Acryptolaria minuta, Watson, 2003

Watson, Jeanette W., 2003, Deep-water hydroids (Hydrozoa: Leptolida) from Macquarie Island, Memoirs of Museum Victoria 60 (2), pp. 151-180 : 163-164

Acryptolaria minuta sp. nov.

Figures 13A–C

Material examined. Stn 130, NMV F 91338 , holotype, small infertile colony of five small stems, two branched, on dead primnoid gorgonian, malinol-mounted microslide .

Description (of holotype). Tallest stem 9 mm high, broken off at tip, 3.5 mm wide at base; stems branched once in one plane; branched stems arising from a small matted plug of stolons, simple stems from junction of stolonal tubes; taller stems with up to four polysiphonic tubes intergrown and rather contorted proximally, becoming linear distally; polysiphonic tubes running almost to top of stems; stems lightly fascicled; branches given off beside a hydrotheca.

Hydrothecae biseriate, alternate, long, tubular, somewhat frontally directed, scarcely overlapping, curving gracefully outwards at an angle of 50–60° from hydrocladial axis; single hydrothecae on proximal region of larger stems partially immersed in fascicular tubes. Adcauline hydrothecal wall smoothly convex, free wall slightly more than half length of adnate wall; adnate wall narrowing proximally downwards into hydrocladium, base of wall ending in minute knot of perisarc; abcauline wall smoothly concave, passing without interruption into hydrocladium. Margin evenly circular, transverse to hydrothecal axis, very weakly everted, sometimes with several replications of rim. Perisarc of stem and branches firm, thinning a little on hydrotheca. Hydranths deeply retracted into hydrotheca; with c. 12 tentacles.

Colour. Pale honey-yellow to colourless.

Measurements (µm)

Branch distance between hydrothecae on same side 624–728

width at junction of adnate and free adcauline walls 152–168 Hydrotheca length of free adcauline wall including marginal replications 200–368

length of adnate adcauline wall 408–464

diameter at margin 104–128

Etymology. Describes the minute nature of the colonies.

Remarks. The habit of Acryptolaria minuta is similar to that of A. patagonica described above. The species is, however, considerably smaller in critical dimensions of the hydrocladium and hydrotheca. The slightly everted margin of the hydrotheca resembles A. conferta minor Ramil and Vervoort, 1992 but it is smaller and the hydrothecae are frontally directed in contrast to those of A. conferta minor which, according to these authors, lie in the plane of ramification of the branches.

Even if the colonies are immature specimens of a larger species their smaller dimensions and sparsely branched habit matches no other known species of Acryptolaria .

Figures

Figures 13A–C. Acryptolaria minuta sp. nov., stn 133. A, whole colony. B, part of branch. C, hydrotheca with replicated margin. Scale bar: A, 3 mm; B, 0.5 mm; C, 0.2 mm.