Haemolymph composition in spiders and scorpions

Hemolymph cytology, hemocyte count, glucose, and electrolyte reference intervals in 93 Cameroon red tarantulas (Hysterocrates gigas)

BACKGROUND

Theraphosidae is a large family of tarantula spiders commonly kept as pets or display animals by zoological institutions. Interest and demand for arachnid medicine have grown over the last decade. While hemolymph analysis could be a fundamental tool for arachnid health assessment, RIs are generally lacking for arachnid species.

OBJECTIVES

The objectives of this study were to describe the appearance of hemocytes and establish RIs for total and differential hemocyte counts as well as hemolymph glucose and electrolyte concentrations in the Cameroon red tarantula (CRT) (Hysterocrates gigas).

METHODS

Ninety-three CRTs were anesthetized using isoflurane or sevoflurane, and hemolymph was collected from the heart. Hemocyte counts were performed using a hemocytometer and trypan blue stain, and differential cell counts were estimated using light microscopy and a Wright stain. Hemocytes were also characterized with transmission electron microscopy (TEM). Hemolymph glucose and electrolyte concentrations were obtained using a blood gas analyzer. The American Society for Veterinary Clinical Pathology (ASVCP) guidelines were used to calculate RIs.

RESULTS

The most abundant hemocytes were plasmatocytes, followed by granulocytes, cyanocytes, and prohemocytes. Hemocytes were characterized by TEM except for cyanocytes. All RIs had a broad range, likely due to a combination of population heterogeneity, high biologic variability of the species, and the propensity of samples to clot.

CONCLUSIONS

The current study is the first to establish RIs for hemolymph cytologic parameters with a sample size of over 20 individuals in any theraphosid species. RIs for CRT hemolymph biochemical analytes are also reported.

Comparative water relations of four species of scorpions in Israel:evidence for phylogenetic differences

In an attempt to determine the nature of possible interspecific differences in osmotic responses to dehydration, the following species of two scorpion families were examined: Scorpio maurus fuscus (Scorpionidae) and Buthotus judaicus (Buthidae) from the mesic Lower Galilee (mean annual precipitation ∼525 mm); and Scorpio maurus palmatus(Scorpionidae) and Leiurus quinquestriatus (Buthidae) from the xeric Negev Desert (mean annual precipitation ∼100 mm).

When sampled in the laboratory following their capture, B. judaicus (548±38 mOsm l–1; mean ± s.d.) and L. quinquestriatus (571±39 mOsm l–1) had higher and less variable haemolymph osmolarities than the scorpionids occupying the same habitats (511±56 and 493±53 mOsm l–1 for S. m. fuscus and S. m. palmatus, respectively).

In response to 10% mass loss when desiccated at 30°C, the haemolymph osmolarity of the two buthids increased by 5–9%, compared to ca. 23% in the two scorpionids. Buthids had lower water loss rates than scorpionids. The similar oxygen consumption rates, when converted to metabolic water production, imply a higher relative contribution of metabolic water to the overall water budget of buthids. This could explain why the osmoregulative capabilities exhibited by buthids are better than those of scorpionids.

We conclude that the observed interspecific differences in water and solute budgets are primarily phylogenetically derived, rather than an adaptation of the scorpions to environmental conditions in their natural habitat.

Lack of effect of a neurotoxin from the scorpion Buthus martensi Karsch on nerve fibers of this scorpion

A neurotoxin (BmK I) was purified from the venom of the scorpion species Buthus martensi Karsch. Effects of this toxin on the excitability of the abdominal nerve fibers of the same scorpion were examined. The toxin had no effect at all on the action and resting potentials recorded intracellularly even at a concentration as high as 100 microM. A similar result was obtained through optical measurements of the action potential using a potential sensitive dye. Sea anemone toxin II (8 microM) had no effect on nerve excitability either. However, tetrodotoxin (50 nM) reversibly suppressed the action potential and grayanotoxin II (20 microM) induced a sustained depolarization of the nerve membrane which resulted in a reversible suppression of the action potential. BmK I at a concentration of 0.1 microM greatly prolonged the action potential in the crayfish giant axon. We conclude that the Na channel of nerve fibers of this scorpion is totally insensitive to the neurotoxin in this scorpion's venom.