Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

More documents

Recommendations

Info

140 polysiphonic colonies. Hydranths polymorphic. Gastrozooids with club-shaped body and with two well separated whorls of tentacles. Gonozooids with either one tentacle or none, with one whorl of gonophores. Dactylozooids small, tentacle-like. Gonophores released as immature medusae. Young medusa with four filiform tentacles, manubrium simple. Remarks When Nutting (1905) described Balea mirabilis, he also created the new family Tubidendridae to accommodate it. Because the name Balea is preoccupied for a gastropod, Stechow (1919: 154) renamed the genus Balella. Some authors, e.g., Fraser (1938), recognized the family Tubidendridae, while Stechow (1922) referred Balella to the new subfamily Balellinae of Clavidae McCrady, 1859. Millard (1975), Bouillon (1985a), and Hirohito (1988) referred the genus to the family Bougainvilliidae. Because the gonophores of Balella are produced on the body of hydranths they can be placed neither in the Bougainvilliidae nor the Cordylophoridae (sensu Schuchert 2001, the taxon Clavidae is a synonym of Hydractiniidae). Because of this and its unique tentacle arrangement it is here placed again in the family Tubidendridae. The polymorphic, almost sessile polyps as well as the young medusae suggest close affinities with the Hydractiniidae. Nutting (1905) made cross-sections of the stem and observed naked coenosarc at the surface. This prompted him likewise to associate the Tubidendridae with the Hydractiniidae. The presence of such naked coenosarc could not be seen with sufficient accuracy in the present samples and no cross-sections could be made. Further discussions on the affinities of Balella mirabilis must await information on the adult medusa. Balella mirabilis (Nutting, 1905) Fig. 2. Balea mirabilis Nutting, 1905: 940, pl. 2: fig. 3, pl. 7: figs 3– 4. – Jäderholm 1919: 4, pl. 1: figs 1–4. Balella mirabilis. – Hirohito 1988: 91, fig. 32a–c. Material examined: Kei Islands Expedition station 81, about 25 colonies, some with medusae buds. P. SCHUCHERT Description Erect hydroid colonies reaching 6 cm in height, irregularly pinnate, side-branches primarily in one plane. Stem and branches polysiphonic to the tips, component tubes neatly parallel and compactly fused together. Hydrorhiza a large, tangled mass of very fine stolons anchoring the colony in the sediment. Polyps polymorphic, with gastrozooids, gonozooids, and dactylozooids. Gastrozooids up to 1.2 mm high, sitting preferentially on upper and under side of the sidebranches in a wide and shallow perisarc collar; body of gastrozooids with a slender, pedicel-like lower part and a swollen, pear-shaped main body; nipple-shaped hypostome very high, two well separated whorls of filiform tentacles, about ten tentacles per whorl, lower whorl of tentacles at base of swelling, second whorl at base of hypostome, tentacles tapering, evenly covered with nematocysts, gastrodermal cells chordoid. In younger gastrozooids the two tentacle whorls more approximated. Gonozooids only half the size or less of gastrozooids, very slender and only slightly swollen distally, base in a short, tubular perisarc collar; at distal end a single, thin tentacle, may be absent; at one third from upper end a single whorl with 4–6 medusae buds. Dactylozooids very numerous and often regularly spaced, finger-like, with no or very low perisarc collar, epidermis of dactylozooids with only few euryteles. Medusa buds up to 0.25 mm, oldest observed stage with four radial canals, four marginal bulbs, each with thick epidermis and a short tentacle, manubrium simple, without visible gonad tissue. Nematocysts similar to the ones described below. Nematocysts: desmonemes, four coils when discharged, approx. 4 x 2.5 µm; microbasic euryteles, about 7 x 2.5 µm, almond-shaped, discharged shaft about as long as capsule, only slightly swollen. Remarks The present material is the first find of this species in Indonesian waters. The gonozooids and gonophores are here described for the second time only. They were first seen by Jäderholm
HYDROIDS OF THE DANISH EXPEDITION TO THE KEI ISLANDS Fig. 2. Balella mirabilis (Nutting, 1905). A. Silhouette of colony, note massive hydrorhiza. B. Part of branch with gastrozooids, gonozooids, and dactylozooids. C. Dactylozooid. D. Gonozooid with medusae buds and tentacle; left of the gonozooid an empty perisarc collar of a young gastrozooid. E. Marginal bulb with tentacle of medusa, seen from inside. – Scales: A = 1 cm; B = 0.5 mm; C, E = 0.1 mm; D = 0.2 mm (1919) in material from Japan and he described the gastrozooids as devoid of tentacles. Contrary to the material of Jäderholm, the gonozooids of the present material usually had a single tentacle (Fig. 2D); some, however, were devoid of such a tentacle (Fig. 2B). Whether this is due to mechanical damage or represents a natural polymorphism could not be determined. Distribution Rare species, occurring at the coasts of Japan, Hawaii, and Indonesia; depth range 49–232 m, on sandy or muddy bottoms. Type locality: Hawaiian Archipelago, between Molokai and Maui, 232 m. Family Stylasteridae Conopora major Hickson & England, 1905 Fig. 3. 141 Conopora major Hickson & England, 1905: 25, pl. 3: figs 33–35. – ?Broch 1936: 91, fig. 30, pl. 13: fig. 38. – Boschma 1956: F100, fig. 82, 2c. – Boschma 1957: 39, bibliography. – Cairns 1991: 73. Material examined: Kei Islands Expedition station 45, 14 colonies, some attached on stones, preserved dry, associated polynoid polychaetes often present. Description Colonies forming erect, calcareous skeleton, 1–4 cm high, robust, arborescent, not uniplanar, branches short, with up to 3 cyclosystems, main stem with associated polynoid polychaetes that induce trunk to grow into hollow tube with slitlike openings. Coenosteum white, microscopic texture linear-imbricate, macroscopic texture smooth. Nematopores only present locally, preferentially near base, rare or mostly absent in distal parts of colony, nematopores on shallow mounds. Clyclosystems in region inhabited
Page 1 and 2: HYDROIDS OF THE DANISH EXPEDITION T
Page 3: HYDROIDS OF THE DANISH EXPEDITION T
Page 13 and 14: Family Solanderiidae HYDROIDS OF TH
Page 55 and 56:
HYDROIDS OF THE DANISH EXPEDITION T
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
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?