Clytia elsaeoswaldae Stechow, 1914, Stechow, 1914
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|Clytia elsaeoswaldae Stechow, 1914|
Material examined. Syntypes: colony with gonangia, on alga. (Charlotte Amalie, St. Thomas, U.S. Virgin Islands) [Zoologische Staatssamlung, München, microslides 20041517 (part of colony with six hydranths and one gonangium), 20041518 (part of colony with nine hydranths and six gonangia) and 20041519 (part of colony with 39 hydranths and ~ 25 gonangia)]. Collected by E. Stechow and E. Oswald, 18 March 1912.
Additional material. (1) Colony with gonangia on posts of a pier, growing on sponges and barnacles ( TEBAR, São Sebastião, SP, Brazil; coordinates: 23 ° 47.97 ’S; 45 ° 22.98 ’W; water depth: 5–20 m) [ MZUSP 962, 963]; collected by A. Lindner and A.E. Migotto, 22 October 1999. (2) Colony with gonangia on iron structure, growing on sponge, Hypnea sp. and Eudendrium carneum Clarke, 1882 (Hydrozoa: Eudendridae) (Saco do Sombrio, Ilhabela, SP, Brazil; coordinates: 23 ° 53.77 ’S; 45 ° 14.74 ’W; water depth: ~ 5 m) [ MZUSP 959, 960, 961]; collected by A. Lindner, 26 September 1999. (3) Colony with gonangia growing on Sargassum sp. and 39 one to 21 days-old medusae liberated from colony and reared in the laboratory (Saco Grande, São Sebastião, SP, Brazil; coordinates: 23 ° 49.72 ’S; 045° 25.52 ’W; water depth: 1–3 m) [colony: MZUSP 937, 938, 940, 941, USNM 1078726; medusae: MZUSP 939, 942, 943, 945, 946, 947, 948, 949, 950, 951, 952, 953, 954, 955, 956, 957, 958]; colony collected by A. Lindner, 19 February 1999. (4) Colony with gonangia on Sargassum sp., Hypnea sp. and bryozoan (Praia de Barequeçaba, west shore, São Sebastião, SP, Brazil; water depth: ~ 0.5 m) [ MZUSP 967, USNM 1078725]; collected by L.P. de Andrade, 0 5 April 2000. (5) Colony with gonangia on Sargassum sp. and ~ 100 newly liberated medusae (Praia de Barequeçaba, east shore, São Sebastião, SP, Brazil; water depth: ~1.0 m) [colony: MZUSP 965, USNM 1078727; medusae: MZUSP 966]; colony collected by L.P. de Andrade, 0 4 April 2000. (6) Colony with gonangia on Sargassum sp. and on dead hydrocaulus of Aglaophenia latecarinata (Hydrozoa: Aglaopheniidae ) (Praia do Guaecá, west shore, São Sebastião, SP, Brazil; water depth: ~ 1 m) [ MZUSP 964]; collected by L.P. de Andrade, 0 1 February 2000. (7) Colony on Sargassum sp. (São Sebastião, SP, Brazil) [ USNM 1078728]; collected by O.M.P. de Oliveira.
Diagnosis. Clytia elsaeoswaldae is distinguished from its congeners and other campanulariids by the combination of the following characters:
polyp: stems monosiphonic or, less common, polysiphonic, branching dichotomously. Hydrothecal cusps usually inclined to one side. Gonothecae only on hydrorhiza, with smooth, slightly undulated walls. B-type microbasic mastigophores 15–18 µm long in vivo and 13–16 µm long in formalin.
adult medusa: bell 3.6–5.5 mm in marginal diameter, up to 16 tentacles and at least 21 statocysts. A – type microbasic mastigophores, ~ 11 µm long, forming a row at the level of the circular canal (no character or combination of characters so far observed is diagnostic for young medusae).
Description. Hydroid. Colonies stolonal or with erect stems branching dichotomously up to 4 times ( Figure 2 View FIGURE 2 ). Erect stems up to 5.6 mm high. Hydrorhiza frequently growing on pedicels, sometimes forming incipient polysiphonic stems ( Figure 2 View FIGURE 2 F) or more developed polysiphonic stems up to 23 mm high and bearing up to 60 hydranths. Pedicels usually smooth, slightly curved, with 5–15 proximal and 2–16 distal annuli; median region of pedicels sometimes annulated. Distal end of pedicels bearing one hydrotheca. Internodes with a upward-curved apophysis supporting the next internode or the distal pedicel ( Figure 2 View FIGURE 2 A,B).
Hydrothecae cylindrical, 368–753 µm long and 255–408 µm wide at margin, with thin perisarc and walls almost parallel in lateral view, except a basal rounded portion ( Figure 2 View FIGURE 2 ). Hydrothecal diaphragm thin, transverse, near base of hydrotheca; basal chamber 16–78 µm long and 78–165 µm wide at diaphragm. Hydrothecal margin with 9–14 cusps (39–86 µm high); cusps usually inclined to right side when hydrotheca is seen in lateral view under microscope ( Figure 2 View FIGURE 2 ). Hydrotheca width:length ratio: 0.48–0.84 ( Table 2).
Gonothecae smooth, with undulated walls, 630–1019 µm long and 255–463 µm in maximum diameter, with a constriction (216–294 µm in diameter) under the truncated distal margin (205–345 µm in diameter). Gonothecae growing only from hydrorhiza ( Figure 2 View FIGURE 2 ); on Sargassum , small “aggregations” of gonothecae common ( Figure 2 View FIGURE 2 H). Gonothecal pedicels absent or having up to 4 annulli. Up to six medusae in each gonangium. Gonotheca width:length ratio: 0.38–0.50.
Hydranth column, on average, 5 times as long as broad when extended [493 ± 83 µm (252–600, N= 47) long and 103 ± 14 µm (72–144, N= 47)] wide; hypostome pedunculated, 120–264 µm wide, spherical in oral and lateral views ( Figure 2 View FIGURE 2 G); 20–34 filiform, amphicoronate tentacles, 420–1080 µm long; rings of A-type nematocysts every 15–20 µm along the tentacles. Coenosarc whitish.
A- and B-type microbasic mastigophores on hydranths and along cenosarc, only A-type on tentacles. A-type microbasic mastigophores 8.1 ± 0.6 µm [7.0– 9.5, N= 46] long and 2.0 ± 0.1 µm [2.0– 2.5, N= 46] wide in vivo and 7.1 ± 0.2 µm [6.5 –8.0, N= 40] long and 2.0 ± 0.2 µm [1.5–2.5, N= 40] wide in formalin. Discharged capsules 6.8 ± 0.4 µm [6.0– 7.5, N= 36] long and 2.0 ± 0.2 µm [1.5–2.5, N= 20] wide in vivo, with a proximal armature 6.8 ± 0.4 µm [6.0–8.0, N= 36] long. B-type microbasic mastigophores 16.4 ± 0.6 µm [15.0–18.0, N= 40] long and 3.8 ± 0.3 µm [3.0–4.0, N= 40] wide in vivo and 14.6 ± 0.5 µm [13.0–16.0, N= 180] long and 3.2 ± 0.3 µm [3.0–4.0, N= 150] wide in formalin. Discharged capsules 14.4 ± 0.5 µm [14.0–15.0, N= 17] long and 3.2 ± 0.4 µm [3.0– 4.5, N= 16] wide in vivo, with a proximal armature 18.1 ± 1.4 µm [15.0–20.0, N= 16] long.
Newly released medusa. Umbrella hemispherical, with ring canal, four perradial canals; four perradial bulbs with tentacles; two to four interradial developing bulbs; D-type nematocysts on the exumbrella; 4–8 adradial statocysts, each with one statolith. Some medusae also liberated with two interradial tentacles developing in opposite quadrants, i.e., with six tentacles (four perradial and the two incipient interradial tentacles). Gonads on median region of radial canals, 31–39 µm wide and 55–78 µm long in newly liberated medusae. Manubrium quadrate, ca. 0.4–0.5 height of bell; lips smooth with A-type nematocysts. Velum broad. Tentacles hollow, with A- and C-type nematocysts and a terminal nematocyst cluster with only C-type nematocysts.
Adult medusa. Umbrella saucer-shaped, 3.6–5.5 mm in diameter. Bell margin with up to 16 bulbs with tentacles and at least 21 statocysts ( Table 1; Figure 3 View FIGURE 3 ). Gonads oval when fully developed, on distal 1 / 3 of radial canals, approximately at the same level of velum margin in oral and aboral views ( Figure 3 View FIGURE 3 B). Manubrium short, cruciform, with four undulated lips in oral view; lips with A-type nematocysts. Marginal tentacles hollow, long, with Atype and atrichous isorhiza nematocysts. C-type, D-type, and terminal nematocyst cluster absent. A-type nematocysts, larger than those in the tentacles, forming a row at the level of the circular canal, perpendicular to the canal ( Figure 3 View FIGURE 3 C). Length of A-type nematocysts in a 21 day old medusa: on tentacles, 7.9 ± 0.3 µm [7.0– 8.5, N= 20]; on circular canal, 10.7 ± 0.5 µm [10.0– 11.5, N= 20]. Bell transparent; gonads, manubrium, bulbs and tentacles assuming the colour of food. Female medusae not seen.
Distribution. Known from São Sebastião and Ilhabela, SP, Brazil ( Migotto 1996) and the type-locality, St. Thomas, U.S. Virgin Islands ( Stechow 1914), but reports of C. hemisphaerica and C. gracilis from other western Atlantic localities may also have been based on the species.
Biological notes. Clytia elsaeoswaldae is one of the most abundant shallow-water hydroids occurring off the coast of São Sebastião and Ilhabela, southeastern Brazil (see Migotto 1996, as C. hemisphaerica ). Some colonies growing on Sargassum have several hundred hydranths and gonangia, and a few hours after collecting even small fragments of such colonies were observed to release several hundred medusae in the laboratory.
Only small size differences were observed among colonies of C. elsaeoswaldae from southeastern Brazil ( Table 2), and all fertile colonies had gonangia growing exclusively on the hydrorhiza. Colonies from Brazil are also similar to the syntypes from off the U.S. Virgin Islands, which also have gonothecae exclusively on the hydrorhiza (as noticed by Stechow 1914: 125) but differ in having smaller gonothecae ( Table 2). This difference, however, is only in size, and the shape of the gonothecae is similar, with a mean width:length ratio of 0.4 ( Table 2). The specimens from Brazil and the Virgin Islands also differ slightly in that the hydrothecal cusps are less tilted and their tips more acute in the latter specimens, but otherwise all specimens are similar in both shape and size ( Table 2). Because of permanent preservation in microslides, cnidome of syntypes could not be determined and DNA sequences could not be obtained, and we regard the specimens from southeastern Brazil conspecific to those from the Virgin Islands on the basis of perisarc morphology.
Medusae of C. elsaeoswaldae are released with small gonads, eight statocysts, and either four or six tentacles. After 2 days of culture at 22–24 °C, medusae attained up to 8 tentacles, and after six days additional statocysts started to develop between perradial and adradial marginal bulbs. D-type nematocysts on the exumbrella disappeared during medusa development, as well as C-types in the tentacles. Maximum diameter of the umbrella (i.e., 5.5 mm) was reached after 12 days, and no additional growth was observed until the culture ended 21 days after liberation [maximum diameter of the umbrella, on average: 4.8 mm (N= 5) on the 14 th day; 4.9 mm (N= 10) on the 16 th day; 4.6 mm (N= 10) on the 20 th]. New statocysts continue to develop after medusae reached their maximum size: up to 16 and 21 statocysts in 12 and 20 days old medusae, respectively. Maximum number of fully developed tentacles varied from 12 to 16.
Phylogenetics. The combined maximum likelihood analysis indicates that Clytia elsaeoswaldae and other Clytia gracilis -like species do not form a monophyletic group ( Figure 4 View FIGURE 4 ). Similarly, none of the four genes support a monophyletic C. gracilis clade when analyzed individually or in mitochondrial (16 S and COI) and nuclear (18 S and calmodulin) partitions (results not shown). The phylogenetic results show that the here re-described C. elsaeoswaldae is most closely related to a clade including C. hemisphaerica and two C. gracilis -like species (species A and B in Figure 4 View FIGURE 4 ).
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