Plumularia lagenifera (sensu Millard, 1975)

Schuchert, Peter, 2013, The status of Plumularia lagenifera Allman, 1885 (Cnidaria, Hydrozoa) and related species, Zootaxa 3613 (2), pp. 101-124 : 106-112

Plumularia lagenifera

Most of the type material of P. lagenifera (BMNH 1959.10.21.1) is a dry herbarium preparation as already described by Allman (1885). Only a small part is kept in alcohol and it was only this material that was available for study. It consists of four stem fragments lacking soft tissues or gonothecae. The partially shrunken appearance of the material strongly suggests that it was also once part of the dry material and put into alcohol either by Allman himself or a later investigator. There are only a few hydrocladial segments left, but all of them have hydrothecae with a distinctly curved outer wall ( Fig. 8B–D ). The internal ridges of the hydrocladial segments are distinct, but not more pronounced than those seen in P. setacea ( Fig. 4 ). One peculiarity is the slight notch on the outside of the proximal annular thickenings, this in both the main and intersegment. However, this could be an artefact due to the drying out of the material. Also the strong curvature of the hydrotheca could in fact be pronounced by some inevitable shrinking during the initial dry preservation.

Other material of P. lagenifera collected in the region of Vancouver Island was identified as such if several of their hydrothecae had a convex outer wall ( Fig. 9 , lowest row). However, the curvature was rarely as pronounced as in the type material (e. g. Fig. 9D 3 , comp. with Fig. 8C–D ). Usually a number of hydrothecae within a single plume had almost straight walls ( Fig. 9B 5 ), whilst others were more or less curved ( Fig. 9B 3–B 4 ). There is thus a considerable variability of this character, although concave walls were never seen. The variability of the curvature could be used as an argument to consider those Pacific colonies with a straight hydrotheca, here attributed to P. setacea ( Fig. 6 ), as merely extreme variants of the same population. The only, but weak, counter-argument is the occasional presence of two apophysal nematothecae ( Fig. 7A ), a trait that was never seen in the P. lagenifera samples examined for this study.

(A) MHNG-INVE-54566, Plymouth, GB, 12– 18 m. (B) MHNG-INVE-36290, Roscoff, 0 m. (C) MHNG-INVE-29393, Bay of Morlaix , 20 m. (D) MHNG-INVE-70533, Roscoff, 70 m. (E) MHNG-INVE-37537, Spain, 20 m. (F) MHNG-INVE-25346, Iceland, 206 m.

(A) MHNG-INVE-36290, Roscoff , 0 m. (B) MHNG-INVE-54566, Plymouth, GB, 12- 18 m. (C) MHNG-INVE-37537, Spain, 20 m. (D) MHNG-INVE-25346, Iceland, 206 m. (E) MHNG-INVE-29393, Bay of Morlaix. (F) MHNG-INVE-70533, Roscoff, 70 m. (D) MHNG-INVE-78076, Vancouver Island , Canada, 22 m.

Comparing the figures of the Atlantic P. setacea ( Fig. 4 ) and P. lagenifera ( Fig. 8 ), the latter seem to have distinctly larger stem segments, but more samples could not confirm this (table 1). For all variables there is an overlap of their sizes and a single character variable would not allow the two populations to be distinguished reliably. Principal components analysis ( Dunn & Everitt 1982) can analyse numerous variables simultaneously by producing a smaller number of abstract variables (linear combinations of the original variables, principal components) and it provides a graphical summary which visualizes the data by placing similar samples close together, while dissimilar samples will result in points which are more distant. If this graph shows that the data result in distinct, spatially separated clusters, then independent characters can be used to identify these groups (in this case the convex hydrotheca or the geographic origin). The variables of table 1 can be combined so that two new variables (PC1 and PC2) represent about 54 % of the original variation ( Fig. 11 ). The broken stick criterion ( Frontier 1976; Jackson, 1993) showed that only components 1 and 2 are usable (43.9 and 20.5 %, see figure 11). Exclusion of the variable "plume height" which is highly dependent on environmental conditions did not yield in significantly different clustering (not shown).

(A) MHNG-INVE-78965, Puget Sound, 118 m. (B) MHNG-INVE-78076, Vancouver Island , 22 m (C) MHNG-INVE-78077, Vancouver Island, 0.5 m .

(A) BMNH 1915.3 .6.44, Vancouver Island , identified by C. M. Fraser. (B) MHNG-INVE-25120, floating docks of Friday Harbor Laboratories. (C) MHNG-INVE-78974, floating docks of Friday Harbor Laboratories. (D) MHNG-INVE-78079, Juan Fuca Strait, 22 m.

(A) MHNG-INVE-78964, floating docks of Friday Harbor Laboratories. (B) MHNG-INVE-78966, floating docks of Friday Harbor Laboratories. (C) MHNG-INVE-25120, floating docks of Friday Harbor Laboratories. (D) MHNG-INVE-78079, Juan Fuca Strait, 22 m.

The clusters of Atlantic P. setacea a nd Pacific P. lagenifera show a more or less good separation ( Fig. 11 ), but it is not complete. Moreover, the samples of P. setacea of the NE Pacific are intermediate to both populations and make a distinction even more difficult using numeric values alone.

The measurements thus give us no additional, solid argument for a separation of P. lagenifera from P. setacea . We are thus still left with the curvature of the outer hydrothecal wall as the only trait that enables us to separate the two nominal species. Unless future population genetic analyses indicate otherwise, it seems preferable to regard P. lagenifera as distinct from P. setacea .

The status of the South African P. lagenifera sensu Millard, 1975 , here attributed to the name P. gaimardi , is discussed in the following section.

Figures

FIGURE 3. Graphic illustration of measured values of the perisarc skeleton. (A) Single plume, ph = plume height. (B) Stem segments; cs = cauline segement length, cd = diameter of cauline segment in middle region, ah = origin of apophysis, al = apophysis length. (C) Repeated hydrocladial segments; as = length of ahydrothecate segment, hs = length of hydrothecate segment, td = depth of hydrotheca, nl = length of lateral nematotheca, tp = position of base of hydrotheca, np = position of infrathecal nematotheca.

FIGURE 4. Variability of microscopic structures of Plumularia setacea from the NE Atlantic. First row (A1 to F1): stem segments and first hydrocladial segment. Second row (A2 to F2): hydrothecae and ahydrothecae segments from the cladia. Third row (A3 to F3): abcauline walls of hydrothecae.

FIGURE 5. Variability of gonothcae of Plumularia setacea, sex is indicated by symbols (♀ female, ♂ male).

FIGURE 6. Variability of microscopic structures of Plumularia setacea from the NE Pacific. First row (A1 to C1): stem segment and first hydrocladial segment. Second row (A2 to C2): hydrothecate and ahydrothecate segments from the cladia. Third row (A3 to C3): abcauline walls of hydrothecae.

FIGURE 7. Plumularia palmeri Nutting, 1900, microscopic details of the syntype specimens (USNM 018625) (A) Stem segment. (B) Hydrothecae and ahydrothecate segment from hydrocladium. (C–D) Abcauline walls of hydrothecae.

FIGURE 8. Plumularia lagenifera Allman, 1885, microscopic details of the schizoholotype (BMNH 1959.10.21.1). (A) Stem segments. (B) Hydrothecae and ahydrothecate segment from hydrocladium. (C–D) Abcauline sides of hydrothecae. (E) Median inferior nematotheca. (F) Lateral nematotheca seen from inner side.

FIGURE 9. Microscopic details of some Plumularia lagenifera samples from the NE Pacific. First row (A1 to D1): stem segments and first hydrocladial segment. Second row (A2 to D2): hydrothecate and ahydrothecate segments from the cladia. Third row (A3 to D4): abcauline walls of hydrothecae.

FIGURE 11. Principal Components Analysis (component axis 1 and 2) of morphological variables of P. setacea, P. lagenifera, and P. gaimardi samples used for this study (see table 1). For details see text.