Sertularella plicata, Galea, 2016

Galea, Horia R., 2016, Notes on some sertulariid hydroids (Cnidaria: Hydrozoa) from the tropical western Pacific, with descriptions of nine new species, European Journal of Taxonomy 218, pp. 1-52 : 29-30

Sertularella plicata sp. nov.

urn:lsid:zoobank.org:act:5CBEB7F6-12F7-403C-AC8D-58AE01B11AC7

Fig. 8 L–O; Table 3

Diagnosis

Small Sertularella with monosiphonic stems; side branches given off irregularly in one plane. Internodes moderately long and geniculate. Hydrothecae piriform, with 8–10 conspicuous, transverse ribs; aperture on short, narrow neck facing outwards; 3 or 5 internal, submarginal, lamellar cusps. Gonothecae unknown.

Etymology

From the Latin plĭco, -ātum, -āre (and the Greek πλέχω), meaning “pleat, pleated, to pleat”, to characterize the appearance of the external surface of the hydrothecal wall.

Material examined

Holotype

MUSORSTOM 3: Stn. CP121, colony composed of several sterile stems up to 1 cm high, epizoic on dead gorgonian (MNHN-IK-2012-16576).

Description

Colony composed of up to 1 cm high, monosiphonic stems arising from creeping, branching hydrorhiza. Basal parts of stems of varied length and ahydrothecate, perisarc smooth; above, stems divided into regular, moderately long, geniculate internodes, by means of slightly oblique nodes slanting in alternate directions; each internode with one, distal hydrotheca. Side branches arising irregularly from below the bases of stem hydrothecae and in the same plane as the stem; from one to several hydrothecae between two successive side branches; up to second order branching observed; structure identical to that of stem, except for the first internode, which is comparatively longer than following ones; distal-most, tendril-like internodes occasionally anastomose with each other or with neighboring stems. Hydrothecae swollen basally, then narrowing gradually distally to a short neck region projecting the aperture slightly outwards; adaxial side less than ½ adnate; walls with 8–10 conspicuous transverse ridges encircling the theca; numerous creases, perpendicular to the ridges, give the hydrotheca a wrinkled appearance; aperture rhomboidal, rim with four blunt cusps separated by shallow embayments; opercular apparatus composed of four triangular valves forming a low roof; 3 or 5 internal, submarginal, lamellar cusps (two latero-adaxial and one adaxial and, in some hydrothecae, two additional, latero-adaxial ones). Gonothecae not observed.

Remarks

Hydrothecae with such deep, transverse ridges are present in a number of congeners, but several distinctive features allow their separation from the new species: 1) S. areyi Nutting, 1904 , but its hydrothecae are provided with only 2–3 transverse ridges ( Fig. 7J ); 2) S. costata Leloup, 1940 is a much smaller hydroid (compare Fig. 8J and 8M); 3) S. crenulata Nutting, 1905 possesses a considerable number of closely-set, transverse ridges, and its hydrothecae are tronconical ( Vervoort 1993); 4–6) S. helenae Vervoort, 1993 ( Fig. 8H), S. paucicostata Vervoort, 1993 ( Fig. 8I) and S. pseudocostata Vervoort, 1993 , but their hydrothecae are larger and more tubular; 7) S. fraseri Galea, 2010 is a more delicate hydroid and its hydrothecae are provided with fewer ridges; 8) S. quadrata Nutting, 1895 has densely-striated, exceedingly long and tubular hydrothecae, with characteristically squared cross-section ( Nutting 1904); 9) the hydrothecae of S. sinensis Jäderholm, 1896 are only half adnate, and the number of ridges they carry reaches as many as 15 in the northern hemisphere ( Naumov 1969); 10) S. striata Stechow, 1923 , but in this species the internodes are comparatively shorter, almost collinear, and the hydrothecae are less fusiform and only about half adnate ( Millard 1964).

Geographical distribution

Philippines.

Figures

Fig. 7. (continued on next page) ― A. Idiellana pristis (Lamouroux, 1816) (TAIWAN 1, Stn. DW1), stem internode and basal part of cladium. ― B–G. Salacia macer Vervoort & Watson, 2003 (NORFOLK 1, Stn. DW1659). B. Stem internode and basal part of cladium. C. Hydrothecae, frontal view. D. Same, dorsal view. E. Hydrothecal aperture, frontal view. F. Hydrothecal aperture, oblique view, showing