Acryptolaria minima Totton, 1930

Peña Cantero, Alvaro L., Marques, Antonio C. & Migotto, Alvaro E., 2007, Revision of the genus Acryptolaria Norman, 1875 (Cnidaria, Hydrozoa, Lafoeidae), Journal of Natural History 41 (5 - 8), pp. 229-291 : 254-256

Acryptolaria minima Totton, 1930

( Figures 10 , 16B , 18C , 19B, D ; Table X) Acryptolaria minima Totton 1930, p 162 –163, Figure 18a, b ; Ralph 1958, p 315, Figure 3e, f .

Material examined

Holotype: BMNH 1929.10 .10.3, Terra Noυa Expedition , Sta. 134, near North Cape, New Zealand, alcohol, fertile specimen 9 cm in height, 11–20 fathoms (19.8–36 m).

Description

Palmate colony, ca 90 mm in height, composed of two main stems, one of them basally giving rise to a conspicuous secondary stem. Stems strongly branched, giving rise to numerous lower-order branches (up to fourth order). Stems almost completely polysiphonic, branches polysiphonic up to distalmost ends, though in most distal parts usually as a single tube. Colonies alternately branched in one plane, though sometimes branches arising either in decussate pairs or alternately in several planes. Branches frequently anastomosed.

Hydrothecae alternate, in one plane. Hydrotheca tubular, almost completely cylindrical; diameter slightly decreasing at basal part. Hydrotheca gently curved abcaulinarly, adcauline wall approximately four-fifths adnate to internode. Adcauline wall convex; abcauline wall mostly concave, but slightly convex at basal part. Hydrothecal aperture circular, directed upwards, forming an angle of 40–60 ° with long axis of branches. Rim even, usually one to two renovations in most distal hydrothecae; renovations more numerous at basal and polysiphonic parts.

Coppinia 13–20 mm long and ca 3 mm in diameter. Gonothecae closely aggregated, pyriform, with a circular distal aperture. Coppinia without defensive tubes.

Remarks

Acryptolaria minima is well characterized by the shape and size of the hydrothecae. In fact, it is the species with the smallest hydrothecae amongst the known species of Acryptolaria (cf. Table XV). By contrast, apart from A. tortugasensis (see below), it has the largest nematocysts. Acryptolaria minima is also characterized by having hydrothecae almost completely adnate to the branches (only one-fifth of the adcauline wall is free). The wellmarked characters make it possible to corroborate some of the identifications made in the literature, such as that of Ralph (1958) for a specimen from Cook Strait, New Zealand.

Distribution

Acryptolaria minima seems to be a shelf species, having been found at depths between 20 ( Totton 1930) and 180 m ( Ralph 1958). Presently, it is known only from New Zealand waters, where it has been reported from off Cape North and Cape Maria van Diemen ( Totton 1930) and from Cook Strait ( Ralph 1958).

Figures

Figure 3. Acryptolaria bulbosa (Stechow, 1932). (A) Part of branch showing hydrothecal arrangement; (B–D) hydrothecae. All drawings from the holotype. Scale bar: 400 Mm.

Figure 10. Acryptolaria minima Totton, 1930. (A) Branch fragment showing hydrothecal arrangement; (B–E) hydrothecae; (F) gonothecae. All drawings from the holotype. Scale bar: 1 mm (A); 400 Mm (B–F).

Figure 16. Hydrothecal arrangement in Acryptolaria (continued). (A) A. longitheca; (B) A. minima; (C) A. minuta; (D) A. operculata; (E) A. pulchella; (F) A. tortugasensis. Scale bar: 500 Mm (A, D); 250 Mm (B, C, E, F).

Figure 18. Shape of hydrotheca in Acryptolaria (continued). (A) A. gracilis; (B) A. longitheca; (C) A. minima; (D) A. operculata; (E) A. pulchella; (F) A. tortugasensis. Scale bar: 100 Mm (A, C, F); 250 Mm (B, D, E).

Figure 19. Shape of gonothecae: (A) Acryptolaria conferta; (B) A. minima. Detail of different structures: (C) bottleneck-shaped basal part of hydrotheca in A. gracilis; (D) opercular structure in A. minima; (E) opercular structure in A. operculata; (F) longitudinal striae in hydrotheca of A. flabellum; (G) intrathecal cusp of A. tortugasensis. Scale bar: 100 Mm (A, B, D, F, G); 50 Mm (C); 250 Mm (E).