Callicarpa gracilis Fewkes, 1881

Galea, Horia R., Di Camillo, Cristina G. & Maggioni, Davide, 2021, An integrative study of Callicarpa gracilis Fewkes, 1881 and Aglaophenia trifida L. Agassiz, 1862, with notes on some hydroids (Cnidaria: Hydrozoa) from French Guiana, Zootaxa 4926 (3), pp. 301-341 : 304-314

Callicarpa gracilis Fewkes, 1881

Figs 1–8 , 15 ; Tables 1, 2

Callicarpa gracilis Fewkes, 1881: 134 , pl. 2 figs 1, 2, 6, 7.— Allman, 1883: 3 (footnote), 13.—A. Agassiz, 1888: 137, figs 438–439.— Versluys, 1899: 47.— Nutting, 1900: 85, pl. 17 figs 4–6.— Bedot, 1916: 58.— Bedot, 1918: 78.— Bedot, 1921: 16.— Fraser, 1944: 328, pl. 69 fig. 316.— Bouillon et al., 2006: 364, fig. 172A–B.—Stephens & Calder, 2010: 271.

Type material. National Museum of Natural History , Washington, USA, catalogue number: USNM 72363 (schizoholotype); collected in 1880 from an unknown locality “off the eastern coast of the United States” ( Fewkes 1881: 127, 129) .

Material examined. Unbranched morphotype: MNHN-IK-2015-629; Proteus stn DW5067; 6°12.4’ N, 52°04.5’ W; 103– 101 m; 01 Dec 2017; one colony 5 cm high bearing a phylactocarp.—MNHN-IK-2015-631; Proteus stn DW5076; 6°10.3’ N, 51°59.6’ W; 112– 112 m; 02 Dec 2017; one colony, 6 cm high, bearing 2 phylactocarps.— MNHN-IK-2015-625; Proteus stn DW5078; 6°10.2’ N, 52°00.1’ W; 105– 99 m; 02 Dec 2017; 6 colonies, 5–7.5 cm high, all but one bearing phylactocarps; GenBank accession numbers: MT 949946 (16S), MT 949952 (18S), MT 949940 (28S), MT 949458 ( COI).—MNHN-IK-2015-652; Proteus stn DW5079; 6°10.1’ N, 52°00.3’ W; 104– 101 m; 02 Dec 2017; 4 colonies, 3–6 cm high, of which 2 are sterile, while 2 others bear phylactocarps.—MNHN-IK-2015-628; Proteus stn DW5080; 6°09.9’ N, 52°00.1’ W; 101– 100 m; 02 Dec 2017; 2 colonies, one 5.5 cm high and sterile, the other 6.5 cm high and bearing a phylactocarp.—MNHN-IK-2015-653; Proteus stn DW5086; 6°11.1’ N, 52°02.4’ W; 107– 104 m; 02 Dec 2017; 3 colonies, 5.5–7.5 cm high, all bearing phylactocarps.—MNHN-IK- 2015-617; Proteus stn DW5087; 6°11.2’ N, 52°02.6’ W; 105– 103 m; 02 Dec 2017; 7 colonies, 4–8 cm high, with variably developed phylactocarps; GenBank accession numbers: MT 949945 (16S), MT 949951 (18S), MT 949939 (28S), MT 949457 ( COI).—MNHN-IK-2015-630; Proteus stn DW5089; 6°09.5’ N, 52°01.4’ W; 94– 92 m; 03 Dec 2017; 2 colonies, each bearing a phylactocarp.—MNHN-IK-2015-635; Proteus stn DW5091; 6°07.4’ N, 51°59.5’ W; 89– 31 m; 03 Dec 2017; a 4.5 cm high colony bearing a young phylactocarp.— MNHN-IK-2015-634; Proteus stn DW5093; 6°05.4’ N, 52°01.5’ W; 75–76 m; 03 Dec 2017; a 6.5 cm high colony bearing a young phylactocarp.

Branched morphotype: MNHN-IK-2015-632; Proteus stn DW5069; 6°13.6’ N, 52°05.3’ W; 115– 115 m; 01 Dec 2017; a ca. 22 cm high colony with phylactocarps; GenBank accession numbers: MT 949950 (16S) , MT 949956 (18S) , MT 949944 (28S) , MT 949459 ( COI) .

Description. The species displays two distinct morphotypes: one forming simple plumes ( Fig. 2 ) and one building comparatively taller colonies whose stems are provided with irregularly-arranged cladia-bearing branches ( Fig. 6 ). Due to their different appearance and structure, they are described separately below.

Unbranched colonies solitary, erect, up to 8 cm high, relatively rigid (quite able to support themselves when out of liquid), feather-like, arising from a tangled mass of thin, highly-ramified, stolonal tubes embedded in sand. Stems simple, moderately-fascicled, not exceeding 0.75 mm in width basally, composed of a centrally-placed, cladia-bearing, main tube, surrounded by a varied number of auxiliary tubes. Main tube relatively thick and unsegmented, with rather thick, smooth perisarc; equivalents of internodes moderately-long, bearing a latero-distal apophysis supporting a cladium; apophysis not always distinctly delimited from the corresponding cladium but, when present, node oblique; apophysis well-developed, with a distally-placed, conical mamelon (with circular aperture on summit) on adaxial surface, and a pair of axillar nematothecae, one on each lateral side. Auxiliary tubes equally undivided, with two parallel, longitudinal rows of nematothecae, arranged either in pairs or irregularly alternate. Cladia unbranched, alternate, closely-set, in two parallel, coplanar rows; up to 12 mm long, regularly divided by distinct, slightly oblique nodes into up to 30 cormidia; each internode relatively long, with a hydrotheca almost centrally-placed, although closest to the proximal node and not occupying the whole length of the cormidium, and its complement of 3 nematothecae, one mesial and a pair of laterals; proximal-most cormidium occasionally with twin mesial nematothecae. Hydrotheca inverted-conical, rather deep, abaxial wall straight to imperceptibly convex, with thickened perisarc, latero-adaxial wall equally thickened and consequently opaque, slightly concave; a perisarc plug at junction between the base and the adaxial wall; hydropore rounded, set close to the abaxial wall; hydrothecal aperture semicircular (in apical view), set at a right angle to the internode. Mesial nematotheca seated well below the hydrothecal base on an adaxial prominence of the internode wall; lateral nematothecae borne on indistinct apophyses, slightly below the hydrothecal rim. Each cladial internode with a number of incomplete internal ridges of perisarc originating adaxially: two flanking above and below the mesial nematotheca, one radiating from the perisarc plug prolonging abaxially the hydrothecal base, one occasionally present in middle of the adaxial hydrothecal wall, two flanking above and below the lateral nematothecae, as well as one (occasionally two) close to the distal node. Phylactocarps up to 3 to each cormoid, given off on one side (that becomes frontal) of the colony from a thick, internal, auxiliary tube that surfaces from inside the fascicled stem at an angle of about 35–40°; up to 19 mm long, borne on a short, smooth pedicel prolonged distally into the longitudinal axis proper; the latter unsegmented, bearing up to 44 stacked verticils, each of which is composed of 3 ramuli (with the exception of the first, occasionally second, whorl) forming an angle of 120° between them; ramuli from every other verticil arranged in the same position, while those belonging to consecutive verticils alternate in position; ramuli hollow tubes, antler-shaped, divided dichotomously twice, occasionally showing an incipient third division, distally opening into small, circular apertures; pedicel of phylactocarp with 2–4 pairs of nematothecae on adaxial side, remainder of axis athecate; adaxial side of undivided, proximal part of ramulus with a pair of proximal nematothecae, followed by a broadly triangular, raised area of thinner perisarc on which are borne ca. 3–4 gonothecae (at different developmental stages), and ending more distally into two successive pairs of nematothecae; first order branches of ramulus with 1–2 pairs of nematothecae displaced laterally; second order branches of ramulus with a number of irregularly-placed nematothecae, with a tendency to alternate. Proximal-most whorl of ramuli generally composed of only two latero-abaxial ramuli; occasionally, there may be an unpaired, abaxial ramulus, followed by a pair, and then by regular, alternating rows of three. Gonothecae broadly ovoid, somehow laterally flattened, thin-walled, aperture distal, transversely-set, ovoid in outline, closed by flimsy, deciduous operculum; the type of gonophore could not be ascertained in this fixed material. All nematothecae of a colony trumpet-shaped, movable, bithalamic, with tall lower chamber and shallow upper chamber, the adaxial wall of the latter with distinct emargination. Hydranths contracted inside their corresponding hydrothecae; tentacle number could not be ascertained.

Branched colony erect, ca. 22 cm high, rather flaccid, unable to fully support itself when out of liquid, arising from a large mass of enmeshing, thin, ramified fibers embedded in sand. Stem 1 mm wide basally, fascicled, grading to monosiphonic distally; lower half without branches and/or cladia, upper half cladiate, giving rise to 5 irregularly-arranged branches springing in all directions; branches up to 3.5 cm long, given off out- and slightly upward, then arching gracefully nearly horizontally; proximally lightly fascicled, grading to monosiphonic distally. Main tube of stem and branches undivided; equivalents of stem internodes with a latero-distal apophysis supporting a cladium, and 1–2 nematothecae in central part of the opposite side, towards the middle of the internode; apophyses well-developed, with a conspicuous, conical mamelon (with small, rounded aperture on summit) on adaxial side, a pair of axillar nematothecae (one on each side of apophysis), as well as with twin, distally-placed, adaxial nematothecae, just below the slightly oblique node that separates the apophysis from the corresponding hydrocladium; internodes of cladia-bearing branches comparatively shorter than their cauline counterparts, without proximal nematothecae, but with similar cladial apophyses, the latter however not delimited distally, but confluent with the corresponding cladia. The latter alternate, the two rows coplanar on both stem and branches; up to 5 mm long on stem and 7 mm long on branches; divided homomerously into up to 16 regular internodes through distinct, slightly oblique nodes; internodes moderately long, with a hydrotheca placed centrally, and its complement of 3 nematothecae, one mesial and a couple of laterals; there are 5 internal septa to each internode, of which 2 pairs flank below and above the nematothecae, while the last one is placed towards the distal node. Hydrotheca deep, conical, abaxial wall almost straight for nearly its whole length, basally convex; adaxial wall distinctly thickened, displaying a wide flange of gradually thinner perisarc on each side of the theca; aperture distinctly sloping adaxially, rim even. Mesial nematotheca well below the hydrothecal base, seated on a distinct, proximal, adaxial prominence of the internode; lateral nematothecae borne on small, though distinct apophyses given off at the junction of the lateral hydrothecal wall with the internode behind; lateral nematothecae greatly surpassing the hydrothecal rim. Hydranths contracted inside their hydrothecae, type of tentacles and their number could not be ascertained. { Fig. 7 about here} Gonosome forming phylactocarps on the distal parts of the branches; phylactocarps arising from either the accessory tubes or the cladia-bearing tube, but given off amongst the hydrocladia in a plane perpendicular to theirs, and projecting upward; proximal most phylactocarps all aligned along a median row but, more distally, alternately shifted on to each side, occasionally forming divergent pairs; phylactocarps short, tubular, arching upward from the axis of cladia-bearing branch, but not being demarcated basally from it by a node; composed of a proximal (axillar) pair of nematothecae (one to each side), followed immediately by 2 consecutive pairs of foramina (for the insertion of gonothecae), another pair of nematothecae towards the central part, and a distal hydrotheca, together with its complement of 3 nematothecae. Gonothecae urn-shaped, thin-walled, except below the aperture, tapering below into an indistinct, laterally-set pedicel; aperture circular, operculum not seen; type of gonophore and sex could not be ascertained. All the nematothecae of the colony alike; conical, moderatelylong, bithalamic, lower chamber deep, upper chamber relatively shallow, with rim emarginated of adaxial side.

Remarks. Nutting (1900) supplemented the original account on C. gracilis with a redescription of the type material, a text that was reproduced later on by Fraser (1944). Although many details of its microscopical anatomy remained overlooked, Nutting confirmed the polysiphonic structure of the stem.

As noted in the descriptive section, two morphotypes occur in the present collection, one being a typical Callicarpa, sensu Fewkes (1881) , while the other has an Antomma -like appearance; they can be easily mistaken for two distinct species, although the results of the molecular study (see below) demonstrate that both are conspecific.

In the unbranched colonies, the phylactocarps “resemble spikes of barley” ( Fewkes 1881: 135) and, unlike in the type material in which there were “no hydrothecae on the ribs or at the base of the verticils”, the proximal most ramuli do not always comprise exclusively the usual branched, hollow, nematothecate tubes. Indeed, a ramulus can be replaced by a short, either simple (MNHN-IK-2015-629) or bifid (MNHN-IK-2015-652), cladium. In this case, the proximal part of the ramulus comprises a short axis, provided basally with 2 laterally-placed, axillar nematothecae (at origin from the longitudinal axis of the phylactocarp), immediately followed by the site of the insertion of gonothecae and –after a short distance– by another pair of nematothecae, all ending in a hydrotheca with its complement of 3 nematothecae. From here, the ramulus is either prolonged by a sequence of hydrothecate internodes (MNHN-IK-2015-629), or by a short, bifid, distal projection above the hydrotheca (each branch is provided with a single, basal nematotheca) carrying a succession of hydrothecate internodes, with or without intervening ahydrothecate internodes bearing single nematothecae (MNHN-IK-2015-652). In some other instances, above the proximal-most hydrotheca, there is a bifid projection (whose short branches do not bear nematothecae) provided with a pair of hollow spikes with nematothecae (MNHN-IK-2015-628). In order to preserve the integrity of these rare specimens, the structures mentioned above were not illustrated.

Type material of C. gracilis was represented by a ca. 15 cm high colony, whose proximal part of the stem bore the stump of a potential broken branch (although this could have been well the pedicel of a broken phylactocarp). A comparatively taller, branched colony is present in material MNHN-IK-2015-632. Its trophosome resembles that of Antomma longicarpa ( Nutting, 1900) , as illustrated by Fewkes (1881, as Hippurella annulata Allman, 1877 ), in being represented by a stem with pinnately-arranged cladia that gives rise irregularly to a number of cladia-bearing branches, both the stem and its branches being fascicled.

Although their respective cladia are almost indistinguishable morphologically, there are several differences occurring in the branched morphotype compared to its unbranched counterpart: 1) the cladial apophyses of the stem possess distally twin nematothecae ( Fig. 7A, B ), but their presence is, however, inconstant, although it is not clear whether this is a normal situation or the consequence of a possible mechanical breakage; such nematothecae were never observed in any of the unbranched colonies at hand; 2) the gonosome of the branched morphotype is not represented anymore by a morphologically-complex structure, but by the equivalent of a radial section of it, comprising only single or twin ramuli, that have spread over the distalmost part of the axis of a cladia-bearing branch; 3) this said, it is however not clear whether the specimen at hand displays a fully-developed gonosome or, in other words, if the structures illustrated in Figs 7K, L and 8B, C represent incipient phylactocarps or the components of an entire phylactocarp fused to the axis of a cladia-bearing branch; additional fertile specimens are expected to answer the question; 4) each phylactocarp/ramulus represents the equivalent of the proximal-most portion of a ramulus that include hydrothecate internodes, as described in the unbranched colonies.

Besides C. gracilis , the genus Callicarpa comprises a second species, C. chazaliei Versluys, 1899 , that is distinguished from the former through the following characters: 1) its cladia are comparatively more distant from one another; 2) its hydrocladial internodes possess a distal, unpaired nematotheca above the hydrotheca; 3) the ramuli of its phylactocarps are reportedly branched once instead of twice.

Distribution. Callicarpa gracilis , although dealt with in comprehensive works such as Nutting (1900) and Fraser (1944), was only known through the (unlabeled) type material collected by the Blake in 1880 who, according to Fewkes (1881: 127), sailed “off the eastern coast of the United States, in the summer of 1880”. Nutting (1900: 85), however, expressed the opinion that it “belongs doubtless to the West Indian fauna”, but this appears to be inexact in light of the data provided by the descriptor. The specimens dealt with in the present study represent the first record for French Guiana.

Figures

FIGURE 1. Historical illustrations of Callicarpa gracilis Fewkes, 1881, modified after the original account. A. Whole colony. B. Hydrotheca. C. Whole phylactocarp seen laterally. D. Cross section through the phylactocarp.

FIGURE 2. Four preserved, fertile colonies of Callicarpa gracilis Fewkes, 1881 (unbranched morphotype). Scale bar: 1 cm.

FIGURE 3. Callicarpa gracilis Fewkes, 1881 (unbranched morphotype). A. Portion of monosiphonic part of stem with proximal parts of three consecutive cladia. B. Detail of a cladial apophysis, showing mamelon and one of the axillar nematothecae. C. Two cladial internodes. D. Proximal part of a cladial internode, showing mesial nematotheca. E. Distal part of a cladial internode, showing lateral nematotheca, thickening of the adaxial hydrothecal wall, and the intranodal ridges. F. Ramulus of phylactocarp with a gonotheca. Scale bars: B, D, E = 100 µm; C = 200 µm; A = 400 µm; F = 500 µm.

FIGURE 4. SEM study of Callicarpa gracilis Fewkes, 1881, unbranched morphotype (part). A. Portion of stem, showing its fascicled condition. B. Portions of cladia. C. Two cladial internodes. D. Whole phylactocarp. E, F. Proximal part of a phylactocarp at different magnifications. All from sample MNHN-IK-2015-617. Scale bars: C = 100 µm; B = 200 µm; A, F = 500 µm; E = 1 mm; D = 2 mm.

FIGURE 5. SEM study of Callicarpa gracilis Fewkes, 1881, unbranched morphotype (continued). A. Detail of an empty phylactocarp. B. Portion of a phylactocarp bearing gonothecae. C. Gonothecae, greatly enlarged. D. Three insertions of gonothecae on the proximal, adaxial side of a ramulus. E. Detail of adjacent ramuli. F. Distal end of a phylactocarp seen apically. All from sample MNHN-IK-2015-617. Scale bars: D = 50 µm; E = 100 µm; B, C = 200 µm; A, F = 500 µm.

FIGURE 6. Preserved colony of Callicarpa gracilis Fewkes, 1881 (branched morphotype). Scale bar: 2 cm.

FIGURE 7. Callicarpa gracilis Fewkes, 1881, branched morphotype. A. Portion of stem with insertions of two consecutive cladia. B. Detail of a cladial apophysis of stem. C. Proximal part of a cladium from a side branch. D. Detail of a cladial apophysis of branch. E–F. Hydrothecae from cladia of stem (E) and branch (F). G–J. Mesial and lateral nematothecae of hydrothecae from stem (G and H, respectively) and branch (I and J, respectively). K, L. Phylactocarp seen laterally (K) and apically (L). M. Gonotheca. Scale bars: B, D, G–J, M = 100 µm; A, C, E, F, K, L = 200 µm.

FIGURE 8. Callicarpa gracilis Fewkes, 1881, branched morphotype. A. Hydrotheca, image obtained by stacking. B. Distal part of a branch, showing one row of cladia (the opposite one was removed) and three consecutive phylactocarps (ph = phylacrocarp; hc = hydrocladium; a.t. = auxiliary tube of the branch). C. detail of a phylactocarp, image obtained by stacking. Scale bars: A = 100 µm; C = 200 µm; B = 300 µm.

FIGURE 15. Phylogenetic trees showing the relationship among Plumulariidae species according to 16S rRNA (A) and multilocus (B) analyses.Numbers at nodes represent the Bayesian posterior probabilities (BPP) and the maximum likelihood bootstrap values (BS), and are shown only when both BPP ± 0.9 and BS ± 75. Newly-produced sequences are highlighted in yellow.

Tables

TABLE 2. Measurements of the branched morphotype of Callicarpa gracilis Fewkes, 1881, in µm.

Stem
- “internode” length	835–1400
- diameter of the main tube	190–200
- cladial apophysis, length	160–235
Branches
- “internode” length	470–555
- diameter of the main tube	215–230
- cladial apophysis, length	145–170
Apophyses-associated nematothecae
- mamelon, diameter at aperture	15–25
- axillar nematothecae, length	105–115
- axillar nematothecae, diameter at rim	55–60
- nematothecae distal on apophysis, length	95–100
- nematothecae distal on apophysis, diameter at aperture	50–55
Cauline cladia
- distance between 2 successive cladia on the same side of the stem	1780–2195
- internode length	485–535
- diameter at node	60–75
Cladia borne on branches
- distance between 2 successive cladia on the same side of the stem	840–920
- internode length	420–475
- diameter at node	60–110
Hydrothecae
- abaxial wall, length	210–230
- adaxial wall, length	175–190
- base width	40–50
- diameter at rim	85–100
- mesial nematotheca, length	100–115
- mesial nematotheca, diameter at rim	50–55
- lateral nematothecae, length	100–105
- lateral nematothecae, diameter at rim	55–60
Gonosome
- phylactocarp length	865–1100
- distance between two successive phylactocarps	800–1110
- gonotheca, total length	ca. 480
- gonotheca, maximum width	ca. 235
- gonotheca, diameter at aperture	ca. 145