MICHELE G. WHEATLY 1, WARREN W. BURGGREN 2, and BRIAN R. MCMAHON 1
1 Department of Biology, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, Canada T2N 1N4
2 Zoology Department, University of Massachusetts, Amherst, Massachusetts 01003
Temperature acclimation (18-30°C) and dehydration (to 86% of initial mass) are two problems frequently encountered by the land hermit crab, Coenobita clypeatus. Their individual and combined effects on hemolymph ion and acid-base status were assessed. With free access to 10% SW, crabs maintained a constant degree of hydration, with hemolymph marginally hypo-osmotic to full strength SW. Increased acclimation temperature produced a reduction in pH, characteristic of ectotherms and consistent with maintenance of relative alkalinity which was accomplished by an elevation of CO2 tension (P,CO2). Hyperactivity resulted in some spillage of shell water and affected Cl- balance. Under water deprivation, evaporative loss declined approximately exponentially and was negatively correlated with body mass. Hemolymph osmolality and electrolyte levels were significantly increased, ionic imbalance contributing largely to the hemolymph acidosis. Hemoconcentration was less marked when combined with temperature acclimation. Temperature-dependent pH regulation however in dehydrated crabs was accomplished as in hydrated crabs by ventilatory P,CO2 control typical of air-breathers. The aquatic route of acid-base regulation (by ionic exchange) potentially afforded by the reservoir of water held in the molluscan shell was apparently not utilized.
Monday, September 24, 2007
Reproductive Biology of Three Land Hermit Crabs (Decapoda: Anomura: Coenobitidae) in Okinawa, Japan
Abstract:
Reproductive ecological research on three land hermit crabs, Coenobita rugosus, C. purpureus, and C. cavipes, was conducted in the southern part of Okinawa-jima island in 1985, 1986, 1987, and for a short period in 1999. Size (carapace length) of the smallest ovigerous female was 3.93 mm for C. rugosus, 3.83 mm for C. purpureus, and 9.49 mm for C. cavipes. Breeding season is late May to November for C. rugosus, late May to mid-September for C. purpureus, and mid-May to late August for C. cavipes. Some females of all three species probably produced at least two broods during the breeding season. The smallest males in which spermatophores were present in dissected vas deferens were 4.24 mm for C. rugosus and 4.94 mm for C. purpureus. Coenobita cavipes females produced more, smaller eggs in comparison with C. purpureus. My observations suggest that coenobitid crabs living in areas with a low supply of shells or with poor shells reproduce at smaller sizes, as is the case in marine hermit crabs. Time of onset of larval release by C. rugosus, with its protracted breeding season, varied according to the seasonal shift in time of sunset. The period during which females of C. rugosus released larvae was about 2 hr in spring tides but was much longer (3 to 5 hr) during neap tides. Larger females of C. purpureus occupied shells derived from the land snail Achatina fulica; smaller ones used shells from the marine snail Lunella granulata. Use of mutually exclusive larval release sites by the larger and smaller females of C. purpureus remained unchanged over 13 yr, from 1986 to 1999. This behavioral difference may be related to the differences in their habitats (i.e., inland versus shore) and to the route traveled by the larger crabs in reaching the sea from inland sites.
Díaz-Uribe, J. Gabriel.
Elorduy-Garay, Juan F.
González-Valdovinos, Ma. Teresa.
Reproductive ecological research on three land hermit crabs, Coenobita rugosus, C. purpureus, and C. cavipes, was conducted in the southern part of Okinawa-jima island in 1985, 1986, 1987, and for a short period in 1999. Size (carapace length) of the smallest ovigerous female was 3.93 mm for C. rugosus, 3.83 mm for C. purpureus, and 9.49 mm for C. cavipes. Breeding season is late May to November for C. rugosus, late May to mid-September for C. purpureus, and mid-May to late August for C. cavipes. Some females of all three species probably produced at least two broods during the breeding season. The smallest males in which spermatophores were present in dissected vas deferens were 4.24 mm for C. rugosus and 4.94 mm for C. purpureus. Coenobita cavipes females produced more, smaller eggs in comparison with C. purpureus. My observations suggest that coenobitid crabs living in areas with a low supply of shells or with poor shells reproduce at smaller sizes, as is the case in marine hermit crabs. Time of onset of larval release by C. rugosus, with its protracted breeding season, varied according to the seasonal shift in time of sunset. The period during which females of C. rugosus released larvae was about 2 hr in spring tides but was much longer (3 to 5 hr) during neap tides. Larger females of C. purpureus occupied shells derived from the land snail Achatina fulica; smaller ones used shells from the marine snail Lunella granulata. Use of mutually exclusive larval release sites by the larger and smaller females of C. purpureus remained unchanged over 13 yr, from 1986 to 1999. This behavioral difference may be related to the differences in their habitats (i.e., inland versus shore) and to the route traveled by the larger crabs in reaching the sea from inland sites.
Díaz-Uribe, J. Gabriel.
Elorduy-Garay, Juan F.
González-Valdovinos, Ma. Teresa.
Respiration and Adaptation to the Terrestrial Habitat in the Land Hermit Crab Coenobita Clypeatus
BRIAN R. McMAHON 1 and WARREN W. BURGGREN 2
1 Department of Biology, University of Calgary, Calgary T2N 1N4, Alberta, Canada
2 Zoology Department, University of Massachusetts, Amherts Ma 01003, U.S.A.
The frequencies of heart (fH) and scaphognathite (ventilatory = fBC) pumping, and responses to hypoxia, hypercapnia and wetting (simulated rain), as well as oxygen consumption (MOO2), pre- and postbranchial haemolymph oxygen tension (POO2), oxygen content (COO2), carbon dioxide content (CCOCO2) and pH were measured in adult land crabs Coenobita clypeatus. There was a large increase in f8C in response to both hypoxia and wetting but a smaller increase in response to even severe hypercapnia. Some evidence suggests that ventilation via the scaphognathites may have been supplemented by a second (branchiostegal) pump when ventilatory requirement was high. fH was less responsive to either hypoxia or hypercapnia, but decreased with severe exposure to either. Haemolymph oxygen tensions were low (P{alpha},O{alpha},O2 = 14, PvOvO2 = 8) but haemocyanin oxygen affinity was high in vivo (P50 = 10 torr at 23°C) and postbranchial haemocyanin was 60-80% saturated. Oxygen content was also high allowing adequate oxygen release to the tissues despite the low oxygen tensions. {Delta}P50/{Delta}t = 0.37 torr/{Delta} °C, log {Delta}P50/{Delta}pH = - 0.84 torr/pH unit, both determined in vitro were lower than literature values for marine and littoral species. As in other terrestrial species, CCOCO2 and PCOCO2, (calculated) were high, as were both bicarbonate and non-bicarbonate buffering capacities. Water loss was less (0-08% body weight. h-1) in Coenobita than in other terrestrial crustaceans, this resulting from the protection of the adopted shell. Results obtained from Coenobita are compared with those from other terrestrial and littoral crabs to illustrate the influence of the adopted shell on the degree of modification needed to enter terrestrial habitats.
1 Department of Biology, University of Calgary, Calgary T2N 1N4, Alberta, Canada
2 Zoology Department, University of Massachusetts, Amherts Ma 01003, U.S.A.
The frequencies of heart (fH) and scaphognathite (ventilatory = fBC) pumping, and responses to hypoxia, hypercapnia and wetting (simulated rain), as well as oxygen consumption (MOO2), pre- and postbranchial haemolymph oxygen tension (POO2), oxygen content (COO2), carbon dioxide content (CCOCO2) and pH were measured in adult land crabs Coenobita clypeatus. There was a large increase in f8C in response to both hypoxia and wetting but a smaller increase in response to even severe hypercapnia. Some evidence suggests that ventilation via the scaphognathites may have been supplemented by a second (branchiostegal) pump when ventilatory requirement was high. fH was less responsive to either hypoxia or hypercapnia, but decreased with severe exposure to either. Haemolymph oxygen tensions were low (P{alpha},O{alpha},O2 = 14, PvOvO2 = 8) but haemocyanin oxygen affinity was high in vivo (P50 = 10 torr at 23°C) and postbranchial haemocyanin was 60-80% saturated. Oxygen content was also high allowing adequate oxygen release to the tissues despite the low oxygen tensions. {Delta}P50/{Delta}t = 0.37 torr/{Delta} °C, log {Delta}P50/{Delta}pH = - 0.84 torr/pH unit, both determined in vitro were lower than literature values for marine and littoral species. As in other terrestrial species, CCOCO2 and PCOCO2, (calculated) were high, as were both bicarbonate and non-bicarbonate buffering capacities. Water loss was less (0-08% body weight. h-1) in Coenobita than in other terrestrial crustaceans, this resulting from the protection of the adopted shell. Results obtained from Coenobita are compared with those from other terrestrial and littoral crabs to illustrate the influence of the adopted shell on the degree of modification needed to enter terrestrial habitats.
Observations on the Social Behavior of the Land Hermit Crab, Coenobita Clypeatus (Herbst)
Brian A. Hazlett
Ecology, Vol. 47, No. 2 (Mar., 1966), pp. 316-317
doi:10.2307/1933783
This article consists of 2 page(s).
Abstract
The social interactions of Coenobita clypeatus resemble those of marine hermit crabs in many ways. Stereotyped movements of the chelipeds and ambulatory legs were often executed as two crabs approached each other. Idividuals also have a repertoire of shell fighting behavior patterns, including rotating movements by the attacker and production of a chirping sound by the defender.
Ecology, Vol. 47, No. 2 (Mar., 1966), pp. 316-317
doi:10.2307/1933783
This article consists of 2 page(s).
Abstract
The social interactions of Coenobita clypeatus resemble those of marine hermit crabs in many ways. Stereotyped movements of the chelipeds and ambulatory legs were often executed as two crabs approached each other. Idividuals also have a repertoire of shell fighting behavior patterns, including rotating movements by the attacker and production of a chirping sound by the defender.
Herreid II, C.F. and R.J. Full. 1986. Locomotion of hermit crabs (Coenobita compressus) on beach and treadmill. J. exp. Bio. 120, 283-296.
Coenobita compressus (H. Milne Edwards) walk forward on six legs using an alternating tripod gait similar to that of insects. The first walking leg provides the driving force for locomotion aided secondarily by the second walking leg, while the chelipeds act largely as supports. The left appendages are longer and heavier than the right, and they extend further laterally from the midline during their stride, thus compensating for the asymmetry of the crab which has a dextrally coiled shell and an abdomen displaced to the right. The abdomen is normally carried off the ground, but it is dragged when the shell is large. Bilateral leg autonomy alters gait patterns; usually a diagonal quadrupedal gait was adopted. Walking was poor in crabs without chelae, L(1) and R(1), because of problems of balance. Crabs without their first walking legs, L(2) and R(2), were the most accomplished amputee walkers. Crabs lacking legs L3 and R3 showed the most gait diversity. Velocity of travel is a function of crab size and the substrate walked upon. Large crabs travel faster than small ones on the beach by increasing their stride length rather than stepping frequency. Studies on a miniature treadmill showed individual crabs change velocity by changing both stepping frequency and stride length. Snail shells of the genus Netira are carried; they are the lightest shells on the beach. Shell mass for an individual may vary three-fold, but usually the masses of the shell and crab are similar. Crabs running with and without shells have the same step frequency and stride length.
Sunday, September 23, 2007
Adaptation of Coenobita scaevola (Forskal) Crustacea, Anemura) to terrestrial life desert-bordered shore line
http://www.int-res.com
Achituv* & M. Ziskind
Department of Life Sciences, Bar Ilan University, Ramat Gan 52100, Israel
ABSTRACT: Coenobita scaevola (Forskal) is a terrestrial hermit crab inhabiting shores of the S~nai
Peninsula, where animals encounter severe conditions of high temperature, high radiation and low
relative humidity. Adaptation of these crabs to such arid conditions was studied. The crabs are
nocturnally active, taking refuge during the day in hiding places with milder conditions. Body
temperature follows that of their hiding places, which is lower than that of the air. After ca 6 h exposure
to direct radiation, the crabs die. Thermoregulatory abil~tyis low. Water loss is lower In shelled crabs,
higher in crabs without shell; the shell protects the abdomen from desiccation. Freshly killed crabs
evaporate less than live crabs, suggesting that evaporation from live crabs is not a purely passive
process. Gill surface area is small in comparison with aquatic crabs. Aquatic oxygen consumption is 1.4
times higher than aerial. Unlike other Coenobita spp. which inhabit sites distant from the sea, and in
spite of successful adaptation to terrestrial life, Coenobita scaevola does not penetrate far inland: In
desert conditions it depends on the sea for its only water source.
Achituv* & M. Ziskind
Department of Life Sciences, Bar Ilan University, Ramat Gan 52100, Israel
ABSTRACT: Coenobita scaevola (Forskal) is a terrestrial hermit crab inhabiting shores of the S~nai
Peninsula, where animals encounter severe conditions of high temperature, high radiation and low
relative humidity. Adaptation of these crabs to such arid conditions was studied. The crabs are
nocturnally active, taking refuge during the day in hiding places with milder conditions. Body
temperature follows that of their hiding places, which is lower than that of the air. After ca 6 h exposure
to direct radiation, the crabs die. Thermoregulatory abil~tyis low. Water loss is lower In shelled crabs,
higher in crabs without shell; the shell protects the abdomen from desiccation. Freshly killed crabs
evaporate less than live crabs, suggesting that evaporation from live crabs is not a purely passive
process. Gill surface area is small in comparison with aquatic crabs. Aquatic oxygen consumption is 1.4
times higher than aerial. Unlike other Coenobita spp. which inhabit sites distant from the sea, and in
spite of successful adaptation to terrestrial life, Coenobita scaevola does not penetrate far inland: In
desert conditions it depends on the sea for its only water source.
Extracellular and intracellular acid-base regulation in crustaceans
Michele G. Wheatly 1, Raymond P. Henry 2
1Department of Zoology, University of Florida, Gainesville, Florida 32611
2Department of Zoology and Wildlife Science, Auburn University, Auburn, Alabama 36849-5414
Abstract
This article attempts to review mechanisms of intra- (ICF) and extracellular fluid (ECF) acid-base balance and the contribution each makes to whole animal acid-base homeostasis in an evolutionary progression of crustaceans (marine, freshwater, semi- and fully terrestrial). ICF pH (pHi) is regulated to preserve the functional integrity of enzymes involved in cell metabolism. The ECF is the intermediary between cellular acid/base production and whole animal exchange at the primary epithelia, the gills, and antennal gland. In vivo regulation of pHi is discussed under selected environmental conditions. Compensatory mechanisms include intracellular buffering and transmembrane exchange of acidic/base equivalents including primarily an Na + /H + /HCO3 -/Cl- mechanism and an Na + /H + exchanger. Acid-base values and regulation in the ECF (which may be subcompartmented in selected tissues) differ in aquatic versus terrestrial species. The latter have higher PCO2 (and lower pH) associated with reduced ventilation due to the higher O2 capacitance of air. Correspondingly they can regulate ECF pH (pHe) by respiratory control of PCO2; terrestrial species also depend upon mobilization of exoskeletal CaCO3 to buffer protons. In aquatic species the primary mechanism of acid-base regulation is via electroneutral ion exchangers (Na +/acidic equivalent; Cl -/basic equivalent) primarily at the branchial epithelium but also apparent in the renal tubule in species that produce dilute urine (hyperosmo/ionoregulators). Evidence is presented for dynamic regulation of unidirectional branchial and renal ion fluxes for purposes of acid-base regulation. Quantitatively the antennal gland typically contributes only 10% of the overall response. Stoichiometrically, whole animal acidic/basic equivalents exchanged at these epithelia originate predominantly in the ICF compartment (50--95%). Future perspectives emphasize the need to better understand how pH compensation or in some cases tolerance is related to cellular function. © 1992 Wiley-Liss, Inc.
1Department of Zoology, University of Florida, Gainesville, Florida 32611
2Department of Zoology and Wildlife Science, Auburn University, Auburn, Alabama 36849-5414
Abstract
This article attempts to review mechanisms of intra- (ICF) and extracellular fluid (ECF) acid-base balance and the contribution each makes to whole animal acid-base homeostasis in an evolutionary progression of crustaceans (marine, freshwater, semi- and fully terrestrial). ICF pH (pHi) is regulated to preserve the functional integrity of enzymes involved in cell metabolism. The ECF is the intermediary between cellular acid/base production and whole animal exchange at the primary epithelia, the gills, and antennal gland. In vivo regulation of pHi is discussed under selected environmental conditions. Compensatory mechanisms include intracellular buffering and transmembrane exchange of acidic/base equivalents including primarily an Na + /H + /HCO3 -/Cl- mechanism and an Na + /H + exchanger. Acid-base values and regulation in the ECF (which may be subcompartmented in selected tissues) differ in aquatic versus terrestrial species. The latter have higher PCO2 (and lower pH) associated with reduced ventilation due to the higher O2 capacitance of air. Correspondingly they can regulate ECF pH (pHe) by respiratory control of PCO2; terrestrial species also depend upon mobilization of exoskeletal CaCO3 to buffer protons. In aquatic species the primary mechanism of acid-base regulation is via electroneutral ion exchangers (Na +/acidic equivalent; Cl -/basic equivalent) primarily at the branchial epithelium but also apparent in the renal tubule in species that produce dilute urine (hyperosmo/ionoregulators). Evidence is presented for dynamic regulation of unidirectional branchial and renal ion fluxes for purposes of acid-base regulation. Quantitatively the antennal gland typically contributes only 10% of the overall response. Stoichiometrically, whole animal acidic/basic equivalents exchanged at these epithelia originate predominantly in the ICF compartment (50--95%). Future perspectives emphasize the need to better understand how pH compensation or in some cases tolerance is related to cellular function. © 1992 Wiley-Liss, Inc.
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