Flora of New Zealand Series

Zoopsis Hook.f. ex Gottsche, Lindenb. & Nees, Syn. Hepat. 473. 1846.

Type: Zoopsis argentea (Hook.f. & Taylor) Gottsche, Lindenb. & Nees (≡Jungermannia argentea Hook.f. & Taylor)

Plants closely creeping or adnate, often in interwoven thin patches, pellucid, pale to pure green, nitid when dry, small to very small, usually less than 800 µm wide. Branching sparing to common, irregular, the branches terminal, of Frullania (with half-leaf) and Zoopsis types (lacking a half-leaf) and ventral-intercalary; geotropic, subterete, microphyllous, pale, ventral-intercalary flagella (or extensions of leafy axes) typically common. Stems typically strongly flattened and gradually merging into the reduced leaves, in cross section planoconvex or, in a few taxa, subterete or elliptical; cortical cells normally in 6 rows (8–9 rows in a few taxa), the cells in the dorsal and lateral rows exceptionally large, inflated and pillow-like, forming a distinctive hyaloderm, the ventral 2(3) rows of cortical cells smaller, often conspicuously so, the cortical cells in surface view rather short, often in a zigzag arrangement like the scales of a reptile; medullary cells much smaller, numerous, forming a well-defined central conducting strand, the cells in surface view strongly elongated. Rhizoids infrequent to frequent, from bases of underleaves and at times from bases of lateral leaves, the tips often swollen and dendritic. Leaves variable, basically bilobed and with the insertion succubous (nearly longitudinally attached to lateral margins of axis), in a few taxa many-celled, with a distinct, many-celled disc, the lines of insertion extending nearly to dorsal stem midline, or (more commonly) in other taxa the insertion not extending to stem midline and then defining a continuous leaf-free dorsal strip of 2 rows of cortical cells; leaves in some species rudimentary and 4–6-celled, consisting of 2 basal cells and 2 “lobes” each formed of 1 or 2 specialized, curved, chlorophyll-free, papilliform cells, or the leaves reduced to ephemeral slime papillae. Cells leptodermous, usually inflated and pillow-like, subisodiametric, extremely large, 45–65 × 60–95 µm or even larger, the leaf and cortical cells of similar size; surface smooth. Oil-bodies several to many per cell, granular-botryoidal or finely granular-botryoidal (nearly smooth in Z. caledonica). Underleaves present throughout, inconspicuous, very small, comprised of up to ca. 12 cells or, more commonly, vestigial and comprised of 2–4 subspherical basal disc cells + a pair of 1-celled lobes each terminating in a slime papilla. Asexual reproduction lacking or by fragmenting or caducous leaf lobes (Z. ceratophylla, Z. matawaia) or by tubers (rarely in Z. leitgebiana).

Dioecious. Androecia on abbreviated, ventral-intercalary branches; deeply concave to ventricose and with a demonstrable disc, the apices bilobed; antheridia 1 per bract, the stalk 1- or 2-seriate. Gynoecia triradial, on abbreviated, ventral-intercalary branches; bracts of innermost series 2(3)-lobed from 0.6 to nearly to the base; lobes narrow, often with a few to several biseriate tiers, terminating in a single cell or a uniseriate row of 2–6 cells, the lobe margins entire or with a tooth; disc 2–5 cells high, the margins entire or with a tooth; bracteole similar to bracts or a little smaller. Perianth trigonous-fusiform, mouth deeply 6-lobed to ca. 0.5 in most species, the lobes narrow, with a few to several biseriate tiers, terminating in a uniseriate row of up to 6 often moniliform cells or, occasionally, a pair of laterally juxtaposed cells, the lobe margins entire, or (Zoopsis ceratophylla) the mouth lobed a small fraction of perianth length, the lobes caudate, each terminating in a cilium or (Z. bicruris) the mouth unlobed and dentate.

Seta with 8 rows of outer cells surrounding an inner core of 10–21 rows of small cells. Capsule ellipsoidal, yellow-brown and without red-brown pigments, wall 2- or (Zoopsis leitgebiana) 2–3-stratose; outer layer of cells with modified two-phase ontogeny, with primary walls lacking pigmented thickenings or nearly so, the secondary walls all (longitudinal + at times also transverse) with continuous sheets of brown or yellow-brown pigmented wall material + irregular nodular to weakly extending thickenings lending the walls a sinuous appearance; inner layer of cells short to narrowly long-rectangular, with narrow, yellow-brown semiannular bands, the bands usually complete, often incomplete.

Spores delicately areolate. Elaters straight or nearly so, hardly tapering toward the tips, bispiral.

A genus of 10 species, all of which are Old World. The center of diversification of the genus is evidently Australasia, with all three subgenera represented there. All subgenera (Amphizoopsis R.M.Schust., Eozoopsis R.M.Schust. and Zoopsis) occur in New Zealand, together with all but two species. Zoopsis setigera K.I.Goebel ranges from West Irian and Papua New Guinea and the Solomon Islands to Indonesia (Molucca Islands, Amboina) to Borneo (Grolle and Piippo, 1984). Zoopsis liukiuensis Horik. ranges from Queensland, New Guinea, New Caledonia, Solomon Islands and Samoa to the Moluccas, Indonesia (Java, Sumatra, Amboina), Borneo, Malaysia, Philippines, Taiwan, Liukiu Island and Kyushu in southernmost Japan (Grolle and Piippo, 1984). The genus is lacking in south temperate and tropical America and from Africa.

Zoopsis is appropriately named, the type species and those immediately allied to it have very large, pillow-like, polygonal cortical cells that evoke a curiously “reptilian” appearance. Species like Z. argentea, and in particular the var. flagelliformis, have evolved what appear to be linear thalli, the leaves reduced to vestiges that form mere scallops on the margins of the flattened “frond.” The remarkable Z. nitida has leaves reduced to ephemeral slime papillae. However, the more primitive species ( subg. Eozoopsis, subg. Amphizoopsis) retain leaves with a distinct lamina. The genus includes several of the most extraordinary hepatics found anywhere. They show progressive flattening of the axis and the coalescence of the flattened axis and rudimentary leaves into a ribbon-like “frond” that simulates a thallus.

References: Glenny et al. (1997); Renner et al. (2006); Schuster (1993, 1999a, 2000a); Scott (1969).

The following key and treatment of taxa are adapted, with considerable modification, from Schuster (1999a).