Santjordia pagesi, Lindsay & Grossmann & Montenegro & Morandini, 2023

Lindsay, Dhugal John, Grossmann, Mary Matilda, Montenegro, Javier & Morandini, André Carrara, 2023, A new subfamily of ulmarid scyphomedusae, the Santjordiinae, with a description of Santjordia pagesi gen. et sp. nov. (Cnidaria: Scyphozoa: Discomedusae: Semaeostomeae: Ulmaridae) from the Sumisu Caldera, Ogasawara Islands, Japan, Zootaxa 5374 (4), pp. 533-551 : 538-543

Santjordia pagesi sp. nov.

( Figs. 1–5 )

New Japanese name: Sekijuujikurage

Synonymy

“ Ulmaridae gen. et sp. ” Kitamura et al. 2008: 320, fig. 24.57.

“ Ulmaridae gen. et sp. nov. ” Hidaka et al. 2021: 52.

Holotype

NSMT-Co-1800 — One specimen captured by the ROV Hyper-Dolphin during Dive 84 on 10 March 2002 at a depth of 812 m (temperature 10.2˚C, salinity 34.30, dissolved oxygen 2.8 ml/L, Sigma T 26.37) within the hydrothermally active Sumisu Caldera (31˚28’N 140˚04’E) in the Izu-Ogasawara Islands south of the Japanese mainland . The reference video file (in situ) in the JAMSTEC High-quality Video Database is HPD0084-20020310-103457.9343- SHHD-Front- 1920x 1080_HDCAM-1o4--NoImpose-Santjordia_pagesi-Dhugal_Lindsay-SEKIJUUJIKURAGE-812.9 m-20020310T013457.9343Z.mov and a transcoded “lightweight” version is accessible on Zenodo ( Lindsay 2022a). Images taken in the shipboard laboratory within the gate sampler ( Lindsay 2022c) and microscope images of tentacle squashes ( Lindsay 2022d) are available online on Zenodo.

Other Material

A second individual was observed at 843 m depth (temperature 10.1˚C, salinity 34.35, dissolved oxygen 2.8 ml/L, Sigma T 26.43). The reference video file is HPD0084-20020310-105552-SHHD-Front- 1920x 1080_HDCAM-1o4- TC10555217to10561003DF-NoImpose-Santjordia_pagesi-Dhugal_Lindsay-SEKIJUUJIKURAGE----Santjordia_ pagesi_842.8m.mov and a transcoded “lightweight” version is accessible on Zenodo ( Lindsay 2022b).

Holotype Description

Umbrella hemispherical; 100 mm diameter, 72 mm height; scattered with nematocysts; mesoglea thick, transparent. Margin cleft into 8 broad lobes (lappets). Eight rhopalia (4 perradial, 4 interradial) located in clefts at margin; 24 additional adradial rhopalia located on the subumbrellar surface but protruding through tear-drop-shaped perforations in the velar lobes (3 per octant) ( Figs 2 , 3f ). Tentacles subumbrellar; up to 60 per quadrant; located in pits in 2 rows along inner [proximal] and outer [distal] surfaces of ring canal; tentacle pits demarcated by rhopaliar canals and other less obvious subumbrellar gelatinous ridges; single tentacle at base of each adradial canal just proximal of where it joins ring canal, not in a pit; tentacle bases light pink when alive, cream in formalin. Tentacle nematocysts composed of small holotrichous a-isorhizas (average length 8.91±0.74 µm, average width 5.09±0.42 µm; range 7.3–11.0 µm×4.2–6.6 µm; n=95) and heterotrichous microbasic birhopaloids (average length 11.63±0.98 µm, average width 8.24±0.24 µm; range 10.0–12.6 µm×7.8–8.5 µm; n=10) ( Fig. 5 ). Subumbrellar musculature not discernible. Subgenital ostia absent. Manubrium height equal to or slightly greater than bell radius; surrounded by thick transparent mesoglea with inner surface red-pigmented. Four V-shaped oral arms; bases fused and following outline of cross-shaped stomach; tips protruding below umbrella rim; with transparent papillae on tips and inner edges, thick transparent mesoglea extends to distalmost ends of oral arms, inner surfaces red-pigmented. Central stomach cross-shaped, red when alive, dark brown in formalin; gastric cirri in 4 pairs of perradial groups, whitish in live specimen; radial canals simple, not anastomosing, similar width throughout length, connected by a ring canal located ~1/3 bell radius away from margin; short rhopaliar canals emanating from ring canal to all sense organs; 4 perradial canals, one each emanating from centre of distal tips of stomach base; 4 interradial canals, one each emanating from centre of stomach base; 8 adradial canals, two each emanating from distal tips of stomach base, one at each corner, not in direct communication with perradial or interradial canals. Gonads not recognized.

Etymology

The species name is in honour of Dr. Francesc Pagès, who hosted the first author during his sabbatical in Barcelona and introduced him to the intricacies of cnidarian taxonomy.

Molecular Phylogeny

The analysis of sequences of the mitochondrial 16S gene using maximum likelihood (ML) and Bayesian methods gave congruent tree topologies ( Fig. 6 ). Robust support was evident for the semaeostome clades Drymonematidae and Cyaneidae , and for another clade including the ulmarid subfamilies Poraliinae and a member of the Ulmarinae, but also including the recently erected family Phacellophoridae . In fact, higher support was evident for Diplulmaris (Ulmarinae) and Phacellophora ( Phacellophoridae ) being more closely related to each other than for a close relationship between some of the ulmarid genera investigated. Somewhat surprisingly, there was reasonable support for Santjordia pagesi gen. et sp. nov. belonging to a sister group to a clade including the ulmarid subfamilies lacking marginal tentacles—Stygiomedusinae + Tiburoniinae + Deepstariinae . A BLAST search for the COXI sequence returned a maximum percentage identity of 82.62% with a query cover of 95% matched with Aurelia coerulea , with the next closest match being Rhopilema aff. esculentum at 82.21% and 97%, respectively. These low values are indicative of the COXI marker not being suitable for resolving higher phylogenies and further analysis was not attempted. Sequences determined in the present study have been registered on GenBank under accession numbers ON391151-ON391163 for 16S and ON496462 for the single COXI sequence, belonging to Santjordia pagesi gen. et sp. nov. All sequences used in the molecular analysis are listed in Tables 1 and 2. Images of sequenced specimens, where available, are available online on Zenodo ( Lindsay 2022a –k).

Remarks

The medusa was swimming upwards at a pulse rate of 0.4 Hz at a depth of 812 m and an altitude of 101 m above the bottom. Only two individuals were observed over 91 minutes of observation time during descent below the caldera rim at 400 m depth inside the Sumisu Caldera, and no individuals were observed during a second dive during descent to a maximum depth of 893 m above the outer wall slope of the caldera on the previous day (31°29.1′N, 140°09.3′E; total observation time below 400 m: 115 min). Compared to environmental parameters outside the caldera in the open ocean, temperature at 812 m depth was elevated within the caldera (10.2˚C vs 5.5 ˚C), as was the dissolved oxygen concentration (2.8 ml/L vs 1.7 ml/L). The oceanographic environment within the Sumisu Caldera is described and discussed in more detail by Hidaka et al. (2021). The caldera wall around this depth is comprised of monomictic lava breccia, coherent facies or talus blocks, while most of the caldera floor is covered with pumiceous sand and pebbles with some lobes of coarser debris ( Tani et al. 2008). Other organisms observed in the same depth layer as Santjordia pagesi gen. et sp. nov. included the calycophoran siphonophore Clausophyes sp. (see Hidaka et al. 2021), pyrosomes ( Pyrosomatidae spp.) (see Hidaka et al. 2021), euphausiids, sergestid shrimps, the hyperiid amphipod Platyscelus ovoides , a presently undescribed species of lobate ctenophore with vestigial auricles (Undescribed Lobata “No auricles” of Hidaka et al. 2021), and cydippid larvae of at least one species of lobate ctenophore (“Cydippid larvae” of Hidaka et al. 2021).

Figures

FIGURE 1. In situ images of the holotype of Santjordia pagesi gen. et sp. nov. Top left: aboral-lateral view; top right: lateral view; bottom left: oral-lateral view; bottom right: lateral view within the gate valve sampler on the ROV Hyper-Dolphin. Specimen size = 100 mm diameter.

FIGURE 2. Schematic diagram of Santjordia pagesi gen. et sp. nov. with morphological terminology.

FIGURE 3. Santjordia pagesi gen. et sp. nov. Holotype. a: photograph of lateral view of living specimen in the gate sampler; b: photograph of aboral view of living specimen in the gate sampler; c: sketch of lateral view of living specimen; d: sketch of aboral view of living specimen; e: sketch of portion of oral view of preserved specimen; f: close-up of adradial rhopalium of preserved specimen, showing exumbrella with cleft, statocyst and rhopaliar canal; g: close-up of oral arm of living specimen in the onboard aquarium, showing marginal papillae. Scale bar = 2 cm except f: scale bar = 1 mm.

FIGURE 4. Close-up photograph of subumbrella of preserved specimen of Santjordia pagesi gen. et sp. nov. holotype showing tentacle disposition. Sketch of subumbrella photograph, labelled with morphological characters. Scale bar = 1 mm.

FIGURE 5. Photograph montage of a tentacle squash from the preserved specimen of Santjordia pagesi sp. nov. holotype showing nematocyst size and morphology. Scale bar = 10 µm.

FIGURE 6. Phylogenetic reconstruction based on the 16S-rDNA region for Scyphozoa. Values at nodes indicate ML bootstrap support>50%, and solid circles represent Bayesian probabilities>0.95.