Rapaniscus dewdneyi Siebenaller & Hessler, 1981

Wilson, George D. F., 2008, A review of taxonomic concepts in the Nannoniscidae (Isopoda, Asellota), with a key to the genera and a description of Nannoniscus oblongus Sars, Zootaxa 1680, pp. 1-24 : 21-23

Rapaniscus dewdneyi Siebenaller & Hessler, 1981

( Fig. 7 )

Rapaniscus dewdneyi Siebenaller & Hessler, 1981: 234 ; Kussakin, 1999: 117.

Remarks. This species does not require a new diagnosis, but was found to lack a critical piece of evidence relating to the definition of the genus. While reviewing specimens described by Siebenaller and Hessler (1981; Table 1 ), the original publication of the type species, Rapaniscus dewdneyi was found to lack illustrations of pereopod I. Non­type specimens from the type locality (WHOI 209; AM P.74555–P.74557) were illustrated to correct this oversight. Pereopod I of both sexes are nearly identical ( Fig. 7 , male shown), perhaps with the male being slightly more robust; these limbs are also similar to R. crassipes . The second pereopod of R. dewdneyi ( Fig. 7 B) is much less robust than the first. R. multisetosus shows more robust setae on the first two pereopods than either R. dewdneyi or R. crassipes .

Pereopod I of R. dewdneyi in both sexes had a blunt curved spine on the merus that has not been previously reported in nannoniscids. This spine was extremely fragile and broke at the base with even the slightest touch. The spine was discovered when observing specimens at high power in the dissection microscope. Mounting the specimen for illustration caused the spine to break in several cases. This feature may be missing from many species descriptions where it was present, owing to its fragility.

Figures

FIGURE 7. Rapaniscus dewdneyi Siebenaller and Hessler, 1981, Male, AM P. 74555, WHOI 209 (type locality). A, left, pereopod I. B, right pereopod II, arrow indicates small triangular plate. Scales bar, 0.1 mm.