Plumularia gaimardi (Lamouroux, 1824)

Schuchert, Peter, 2013, The status of Plumularia lagenifera Allman, 1885 (Cnidaria, Hydrozoa) and related species, Zootaxa 3613 (2), pp. 101-124 : 112-113

Plumularia gaimardi

Material of the present study included also the sample of Ritchie (1909), which according to Billard (1909) matches exactly the type specimen of P. gaimardi ( Lamouroux, 1824) . Most of the other material is mentioned in Millard (1957, 1975).

The taxonomic history of this species and its possible identity with P. lagenifera or P. setacea has already been outlined in the introduction. The South African P. setacea- like samples with a curved hydrothecal wall ( Fig. 12 ) were first assigned to P. lagenifera by Broch (1914) and subsequently by Millard (1957; 1975), although Billard (1909) showed that the correct name for this South African morphotype is P. gaimardi ( Lamouroux, 1824) . Plumularia gaimardi and P. setacea are clearly distinct species as both morphotypes occur sympatrically in the same environment ( Millard, 1975; own material listed below). Plumularia gaimardi resembles P. lagenifera , but both nominal species should be considered distinct. Plumularia gaimardi is distinguishable by the often recurved neck of the female gonotheca ( Fig. 13A 1 ) and the thickened abcauline wall of the hydrotheca ( Fig. 12 , lower two rows). Measurements (table 1, summaries) allow a distinction using the variables cs (length of abcauline segments), ah (position of apophysis), and as (length of ahydrothecate segments). The PC analysis clearly separated the South African material from Pacific P. lagenifera and P. setacea ( Fig. 11 ). Preliminary molecular data ( Moura et al. 2011) also indicates that samples of P. lagenifera from the NE Pacific and South Africa belong to separate lineages.

The South African P. lagenifera -like hydroids and Pacific P. lagenifera are thus distinguishable and because of their widely disjunct occurrence they should be attributed to separate species. Here, I suggest that the name P. gaimardi ( Lamouroux, 1824) is used for South African P. lagenifera -like hydroids. Although the type material for P. gaimardi is lost (see above), Billard (1909) found it identical to a sample described and depicted by Ritchie (1909), which was included in the present analysis. It is identical with the form having shallow hydrothecae ( Fig. 12 , rows A and B). Millard (1975) found that her samples comprised two rather distinct forms, although intermediate ones connected them. One is the form with shallow hydrotheca conforming with P. gaimardi , the other form has larger plumes and deep hydrothecae ( Fig. 12 , column D). It was interesting to note that where the substrate was still identifiable, the morphotype with shallow hydrotheca was always found on laminarian fronds, while the other forms occurred on a variety of other substrata (red algae, shells). There was also a notable difference in the male gonotheca. The morphotype with shallow hydrotheca had a broad, flattened male gonothecawith a distinct, recurved neck ( Fig. 13 G 1–G 3 ), while the other morphotype had a more tubular form and often lacked a neck ( Fig. 13B 1 , 13D1–13D2 ). Thus, in contradistinction to the opinion of Millard (1975), the South African material could nevertheless be composed of two distinct species, albeit with intergrading morphologies. However, not enough material, especially of the intermediate forms, has been analysed yet to allow a definitive conclusion. More detailed morphological, ecological and population genetic studies of the South African P. gaimardi are clearly needed.

Figures

FIGURE 1. Plumularia lagenifera, living colony from Friday Harbor, San Juan Islands (USA, WA). The height of the plumes is about 2–3 cm (voucher specimen MHNG-INVE-78966). The yellow bulbs along the stem are female gonothecae.

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 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.

FIGURE 12. Variability of microscopic structures of Plumularia gaimardi from South Africa. First row (A1–D1): stem segments and first hydrocladial segment. Second row (A2–D2): hydrothecate and ahydrothecate segments from the hydrocladia. Third row (A3–D3): abcauline walls of hydrothecae.

FIGURE 13. Variation of the gonothecae of Plumularia gaimardi, sex is indicated by symbols (♀ female, ♂ male).