Spinosphaera Hessle, 1917
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https://doi.org/ 10.5281/zenodo.176723 |
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https://doi.org/10.5281/zenodo.5627893 |
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https://treatment.plazi.org/id/03828032-FF83-FFD5-F5C6-FD27FCE2FB5D |
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Plazi |
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Spinosphaera Hessle, 1917 |
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Spinosphaera Hessle, 1917 View in CoL
Type species: Spinosphaera pacifica Hessle, 1917 , by monotypy.
Diagnosis. Prostomium in two parts, basal part sometimes with eyespots, distal part forming shelf-like process from which buccal tentacles originate. Peristomium restricted to lips; upper lip short, hood-like, lower lip narrow. Segment 1 conspicuous dorsally, laterally and ventrally, forming ventral lobe below lower lip. Anterior segments not dorsally inflated, lateral lobes absent. Anterior segments with smooth mid ventral shields, followed by mid ventral stripe extending from posterior notochaetigerous segments to pygidium. Branchiae absent. Notopodia beginning from segment 4 and extending for variable number of segments. Notochaetae arranged in two oblique tiers, those on anterior tier shorter; anterior notochaetae on both tiers as bilimbate capillaries; posterior notochaetae on both tiers with serrated tips. Neuropodia beginning from segment 5, forming low rectangular ridges slightly raised from surface of body, internal supporting rods on abdominal neuropodia absent. Uncini short-handled, with conspicuous dorsal button, short triangular heel and prow distally pointed and downwardly directed; uncini arranged in double rows from segment 11, for a variable number of segments.
Remarks. Spinosphaera was revised by Londoño-Mesa (2003), who described three new species, redescribed S. oculata Hartman, 1944 and transferred S. cowarrie Hutchings, 1997 to a new genus, Hutchingsiella Londoño-Mesa, 2003 . The author emphasized the importance of the structure of the notochaetae of posterior notochaetigerous segments, which characterize the group, and which he named as “ spinosphaera chaeta”.
However, although S. pacifica Hessle 1917 , the type species of the genus, and some other species of the group have unique notochaetae on the posterior tier of posterior notochaetigerous segments, as illustrated by Hessle (1917) and in this paper ( Fig. 5 View FIGURE 5 B–D), Londoño-Mesa (2003) mistakingly illustrated “ spinosphaera chaetae” as flail-tipped capillaries, which occur in several genera of terebellines. He then proceeded to describe additional species of the genus which actually lack the characteristic chaetae. True “ spinosphaera chaetae” have uniform broad winged limbation on both margins basally, which is broader than the width of the shaft, followed by a coarsely spinulated process originating from a swollen part of the shaft, with narrow limbation restricted to the outer margin, and finely serrated tip ( Fig. 5 View FIGURE 5 B–D).
Londoño-Mesa’s drawings of S. carrerai (2003: 750, Fig. 2 View FIGURE 2 C) illustrate notochaetae from both the anterior and posterior tiers of a posterior notochaetigerous segment, both these chaetae have long, hirsute limbation inside which the shaft is visible. This indicates that the shaft is not involved in the formation of the hirsute process, which is formed from the limbation, as occurs in Amphitritides , Neoleprea , Phisidia Saint-Joseph, 1894 , Terebella Linnaeus, 1767 , Tyira and several other genera of terebellines, but not in S. pacifica , according to the figure provided by Hessle (1917: 209, Fig. 60a). This indicates that S. carrerai cannot be classified as possessing true “ spinosphaera chaetae” which characterize the genus and occur in the type species.
The genus currently contains six species, including S. barega sp. nov., described below. Of those, only S. pacifica , S. harrisae Londoño-Mesa, 2003 , according to drawings provided in the original description, and S. barega sp. nov., possess the true “ spinosphaera chaetae” as defined above. These three species also share other features, most of which are not present in the other three species, such as 20–23 pairs of notopodia, chaetae of the anterior tier of notochaetae on posterior notochaetigerous segments alimbate and serrate, with blade at an angle with the shaft, and uncini arranged in double rows terminating before the segment on which notopodia terminate. The characteristics of all species of Spinosphaera currently recognized are listed in Table 2 View TABLE 2 .
Londoño-Mesa (2003) removed S. cowarrie from Spinosphaera and erected the new genus Hutchingsiella Londoño-Mesa, 2003 to accommodate it because, according to him and the original description ( Hutchings 1997a), it has notopodia beginning from segment 5, neuropodia beginning from segment 6, greater number of segments with uncini arranged in double rows, more pairs of notopodia than any other species currently assigned to Spinosphaera and the notochaetae of posterior notochaetigerous segments having a different morphology. These chaetae in H. cowarrie are alimbate and distally serrate, with blade at an angle with the shaft on both the anterior and posterior tiers of notochaetae.
Re-examination of type material of H. cowarrie showed that, contrary to its original description ( Hutchings 1997a) and the redescription provided by Londoño-Mesa (2003), this taxon has notopodia from segment 4 and neuropodia from segment 5. So, the major differences between H. cowarrie and S. pacifica are with regards to the numbers of pairs of notopodia and neuropodia with uncini arranged in double rows, and the absence of “ spinosphaera chaeta” in H. cowarrie . Similar differences are found between S. pacifica and the three other species which Londoño-Mesa considered as belonging to this genus, S. carrerai Londoño-Mesa, 2003 , S. hutchingsae Londoño-Mesa, 2003 and S. oculata ( Table 2 View TABLE 2 ). The fact that all these species are grouped in Spinosphaera , but not H. cowarrie , is inconsistent and makes the diagnosis of Spinosphaera considerably continued.
S. oculata S. pacifica S. barega sp. nov.
broader than those of the other genera of the subfamily. However, as previously stated, we prefer to wait for the results of the phylogenetic analysis of the group, which is in progress (Nogueira and Hutchings in prep.), before reorganizing these genera and their components.
TABLE 2. Comparison between the species currently assigned to the genus Spinosphaera. S. carrerai S. harrisae S. hutchingsae
| Type locality | off Punta Herradura, southern Mexican Carri- bean Sea | off San Diego, California, USA | Contoy Island, northern Mexican Carribean Sea |
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| Size: length x width (mm) | 11 x 0.5 | 39 x 1.5 | 10.5 x 1 |
| Arrangement of eyespots on basal part of prostomium | one cluster with 2–3 eye- spots at each lateral | large eyespots concentrated laterally, small eyespots con- tinuing dorsally, with mid dor- sal gap | big eyespots concentrated laterally, small eyespots forming uninterrupted row across dorsum |
| Notopodia on segments | 4–18, 15 pairs | 4–23, 20 pairs | 4–25, 22 pairs |
| Type of notochaetae on pos- terior tier, on posterior tho- racic segments | flail-tipped | spinosphaera chaetae | flail-tipped |
| Type of notochaetae on ante- rior tier, on posterior thoracic segments | flail-tipped | alimbate and serrate, with blade at an angle with the shaft | flail-tipped |
| Ending of uncini arranged in double rows | close to pygidium (seg- ment 75) | segment 22 | until end of fragments, long- est fragment examined with 35 segments |
| Nephridial papillae on seg- ments | absent or, at least, not seen | 7–12 or 13 | 17 |
| Source | Londoño-Mesa 2003 | Londoño-Mesa 2003 | Londoño-Mesa 2003 |
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