Stolella Annandale, 1909

Wood, Timothy S., 2022, Phylactolaemate bryozoans at the Zoological Survey of India and a taxonomic key to Indian Phylactolaemata, Zootaxa 5200 (2), pp. 401-435 : 428

Stolella Annandale, 1909

This group includes species “with upright zooecia joined together by an adherent pseudostolon in a linear series, the pseudostolon consisting of a prolongation in one direction of the base of one of the zooecia; no gelatinous investment present” (Annandale 1909).

The genus was erected to accommodate a new species, Stolella indica , described more fully in this paper. Additional sightings of S. indica were reported in North America by Rogick (1943) and in central Africa by Wiebach (1964), neither of them resembling Annandale’s holotype. In South America Ernst and Eveline Marcus together described a total of six plumatellid species, placing five of them in the genus Stolella ( Marcus 1941, 1942; DuBoisReymond Marcus 1953).

It is worth noting that nearly all of the Stolella species, including S. indica , were reported to be growing on filiform substrata such as duckweed roots, filamentous algae, or the narrow stems and leaves of submerged macrophytes. Under such conditions I have found it not unusual for plumatellid zooids to become elongated. Even on broad substrata it is possible to encounter elongated and tapered zooids among species in which this growth form is atypical ( Fig. 11 ). Zooid length is so inconsistent that in his African collection of Stolella indica Wiebach specifically set aside and labeled small subsamples exhibiting elongate zooids, because all other zooids in the specimen appeared to lack this feature ( Wood 2020).

The same variability is seen in Stolella material from Ernst and Eveline Marcus deposited at the NHMUK. While the stolon-like growth is certainly striking, it is often not representative of the entire colony. I am therefore inclined to regard this feature as an interesting phenomenon, possibly imposed by environmental conditions, but not a reliable foundation for an entire genus. I suggest that Annandale’s Stolella be retired and replaced with Plumatella .

Figures

FIGURE 11. Stolella indica, holotype (now Rumarcanella indica). (a) Floatoblast valves from ZEV3482/7, scale bar = 100 µm; (b) SEM image showing hypertubercles on a portion of the floatoblast dorsal fenestra, scale bar = 25 µm.