Effects of sevoflurane anesthesia on righting reflex and hemolymph gas analysis variables for Chilean rose tarantulas (Grammostola rosea).

OBJECTIVE: To determine the safety, efficacy, and effects on hemolymph gas analysis variables of sevoflurane anesthesia in Chilean rose tarantulas (Grammostola rosea). ANIMALS: 12 subadult Chilean rose tarantulas of unknown sex. PROCEDURES: Spiders were anesthetized in a custom chamber with sevoflurane (5% in oxygen [1.0 L/min]), then allowed to recover in 100% oxygen. Righting reflex was evaluated every 3 minutes during anesthesia to determine time to anesthetic induction and recovery. Hemolymph samples were collected from an intracardiac location prior to and after induction of anesthesia and evaluated to determine various gas analysis variables. RESULTS: Mean ± SD induction and recovery times were 16 ± 5.91 minutes and 29 ± 21.34 minutes, respectively. Significant differences were detected for Po2, base excess, and glucose and ionized magnesium concentrations between hemolymph samples obtained before anesthesia and those obtained after induction of anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE-Results of this study suggested that the use of sevoflurane as an anesthetic agent for Chilean rose tarantulas was safe and effective. Various hemolymph sample gas analysis values changed during anesthesia.

To breed or not to breed: physiological correlates of reproductive status in a facultatively biennial iguanid.

It is unusual for seasonal breeders to frequently skip opportunities for reproduction. We investigated the relationship between physiological state and reproductive decision-making in Galápagos marine iguanas (Amblyrhynchus cristatus), a species in which females typically reproduce biennially, although the proportion of breeding individuals varies significantly across years. Nearly all adult-sized females initiated follicular development prior to the lekking period, but 38% of females resorbed all developing follicles 5-15 days before the start of copulations. Receptive and non-receptive females differed in reproductive hormones during the mate choice period. Testosterone peaked in receptive females immediately prior to copulation, indicating that testosterone or its derivative estradiol likely mediates female receptivity in Galápagos marine iguanas. Non-receptive females showed significant peaks in both testosterone and progesterone during follicular atresia, suggesting that these hormones may be involved in inhibiting vitellogenesis. Two to three weeks prior to the period of reproductive decision-making (and the onset of follicular atresia in non-receptive females) receptive females were in higher body condition, were developing larger follicles, and had lower levels of both baseline and stress-induced corticosterone. Reproduction is extremely costly in this long-lived species, and increases the likelihood of mortality in the year following breeding; females could therefore gain significant benefits from being attuned to indicators of reproductive success. We suggest that corticosterone may modulate reproductive decisions by altering individual sensitivity to both internal and external cues of the likelihood of successful reproduction.

Isoflurane anesthesia of wild-caught goliath birdeater spiders (Theraphosa blondi) and Chilean rose spiders (Grammostola rosea).

Anesthesia is used in theraphosid spiders to facilitate medical procedures (e.g., physical examination, sample collection, surgery); however, most information on this subject is anecdotal. This study was conducted to systematically determine the anesthetic parameters of wild-caught, subadult goliath birdeater spiders (Theraphosa blondi) (n = 11) and Chilean rose spiders (Grammostola rosea) (n = 12). Each spider was placed in a 3-L gas anesthetic chamber and subjected to an induction of 5% isoflurane at a rate of 1 L/min oxygen. Anesthetic depth was monitored by evaluating the righting reflex every 5 min. Animals were recovered in 100% oxygen. Induction, recovery, and overall anesthetic times were determined. After an 8-wk washout period, the procedure was repeated. For both species, median induction time was 10 min. Median recovery time was 30 min for T. blondi and 12.5 min for G. rosea.

Function of muscle-type lactate dehydrogenase and citrate synthase of the Galápagos marine iguana, Amblyrhynchus cristatus, in relation to temperature.

The Galápagos marine iguana, Amblyrhynchus cristatus, is unique among lizards in foraging subtidally, leading to activity across a broad range of ambient temperatures ( approximately 14-40 degrees C). To determine whether the marine iguana shows any biochemical changes consistent with maintaining enzyme function at both warm and cold body temperatures, we examined the function of the aerobic enzyme citrate synthase (CS) and the muscle isoform of the anaerobic enzyme lactate dehydrogenase (A(4)-LDH) in A. cristatus and a confamilial species, Iguana iguana, from 14 to 46 degrees C. We also deduced amino acid sequences from cDNA of each enzyme. In CS, despite two amino acid substitutions, we found no difference in the apparent Michaelis-Menten constant K(m) of oxaloacetate at any temperature, indicating that the substrate affinity of CS in A. cristatus has not adapted to changes in thermal environment. In A(4)-LDH, we used site-directed mutagenesis to show that the substitutions T9A and I283V (A. cristatus --> I. iguana) individually have no effect on kinetics, but together significantly decrease the K(m) of pyruvate and catalytic rate constant (k(cat)) of the A. cristatus ortholog. Thus, our data show that A. cristatus A(4)-LDH has not become cold adapted in response to this species' aquatic foraging behavior, and instead may be consistent with moderate warm adaptation with respect to the I. iguana ortholog.

Hemolymph biochemistry reference ranges for wild-caught Goliath birdeater spiders (Theraphosa blondi) and Chilean rose spiders (Grammostola rosea).

Theraphosid spiders have become increasingly popular for private and public uses in the United States. However, little is known about their physiology from a medical standpoint. This study represents the first attempt to establish reference hemolymph values for two common species of theraphosids, the goliath birdeater spider (Theraphosa blondi) and the Chilean rose spider (Grammostola rosea). Eleven T. blondi and twelve G. rosea, all wild-caught subadults, were obtained after importation and hemolymph was collected for biochemical analysis. After 8 wk of captivity, hemolymph was again collected from the spiders and analyzed. The biochemical analytes measured in the study included aspartate transferase, creatine kinase, glucose, total protein, albumin, uric acid, blood urea nitrogen, phosphorous, calcium, potassium, and sodium. The osmolality of the hemolymph was estimated for each spider using two different formulae. There were significant differences in body weight, sodium, potassium, and osmolality between the sampling times for both species. There were also significant differences in creatine kinase, calcium, total protein, and blood urea nitrogen between sampling periods for T. blondi. The results of this study suggest that serial hemolymph samples may be used to assess the hydration status of theraphosid spiders. In addition, the differences in hemolymph analytes between spiders suggest that there may be differences between species that should be addressed in future studies.