COCCONEJS DIATOMS INFECTED ON WHALESIN THE ANTARCTIC
TAKAHISA NEMOTO
Diatoms infected on the whales have been studied by Hart (1935), Kalcher (1940), Hustedt (1952) and Nemoto (1956), and many interesting
diatom specimens are found on the skin films of whales by their works.
Among them, Cocconeis ceticola, which is first described by Nelson in
Bennett's paper (1920) is the most dominant species on whales, but it has
never been found as the plankton or on any other host than whales.
The next real parasitic Cocconeis, C. Wheeleri is described by Hart(1935), but Okuno (1954) considers it may be a variety of C. ceticola.
Above two-mentional forms and a new variety of C. ceticola, C. ceticola
f. constrica described in the previous report (N emoto, 1956) from sperm
whales in the North Pacific are also observed among the collections fromthe Antarctic whales.
The study on the samples collected by the Japanese Antarctic whaling expeditions reveals that some characteristic forms of Cocconeis arefound besides three above forms. Some of new Cocconeis forms seemto transform their types according to their host species or parasitic
positions of whales. Diatom samples treated here are collected by theJapanese whaling expeditions from various species of whales and preserved in formalin sea water.
The preparations and the method of this examination are the sameas those in the previous report (Nemoto, 1956), but Hyrax is mainly
used in this study as a mounting medium. The phase-microscope is mainly
used for the preexamination of species before electron-micrograph studies.
NOTE ON SPECIES

Cocconeis ceticola Nelson
C. ceticola is the most dominant diatom on whales as it has been
considered up to this time. The typical form is mostly found on finwhales, sei whales and blue whales, while I have never found any
typical specimens of C. ceticola on sperm whales as in th~ case of northern sperm whales. Cocconeis specimens found on sperm whales are
all constricted forms except some vague ones.
Cocconeis ceticola form. constricta NemotoThis variety form of C. ceticola is mainly found on sperm whales asin the North Pacific. But some specimens found on humpback whales
185

186

T. NEMOTO

bear such constricted valves as those of C. ceticola f. constricta. These
constricted forms, however, have wider girdles than typical C. cetfoola
f. constricta.
Cocconeis ceticola form. subconstricta form. nov.
Cells are solitary, forming patches on the skins of blue whales. Valves
are rather broadly oval and constricted at only one side of the valve
where the stauros of rache valve reaches. The surface structures andsizes of valves are the same as the original form of C. ceticola.
This form is found only on blue whales caught in the Antarctic
waters among C. ceticola, and is considered one of the intermediate
forms between C. ceticola form constricta and the original form of C.
ceticola.

cCocconeis Wheeleri Hart, x 1000. A, rache valve.
C, D, girdle views of C. Wheeleri.

Fig. 1.

AD

B, racheless valve.

B

Fig. '.2. A, B, C, Cocconeis ceticola collected from humpback whales. xlOOO. D, E, F,Cocconeis ceticola fo. svhconstricta n. fo. x 1000. Notice the broader girdles of valves
illustrated in C figure. Arrowes show the constricted position of the valves.

Cocconeis Wheeleri HartHart (1935) describes this characteristic diatom only from Antarctic
humpback whales, and I also observe it mainly on humpback whales. Many
specimens collected from tail flukes of humpback whales are almost all
Wheeleri type, and on the other hand ceticola type specimens are verysmall in number on humpback whales. (Fig. 2. A. B. C.)
The most characteristic distinctions between two above forms may be
the curvature of valves and width of girdles' portion. Other distinction,

COCCONEIS DIATOMS ON WHALES

187

such as the size of valves is not clear enough to divide two forms asdescribed in Okuno's report. The sizes of valves of Wheeleri are ratherlarger than C. ceticola as described by Hart (1935). But the largest C.
ceticola is also as large as C. Wheeleri (Okuno, 1954).
In the previous paper (Nemoto, 1956) I considered C. Wkeeleri might
be one variation of C. ceticola as described in Okuno's report, because nospecimens of C. Wkeeleri was found on other baleen whales than humpback whales, and popular C. ceticola was also not observed on humpbackwhales. It suggests that C. ceticola transformed its shapes when it attached to humpback whales. However, I have not been able to derive
any valid reason for above transformation of Cocconeis specimens after
such consideration, and samples collected from a blue whale in the Antarctic are also all Wheeleri types. So I describe here C. Wheeleri again
as a form different from C. ceticola after the description by Hart. Some
discussion on this point is stated in the following chapter.
DISCUSSION

The original type of Cocconeis ceticola is reported by Nelson in Bennett's paper (1920). After their descriptions and successive investigations by Hart (1935), Hendey (1937), Okuno (1954) and Nemoto (1956),
all typical forms of C. ceticola are elliptic-lanceolate in the outlines.
This typical form of C. ceticola is mostly collected from fin whales.
Cocconeis diatoms collected from fin whales are all this ceticola type.
On the contrary, the constricted form C. ceticola f. constricta is only
found on sperm whales as in the northern Pacific (Nemoto, 1956). The
outline of the constricted form is broadly oval and constricted at themedian margin of the valve and it is considered that the constricted
form is one of the transformations of C. ceticola on sperm whales, andthe constricted form has never been found on fin whales.
Ceticola form is also found on sei and blue whales, but ceticola form
is rarely found on humpback whales, while, C. Wheeleri is only foundon humpback whales. Cocconeis Wheeleri, reported by Hart from theAntarctic humpback whales, has never been found on the species ofwhales but a blue whale. C. Wheeleri resembles closely C. ceticola
but has much greater width of the girdle and stronger curvature of thevalves as described by Hart (1935). The sizes of valves are also larger
than those of C. ceticola. But in opposition to Hart's description, Okuno(1954) considers C. Wkeeleri may be a synonym of C. ceticola, because
sizes and structures of valves of C. Wheeleri do not differ so markedly
as C. Wkeeleri is separated from C. ceticola.
I also considered that C. Wheeleri might be a fixed variety form of

T.NEMOTO

188

c. ceticola in my previous report, because C. Wheeleri is found only on
humpback whales and few ceticola type is found on humpback. It suggests that C. cetico'la, which is very common on other whales, is transformed by any causes of humpback whales' skins when it attached tothe whales. But the further observations after above suggestion, reveals
that, though C. ceticola has many variety forms, it is best to consider

D0BJue whale

EHumpback whale

Fin & Sei whale

N
Sperm whale
Fig. 3. A, B, C, Cocconeis ceticola Hart collected from fin and sei whales. D, C. ceticola f. subconstricta collected from a blue whale. E, C. ceticola collected from thesame blue whale. F, G, H, C. ceticola & ceticola f constricta collected from humpback whales. I, J, C. Wheeleri collected from humpback whales. K, L. Ambiguous
C. ceticola collected from sperm whales. M, N, 0, C. ceticola f. constricta collectedfrom sperm whales.

C. Wheeleri is the fixed species on humpback whales though it is possiblethat further information on structures, etc., may cause me to revise mypresent opinion. These variety forms and Cocconeis Wheeleri are listed
in figure 3. As shown in figures, various forms of Cocconeis ceticola
are found on each whale. Especially, it is an interesting fact that theoutlines of valves differ in each whale species as partly described inabove descriptions. The types A, B and C are collected from fin andsei whales in the North Pacific and the Antarctic. They are all typical
ceticola forms, and these host whales are mostly related to each other.

COCCONEIS DIATOMS ON WHALES189

The next figures D and E are found on a blue whale caught in theAntarctic waters. The characteristic point of the former specimens isa constriction on only one side of the valves. This constriction is usuallyfound on the marginal position where the stauros of rache valves reaches
alike constricta form which has two constrictions on both sides. The
latter oval form is found on the same blue whale and it closely resembles
some specimens collected on humpback whales. This oval form is not
the typical elliptic lanceolate ceticola form, and this type is also observed on sperm whales as shown in K illustration. The oval form isconsidered as the first transformation of C. ceticola on other whales than
fin whales.
F illustration is collected among the ventral grooves of humpback
whales in the Antarctic. The next G illustration is collected from thesame whales. The following figures, H, I and J illustrations are obtained
also from humpback whales. But, these specimens are collected fromthe tail flukes of humpback whales. The latter two specimens are apparently Wheeleri types. Cocconeis Wheeleri has been found only on
humpback whales by Hart (1935) and also by my examinations on Japanese collections in 1954 and 1957, but in 1958 I found C. wheeleri on ablue whale in the Antarctic. The typical Wheeleri specimens are mostly
collected from the tail flukes of humpback whales. On the contrary tothis fact, there is no dominant patch of typical Wheeleri among theventral groove specimens in 1957. And the ventral groove specimens
are almost all rather small oval forms or sometimes constricted form
like C. ceticola f. constricta. This phenomenon suggests that, though
the materials are few in number, the parasitic positions on whales may
have some effect to the transformation of the form of C. ceticola or
the related forms.
From the girdle view of above Cocconeis specimens, some interesting
features are also observed. The subconstricted form, D and E illustra·tions have narrow girdles as ceticola form shown in figure 2. Butoval and constricted form collected from humpback whales among ventral grooves have the wider girdles like Wheeleri, though they neverbear the stronger curvature of valves such as Wheeleri. So from thegirdle view, it resembles C. Wheeleri more than C. ceticola. The microstructure of the girdles of the specimens is now under close examinationand it will be discussed in the next report.
The deformation of C. ceticola on sperm whales is also very characteristic. In the lower series, these typical variety forms on sperm whales
are illustrated. K illustration shows the first deformation, which ismostly related to the original type and mostly related to Karcher's
photographs in 1940. L illustration is as large as C. Wheeleri, but this190 'T.NEMOTO

specimen bears slight curvature of valves like that of ceticola form. M,
N and 0 illustrations are all constricted forms, though some differences
are observed among these forms. M specimen is large and the constricted positions are not situated at the median portions of outlines. N
specimen is generally of moderate size, and rather slender than otherconstricta forms. This type is also shown in figures 11 and 12 in plate
II. The constriction of the type is not sometimes so distinct as oval
constricta form. 0 illustration is the most typical constricta forms, andno typical difference is observed in surface structures, from the constricted forms of C. ceticola f. constricta from humpback whales but thesizes of valves.
SUMMARYCocconeis diatoms infected on the Antarctic whales are examined. Cocconeis ceticola is mostly common on fin, sei and blue whales, but it isfound on humpback and sperm whales in rare cases. Cocconeis Wheeleri
Hart is the dominant species on humpback whales and Cocconeis ceticola
f. constricta Nemoto is the dominant species on sperm whales.
One new form, a variety form of C. ceticola, Cocconeis ceticola f. subconstricta is described from blue whales in the Antarctic.
Some specific differences among host whales, and transformations ofCocconeis diatoms are suggested.
REFERENCES
BENNET, A. G, (1920). On the occurrences of diatoms of the skin of whales (with an ap·
pendix by Nelson, E. W.). Proc. Roy. Soc. london, 91: 352-7.
HART. T. J. (1935). On the diatoms of the skin film of whales and their possible bearing
on problems of whales movements. Discovery Rep., 10: 249-82.
HUSTEDT, F. (1952). Diatomeen aus der Lebensgemeinshaft des Buckelwals (Megaptera
nodosa Bonn.). Arch. Hydrobiol., 46: 286-98.
KALCHER, F. H. (1940). Uber den Algenbewuchs auf Siidlichen Walen. Zeitschr. Fisch.
Hilfwiss. Beih., 1: 13-36.
NEMOTO, T. (1956). On the diatoms of the skin film of whales in the Northern Pacific.
Sci. Rep. Whales Res. Inst., no. 11: 97-132.
OKUNO, H. (1954). Electron microscopical study on Antarctic diatoms (6) Observation on
C. ceticola forming "Diatom film" on whales skin. J. Jap. Bot., 29 (9) : 271-7.

EXPLANATION OF PLATESAll photomicrographs have been taken by electronmicroscope. The materials are boiled
with hydro-chloric acid to remove the organic contents before the photographing.
PLATE I
Fig. 1. Rache valve of Cocconeis ceticola f. constricta Nemoto collected from a sperm
whale in the Antarctic. x 4000.

COCCONEIS DIATOMS ON WHALES

191

Fig. 2. Rache valve of Cocconeis ceticola collected from a humpback whale in the Antarctic. x 4000.
Fig. 3. Racheless valve of Cocconeis ceticola f. subconstricta n. fo. collected from a blue
whale in the Antarctic. x 4000.

PLATE II
Figs. 1 & 2. Cocconeis ceticola f. subconstricta n. fo. collected from a blue whale in theAntartic.
Figs. 3 & 4. Cocconeis ceticola f. constricta collected from a humpback whale in the Antarctic.
Figs. 5. & 6. Cocconeis ceticola collected from a humpback whale in the Antarctic.
Figs. 7-9. Cocconeis Wheeleri Hart collected from humpback whales in the Antarctic.
Fig. 10. Ambiguous Cocconeis ceticola Nelson collected from a sperm whale in the Antarctic.
Figs. 11-15. Various forms of Cocconeis ceticola f. constricta Nemoto collected from sperm
whales in the Antarctic.
All photographes show 1,000 magnifications.

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