THE NAUTILUS 114(1):14-17, 2000
Page 14
A new species of Columhella (Neogastropoda: Columbellidae)
from the Caribbean Neogene
Maria J. deMaintenon
Department of Marine Science
Universitv of Hawaii at Hilo
200 W. Kawili Street
Hilo. HI 96720 USA
deniainte@ha\vaii.edu
ABSTRACT
A new species of CohimbeUa is described from the Neogene
of the southwestern Caribbean and compared widi other Ca-
ribbean CohimhcUa species. The new species is a member of
a species pair diitering primarily in inferred lar^'al ecolog\-. Pro-
toconch morphology suggests that the new species had planktic
development, whereas its extant analogue. Columhella mcrca-
toria (Linnaeus, 1758), has nonplanktic development. Though
tlie 2 species were contemporaneous. the\' do not appear to
have been svmpatric.
Kcif words: Colombia. Costa Rica, lanal ecolog\'. protoconch.
INTRODUCTION
Evolutionary divergence in larval ecology between
planktic and nonplanktic modes i.s a common pattern in
marine molluscs. Many gastropod genera in several fam-
ilies display both reproductive modes. Recent evolution-
arv divergence may result in pairs of .species differing
primariK-in lar\al shell moq^hologx-. Traditionally such
variation was considered as evidence for poecilogony in-
traspecific variation in larval developmental modes. Re-
cent reviews of poecilogony in marine invertebrates
(Hoagland and Robertson, 1988; Bouchet. 1989; Knowl-
ton, 1993; Oli\erio, 1996) however, ha\e found httle ev-
idence to definitiveK' support that poecilogony occurs.
Hoagland and Robertson (I98S) reviewed reported cases
of poecilogon\' in marine gastropods, and concluded that
the pattern of larval development is generalK informa-
Hve in species-level invertebrate swstematics. The pur-
pose of this paper is to describe a new species of col-
umbellid gastropod, CohimhcUa mohiciisis, that differs
from another Caribbean CohimhcUo species in its in-
ferred developmental mode. AdditionalK. the 2 species
appear to be allopatric, lending further support to their
taxonomic distinction.
CohimhcUa Lamarck, 1799 is primariK-a tropical
American taxon, consisting of 15 Neogene and Recent
American species and 2 species in the eastern Atlantic.
Phylogenetic analyses of representative columbellid ta.\a
(deMaintenon. 1999) supports the monoph\K of Col-
umhcUa. based on 8 characters of anatom\-, radular mor-
phology' and shell morpholog)-. Recent species of Col-
iimhcUa are differentiated primarily on the basis of con-
chological characters. The extant species comprise 2
morphological groups, one of which occurs in the Atlan-
tic. The Atlantic CohimhcUa species are very similar, and
are characterized by having shells with spiral cords over
die entire shell surface. The\' differ primariK' in shell
coloration and in the number and strength of spiral
cords. Jung (1994) recently reviewed the fossil species
of the Atlantic group in a discussion of the CohimhcUa
species from the Neogene of the Dominican Republic.
The extant members of the Atlantic group include 2 spe-
cies in the eastern Atlantic and 2 in die western Atlantic.
The known fossil record of the group extends back to
the late Miocene. Of the living and fossil species of Col-
iimhcUa in the Atlantic, the new species is the onK' one
considered to have planktic development.
The second group comprises the 10 extant Panamic
CohimhcUa species. These differ from the Atlantic group
by lacking spiral cords on the shell except as juveniles.
All members of the Pacific group have multiwhorled
protoconchs, and are inferred to have planktic devel-
opment. The fossil record of this group is unk-nown be-
fore the Pliocene, when the extant species appear Al-
lopatric species pairs differing in developmental mode
alread\' have been reported in the group of Atlantic Col-
umhella species. Moolenbeek and Hoenselaar (I99I) dif-
ferentiated 2 species in the eastern Atlantic: CohimhcUa
nistica (Linnaeus. 1758) with nonplanktic development,
in the Mediterranean and eastern Atlantic coast, and
CohimhcUa adansoni (Menke, 1853) with planktic de-
velopment, endemic to the offshore islands of the east-
em Atlantic. Stud\' of alloz\me data from these 2 species
(Oliverio, 1995, 1996) indicates that they thverged about
2 million years ago. The new species described herein
has a similar relationship with one of the western Atlan-
tic species, Columhella mcrcatoria (Linnaeus, 1758).
The following institutional abbrexiations are used: UF,
Universit\' of Florida, Florida Museum of Natural His-
BioStor
