042. THE EFFECT OF THE INSECTICIDE PYRIPROXYFEN ON OVARY SYNTHESIS IN THE CHRISTMAS ISLAND RED CRAB, GECARCOIDEA NATALIS; A POSSIBLE CASE OF ENDOCRINE DISRUPTION?

2010 ◽  
Vol 22 (9) ◽  
pp. 14
Author(s):  
S. M. Linton ◽  
L. Barrow ◽  
C. Davies ◽  
L. Harman
Keyword(s):  
Leaf Litter ◽  
Endocrine Disruption ◽  
Dry Mass ◽  
Ovary Development ◽  
Environmental Damage ◽  
Target Tissue ◽  
Methyl Farnesoate ◽  
Christmas Island ◽  
Land Crabs ◽  
Gecarcoidea Natalis

The yellow crazy ant, Anopholepis gracilipes is an invasive species on Christmas Island, Indian Ocean whose population needs to be controlled before there is irrevocable environmental damage. The insecticide, pyriproxyfen, a compound which mimics juvenile hormone of insects, has been proposed to do this. Before it can be used in the field, its effects on non target species such as the endemic red crab, Gecarcoidea natalis, need to be investigated. Land crabs, like all decapods, may utilise a similar hormone called methyl farnesoate which is thought to be involved in controlling early ovary development. Pyriproxyfen may also mimic methyl farnesoate and thus disrupt this process. The effect of pyriproxyfen on early ovary synthesis in G. natalis was investigated by feeding crabs a mixture of leaf litter and bait containing 0.5% pyriproxyfen (experimental groups) or a mixture of leaf litter and bait containing no pyriproxyfen (control groups) at simulated baiting doses (2 kg ha–1 and 4 kg ha–1). Two additional groups of crabs were fed ad libitum, either bait containing 0.5% pyriproxyfen or the control bait. Experiments were conducted from July to September of 2007. Red crabs synthesise their ovaries annually over two months (July to September) in the dry season. This situation of high nitrogen demand is funded from small excesses of nitrogen assimilated from a mainly leaf litter diet. Pyriproxyfen affected early ovary development. Ovaries from crabs in the experimental groups at all baiting levels had a higher total nitrogen content and dry mass than that of the control animals. The ovaries from the experimental animals were also more mature; they contained more previtellogenic and early vitellogenic oocytes, of a larger diameter, than ovaries of the control animals. Significant amounts of pyriproxyfen were accumulated in the target tissues, the midgut gland and ovary. Minor amounts of pyriproxyfen were accumulated in muscle, a non-target tissue. By mimicking methyl farnesoate, pyriproxyfen may have caused endocrine disruption in G. natalis. In particular it may have stimulated early ovary development and synthesis of yolk protein.

The functioning of the haemocyanin of the terrestrial christmas island red crab gecarcoidea natalis and roles for organic modulators

1998 ◽  
Vol 201 (23) ◽  
pp. 3233-3244 ◽  
Author(s):  
A. M. Adamczewska ◽  
S. Morris
Keyword(s):  
Lactate Concentration ◽  
Specific Effect ◽  
Time Dependent ◽  
Binding Properties ◽  
Christmas Island ◽  
Land Crabs ◽  
Gecarcoidea Natalis ◽  
O2 Binding

Gecarcoidea natalis is a land crab that migrates annually several kilometres to breed. The O2-binding properties of haemocyanin in G. natalis were investigated in vitro to test the idea that the O2-binding properties of the haemocyanin of land crabs are not dependent on circulating modulators and to provide a model of haemocyanin functioning during exercise. The affinity of the haemocyanin for O2 decreased with increasing temperature (change in the heat of oxygenation; capdelta H=-59 kJ mol-1). The haemocyanin of G. natalis apparently differs from that of other terrestrial crabs in showing haemocyanin O2 modulation by both organic and inorganic molecules. Haemocyanin O2-affinity was not affected by Mg2+ but was sensitive to changes in Ca2+ concentration ( capdelta logP50/ capdelta log[Ca]=-0.61, where P50 is the partial pressure of O2 required for half-maximal O2 binding). The Bohr factor was modest ( &phgr;=-0.26+/-0.03, N=4, in whole haemolymph at 25 degreesC) and there was no specific effect of CO2 on the O2-binding properties of the haemocyanin. An increase in urate concentration increased haemocyanin O2-affinity, but the effect was linear ( capdelta logP50/ capdelta [urate]=-0.06) and not logarithmic as is the case in other species. The effect of l-lactate on the haemocyanin O2-affinity in G. natalis was unique among the crustaceans,because an increase in l-lactate concentration decreased the haemocyanin O2-affinity. The effect of l-lactate on haemocyanin O2-affinity ( capdelta logP50/ capdelta log[lactate]) was time-dependent and decreased from a maximum of 0.044 on day 1 to 0.001 after 4 days of storage at 4 degreesC. The presence of an unknown dialysable and unstable factor in the haemolymph is postulated to explain the time-dependent effect of l-lactate on haemocyanin O2-binding properties. Model oxygen equilibrium curves constructed for in vivo conditions showed that the reverse effect of l-lactate was advantageous by decreasing the O2-affinity of the haemocyanin beyond that predicted by the Bohr shift alone and assisted in O2 off-loading at the tissues. This effect of lactate can only provide an advantage if the gas-exchange organs maintain arterial O2 loading and thus is dependent on lung function in land crabs and must have occurred coincident with the evolution of these other features.

scholarly journals Post-fire consequences for leaf breakdown in a tropical stream

2019 ◽  
Vol 31 ◽  
Author(s):  
Renan de Souza Rezende ◽  
Cristiano Queiroz de Albuquerque ◽  
Andrezza Sayuri Victoriano Hirota ◽  
Paulo Fernandes Roges Souza Silva ◽  
Ricardo Keichi Umetsu ◽  
...  
Keyword(s):  
Leaf Litter ◽  
Fungal Biomass ◽  
Mesh Size ◽  
Fire Effects ◽  
Dry Mass ◽  
Tropical Stream ◽  
Fire Event ◽  
Litter Bags ◽  
Fine Mesh ◽  
Post Fire Effects

Abstract Aim Wildfire is a natural pulsed disturbance in landscapes of the Savannah Biome. This study evaluates short-term post-fire effects on leaf litter breakdown, the invertebrate community and fungal biomass of litter from three different vegetal species in a tropical stream. Methods Senescent leaves of Inga laurina, Protium spruceanum and Rircheria grandis (2 ± 0.1 g dry mass) were individually placed in litter bags (30 × 30 cm: 10 mm coarse mesh and 0.5 mm fine mesh) and submerged in the study stream before and after fire. Replicate bags (n = 4; individually for each species, sampling time, fire event and mesh size) were then retrieved after 20 and 40 days and washed to separate the invertebrates before fire event and again immediately after fire. Disks were cut from leaves to determine ash-free dry mass, while the remaining material was oven-dried to determine dry mass. Results The pre-fire mean decomposition coefficient (k = -0.012 day-1) was intermediate compared to that reported for other savannah streams, but post-fire it was lower (k = -0.007 day-1), due to decreased allochthonous litter input and increased autochthones production. Intermediate k values for all qualities of litter post-fire may indicate that fire is equalizing litter quality in the stream ecosystem. The abundance of scrapers was found to be more important than fungal biomass or shredder abundance, probably due to their functioning in leaf fragmentation while consuming periphyton growing on leaf litter. Conclusions Theses results indicate that fire can modify the relationships within decomposer communities in tropical stream ecosystems.

EXERCISE IN THE TERRESTRIAL CHRISTMAS ISLAND RED CRAB GECARCOIDEA NATALIS - BLOOD GAS TRANSPORT

1994 ◽  
Vol 188 (1) ◽  
pp. 235-256 ◽  
Author(s):  
A Adamczewska ◽  
S Morris
Keyword(s):  
Gas Transport ◽  
Lactate Production ◽  
Circulatory System ◽  
Indirect Evidence ◽  
Blood Gas ◽  
Christmas Island ◽  
Exercise Period ◽  
Gas Measurements ◽  
Gecarcoidea Natalis ◽  
O2 Delivery

The respiratory and circulatory physiology of the terrestrial Christmas Island red crab Gecarcoidea natalis was investigated with respect to exercise in the context of its annual breeding migration. Red crabs were allowed to walk for predetermined periods of up to 45 min. During this exercise period, blood gas measurements were made on venous, pulmonary and arterial samples to assess the function of the lungs in gas exchange and the performance of the circulatory system in gas transport and to determine the role and importance of the haemocyanin. The lungs of G. natalis were very efficient at O2 uptake, pulmonary blood being 80­90 % saturated throughout the 45 min exercise period. The maximum O2-carrying capacity was 1.1 mmol l-1, and haemocyanin (Hc) delivered 86 % of oxygen in resting crabs and 97 % during exercise. Oxygen delivery to the tissues was diffusion-limited during exercise. Indirect evidence, from the changes in haemolymph pH during transit through the lungs, suggested that the lung is the site of CO2 excretion. The Bohr shift was high at high pH (pH 7.8­7.5, phi=-1.23) but decreased at low pH (pH 7.1­6.8, phi=-0.48). The decreased Hc affinity for O2 during the exercise period facilitated O2 delivery to the tissues without impairing O2 loading at the lungs. The decrease in pH was sufficient to explain the change of affinity of Hc for O2 during the exercise period. The marked acidosis (0.8 pH unit decrease) was largely metabolic in origin, especially during sustained locomotion, but less than could be predicted from concomitant lactate production.

scholarly journals Response of nutrients, biofilm, and benthic insects to salmon carcass addition

2006 ◽  
Vol 63 (6) ◽  
pp. 1230-1241 ◽  
Author(s):  
Shannon M Claeson ◽  
Judith L Li ◽  
Jana E Compton ◽  
Peter A Bisson
Keyword(s):  
Leaf Litter ◽  
Litter Decomposition ◽  
Headwater Streams ◽  
Dry Mass ◽  
Trophic Levels ◽  
Leaf Litter Decomposition ◽  
Ammonium Concentration ◽  
Benthic Insects ◽  
Salmon Carcass ◽  
Density And Biomass

Salmon carcass addition to streams is expected to increase stream productivity at multiple trophic levels. This study examined stream nutrient (nitrogen, phosphorus, and carbon), epilithic biofilm (ash-free dry mass and chlorophyll a), leaf-litter decomposition, and macroinvertebrate (density and biomass) responses to carcass addition in three headwater streams of southwestern Washington State, USA. We used stable isotopes (δ13C and δ15N) to trace incorporation of salmon-derived (SD) nutrients into stream food webs. SD nutrients were assimilated by biofilm, benthic insects (Perlidae and Limnephilidae spp.), and age-1 steelhead (Oncorhynchus mykiss gairdneri). SD nutrients peaked ~2 weeks after carcass addition for insects and fish feeding on carcasses, but indirect uptake of SD nutrients by biofilm and insects was delayed by ~2 months. A strong stable isotope signal did not always correspond with measurable biological change. At reaches 10–50 m downstream from carcasses, ammonium concentration, leaf-litter decomposition, and benthic insect density all increased relative to upstream control sites. The strongest responses and greatest SD-nutrient uptake were observed 10 m from decomposing carcasses, with effects generally decreasing to undetectable levels 250 m downstream. Carcass addition to headwater streams can have a transient effect on primary and secondary trophic levels, but responses may be limited to specific taxa near carcass locations.

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