Nemertesia macquariensis, 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 : 19-22

Family Plumulariidae McCrady, 1859 Nemertesia macquariensis sp. nov. ( Figs. 4B , 11−12 )

urn:lsid:zoobank.org:act:45EE4511-7F5E-47E1-9865-CDAAD4D4055B

Material examined: Stn 63, one stem 120 mm high, without gonothecae (Holotype, NIWA 40094) and four stems up to 170 mm high, without gonothecae (Paratype, NIWA 144254); Stn 71, two stems, 180 and 130 mm high, without gonothecae ( NIWA 40351).

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

Diagnosis: Stems polysiphonic, planar, frequently branched. Hydrocladia on cauline apophyses arranged in decussate pairs, not at right angles, resulting in four longitudinal rows; apophyses with one mamelon (two also observed), two axial nematothecae and another pair more above mamelon. Hydrocladia divided into alternating hydrothecate and ahydrothecate internodes, starting with a hydrothecate internode. Ahydrothecate internode with a basal nematotheca. Hydrothecate internode with one hydrotheca in the middle and three nematothecae: two flanking hydrothecal aperture, and one mesial infrahydrothecal nematotheca not reaching hydrothecal base. Internode with strongly developed perisarc ridges. Hydrotheca low, about as high as wide; abcauline wall straight, directed outwards. Hydrothecal aperture circular, slightly tilted adcaudally; rim even. Nematothecae with scooped rim. Paired nematothecae of hydrothecate internodes similar to infrahydrothecal ones.

Description: Stems strongly polysiphonic, branched, up to 180 mm high and 5 mm in diameter at base. Hydrorhiza disc-shaped or rhizoidal. Stems deprived of branches for a large basal part. Branching in one plane, rather irregular, alternate in some places, sub-opposite in others; branches up to sixth order, arising from accessory tubes. Hydrocladia originating from cauline apophyses arranged in decussate pairs in X (i.e., not at right angles), giving rise to four longitudinal rows. Branches divided into internodes by straight transverse nodes, with variable number of hydrocladia per internode. Hydrocladia with up to fourteen hydrothecae. Cauline apophyses with one mamelon (two also observed), two axial nematothecae and another pair more above mamelon.

Hydrocladia divided into internodes by oblique nodes, alternately hydrothecate and ahydrothecate, starting with a hydrothecate internode. Ahydrothecate internode with a basal nematotheca resting on upper side of basal swelling of internode.

Hydrothecate internode with one hydrotheca resting approximately in the middle of internode and three nematothecae: two lateral, flanking hydrothecal aperture, and one mesial infrahydrothecal resting on basal swelling of internode and not reaching hydrothecal base. Internode with strongly developed perisarc ridges: one before mesial nematotheca, one in the middle between mesial nematotheca and hydrotheca, one at base of hydrotheca, one just above hydrothecal aperture and a fifth before distal node (a sixth ridge present in some internodes just above mesial nematotheca). Ahydrothecate internodes typically with two perisarc ridges, one basal and one distal.

Hydrotheca low, about as high as wide. Abcauline wall straight, directed outwards. Hydrothecal aperture circular, slightly tilted adcaudally; rim even.

Nematothecae bithalamic; distal chamber with scooped rim. Paired nematothecae of hydrothecate internodes similar to infrahydrothecal nematothecae.

Measurements (in µm): Cauline apophyses: length 300–350. Hydrothecate hydrocladial internodes: length 330−350, diameter at hydrothecal base 75–105. Ahydrothecate hydrocladial internodes: length 180−200. Hydrotheca: abcauline length 60–90, adcauline length 50–65, diameter at aperture (frontal view) 70–90. Lateral nematotheca: height 80−85, diameter at aperture 50−60, diameter at diaphragm 30, height of distal chamber 20. Mesial nematotheca: height 70, diameter at aperture 45−50, diameter at diaphragm 30, height of distal chamber 20−25.

Remarks: The colonies are strongly polysiphonic, except for the most distal, lowest-order branches.

The internodes of stems and branches are very variable in length (some have only one pair of hydrocladia, but others up to five pairs), probably because they are just the result of growth interruptions, as is also indicated by the decrease in diameter (e.g., from 200−210 µm at the first internode to 170−180 µm at distal one).

As mentioned above, hydrocladia originate from cauline apophyses arranged in decussate pairs which are not at right angles. Lower-order branches typically originate in the narrower sides of the X and, as a result, it is possible to observe a bilateral symmetry in the colonies, with the hydrocladia and branches confined to the laterals, and the anterior and posterior parts devoid of them, giving rise to the final planar structure of the colony.

As previously stated, branching is in one plane, but is quite irregular. In some parts of the colony it appears to be alternate, with branches widely separated, but in other parts the branches are close together and then appear to form sub-opposite pairs, yet in other parts the alternate order is reversed.

Branches, or lower-order stems, arise from accessory stolons and start with an apophysis, which may be followed by an intermediate athecate internode, and a first internode with hydrocladia at different levels and positions. The following internode already has apophyses with more or less the typical arrangement.

In the general colony shape, Nemertesia macquariensis sp. nov. is allied to Nemertesia pinnatifida Vervoort and Watson, 2003 , which has a fanshaped colony with all branches and the main stem in one plane. They also share the heteromerous division of the hydrocladia, starting with a hydrothecate internode. However, they differ in several aspects.

In N. pinnatifida the secondary or lower-order branches are quite short (10−20 mm long) and pinnately arranged in close opposite or sub-opposite pairs, whereas in the present species branches are longer (30 mm long) and, as mentioned above, branching is quite irregular. In N. pinnatifida , the number of longitudinal rows of apophyses is quite irregular, whereas in Nemertesia macquariensis sp. nov. the apophyses are arranged in decussate pairs in X and, consequently, the number of longitudinal rows is always four.

The number of associated nematothecae on the cauline apophyses is higher in N. pinnatifida (5 to 6). According to Vervoort and Watson (2003: 284), “1 or a pair may occur in the axil, 1 halfway mamelon, 1 or a pair above mamelon, and 1 on slight elevation almost at end of apophysis”. In Nemertesia macquariensis sp. nov. there are four nematothecae, one pair at the axil and another pair above the mamelon.

The nematothecae in N. pinnatifida are significantly longer (height 67−100 µm) than in the present species, whereas the hydrothecae are smaller (abcauline length 34−45 µm, in Vervoort and Watson 2003). As a result, the nematothecae are very long compared to the hydrothecae in N. pinnatifida . In addition, the hydrotheca is located in the middle of the internode in the present species, whereas it is clearly below the middle in N. pinnatifida .

The species also differ in the development and number of the perisarc ridges of the hydrothecate internodes. In N. pinnatifida , there are incomplete septa at both ends of the internode, just above the insertion of the median inferior nematotheca and at the base of the hydrotheca. In Nemertesia macquariensis sp. nov., the perisarc ridges are more developed and more numerous.

Nemertesia macquariensis sp. nov. shares w i t h N e m e r t e s i a c y m o d o c e a (B u s k, 1 8 5 1), t h e polysiphonic, branched stems, and the structure of the hydrocladial apophyses. They differ because in N. cymodocea the cauline apophyses are usually arranged in decussate verticils of three or four apophyses, although decussate pairs are also found in younger parts of the colony ( Ramil and Vervoort 2006); in Nemertesia macquariensis sp. nov., however, there are only decussate pairs arranged in X. They also share the heteromerous division of the hydrocladia into internodes with alternating hydrothecate and ahydrothecate internodes. However, they differ because in N. cymodocea the first hydrocladial internode is ahydrothecate, whereas in the present species it is hydrothecate. The colony structure is also completely different, with the stem provided with long branches arising just above the base and the branches rebranching basally into long upwardly directed shoots in N. cymodocea ( Vervoort and Watson 2003) . Finally, there are biogeographical reasons, as N. cymodocea seems to be restricted to temperate waters.

Nemertesia macquariensis sp. nov. shares with Nemertesia ciliata Bale, 1914 , the presence of branched and polysiphonic stems and the heteromerous division of the hydrocladia into internodes. However, in Bale’s species the hydrocladia start with an ahydrothecate internode. They also differ because in N. ciliata the cauline apophyses are typically arranged in verticils of three or four, although decussate or even alternate pairs are also present in younger parts ( Ramil and Vervoort 2006). Finally, the hydrotheca is well below the middle of the internode. The geographically closer records of N. ciliata are from Tasmania, New Zealand and waters around South Africa.

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

Figures

Fig. 4. Holotypes: A, Acryptolaria seamountensis sp. nov. (NIWA 40133); B, Nemertesia macquariensis sp. nov. (NIWA 40094). Scale bar = 10 mm.

Fig. 11. Nemertesia macquariensis sp. nov.: A, stem fragment showing hydrocladial arrangement; B, stem fragment with cauline apophysis showing mamelon (arrow) and one axillary nematotheca; C, detail of cauline apophysis showing mamelon (arrow); D−G, hydrocladial internodes showing hydrothecae and nematothecae; H, detail of hydrotheca and nematotheca with scooped rim (arrow). Scale bars: A = 200 μm; B, D−G = 100 μm; C, H = 50 μm.

Fig. 12. Nemertesia macquariensis sp. nov. A−B, cauline apophyses showing mamelon and nematothecae (A with two mamelons); C−D, fragments of hydrocladia showing division into hydrothecate and ahydrothecate internodes, hydrothecae and nematothecae. Scale bars: A−B, D = 250 μm; C = 500 μm.