Kenneth N. Prestwich

Energetics of Singing in Crickets: Effect of Temperature in Three Trilling Species (Orthoptera: Gryllidae)

Summary1.Oxygen consumptions of resting and trilling crickets were measured at various temperatures. Oscillograms taken at comparable temperatures were used to identify the major factors determining the cost of stridulation.2.Species used wereAnurogryllus arboreus (mass ≃0.4 g), wing stroke rate at 23°C of 71 strokes per s; andOecanthus celerinictus andO. quadripunctatus, two sibling species, (masses ≃0.06 g), wing stroke rates at 23°C of 57 and 38 strokes per s respectively.3.At 23°C the three species have similar total mass-specific metabolism during singing (

The fluid pressure pumps of spiders (Chelicerata, Araneae)

\dot V_{O_2 }

Anaerobic Metabolism in Spiders

μl·(g·h)−1; Table 3) even though their wing stroke rates are different.4.A. arboreus has no change in net singing metabolism with increasingTa; however, cost per wing stroke decreases slightly. TheOecanthus both increase their net singing costs with increasedTa and the cost per wing stroke remains roughly constant.O. quadripunctatus has a cost per wing stroke about 1.6 timesO. celerinictus (Tables 1, 3; Fig. 10).A. arboreus does not elevate its thoracic temperature significantly while stridulating and it is doubtful that tree crickets thermoregulate due to their small size.5.The cost of singing inA. arboreus varies from 10 to 16 times resting; inOecanthus, from 6 to 12 times resting (Table 3).6.Although the two tree cricket species have different wing stroke rates at any common temperature, the number of file teeth struck per s is almost the same;A. arboreus strikes nearly twice as many teeth per s as do either of the tree crickets (Fig. 9).7.The two factors that explain most of the variation in net cost of trilling are the wing stroke rate (Fig. 10) and the number of teeth struck·(wing stroke)−1. Related factors that merit study are interspecific differences in file tooth depth and angle, wing mass, and wing velocity.8.For three species of crickets and two species of katydids the average net cost of trilling is about 1.5×10−5 ml O2·(g·wing stroke)−1 (Fig. 10).9.Chirping should be energetically less expensive than trilling, with costs equivalent to the average cost per wing stroke times the total number of wing strokes per time. The latter factor is 10–95% lower in chirping species than in trillers.10.An estimated daily respiratory energy budget shows calling taking about 56% of the daily respiratory budget ofO. celerinictus and 26% forA. arboreus (Table 4).

Simultaneous measurement of metabolic and acoustic power and the efficiency of sound production in two mole cricket species (Orthoptera: Gryllotalpidae).

Abstract 1. 1. The cost of web-building and the standard metabolism of a sheet web-building wolf spider, Sosippus janus Brady, were measured at 25°C. 2. 2. The cost of activity is about 18% of the total cost of the web, the remainder being web silk cost. 3. 3. The cost of activity in sheet web-building was compared with a literature value for an orb-weaver and found to be similar. An average value is proposed as useful in estimating the cost of activity for other species of web-building spiders, given the weight of the web.

The physiology of exercise at and above maximal aerobic capacity in a theraphosid (tarantula) spider,Brachypelma smithi (F.O. Pickard-Cambridge)

SummaryThe identity of the fluid pressure pumps in spiders was investigated in Filistata hibernalis through measurements of the activity of certain muscle groups, leg movements, and changes in fluid pressure within the leg. Our results indicate the cephalothorax is the site of the pressure pump responsible for leg extension and the musculi laterales are the major muscles involved in the operation of this pump. Fluid pressures in the legs averaged 5 100 N·m−2 in resting spiders, ranged from 4 000 to 6 700 N·m−2 in walking spiders and reached as high as 61000 N·m−2 in startled spiders. Intra-abdominal fluid pressures were also measured and found to be much lower, ranging from 1000 to 4 000 N· m-2. These pressures are the result of activity of at least two sets of abdominal muscles, the sub-cuticular muscle sheet and the paired series of dorso-ventral muscles. We suggest the abdominal fluid pressure and the rigidity of the book-lungs attenuate pooling of the hemolymph in the abdomen when the spider is active. Finally we hypothesize that evolution of the hydrostatic skeleton in spiders has allowed a greater mass of flexor muscles to be incorporated into the legs and this in turn is an adaptation to the spider in prey capture.

Scaling of subunit structures in book lungs of spiders (Araneae)

The relative importance of aerobic and anaerobic metabolism in active spiders was investigated in four species, Filistata hibernalis, Lycosa lenta, Phidippus audax, and Neoscona domiciliorium. Peak V̇o2 varied from 2.3 to 5.8 times the resting V̇o2. These relatively low increases are suggested as being partially due to arrested hemolymph circulation to the active prosomal muscles. Aerobic capacities were directly correlated with book lung surface area. Late in exercise or early in recovery, about 10%–20% of the individual Lycosa, Filistata, or Phidippus released large (>100 μl) volumes of gas that were composed of gases in addition to CO₂. Estimates of the relative importance of anaerobic metabolism to total power generation during short, maximal struggles (less than 2 min) varied from 55% to 94% of the total power generation. Anaerobic dependence was inversely associated with respiratory surface area. The anaerobic contribution to construction of orb webs in Neoscona domiciliorium was estimated to be about 1% of the total cost of the web. Calculations based on lactate accumulations, recovery oxygen, and the known stoichiometry of gluconeogenesis and complete oxidation of lactate suggest most of the lactate accumulated during a struggle is reconverted to hexose during the recovery period.

The activities of enzymes associated with anaerobic pathways glycolysis and the krebs cycle in spiders

The major anaerobic by-product of spiders is D-(–)-lactic acid. Minor accumulations of L-glycerol-3-phosphate may account for about 5% of the anaerobic ATP production. The possibility remains for other pathways, especially one that results in the accumulation of alanine and succinate. Lactate accumulations after maximal activity are greatest in the legs and prosoma and can be as large as 15 μmol/g; accumulations of lactate in the opisthosoma seldom exceed 4 μmol/g and average near 2.5 μmol/g. Opisthosomal lactate accumulations are inversely correlated with the relative size of the spiders opisthosoma compared with its prosoma. Evidence is presented that suggests that, at a common level of exercise, an inverse relationship exists between prosomal lactate accumulation and book lung surface area.

ANAEROBIC METABOLISM AND MAXIMAL RUNNING IN THE SCORPION CENTRUROIDES HENTZI (BANKS) (SCORPIONES, BUTHIDAE)

SUMMARY We here report the first simultaneous measurement of metabolic cost of calling, acoustic power and efficiency of sound production in animals – the mole crickets Scapteriscus borellii and S. vicinus (Gryllotalpidae). We measured O2 consumption, CO2 production and acoustic power as the crickets called from their burrows in an open room. We utilized their calling burrow as the functional equivalent of a mask. Both species had a respiratory quotient near 0.85, indicative of metabolism based on a mix of carbohydrates and fats. The metabolic rate was significantly higher in S. borellii (11.6 mW g–1) than in S. vicinus (9.0 mW g–1) and averaged about eight- to fivefold greater, respectively, than resting metabolism. In some individuals, metabolic rate decreased by 20% during calling bouts. Costs of refurbishing calling burrows in S. borellii were less than calling costs, due to the behaviors short duration (ca. 15 min) and its relatively low average metabolic rate (4 mW). Acoustic power was on average sevenfold greater in S. borellii (21.2 vs 2.9 μW) and was more variable within individuals and across species than the metabolic rate. The efficiency of sound production was significantly higher in S. borellii (0.23 vs 0.03%). These values are below published estimates for other insects even though these mole crickets construct acoustic burrows that have the potential to increase efficiency. The cricket/burrow system in both species have an apparent Qln decrement of about 6, indicative of significant internal damping caused by the airspaces in the sand that forms the burrows walls. Damping is therefore an important cause of the low sound production efficiency. In field conditions where burrow walls are saturated with water and there is less internal damping, calls are louder and sound production efficiency is likely higher. File tooth depths and file tooth-to-tooth distances correlated with interspecific differences in metabolism and acoustic power much better than with wing stroke rates and plectrum-to-file tooth strike rates. To further investigate these correlations, we constructed two models of energy input to the tegminal oscillator. A model based on transfer of kinetic energy based on differences in tegminal velocity and file tooth spacing showed the most promise. Related calculations suggest that if there are no elastic savings, the power costs to accelerate and decelerate the tegmina are greater than the predicted power input to the tegminal oscillator, and that they are similar in the two species even though S. vicinus has a nearly threefold higher wing stroke rate.