PubMed Health⌕ Search

Biomedical subjects

R T Hanlon

Publications and source records attributed to R T Hanlon.

32 records · Page 2Linked to original sources
PubMed1990

Physiological color change in squid iridophores. II. Ultrastructural mechanisms in Lolliguncula brevis.

Evidence is presented that changes in the optical properties of active iridophores in the dermis of the squid Lolliguncula brevis are the result of changes in the ultrastructure of these cells. At least two mechanisms may be involved when active cells change from non-iridescent to iridescent or change iridescent color. One is the reversible change of labile, detergent-resistant proteinaceous material within the iridophore platelets, from a contracted gel state (non-iridescent) to an expanded fluid or sol state when the cells become iridescent. The other is a change in the thickness of the platelets, with platelets becoming significantly thinner as the optical properties of the iridophores change from non-iridescent to iridescent red, and progressively thinner still as the observed iridescent colors become those of shorter wavelengths. Optical change from Rayleigh scattering (non-iridescent) to structural reflection (iridescent) may be due to the viscosity change in the platelet material, with the variations in observed iridescent colors due to changes in the dimensions of the iridophore platelets.

Acetylcholine↗
PubMed1989

Strontium is required for statolith development and thus normal swimming behaviour of hatchling cephalopods.

When cephalopod eggs were incubated in artificial sea water it was found that they sometimes resulted in hatchlings with defects of the statocyst suprastructure, leading to the severe behavioural defect of uncontrolled swimming. Experiments in defined media (seven basic salts mixed in deionized water) with seven species of cephalopods demonstrated clearly that there is 100% normal development of the aragonite statoliths when strontium levels were 8 mg l-1. Conversely, statoliths did not develop when strontium was absent. In cuttlefish, the growth of the cuttlebone was also affected adversely when strontium was absent. In mariculture production tanks, supplementing commercial artificial sea water with strontium to normal levels of 8 mg l-1 almost eliminated the occurrence of abnormal hatchlings. Circumstantial evidence indicates that there is a critical window in development during which strontium is required for normal development. The role of strontium in biomineralization during embryogenesis is unknown, but it appears to be important in the Mollusca.

Animals↗
PubMed1989

Alternative diets for maintaining and rearing cephalopods in captivity.

The requirement of live marine prey for cephalopod mariculture has restricted its practicality for inland research laboratories, commercial enterprises and home aquarists. We evaluated acceptability and resultant growth on: (a) frozen marine shrimps, (b) live and frozen marine polychaete worms, (c) live and frozen marine crabs, (d) frozen marine fishes, (e) live adult brine shrimp, (f) live freshwater fish and (g) live freshwater crayfish. The diets were presented for periods of 2 to 11 weeks to octopuses, cuttlefishes or squids and in most trials the results were compared to animals fed control diets of live marine shrimps, crabs or fish. Overall, frozen marine shrimp proved to be the best alternative diet tested. Adult Octopus maya on frozen marine shrimp diets grew as well as those on control diets at 2.8% body weight per day (%/d) compared to 2.0%/d on live freshwater crayfish, 1.4%/d on live marine polychaete worms and 0.8%/d on live freshwater fish (Tilapia sp.). Juvenile Octopus maya and Octopus bimaculoides also grew comparably to controls when fed frozen marine shrimps; growth rates ranged from near 3.0%/d at 3 months of age to nearly 2.5%/d at 6 months of age. Thus, these alternatives are acceptable as the octopuses end their exponential growth phase at an age of 3 - 5 months. Attempts to rear O. maya hatchlings and juveniles (up to 1 month of age) on dead foods resulted in high mortality and slow or negative growth. No live or dead alternative diet has been found yet that will promote good growth and survival in hatchling octopuses. Hatchling F3 generation Sepia officinalis (the European cuttlefish) were reared for 6 weeks exclusively on adult brine shrimp (Artemia salina).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed1986

Chromatophore motoneurons in the brain of the squid, Lolliguncula brevis: an HRP study.

The location of the motoneuron somata controlling activity of the chromatophore muscles was studied in the squid Lolliguncula brevis. Retrograde transport of horseradish peroxidase from injection sites in the skin or in the mantle muscle established that the chromatophore motoneurons are situated in the subesophageal mass of the brain while at least some of the mantle muscle motoneurons are in the stellate ganglia. Motoneurons to chromatophores in the mantle have their somata in the posterior subesophageal mass, mainly in the chromatophore or fin lobes. Motoneurons to chromatophores in the head are located in the anterior pedal lobes and those to the chromatophores in the arms project mainly from the anterior chromatophore lobes. However, some neurons in the posterior chromatophore lobes project to the head or arm regions. A few cells in both the anterior and posterior chromatophore lobes project contralaterally. Somata in other lobes of the subesophageal mass are also labelled by injections in the skin or in the mantle muscle. Evidence presented here suggests that some of the neurons labelled outside the chromatophore lobes are chromatophore motoneurons.

Animals↗
PubMed1986

Localization and stimulation of chromatophore motoneurones in the brain of the squid, Lolliguncula brevis.

The relatively simple chromatophore system of the squid, Lolliguncula brevis, was studied with combined behavioural, morphological and electrophysiological methods in order to understand how the chromatophore patterns in the skin are organized at the level of the posterior chromatophore lobes (PCL). There are nine simple chromatic components of patterning in L. brevis. Retrograde transport of horseradish-peroxidase from chromatophores in the mantle skin established that the chromatophore motoneurones are located in the PCL. Focal threshold stimulation of the PCL in perfused, semi-intact preparations showed that the motor fields of individual chromatophore motoneurones are compact, including 2-60 chromatophores, generally of the same colour. Adjacent motoneurones in the lobe do not necessarily have adjacent motor fields in the skin.

Animals↗
PubMed1985

Evidence for L-glutamate as a transmitter substance of motoneurons innervating squid chromatophore muscles.

Motor nerve branches were stimulated in the dermis layer prepared from isolated pieces of dorsal mantle skin of the squid Lolliguncula brevis and the contractions of chromatophore muscle fibers were recorded with the aid of a photo-electric transducer. L-Glutamate (L-Glu), kainate and quisqualate caused a contracture and often repetitive twitch-like contractions. These effects were readily reversible. In the case of L-Glu application, twitches induced by single stimuli applied to motor nerves were enhanced and prolonged. The glutamate antagonists glutamic acid gamma-methyl ester, glutamic acid diethyl ester, D,L-2-amino-4-phosphonobutyrate and gamma-D-glutamylglycine prevented both nerve induced and L-Glu induced contractions. The NMDA-receptor agonists N-methyl-D-aspartate, L-aspartate and D-glutamate, and their antagonists alpha-aminoadipate and D,L-2-amino-5-phosphonovalerate were found ineffective. With the aid of saline media of different Ca and Mg content, it was possible to selectively eliminate one or all components of the effect of L-Glu. Tetrodotoxin abolished nerve induced contractile responses but did not interfere with the contracture caused by L-Glu. Intracellular electrical recording indicated that nerve stimulation causes EPSPs which do not give rise to spike discharges. The results are compatible with the hypothesis that L-Glu is a transmitter substance of the motoneurons that innervate chromatophore muscle fibers.

Animals↗
PubMed1985

Advances in the laboratory culture of octopuses for biomedical research.

Five species of Octopus were cultured in pilot, large-scale 2,600 liter circulating seawater systems. Improvements in system design, water management and culture methodology were described. These five species all produced large eggs and correspondingly large hatchlings that had no planktonic or larval stage and thus were easier to culture. Octopuses grew well only when fed live marine crustaceans, fishes and other molluscs. Growth occurred as a 4-7% increase in body weight per day during the early exponential growth phase and 2-4% during the latter 1/2 to 3/4 of the life cycle, which ranged from 6-15 months depending upon species. All species reproduced in captivity. Survival was 70-80% when octopuses were reared in individual containers, but in group culture survival dropped to as low as 40% by the adult stage. Causes of mortality were species-specific and included hatchling abnormalities, escapes, aggression, cannibalism, disease, senescence and laboratory accidents. Octopus bimaculoides showed superior qualities for laboratory culture. The future potential of providing American scientists with laboratory-cultured octopuses was discussed along with their uses in biomedical research.

Animals↗
PubMed1984

"Spinner" cephalopods: defects of statocyst suprastructures in an invertebrate analogue of the vestibular apparatus.

Individuals of seven species of coleoid cephalopods (three species of octopus, three of squid, and one of cuttlefish), that were cultured and reared in laboratory aquarium systems, had a behavioral defect at hatching which was characterized by an inability to control orientation while swimming. These defective animals were designated as "spinners." An examination of statocysts from individuals of five of the affected species revealed abnormalities of the neuro-epithelial suprastructures: absence or malformation of the statolith of the gravity receptor system and absence of the cupulae of the angular acceleration receptor systems. The sensory epithelia did not differ from those of normal animals, nor did the synaptic structures and relationships, when examined both with scanning and transmission electron microscopy. The abnormalities were compared with congenital defects of the neuropeithelial suprastructures of the vestibular apparatus (especially in mammals). The defects observed in statocysts of spinner animals are thought to be the result of environmental causes, such as the temperature or chemistry of the seawater in the transportation vessels or rearing systems, rather than genetic causes.

Animals↗
PubMed1980

A closed marine culture system for rearing Octopus joubini and other large-egged benthic octopods.

The system consists of 2 adjoining 150 litre aquaria, one functioning as the water-conditioning tank and the other as the principal rearing tank. Water quality remained high with biological and mechanical filtration, physical adsorption and ultraviolet-light disinfection taking place exclusively in the conditioning tank. The pH ranged from 7.58 to 8.00 and ammonia and nitrite levels never exceeded 0.004 mg/l and 0.198 mg/l, respectively. Nitrate levels were maintained at 40 mg/l or less with no adverse affects. Adult octopuses readily mated and females produced 50-150 eggs, with 95% hatching success. When fed small liver crabs, the octopus hatchlings were reared to sexual maturity either in groups or individually in about 120-150 days. Growth rates (4% bodyweight/day) and food conversion efficiences (30-40%) were as high as those obtained in open systems by previous workers.

Ammonia↗
PubMed1979

Fin damage in captured and reared squids.

Fin damage was a major factor in the mortality of wild-caught squids kept in the laboratory. Infection of abraded fins by opportunistic bacterial pathogens impaired swimming and led to death. Serious skin abrasions were especially common in trawl-caught squids. Dipnets and jigs inflicted minimal trauma and were preferred for squid capture. Fin damage also occurred during transportation and during maintenance of squids in onshore tanks. A successful aquarium system with recycled sea water was used for squid maintenance. Hatchling, juvenile and adult loliginid squids remained healthy in closed-system aquaria for periods ranging from 1 to 16 weeks.

Animals↗
PubMedDate not supplied

Toxic exposure to ethylene dibromide and mercuric chloride: effects on laboratory-reared octopuses.

The effects of acute and chronic exposure to either ethylene dibromide (EDB) or mercuric chloride (MC) were studied in laboratory-reared Octopus joubini, O. maya and O. bimaculoides. The advantages of using octopuses were that the responses were immediate, highly visible and sensitive. All species demonstrated signs of toxicity to acute and chronic exposure to EDB and to MC. A dosage-sensitive relationship for the loss and subsequent recovery of locomotor response and of chromatophore expansion was found for each species after acute exposure. For each species the LC50 for chronic exposure occurred within 12 hr at 100 mg/l for EDB and within 3 hr at 1,000 mg/l for MC. This study demonstrated the potential usefulness of laboratory-reared octopuses in evaluating the toxicity of marine environmental pollutants.

Animals↗