Contributions to Zoology, 79 (2) – 2010Bastian T. Reijnen; Bert W. Hoeksema; Edmund Gittenberger: Host specificity and phylogenetic relationships among Atlantic Ovulidae (Mollusca: Gastropoda)

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Results

Species and associations

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A total of 104 samples of ovulids was collected, representing viz. Cyphoma gibbosum (Linnaeus, 1758), Cyphoma signatum Pilsbry and McGinty, 1939, Simnialena uniplicata (Sowerby II, 1848) and Cymbovula acicularis (Lamarck, 1810) (Fig. 2, including specimen resembling the so-called C. bahamaensis). The 72 snails of Cyphoma gibbosum that could be studied were found with 21 alcyonacean species, representing nine genera. The 27 individuals of Cymbovula acicularis were found in association with five gorgoniid species, belonging to two genera. Simnialena uniplicata occurred with two congeneric host species, but since only four individual snails were found, it would be premature to derive any conclusions about host specificity. Unfortunately, only a single specimen of Cyphoma signatum could be studied, which was associated with Plexaurella dichotoma (Esper, 1791). This gorgonian species was also mentioned by Botero (1990), who additionally reported the congeneric P. nutans as a host for C. signatum. Due to the poverty of its records, the host preferences of this ovulid remain largely unknown.

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Fig. 2. Shells in dorsal and ventral view. a-d) Cymbovula acicularis (juvenile and adult); e) Cyphoma signatum; f-g) Simnialena uniplicata (juvenile); h) Simnia patula; i) Cyphoma gibbosum. Scale bars 1 cm (left, for a-d and f-h; right, for e and i).

From a total of 46 octocoral species recorded at Curaçao, 26 (57%) were found to be occasionally parasitized by one or more ovulid species (Table 2). Not all encountered Octocorallia species were found associated with ovulids. Additionally, a list was composed (Table 3) of encountered Octocorallia without associated ovulids.

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Table 2. Host-species associations between Ovulidae and Octocorallia.

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Table 3. Overview of collected Octocorallia that were not found to be parasitized by Ovulidae.

Phylogeny reconstruction

Cyphoma gibbosum is a common Caribbean species that is easily recognized by its colour pattern and morphology. To exclude possible sibling species occurring on, for example, different hosts or at other localities at Curaçao, several individuals from different Octocorallia species and from different localities along the coast were sequenced. Based on the molecular data no sibling species occurrence was detected. In Fig. 3 the results of the combined dataset subjected to a maximum likelihood analysis (ML) with bootstrap values is presented.

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Fig. 3. Maximum likelihood analysis for combined Atlantic and Indo-Pacific Ovulidae based on 16s and CO-I data. The values above the branches represent bootstrap values (100 replicates).

The phylogeny reconstruction indicates that there is a separation between the Atlantic and the Indo-Pacific clade (moderately supported, bootstrap value 70), although the East-Pacific species Neosimnia arcuata clusters with the Atlantic clade (poorly supported, bootstrap value 51). Simnialena uniplicata (Fig. 2f-g), Neosimnia arcuata and Cymbovula acicularis (Fig. 2a-d) are characterized conchologically by long and slender shells, but in the cladogram S. uniplicata does not appear as sister species to either N. arcuata or C. acicularis. Instead, it forms a highly supported (bootstrap value 100) clade with the Cyphoma group. The individual sequence of the ovulid specimen resembling Cymbovula bahamaensis (Fig. 2c) forms a highly supported clade (bootstrap value 100) with the included C. acicularis species.