Porcellio echinatus is a rough-backed woodlouse from Portugal, Spain and the north-west corner of Africa, sold as the Shark Skin isopod for the crowded raised bumps on its back, and in a selected 'Red Edge' line with a cream to soft orange rim. Like other Porcellio, it cannot roll into a ball. Our care panels give both lines 18 to 26°C and 50 to 70% humidity, and rate them easy. What matters most is the gradient: a damp end, a drier end and air moving through the tub, never a box that is wet and still all over. Give it 5 to 8 cm of living substrate under leaf litter, bark and flat stones, and calcium at all times. Our Porcellio echinatus 'Red Edge' isopods and standard Porcellio echinatus are both captive-bred.
What Porcellio echinatus Is
Lucas described it in 1849 from Algeria, and the name still stands. Echinatus is Latin for prickly, though the back is studded rather than spiny. Gustav Budde-Lund, in his 1885 monograph of the land isopods, described the head and the middle of the body as very roughly granulated in crosswise rows, with coarser, scattered granules on the sides. Up close, the back is covered in small, rounded bumps.
The published range is southern Portugal, southern Spain, northern Morocco and north-western Algeria. That is the wording of two 2015 papers: Taiti and Rossano's survey of the Oued Laou basin in northern Morocco, which examined 35 specimens collected there in 2004 and 2005, and Reboleira and colleagues' review of the cave woodlice of Portugal. Spanish records also come from Extremadura, Toledo, Ciudad Real and Murcia, and from as far north as Navarra; in Portugal most records come from the Algarve, Setúbal, Lisbon and Leiria. In the Moroccan survey it turned up under stones in a meadow and beside a path, in cork-oak and Phillyrea woodland and near a wheat field. It lives at the surface and only wanders into caves now and then.
Size: Two Published Figures That Do Not Agree
Budde-Lund measured the species at 12 to 14 mm long and 5 to 6.5 mm wide. That is the figure on both our care panels. Julio Cifuentes, in a 2018 study of the Iberian Porcellio, figured six males of 6.5 to 10 mm. The two series do not overlap, and we cannot reconcile them. Budde-Lund does not say what sex his animals were, and Cifuentes's figure compares males of different sizes, so his six are not necessarily full-grown.
The Red Edge Line
Budde-Lund described the species as uniformly grey, a little paler at the edges, with whitish legs, and mentioned no red. The red edge is a line selected in captivity, not a feature of the species: a UK seller says its line was selectively bred for a red band along the outer edge of the body. We have found nothing published on how the colour is inherited. In our gallery photos the Red Edge has the same blue-grey, heavily bumped back as the standard animal, with margins from pale cream to soft orange and pale orange tail points. To hold the edge, keep the two lines in separate tubs, since they are one species and can interbreed.
Which Red Edge Is This?
'Red Edge', sometimes 'Red Skirt', is a trade name, and at least five different animals carry it: this Porcellio, a rolling Cubaris sold as Thai, a Porcellio scaber colour form, an unidentified Porcellio sold as 'Moroccan Red Edge', and the 'Japanese Red Edge' sold as Cubaris iriomotensis, which we list as the Miyako. They are not one group, and they are not kept alike. The Thai Cubaris rolls into a tight ball, and our panel gives it 22 to 26°C and 75 to 85% humidity, a warmer floor and a wetter tub than our echinatus panels. Our Cubaris Red Edge care guide covers that animal. Check the scientific name before you buy.
Setting Up the Tub
A plastic tub with a clip-on lid suits a starter group. My own standard is an 11-litre tub, because more substrate and moss hold humidity and warmth more steadily than a small box. Lay 5 to 8 cm of flake soil, crumbled white-rotted hardwood and organic topsoil, and top it with a thick layer of dead hardwood leaves. Isopods graze the substrate they live in, so leave coco coir out: it holds moisture but is not food. Add cork bark and a few flat stones for cover, with a pad of moss at the damp end; the Moroccan survey found it under stones.
Moving air matters as much as moisture. Stagnant, humid air kills isopods that need airflow; that is a keeper's rule rather than a study, and sellers say the same of this species. I use two to four large vents per tub, and oscillating fans to keep the air moving.
Temperature and Humidity
Our panels give 18 to 26°C for both lines. An English home averages about 19.0°C over the heating season, October to April, 18.1°C in December and about 21.5°C in July and August, so a heated room keeps the tub in the band for most of the year with no heat mat. A room that falls below 18°C in winter wants a heat mat or heat cable on a thermostat, fixed to the side of the tub and never underneath; our guide to heating isopods covers the kit. Sellers give 18 to 26°C or 22 to 25°C, and we have found no published thermal study of this species, so the band is a keeper's figure, not a measurement.
Our panels give 50 to 70% humidity for both lines, and the range covers the whole tub: the drier end near the low figure, the damp end under the moss near the high one. Keep one end damp and let the rest dry back between mistings. Sellers describe it as a medium-humidity animal, and a German seller calls for a semi-moist to dry setup with good ventilation. Its range has hot, dry summers, but the Moroccan survey found it in sheltered spots, mostly under stones and in woodland, and we found no study of how much moisture it prefers. If the substrate turns to mud or smells sour, it is too wet.
Feeding
As a detritivore it lives mainly on leaf litter and rotting hardwood, so keep both in the tub at all times. Add a small piece of vegetable such as courgette, carrot or squash once or twice a week, and lift what is left within a couple of days, before it moulds. Most keepers add a little protein once a week, such as a pinch of fish flakes. Keep calcium in at all times: a cuttlebone, pieces of limestone or both.
Springtails are worth adding, and our springtail cultures are the place to start. I keep tropical white springtails in with all my beetle and isopod colonies, where they graze soft mould on leftover food and in the damp corner, a help rather than a cure.
Breeding
Breeding follows the woodlouse rule: a colony needs both sexes, each female broods her eggs in a fluid-filled pouch under her body, the marsupium, and the young, called mancae, leave it small and pale. We have found no published brood size, age at maturity or lifespan for P. echinatus. Most woodlice live about two years, and some three or four. Sellers call it prolific, while our Red Edge listing says it establishes well and builds at a measured pace, and notes that the bumps and coloured margins develop as the young mature.
I start colonies with 20 or more animals where I can. After that, keep conditions steady, keep food and calcium in, give the females bark and stones to shelter under, and disturb the tub as little as you can.
Behaviour and Handling
Disturbed, it runs rather than rolls, and wedges itself flat into cracks in bark and under stones. Our Red Edge listing calls it surface-active and happy to be seen, a display animal as much as a clean-up crew. It has no bite and no venom; to move one, coax it onto a flat hand instead of picking it up by the body.
Frequently Asked Questions
Is Porcellio echinatus the same as the Red Edge isopod?
Not necessarily. 'Red Edge' is a trade name: a selected line of Porcellio echinatus carries it, but so do a rolling Cubaris sold as Thai and at least three other animals. Check the scientific name.
How big do Porcellio echinatus get?
Budde-Lund measured them at 12 to 14 mm in 1885, the figure on our care panels. Cifuentes figured six males of 6.5 to 10 mm in 2018 to compare their pleopods, so they are not necessarily full-grown. The two do not overlap, and we cannot reconcile them.
Where is Porcellio echinatus from?
Southern Portugal, southern Spain, northern Morocco and north-western Algeria, with Spanish records as far north as Navarra. Lucas described it from Algeria in 1849.
Do Porcellio echinatus need a heat mat?
Not in a heated room for most of the year. Our panels start at 18°C, and an English home averages about 19.0°C over the heating season, but a room that drops below 18°C in winter wants a heat mat or heat cable on a thermostat, fixed to the side of the tub and never underneath.
What humidity do Porcellio echinatus need?
Our panels give 50 to 70% across the tub, with a damp end, a drier end and steady airflow, never wet and still throughout.
Are Porcellio echinatus good for beginners?
Yes. Both our panels rate them easy, and sellers call them very easy. Get the gradient and the airflow right and they need little else.
Where to Go From Here
If you want a Porcellio with more texture than the smooth and speckled species, this is a good one to start with, and the Red Edge adds colour to the same easy care. Set the tub up and let it settle before the animals arrive. There is no single right way to keep any invert, and this one forgives small mistakes. Our guide to the different types of Porcellio isopods covers the rest of the genus.
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