Cladocarpus formosus

Cladocarpus speciosus Verrill, 1879: 311. — Nutting 1900: 116, pl. 28, fig. 8 – 11. — Whiteaves 1901: 28. — Kindle & Whittaker 1917: 233. — Fraser 1918: 361. — Fraser 1921: 179, fig. 106. — Fraser 1944: 41, pl. 90, fig. 399 a – d. — Fraser 1946: 413. — Vervoort 1966: 149. — Calder 1997 b: 89. Cladocarpus crenulatus Levinsen, 1893: 210, pl. 8, fig. 13 – 14. — Vanhöffen 1897: 246. — Jäderholm 1909: 110. — Ritchie 1909: 314. Cladocarpus dubius Broch, 1910: 207. — Kramp 1943: 44.

Description. Colonies light brown to whitish in alcohol, plumose, occasionally ramified, up to 53.5 cm high, arising from root-like hydrorhizae consisting of tufts of tubules supporting the stems. Hydrorhiza sometimes also discoid (hard substrate). Stem erect, polysiphonic basally (3.0 mm wide), thinning out to monosiphonic distally. Branches long, arising at acute angles from stem, either irregularly or in subopposite pairs; sometimes second order branching present. Main axial tube in front of stem and branches, divided into 850 – 1100 µm long internodes by more or less straight nodes. Accessory tubes parallel, not jointed, without hydrothecae, but with numerous nematothecae. Internodes with one apophysis close to distal end, directed alternately left and right, and with 3 – 4 nematothecae; 1 – 2 centrally placed and two axillar. Hydrocladia up to 2.7 cm long, closely set, given off frontally at acute angles from apophyses of main tube. They are formed by up to 33 thecate internodes separated by transverse nodes, each with 8 – 10 internal septa (generally 8). Internodes with one hydrotheca and three one-chambered nematothecae. Hydrothecae deep, not bulging into lumen of hydrocladium or only very slightly, almost totally adnate to internode, leaving only 1 / 10 th free distally. Walls almost parallel, long hydrothecal axis forming an acute angle with the corresponding internode; depth / width at rim = 1.15 – 1.74 (n = 25). Intrathecal ridge of varied shape, length and development, thin and straight or sometimes almost circular, running from abcauline wall of hydrotheca towards internode, hardly reaching the latter. Margin wavy, with normally two outer cusps on abcauline side. Nematothecae: one mesial proximal and two laterals. Mesial adnate to hydrotheca except on first internode, where there is a distinct gap between distal end of nematotheca and hydrothecal base, tapering distally, with slightly crenulated margin, extending for 1 / 2 – 4 / 5 th the length of abaxial wall of hydrotheca; an oblique distal septum frequently present (Figure 4 C, D). Lateral nematothecae mostly adnate to both internode and hydrotheca, tapering distally, tip slightly rising above hydrothecal margin; aperture adaxial, with finely crenulated margin. Phylactocarps one per hydrocladium, 3.8 mm long, arising slightly laterally to first thecate internodes, between hydrothecal base and mesial nematotheca; antler-shaped, ramified, arching over the gonothecae, composed of a small internode followed by a dichotomously branched jointed structure. Branching normally of first order (though some additional branching may occur) and up to six branches. Nematothecae abundant, in a single adaxial row (occasionally abaxially), ending in a pair distally, all with margin finely crenulated. Gonothecae 1 – 2 on apophyses of main tube and up to 6 at forking of phylactocarps, obovate, distally truncated, curved, hooded, with lateral, narrowly oval aperture. Sex indeterminable.

Remarks. This species is morphologically varied, and our material comprises colonies with differences in structure of the thecate internodes that we attribute to intraspecific variability. There are two extreme morphs, although intermediate material is present as well. One of these extremes corresponds with material such as that described by Schuchert (2001). The other (Figure 4 A) exhibits the following differences: i) the basal regions of hydrothecae bulge slightly into the lumen of the hydrocladium; ii) the terminal aperture of paired lateral nematothecae is slightly below the level of the hydrothecal margin; iii) the end of the mesial nematotheca extends for 3 / 5 – 4 / 5 th the length of the abaxial hydrothecal wall; iv) the abaxial end of the hydrothecal ridge is curved backwards, so that it reaches back to the septum (hairpin shaped). One of the main differences between the two morphotypes is the shape of the intrathecal septum, which can be thin and straight (FC 07 L 167) or with its end arching backwards so that it sometimes reaches the septum again (NEREIDA 0610 RD 74, PLA 07 L 101, Figure 4 C). This character is highly variable. Levinsen (1893: pl. 8, fig. 13) depicted hydrothecae with a slightly curved adcauline end of the hydrothecal septum, and Naumov (1969: 526) discussed differences in structure of the intrathecal septum between Cladocarpus speciosus (now a synonym of C. formosus) and C. formosus, indicating that this character should not be considered of taxonomic importance in distinguishing between the two species. In the illustration of C. speciosus by Nutting (1900), the septum originates at the internode (see his pl. 28), while in the material studied here it begins at the abcauline wall of the hydrotheca and seldom reaches across to the internode. The mesial nematothecae are adnate to the hydrothecae and their ends extend for 1 / 2 – 1 / 3 to 3 / 5 – 4 / 5 the length of the abaxial wall of the hydrotheca (Figure 4 A, B). However, in the first cormidium, the mesial nematotheca is free from the hydrotheca (Figure 4 F). This is related to the location of the phylactocarps, which occur on this internode and arise in the gap between mesial nematotheca and hydrotheca. Internodes vary considerably in length, and so do the hydrothecae, as well as the proportion of the internodes occupied by the hydrothecae. In some colonies (FC 07 L 167), the hydrothecae extend along 75 – 86 % of the internode, whereas in others having smaller hydrothecae, only 60 – 68 % of the internode length is occupied (NEREIDA 0610 RD 74, see Table 5). The ratio hydrothecal length / width is also quite varied (between 1.15 – 1.74), with some hydrothecae almost as long as wide, while others are more than 1.5 times longer than wide. Gonothecae occur on both the phylactocarp and apophyses (with 1 – 2 per apophysis) of the main tube (Figure 4 F). Colonies with gonothecae, but lacking phylactocarps, were observed in material from several stations, including NEREIDA 0610 RD 74. Such specimens were usually small in size. Cornelius (1995) noted that colonies of this species typically reach up to 8.0 cm, with specimens of as much as 15.0 cm reported by Naumov (1969). A specimen from station NEREIDA 0810 RD 104 was 53.5 cm high, a colony that must be considered exceptionally large. The development of the hydrothecal cusps varies, sometimes they being so little developed that the margin appears sinuous. Branching of the hydrocaulus is frequent at the distal end of the colony, and twin main stems arising from the same hydrorhiza sometimes occur. The shape of the phylactocarp and the position of gonothecae are identical in both types of colonies. Fewkes (1881) provided a rudimentary account of an aglaopheniid he called Aglaophenia crenata from a fragmentary and unbranched colony dredged at 41 º 25 ’ N – 65 º 35 ’ W (2270 m depth) off Massachusetts. Nutting (1900) redescribed and assigned it to Cladocarpus, despite the absence of a gonosome on the type, and he considered it very close to C. speciosus. His description agrees with the material of C. formosus studied here, colonies of which vary considerably in hydrothecal shape, intrathecal septum development, and position of the mesial nematotheca, and the two may be conspecific. That possibility is supported by the depth at which C. crenatus was collected, falling within the known depth range of C. formosus. Observed depth range: 240 – 1885 m, within the range already known for the species. A neritic-bathyal species according to Calder (1997 b), and also abyssal (Cladocarpus speciosus, 2602 m, continental slope east of Virginia, Fraser 1944; Calder 1997 b).

Distribution. Kramp (1938) considered C. formosus to be a southern species in Iceland, perhaps following Broch (1910), who regarded it as a southern Atlantic hydroid recorded sporadically in the Arctic. According to Cornelius (1995), its distribution is circumpolar in sub-arctic to arctic waters. Cladocarpus formosus is known from the Barents Sea, Sea of Okhotsk and the Kuriles (Naumov 1969, 80 – 1400 m; Antsulevich 1992, 42 – 60 m in an upwelling zone, and 130 + m out of this area), Faroe Channel (Ritchie 1909, 1030 m), Iceland (Broch 1918, ca. 83 – 847 m; Kramp 1938, 83 m; Schuchert 2001, 83 – 1020 m), Denmark Strait (Broch 1918, ca. 1444 m; Kramp 1938, 384 – 1444 m), Bredfjord in south Greenland (Kramp 1932 b, 260 – 320 m), west coast of Greenland (Broch 1918, ca. 103 – 1096 m; Schuchert 2001, 187 – 200 m), Davis Strait (Levinsen 1893, ca. 150 m; Broch 1918, ca. 1041 m), 63 º 36 ’ N – 55 º 15 ’ W, 60 º 16 ’ N – 47 º 48 ’ W, 60 º 22 ’ N – 47 º 27 ’ W (Kramp 1932 a, 120 – 1200 m), 72 ° 32 ’ N – 58 ° 05 ’ W, 69 ° 16 ’ N – 58 ° 08 ’ W (Jäderholm 1919, ca. 212 – 335 m), eastern Canada (Kindle & Whittaker 1917, ca. 366 m, based on literature records), Flemish Cap, Flemish Pass and Grand Banks (present study), and Banquereau, off Sable Island (Verrill 1879, ca. 365 m; Nutting 1900; Whiteaves 1901; Fraser 1918, 1944). Not recorded further south in southeastern USA by Henry et al. (2008), but collected from Rainbow Vent Field, Mid-Atlantic Ridge (36 ° 13 ’ N, ca. 2400 m) (Desbruyères et al. 2001).

Fertile material. Collected in August 2006 (240 – 1185 m depth), June and July 2007 (406 – 1381 m depth), August 2008 (1016 – 1198 m depth), from May to August 2009 (768 – 1885 m depth), and from June to August 2010 (520 – 1589 m depth).

Material examined. FN 3 L 06 L 44, one fertile colony 9.0 cm high; FN 3 L 06 L 51, one fertile colony 7.0 cm high; FN 3 L 06 L 85, one fertile colony 9.5 cm high; PLA 07 L 70, 2 fertile colonies, largest one 8.0 cm high; PLA 07 L 86, one fertile colony 31.5 cm high; PLA 07 L 87, 2 colonies, largest one 22.0 cm high, one fertile; PLA 07 L 93, one fertile colony 19.1 cm high; PLA 07 L 101, one colony 19.5 cm high; FC 07 L 21, 2 colonies, largest one 12.1 cm high, one fertile; FC 07 L 23, one sterile colony 6.2 cm high; FC 07 L 155, one fertile colony 14.5 cm high; FC 07 L 166, 4 colonies, largest one 9.2 cm high, one fertile; FC 07 L 167, 2 fertile colonies, largest one 13.0 cm high; FC 07 L 171, one fertile colony 5.5 cm high; FN 3 L 08 L 66, one fertile colony 22.5 cm high; FN 3 L 08 L 88, 3 colonies, largest one 19.0 cm high, 2 fertile; FN 3 L 09 L 88, 3 colonies, largest one 44.0 cm high, one fertile; FN 3 L 10 L 35, one sterile colony 9.5 cm high; NEREIDA 0509 RD 4, 5 fertile colonies, largest one 8.3 cm high; NEREIDA 0509 RD 6, 5 colonies, largest one 10.1 cm high, 4 fertile; NEREIDA 0509 RD 10, 15 colonies, up to 11.0 cm high, some fertile; NEREIDA 0509 RD 12, 8 colonies, up to 11.5 cm high, some fertile; NEREIDA 0509 RD 15, 14 colonies, up to 11.7 cm high, some fertile; NEREIDA 0509 RD 18, 14 colonies, up to 10.8 cm high, some fertile; NEREIDA 0509 RD 19, 18 colonies, up to 12.8 cm high, some fertile; NEREIDA 0509 RD 20, 22 colonies, up to 12.7 cm high, some fertile; NEREIDA 0509 RD 21, 2 fertile colonies, largest one 8.5 cm high; NEREIDA 0509 RD 22, 20 colonies, up to 9.0 cm high, some fertile; NEREIDA 0509 RD 23, 21 colonies, up to 9.5 cm high, some fertile; NEREIDA 0509 RD 24, 34 colonies, up to 11.5 cm high, some fertile; NEREIDA 0609 RD 27, 5 colonies, largest one 11.0 cm high, some fertile; NEREIDA 0609 RD 28, 2 colonies, largest one 7.3 cm high, one fertile; NEREIDA 0609 RD 41, 6 colonies, up to 7.6 cm, some fertile; NEREIDA 0709 RD 49, 3 fertile colonies, largest one 8.8 cm high; NEREIDA 0709 RD 51, one fertile colony 14.3 cm high; NEREIDA 0709 RD 57, 2 fertile colonies, largest one 17.5 cm high; NEREIDA 0709 RD 59, 6 fertile colonies, largest one 14.2 cm high; NEREIDA 0610 RD 62, 20 colonies, up to 5.7 cm high, some fertile; NEREIDA 0610 RD 63, 12 colonies, up to 8.0 cm high, some fertile; NEREIDA 0610 RD 64, 9 colonies, up to 5.3 cm high, some fertile; NEREIDA 0610 RD 65, 51 colonies, up to 9.8 cm high, some fertile; NEREIDA 0610 RD 66, 50 colonies, up to 11.0 cm high, some fertile; NEREIDA 0610 RD 67, 5 fertile colonies, largest one 7.0 cm high; NEREIDA 0610 RD 71, 6 colonies, up to 6.0 cm high, some fertile; NEREIDA 0610 RD 74, 42 colonies, up to 17.0 cm high, some fertile; NEREIDA 0710 RD 76, 36 colonies, up to 13.5 cm high, some fertile; NEREIDA 0710 RD 77, 8 colonies, up to 12.5 cm high, some fertile; NEREIDA 0710 RD 78, one sterile fragment 2.7 cm high; NEREIDA 0710 RD 79, 2 fertile colonies, largest one 11.0 cm high; NEREIDA 0710 RD 80, 18 colonies, up to 14.2 cm high, some fertile; NEREIDA 0710 RD 83, 2 fertile colonies, largest one 6.0 cm high; NEREIDA 0710 RD 85, 9 colonies, up to 10.0 cm high, some fertile; NEREIDA 0710 RD 86, 9 colonies, up to 18.2 cm high, some fertile; NEREIDA 0710 RD 87, 26 colonies, up to 17.3 cm high; NEREIDA 0710 RD 88, 41 colonies, up to 17.5 cm high, some fertile; NEREIDA 0710 RD 92, 39 colonies, up to 20.5 cm high; NEREIDA 0710 RD 95, 13 colonies, up to 42.0 cm high, some fertile; NEREIDA 0810 RD 97, 16 colonies, up to 16.5 cm high, some fertile; NEREIDA 0810 RD 98, 7 colonies, up to 15.6 cm high, some fertile; NEREIDA 0810 RD 99, 14 colonies, up to 10.5 cm high, some fertile; NEREIDA 0810 RD 100, 30 colonies, up to 23.2 cm high, some fertile; NEREIDA 0810 RD 101, 10 colonies, up to 11.4 cm high, some fertile; NEREIDA 0810 RD 102, 2 colonies, largest one 8.8 cm high, one fertile; NEREIDA 0810 RD 103, 13 colonies, up to 27.5 cm high, some fertile; NEREIDA 0810 RD 104, 16 colonies, up to 53.5 cm high, some fertile.