Acryptolaria seamountensis, Cantero, 2024

Cantero, Álvaro Luis Peña, 2024, Fig. 4 in Positive association between PTN polymorphisms and schizophrenia in Northeast Chinese Han population., Zoological Studies 63 (17), pp. 141-149 : 6-8

Acryptolaria operculata Stepanjants, 1979 ( Fig. 3B )

Acryptolaria operculata – Peña Cantero et al., 2007: 258–261, figs. 12, 16D, 18D, 19E; Peña Cantero, 2020: 288−291, figs. 1E, 6B, 7E.

Acryptolaria patagonica – Watson, 2003: 162−163, fig. 12A–C.

Material examined: Stn 71, one stem fragment 11 mm long with several hydrothecae, without coppinia, in bad condition ( NIWA 114754).

Description: Stem fragment 11 mm long, with two short lateral branches. Hydrothecae arranged alternately in two planes forming an obtuse angle. Hydrotheca markedly curved outwards, fusiform, largest diameter at the middle; diameter barely decreasing toward aperture, more noticeably basally at adnate part. Hydrotheca adnate to internode for around half its length. Adcauline wall convex. Abcauline wall concave. Hydrothecal aperture circular, directed up- and outwards; rim even, with a few short renovations.

Measurements (in µm): Hydrothecae: abcauline wall 1400, free part of adcauline wall 900−950, adnate part of adcauline wall 700−1050, adcauline wall 1650−1970, diameter at aperture 330−340, diameter at base 180−190. Cnidome (taken with × 40): putative macrobasic mastigophores, 15 × 6.

Remarks: Although scarce, the material examined undoubtedly corresponds to A. operculata (for recent descriptions, see Peña Cantero et al. 2007; Peña Cantero 2020). This species is well characterised by the shape and large size of the hydrotheca and the small size of the nematocysts (e.g., 14–15 × 4.5–5.5 µm in Peña Cantero 2020). In terms of hydrotheca size, the material studied here is closer to that of Peña Cantero (2020) from the Tasman Sea, with hydrothecae significantly smaller than his material from the southwest Atlantic.

Ecology and distribution: The species has been collected at depths between 98 ( El Beshbeeshy 2011) and 4740 m ( Peña Cantero 2020); present material was gathered from depths of 488 to 542 m.

Acryptolaria operculata is mainly distributed in sub-Antarctic waters, although it penetrates into Antarctic waters along part of the Scotia Arc ( Peña Cantero 2020). It has been reported in sub-Antarctic waters of the southwest Atlantic: the Patagonian shelf ( Stepanjants 1979; El Beshbeeshy 2011), the Burdwood Bank ( Soto Àngel and Peña Cantero 2015), and the area between Staten Island (Tierra del Fuego), the Falkland Islands and South Georgia ( Peña Cantero 2020). In the sub-Antarctic waters of the Pacific it has been documented in the Macquarie region ( Watson 2003), New Zealand waters ( Vervoort and Watson 2003) and the Tasman Sea ( Peña Cantero 2020). It is also known from Antarctic waters of the Scotia Arc, from Shag Rocks to Discovery Bank ( Soto Àngel and Peña Cantero 2015). Present material was collected from Seamount 6, north of Macquarie Island.

Acryptolaria seamountensis sp. nov. ( Figs. 3 C−G, 4A, 5A−C) urn:lsid:zoobank.org:act:795B3DE1-6785-4708-8C7D-3B72F08ACD79

Material examined: Stn 63, a complete stem 65 mm high, without coppinia (Holotype, NIWA 40133) and several stem fragments up to 50 mm long (Paratype, NIWA 126561).

Etymology: The specific name seamountensis is formed with the Latin adjectival suffix –ensis to indicate that the species originates from a seamount on the Macquarie Ridge.

Diagnosis: Stem polysiphonic, frequently branched. Branches practically straight. Hydrotheca cylindrical, smoothly curved outwards; adcauline wall convex, adnate over three-fourths of its length; abcauline wall concave towards the middle, practically straight at basal and distal thirds. Aperture directed outwards and upwards. Cnidome consisting of large macrobasic mastigophores and small microbasic mastigophores.

Description: Stem up to 65 mm high. Branching frequent, at least of fifth order. In some parts of the colony, mainly distal, branches alternate every third hydrotheca (i.e., there are two hydrothecae between branches) and slightly disposed in two planes. Branching more irregular at basal parts (probably due to loss of branches). Branches practically straight.

Hydrothecae alternate, in one or two planes forming a very obtuse angle. Hydrotheca cylindrical; diameter constant, slightly narrowing in basal part. Hydrotheca smoothly curved outwards; adcauline wall convex throughout, adnate to internode over three-fourths of its length (adnate/free ratio 2.6−3.6); abcauline wall concave towards the middle, practically straight at basal and distal thirds. Hydrothecal aperture circular, directed upwards and outwards. Rim even, often with a few short renovations.

Measurements (in µm): Hydrothecae: abcauline wall 740−900, free part of adcauline wall 160−420, adnate part of adcauline wall 630−820, adcauline wall 900−1150, diameter at aperture 160−210, diameter at base 80−120. Cnidome: large putative macrobasic mastigophores, 23.8 ± 1.0 × 11.7 ± 0.7 (n = 12), range 22−26 × 10.5−13, small putative microbasic mastigophores 8 × 4.

Remarks: The present material cannot be assigned to any of the known species of the genus and it is therefore considered a new species to science.

Acryptolaria seamountensis sp. nov. is similar to Acryptolaria minima Totton, 1930 in the shape of the hydrotheca, almost completely cylindrical, with its diameter only slightly decreasing at the basal part, and with the aperture directed outwards and upwards. However, the hydrotheca is much smaller in A. minima , about half the size of the present species (e.g., abcauline length 392–480 µm or diameter at aperture 120−136 µm, in the holotype of A. minima , in Peña Cantero et al. 2007). On the contrary, nematocysts are slightly longer and thinner (25.8 ± 0.8 × 9.8 ± 0.4, 25−27 × 9−10). Furthermore, in A. minima the abcauline wall is slightly convex at the basal part, with a clear discontinuity with the previous internode ( Fig. 6 A−B in Vervoort and Watson 2003 and Fig. 16B in Peña Cantero et al. 2007), whereas in Acryptolaria seamountensis sp. nov. the abcauline wall is straight, and essentially a prolongation of the preceding internode. Finally, Totton’s species is characterized by having hydrothecae almost completely adnate to the branch (about four-fifths of their adcauline length are adnate to the internode), whereas in the present species a greater proportion of the adcauline wall is free. Vervoort and Watson (2003) assigned to A. minima material from Sta. BS 756 that differed from their remaining material, including type material, by “the slightly longer hydrothecae, the greater length being principally due to the longer free hydrothecal portion” ( Vervoort and Watson 2003: 48). Their figures and measurements are in agreement with the present species. However, without information about the cnidome it is not possible to assign it to Acryptolaria seamountensis sp. nov.

The present species is also morphologically close to Acryptolaria bathyalis Peña Cantero and Vervoort, 2010 in the general shape of the hydrotheca: cylindrical, with a constant diameter throughout, decreasing only at its base. However, the species are clearly distinguishable because in A. bathyalis , the hydrotheca is markedly curved outwards and, therefore, the hydrothecal aperture is roughly parallel to the long axis of the branch, whereas in Acryptolaria seamountensis sp. nov., the hydrotheca is less bent and, consequently, the aperture is clearly directed upwards. In addition, the hydrothecae in A. bathyalis are smaller (e.g., abcauline length 680−770 µm) and the nematocysts are shorter and thinner (21.6 ± 0.8 × 8.5 ± 0.4 µm) ( Peña Cantero and Vervoort 2010).

Finally, Acryptolaria seamountensis sp. nov. agrees with the holotype of Acryptolaria gracilis ( Allman, 1888) in the size of hydrothecae and nematocysts (23.5−26 × 9 µm), although Peña Cantero et al. (2007) were able to take measurements of only two nematocysts from the holotype. However, the shape of the hydrotheca is clearly different due to the absence in the present species of the characteristic basal bottleneck described from the holotype of A. gracilis . According to Peña Cantero et al. (2007: 250) “Hydrotheca tubular, cylindrical at distal half, diameter approximately constant from hydrothecal aperture to the middle of hydrothecal length, then slightly decreasing up to become more or less constant, forming a kind of bottleneck at the most basal part.”

Ecology and distribution: Acryptolaria seamountensis sp. nov. was collected from Seamount 6, north of Macquarie Island, at depths between 350 and 560 m.

Figures

Fig. 3. Acryptolaria minuta Watson, 2003: A, hydrothecae. Acryptolaria operculata Stepanjants, 1979; B, distal part of hydrotheca. Acryptolaria seamountensis sp. nov.: C−F, hydrothecae and hydrothecal disposition; G, putative macrobasic mastigophore (arrow). Acryptolaria sp.: H, hydrothecae and hydrothecal disposition. Scale bars: A−F, H = 200 μm; G = 10 μm.

Fig. 6. Filellum liberum sp. nov.: A−G, different shapes of hydrothecae; H, broken hydrotheca showing desmocytes (arrow). Scale bars: A−G = 200 μm; H = 100 μm.