Harris: Male antennule of porcellidiid copepods 
129 
Genus Kensakia Harris & Iwasaki, 1997 
Kensakia Harris & Iwasaki, 1997: 136. 
Acutiramus. —Harris & Robertson, 1994: 289. 
Porcellidium. —Thompson & Scott, 1903: 275; Kim & Kim, 
1997: 153; Walker-Smith, 2001: 665; Wells, 2007: 79. 
Type species. Kensakia acuta (Kim & Kim, 1997) 
Diagnosis. Segment 3 of male antennule with triangular 
denticle at base of 5 seta (not comb-like), segment 4 with 
large pad of hair-like setules (brush-pad) and small distal 
denticle; adult female genital double-somite cordate, 
caudal ramus trapezoid, terminal seta T1 present, T2 absent 
from female but present on male caudal ramus, T3 absent 
from both male and female; ventrolateral band of surface 
markings on underside of cephalosome; maxillule endopod 
with six setae; coxal lobes of maxillipeds touch in midline; 
spermatophore elongate, ephemeral on female. 
Species composition. Kensakia acuticaudata (Thompson 
& Scott, 1903) comb, nov.; Kensakia acuta (Kim & Kim, 
1997); K shimodensis Harris & Iwasaki, 2009; K parva 
Harris & Iwasaki, 2009; K australis sp. nov. 
The genus has a wide range. It is represented in Japanese 
and Korean waters, southern Gulf of Thailand, North East 
coast of Australia, Sri Lanka and the Suez Canal. 
Etymology. The specific name refers to the pointed shape 
of the caudal rami (Japanese, Kensaki = point of a sword). 
Remarks. The genus was first defined to accommodate a 
single species from Kadonohama Bay, Iwate Prefecture, 
Japan, Harris & Iwasaki (1997). Since then three closely 
related species have been collected from Japan, Malaya and 
Australia which share the same unique set of characters and 
justify admission to the genus. 
The characteristic brush-pad of male Kensakia differs 
from the denticulate pad described for genera such as 
Murramia or Porcelloides because it is only attached to the 
antennule by its proximal edge. It is possible to lift it up as 
a flap (see Figs 131). It is the most conspicuous apomorphic 
character defining the genus. Markings on the under surface 
of the cephalosome (see Fig. 131, left figure) may form a 
band parallel to the hyaline border (ventrolateral band). It has 
been found on all species examined. This band is structurally 
different from the condition in Tectacingulum because it 
does not involve displacement of the hyaline membrane or 
its sensilla. 
The diagnostic characters listed above clearly separate 
members of Kensakia from other superficially similar genera 
(i.e., Ravania, Acutiramus and Porcelloides). 
Female specimens in the NHM collection labelled 
Porcellidium acuticaudatum Thompson & Scott 1903 
(1928, 4,2,43), collected from Lake Timsah, Ismalia, by 
the Cambridge University Expedition to the Suez Canal, 
Gurney (1924), were examined by the author. Females 
have a trapezoid caudal ramus, but T2 and T3 are missing 
which eliminates them from Porcelloides. They also have a 
distinct notch at the posterior end of the falciform ridge on 
P5 (compare with Fig. 14A). These are all characteristics of 
Kensakia and eliminate P. acuticaudatum from Porcellidium, 
Acutiramus and Ravania. Unfortunately, details of the 
male antennule, which would have confirmed that P. 
acuticaudatum belongs to Kensakia , could not be resolved 
on the specimen examined, however the male cephalosome 
is only slightly truncated with broadly rounded shoulders 
as in K australis. Illustration of the male by Gumey (1927) 
lacks important detail, but P5 is shown trapezoid and P2 has 
two terminal setae on endopod. This suggests that the species 
should be renamed Kensakia acuticaudata (Thompson & 
Scott, 1903) comb. nov.Thompson & Scott found three 
female specimens in washings from Muttuvaratu pearl 
oysters, Sri Lanka (formerly Ceylon), but material from 
Ismalia was washed from Sargassum sp., and Halophila sp., 
Gurney (1927). The species is described as “...vivid rosy 
red or red spots on thorax and abdomen”, Gurney (1927). 
Key to species of Kensakia 
Kensakia acuticaudata (Thompson & Scott, 1903) has not been included in this key due to lack of data 
on male characters. 
1 Numerous dorsal sensilla on cephalosome (>200). Distal 
coupling denticle on segment 4 of male antennule relatively 
large (10-15 pm). Kensakia shimodensis Harris & Iwasaki, 2009 
- Dorsal sensilla not numerous (< 50). Distal coupling denticle 
on segment 4 of male antennule small (5 pm) . 2 
2 Male P5 curved, not trapezoid. Male rostrum U-shaped in 
ventral view. Ventrolateral band on cephalosome not net-like 
. Kensakia parva Harris & Iwasaki, 2009 
- Male P5 trapezoid. Male rostrum V or Y-shaped in ventral view. 
Ventrolateral band on cephalosome net-like. 3 
3 Female maximum length <0.65 mm. Female cephalosome 
width/rostrum ratio <4.2. Labrum with pad of minute setules + 
four lateral striations. Female carries eight eggs. (Plate ID. Kensakia australis sp. nov. 
- Female maximum length >0.75 mm. Female cephalosome 
width/ rostrum ratio >4.5. Labrum without pad of fine setules 
or striations. Female carries 16-18 eggs. (Plate 2F) . Kensakia acuta (Kim & Kim, 1997) 
