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Page 12 THE FESTIVUS Vol. XXXIX: Supplement
Clipperton, the species with red to orange coloration is
distinct from both C. squamuligera and C. buddiana
from the Golfo de California and the continental coast of
west America. I consider these specimens from
Clipperton to be Chama rubropicta and it is here
reinstated as a valid species.
The bivalve fauna is dominated by species that attach
to hard substrata or are boring therein. There is a
notable lack of infaunal bivalves which constitute the
majority of species in most marine environments. The
total of 36 bivalve species found at Clipperton are
reflective of the particular substrata encountered. The
two infaunal species in Lucinidae were recovered from
the lagoon as empty shells; they are remains of species
that thrived at a time when the lagoon was open to the
ocean and fully marine as opposed to the brackish
condition encountered today. Records of Rochefortina
sandwichensis (Smith, 1885) and Streptopinna saccata
(Linnaeus, 1758), in conjunction with Codakia punctata
(Linnaeus, 1758) show a biogeographic connection with
the Indo-Pacific islands. The majority of the 28
identified bivalve species are from the Panamic
Province.
The seven identified species of Vetigastropoda show
mostly Panamic affinity with the exception of Diodora
granifera (Pease, 1861) chiefly known from Hawaii.
The most diverse group within Vetigastropoda is
Trochoidea with approximately 3,000 species worldwide
(Geiger & Thacker, unpublished data) though only five
species have been recorded from Clipperton. Compared
to the four species of Fissurellidae (606 worldwide:
Geiger et al., in press) and four nominal taxa in
Scissurellidae (170 worldwide: Geiger et al., in press)
the low diversity of Trochoidea is remarkable. There
seems to be an inverse proportional relationship between
diversity and body size. The overall body-size sequence
is from the smallest Scissurellidae to the intermediatesized
Fissurellidae to the rather large Trochoidea.
Among Trochoidea the species found at Clipperton are
rather small in size for the group.
Only two species of Neritoidea have been collected at
Clipperton (Neritidae, Plate 12, figures 1a-b;
Phenacolepadidae, Plate 12, figures 2a-c). Species in
this group occur mostly in the high intertidal and
dysaerobic environments. The intertidal of Clipperton is
essentially non-existent, with strong wave action
hampering the colonization of the substratum by
epifaunal species. This explains the low number of
species in this low-diversity group.
The Caenogastropoda, to the exclusion of
Neogastropoda, comprise 114 species. Four intertidal
Figure 21. Two Melanella dufresnei parasitizing a sea cucumber.
This species of holothurian is the most common at Clipperton, 1994.
Photo: R.B. Herrmann.
species in Littorinidae have been encountered, half from
the Indo-Pacific fauna, half from the Panamic fauna. A
rich assembly of microshells were collected
predominantly on the underside of rocks, and as empty
shells. Species in the Epitoniidae (Plate 18) and
Eulimidae (Plates 19, 20) are parasites on sea anemones
and echinoderms, respectively (Plate 43, figure 6),
(Figure 21). In most, the host-parasite relationship has
not been documented, which makes identification more
difficult. The species diversity of Eulimidae is
surprisingly high. Infaunal species are rare, with two of
the four Naticidae (Plate 23) only tentatively assigned to
that family. The diversity of Cypraeidae (Plates 24, 25)
is high, most likely owing to their long dispersal
capability as teleoplanktic, planktotrophic veliger larvae.
Most Clipperton Cypraeidae seem not to have
established populations because their records stem from
empty shells. Of the 51 caenogastropod species
identified to species level (excluding the holoplanktonic
families), 29 are members of the Indo-Pacific
malacofauna, 21 are Panamic and 1 western Atlantic.
Species in the Janthinidae, Atlantidae, Carinariidae
and Pterotrachaeidae among the Caenogastropoda and
Pteropoda (Cavoliniidae and Limacinidae) among the
Opisthobranchia, have a holoplanktonic life style. They
all have broad geographic distributions, hence their
records do not assist in determining the faunal affinity
of Clipperton.
The 61 Neogastropoda represent the predator guild
of the marine fauna. The Muricidae (Plates 28, 29) is
the second most diverse faunal element and contributes
some of the largest-shelled species collected.
Coralliophilinae (Plates 30, 31) are specialized
consumers of live coral tissue, and are particularly