Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

More documents

Recommendations

Info

178 three alternate hydrothecae in two lateral rows and a long apophysis below the distal-most hydrotheca. Hydrocladia alternate, straight, with up to 10 segments, nodes transverse and distinct, flanked by swellings of the segment ends, segments long and thin, quite uniform in length (1.5–1.6 mm). Hydrocladial hydrothecae in two lateral rows, in strictly opposite pairs in the distal half of the segment, members of a pair not contiguous on any side, consecutive hydrothecae of one row very far apart. Hydrotheca curved, free part wedge-shaped in lateral view, duck-billed in oblique view, adcauline side adnate for less than half its length, sharply bent where becoming free, adnate part 0.4 mm long, free adcauline side nearly horizontal, straight to slightly concave, 0.55–0.60 mm long, upper side of hydrotheca shaped like a gabled roof, with lateral crease lines. Periderm of distal part of hydrotheca very thin and flexible. Opening very oblique, with one large, oval adcauline opercular flap, sometimes repeatedly present; perhaps also a small, very indistinct adcauline opercular valve present. Hydranth with about 20 tentacles, without abcauline caecum. Gonothecae on stem, often opposite a hydrocladium. Gonotheca oblong, about 2 mm long, maximal diameter about 1 mm, distal end truncate, opening on a short neck with wide diameter, lateral wall of gonotheca with about 6 thick annulations; near distal end an interior ring of periderm knobs. Remarks With its relatively large, pinnate colonies, and especially the widely spaced hydrothecal pairs with their long wedge-shaped ends, Salacia sibogae is quite easily identifiable in the present fauna. All examined samples come from a small area north-east of the Kei Island archipelago, not far from the type locality of the species. Most records lie in deeper waters, with a range of 40– 450 m (of the seven known records six are below 245 m, only one is from 40 m). Although the identity of the present material with Billard’s species is quite certain, the allocation of this species to the genus Salacia is not P. SCHUCHERT entirely secure because there might be more than just one opercular valve and the species appears intermediate between the genera Dynamena and Salacia. In many hydrothecae, the adcauline (upper) margin is thinner and it looks like a short adcauline opercular valve partitioned by a short median tooth (Fig. 34D). This was only visible in the stereomicroscope and the putative valve is not distinctly demarcated at its base. It was not possible to evaluate whether this is a true, rudimentary operculum or only an illusion. However, the hydrotheca is not entirely typical for the genus Salacia and perhaps the genus Dynamena might be more appropriate for this species. Millard (1975) mentions that in Dynamena the upper valve is usually smaller and it may have a median partition (see Dynamena crisioides). However, the distal part of the hydrotheca of S. sibogae is so flimsy and difficult to observe that no clear answer seems possible with ordinary light microscopy. Distribution Indonesia, Indian Ocean (Hirohito 1995). Type locality: Kei Islands, 5.473°S, 132.000°E, 204 m, on hard coralline sand. Salacia punctagonangia (Hargitt, 1924) Fig. 35. Sertularia punctagonangia Hargitt, 1924: 469, pl. 6: fig. 23. ?Salacia spec. – Hirohito 1995: 185, fig. 60d–e. Type material examined: Sertularia punctagonangia, NMNH, slide reg. number USNM 42655, part of a plume with male gonothecae. Other material examined: Kei Islands Expedition station 4, with female gonothecae. Differential diagnosis Similar to Salacia sibogae Billard, 1924 (see above), but stem occasionally forked, 7 cm high, nodes on stem absent in proximal region. Hydrocladial hydrothecae smaller, subopposite, some almost alternate, few opposite. Free adcauline wall of hydrotheca convex in side view, crosssection rounded and not roof-shaped, without lateral crease lines. Gonotheca smooth-walled, oblong oval, tapering below into pedicel, termi-
HYDROIDS OF THE DANISH EXPEDITION TO THE KEI ISLANDS Fig. 35. Salacia punctagonangia (Hargitt, 1924); station 4. A. Colony silhouette. B. Part of stem and hydrocladia. C. Side view of typical pair of hydrothecae. D. Oblique view of hydrothecal opening. E. Gonotheca in side view. – Scales: A = 1 cm; B, E = 0.5 mm; C = 0.2 mm. nal end truncate, with large convex operculum, with slight sub-terminal constriction, at height of constriction a ring of internal wart-like periderm nodules. Measurements: length of free adcauline wall of hydrotheca 0.4–0.5 mm, adnate part 0.3 mm, length of female gonotheca 1.8 mm, male gonotheca 1.3–1.4 mm. Remarks Salacia punctagonangia (Hargitt, 1924) is a rare species, so far only recorded from the Philippines (Hargitt 1924). Re-examination of Hargitt’s material showed that the present Indonesian material is indistinguishable from it. The only notable difference is the size of the gonothecae, the length of which is 1.3–1.4 mm in the type mate- 179 rial, but 1.8 mm in the material from the Kei Islands. The type material is clearly male, while the Indonesian material contains oocytes. The size difference is thus likely to be explained by the different sexes. Salacia punctagonangia (Hargitt, 1924) so closely resembles Salacia sibogae Billard, 1924, especially in the aspect of the colony, hydrothecae and dimensions, that I took it first as a variant of the latter. However, the various small differences are convincing evidence that the two morphotypes belong to different species. Both morphotypes were fortunately found at localities so close together (less than one nautical mile apart), that the respective populations must be considered sympatric. Because both localities are in rather deep waters (245 and 250 m) where
Page 1 and 2: HYDROIDS OF THE DANISH EXPEDITION T
Page 13 and 14: Family Solanderiidae HYDROIDS OF TH
Page 41: HYDROIDS OF THE DANISH EXPEDITION T
Page 93 and 94:
HYDROIDS OF THE DANISH EXPEDITION T
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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?