial pressures as low as 6 torr in the oxygen minimum layer off south- ern California. This study is concerned with the O2 bind- ing properties of this mysid's hemocyanin and the func- tion of the pigment in O2 uptake at low PO,. The effect of temperature on in vivo hemolymph pH (ApH/AT = -0.018) was measured from 2.5 to 12.5"C. Hemocya- nin concentration was estimated to be 24 mg/l, corre- sponding to an O2 binding capacity of about 0.3 mmol 02/1. Freezing of hemolymph samples significantly de- creased the affinity and cooperativity of HcOz binding, necessitating the use of fresh hemolymph. The Hc02 affinity was high (PsO of 1.4 torr at 5.5"C, pH 7.87) allow- ing the loading of O2 even at 6 torr. The cooperativity of Hc02 binding was also high (n5,, = 3.5 at 5.5"C, pH 7.87); presumably allowing the pigment to function effectively as an O2 transporter within the small Po, difference be- tween the environment and the tissues. Temperature differences within the environmental range (2- 1 OOC) had no significant effect on the oxygen affinity (AH = -6.7 kJ/mol, pH 7.7) or on the cooperativity of O2 binding. A large Bohr shift (A log PSo/ApH = -0.80 to -0.8 1) was present at all temperatures. L-lactate produced moderate increases in HcOz affinity (A log P50/A log (lactate) = -0.13 at pH 7.9) and in cooperativity. Regional and ontogenetic comparisons suggest that regional and onto- genetic differences in HcO, affinity occur in this species. This mysid has a hemocyanin of unusually high O2 affinity and cooperativity of O2 binding for a crustacean living at low temperatures, and this appears to be an ad- aptation for oxygen loading and transport at the cold,

Promotion and Inhibition of Calcium Carbonate Crystallization In Vitro by Matrix Protein From Blue Crab Exoskeleton.

Abstract: Soluble organic matrix isolated from dorsal carapaces of the blue crab, Callinectes sapidus, inhibited CaCO3 crystallization when free in solution. Immobilized matrix complexes, prepared by crosslinking soluble matrix to decalcified crab carapace, promoted CaCO3 formation in that crystallization in the presence of the immobilized soluble matrix complexes began sooner than in solution controls. In the experimental treatments, deposition of crystals occured only within the complexes and not in the crystallization solutions. Chitin, a polymer of N-acetyl-D-glucosaminc, and chitosan, a deacetylated chitin, which are both insoluble products of the organic matrix of the crab carapace containing little to no matrix protein, did not promote CaCO3 crystallization. Complexes of immobilized polyanionic synthetic peptides on chitosan also promoted CaCO3 crystallization. Addition of a hydrophobic tail (Ala8) to the polyanionic peptide (Asp20) reduced the rate of promotion, possibly because the hydrophobic tail formed a diffusion barrier around crystal nuclei growth sites, suppressing interactions of nascent crystal nuclei with ions in the bulk solution.

Jelly Layer Formation in Penaeoidean Shrimp Eggs

Abstract: Etude histologique et chronologique de la formation de la couche gelatineuse des œufs de crevettes Penaeoidea par microscopies optique et electronique a transmission

Behavioral Responses of Crustacean Larvae to Rates of Temperature Change.

Abstract: The ontogeny of behavioral responses of larvae of the crabs Rhithropanopeus harrisii and Neopanope sayi to rates of change in temperature were analyzed using a video system. A temperature decrease evoked an ascent in both species. The threshold rates of decrease for Stages I and IV zoeae of R. harrisii, and Stage I zoeae of N. sayi, were 0.06, 0.1, and 0.09°C min-1, respectively. Stage IV zoeae of N. sayi were unresponsive to any rate of decrease. Larvae descended upon a temperature increase. For Stages I and IV zoeae of R. harrisii and Stage I of N. sayi the threshold rates of temperature increase were 0.07, 0.24, and 0.18°C min-1, respectively. Stage IV zoeae of N. sayi were again unresponsive. In general, there was an ontogenetic change in responsiveness as Stage IV zoeae of both species were less sensitive than Stage I zoeae. The average absolute amounts of temperature change needed to evoke a response was independent of the rate of change at rates above threshold and ranged from 0.29 to 0.49°C for both species. A consideration of larval sinking rates and ascent speeds, as well as normal environmental temperature gradients, shows that larvae of both species can respond to the rates and amounts of temperature change found in their environments. These responses constitute a negative feedback system that could be used to regulate depth relative to temperature.

Behavioral and Metabolic Responses to Emersion and Subsequent Reimmersion in the Freshwater Bivalve, Corbicula fluminea.

Abstract: When exposed to air, the freshwater bivalve, Corbicula fluminea, displayed valve movement behaviors, such as mantle edge exposure, wider gaping "ventilatory" response, and an escape or "burrowing" response. The proportion of the emersion period spent in these behaviors, relative to valve closure, increased with decreasing temperature. Emersion at 35°C inhibited valve movement behaviors, whereas emersion in a nitrogen atmosphere stimulated ventilatory activity. High rates of aerial oxygen uptake (Mo2) were associated with initial valve opening and ventilatory behaviors, and lower Mo2 occurred during bouts of mantle edge exposure. Heart rate was affected by temperature, but not by mantle edge exposure. Heart rate increased during burrowing and ventilatory behaviors suggesting a hydraulic function for hemolymph. Emersed C. fluminea had short bursts of heat production followed by longer periods of lower heat flux when measured by direct calorimetry. The mean heat production rate was 1.11 mW (g dry tissue)-1, ...

Associations between egg capsule morphology and predation among populations of the marine gastropod, Nucella emarginata

Abstract: Intraspecific variation in the morphology of egg capsules is ideal for assessing the costs and benefits of encapsulation, yet little is known about the extent of such variation among populations of a single species. In the present study, I compared capsule morphology among three populations of the intertidal gastropod, Nucella emarginata. Significant differences were found both in capsule wall thickness and capsule strength. Mean capsule wall thickness varied as much as 25% among populations, with the dry weight of capsular cases differing accordingly. Capsule strength, measured as resistance to puncturing and squeezing forces, also varied among populations, but did not directly reflect differences in capsule wall thickness. Despite extensive variation in capsule morphology within this species, the number and size of eggs contained within capsules of equal volume did not differ significantly among populations. I also compared the type of capsule-eating predators that were present at each site. Shore crabs, Hemigrapsus spp., were abundant at all three sites; however, the predatory isopods Idotea wosnesenskii were only present at sites containing relatively thick-walled capsules. Although Hemigrapsus and Idotea were able to chew through both thick- and thin-walled capsules, laboratory experiments revealed that Idotea preferentially opened thin-walled capsules. These results suggest that variation in capsule morphology among populations of N. emarginata may, at least in part, reflect selection for the protection of embryos against predation.

The Sequencing, Synthesis, and Biological Actions of an ANP-Like Peptide Isolated from the Brain of the Killifish Fundulus heteroclitus

Abstract: We have extracted, purified, and sequenced an ANP-like peptide from the killifish. The peptide was extracted from whole brains with acidic acetone, and the aqueous phase remaining after evaporation of the ace- tone was subjected directly to HPLC. A pure peak was obtained after three successive HPLC steps. A key part of our purification method was the deliberate oxidation of methionyl residues in the peptide between the second and third HPLC steps. The purified peptide was chemi- cally sequenced, and its molecular weight was deter- mined by fast atom bombardment mass spectrometry (FABms). The peptide is 22 amino acids long and has considerable sequence similarity to the known natri- uretic peptides, especially within the disulfide bonded "ring"; but unlike these known peptides it ends immedi- ately after the second half cystine. Though it lacks a C- terminal "tail," the killifish peptide is equipotent to rat ANP in our radioimmunoassay, which employs an anti- serum to the rat peptide. Furthermore, this brain peptide is equipotent to eel ANP in relaxing toadfish aortic rings, though both fish peptides are slightly less potent than rat ANP.

Functional Autonomy of Land and Sea Orientation Systems in Sea Turtle Hatchlings

Abstract: Sea turtle hatchlings emerge from underground nests on oceanic beaches and immediately confront two separate problems in orientation. First they must locate the ocean and crawl to it; then they must orient offshore while they swim out to sea in a migration lasting several days. Visual cues guide hatchlings from the nest to the sea (1, 2) but little is known about the cues used by turtles in the ocean. Nevertheless, the crawl across the beach has long been considered essential to swimming orientation because hatchlings released offshore without a crawl reportedly fail to orient seaward (3, 4). Here we report that hatchling leatherback (Dermochelys coriacea) and green (Chelonia mydas) sea turtles released offshore consistently swam toward approaching waves and oceanic swells. Wave tank experiments confirmed that swimming hatchlings oriented into waves. A crawl across the beach was not a prerequisite for wave orientation in either the field or lab, indicating that hatchling sea turtles possess two separate orientation systems, each based on different sensory cues and capable of functioning autonomously. The first guides hatchlings on land to the sea; the second, based on wave detection, functions during the ocean migration. In five field experiments with green turtles and five others with leatherbacks, we monitored the swimming orientation of hatchlings released at various distances offshore near Fort Pierce, Florida. A total of 45 green turtle and 48 leatherback hatchlings were tested. All experiments were conducted between July and September in 1988 and 1989. Hatchlings were obtained from nests deposited on beaches in the Fort Pierce area. Nests were checked daily

Ontogenetic Variation in Sponge Histocompatibility Responses

Abstract: Grafting of adult sponge fragments (Chalinula sp) led to isograft fusion and allograft nonfusion in both parabiotic and implant grafts We conclude that adult Chalinula sp individuals discriminate between self and nonself, and fuse only isogeneic fragments In the laboratory, however, larvae and early juveniles fuse Larvae used in the experiments were probably genetically different, even if they were asexually reproduced These results indicate that the capacity for fusion between allogeneic individuals disappears during ontogenesis in this sponge In some cases, multichimeras were formed when up to five larvae fused to yield a single sponge All 37 chimeras metamorphosed and survived during 17 days of observation Possible mechanisms for the formation of sponge chimeras during early development are discussed, as are the costs and benefits of chimera formation at juvenile versus adult stages We propose that, if fusion exists in the field, it occurs between kin larvae

Parasitism and the Movements of Intertidal Gastropod Individuals.

Abstract: Movements of marked individuals of Ilyanassa obsoleta (n = 500) were charted in an intertidal environment for about one week. At the end of observations, 260 marked individuals, which had been sighted 1017 times collectively, were recollected and examined for trematode infections. Six trematode species were found in 19 infection combinations including uninfected, singly, doubly, and triply infected snails. We know that most snails found high on beaches and on sandbars carry Gynaecotyla adunca infections. It has been hypothesized that this host behavior modification is a parasite adaptation to enhance cercarial transmission to a semi-terrestrial next host. Observations reported here support this hypothesis and reveal some of the complexity in the behavior imposed on I. obsoleta by G. adunca. Individuals that were uninfected or infected with other parasites demonstrated no unique movement patterns, but individuals infected with G. adunca made repeated excursions into the upper shore habitat. These excursion...

Structure and Function of a Special Tissue in the Female Genital Ducts of the Chinese Freshwater Crab Eriocheir sinensis.

Abstract: The histological anatomy of the genital ducts of adult females of Eriocheir sinensis was studied before and after copulation, and during and after egg-laying. A strongly basophilic valve-like tissue was discovered at the junction of the spermatheca and the oviduct. This tissue prevents communication between the spermatheca and the oviduct except during oviposition. At this time, it functions as a valve, allowing ripe eggs out of the oviduct and preventing sperm from entering the oviduct during and after egg-laying. These findings suggest that the actual site of gamete contact in E. sinensis is within the spermatheca, instead of in the lumen of the ovary or in the oviduct. The presence of the valve-like tissue assures that the ripe eggs collected from the ovary during egg-laying are unfertilized. This observation is of great importance for obtaining unfertilized ripe eggs in studies of artificial fertilization (in vitro) and hybridization. The valve-like tissue has not been described in other brachyurans, ...

The Limulus Blood Cell Secretes α2-Macroglobulin When Activated.

Abstract: Alpha2-macroglobulin, a protease-binding protein that is reactive with almost all endopeptidases, is present in high concentrations in the plasma of the horseshoe crab, Limulus. Alpha2-macroglobulin was demonstrated by its ability to protect the active site of trypsin from inactivation by the macromolecular active site inhibitor, soybean trypsin inhibitor, and by reaction with an antiserum prepared against purified Limulus α2-macroglobulin. The blood cells also contain α2-macroglobulin in a form that is released when washed cells are stimulated to undergo exocytosis by treatment with the ionophore, A23187. Alpha2-macroglobulin is detected in the materials released from the cells during degranulation both by activity in the soybean trypsin inhibitor-protection assay and by immunochemical staining of Western blots. The subunit molecular weight of the cell-associated form of α2-macroglobulin, 185 kDa, is identical to that of the plasma form. The amount of α2-macroglobulin contained within the cells of a given volume of blood is 0.5-2% of the quantity in solution in that volume of plasma. The distilled water lysates of N-ethylmaleimide-stabilized amebocytes used to detect endotoxin (e.g., Limulus amebocyte lysate or LAL) contain relatively large quantities of active α2-macroglobulin. These preparations are essentially free of the principal plasma protein, hemocyanin, indicating that the cells had been well washed prior to lysis.

Drag Coefficients of Swimming Animals: Effects of Using Different Reference Areas

Abstract: The drag coefficient (C,) is useful for com- paring the hydrodynamic drag among different swimming animals However, Co is calculated using an arbitrary ref- erence area for which there is no uniform convention; both total surface area ("wetted area") and maximum cross-sectional area ("frontal area") are widely used The choice of reference area can have a profound effect on calculations of drag coefficient To illustrate this problem, drag measurements from two isopod crustacean species were used to calculate CD based on both wetted and frontal areas Idotea wosnesenskii had a higher mean Cu based on wetted area (0084) than Idutea resecatu (0059), but a lower mean CD based on frontal area (095) compared to I resecata (122); both differences are statistically sig- nificant Given that there is no powerful hydrodynamic basis for choosing either reference area, and that conver- sions between wetted area CD and frontal area CD cannot accurately be made for complex shapes, I suggest reporting both wetted area and frontal area C,'s wherever practical