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Records of the Australian Museum (2014) Vol. 66 
to accommodate the massive adductor muscle that closes 
the finger-like dactylus against the ventral side of segment 
4. This enables the male to grip the posterior region of 
a juvenile female during mate guarding behaviour. The 
number and position of setae on the antennule is more or less 
constant throughout the family, but setae may differ from 
species to species in type (plain, annulate, plumulose) and 
length (compare Figs 28G and 29B). The chitinous coupling 
denticles are not modified setae, they appear de novo at the 
final moult or metamorphosis of the male from stage V 
copepodid to adult, Harris (1994). They are only found on 
the ventral side of segments 3 and 4. Many species do not 
have a denticle on segment 3, but when it is present, there is 
never more than one. Segment 4, however, always has one 
to five denticles. The shape of these denticles varies widely, 
from simple thorn-like structures to complex brush-like 
pads, clusters of denticles (denticulate pads), flat plates with 
plain or serrated edge, comb-like denticles, plain tooth-like 
denticles and even small balloon-like structures (Fig. 12G). 
It is assumed the coupling denticles enable the male to grip 
the female copepodid more effectively by increasing friction. 
There is no evidence for a “locking mechanism” as there is no 
corresponding depressions on the juvenile’s P5 or posterior 
region of the body into which the denticles could fit. Apart 
from differences in size and shape between juvenile stages, 
there is surprisingly little variation in shape or structure of 
the abdominal region between species of female copepodids. 
This suggests the variability of the male’s coupling denticles 
is not connected with a species isolating mechanism or a 
mechanism whereby adult males can distinguish between 
male and female copepodids. 
When the male antennule is compared between species, a 
clear correlation can be seen between certain arrangements 
of denticles (number and shape) and particular genera. 
The clearest example of this is seen in the genus Kushia 
with four described species. The genus is defined by the 
unique ventral expansion on the female P5 (Fig. 16E), but 
the characteristic anterior comb on segment 3 of the male 
antennule is equally unique (Fig. 18E, F); both can be 
regarded as apomorphic characters. Similarly, the brush-pad 
only found on segment 4 of all species of Kensakia should 
be considered autapomorphic. A remarkable similarity in the 
arrangement of denticles can be seen in species belonging to 
other genera. In Fig. 34 the typical arrangement of denticles 
is shown diagrammatically for certain porcellidiid genera. 
The arrangement of denticles can be divided into two groups: 
those with one denticle (or comb) on segment 3 and those 
without a denticle on segment 3. In each group segment 4 
may have two, three, four or five denticles. In the first group 
Kensakia (type A) and Ravania (type B) have only two 
denticles. Kushia (type C) has three denticles of characteristic 
shape. Mucrorostrum (type D) and Murramia (type E) both 
have four denticles, but the shape of the denticles is very 
different in the two genera {Murramia is unique in lacking 
the 5' seta). The second group, without a denticle on segment 
3, is less clearly defined but Clavigofera (type F) appears to 
have two denticles on segment 4 (the antennule has not been 
described for all the known species). Porcelloides has three 
characteristically shaped denticles (type G). Porcellidium 
(type la, lb, Ic) also has three denticles but their shape is 
much more variable. This genus may have a ventral process 
to segment 3 in the shape of a “blade” or “peg”, but this is 
not unique to Porcellidium for it is found in Tectacingulum, 
Acutiramus , Synurus and Dilatatiocauda. The latter genus 
shows another unusual feature, the anterior process carrying 
8 and 8' setae lies parallel to the axis of the antennule 
(horizontal); in most other species the process and 8 seta 
project forwards. 
Because the configuration of the setae and denticles is 
unique for each species, male animals have been chosen as 
the holotype for each of the new species described above. 
Acknowledgment. I am grateful to Yuka (Tadasugi) Sasaki for 
allowing me to examine her extensive collection of Porcellidiidae 
from Japan. 
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