Cystonectae Polygastricae.

Pugh, P. R., 2019, A history of the sub-order Cystonectae (Hydrozoa: Siphonophorae), Zootaxa 4669 (1), pp. 1-91 : 49-51

Cystonectae Polygastricae. Family Epibulidae .

We come now to Haeckel’s (1888b) short-stemmed grouping of cystonects, the Brachysteliniae, which included the families Epibulidae and Physalidae . The species Epibulia was briefly discussed earlier and for all the descriptions Haeckel was the most muddled. In Haeckel (1888a) he consider the genus Epibulia to belong to the calycophoran family Diphyidae , and even established the Subfamily Epibulidae to include it, noting that the genus Epibulia was the same as Blainville’s Galeolaria , which currently is referred to as Sulculeolaria . Another diphyid subfamily was the Prayidae , which has long been known to be a distinct family. However, in his Challenger Report Haeckel (1888b, p. 151) remarked that the genus Galeolaria had been: “confounded by later authors with Epibulia ”, apparently forgetting that he was one of them. He again placed the genus in its own family, the Epibulidae , but now returned it to its original placed amongst the cystonect siphonophores. He (ibid, p. 332) defined the family as: “ Cystonectae polygastricae with a short inflated trunk of the vesicular siphosome, which is spirally convoluted beyond the basal side of the large subvertical pneumatophore. Cormidia ordinate in a spiral ring, protected by a corona of palpons. Pneumatosaccus without radial septa and pericystic radial pouches, but with eight or more radial groups of hypocystic villi”. He included two genera Epibulia and Angela , for the species A. cytherea Lesson. He devoted just twelve lines to the latter genus, in which he noted that the tentilla were trifid, which is a classic character for species of the genera Agalma , Athorybia and Melophysa . Bigelow (1911) considered Lesson’s species in some detail and concluded that it belonged to the physonect family that he called the Anthophysidae . Indeed, there can be very little doubt that, despite the poorness of the illustration the species name cytherea is a junior synonym of Athorybia rosacea ( Forsskål, 1775) , which currently is included in the physonect family Agalmatidae (see Pugh, 2006); and so need not concern us any further.

Within the genus Epibulia Haeckel (1888b) included Epibulia chamissonis Eysenhardt and E. erythrophysa Brandt but, as noted above, despite Haeckel’s statement that he saw the original manuscript drawing of Mertens, those drawings remain unpublished and so that species name must be treated as a nomen nudum. As Haeckel also had what he identified as an Epibulia specimen, collected off Sri Lanka, of course he described it as a new species, E. ritteriana Haeckel , and illustrated it in his Plate XXII (see Figure 24A ). Like so many of Haeckel’s illustration, this is a work of art but, as always, the question remains as to just how accurate was it? As noted above, Haeckel keenness to find intermediary species was also applied to Epibulia , which he considered to be a prime example of an intermediate between the Physaliidae and the Rhizophysidae .

Haeckel (1888b), in his comparatively lengthy (88 lines) description of Epibulia ritteriana , spent a great deal of space (40%) describing the pneumatophore with its hypocystic villi that, as Haeckel noted, were also found in his Rhizophysidae . The critical part of the description, however, is the description of the siphosome. Haeckel considered that this was made up by 40–60 palpons, as well as many young buds. He counted eight “cormidia” of which “four siphons and tentacles, and four large gonodendra were fully developed, two others (smaller) half developed, and two very small and young” (ibid. p. 335). By dividing the number of palpons by the number of “cormidia”, he suggested that each “cormidium” bore 6–10 palpons. However, despite the fact that he himself had captured the specimen and watched its “vivid motions”, he noted (ibid.): “Unfortunately, I was not able to examine closely the form of the central trunk of the siphosome, and the mode of attachment to the cormidia; probably it is similar to that of the Anthophysidae , Discolabidae, and Nectalidae; all that I could observe of the trunk was that it represented a shortly conical or ovate bladder, coiled up in a spiral, with a single dexiotropic turning”. Thus once again it appears that we were being given pure speculation rather than hard fact.

Schneider (1898), rather mysteriously, retained Epibulia erythrophysa , which must be considered as a nomen nudum, as the only species of the genus and synonymised Haeckel’s E. ritteriana with it, on the rather dubious grounds that they both came from the Indo–Pacific. He thought that E. chamissonis probably also belonged to the genus. He suggested that Haeckel’s description should be interpreted with some caution as Haeckel was describing features not known in cystonect species, i.e. stem palpons. Further, he noted that the descriptions of the pneumatophore, tentacles and genital clusters also equally applied to Rhizophysa species. However, Bigelow (1911, p. 320) considered that: “one species, E. ritteriana Haeckel , from the Indian Ocean, has been carefully described and beautifully figured. Two others from the Pacific, E. (Rhizophysa) chamissonis Eysenhardt , the type, and E. erythrophysa Brandt , are known, but from such incomplete accounts that their relationship to Haeckel’s form remains doubtful”.

Stepanjants (1967) retained all three species in her systematic list (see below), but otherwise made no mentioned of the genus. Totton (1965, p. 44) wrote of the “? Epibulidae Haeckel, 1888 ” that the chief characteristic was the presence of a ring of palpons below the pneumatophore so that (ibid.): “it seems best to regard these animals, if they exist, as forming a quite separate family Epibulidae Haeckel ”. He included both E. chamissonis and E. ritteriana , and for the latter he was (ibid.): “not satisfied of the existence of a siphonophore such as was figured by Haeckel. If it was indeed a cystonect it could hardly have a ring of palpons under the float. The description is incomplete and unconvincing. It seems possible that Haeckel had worked up notes and sketches of an incompletely examined specimen of Athorybia rosacea ”. Indeed, Totton included as a synonym of E. ritteriana “? Athorybia rosacea (Forskål) 1775 ”. However, that seems to be a rather strange conclusion and perhaps Totton was actually thinking of the other species, Angela cytherea . It is also strange that Totton, who must have studied several specimens of Rhizophysa filiformis during his visits to Villefranche-sur-Mer, appeared not to have noticed the fact that in that species the youngest gastrozooids, close to the pneumatophore, have yet to develop their tentacles; the buds of which gradually appear and enlarge as the gastrozooids move posteriorly in accordance with the growth of the stem. The reason for the presence of the so-called palpons would then become apparent. They are nothing more than young gastrozooids. Daniel (1974, p. 33) also elucidated this point when she said: “As pointed out by Totton … the species of the family Epibuliidae will have to be treated as species inquirendae. The alleged presence of ‘palpons’ below the float may be really young gastrozooids, for if it were really palpons this family may have to be removed from the Suborder Cystonectae and placed before the Suborder Physonectae ”.

Since Totton’s (1965) Synopsis, Alvariño (1972) reported the second record for Epibulia ritteriana ( Figure 24B ), from off California, and gave a “description” of the specimen. This description is remarkable for the fact that it reads almost exactly as though it had been copied directly from that of Haeckel (1888), as follows:

Alvariño (1972) “The pneumatophore is an ovate chitinous case, 8 mm x 10 mm in size. According to Haeckel (1888) the size of the pneumatophore ranged from 10 mm x 12 mm in the expanded stage to a spheroid of 3 to 4 mm after the emission of the gas through the apical pore. The structure of the pneumatophore, according to Haeckel (1888) in- cludes the pneumatocodon or outer wall of the pneumato- phore, which is separated from the inner wall, or pneu- matosac, pneumatocyst or air sac, which contains the gas gland; and the hypocystic villi (giant cells) protrude from the air sac into the pericystic space. The apical pore is closed by the stigmatis sphicter [sic] (ring muscle).

"The palpons (feelers or testers) are slender, cylindrical tubes, smaller than the siphons, with a thick muscular wall. They connect into the vascular trunk, and the outer end is armed with cnidocysts. The palpons are conse- quently then both sensory and protective organs.

"The siphons or gastrozoids [sic] are large ... rod-shaped tubes of thick muscular wall.

"The largest part is the stomach with the hepatic villi, and the outer opening a muscular proboscis. The opening of the mouth may be expanded in a kind of disc or sucker, divided into several lobes.

"The tentacle arising from the base of each gastrozoid [sic] consists of a long cylindrical tube reaching to 80 mm or more than 100 mm long when fully extended.

"The concave side of each tentillum has sensitive papil- lae, and the convex side is armed with cnidocysts.

"The gonodendra are attached by a short pedicle to the periphery of the vesicular trunk, between the palpons and the siphons or gastrozoids [sic]. The gonostyle is branched, and each branch has at the end a gonopalpo [sic] and a medusoid gynophore (female gonophore) and below a bunch of roundish androphores (male gono- phores). "

Haeckel (1888b) “The great float filled with air is ovate, and has a diameter of 10 to 12 mm. in the expanded state; in the contracted state, however, after the emission of gas through the apical pore, it represented a depressed spheroid of 3 to 4 mm. only. The pneumatocodon or the outer wall of the pneumatophore is separated from the inner wall, or the pneumatosaccus, by a wide cavity. This pericystic cavity opens below into the stemcavity of the siphosome, whilst it is closed above, surrounding like a ring the apical pore where both walls are connected. The distal or inferior half of the pericystic cavity is filled by the numerous finger-shaped hypocystic villi, arising in eight radial bunches from the airfunnel.

"The palpons are slender, very movable, cylindrical tubes with a thick muscular wall. Their cavity opens at the proximal end into the vesicular trunk, whilst the closed distal end is armed with cnidocysts and a purple ocellus. Their function is not only sensory, but also protective and capturing.

"Siphons [are] ... spindle-shaped tubes with a thick muscular wall.

"The largest part is the dilated stomach, covered inside with numerous yellow hepatic villi. The distal proboscis is very muscular; its mouth-opening may be expanded in the form of a circular suctorial disc, the margin of which is divided into sixteen lobes.

"The single tentacle which arises from the base of each siphon is a long cylindrical tube, in the fully expanded state 80 to 120 mm. long or more.

"The concave ventral side of the tentilla bears sensible papillae; the convex dorsal side is armed with spherical cnidocysts.

"Gonodendra [are] attached by a short pedicle to the periphery of the vesicular trunk, between the superior palpons and the inferior siphon. The gonostyle is richly branched, and each ultimate branch ... bears a large, distal, medusiform gynophore and a bunch of club-shaped androphores with small gonopalpons scattered between them." Thus, there appeared to be no new observations in Alvariño’s description, and the only difference from that of Haeckel is that she, probably inadvertently, at one point equated the palpons with young gastrozooids.Alvariño also gave a presentation concerning this species at the Third International Conference on Coelenterate Biology, which took place in Victoria, B.C. in 1976. She showed some photographs of the specimen and both Dr. D.C. Biggs and myself were present and were immediately convinced that what we were seeing was a highly contracted Rhizophysa species. Thus we contend that Epibulia species are merely young, highly contracted specimens of a Rhizophysa . Because of the pink and red pigmentation and the simple, filiform nature of the tentilla, the most obvious candidate for both Eysenhardt’s (1821) E. chamissonis and Haeckel’s (1888b) E. ritteriana is R. eysenhardtii . However, personal observations (see below) have shown that the young gastrozooids of R. eysenhardtii quickly develop their tentacles, so that the sixth gastrozooid from the zone of proliferation has a well-developed one. In contrast, for R. filiformis the first 30 developing gastrozooids have no sign of a tentacle. This again raises the question, possessed above, as to whether all R. eysenhardtii specimens are red and R. filiformis ones green. Nonetheless, the large number of palpons, i.e. young gastrozooids, illustrated by Haeckel for E. ritteriana should be put down to the artistic licence that Haeckel (ab)uses all too often. It is concluded that there is no reason to continue to consider the family Epibuliidae , including its genera and species, as having any validity.

Figures

FIGURE 24. Epibulia ritteriana. A. Reproduced from Haeckel (1888) Plate XXII (partim). B. Adapted from Alvariño (1972, fig. 1). Scale bar 5 mm.