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

The inside of the tube, the lumen, is even more underexploited as a character than the outside. The internal
cross-section of the tube lumen in serpulids is mostly circular. However, in species of the genus Spiraserpula
Pillai & ten Hove, 1994, the lumen can also be oval with a “waist”, the cross-section is like a ∞ without the
middle line dividing it in two parts (Fig. 7E). Such a lumen shape is a result of the internal tube structures
(ITS) in the form of ridges and crests that are known only for this genus. There is a single observation of a
Protula species with a dorso-ventrally compressed lumen (Netherlands Antilles, Curaçao, Piscadera Bay, 20
m, reef, 12 Jan. 1990, ten Hove unpublished). Finally, two series of small pits in the substrate-side of the
lumen have been described for Spirobranchus corrugatus (see ten Hove & Nishi 1996).
Tabulae or transverse tube elements (Fig. 7C) may partition the oldest parts of the tube as response to tube
damage in Pyrgopolon, Pomatoceros, Spirobranchus, and Serpula (e.g., Lamarck 1818: 362, McIntosh 1923
fig. 168, Mörch 1863: 349, ten Hove 1973, ten Hove & van den Hurk 1993: 27), and rarely so in Hydroides
(Perkins pers. comm.; Breton & Vincent 1999 fig. 14), as well as in Crucigera, Ficopomatus, Hyalopomatus,
and Neovermilia (present paper).
Attached parts of the tubes are often flattened and may contain alveolar structures as for instance in
Filogranula, Pomatoceros, Semivermilia, and Spirobranchus (e.g., Bianchi 1981 figs 32c, 36a, 42b, 43b;
McIntosh 1923 fig. 169–170; Thomas 1940 Plate 1 figs 2, 3). According to Thomas (1940: 7) it is probable
that alveoles are left to economize the amount of material used.
The ornamentation of the external tube surface of the serpulid tubes is variable within populations and
may be quite elaborate (e.g., Janita fimbriata, see Bianchi 1981 fig. 39), but most typically consists of
longitudinal and transverse elements (see Bianchi 1981 fig. 6 for possibilities). Serpulids may have a single
major prominent longitudinal keel (as in Pomatoceros or Laminatubus, e.g., ten Hove & Zibrowius 1986 fig.
1) or two identical major keels may be present (as in Galeolaria, e.g., Dew 1959 figs 11, 12), even though
such keels may be indistinct as in some Hydroides spp. In other cases, the major longitudinal keel is
supplemented by secondary more subtle ones (compare Pomatoceros triqueter with P. lamarckii in Bianchi
1981 figs 42a, b, 43a, b). Finally, a number of longitudinal keels may be present (Metavermilia multicristata,
Serpula vermicularis, e.g., Bianchi 1981 figs 29, 13). The keels may either be sharp (Semivermilia
agglutinata: Bianchi 1981 fig. 33) or smooth (S. pomatostegoides: Bianchi 1981 fig. 34), straight (Hydroides
uniformis Imajima & ten Hove, 1986 fig. 1) or wavy (as in Semivermilia crenata: Bianchi 1981 fig. 31), or in
the form of longitudinal rows of larger denticles and smaller tubercules (Spirobranchus lima: Bianchi 1981
fig. 40).
Transverse tube ornamentation includes simple growth striations such as in Protula, circular growth rings
(Josephella marenzelleri: Bianchi 1981 fig. 50), flaring smooth trumpet peristomes directed toward the distal
end of the tube as seen in Ficopomatus enigmaticus. The most complex denticulate peristomes are found in
Filogranula stellata, F. calyculata, and F. gracilis (e.g., Bianchi 1981 figs 35–38).
A combination of numerous longitudinal keels and transverse ridges may form structures as in
Metavermilia arctica Kupriyanova (1993d fig. 1K) or Vermiliopsis labiata (see Imajima 1977 fig. 4). Tube
ornamentation in the free distal and attached proximal parts of one tube may differ (e.g., Filogranula
annulata: Bianchi 1981 fig. 37, Placostegus incomptus Ehlers (1887 pl. 60 fig. 8) or Pyrgopolon differens (ten
Hove, 1973 pl. IIb)). Tube ovicells used for brooding such as found in Rhodopsis (Fig. 2A), Chitinopoma, and
Pseudovermilia (Fig. 7D) are also a form of tube ornamentation.
The tube wall is usually uniformly opaque, but in species such as, for example, Ditrupa arietina and
Laminatubus alvini, the walls consist of two distinct layers: an inner opaque and outer hyaline layer; the latter
may cause a shiny surface in tubes of e.g., Bathyvermilia and Serpula crenata. A hyaline granular overlay is
present in tubes of Spiraserpula species (see ten Hove & Pillai 1994), as well as in Serpula oshimae and S.
hartmanae, in Hydroides mongeslopezi and also in an undescribed species of Apomatus (ten Hove unpubl.). It
may have been overlooked in other taxa. Placostegus (Fig. 1F), Vitreotubus, and Neomicrorbis have entirely
transparent tubes, and this situation also may occur in some spirorbins (e.g., Paradexiospira vitrea (Fabricius,
1780) and Protolaeospira striata (Quiévreux, 1963)). Scanning electron microscopy observation of some of
these tubes (ten Hove & Zibrowius 1986) suggested that transparency is caused by preferred orientation of
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