A Review of the Genus Eunice - Smithsonian Institution Libraries

NUMBER 523 15
be longer than the other teeth (compare Figures 13a, 5h, and
9c). All teeth may be wide and abruptly tapering distally
(Figure 21c) or evenly tapering from the bases (Figure 5h). The
number of pectinate setae usually increases from anterior to
posterior setigers; in some species, pectinate setae appear to be
absent in the first 15-20 setigers.
Compound falcigers are usually distinctly narrower than
aciculae or subacicular hooks, but in some species they are as
thick as the latter. Falcigers are composed of shafts and
appendages. The shaft is usually slender, but often expanded
distally to a distinct head (compare Figures 23a and 4e). Shaft
heads may be marginally dentate or serrated. Shafts are usually
clear, nearly translucent, but may become more strongly
sclerotinized, especially towards the bases, which then become
chestnut, brown, or even black in color (e.g., Eunice sebastiani).
The appendages may be short (about as long as the
distally expanded head of the shafts, Figure 4e) or they may be
distinctly longer, becoming in some instances, very long and
narrow (Figure 8b). The appendages may distinctly taper
towards the tip (Figure 8b) or have nearly to completely parallel
sides (Figure 12f). Distally, they arc usually bi- or, rarely,
tridentate. In bi- and tridentate falcigers (Figures 4e and 5e), the
teeth are in a row, with one above the other. The teeth may be
nearly erect or variably curved and differ in size from barely
noticeable to long and pointed. Reduction in size of the teeth is
most common in the proximal teeth. Distally the appendages
are covered by a pair of guards. The guards usually fit closely
around the appendages, but are very much wider in a few
species. Each guard consists of a convex membrane, which
distally may be rounded or bluntly to sharply pointed (Figures
3b, 4e, 5e). The guards may be equipped with distinct mucros
(Figure 130- Such mucros are mostly present in forms with
bluntly to sharply pointed guards, but may also be present in
forms with rounded guards (Figure 16f,i). The edge facing
away from the teeth may be slightly thickened and the other,
cutting edge may be serrated.
Pseudocompound falcigers (Figure 7h, j,k; Figure 86h,i) have
thick shafts that are barely inflated near the reduced joint. The
joint may be recognizable only as a swelling on one side of the
falciger or be more distinct. The pseudoappendages are short,
with nearly parallel sides and bidentate. Both teeth are directed
distally and tapering.
Shafts of the compound spinigers closely resemble those of
the falcigers (Figure 57c). Appendages (blades) vary in length
and are always knife-edged; the narrower edge may be serrated.
Each neuropodium may be supported by a single acicula;
perhaps most common are paired aciculae, but up to about
seven have been recorded (e.g., Eunice manihine, four in Figure
69e). When multiple aciculae are present, they are arranged in
a dorsoventral row. The aciculae usually are thicker than all
other setae. The number and shape may vary from anterior to
posterior end. Multiple aciculae are more common in anterior
than in posterior setigers. Most species have tapering, distally
bluntly pointed, straight aciculae; some species have distally
hammer-headed or irregularly thickened and truncated aciculae.
In some species, aciculae are distally bifid. Gently curved,
or geniculate aciculae are common. Aciculae from a single
neuropodium may differ in shape.
Subacicular hooks are exclusively present in the neuropodia
and are first present from setigers 15-35 in most species.
Hooks are usually present in all remaining setigers. Hooks
originate near the base of the aciculae, but form a distinct angle
relative to the aciculae (Figure 3e) and emerge along the lower
edge of the neuropodia. Subacicular hooks are usually slightly
thinner than the aciculae and are often somewhat lighter in
color. Most species have a single subacicular hook per
parapodium, but in some species a vertical series of as many as
5 may be present (e.g., Eunice vittata, three in Figure 114e).
Distally, subacicular hooks may be bidentate (Figures 3d and
7c,h), tridentate (Figures 4d, 5c,d) or simple and spine-like
(Figure 103k). In some species the two distal teeth in the
tridentate hooks are arranged in tandem (e.g., E. cirrobranchiata,
Figure 31e; E.flaccida, Figure 46c), but in most cases
the teeth are crested (i.e., with the tips of the teeth in a single
plane parallel to the curvature of the setal axis, e.g., Figures 4d,
5c,d).
Structurally, aciculae and subacicular hooks are similar
when viewed with a light microscope; when any internal
structure is visible, they appear to consist of an inner core of
dense fibers, covered by a non-fibrous sheath. In some species,
the separation between core and sheath is distinct, with a
dark-colored core and a clear, often translucent sheath. In other
species the separation between core and sheath is indistinct.
Aciculae and subacicular hooks may be clear and nearly
colorless, yellow, chestnut colored, various shades of brown,
and in some instances a very distinct jet black. If paired
aciculae are present, they are often of different colors. If paired
subacicular hooks are present, they usually have the same
color, but replacement subacicular hooks that have yet to
emerge are often lighter in color. Aciculae and hooks in anterior
setigers are often lighter in color then those farther back, and
smaller specimens tend to have more light-colored aciculae
than do larger specimens.
Cladistic Analysis
Species of Eunice have for the last 50 years organized into
informal species groups (Hartman, 1944; Fauchald, 1970). A
cladistic analysis was performed to test if these informal groups
represented monophyletic, possibly definable taxa. The analysis
was done using PAUP 2.4 on an IBM PS-2/80 and the
corresponding mainframe version on an IBM 4381.
SELECTION OF OUTGROUP TAXA
This initial analysis was intended to justify selection of
outgroups to be used in this study. A complete analysis of the
order Eunicoidea is beyond the scope of this study. The