John D. Costlow

Settlement and behavior in relation to flow and surface in larval barnacles, Balanus amphitrite Darwin

Abstract Behavior and settlement of laboratory-reared larval barnacles were examined with respect to age of larvae, type of surface (polystyrene and glass), and treatment of surface with settlement factor. Young cyprids were more discriminating in settlement than old cyprids. Young cyprids settled more on glass than on polystyrene. Young cyprids settled in higher percent on either polystyrene or glass in the presence of settlement factor. Settlement factor had no detectable effect on settlement of older cyprids. A rapid (2 to 10 min) quantitative assay for study of larval barnacle responses to surfaces was developed. The assay can be used to investigate molecular modifiers of larval barnacle behavior. Surfaces treated by adsorption of settlement factor from a 2.5 μ/ml solution promoted reversible attachment by cyprids. Cyprids separated on the basis of their behavior were tested in settlement assays. In the absence of settlement factor, there were marked differences in percent settlement between classes. Addition of settlement factor to settlement assays did not affect settlement of certain behavior classes and increased settlement over six-fold in others.

Ion and neuropharmacological studies of barnacle settlement

Abstract Experiments tested effects of altering ion concentrations and the effects of additions of biologically active substances in the media surrounding settling stage barnacle larvae. Alteration of ionic concentrations did not result in induction of metamorphosis. Excess potassium ion, magnesium ion and calcium ion inhibited settlement. Potassium ion affected young cyprids while other cations had more pronounced effects on older cyprids. Replacement of one cation by another reduced the inhibitory effects of all but calcium. Excess magnesium was routinely inhibitory while lowered magnesium had little effect. Calcium ion could be increased 50% by lowering magnesium concentrations without affecting settlement. However, low calcium ion concentrations inhibited settlement. Of the biologically active substances tested, only soluble barnacle settlement factor and dibuteryl cAMP induced metamorphosis. SITS, a calcium channel blocker, inhibited settlement and negated the effects SF +. Most of the other compounds inhibited settlement at millimolar concentrations and had no effect when tested at lower concentrations. Picrotoxin, a compound that interferes with chloride ion movement (and membrane depolarization) strongly inhibited metamorphosis with an EC50 of 10−6 mol.

Inhibition of barnacle settlement and behavior by natural products from whip corals,Leptogorgia virgulata (Lamarck, 1815).

Laboratory-reared barnacle larvae were used to study natural products from whip corals. Biological assays used barnacle responses in behavioral assays and in larval settlement assays. Whip corals contained substances that were active in both assays. Substances inhibiting swimming and reversible attachment of barnacle larvae were found in an aqueous extract of whip corals. Low-molecular-weight substances inhibiting barnacle settlement were found in a methylene chloride extract of material soluble in aqueous methanol. Antisettlement activity was associated with substances with specific mobilities in several chromatography systems. Partially purified material was effective in preventing settlement at concentrations of less than 0.2 μ/ml. Settlement inhibition involves adsorption of the natural product to surfaces.

Free Cupric Ion Activity in Seawater: Effects on Metallothionein and Growth in Crab Larvae

Crab zoeae (Rhithropanopeus harrisii) were exposed during their development opment to a range of free cupric ion activities regulated in seawater by use of a copper chelate buffer system. Most cytosolic copper was found to be associated with metallothionein. Copper-thionein could be related to free cupric ion activity, and a shift in copper-thionein accumulation was correlated with inhibition of larval growth. These data reveal predictable relations between cupric ion activity in seawater and processes at the cellular and organismic levels.

EFFECTS OF EARLY STARVATION PERIODS ON ZOEAL DEVELOPMENT OF BRACHYURAN CRABS

Larvae of the crabs Menippe mercenaria Say (Menippidae), Panopeus herbstii Milne-Edwards, Neopanope sayi Smith (Xanthidae), Sesarma cinereum Bosc (Grapsidae), and Libinia emarginata Leach (Majidae) were reared in the laboratory. Starvation periods different in length and timing within the first zoeal stage were studied as to their effects on later development and survival rate. After 1-3 days of initial feeding, most larvae had accumlated enough reserves to reach the second stage, independently of further food availability. The development of the survivors was delayed in the following stages, and their later mortality rate was higher than the fed controls. Starvation periods commencing directly after hatching of the larvae exert far stronger negative effects than those beginning later. All observations suggest a particularly sensitive phase in the beginning of larval life in brachyurans. When initial starvation periods exceed the point-of-no-return (PNR), the larvae will die later, even if feeding begins ...

Inhibition and induction of barnacle settlement by natural products present in octocorals

Barnacle settlement inhibitors and inducers are present in the gorgonianLeptogorgia virgulata and the pennatulaceanRenilla reniformis. The inhibitors are low-molecular-weight compounds (<20,000 daltons) that were detected in soft tissue homogenates and dialysates of homogenate and in ambient “gorgonian water.” Settlement was almost completely inhibited at a dialysate concentration of 1.0 g wet weight equivalents/liter. The inhibitors probably function in chemical defense against predation and fouling, and could prove useful in ship fouling control. The settlement inducers are high-molecular-weight substances (>20,000 daltons) that adsorb to surfaces.

The effect of salinity and temperature on survival and metamorphosis of megalops of the blue crab Callinectes sapidus

1. Megalops of the blue crab,Callinectes sapidusRathbun, reared from hatching through all zoeal stages at 25° C, 30 p. p. m., were maintained in 23 combinations of salinity and temperature until metamorphosis to determine the effect of salinity and temperature and the combined effect of salinity and temperature on survival and rate of development.KurzfassungLarven der Blauen Krabbe (Callinectes sapidusRathbun) wurden bei 25° C und 30 ‰ S (= p. p. m.) gezüchtet, bis das Megalopalarvenstadium erreicht war. Die Megalopalarven wurden sodann in 6 verschiedenen Salzgehalten und 4 verschiedenen Temperaturen gehalten, um die Wirkung von Salzgehalt und Temperatur sowie von deren Kombinationen auf Überlebensrate, Entwicklung und Metamorphose festzustellen. Bei 20°, 25° und 30° C überlebten über 70 % der Megalopalarven in Medien von 10 bis 40 ‰ S. Bei 15° C betrug die Überlebensrate 10 bis 50 % in Salzgehalten von 20 bis 40 ‰. Die Megalopalarven metamorphosierten nicht bei 15° C und 10 ‰ sowie bei 20° C und 5 ‰. Die Dauer des Megalopastadiums schwankte von 5 Tagen bei 30° C bis zu 67 Tagen bei 15° C. Die Temperatur beeinflußte die Lebensdauer der Megalopalarven stärker als der Salzgehalt. Bei 20° und 30° C wurde die Dauer des Megalopastadiums durch veränderte Salinitätsbedingungen nicht beeinflußt. Bei 15° C bewirkte eine Erhöhung des Salzgehalts jedoch eine Verzögerung der Metamorphose des ersten Krabbenstadiums. Durch statistische Analysen sind die Wirkungen von Salzgehalt und Temperatur auf Sterblichkeit und Entwicklungsrate der Megalopalarven für eine größere Anzahl von Umweltsbedingungen, als sie im Laboratorium geprüft werden konnten, ermittelt worden, so daß die Überlebensrate der Megalopalarven innerhalb eines großen Temperatur- und Salzgehaltsbereiches mit großer Wahrscheinlichkeit vorausgesagt werden kann. Es ist anzunehmen, daß durch die zeitliche Verlängerung des Megalopastadiums und die hohe Überlebensrate in Gewässern mit niedriger Temperatur und hohem Salzgehalt ein Transport der Megalopalarven durch Meeresströmungen über weite Entfernungen ermöglicht wird. Diese Annahme würde unter anderem die Verbreitung dieser Gattung über einen großen Teil der Gewässer entlang der atlantischen Küste sowie im Golf von Mexiko erklären.Summary1. Megalops of the blue crab,Callinectes sapidusRathbun, reared from hatching through all zoeal stages at 25° C, 30 p. p. m., were maintained in 23 combinations of salinity and temperature until metamorphosis to determine the effect of salinity and temperature and the combined effect of salinity and temperature on survival and rate of development.2. Survival of the megalops stage was similar at temperatures of 20°, 25°, and 30° C with the exception of the larvae maintained at 5 and 10 p. p. m. At 15° C, survival never exceed 50 percent.3. In the lower salinities (5 and 10 p. p. m.) survival decreased with a decrease in temperature.4. The most pronounced effect of temperature in delaying the time of metamorphosis was observed in megalops maintained at 15° C. As the salinity increased from 20 to 40 p. p. m., the duration of the megalops stage was further extended at 150° C. This effect was not observed at other salinity-temperature combinations.5. Statistical analysis of factorical design was used to predict the mortality and duration of the megalops stage which might be expected under a greater number of salinity-temperature combinations than are feasible to observe in the laboratory. The results of the analysis and their possible significance are discussed.6. The hypothesis is presented that survival and duration of the megalops ofC. sapidus in the natural environment are directly associated with the time of hatching, the time at which the megalops stage is reached in relation to seasonal changes in water temperatures, and the salinity of the water in which the final zoeal molt occurs. The delay of metamorphosis in waters of high salinity and low temperature may have contributed to the distribution of this species in the estuaries along a major portion of the Atlantic and Gulf Coasts of the United States.

Anaerobic sampling of body fluids in bivalve molluscs

Abstract 1. A method is described for anaerobic sampling of pericardial fluid and haemolymph from live, intact bivalve molluscs, without taxodont dentition, with special reference to the clam Rangia cuneata. 2. No difference is found between pericardial fluid and haemolymph of R. cuneata with respect to osmolality, chloride concentration, protein concentration, concentration of ninhydrin positive substances, pH, and oxygen tension. 3. Hypoxia and acidosis in R. cuneata is not evident before 1–2 days of air exposure.

The molt cycle and its hormonal control in Rhithropanopeus harrisii larvae.

Abstract Stages of the zoeal and megalopal molt cycles of Rhithropanopeus harrisii were characterized by the appearance of epidermal cells in the spines and antennae. Eyestalk removal of the beginning of the last zoeal instar slightly accelerated the molt cycle. Fourth-instar larvae which had undergone eyestalk ablation during the third instar progressed through the molt cycle significantly faster than did control larvae. Eyestalkless megalopae also demonstrated an enhanced molting rate. The results suggested that the larval eyestalks contain a factor (molt-inhibiting hormone) which plays a role in controlling the molting rate.

The Effect of Salinity and Temperature on the Larval Development of the Stone Crab, Menippe mercenaria (Say), Reared in the Laboratory

The larvae of the stone crab,Menippe mercenaria (Say) have been reared in 18 different environments—comprising 6 levels of salinity (10, 20, 25, 30, 35 and 40‰) and 3 levels of temperature (20, 25 and 30 C). The results show that both salinity and temperature affect the rate of larval development as well as larval survival. The rate of development was slightly slower in a reduced salinity (20‰) than in high salinities (30–40‰), and very markedly retarded with decreasing temperature from 30 to 20 C. Total mortality was observed in the first zoeal stage in 10‰ at all temperatures. In other experimental salinities (20–40‰) at 20 C, the larvae only developed to the megalopa. Survival to the megalopa at 20 C was less in 20–25‰ than in 30–40‰ and also lower than that observed at 25 and 30 C. Survival to the first crab at 25 and 30C was considerably lower in 20‰ than in higher salinities. The optimum temperature for the larvae ofM. mercenaria would be approximately 30 C, and the optimum salinity in the range of 30–35‰. Under these conditions, the megalopa aas reached on the 14th day after hatching, and the first crab on the 21st day, with total survival in the range of 60–72%. From the relatively high survival and the short development period, it would appear that the stone crab might be a more suitable species than other commercially important crabs for any future large-scale rearing experiments.