66 
Records of the Australian Museum (2014) Vol. 66 
Key to the species of Porcellidium 
The antennules of male porcellidiids provide numerous species specific characters, consequently any 
male animal, for which the antennule has been described in detail, can be identified with a high degree of 
certainty. In marked contrast, very few species specific characters have been found on female members 
of the genus Porcellidium , consequently the females of less than half of the 20 recognized species can 
be identified. This is because female characters are based upon shape, position, size or number of body 
parts which will vary within a species and their measurements or ratios may overlap with other species. 
The following key will rely heavily on characters of the male antennule which must be viewed from 
the ventral side in the fully extended position (see Methods and nomenclature). Female ratios are given 
to help confirm the identity of the female animals. [Abbreviations: CR caudal ramus; GDS genital double¬ 
somite; L length of animal; H.I. Hicks’ index for a or (3 setae; * see Hicks, 1982:64], 
1 Male antennule with ventral process or “blade” on segment 3 
(see Fig. 12D, F). 2 
- Male antennule with “peg” or swollen knob on segment 3 
(see Fig. 7F). 3 
- No blade, peg or knob on segment 3 of male antennule .4 
2 Ventral process short (% length of segments 3+4), coupling 
denticle 1 on segment 4 flat with serrated edge, denticles 2 and 3 
very small, botryoidal, segment 6 distinct (not fused with segment 
5). Ventral surface of male and female cephalosome wrinkled 
(Fig. 12A). Female GDS with deep cleft between anterior and 
posterior lobe. Body length male 0.56 mm, female 0.77 mm, 
CR/L = 18%, CR 1/w = 2.8, H.I. for (3 = 25%, setae T1-T4 
pinnate. Colourless with broad band of dark blue down middle 
of back. Europe. (Plate 1C,E, p. 67). P.fimbriatum (Claus, 1863) 
- Ventral blade almost as long as segments 3+4, segment 3 with 
spine ventral to 6 seta, denticle 1 on segment 4 comb-like, 2 
and 3 serrate, segment 5 hooked, fused with 6. Body length 
male 0.55 mm, female 0.71 mm, CR/L = 7%, CR 1/w = 1.2, 
H.I. for |3 = 20%. Colour yellow with broad red dorsal stripe. 
Australia. (Plate 2B, p. 69). P. pulchrum Harris & Robertson, 1994 
- Ventral blade bifid, % length of segments 3+4, denticle 2 
on segment 4 spherical with surface serrations, denticle 
3 large flat triangle with distal border serrated, segment 5 
not hooked fused with 6. a seta on female CR thicker than 
other setae. Body length male 0.50 mm, female 0.68 mm, 
CR/L = 12%, CR 1/w 1.7, H.I. for (3 = 22%. Amber colour. 
Australia . P. hormosirii Harris & Robertson, 1994 
- Ventral blade l A length of segments 3+4, segment 3 with finger¬ 
like lobe pointing forward ventral to 5 seta, denticles 1, 2 and 
3 triangular with double serrated edge, segment 6 fused with 5. 
Body length male 0.56 mm, female 0.67 mm, CR/L = 6%, CR 
1/w 1.5, H.I. for |3 = 32%, GDS with lateral notch. Colourless 
with red area round ocellus and larger red dot in middle of back. 
Australia. (Plate 2H, p. 69). P. ocellum Harris & Robertson, 1994 
- Ventral blade % length of segments 3+4, denticle 1 on segment 
4 comb-like, 2 and 3 with serrated edge, segment 5 small, fused 
with 6. Body length male 0.61 mm, female 0.83 mm, CR/L = 
5.5%, CR 1/w 1.45, H.I. for |3 = 10%, GDS with lateral notch. 
Colourless with areas of thickened ventral cuticle dark red. 
Australia. (Plate 2A, p. 69). P. erythrogastrum Harris & Robertson, 1994 
- Ventral blade 3 A length of segments 3+4, denticle 1 on segment 
4 double serrated, 2 tooth-like, 3 with serrated edge, segment 5 
hooked, fused with 6. Body length male 0.57 mm, female 0.75 
mm, CR/L = 11%, CR 1/w 2.2, H.I. for |3 = 9%, GDS with scar 
and very small notch. Coral pink with small iridescent light blue 
areas at trabeculae, GDS scar and between metasome segments. 
Australia. (Plate 2F, p. 69) . 
P. londonarum Harris, 1994 
