Harris: The copepod genus Porcellidium 
65 
photographs. The delicate hyaline membrane that surrounds 
the cephalosome and metasome segments is not shown 
in the drawing of adult animals, but may be illustrated in 
detail elsewhere. The extremely fine hair-like setules and 
“feathering” of setae found on mouthparts and ambulatory 
limbs is only indicated diagrammatically in the drawings. 
Terminology follows Harris & Robertson (1994). 
Members of the Porcellidiidae are poor swimmers. Their 
antennae and limbs P2, P3 and P4 are highly specialized for 
movement over the surface of seaweed and will be referred 
to as “ambulatory limbs”. Comparison of caudal setae with 
other copepods is difficult because the furca is modified 
for protecting the egg mass. The rami are flattened and the 
setae greatly shortened. There are two dorsal setae (a and 
(3) plus a third (y) which is usually inserted at the lateral 
region of the posterior border. Typically there are four 
terminal setae (T1-T4) on the posterior border of the caudal 
ramus (Figs 21E, 22H), but T1, T2 or T3 may be missing on 
certain species. Wells (2007:871, fig. 120) gives a diagram 
illustrating the differences between the above notation and 
that of Huys & Boxshall (1991). The terms “serrulate” is used 
to denote very fine short serration on setae, “plumulose” is 
used to describe very fine “feathering” on antennule setae 
and “pinnate” for fine feathering on terminal caudal setae. 
Because the caudal rami can be held in line with the body 
or depressed downwards, some animals may appear much 
shorter than others. A more reliable measure is the distance 
from rostrum to the extremity of the genital double-somite. 
This is denoted by the symbol L urs and the distance to the 
extremity of the caudal furca by the symbol L m ax. The male 
antennule is measured in the fully extended position. The 
position of a and (3 seta relative to the posterior border of the 
female caudal ramus is a useful parameter in distinguishing 
between some species. Here it is expressed as the Hick’s 
index defined as the distance of either a or (3 seta from the 
posterior border of the ramus divided by the length of the 
ramus expressed as a percentage (i.e., a/ramus length x 100). 
The following abbreviations are used. NHM—Natural 
History Museum, London; NMI—National Museum of 
Ireland, Dublin; AM—Australian Museum, Sydney. 
Systematics 
Family Porcellidiidae Boeck, 1865 
Type genus: Porcellidium Claus, 1860 
Diagnosis. Antennule of adult male subchirocer, six 
segmented, less than half body width, segment 3 partly 
fused with segment 4, coupling denticles on ventral surface 
of segment 4; antenna exopod of one segment with six 
setae; large mandibular palp, anterior lobe with four bulbous 
setae, posterior lobe with one annulate seta and five bulbous 
setae, endopod with nine setae; cephalosome surrounded by 
hyaline membrane (in one genus the hyaline membrane is 
located on the ventral surface of the cephalosome) with eight 
embedded border sensilla (six or seven sensilla in species 
where the anterior border of the cephalosome is turned 
ventrally); epipleural lobe of metasome segment 3 expanded 
in male, reduced in female; urosome consists of 5th somite, 
genital double-somite, anal somite and caudal furca; furca 
composed of two flat plates or rami each with seven setae, 
setae never longer than ramus, (a and |3 dorsal, y terminal, 
plus four terminal setae [may be reduced to three or two in 
some species]); strong sexual dimorphism. 
Generic composition. Porcellidium Claus, 1860; Tecta- 
cingulum Harris, 1994; Murramia Harris, 1994; Brevifrons 
Harris, 1994; Acutiramus Harris & Robertson, 1994; 
Clavigofera Harris & Iwasaki, 1996b; Kushia Harris 
& Iwasaki, 1996b; Kensakia Harris & Iwasaki, 1997; 
Mucrorostrum Harris & Iwasaki, 1997; Dilatatiocauda 
Harris, 2002; Porcelloides gen. nov. 
Genus Porcellidium Claus, 1860 
Type species. Porcellidium viride (Philippi, 1840). 
Diagnosis [an alternative (apomorphic) character state 
is known for all characters marked with an asterisk], 
Spermatophore elongate* (sausage shaped), female receives 
only one spermatophore during her life span, usually 
deposited on ventral surface of the genital double-somite 
at time of metamorphosis from stage V copepodid to adult, 
attachment to female ephemeral (shed before egg laying 
starts); body oval*, dorsoventrally compressed*; male 
cephalosome truncated anteriorly*, female not truncated 
anteriorly*; animals do not conglobate*; dorsal organs 
absent*, no massive honeycomb-like cuticle; hyaline 
border surrounds cephalosome*, marginal glands open 
dorsal to hyaline border*; female genital double-somite 
broad*, divided into anterior and posterior lobes*, rounded 
posteriorly*, lateral striations absent*; male genital somite 
never fused to metasome segment 4 and P5 baseoendopod*; 
female caudal ramus rectangular*, setae T1 to T4 always 
present* (T1 may be recessed), never pinnately clavate or 
evenly spaced*; no ridge-plates on labrum*; six setae on 
maxillule endopod*; maxilliped coxae touch in midline*, 
basis with fimbriate process*; limbs P2, P3, P4 with three 
external spinous setae on exopod segment 3*; P5 shorter 
than genital double-somite*, ventral expansion absent*; 
male antennule segment 3 setae 5 and 5' always present*, 
anterior comb absent*, blade or knob-like ventral process 
may be present, segment 4 with three denticles*, brush-pad 
never present*; male P5 trapezoid with six setae*. 
Species composition. Porcellidium viride (Philippi, 1840); 
P. fimbriatum Claus, 1863; P. roscoffensis (Bocquet, 
1948) comb. nov. (northeast Atlantic coast of Europe and 
Mediterranean Sea); P. rubrum Pallares, 1966 (Argentina); 
P. erythrum Hicks, 1971 (Aotearoa, New Zealand); P. 
hartmannorum Tiemann, 1978; P. algoense Hicks, 1982 
(East and West coast of South Africa); P. hormosirii Harris 
& Robertson, 1994; P. ocellum Harris & Robertson, 1994; 
P. pulchrum Harris & Robertson, 1994; P. erythrogastrum 
Harris & Robertson, 1994; P. naviculum Harris & Robertson, 
1994; P. phyllosporum Harris & Robertson, 1994; P. 
londonarum Harris, 1994 (name correction for P. londonii by 
Wells, 2007); P. rastellum sp. nov. (East Coast of Australia); 
P. ofunatense Harris & Iwasaki, 1996; P. kiiroum Harris & 
Iwasaki, 1996; P. akashimum Harris & Iwasaki, 1996; P. 
wandoensis Kim & Kim, 1997; P. brevicavum Kim & Kim, 
1997 (Japan and Korea). 
