500 
PACIFIC SCIENCE, Vol. XXI, October 1967 
TABLE 1 
Distribution and Habitats of the Plqtosidae* 
SPECIES 
AUSTRALIA 
NEW GUINEA 
HABITAT 
Group A (dendritic organ present) 
1. Cnidoglanis macrocephalus (Yal.) 
+ 
+ 
marine 
2. C. micro ceps (Rich.) 
+ 
— 
marine 
3. C. muelleri (Klunzer) 
+ 
— 
marine 
4. Euristhmus lepturus (Gunther) 
+ 
+ 
marine 
5. E. nudiceps (Gunther) 
+ 
+ 
marine 
6. Oloplotosus mariae Weber 
— 
+ R 
fresh water 
7. Paraplotosus albilabris (Val.) 
+ 
+ 
marine 
8. Plotosus anguillaris (Bloch) 
+ 
+ 
marine 
9- P. canius Ham. Buch. 
— 
+ 
marine 
10. P. papuensis Weber 
— 
+ R 
fresh water 
Group B (no dendritic organ) 
1. Anodontiglanis dahli Rendahl 
+ L 
— 
fresh water 
2. Neosilurus argenteus (Zietz) 
+ S 
— 
fresh water 
3. N. ater ater (Perugia) 
+ E 
+ R 
fresh water 
N. ater sepikensis (Whitley) 
— 
+ G 
fresh water 
4. N. hart on i Regan 
— 
+ R 
fresh water 
5. N. hrevidorsalis (Gunther) 
+ L,J 
+ R 
fresh water 
6. N. equinus (Weber) 
— 
+ R 
fresh water 
7. N. gjellerupi (Weber) 
— 
+ G 
fresh water 
8. N. glencoensis (Rendahl) 
+ L 
— 
fresh water 
9. N. hyrtlii Steindachner 
+ L,J 
— 
fresh water 
10. N. idenburgi (Nichols) 
— 
+ G 
fresh water 
11. N. meraukensis (Weber) 
— 
+ R 
fresh water 
12. N. mortoni Whitley 
+ L 
— 
fresh water 
13. N. novaeguineae niger (Nichols) 
— 
+ G 
fresh water 
N. novaeguineae novaeguineae 
(Weber) 
— 
+ R 
fresh water 
14. N. perugiae (Ogilby) 
— 
+ R 
fresh water 
15. N. rendahli (Whitley) 
+ E 
— 
fresh water 
16. Porochilus obbesi Weber 
+ E 
+ R 
fresh water 
17. Eandanus bostocki Whitley 
+ Gr 
— 
fresh water 
18. T. tandanus Mitchell 
+ M 
— 
fresh water 
* Symbols used: +, present; — , absent; G, Gaimardian fluvifaunula; Gr, Greyian; J, Jardinian; L, Leichhardtian; M, 
Mitchellian; R, Riechian; S, Sturtian. 
(Weber and de Beaufort, 1913). All the spe- 
cies of group B are freshwater inhabitants. 
Examinations carried out on adult and juve- 
nile individuals of Plotosus anguillaris, Cnido- 
glanis macrocephalus, and Eur isthmus leg turns 
showed that the dendritic organ is present and 
equally developed in both sexes, and also that 
it is already conspicuous in juvenile catfish 
ranging in size between 45 and 56 mm. Re- 
cently, van Lennep (unpublished) found that, 
in comparison with adults, the dendritic organ 
of juvenile catfish contains only a relatively 
small number of fully developed glandular 
cells. 
The mean length of nine adult Plotosus 
anguillaris was 322 mm (286-361 mm) total 
length. Since some of the gonads were either 
in a fully mature or in a spent condition, these 
measurements must represent the size of adult 
catfish of this species. Comparable figures have 
been reported by Delsman and Hardenberg 
(1934), 300 mm; Okada (1955), 250 mm; 
and Fowler (1959), 460 mm. A much higher 
figure for maximum size (30 inches) is given 
by Smith (1949), and is quoted by Munro 
(1954) and Fowler (1956), but probably is 
erroneous. 
DISCUSSION 
More than half of the 28 species of Ploto- 
sidae are freshwater inhabitants. This makes 
