Harris: Male antennule of porcellidiid copepods 
139 
The commensal group do not have an internal seta on 
segment 1 of P3 endopod. 
Acutiramus brevicaudatus (Thompson & Scott, 1903); A. 
tapui (Hicks & Webber, 1983) comb, nov.; A. paguri (Ho, 
1986) comb, nov.;/I. similis (Kim & Kim, 1996) comb, nov.; 
A. cumulus sp. nov.; A. iwasakii sp. nov. 
The algal group have an internal seta on segment 1 of 
P3 endopod. 
Acutiramus geddesi (Geddes, 1968) comb. nov. (synonym 
Porcellidium ovatum Geddes, 1968); A. rufolineatus Harris 
& Robertson, 1994; A. quinquelineatus Harris & Robertson, 
1994; A. sesquimaculatus (Harris, 1994) comb, nov.; A. 
bipunctatus sp. nov.; A. edenensis sp. nov. 
Genus known from Indian Ocean, Madagascar, Ceylon, 
Pacific Ocean, Japan, Korea, Australia, New Zealand and 
Bahamas. 
Remarks. Although no clear apomorphic character defines 
Acutiramus , the genus is clearly separated from Porcellidium 
by a unique combination of characters and is excluded from 
all other genera by their own apomorphies. Relative to 
cephalosome width (W), the genital double-somite width (w) 
of Acutiramus is narrower than that of Porcellidium (mean 
wAV for Acutiramus = 48%, range 40-53%, N = 10 species: 
fox Porcellidium wAV = 62%, range 55-63%, N = 18 species) 
and the posterior lobe is narrow and pointed compared with 
the broad, rounded posterior lobe of Porcellidium species. 
A characteristic feature of all female members of the genus 
is the long P5 limb that extends beyond the posterior limit 
of the caudal furca. On living or freshly preserved animals 
the posterior apices appear to touch, but when mounted 
on a slide the pressure of the cover glass usually separates 
them as shown in Figure 27A. Synurus and Kensakia also 
have P5 limbs that are longer than the caudal furca and may 
touch posteriorly, but their defining apomorphic characters 
eliminate Acutiramus species. 
Porcellidium ovatum Haller, 1879 is a synonym of 
Porcelloides tenuicaudus (see Harris, 2014), but the animals 
identified by Geddes (1968) as Porcellidium ovatum do not 
show the characteristic features of Porcelloides tenuicaudus, 
i.e., female body shape is oval, not ovoid; caudal ramus 
rhomboid, not trapezoid; terminal seta T3 is present; genital 
double-somite is deeply cleft and its arch encloses half 
the caudal furca; dorsal setae on P5 are plain, not pinnate. 
Moreover, Geddes’ female is less than half the size (0.62 
mm compared with 1.4 mm). The shape and setation of the 
female caudal ramus and length of P5 eliminate Geddes’ 
animals from Porcellidium and the presence of T3 eliminates 
them from Ravania and Kensakia. They are included here as 
Acutiramus geddesi (Geddes, 1968) comb. nov. 
Walker-Smith (2001) argues that the genus Kioloaria 
possesses the same character set as Acutiramus except for 
the number of setae on male P2 limb. This character cannot 
be considered apomorphic because it occurs sporadically in 
other genera and so there is no justification for maintaining 
Kioloaria. This argument is accepted, although K. 
sesquimaculata does have an unusual male antennule. It is 
move&to Acutiramus A. sesquimaculatus (Harris, 1994). 
Kioloaria now becomes a junior synonym of Acutiramus. 
Key to the species of Acutiramus 
1 No internal seta on segment 1 of P3 endopod. Animals live in 
association with hermit crabs . 2 
- Internal seta present on segment 1 of P3 endopod. Animals live 
on seaweed . 6 
2 Female caudal ramus rhomboid, T2 and T3 close together, 
wide gap between T3 and T4. Male shoulders rounded. 3 
- Female caudal ramus not rhomboid, tapers posteriorly, posterior 
edge rounded, no network of ridges (if present not prominent, 
restricted to posterior). T2, T3 and T4 evenly spaced. Male 
shoulders rounded . Acutiramus tapui (Hicks & Webber, 1983) comb. nov. 
- Female caudal ramus rhomboid with conspicuous dorsal network 
of ridges, T2, T3 and T4 bunched together at apex. Male 
shoulders prominent . Acutiramus cumulus sp. nov. 
3 % or more of caudal ramus enclosed in arch of genital double¬ 
somite . 4 
- Caudal ramus completely excluded from arch of genital double¬ 
somite . Acutiramus brevicaudatus (Thompson & Scott, 1903) 
4 Number of setae on internal edge of P3 endopod = 0:2:4, P4 
endopod = 0:1:3. Acutiramus paguri (Ho, 1986) comb. nov. 
- Number of setae on internal edge of P3 endopod = 0:2:5, P4 
endopod = 1:1:4. 5 
5 Female rostrum appears concave with straight hyaline border. 
Male rostrum with conspicuous anterior point, y seta on male 
caudal ramus equals width of ramus . Acutiramus iwasakii sp. nov. 
- Anterior border of female rostrum not concave. Male rostrum 
not pointed anteriorly, y seta on male caudal ramus twice width 
of ramus. Acutiramus similis (Kim & Kim, 1996) 
