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You are here:   OldClasses > 2012 > Cymodoce pelsarti | Amelia Armstrong






Fact Sheet



Physical Description


Life History & Behaviour

Anatomy & Physiology

Evolution & Systematics

Biogeographic Distribution

Conservation & Threats

References & Links

Physical Description

Size Range

C. pelsarti specimens collected in the study had a size range of 6mm through to 13mm with an average length of 8.6mm (n=18). These measurements correlate with previous collection records from Harrison and Holdich (1984).


C. pelsarti is a sandy colour with darker brown mottled patterns displayed on the epidermis of the dorsal cuticle (Harrison & Holdich, 1984). It was observed that individuals were apparently able to control the amount of darker colouration on their dorsal region with dark captured animals becoming lighter once placing in a white jar (Fig 1). This variability in colouration is achieved through presence of chromatophores. Individuals freshly caught displayed distinct dark colouration that faded significantly once placed in a white container (Oguro, 1959).

Figure 1: Observable colour variation in C. pelsarti following exposure to laboratory conditions. Duration of exposure to these conditions decreases Left to Right. 

Diagnostic Physical Characteristics

Due to the multitude of similarities between species of the genus Cymodoce, it is advisable to determine whether the Isopod is even in the family Sphaeromatidae. This is easily achieved by collecting the individual and seeing if it is capable of enrolling itself into a sphere.  A suite of requirements for each of the labelled parts below (Figure 2) is detailed in depth when identifying individuals to species level. Crustacea are notorious for their associated  in depth terminology and as such, use of identification keys for the inexperienced proves exceptionally challenging. Often the overall body shape or shape of the Pleotelson will be a distinct characteristic from which species can be excluded or identified if imagery is available. 

For this family of Isopods a fantastic online resource containing free publications and imagery is available to assist with identification- Sphaeromatid Isopods Worldwide ( Access to a labelled diagram detailing basic parts (seen below), live and fixed specimens greatly assists in identification below genus level. 

Figure 2: Sketch of Cymodoce cf. pelsarti showing major external anatomy and detailing dorsal colouration.