Spiders’ Bodies Shift Their Elemental Makeup Dramatically Across a Single Season

Spiders eat an astonishing amount of the world’s insects. By some estimates, the global spider community consumes between 400 and 800 million tons of prey biomass every year, making these eight-legged predators one of the most influential groups of carnivores on land. Yet the way spiders process all that food—what they keep in their bodies and what they release back into the environment—has remained largely a black box, especially when it comes to how those processes change over time. A new study of a common riparian orb-weaver, Larinioides cornutus, now shows that the elemental chemistry of a spider’s body is anything but static. Over a single growing season, the concentrations of nitrogen, phosphorus, and a suite of trace elements in these spiders shifted substantially, in some cases by hundreds of percent, suggesting that the nutrient footprint of invertebrate predators may be far more dynamic than ecologists have assumed.

The research, conducted by Colton Herzog and Shawn Wilder and published in the journal Ecology and Evolution, focused on adult female L. cornutus living in the vegetation along the banks of Lake McMurtry in Noble County, Oklahoma. From mid-June through early October, the team collected twenty spiders during each of seven sampling trips, timed at roughly two- to three-week intervals across the growing season. Each spider was brought into the laboratory and housed individually for seven days under controlled conditions of 25 degrees Celsius and a 14-hour light cycle, with water provided freely. This week-long holding period served a dual purpose: it allowed the animals to clear their guts completely, ensuring that any excreta collected came from the spiders themselves rather than from their last field meal, and it standardized conditions so that differences among sampling dates would reflect seasonal biology rather than laboratory artifacts.

After the holding period, a subset of spiders from each date was frozen, dried at 60 degrees Celsius for 72 hours, weighed to obtain whole-body dry mass, and ground into a homogeneous powder for chemical analysis. Carbon and nitrogen concentrations were measured at the University of Florida Stable Isotope Laboratory, while a broader suite of seventeen additional elements—including phosphorus, potassium, sodium, sulfur, and a range of trace metals—was quantified using inductively coupled plasma optical emission spectrometry at Oklahoma State University. In total, seventy spiders were analyzed for whole-body elemental composition. The remaining spiders were released at sites away from their original collection locations.

Excreta presented a more delicate analytical challenge. Spider waste is produced in tiny quantities, so the researchers pooled low-mass samples from different individuals within each sampling date to obtain enough material for carbon and nitrogen analysis, ultimately processing fifty excreta samples. Because pooling could theoretically distort the data, the team ran a careful series of checks, comparing pooled and unpooled samples for differences in variance, multivariate dispersion, and overall composition. None of these tests detected any effect of pooling, giving the authors confidence that their excreta measurements faithfully reflected the spiders’ waste chemistry. All statistical analyses used generalized linear models with Julian day as a continuous predictor, comparing linear and quadratic seasonal patterns with Akaike’s Information Criterion.

The first major finding concerned body size and waste production. Both followed strikingly similar unimodal trajectories across the season. Spider dry mass rose from early summer, peaked around Julian day 220—August 7—and then declined toward October. Aggregate excreta production followed the same arc, peaking just eight days earlier, around July 30, and falling to its lowest levels at the beginning and end of the sampling period. This tight temporal alignment suggests that mid-summer spiders were both larger and processing more food, likely reflecting peak prey availability during the height of the growing season. The pattern is intuitively satisfying: when resources are abundant, predators eat more, grow more, and excrete more, all at once.

The elemental story, however, proved more surprising. While the carbon and nitrogen concentrations of spider excreta remained essentially stable across the entire season—changes of less than eleven percent that failed to reach statistical significance—the composition of the spiders’ own bodies shifted dramatically. Whole-body nitrogen concentrations declined by 5.77 percent over the season, while phosphorus concentrations moved in the opposite direction, climbing by 25.3 percent. These opposing trajectories in two of the most ecologically important macronutrients mean that a spider eaten by a bird in June delivers a different nutrient package than one eaten in October. Because spiders occupy intermediate trophic levels, serving as both predators and prey, such shifts could ripple through food webs in both directions, altering the timing and composition of nutrient transfer to animals above them and to decomposers below.

The trace element results were even more dramatic. Eight elements—potassium, lithium, manganese, sodium, nickel, sulfur, silicon, and strontium—showed significant seasonal patterns in whole-body concentrations. Lithium rose by nearly 70 percent and silicon by 128 percent over the season, while strontium fell by almost 40 percent. Potassium and sodium followed non-monotonic, mid-season peaks that roughly coincided with the peak in body mass, hinting that shared seasonal drivers such as shifting prey communities or changing physiological demands shape both growth and elemental accumulation. Manganese, sulfur, and strontium have well-established roles in arthropod biology—sulfur in protein structure, strontium as a calcium analog incorporated into the exoskeleton, and manganese in enzymatic reactions and oxidative stress regulation—so their seasonal swings may track genuine physiological needs.

The most eye-catching result of all belonged to nickel, a trace metal with a strong propensity for bioaccumulation. Whole-body nickel concentrations in the spiders increased by a staggering 287 percent across the growing season. Nickel can act as a micronutrient at low doses, but it readily accumulates in arthropod tissues, and previous studies have documented similar accumulation in other spider taxa. The Oklahoma findings suggest that riparian orb-weavers may function as prominent transient sinks for nickel in their food webs, concentrating the metal from their prey and then potentially passing it upward to the birds, wasps, and other spiders that eat them—or releasing it into detrital pathways when they die. Whether consuming nickel-laden spider biomass carries physiological costs for those predators remains an open and potentially important question.

What emerges from this study is a picture of spiders as temporally variable reservoirs of biologically important elements rather than fixed chemical entities. The authors emphasize that the physiological mechanisms behind these shifts remain unresolved. Spiders may prioritize somatic growth early in the season and shift toward reproductive investment later, and because spider eggs differ compositionally from female somatic tissues and can represent a substantial share of total body mass, reproduction could substantially reshape whole-body chemistry. Diet almost certainly plays a role as well: invertebrate prey communities change composition through the season, and elements like lithium and silicon, which appear to be weakly regulated homeostatically, may simply mirror whatever the spiders happen to encounter in their food and environment.

For ecologists, the implications extend well beyond a single species of Oklahoma orb-weaver. If the elemental phenotype of an abundant invertebrate predator can swing this much within a few months, then models of predator-mediated nutrient cycling that assume constant body chemistry may be missing a crucial dimension of temporal variation. Spiders return nutrients to ecosystems through excreta, discarded prey remains, and mortality, and they also export nutrients upward through predation. Quantifying how those fluxes change with the seasons—and how trace metal accumulation in predator biomass affects the animals that consume it—will require integrating ecological stoichiometry with physiology and toxicology. This study provides a template for that integration, and a reminder that even the most familiar backyard predators are chemically far more changeable than they look.

Subject of Research: Seasonal variation in whole-body elemental concentrations and excreta production of the riparian orb-weaving spider Larinioides cornutus

Article Title: Seasonal Variation in Whole‐Body Elemental Concentrations and Excreta Production of a Riparian Orb‐Weaving Spider (Larinioides cornutus)

Article References: Herzog, C., & Wilder, S. M. (2026). Seasonal Variation in Whole‐Body Elemental Concentrations and Excreta Production of a Riparian Orb‐Weaving Spider ( Larinioides cornutus ). Ecology and Evolution, 16(9), Article e74385. https://doi.org/10.1002/ece3.74385

Image Credits: AI Generated

DOI: 10.1002/ece3.74385

Keywords: spiders, ecological stoichiometry, nutrient cycling, trace elements, nickel bioaccumulation, Larinioides cornutus, riparian ecosystems, excreta, seasonal variation, food webs, macronutrients, invertebrate predators