Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

More documents

Recommendations

Info

184 Description Colonies erect, pinnate, up to 3 cm high, stems unbranched, monosiphonic, basal part without hydrothecae, delimited by oblique node from distal part; distal part with alternate hydrocladia and hydrothecae in two lateral rows, nodes at least in more distal parts visible, internodes elongate, apophysis for hydrocladium arising below most distal hydrotheca of internode, apophysis rather short, delimited by node from hydrocladium. Hydrocladia quite long, some with one or two side-branches, with distant nodes and a variable number of hydrothecae per internode. The two rows of hydrothecae on stem and hydrocladia more or less in one plane. Hydrothecae alternate, successive hydrothecae of one row well separated by a gap of about half a hydrothecal length. Hydrotheca roughly tubular, adnate for 7/8 of length, adcauline side curved, abcauline wall straight for almost entire length and nearly parallel to hydrocladial axis, length of abcauline wall around 0.45 mm, diameter of opening 0.2 mm, opening-plane almost parallel to hydrocladial axis, margin with four pointed cusps, slightly below margin of abcauline side at point of flexure a short intrathecal shelf. Floor of hydrotheca not reaching abcauline side, without distinct process towards interior of internode. Gonothecae developing in small clusters at very base of stem near junction to stolons. Gonotheca very large, length 3 mm without pedicel, major part cylindrical, tapering and curving below into pedicel, distal part with spiral annulation grading into shallow annulation and smooth part below, distal end truncate, margin with four shallow cusps, operculum pyramidal, composed of four flaps. Remarks Stechow & Müller (1923) doubted the validity of this species, suggesting it may be conspecific with S. quadridens. This was contested by Watson (2000) who described the gonotheca for the first time. The gonothecae of S. decipiens are larger and curved, have a spiral annulation, and develop at the base of the stem. The gonothecae of S. quadridens are smaller (up to 2.2 mm), straight, with sharp transverse ridges, and they P. SCHUCHERT develop in the hydrocladiate region of the stem. The examined samples of S. decipiens agreed well with Billard’s (1925b) description, which was also based on material from the Kei Islands. The Indonesian material shows some minor differences to the material of northern Australia described by Watson (2000): the hydrothecae are notably more widely spaced, the hydrocladia are sometimes branched, and the lower part of the gonotheca is smooth. These differences are here interpreted as intraspecific variation. The characteristic site of gonotheca development at the base of the stem renders this species quite easily identifiable. Distribution Indonesia, northern Australia. Type locality: Tual, Kei Islands, Indonesia, 22 m. Sertularella diaphana (Allman, 1886) Fig. 40. Thuiaria diaphana Allman, 1886: 145, pl. 18: figs 1–3. Sertularella diaphana var. delicata Billard, 1919b: 21, fig. 3A. – Billard 1925b: 161, fig. 24, pl. 7: fig. 14. Sertularella diaphana var. orthogona Billard 1925b: 161, fig. 23. Sertularella diaphana var. gigantea Billard, 1925b: 161, pl. 9: fig. 35. – Vervoort 1941: 213. Sertularella diaphana. – Bale 1919: 337, pl. 16: fig. 5. – Billard 1925b: 157, fig. 22 pl. 7: figs 12–13. – Millard 1975: 285, fig. 93A–D. – Calder 1991: 101, fig. 53, synonymy. – Vervoort 1993: 214, figs 45d–e & 46d, synonymy. – Hirohito 1995: 192, fig. 62b–d, pl. 12: fig. A. – Watson 2000: 31, fig. 24, synonymy. Material examined: Kei Islands Expedition station 107, on hydroid, with gonothecae. – Kei Islands Expedition, Neira Island, Banda Islands, 10 m, 5 Jun 1922, on hydroids, sponges and other substrata, numerous colonies, many with gonothecae. – Kei Islands Expedition, Bay of Ambon, 90 m, 2 Mar 1922, bottom of stones and sand, no gonothecae, corresponds to S. diaphana var. orthogona. Description Colonies erect, reaching heights of 12 cm, multipinnate. Stem thick, polysiphonic, forked or not, final branches pinnate with alternate hydrocladia which are more or less in one plane. Stem and branches divided into internodes in distal regions only, nodes oblique, sloping alternately to left and right. Each stem internode bearing three
HYDROIDS OF THE DANISH EXPEDITION TO THE KEI ISLANDS Fig. 40. Sertularella diaphana (Allman, 1886); Neira Island. A. Colony silhouette, height about 6 cm. B. Stem internodes with bases of hydrocladia. C. Hydrothecae of hydrocladium. D. Gonotheca. – Scales: B = 0.5 mm; C = 0.2 mm. hydrothecae in two rows and one hydrocladium, the latter rising just below the most distal hydrotheca. Hydrocladium straight, unbranched, with distant nodes and a variable number of hydrothecae per internode. The two rows of hydrothecae on 185 stem, branches and hydrocladia shifted somewhat to anterior surface. Hydrothecae alternate, the two rows of hydrothecae on the hydrocladia either in one plane or in two planes of variable obtuse to right angle, both rows well separated. Hydrotheca completely adnate or very nearly so, without floor, smooth, curved outwards, opening tilted towards abcauline side, adcauline side about 0.5 mm, opening diameter 0.22–0.25 mm. Marginal cusps low but pointed, no internal teeth. Lower end of adcauline hydrothecal wall often ending in a swelling, especially so in the cauline hydrothecae (Fig. 40B). Gonothecae borne on anterior surface of hydrocladia, elongated, polygonal in cross-section, truncated distally, length 2 mm, diameter 0.7 mm, no marginal spines, Variation The variant Sertularella diaphana var. delicata forms 1 cm high, monosiphonic shoots; variant S. diaphana var. orthogona has the two rows of hydrothecae set at a right angle; variant gigantea forms very large colonies, reaching dimensions of 35 x 28 cm (all after Billard 1925b). Remarks Only an abbreviated synonymy of this species is given here because several authors provided one in recent publications (Calder 1991, Vervoort 1993, Watson 2000). The sample from the Bay of Ambon was clearly referable to the variant orthogona, although it lacked the thickenings at the lower end of the adcauline hydrothecal wall. Vervoort (1993) also mentions material of this variant lacking the thickening. Distribution Widespread in tropical and subtropical waters of the Indo-Pacific and Atlantic. Type locality: Moreton Bay, Queensland, Australia. Sertularella quadridens (Bale, 1884) Fig. 41. Thuiaria quadridens Bale, 1884: 119, pl. 7: figs 5–6. – Weltner 1900: 586, pl. 46: figs 1–3. Thuiaria vincta Allman, 1888: 68, pl. 32: figs 2 & 2a. Sertularella quadridens. – Ritchie 1910b: 818, pl. 77: fig.
Page 1 and 2: HYDROIDS OF THE DANISH EXPEDITION T
Page 13 and 14: Family Solanderiidae HYDROIDS OF TH
Page 47: HYDROIDS OF THE DANISH EXPEDITION T
Page 99 and 100:
HYDROIDS OF THE DANISH EXPEDITION T
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
show all

Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

Create successful ePaper yourself

Delete template?

Save as template?