Nesodillo sp. "Shiro Utsuri" is a striking black and white isopod from Taiwan that has become popular for both its attractive appearance and ease of care. The name comes from Japanese koi terminology—"Shiro Utsuri" refers to a black koi with white markings, which accurately describes this isopod's bold contrasting pattern. At 1.5-2 cm when fully grown, they're a decent size that makes them easy to observe, and their reputation as prolific breeders makes them a solid choice for keepers wanting to build a colony relatively quickly.
A Glimpse
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Origin: Taiwan
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Scientific Name: Nesodillo sp. "Shiro Utsuri"
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Maintenance required: Low
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Average Size: 1.5-2 cm
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Rarity: Low
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Lifespan: 2-3 years
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Temperature: 22-26°C (72-79°F)
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Ventilation: Low to Medium
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Humidity: 70-80%
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Favorite food: Leaf litter, decaying hardwood, vegetables
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Supplements: Cuttlefish bone, crushed eggshells, oyster shell
Shiro Utsuri Isopods: Introduction
Shiro Utsuri isopods originate from Taiwan and belong to the Nesodillo genus. Their common name borrows from Japanese koi breeding terminology—a Shiro Utsuri koi is a black fish with white patterning, and this isopod's bold black and white colouration follows the same theme. Some keepers also refer to them as having a "samurai" appearance due to this high-contrast colouration.
These isopods have earned a good reputation among hobbyists for being beginner-friendly while still offering visual appeal. They're hardy, breed readily, and don't have demanding care requirements. For keepers who want something more interesting than common grey woodlice without the challenges of sensitive exotic species, Shiro Utsuri are a sensible choice.
At 1.5-2 cm as adults, they're a respectable size—large enough to observe and appreciate the patterning clearly. Combined with their willingness to breed in captivity, they're well-suited to keepers wanting to establish and grow a colony.
Shiro Utsuri Isopods: Physical Traits and Characteristics
- Adults reach 1.5-2 cm in length
- Bold black and white patterning across the body
- Predominantly white base colour with black patches and markings
- Pattern varies between individuals, giving each isopod a somewhat unique appearance
- Hard, calcified exoskeleton typical of conglobating species
- Ability to roll into a ball when threatened
- Smooth, domed body shape
- Juveniles display the black and white pattern from an early age
Behaviour
Shiro Utsuri isopods are generally easy-going and adaptable.
Activity levels: Once established, they're reasonably active and visible. They'll forage and explore the enclosure, making them more rewarding to observe than species that hide constantly.
Temperament: Peaceful and non-aggressive. They coexist well with other isopod species and terrarium inhabitants, earning them a reputation as "peaceful cohabitants." This makes them suitable for mixed cleanup crew setups or community bioactive enclosures.
Burrowing: Like many isopod species, they appreciate the ability to burrow and will use hiding spots throughout the enclosure. Providing adequate cover helps them feel secure.
Defence: When threatened, they roll into a tight defensive ball—classic pill bug behaviour.
Settling in: They typically adapt well to new enclosures without extended settling periods. Compared to more sensitive species, they're relatively unfussy about transition.
Diet
Shiro Utsuri isopods are detritivores with straightforward dietary needs.
Primary foods:
- Dried leaf litter (oak, beech, and similar hardwoods)
- Decaying hardwood
- Cork bark
Supplementary foods:
- Vegetables: carrot, courgette, sweet potato, cucumber
- Freeze-dried vegetables work well
- Fish flakes for protein
- Small amounts of fruit occasionally
Calcium: Important for their calcified exoskeletons and healthy moulting. Provide cuttlefish bone, crushed eggshells, or oyster shell as a constant calcium source.
Feeding approach: They're not picky eaters. Maintain a base of leaf litter and decaying wood, supplementing with vegetables every few days. Remove uneaten fresh foods within 24-48 hours to prevent mould. Their willingness to eat a variety of foods makes them easy to cater for.
Shiro Utsuri Isopods: Breeding
This species has a well-deserved reputation as prolific breeders, making them excellent for keepers wanting to grow a colony.
Breeding basics:
- Females carry eggs in a marsupium and release fully formed juveniles
- Breeding rate is relatively fast compared to many species
- Adults reach reproductive maturity within 6-8 months
- Brood sizes are good, contributing to steady population growth
Conditions for breeding:
- Maintain humidity in the 70-80% range
- Stable temperature within preferred range (22-26°C)
- Adequate calcium for breeding females
- Sufficient hiding spots
- Consistent food availability
Colony growth: Under good conditions, expect steady and reliable population growth. They're one of the better species for keepers who want to see their colony expand without the frustratingly slow breeding of some exotic species.
Beginner suitability: Their prolific breeding and forgiving nature make them frequently recommended as a beginner species. New keepers can learn isopod husbandry while actually seeing results, rather than waiting months for slow-breeding species to establish.
Shiro Utsuri Isopods: Habitat Setup
Enclosure: A standard plastic container with a secure lid works well. A 10-15 litre container suits a starter colony, with room to expand as numbers grow. They don't require elaborate setups—functionality matters more than aesthetics for the enclosure itself.
Substrate: Use a moisture-retentive substrate that supports their humidity requirements:
- Organic topsoil as a base (pesticide-free)
- Sphagnum peat moss mixed in for moisture retention
- Leaf litter worked into the substrate and layered on top
- Decaying hardwood pieces
- Crushed limestone or calcium powder throughout
Substrate depth of 5-8 cm allows for burrowing and helps maintain stable humidity at lower levels.
Humidity: These isopods prefer higher humidity than Mediterranean species. Aim for 70-80% humidity. The substrate should remain consistently moist but not waterlogged. Regular misting helps maintain appropriate moisture levels.
Unlike some arid-adapted species, Shiro Utsuri don't require a steep dry/wet gradient—they're comfortable with generally humid conditions throughout, though some variation is fine.
Ventilation: Low to medium ventilation. Some airflow prevents stagnation and mould, but excessive ventilation will dry out the enclosure and work against the humidity these isopods prefer. Small ventilation holes or limited mesh area is sufficient.
Décor and hides:
- Cork bark pieces and tubes
- Flat bark pieces on the substrate surface
- Leaf litter coverage
- Hardwood pieces
- Sphagnum moss patches
Provide plenty of hiding spots. They'll burrow and shelter under cover, and adequate hiding places help them feel secure and encourage natural behaviour.
Temperature: Room temperature works well (22-26°C). They're not demanding regarding temperature and will thrive in normal UK household conditions without supplementary heating in most cases.
Bioactive Use
Shiro Utsuri isopods work well as cleanup crew in appropriate bioactive setups.
Advantages:
- Peaceful nature allows cohabitation with other species
- Prolific breeding maintains population levels
- Good size for functional decomposition work
- Hardy enough to establish in bioactive environments
- Scavenging behaviour helps break down organic waste and maintain substrate health
Suitable setups: They're best suited to humid bioactive enclosures—tropical or subtropical setups for dart frogs, tree frogs, humid-environment geckos, and similar species. Their humidity requirements align well with many popular bioactive inhabitants.
Mixed cleanup crews: Their peaceful temperament means they coexist well with springtails and other isopod species. They won't aggressively outcompete tankmates, making them suitable for diverse cleanup crew combinations.
Suitability
Shiro Utsuri isopods are excellent for beginners and experienced keepers alike.
Good choice for:
- Beginners wanting an attractive, easy first species
- Keepers who want to see colony growth without long waits
- Humid bioactive setups
- Mixed species or community enclosures
- Anyone wanting visual interest without demanding care requirements
Not ideal for:
- Arid or low-humidity setups (they need moisture)
- Keepers specifically wanting slow-breeding, rare species
Care level: Low difficulty. They're forgiving of minor husbandry variations, breed reliably, and don't have demanding requirements. One of the easier species to keep successfully, making them ideal for learning isopod husbandry or for keepers who want results without constant attention.
Value: Excellent value. They offer attractive appearance and reliable breeding at an accessible price point. A sensible choice for building a collection, starting in the hobby, or adding functional cleanup crew to bioactive setups without significant expense.
