Acryptolaria tetraseriata, Peña Cantero & Vervoort, 2010

Peña Cantero, Álvaro L. & Vervoort, Willem, 2010, Species of Acryptolaria Norman, 1875 (Cnidaria, Hydrozoa, Lafoeidae) collected in the Western Pacific by various French expeditions, with the description of nineteen new species, Zoosystema 32 (2), pp. 267-332 : 321-323

Acryptolaria tetraseriata n. sp.

( Figs 28 ; 30 ; 32K ; Table 29)

MATERIAL EXAMINED. — Philippines. MUSORSTOM 3, stn DR 117, 12°31.2’- 12°31.3’N, 120°39.3’- 120°39.5’E, 92-97 m, 3.VI.1985, 1 stem c. 100 mm high, holotype (MNHN-Hy.2009-0174) ; 1 incipient stem c. 13 mm high, paratype (RMNH-Coel. no. 31529).

ETYMOLOGY. — The species name tetraseriata refers to the arrangement of the hydrothecae in four longitudinal rows, “tetra” being the Greek numeral four alluding to the number of series in which the hydrothecae are arranged.

ECOLOGY AND DISTRIBUTION. — Acryptolaria tetraseriata n. sp. was collected at a depth of 92-97 m in the Philippine region.

DESCRIPTION (BASED ON HOLOTYPE)

Main stem c. 100 mm high, very distinct, straight, pinnate, regularly giving rise at approximately the same interval to primary branches, alternately arranged in one plane, following a sub-opposite pattern ( Fig. 32K ); the first two primary branches are opposite. Primary branches also straight and roughly of same development, though slightly shorter and less developed at distal part of stem, perpendicular to main stem or slightly directed upwards, forming an angle of c. 70° with long axis of stem, but sometimes, particularly in the distal part, reaching 45°. In their turn the first-order branches give rise to short, much less developed and mostly monosiphonic, secondary branches. There may be anastomoses. Branches straight ( Fig. 28 ).

Hydrothecae arranged in alternate decussate pairs, forming four longitudinal rows ( Fig. 28A ). In some secondary branches that arrangement may become lost because hydrothecae there are alternately arranged in two planes that form an angle of c. 90° with each other ( Fig. 28B ). Hydrotheca tubular, roughly fusiform ( Fig. 28 ) with a diameter slightly increasing from aperture to approximately midlength, after which it decreases slightly basally; minimum diameter at the base. Operculum frequently present. Hydrotheca strongly curved outwards, with a distinct inflection point where it becomes free. Adcauline wall adnate over half its length (adnate/free ratio 1.4), slightly convex in both adnate and free portions; abcauline wall concave. Hydrothecal aperture circular and directed outwards, either parallel to long axis of branch or slightly facing upwards; rim even but slightly everted, frequently with renovations. Hydrothecae moderately immersed into the branches, with distinctly marked “step” at the origin of the abcauline wall, affecting the communication between the interior of hydrotheca and branch which from “vertical” has become “lateral”.

Large nematocysts relatively very large and fusiform ( Fig. 30 ).

Coppinia not observed.

REMARKS

Our material is undoubtedly allied to A. tortugasensis Leloup, 1935 . There are, however, a few differences that prevent us, at present, to refer our material to that species.One of the most remarkable differences is the absence in our material of the characteristic internal abcauline perisarc cusp, in about the middle of the abcauline wall, of Leloup’s species. Although the presence of internal cusps has been demonstrated to be a variable character in certain species of other genera (e.g., Sertularella Gray, 1848 ), where those cusps are associated with the hydrothecal rim, the presence of internal cusps in species of Acryptolaria is exceptional, as it is only known in A. tortugasensis . Consequently we consider its presence an important diagnostic character.

In addition, although our material share with A. tortugasensis the subopposite branching pattern, some primary branches in Leloup’s species become much developed, acting as secondary stems, so that the degree of branching is high, whereas in our material the stem is clearly pinnate with all primary branches reaching more or less the same development. There is also difference in hydrothecal disposition, because in our material the hydrothecae form four longitudinal rows, being arranged in alternate decussate pairs, though this pattern may become less evident or even lost in the secondary branches, where the hydrothecae can be alternately arranged in two planes making a right angle and form only two longitudinal rows of hydrothecae as also happens in A. tortugasensis . Although they agree in the general shape and size of both hydrothecae and nematocysts, there are slight differences in these aspects too: the nematocysts in our material are slightly longer and the hydrothecae have a distinctly longer free adcauline part (cf. Table 31). In our material the abcauline hydrothecal wall is smoothly concave but in A. tortugasensis there is a slightly marked inflection point near the abcauline cusp, the hydrotheca being more abruptly directed outwards. Finally, there are also biogeographical reasons to keep both species separated, since A. tortugasensis is known from Tortugas, Florida, USA.

The distinct step found at the bottom of the hydrotheca is very characteristic, being only present in A. tortugasensis and in less-developed condition in A. medeae n. sp. This step sets off the abcauline hydrothecal wall from the branch, contrary to the other species of the present genus, where the basal part of the abcauline wall is either parallel to the branch or becomes gradually separated.The presence of that strong discontinuity has another important consequence. Contrary to the other species of Acryptolaria , in which the communication between the lumina of hydrotheca and branch occurs perpendicular to the long axis of branch, between the adcauline and the abcauline walls of the hydrotheca, in our material it takes place parallel to that axis, under the adcauline hydrothecal wall.

Figures

FIG. 28. — Acryptolaria tetraseriata n. sp., from MUSORSTOM 3 stn DR 117, branch fragments showing hydrothecal arrangement and hydrothecae. Scale bar: 250 μm.

FIG. 30. — Outline drawings of the large type nematocysts of Acryptolaria species discussed in the present report. Scale bar: 30 μm.

FIG. 32. — Colony shape and branching in Acryptolaria Norman, 1875: A, A. longitheca (Allman, 1877), from MUSORSTOM 6 stn DW 407; B, A. medeae n. sp., holotype,MUSORSTOM 4 stn CP 195; C, A. niobae n. sp., holotype,BIOCAL 1 stn DW 08; D, A. norfolkensis n. sp., holotype, BIOCAL 1 stn DW 36; E, A. novaecaledoniae n. sp., holotype, MUSORSTOM 6 stn DW 422; F, A. profunda n. sp., holotype, MUSORSTOM 6 stn DW 422; G, A. pseudoangulata n. sp., holotype, MUSORSTOM 4 stn CP 217; H, A. pseudoundulata n. sp., holotype, MUSORSTOM 6 stn DW 457; I, A. pulchella (Allman, 1888), from MUSORSTOM 3 stn DR 117; J, A. pygmaea n. sp., holotype, SMIB 4 stn DW 60; K, A. tetraseriata n. sp., holotype, MUSORSTOM 3 stn DR 117; L, A. undulata n. sp., holotype, BIOCAL 1 stn DW 66. Scale bars: A, C, F-I, 10 mm; B, D, E, K, 20 mm; J, L, 5 mm