Iain J. McGaw

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The passage of a barium meal (15 % by mass) was followed through the digestive system of the blue crab Callinectes sapidus by flash-freezing crabs at set intervals, followed by radiography of specimens. Food moved from the oesophagus into the stomach region within 15 min. After 1-2 h, food was visible in the midgut, at 6 h it had reached the hindgut, and(More)
The osmoregulatory physiology of decapod crustaceans has received extensive attention. Within this field there is a growing body of literature on cardiovascular and respiratory responses to low salinity. Most species exhibit a tachycardia coupled with an increase in ventilation rate and oxygen uptake. However, these previous experiments were conducted on(More)
The relationship between the behavioral and physiological responses to hyposaline exposure was investigated in Cancer gracilis, the graceful crab. The status of C. gracilis as an osmoconformer was confirmed. Survival decreased with salinity: the LT(50) in 50% seawater (a practical salinity of 16, or 16 per thousand) was 31.5 +/- 22.7 h and in 25% seawater(More)
Gastric evacuation and gut contraction rates were followed in the graceful crab Cancer gracilis during exposure to low salinity. Crabs were fed a radio-opaque meal and then exposed to 100% seawater (SW), 80%SW or 60%SW; passage of digesta was followed using a fluoroscope. Exposure to low salinity increased the time for food passage through the gut system.(More)
The circulatory system of adult blue crabs, Callinectes sapidus, was mapped by either injecting barium sulfate into intact animals followed by radiography or by resin corrosion casts (Batsons Monomer). Seven arteries arise from the heart. The anterior aorta exits from the anterior dorsal surface of the heart and gives rise to the optic arteries; these(More)
Peptide neurohormones exist as functionally similar analogues in a wide variety of invertebrate and vertebrate phyla, and many have been implicated as cardiovascular regulators. In decapod crustaceans, these include the pentapeptide proctolin, crustacean cardioactive peptide (CCAP) and the FMRF amide-related peptides F1 and F2, all of which are found in the(More)
Recent studies focusing on the consequences of feeding for ion and water balance in freshwater fish have revealed the need for similar comparative studies in seawater fish. A detailed time course sampling of gastrointestinal (GI) tract contents following the ingestion of a single meal of a commercial diet revealed the assimilation of both water and dietary(More)
Reports focusing on the behavioral responses of crabs to exposure to low salinity have involved choice chamber experiments or quantification of changes in activity. In addition to describing changes in locomotor activity in four species of crabs of differing osmoregulatory ability, the present study describes six behaviors: increased movement of the(More)
  • Iain J McGaw
  • Microscopy and microanalysis : the official…
  • 2005
Historically, the decapod crustacean circulatory system has been classed as open. However, recent work on the blue crab, Callinectes sapidus, suggests the circulatory system may be more complex than previously described. Corrosion casting techniques were refined and used to map the circulatory system of a variety of crab species (order: Decapoda; family:(More)
Respiratory responses and gastric processing were examined during hyposaline exposure in two crab species of differing osmoregulatory ability. The efficient osmoregulator, Callinectes sapidus, displayed an immediate increase in oxygen uptake when exposed to low salinity in isolation. In contrast, the weak osmoregulator, Cancer magister, showed no change in(More)