Leather star

Lore & Background

The leather star has a broad central disc and five plump, short arms which taper broadly from the central disc. The arms have two rows of tube feet and no bordering marginal plates. The upper, aboral, surface is smooth and velvety, made more so by the absence of spines and a light layer of mucous. It is covered with a reticulated pattern in reddish-brown, often with patches of greyish-blue. No pedicellariae are present, but the madreporite can be seen. This starfish can grow to about 30 centimetres (12 in) in diameter and has a distinctive smell that resembles garlic and sulphur.

The range of the leather star includes the western seaboard of North America from Cook Inlet, Alaska to northern Mexico. It occurs in Puget Sound. It lives in the intertidal zone and in deeper water down to depths of about 100 metres (330 ft). It is found on rocky bottoms and occasionally sandy seabeds.

The leather star feeds on algae and a range of invertebrates, including other asteroids, bryozoans, sea urchins, sponges, sea cucumbers, hydroids, sea pens, and colonial tunicates. It is in turn preyed on by the morning sun star (Solaster dawsoni). In its attempts to evade this voracious predator, it crawls away at a maximum speed of 15 cm/min, but this is too slow, and leather stars make up 50% of the diet of morning sun stars. Off the Washington coast, spawning is from April to August. The females release yellow eggs which are fertilized in the water column. The larvae then become part of the zooplankton. The leather star sometimes lives symbiotically with the scaleworm Arctonoe vittata. The worm also associates with various other marine invertebrates, but if separated from its host, will search out another member of the same species. The worm may nip off the heads of small tube-dwelling polychaetes as the starfish moves around, but is not harmed by its host. The parasitic barnacle genus Dendrogaster is sometimes an endoparasite of the leather star.

Reader's Guide

The leather star is significant as a common and distinctive sea star of the North American Pacific coast, first described in 1857 by Adolph Eduard Grube. Its smooth, spineless surface and garlic-sulphur odor make it easily identifiable. Ecologically, it plays a dual role as both a predator of many invertebrates and a key prey species for the morning sun star, comprising half of that predator's diet. Its slow crawling speed of 15 cm/min is insufficient to escape this predator. The species also engages in symbiotic relationships, hosting the scaleworm Arctonoe vittata, which may feed on small polychaetes while the starfish moves. Additionally, it can be parasitized by barnacles of the genus Dendrogaster. Its spawning season off Washington runs from April to August, with yellow eggs released into the water column. The leather star's presence in both intertidal and subtidal zones up to 100 meters deep, on rocky and sandy bottoms, underscores its adaptability and importance in benthic communities.

The Leather Star in the 2013 Laboratory Crisis

In October 2013, a marine laboratory in California maintained a seawater tank housing multiple species of sea stars, and it became an unintentional witness to the unfolding wasting disease crisis. The ochre star was the first to show symptoms, with most individuals in the tank developing lesions, losing arms, and perishing within roughly a week. The rainbow star followed, succumbing to the same progressive breakdown. Yet the bat star and the leather star (Dermasterias imbricata), which shared that same confined tank, appear to have fared differently, set apart by the contrast in the record. This laboratory observation arrived at a critical moment: by late August 2013, wasting symptoms had already been documented stretching from Alaska down to the Mexican border, affecting more than twenty sea star species along the Pacific coast. The leather star's presence in that tank, alongside species that were visibly disintegrating, placed it squarely within the geographic and biological scope of the 2013–2014 plague, even as its apparent resilience in that controlled setting hinted at species-level variation in susceptibility to the disease.

The Wasting Disease and Its Devastating Progression

Sea star wasting disease represents one of the most catastrophic die-off events in marine invertebrate history. The progression is methodical and merciless: an infected individual first refuses food, then grows listless over weeks, before white lesions erupt across its surface and spread with alarming speed. The tissue surrounding those lesions decays, the animal's water vascular system collapses, and it can no longer hold its hydrostatic balance. It loses its grip on the rock, its body goes limp, and stretching appears between the arms. Those arms may twist, detach, and continue crawling for a time even after the body has died. The final state is a disintegrated, white, mushy mass that no longer resembles a starfish at all. As of 2025, more than five billion sea stars have been lost since the 2013 outbreak began, with some species suffering population declines exceeding ninety percent. The leather star, as a member of the sea star group on the western North American coast, exists within the same vulnerable community that this disease has systematically dismantled.

Ecosystem Collapse and the Urchin Tide

The vanishing of sea stars from Pacific Northwest coastlines has triggered a cascade of ecological consequences that ripple through the entire marine food web. With the predation pressure removed, sea urchin populations have surged unchecked, feeding voraciously on the kelp forests that once thrived in those waters. This pattern mirrors what was observed after the 1978 wasting event in the Gulf of California, where the local extinction of Heliaster kubiniji—a top-level predator—produced profound and lasting ecosystem disruption; some populations had not recovered even by the year 2000. In the Channel Islands off California, the 1978 event also struck ten sea star species, three sea urchin species, two brittle stars, and a sea cucumber, all experiencing significant population declines. The leather star, as a sea star inhabiting these same western North American waters, occupies a niche within a community that has been fundamentally restructured by the loss of its relatives. The imbalance between urchin grazing and kelp regeneration now defines the landscape of coastlines where sea stars once dominated.

The Elusive Cause and Ongoing Scientific Inquiry

For over a decade, scientists have struggled to identify the definitive agent behind sea star wasting disease. In 2014, a hypothesis emerged linking the disease to a single-stranded DNA virus, the sea star-associated densovirus, but subsequent research in 2018 and 2020 refuted that connection. The puzzle persisted: the disease appeared sporadically, sometimes correlated with elevated water temperatures in certain locales but not others, making a single environmental trigger difficult to confirm. In 2025, a study published in Nature Ecology and Evolution provided a significant breakthrough, demonstrating that the bacterium Vibrio pectenicida, specifically strain FHCF-3, could produce a wasting-disease-like condition in the sunflower star. Meanwhile, tracking the spread of the disease has relied heavily on both professional marine scientists and citizen observers who log sightings of healthy and diseased individuals along the coast. The leather star's apparent resistance in the 2013 California laboratory tank adds another layer to the question of why some species succumb while others endure, a distinction that remains central to understanding the disease's full scope.