Acryptolaria sp.

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 : 8-11

Acryptolaria sp. ( Fig. 3H , 5 D−E)

Material examined: Stn 98, one stem 5 mm high with a few hydrothecae, without coppinia, on the axis of a dead gorgonian ( NIWA 130063).

Description: Monosiphonic, incipient stem, 5 mm high, with six hydrothecae in a marked zigzag, arranged alternately in two planes forming an obtuse angle. Hydrotheca tubular, free part almost cylindrical, its diameter only slightly narrowing from aperture to where adcauline wall becomes adnate; more pronounced afterwards. Hydrotheca gently curved outwards. Hydrotheca adnate to internode for more than half its length. Free adcauline wall straight or slightly convex; adnate part initially convex, becoming roughly straight basally, forming a sort of bottleneck. Abcauline wall concave by the middle, practically straight at basal and distal thirds. Hydrothecal aperture circular, directed up- and outwards. Rim even, with up to four renovations.

Measurements (in µm): Hydrothecae: abcauline wall 770−850, free part of adcauline wall 310−450, adnate part of adcauline wall 510−530, adcauline wall 840−930, diameter at aperture 160−200, diameter at base 60−70. Cnidome (taken with × 40): large putative macrobasic mastigophores, range 14−17.5 × 7.5.

Remarks: The diameter of most hydrothecae gradually decreases in their adnate part until about the basal fourth, from where it remains approximately constant, forming a sort of basal bottleneck, much like that found in A. gracilis .

The present material agrees with Acryptolaria corniformis Naumov and Stepanjants, 1962 in having internodes in zigzag, in the general shape of the hydrotheca and in the size of the nematocysts. However, it differs in the size of the hydrotheca, which is significantly smaller in the present material (e.g., abcauline length 1600−1900 µm and diameter at aperture 320−400 µm in the holotype of A. corniformis , in Peña Cantero et al. 2007), although this could be related to the fact that the material studied here consists of an incipient stem with only six hydrothecae. All previously described material of A. corniformis consists of four stem fragments up to 20 mm long, and therefore knowledge of this species is incomplete ( Peña Cantero 2020). For example, in the material studied by Peña Cantero (2020), the smallest diameter at the hydrothecal aperture reached 270 µm, closer to that found in the present material. On the other hand, considerable variation in the size of the hydrotheca has been reported in some species of Acryptolaria , like Acryptolaria angulata ( Bale, 1914) and Acryptolaria bulbosa ( Stechow, 1932) ( Peña Cantero and Vervoort 2010) . However, it is important to highlight that the present material differs from the holotype of A. corniformis in other details. In the holotype, the branches are slightly zigzagged, whereas in the present specimen the zigzagging is more pronounced; the hydrotheca is smoothly curved outwards and the hydrothecal aperture is strongly directed upwards in A. corniformis , whereas in the present species the hydrotheca is more curved outwards and the aperture is less directed upwards. The scarcity of the available material and the differences indicated do not allow me to assign the present material with certainty to A. corniformis .

The present material is also similar to Acryptolaria gemini Peña Cantero and Vervoort, 2010 in the size and general shape of the hydrotheca. They differ because in A. gemini the branches are approximately straight, the adcauline wall of the hydrotheca is free for more than half its length and there is a sharp reduction in the hydrothecal diameter at the point where the hydrotheca becomes adnate.

The other species with a similar hydrothecal shape is Acryptolaria longitheca ( Allman, 1877) , but it has distinctly larger hydrothecae and nematocysts.

Ecology and distribution: Acryptolaria sp. was collected from Seamount 9 Hjort, south of Macquarie Island, at depths between 676 and 750 m.

Filellum liberum sp. nov. ( Figs. 6−8 ) urn:lsid:zoobank.org:act:F34F6C2C-4C39-41AB-82D2-AA22A527A87C

Lafoea tenellula – Watson, 2003: 156−157, fig. 6A–C.

Material examined: Stn 98, numerous hydrothecae and several coppiniae, growing on Eudendrium sp. (Holotype, NIWA 40962).

Etymology: The specific name liberum comes from the Latin adjective 'liberum' and refers to the fact that the hydrothecae of this species are completely free from the substrate.

Diagnosis: Hydrothecae erect, tubiform, straight, curved or winding, completely free; height highly variable and diameter distinctly increasing distally; a wide band of desmocytes present at their basal part. Aperture circular; rim even, flared, often with renovations. Coppinia a fence of unforked, distally open, protective tubes surrounding and arching over closely packed gonothecae. Gonotheca flask-shaped; aperture circular, on a short distal neck markedly widening distally. Cnidome consisting of microbasic euryteles.

Description: Stolonal colony growing on Eudendrium sp. Stolons giving rise to erect, tubiform, straight, curved or winding, completely free hydrothecae; height highly variable and diameter distinctly increasing distally. Hydrothecal aperture circular; rim even, flared, often with renovations, increasing in diameter distally. A wide band of desmocytes present at basal portion of hydrotheca.

Coppinia with a fence of protective tubes surrounding the closely packed gonothecae and arching over them, creating a protective chamber. Defensive tubes unforked, distally open, relatively large compared to gonothecae; adjacent protective tubes coalescent with each other for part of their basal length. Gonothecae tightly packed, flask-shaped; aperture circular, on a short distal neck markedly widening distally; gonothecal shape becoming irregular towards the vicinity of protective tubes.

Measurements (in µm): Hydrothecae: height 490–1170, height with renovations up to 1700, diameter at origin 50−100, diameter at aperture 150−190 (primary hydrotheca), diameter at aperture of lower-order hydrothecae 180−200. Gonothecae: height c. 200, diameter at aperture 30−50. Cnidome: microbasic euryteles, range 5.5−6.5 × 2.5−3.

Remarks: Coppinia forms a kind of nest, similar to that found in other species of the genus, with gonothecae surrounded by a fence of protective tubes arching over them. It can even form a disk-shaped structure around the stem of Eudendrium sp. , much like that described for Filellum antarcticum ( Hartlaub, 1904) ( Fig. 3A in Peña Cantero et al. 2004).

The position of the band of desmocytes at the base of the hydrotheca is quite variable; in the hydrothecae examined it started at a height between 170 and 300 µm from the origin of the hydrotheca. It is important to note that the desmocytes do not form a single narrow ring, but rather a band, with a width of 100 to 250 µm.

The presence of desmocytes, which might initially be thought to be related to the free condition of the hydrotheca, is not unique to the present species. I have re-examined material of Filellum magnificum Peña Cantero, Svoboda and Vervoort, 2004 from Peter I Island and found that desmocytes are also present, even in hydrothecae with an adnate part, occupying a wide area of the wall in contact with the substrate.

The hydrothecae show a wide variety of shapes, with some being completely straight, others gradually curved at the distal part and still others winding along their length. As mentioned above, the diameter of the hydrotheca increases significantly distally; for example, in one of the hydrothecae the diameter was 100 µm at the origin and 160 µm at the aperture, reaching even 200 µm at the aperture of a secondary hydrotheca.

The present material seems to be conspecific with the material, also from the area of Macquarie Island, assigned to Lafoea tenellula Allman, 1877 by Watson (2003). Filellum liberum sp. nov. is, however, different from L. tenellula . According to Allman (1877: 12) “Hydrothecae very minute, slightly curved, contracted below into a short thick peduncle”. In the present species there is no pedicel, and instead there is a continuum along the whole structure and the basal part is very variable, being quite wide in some hydrothecae, but very narrow in others. In addition, whereas Allman indicated that the hydrothecae in L. tenellula are slightly curved, their shape is very variable, from straight to sinuous, in Filellum liberum sp. nov. It is likely that Allman’s species was actually a stolonal form of Lafoea Lamouroux , probably Lafoea dumosa ( Fleming, 1820) . In fact, Allman himself stated that “the form of the hydrothecae resembles that of the hydrothecae of L. dumosa , but the whole hydroid is more minute and delicate.” The material ascribed to L. tenellula by Hirohito (1995) is clearly a Lafoea and differs markedly from both Watson’s and the present material. According to Hirohito (1995), the hydrotheca is similar to that of Hebella Allman but is distinguishable by the absence of a diaphragm.

In my opinion, the present species is conspecific with Watson’s material and clearly belongs to Filellum Hincks. Even when the genus Filellum is generally characterised by having hydrothecae partially adnate to the substrate, there are species with hydrothecae with a much reduced or even absent adnate part. Filellum bouvetensis Marques, Peña Cantero, Miranda and Migotto, 2011 has erect and almost completely free hydrothecae and Filellum magnificum Peña Cantero, Svoboda and Vervoort, 2004 is characterised by hydrothecae adnate to the substrate for only a tiny part; Peña Cantero (2010), for example, studied material with hydrothecae with a much reduced, or even absent, adnate part. Completely free hydrothecae have even been observed in Filellum antarcticum ( Hartlaub, 1904) ( Fig. 2D in Peña Cantero et al. 2004).

The characteristics of the new species, Filellum liberum sp. nov., make it necessary to propose the following diagnosis for the genus Filellum , with slight modifications from that presented by Marques et al. (2011).

Lafoeidae with young and adult colonies stolonal; hydrorhiza filiform, branched, creeping on substratum. Hydrorhizal stolons giving rise directly to hydrothecae. Hydrothecae tubular, either completely free from substrate or partially sessile; hydrotheca or distal free part directed upward to varying degrees and extension. Desmocytes present. Hydranth long, a distal whorl of filiform tentacles; hypostome short, dome-shaped. Hydrothecal diaphragm, hydrothecal operculum, nematothecae and nematophores absent. Gonophores as fixed sporosacs, in gonothecae forming coppiniae. Gonothecae either closely set, with lateral walls juxtaposed, or weakly aggregated, with gonothecae isolated. Coppinia with or without defensive tubes (modified hydrothecae). Cnidome consisting mainly of heterotrichous microbasic mastigophores and/or microbasic euryteles.

The presence of completely free hydrothecae in Filellum liberum sp. nov. may raise questions about the differences between Filellum and Lafoea , as stolonal colonies have also been described in Lafoea . In my opinion, there are enough differences between the two genera to distinguish them. In Filellum , both juvenile and adult colonies have an exclusive stolonal structure ( Marques et al. 2011), with coppiniae developing on the substrate on which the colony is growing. In Lafoea , colonies typically consist of erect, branched, polysiphonic stems, although occasionally juvenile colonies with a stolonal structure exist ( Millard 1975). Coppiniae are specifically associated with the erect, polysiphonic stems. It appears that stolonal colonies in Lafoea represent the initial stages in the formation of a typical colony with erect stems. According to Schuchert (2001), erect stems are simply older. This seems to be the case in other genera of the family ( Millard 1975), such as Acryptolaria Norman , where stolonal and pedicellate hydrothecae have been reported in several species, including Acryptolaria conferta ( Allman, 1877) ( Calder 1991) or Acryptolaria infinita Peña Cantero and Vervoort, 2010 and A. operculata ( Peña Cantero and Vervoort 2010) .

Filellum and Lafoea also differ in the presence of a pedicel. Hydrothecae in Lafoea are typically pedicellate, although the pedicel is sometimes absent in L. dumosa , in which case the hydrothecae are directly joined to the branch. In Filellum the hydrothecae are either partially sessile or completely free, but without a pedicel. Schuchert (2001: 69) stated about L. dumosa : “Even among colonies from the same locality, there are often very distinct morphotypes, mostly differing in size and shape of the hydrothecae, and presence or absence of a hydrothecal pedicel (comp. Fig. 54C). However, comparing enough material, all forms will ultimately intergrade and they are not objectively identifiable.” In Filellum there are no intergrading morphologies; the hydrothecae never show a pedicel. In fact, in L. dumosa , when the hydrothecae are sessile, it is because the pedicel is absent, as shown by the position of the desmocytes, located at the origin of the hydrothecae (see Fig. 3G in Peña Cantero and Horton 2017). In contrast, in Filellum liberum sp. nov. desmocytes are always far above the origin of the hydrothecae ( Fig. 6H ), even in hydrothecae that are relatively short and could be confused with sessile hydrothecae of Lafoea ( Fig. 6D ). Furthermore, as mentioned above, desmocytes form a broad band in Filellum liberum sp. nov., but a narrow ring in Lafoea .

There are also differences concerning the cnidome. The nematocysts of Lafoea species include small microbasic mastigophores ( Calder 2013; personal observations) and large isorhizas ( Schuchert 2001; Calder 2013; Peña Cantero and Horton 2017); the latter type is absent in Filellum species, where only microbasic mastigophores and/or microbasic euryteles are present ( Marques et al. 2011; Soto Àngel and Peña Cantero 2019). In Filellum liberum sp. nov. only microbasic euryteles were observed ( Fig. 7E–F ).

Ecology and distribution: Filellum liberum sp. nov. has been collected at depths from 500 to 1064 m ( Watson 2003); present material between 676 and 750 m. Coppiniae in January ( Watson 2003) and April (present material).

Filellum liberum sp. nov. has been found north, west and south of Macquarie Island ( Watson 2003). Present material was collected from Seamount 9 Hjort, south of Macquarie Island.

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. 5. Acryptolaria seamountensis sp. nov.: A−C, hydrothecae and hydrothecal disposition. Acryptolaria sp.: D−E, hydrothecal arrangement and shape of hydrothecae. Scale bar = 250 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.

Fig. 7. Filellum liberum sp. nov.: A, defensive tubes of coppinia; B−D, gonothecae; E, microbasic eurytele (arrow); F, discharged microbasic eurytele (arrow). Scale bars: A = 200 μm; B−D = 100 μm; E−F = 10 μm.

Fig. 8. Filellum liberum sp. nov.: A−C, hydrothecae; D, part of a coppinia showing gonothecae and defensive tubes. Scale bar = 250 µm.

Fig. 2. Types of hydrothecae found in the collection studied and their main morphological characters. Abbreviations: aad, adnate adcauline wall; ab, abcauline wall; ad, adcauline wall; aint, ahydrothecate intermediate internode; c, cusp; d, diaphragm; des, desmocytes; fad, free adcauline wall; ht, hydrotheca; int, internode; lnt, lateral nematotheca; mnt, medial infrahydrothecal nematotheca; n, node; nt, nematotheca; ped, pedicel; pr, perisarc ridge; r, rim; ren, renovation; stn, stolon.