Zootaxa, Taxonomy of Serpulidae (Annelida ... - Magnolia Press

large crystals in the structure of the tube, while small, disorderly arranged crystals give an opaque appearance.
Most recently, Vinn et al. (2008) described up to four different layers found in 34% of serpulid tubes, based on
SEM and they also found a positive correlation between regular crystal orientation and tube transparency.
Aggregated tubes. Serpulids like Salmacina, Filograna, and Filogranella build characteristic open
aggregates made of numerous tiny branching tubes (Fig. 1B). Nishi (1992c) illustrated that the “colonies” are
the result of combination of asexual budding and gregarious larval settling. Asexual reproduction also leads to
a chain of tubes in Filogranula (cf. ten Hove 1979: 286) or a network of branching tubes in Josephella
marenzelleri and Rhodopsis pusilla (see George 1974, Ben-Eliahu & ten Hove 1989, Nishi 1992c, Nishi &
Yamasu 1992). Asexual reproduction also has been reported for Spiraserpula (Pillai & ten Hove 1994 fig.
16B). These “colonies” are different from dense aggregations such as found in Galeolaria caespitosa (Fig.
2D), Ficopomatus enigmaticus or some or some Hydroides spp. resulting from gregarious larval settling only.
For a review of serpulid “colonies” see ten Hove & van den Hurk (1993).
Tube colour. Serpulid tube colour is most commonly white, however in some species completely or
partly pink, bluish, orange (e.g., Spirobranchus, Serpula and one Hydroides), or purple (Fig. 2B), as well as
mustard (both Spiraserpula), or even white with dark-brown cross-striation as in Serpula vittata (as S.
palauense Imajima, 1982 fig. 2m; Fig. 1C). Sometimes inner tube parts can be coloured as in tropical
Spirobranchus spp. (ten Hove 1970, Smith 1985, Fig. 2C). In individual tubes of small Serpula spp. colour
can change from pink to white in a few millimeters near the entrance of the tube (ten Hove unpublished).
The general morphology of the body
Serpulids (and sabellids) have a body that is clearly divided into three regions: branchial crown, thorax, and
abdomen (Fig. 5A–D). The branchial crown is composed of a number of radioles each bearing a double row
of ciliated pinnules. One of the radioles is usually transformed into the opercular peduncle (Fig. 5C, D, pd)
and distally bears the operculum (Fig. 5B–C, op). The base of the branchial crown is surrounded by the collar,
which continues as the thoracic membranes, a structure found only in serpulids. The border between thorax
and abdomen is marked by chaetal inversion, with the dorsal notochaetae and ventral comb-shaped
neurochaetae (uncini) of the thorax changing places such that abdominal uncini become dorsal (notopodial)
and abdominal chaetae become ventral (neuropodial) in the abdomen.
Although serpulids are often very brightly coloured and the colour of the animals indeed may be useful in
the field (Fig. 1), as a taxonomic character the type of colouration is of little use as colour is rapidly lost in
preservatives, particularly in alcohol. The colouration may also be a subject to significant interspecific
variability (e.g., in the Spirobranchus corniculatus complex: Fosså & Nilsen 2000: 140, 147; Song 2006, as S.
giganteus). It may even vary within a single specimen, for instance, in Spirobranchus the colour of both lobes
of a branchial crown may be so different as blue and red (ten Hove unpubl.). Føyn & Gjøen (1953) describe a
Mendelian pattern found in the colouration of branchial crowns of Pomatoceros triqueter, with 2628 brown,
218 blue, and only 2 orange branchial crowns.
The branchial crown
The branchial crown, used for feeding and respiration, with each radiole bearing rows of paired ciliated
pinnules is a distinct feature of sabellids and serpulids. The crown is considered to be prostomial (cf. Segrove
1941). The radioles of the branchial crown are attached to paired lobes (Fig. 6F, bl) located laterally on both
sides of the mouth. The branchial lobes are completely separate from one another in serpulids, but are fused
together in some sabellids (e.g., Chone Bush, 1905 and Sabella Linnaeus, 1767, see Fitzhugh (1989)).
The number of radioles used to delineate some taxa (e.g., Salmacina tribranchiata) is an unreliable
character. In individual species, the lower limit of the number of radioles has no value, since all juveniles have
TAXONOMY OF SERPULIDS: STATE OF AFFAIRS
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