Partitioning and utilization of energy during the larval development of the xanthid crab, Rhithropanopeus harrisii (Gould)

An energy budget is constructed for the larval development of the crab Rhithropanopeus harrisii (Gould) fed nauplii of the brine shrimp Artemia salina (L.). Between the first zoeal instar and the megalopa, there is a 5.4-fold increase in caloric consumption and a 13.2-fold increase in dry weight. Weight specific energy content increases through the zoeal stages and drops at the megalopa. Rate of oxygen consumption increases steadily throughout development. Assimilation, gross growth, and net growth efficiencies increase steadily through zoeal development and drop at the megalopa. Calories put into tissue production exceed those expended via respiration in zoeal stages II–IV; the reverse is true in zoeal stage I and the megalopa.

A total energy budget has been calculated and the partitioning of energy is discussed in relation to other physiological studies on this species.     

Depth regulation of crab larvae in the absence of light

Behavioral responses to gravity and hydrostatic pressure have been investigated in two species of xanthid crabs Leptodius floridanus (Gibbes) and Panopeus herbstii Milne-Edwards to determine whether such responses provide a mechanism for depth regulation in the absence of light.In laboratory experiments, the four zoea stages and one megalopa stage of each species assume a differential vertical distribution in darkness, with succeeding stages showing a deeper overall distribution. Passive sinking rates increase in succeeding zoea stages and drop to an intermediate level after the molt to the megalopa stage. All zoea stages exhibit a negative geotaxis in the absence of light; the megalopa shows a positive geotaxis. The first zoea stage of Leptodius floridanus responds to an increase in hydrostatic pressure (up to 1 atmos above ambient) with an increase in swimming rate. This pressure response is shown to be reversible and not subject to short-term acclimation. The swimming rate of the last zoea stage does not increase in response to an increase in pressure.It is concluded that the responses of these larvae to gravity and hydrostatic pressure together with their characteristic passive sinking rates provide a mechanism for depth regulation in the absence of light that varies during ontogeny.     

The significance of diet in the growth and development of larvae of the blue crab,Callinectes sapidus rathbun,under laboratory conditions

The following protistan diets were tested on blue crab larvae: the algae Isochrisis galbana Parke, Monochrisis lutheri Droop, Dunaliella sp., and an unknown mixture; and the ciliated protozoans Euplotes vannus Muller and Parauronema virginianum(2/1) Thompson. None of these diets resulted in development past the first zoea stage, although some apparently were ingested and delayed mortality as compared to unfed controls.The rotifer Brachionus plicatilis Müller sustained good survival through early zoea development; however, rotifer-fed larvae did not metamorphose to the megalopa. Larvae of the polychaete Hydroides dianthus (Verrill) sustained crab larvae throughout zoea development, resulting in 17% survival to metamorphosis. The percentage mortality per stage was significantly lower in polychaete-fed larvae when compared with rotifer-fed larvae during zoea stages III, VI, and VII. Mean intermolt duration varied between diet treatments during the first three stages, but showed no differences during later zoea development. In tests on groups of late stage sibling larvae, Artemia salina L. nauplii gave development to metamorphosis, whereas rotifers did not.All the diets so far tested on blue crab larvae are classified according to their ability to sustain development. It is demonstrated that the two diets which allow completed development, Hydroides dianthus larvae and Artemia salina nauplii, contain 2–3 times as much lipid per dry weight as do rotifers. A metabolic requirement for lipid late in development may be indicated. Invertebrate larvae derived from yolky telolecithal and centrolecithal eggs may be an important dietary component for brachyuran larvae.     

HISTOCHEMICAL STUDIES ON MUCOPROTEINS IN NERVE CELLS OF THE DOG

Autonomic and sensory ganglion cells in the senile dog contain a deposition of PAS-positive substances which has been shown to be mucoprotein in nature. Data are presented to show that this PAS-positive mucoprotein can be demonstrated by metachromatic staining with toluidine blue after the mucoprotein is sulfated. This procedure indicates that mucoprotein is also present in a granular form in all nerve cells in both senile and young dogs. The evidence for this is further substantiated by the use of the aldehyde-fuchsin stain following both periodic acid oxidation and sulfation. The granular and non-granular deposition can be demonstrated by the periodic acid-aldehyde-fuchsin method due to the affinity of the aldehyde-fuchsin stain for aldehydes. It can be demonstrated following the sulfation-aldehyde-fuchsin method owing to the affinity of the stain for the sulfuric group. The evidence for this latter phenomenon has been reported by Scott and Clayton (6). It is concluded that mucoprotein is present in a granular form in all nerve cells in both senile and young dogs but is not concentrated enough in the latter to be demonstrated by the PAS method.     

CD36 Protein Influences Myocardial Ca2+ Homeostasis and Phospholipid Metabolism: CONDUCTION ANOMALIES IN CD36-DEFICIENT MICE DURING FASTING*

Sarcolemmal CD36 facilitates myocardial fatty acid (FA) uptake, which is markedly reduced in CD36-deficient rodents and humans. CD36 also mediates signal transduction events involving a number of cellular pathways. In taste cells and macrophages, CD36 signaling was recently shown to regulate store-responsive Ca²⁺ flux and activation of Ca²⁺-dependent phospholipases A₂ that cycle polyunsaturated FA into phospholipids. It is unknown whether CD36 deficiency influences myocardial Ca²⁺ handling and phospholipid metabolism, which could compromise the heart, typically during stresses. Myocardial function was examined in fed or fasted (18–22 h) CD36^−/− and WT mice. Echocardiography and telemetry identified conduction anomalies that were associated with the incidence of sudden death in fasted CD36^−/− mice. No anomalies or death occurred in WT mice during fasting. Optical imaging of perfused hearts from fasted CD36^−/− mice documented prolongation of Ca²⁺ transients. Consistent with this, knockdown of CD36 in cardiomyocytes delayed clearance of cytosolic Ca²⁺. Hearts of CD36^−/− mice (fed or fasted) had 3-fold higher SERCA2a and 40% lower phospholamban levels. Phospholamban phosphorylation by protein kinase A (PKA) was enhanced after fasting reflecting increased PKA activity and cAMP levels in CD36^−/− hearts. Abnormal Ca²⁺ homeostasis in the CD36^−/− myocardium associated with increased lysophospholipid content and a higher proportion of 22:6 FA in phospholipids suggests altered phospholipase A₂ activity and changes in membrane dynamics. The data support the role of CD36 in coordinating Ca²⁺ homeostasis and lipid metabolism and the importance of this role during myocardial adaptation to fasting. Potential relevance of the findings to CD36-deficient humans would need to be determined.     

Nutritional requirements during larval development of the portunid crab,Callinectes sapidus Rathbun

Three kinds of diet were used to identify the critical periods of nutritional vulnerability during larval development of the portunid crab, Callinectes sapidus Rathbun. A diet consisting solely of the rotifer Brachionus plicatilis Müller is not sufficient for complete developmetn. Development to metamorphosis can occur if rotifers are replaced by Day 15 with Artemia salina L. nauplii, but a diet of A. salina between Days 15 and 21 is also not sufficient for complete development. Delay in giving a brine shrimp diet beyond Day 15 causes a reduction in survival to the megalopa with an apparent threshold between Days 22 and 29, delay in molting in late instars, and increased frequency of supernumeracy larvae, many of which molt subsequently to the megalopa. Development to the megalopa on the rotifer diet is possible if crab larvae are initially fed a favorable control diet for as little as 14 days after hatching. Extension of time on the control increases survival to the megalopa slightly, has little effect on molt frequency, but reduces the number of zoeal instars.These data are interpreted in the context of identification of the unknown dietary requirement and for its implication to evolution of reproduction in the Brachyura.     

Inheritance patterns of enzymes and serum proteins of mallard-black duck hybrids

From 1974 to 1976, a breeding program was used to produce hybrids of black ducks and mallards for the evaluation of inheritance patterns of serum proteins and serum, liver and muscle enzymes. In addition to the crosses designed to produce hybrids, a series of matings in 1975 and 1976 were designed to evaluate inheritance patterns of a hybrid with either a black duck or mallard. At the F₁ level, hybrids were easily distinguished using serum proteins. However, once a hybrid was crossed back to either a mallard or black duck, only 12–23% of the progeny were distinguishable from black ducks or mallards using serum proteins and 23–39% using esterases. Muscle, serum and liver enzymes were similar between the two species.     

Frequency of mallard-black duck hybrids along the atlantic coast determined by electrophoresis and plumage analysis

The frequency of mallard and black duck hybrids along the Atlantic flyway was estimated based on serum protein and serum esterase electrophoresis and plumage analysis. Hybrid frequencies for black ducks were low (below 10%) in Nova Scotia - Maine, Ontario and New Jersey and high (above 10%) in Maryland and Massachusetts. Plumage estimates tended to be higher for black ducks in Massachusetts and Maryland than estimates based on the electrophoretic work.     

Feeding on dinoflagellates by intermediate and late stage crab zoeae raised in the laboratory and collected from the field

Hatching stage crab larvae will ingest algae, including non-toxic and toxic dinoflagellates. We determined that later zoeal stages, obtained from both laboratory-raised larvae and natural assemblages, also ingest dinoflagellates and we measured the effects of prey density, prior feeding history and time of exposure to prey on incidence of ingestion. Both stage 1 and later stage larvae exposed to algal prey were examined using epifluorescence for the presence of chl a. Both stage 1 and stage 3 laboratory-raised Cancer oregonensis (Dana) and Hemigrapsus nudus (Dana) ingested both the non-toxic dinoflagellate Prorocentrum micans Ehrenberg and the toxic Alexandrium andersoni Balech, with no difference between the stages. Both species showed higher ingestion of P. micans than A. andersoni. Ingestion of both prey types occurred at prey densities as low as 200 cell ml^− 1 in C. oregonensis and 50 cells ml^− 1 in H. nudus. Samples collected in summer, 2004, provided both stage 1 and late stage Lophopanopeus bellus (Stimpson); stage 1, intermediate, and late stage Fabia subquadrata Dana; and an unidentified porcellanid. Stage 1 L. bellus ingested both prey, while late stage zoeae did not, although the latter apparently were not actively feeding. F. subquadrata fed on both prey, with no difference between early and late larvae. Both stages ingested P. micans more readily than A. andersoni. First evidence of ingestion of P. micans at 600 cells ml^− 1 occurred after only 0.5 h, while it took 2 h for ingestion at 50 cells ml^− 1. The model of larval feeding involving both omnivory and prey discrimination described previously for the hatching stage is sustained throughout zoeal development and is, perhaps, an adaptation to an uncertain prey environment, one that trades opportunism for inefficiency.