Ficopomatus talehsapensis, Pillai, 2008

Pillai, T. Gottfried, 2008, Ficopomatus talehsapensis, a new brackish-water species (Polychaeta: Serpulidae: Ficopomatinae) from Thailand, with discussions on the relationships of taxa constituting the subfamily, opercular insertion as a taxonomic character and their taxonomy, a key to its taxa, and their zoogeography, Zootaxa 1967, pp. 36-52 : 38-41

Ficopomatus talehsapensis , new species

( Fig. 1 A–D)

Synonyms:

Ficopomatus macrodon Southern 1921 , Pillai (1971, p. 116): distribution only based on Fauvel (1932).

Ficopomatus macrodon Southern 1921 , ten Hove & Weerdenburg (1978), in part, description and figures of the material from Taléh Sap, Gulf of Thailand, p. 103–106, fig. 4, e–g, o–p, cc–dd, ww.

Material examined: Type material, labeled Syntypes: BM (NH) 1938:5:7: 89–91, collected by N. Annandale from Taléh Sap, Gulf of Thailand fide Annandale, 1916); also studied and described by ten Hove & Weerdenburg (1978).

Description: The following description is based on characters observed on re-examination of Annandale’s Taléh Sap material, as well as those described by ten Hove and Weerdenburg (1978), indicated within quotation marks. For additional figures see ten Hove & Weerdenburg (1970, Fig. 4).

Tube: White, semicircular in cross-section, bearing single, median, smooth longitudinal ridge, rounded in cross-section, and not projecting anteriorly as pointed tooth over aperture ( Fig. 1 A). Faint, smooth, transverse ridges separated by smooth shallow transverse grooves occur on either side of median longitudinal ridge.

Worm: Branchial crown bears up to 5 to 7 radioles on each side. Interradiolar membranes: absent. Operculum occurs on left side, in position of the most dorsal radiole ( Fig. 1 B); opercular peduncle pinnule-free, wingless; fully formed operculum vesicular bearing distally “a more or less horny cap, which has a dorsal furrow. Thickness of the horny plate is positively correlated with increasing length of the cone.” For figures of opercula, including non-collapsed ones, see ten Hove & Weerdenburg (1978, Fig. l a–e). The juvenile specimen figured in the present account ( Fig.1 D) lacks a distal horny cap. Thorax consists of 7 chaetigers. Collar: continuous with the thoracic membrane on each side; both extending to end of thorax, uniting to form a postthoracic ventral flap, the apron.

Chaetae: Collar chaetae conspicuously toothed; Apomatus -chaetae absent; thoracic uncini partially raspshaped, with about ten to twelve teeth as seen in profile, in addition to the most anterior tooth, which is gouged; one or two anterior uncinal teeth, located just posterior to the gouged tooth consist of “one or two transverse rows of two or three teeth.” Abdominal uncini: rasp-shaped, with “13–15 teeth” as seen in profile, “including the anterior gouged one.” Abdominal chaetae: geniculate. See Hove & Weerdenburg (1978, Fig. 4 e–g for toothed collar chaetae, t–u for thoracic uncini, cc–dd for abdominal uncini and ww for abdominal chaetae).

Comparison between F. talehsapensis n. sp., and F. macrodon Southern, 1921 :

F. talehsapensis differs from F. macrodon in many respects. As regards the tubes, Annandale (1916, p.100) states that the tubes of the former are small and white. Indeed, adult sizes are quite small compared to the other known species of Ficopomatinae . Its tube diameter is up to about 0.75–1.0 mm, whilst that of F. macrodon Southern is double that.

According to ten Hove and Weerdenburg (1978) “The tube is shining white, semicircular in cross-section. Collar-like peristomes are absent in the material studied. Most of the tubes possess a high and sharp median keel ( Fig. 5 e); however, in a few tubes it is indistinct.” There is a significant discrepancy, though, with regard to the median longitudinal ridge in terms of the latter description and that actually occurring in Annandale’s specimens according to the present study. Ten Hove and Weerdenburg do not mention that the median longitudinal ridge of the Taléh Sap specimens ends in a sharp tooth over the aperture; they would have done so if it existed in any of the specimens. As seen in the photograph by ten Hove and Weerdenburg (1978 p. 104, fig.5e) and according to the present re-examination of type specimens, the median longitudinal ridge is smooth and rounded and does not terminate anteriorly as a pointed tooth over the aperture ( Fig. 1 A). In contrast, as originally described and figured for F. microdon by Southern (1921). As shown by Pillai (1971), and Fig. 1 E in the present account, the median longitudinal ridge is sharp and sinuous. As also stated by Southern (1921), it characteristically "terminates anteriorly over the orifice in a small sharp tooth”.

The worm in F. talehsapensis , Fig. 1B, attains a smaller maximum size than that of F. macrodon . According to ten Hove and Weerdenburg (1978, p. 105) “including the operculum, is at least up to 7 mm ” which agrees with that observed during the present study. On the other hand, according to Southern (1921), F. macrodon grows up to about 11.0 mm. The maximum total number of branchial radioles of both sides together in the Taléh Sap species, according to ten Hove & Weerdenburg (1978, p.103) is 14, whereas according to Southern (1921) and Pillai (1971), it is 17 in F. macrodon .

The operculum is also strikingly different in the two species. According to (ten Hove and Weerdenburg (1978) it is “a fleshy bulb, terminated by a more or less horny cap, which has a dorsal furrow” in the Taléh- Sap species. In contrast, there is no such “conical horny cap” or other outgrowths on the operculum of F.macrodon . According to Southern (1921) it is “rather fig-shaped….. The distal end is almost flat in some specimens, as shown in fig. 27 C, while in others it is markedly convex. There are no outgrowths either on the stem or on the head of the operculum. Usually there are patches of pigment, a narrow band just beneath the swollen head being rather constant.” Pillai’s description (1971, p. 115, fig. 8A & B) agrees fully with Southern’s (1921) description and figures, including opercular pigmentation, as shown in Fig. 1 F & G below.

Chaetae of the present species have been dealt with in detail by ten Hove and Weerdenburg (1978, p. 105–106, fig. 4 e–g, o–p, t–u, and cc–dd.). As regards the strongly toothed collar chaetae in F. enigmaticus, Fauvel (1932) describes them as possessing “two longitudinal rows of teeth …” As seen in SEM of collar chaetae of F. enigmaticus by Knight-Jones (1981, figs. 28 & 54), they may bear two rows of teeth. Such strongly toothed collar chaetae are present in all brackish-water serpulid taxa dealt with here, see Pillai (1960, 1965 & 1971), Hartmann-Schröder (1971), and ten Hove & Weerdenburg (1978), except in Marifugia , which lacks collar chaetal fascicles. The most anterior uncinal tooth in all ficopomatine genera is gouged. There is a difference, though, with regard to the uncini. As stated by ten Hove and Weerdenburg (1978, p. 105 and fig. 4 t –u and 4 cc–dd), in F. talehsapensis they are partly rasp-shaped in the thorax, and rasp-shaped in the abdomen. This appears related to the comparatively small size of the species. In contrast, the thoracic and anterior abdominal uncini in the larger, Ficopomatus macrodon are saw-shaped, with teeth arranged in a single row ( Southern 1921, figs. 27a & h). Abdominal chaetae are geniculate.

Etymology: The species is named after its type locality, Taléh Sap, Thailand.