Acryptolaria rectangularis ( Jarvis, 1922 )

Peña Cantero, Alvaro L., Marques, Antonio C. & Migotto, Alvaro E., 2007, Revision of the genus Acryptolaria Norman, 1875 (Cnidaria, Hydrozoa, Lafoeidae), Journal of Natural History 41 (5 - 8), pp. 229-291 : 263-265

Acryptolaria rectangularis ( Jarvis, 1922)

Cryptolaria rectangularis Jarvis 1922, p 335 , Plate 24 Figure 3 .

Acryptolaria rectangularis: Millard 1967, p 174 , Figure 2B (in part).

Acryptolaria angulata: Vervoort 1966, p 117 , Figure 17 .

Description

‘‘The material consists of a part of a colony 0.7 cm high and lacking both basal and distal portions. Fascicling tubes are few and limited to the proximal end of the stem. Branches are irregular, or perhaps opposite, and polysiphonic for a short distance beyond their origin. The hydrothecae are alternate, long and tubular, the proximal halves erect and adnate, the distal diverging at a right angle. The margin is smooth with several reduplications and circular aperture. A well-marked fold occurs in the lower wall of the hydrotheca at the point of divergence. Gonosomes absent’’ ( Jarvis 1922, p 335–336).

Remarks

Unfortunately, it has not been possible to examine type material of this species. According to Vervoort and Watson (2003), the location of the type material of Jarvis’ species is unknown.

The branches represented in Jarvis’ (1922) figures have a zigzag arrangement. According to Vervoort (1966, as A. angulata ) ‘‘The stems are erect and largely monosiphonic; there are some accessory tubes at the basal parts of some of the hydrocauli and some short hydrorhizal fibres’’.

As already noted, the species A. angulata , A. bulbosa , and A. rectangularis share similar hydrothecal morphology and may be phylogenetically closely related species. In fact, Acryptolaria rectangularis has been considered conspecific with A. angulata by several authors (e.g. Hirohito 1995; Vervoort and Watson 2003). Vervoort and Watson (2003, p 41), for example, indicated that they studied ‘‘great amount of material of this species [ A. angulata ] from all over its large area of distribution … has convinced us that Cryptolaria angulata Bale, 1914 and Cryptolaria rectangularis Jarvis, 1922 are inseparable’’.

We found, however, that the three species are different, although sharing similar hydrothecae. Acryptolaria angulata is characterized by the presence of the adcauline boss projecting into the hydrothecal cavity. Jarvis (1922) made it clear that A. rectangularis differs from A. angulata in the straightness of the upper wall of the hydrotheca, in its divergent portion, and in the absence of an internal thickening opposite the fold. Gravier- Bonnet (1979, p 18) followed the opinion of Jarvis (1922) and Millard (1967, 1968, 1975) that this species is clearly distinguishable from Bale’s species by the absence of the adcauline thickening of the hydrothecae. Schuchert (2003, p 155) also considered A. rectangularis and A. angulata as ‘‘separate species because both morphotypes were found not very far apart’’; but he acknowledges, however, ‘‘the possibility that both could be only forms belonging to the same species’’.

The presence of the adcauline boss projecting into the hydrothecal cavity is clearly a distinct character of A. angulata . On the other hand, the absence of this boss makes A. bulbosa and A. rectangularis morphologically similar. However, the shape of the hydrotheca of these two species seems to be slightly different. Stechow (1932) indicated that A. bulbosa differs from A. rectangularis mainly in the stronger bend of the hydrotheca, the smaller diameter of the hydrothecal aperture and the shorter free portion of the hydrotheca (cf. Table XV). These differences, though small, prevent us from considering the two species to be conspecific. In addition, the hydrotheca of A. bulbosa is similar to that of A. angulata , it distinctly bends upwards after the adcauline wall becomes free. By contrast, A. rectangularis has the free portion of the adcauline wall straight, the diameter of the hydrothecal aperture larger, and the free portion of the hydrothecal wall longer than in the other two species.

Possible misidentifications of A. rectangularis , especially by Millard (1967, 1968, 1980), Gravier-Bonnet (1979), and Schuchert (2003), are listed under the discussion of A. bulbosa . On the other hand, Vervoort (1966) assigned to A. angulata material belonging to Jarvis’ species. The material shares with A. rectangularis the shape and size of the hydrothecae and the absence of the adcauline notch so characteristic for Bale’s species.

Distribution

Acryptolaria rectangularis seems to be a bathyal species, having been found from depths between 225 ( Jarvis 1922) and 495 m ( Vervoort 1966). It is certainly known from the

western Indian Ocean, off Providence Islands ( Seychelles) and off Durban, east coast of South Africa ( Vervoort 1966; Millard 1967).

Figures

Figure 2. Acryptolaria angulata (Bale, 1914). (A–C) Hydrothecae. All drawings from the holotype. Scale bar: 400 Mm.

Figure 3. Acryptolaria bulbosa (Stechow, 1932). (A) Part of branch showing hydrothecal arrangement; (B–D) hydrothecae. All drawings from the holotype. Scale bar: 400 Mm.

Figure 17. Shape of hydrotheca in Acryptolaria. (A) A. abies; (B) A. angulata; (C) A. conferta; (D) A. corniformis; (E) A. crassicaulis; (F) A. flabellum. Scale bar: 250 Mm.