BULLETIN OF MARINE SCIENCE, 61(2): 377–385, 1997
GRAY WHALE BARNACLES CRYPTOLEPAS RHACHIANECTI
INFEST WHITE WHALES, DELPHINAPTERUS LEUCAS,
HOUSED IN SAN DIEGO BAY
Sam H. Ridgway, Elek Lindner, Kerry A. Mahoney and
William A. Newman
ABSTRACT
A whale barnacle, Cryptolepas rhachianecti (Dall), previously considered an obligate
commensal for the gray whale, Eschrichtius robustus (Lilljeborg), infested white whales,
Delphinapterus leucas (Pallas), housed in San Diego Bay. The infestation occurred annually between January and April in concert with the northward migration of the gray
whale, and did not occur during years when the white whales were housed elsewhere
during these months. Although initial infestation elicited no apparent skin response,
after successive years of exposure, massive cellular proliferation in the adjacent epidermis resulted in ejection of barnacles from the whales within a few weeks. This increasing
epidermal response and the invasion of inflammatory cells at the juncture of skin and
barnacle shell is suggestive of an immune reaction to the barnacles.
Barnacles are marine crustaceans that attach to a variety of inanimate and animate
objects including the skin of whales. Although whale barnacles are often referred to as
parasites, they strain food from the sea and, other than to increase drag, are generally
thought not to adversely affect their cetacean hosts (Slijper, 1962). The life cycle of a
barnacle begins with a series of six free-swimming planktonic stages progressing to a
molt into a cyprid which seeks a place for permanent settlement. In the case of Cryptolepas
rhachianecti (Dall), the site of attachment is the skin of the gray whale, Eschrichtius
robustus (Lilljeborg), for which it is generally considered to be host-specific (Newman
and Ross, 1976; Newman and Abbott, 1980; Wolman, 1985; Scarff, 1986). Observations
of C. rhachianecti suggest that they spawn on the whales’ winter grounds following the
southern breeding migration. No small (newly attached) barnacles are found on southbound whales as they pass by San Francisco; however, all northbound whales carry numerous small barnacles (Rice and Wolman, 1971). Therefore, attachment must occur in
the warmer waters of the breeding grounds and/or during their return north. Although
other barnacles are found on other whale species, there are no published reports of barnacles occurring on beluga or white whales, Delphinapterus leucas, (Pallas).
MATERIALS AND METHODS
At various times between 1977 and 1980, two male and two female white whales taken
off Churchill, Canada, were brought to live in netted ocean enclosures at the mouth of San
Diego Bay (Fig. 1) at the Naval Command Control and Ocean Surveillance System
(NCCOSC), RDT&E DIV. The males were identified as NOC and CHU; the females as
MUK and RUB. Over the next 8 yrs, some were also kept in land-based pools in San
Diego, and/or in netted ocean enclosures in Kaneohe Bay, Hawaii; Puget Sound, Washington; or Vancouver Island, Canada (Table 1).
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Figure 1. Three of the four white whales (Delphinapterus leucas) in this study: left to right, MUK,
NOC, RUB in the bay pen complex. The entrance to San Diego Bay is about 1 km away in the upper
right of this photograph.
The water for the land-based pools in San Diego was collected from the Pacific Ocean
at a depth of about 20 m and pumped through sand and gravel filters into the pool at a rate
sufficient to allow for complete water exchange every 2-4 h.
For laboratory examination, excised barnacles were fixed in 70% alcohol. Under a
dissecting microscope, the whale epidermis was removed from the barnacle so that it
could be identified. Portions of proliferated epidermis containing barnacles were decalcified, processed for histology, and sectioned on a microtome prior to mounting on a
glass slide for staining with hematoxylin-eosin.
RESULTS
In late January, and early February 1978, trainers noticed small dark specks on the skin
of the whales. By late February they had grown to about 1 mm in diameter, and appeared
over much of the whales’ body surface. By March cirral-like appendages, were seen
protruding from many of the black spots. A few of these dark areas were excised to reveal
barnacles with a calcareous shell.
Despite the absence of overt signs of inflammation, purulence, or discomfort manifested by the whales, we eliminated most of the barnacles from the whales’ skin by apply-
RIDGWAY ET AL.: GRAY WHALE BARNACLES ON WHITE WHALES
379
Table 1. Location of white whales, NOC, MUK, CHU, and RUB, 1977-1995, and incidences of
barnacle infestations.
Animal Date
NOC
8/1977
12/1977
1979
04/30/79
10/1980
1981
3/1982
11/1982
1983
4/1984
1985
1986
1987 to 1995
Location
Canada to SD pool
Open water SD
Open water SD
San Clemente Is., CA
Wash. and Canada
Wash. and Canada
Open water SD
Hawaii
Hawaii
Open water SD
Open water SD
Open water SD
Open water SD
CHU
8/1977
12/1977
1979
5/1980
5/1981
3/1982
1983
10/1984
2/1985
Canada to SD pool
Open water SD
Open water SD
SD pool
Hawaii
Hawaii
Hawaii
Open water SD
Open water SD
No barnacles
Barnacles 1/78
Reinfested, no skin response noted
No barnacles
No barnacles
No barnacles
No barnacles
No barnacles
Reinfested, no skin response noted
(5/95 died)
MUK
8/1977
12/1977
1979
04/30/79
10/1980
1981
3/1982
1983
1984
1985 to 1995
Canada to SD pool
Open water SD
Open water SD
San Clemente Is., CA
Wash. and Canada
Wash. and Canada
Open water SD
Open water SD
Open water SD
Open water SD
No barnacles
Barnacles 1/78
Reinfested, no skin response noted
7/1980
10/80
1982
1983
1984
1985 to 1995
Canada to SD pool
Open water SD
Open water SD
Open water SD
Open water SD
Open water SD
RUB
Barnacles
No barnacles
Barnacles 1/78
Reinfested, no skin response noted
No barnacles
No barnacles
Reinfested, no skin response noted
No barnacles
No barnacles
No barnacles
Reinfested, no skin response noted
Reinfested, marked skin response
Reinfested each Jan/Mar, marked skin
response
No barnacles
No barnacles
Reinfested, no skin response noted
Reinfested, no skin response noted
Reinfested, no skin response noted
Reinfested each Jan/Mar, marked skin
response
No barnacles
Barnacles 1/81
Reinfested, no skin response noted
Reinfested, no skin response noted
Reinfested, no skin response noted
Reinfested each Jan/Mar, marked skin
response
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Figure 2. A. Exterior view of shells of three different size barnacles are shown in the upper series.
Below these barnacles three comparable ones are displayed with wall plates separated. B. Side
views of the shells of two immature barnacles. C. High-magnification basal view of one wall plate
cusp showing the complex lace-like pattern by which the shell anchors to the whale skin. D. Highmagnification of the exterior of a wall plate cusp showing the complex arrangement for anchoring
to the skin of the whale.
ing an ointment containing zinc oxide and copper sulfate. This treatment rapidly stopped
cirral movement and killed the barnacle. Treatment was withheld from a few of the
barnacles to allow them to grow to a size that would enable us to confirm their identity.
In March 1978, a specimen with a 3 mm high and 3 mm diameter shell was removed for
examination. The slightly conical shell had no vertical ridges on either of the six compartments and had no calcareous basis, but it was clearly a balanomorph or sessile barnacle. Because the specimen was immature, it lacked some of the characteristics of the
coronuline barnacle, Cryptolepas; however, it was tentatively identified as such. For
more positive identification, a few barnacles were allowed to grow; periodically some of
these specimens were removed for examination. Growth rates of the attached barnacles
RIDGWAY ET AL.: GRAY WHALE BARNACLES ON WHITE WHALES
381
Figure 3. A. Ventral body skin of RUB showing barnacles of various sizes from about 2 to 20 mm
in diameter. The photograph was taken in early June 1981 during RUB’s first year in San Diego
Bay. Small scratches, creases, or depressions in the whale skin appeared to be favorite attachment
points for barnacles. B. Photograph taken in March 1985 showing the massive skin proliferation
around a barnacle. C. Photograph showing a pit remaining in the epidermis after the barnacle was
ejected. In most cases, pits filled in and the skin was smooth within about 6 wks.
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Figure 4a. A. 40 X photomicrograph of a section through whale skin with embedded barnacle. B.
Enlargement (250X) of the area of i and s indicated on A. C. Enlargement (250X) of an area
between i-s and b indicated on A.
appeared to be in the range of 3 to 4 mm per month. The complexity of the shell (Fig. 2)
could be one explanation for the relatively slow growth rate (Hirano and Okushi, 1952).
Two more specimens, one 16 mm and one 20 mm were collected from MUK and RUB
during the month of June. Although a mature C. rhachianecti may reach 55 mm in diameter, these barnacles were sufficiently large to positively identify them as Cryptolepas
rhachianecti (Dall).
MUK, NOC, and CHU acquired their first barnacle infestations in 1978; RUB was first
infested in 1981. During these initial infestations there was no apparent skin response
(Fig. 3A); however, with several successive years of exposure, a marked response developed (Fig. 3B). Infestation did not occur during the years when these whales were kept at
other locations during the months of January, February, or March - even if the whale was
returned to San Diego after these months. In whales that spent successive years in San
RIDGWAY ET AL.: GRAY WHALE BARNACLES ON WHITE WHALES
383
Figure 4b. D. 500 X photomicrograph of a section through whale skin with embedded barnacle: b,
barnacle tissue; i, layer of inflammatory cells; e, whale epidermis proliferated around barnacle; s,
barnacle shell.
Diego Bay and were likewise infested, a marked response of the epidermis adjacent to the
barnacles was noted which caused the barnacles to be ejected within several weeks of
attachment (Fig. 3C). Microscopic examination of stained sections of portions of skin
with attached barnacles revealed that there was a massive proliferation of epidermis surrounding the barnacle. Micro-abscesses developed at the juncture between the barnacle
shell and the epidermis. Within these micro-abscesses were numerous white blood cells
including neutrophils, eosinophils, and lymphocytes (Fig. 4). No scarring was observed
on the skin of the whales after shedding the barnacles. This was surprising because when
barnacles are removed or shed from E. robustus or Megaptera novaeangliae (Borowski),
the remaining pit eventually becomes a tissue scar (Wolman, 1985; Geraci and St. Aubin,
1987).
DISCUSSION
Whenever white whales were kept in San Diego Bay during the season of the northward migration of the gray whales past San Diego Bay, barnacles appeared on their skin.
When whales were in land-based pools in San Diego, or in bay enclosures in Hawaii or in
open ocean enclosures in the Pacific Northwest, their skin remained clear of barnacles.
Whales kept in the land-based pools in San Diego during the northward migration of
gray whales were not infested by barnacles despite the fact that the pools were filled with
sea water pumped from an area closer to the path of the migrating gray whales than the
enclosures in the bay. This water source is in a mixed layer during the late fall and winter
(Dayton et al., 1992) and passes through sand and gravel filters before it enters the whale
pools. It is possible that filtration removed any barnacle larvae that may have been in this
water, thus preventing infestation of the whales in the land-based pool.
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The southward migration of gray whales passes San Diego as early as the end of November; however, we never saw any sign of barnacles until the middle to end of January,
after the northward migration had begun. Of course, some gray whales are still migrating
south in January and we cannot be certain that all infestations were from northward migrating whales. However, the observations of Rice and Wolman (1971), mentioned earlier, suggest that infestation by southward migrating gray whales is unlikely.
Because white whales do a good deal of rubbing and scratching on one another and
objects within their enclosures, it is difficult to tell whether or not barnacle infestation
causes irritation. We have not noticed quantifiable signs that the barnacles cause skin
irritation to the whale. We question if there might be some secretion from the barnacle
that may have an anesthetic effect on whale skin, for it is known that barnacles may
influence the growth of surrounding tissue when established on other animals (Anderson,
1994).
It is interesting that no barnacles were ever found on any of the numerous bottlenose
dolphins, Tursiops truncatus (Montagu), that occupied San Diego Bay alongside the white
whales. Perhaps physiological or anatomical differences in the skin covering of the two
species (Brown et al., 1983; Hicks et al., 1985; St. Aubin et al., 1990; Shoemaker and
Ridgway, 1991) explain the barnacles’ selective affinity for, or ability to, infest white
whales.
The proliferation of skin and the invasion of inflammatory cells at the juncture between
skin and barnacle shell suggests that with successive exposure over a period of 3-4 yrs, an
immunity developed in response to the barnacle. We have not looked for barnacle antibodies in whales; however, this should be the next step in defining the proliferative skin
response we observed.
In their summer feeding areas off Alaska and Siberia, gray whales are sympatric with
white whales, yet barnacle infestations have never been reported in white whales in the
North Pacific. Atlantic gray whales probably became extinct at least two centuries ago.
Likely, the Atlantic gray whales were coastal migrators and may well have been sympatric with the Hudson Bay populations (Reeves and Mitchell, 1988) from which our animals were taken at Churchill, Canada. It seems reasonable to question whether the North
Pacific white whales are already sensitized, or more easily sensitized to the barnacle, than
our North Atlantic white whales. In view of the aforementioned observations of Rice and
Wolman (1971), however, it appears more likely that C. rhachianecti do not produce
larvae in the cooler northern waters that their gray whale hosts share with white whales.
ACKNOWLEDGMENTS
We thank C. Bowers and D. Ewing for help in the initial discovery of barnacles on the white
whales, M. Reddy for help with manuscript preparation, and R. Tarpley for taking the photomicrographs. The whales were collected in 1977 and 1980 under Canadian and U.S. federal permits.
Since collection, the whales have been maintained in accordance with regulations promulgated
under the Animal Welfare Act and Marine Mammal Protection Act.
RIDGWAY ET AL.: GRAY WHALE BARNACLES ON WHITE WHALES
385
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DATE ACCEPTED: September 25, 1995
ADDRESSES: (S. H. R. and E. L.) Naval Command, Control, and Ocean Surveillance Center, RDTE
DIV D3503, San Diego, CA 92152-6266; (K. A. M.) Office of the San Diego County Veterinarian,
5555 Overland Ave., Bldg. 4, M.S. 0525 San Diego, CA 92123; (W. A. N.) Scripps Institution of
Oceanography, La Jolla, CA 92093-0202.