Research Article |
Corresponding author: Julian Uribe-Palomino ( julian.uribepalomino@csiro.au ) Academic editor: James Reimer
© 2018 Julian Uribe-Palomino, Sarah Pausina, Lisa-ann Gershwin.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Uribe-Palomino J, Pausina S, Gershwin L-A (2018) (2018) Two new species of Hydromedusae from Queensland, Australia (Hydrozoa, Leptothecata). ZooKeys 783: 17-36. https://doi.org/10.3897/zookeys.783.26862
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Two new species of small hydromedusae were found during routine monitoring in coastal waters of eastern Australia and are here described. The first, Melicertissa antrichardsoni Uribe-Palomino & Gershwin, sp. n., from Moreton Bay, Queensland, is placed in its genus because of its possession of both cordyli and eight-fold symmetry. It differs from its congeners in two conspicuous features: firstly, having small, oval split gonads located adjacent to the base of the stomach, and secondly, in its extremely small size at maturity (2 mm bell diameter, compared to the next smallest species at 7 mm). Moreover, it possesses a unique combination of other characters. This species appears to be endemic to Moreton Bay. The second new species, Paralovenia yongalensis Gershwin & Uribe-Palomino, sp. n., from the Great Barrier Reef, Queensland, is placed in its genus because of its two opposite normal tentacles and two opposite marginal clusters of cirri. It differs from its congeners primarily in a more rounded body than the others; the shape, length, and position of its short spindle-shaped, distal gonads; possession of subumbrellar nematocyst clusters; and possession of statocysts. These discoveries bring the total number of Melicertissa species to eight and the total number of Paralovenia species to three. The discovery of these two micromedusae underscores the need for further examination of the often-ignored minute and/or gelatinous fauna.
coastal ecology, endemic, gelatinous zooplankton, Great Barrier Reef, IMOS, Laodiceidae , Lovenellidae , Medusozoa , systematics, taxonomy
Increasing global scientific attention on jellyfish has focused mostly on large and conspicuous species; however, approximately 90% of jellyfish species are small and rarely noticed (
Around Australia, gelatinous zooplankton are now routinely monitored along with other plankton, under the umbrella of the Australian Plankton Survey, a collaboration between the Integrated Marine Observing System (IMOS) and the Commonwealth Scientific Industrial Research Organisation (CSIRO). Four recent sampling programs under this umbrella have collected numerous specimens comprising two species of hydromedusae new to science.
Seven species of the genus Melicertissa have been described since it was proposed by Haeckel in 1879. Five of those species have been found in tropical and subtropical waters of the northern hemisphere. The remaining two species, M. orientalis Kramp (1961) and M. rosea
Here, we describe two new species from Queensland coastal waters, the first, Melicertissa antrichardsoni sp. n., is based on a few specimens collected in Moreton Bay, and the second, Paralovenia yongalensis sp. n., is based on a single specimen from tropical waters of the GBR. Both new species constitute the most southerly record for their respective genus. Neither of these species has been found in any other area of Australia or the world, suggesting endemism to eastern Australian waters. The purpose of this paper is to describe these two new species, thus adding to our baseline knowledge of Australia’s marine biodiversity.
Specimens were collected as part of four separate studies in Queensland, Australia, three in the subtropics and one in the tropics. The locations where the specimens were found and the distribution of their congeners is shown in Figure
Study 1: University of Queensland PhD project (Sarah Pausina), four specimens December 2010 to April 2011. Specimens were collected as part of a study on the zooplankton community dynamics within Moreton Bay, a shallow subtropical embayment. Stations along a salinity and nutrient gradient were sampled from the eutrophic Brisbane River mouth to the oligotrophic, oceanic-influenced Rous Channel. A 0.2 m mouth diameter, 100 µm mesh net fitted with a non-filtering cod-end (0.75 L) was towed horizontally within 1 m of the surface at approximately 1 m s-1 for 3-5 minutes during daylight hours.
Study 2: CSIRO, 3 specimens, March to December 2011. Specimens were collected as part of a project to evaluate the impact of the January 2011 Brisbane floods on the Moreton Bay area. Samples were collected every three months for one year from 13 sites around Moreton Bay, using a conical net with a 0.5 m diameter mouth and 100 μm mesh. The net was towed for 2 minutes at 1.5–2 knots following a linear transect collecting samples from the surface to 2 m deep.
Study 3: IMOS and CSIRO, 3 specimens, May 2013 and April 2014. Qualitative samples were collected as a supplement to the Moreton Bay plankton monitoring project. These samples were collected from Rous Channel in eastern Moreton Bay using a conical net of 0.5 m mouth diameter and 140 μm mesh. The net was towed at 1.5–2 knots following a linear transect collecting samples from the surface to 2 m deep.
Study 4: IMOS and CSIRO, 1 specimen, September 2016. The specimen was collected during routine monitoring of zooplankton at the IMOS National Reference Station near the SS Yongala shipwreck site, south-east of Townsville, Queensland, Australia. The sample was collected during a vertical tow descending from the surface to 28 m depth, using a conical net with a mouth diameter of 0.6 m and 100 μm mesh.
Samples collected from the different projects were fixed and preserved in 10% formalin.
All specimens were examined in a preserved state. Bulk samples were sorted under a Leica M165C stereo microscope. Specimens were photographed with a Canon EOS-5D camera adapted to the microscope by a 2.5x Leica optical tube. High quality images of the specimens were produced by stacking multiple pictures from different depth planes with Helicon focus 6.7.1 software.
Nematocyst slides from M. antrichardsoni sp. n. were prepared as described in
Distribution maps were produced using the packages ‘map’ and ‘mapdata’ for the statistical computing and graphics software R 3.3.3 (R-Project) and the application RStudio 1.1.136 (RStudio).
Non-English descriptions were converted to text with OnlineOCR (https://www.onlineocr.net/) and translated online with Google Translate (https://translate.google.com.au/). Abbreviations used in the text: Bell diameter (BD) and stomach diameter (SD).
?Melicertiasa Haeckel, 1879 [incorrect spelling of Haeckel’s genus]:
Holotype: QM G335899, Male, BD ca. 2 mm, tentacles six well developed and two rudimentary (Figures
Paratypes: QM G335904, Lot of two specimens, both male, BD ca. 2 mm, SD ca. 1 mm, hemi-gonad: 0.8 mm × 0.3 mm, tentacular bulbs seven, one clearly missing, base ca. 0.6 mm diameter (Figure
QM G335903, very poor condition, BD ca. 2 mm (Not figured), Moreton Bay, Queensland, Australia, 27.38°S, 153.39°E, 1 m, (Study 1), coll. S. Pausina, 19 Apr 2011.
QM G335902, Male, BD ca. 2.4 mm, hemi-gonad: 0.8-0.9 mm x 0.3 mm, tentacle bulbs seven (five well developed, plus two small ones), base ca. 0.6 mm (Figure
QM G335900, Male, flattened specimen, BD ca. 2 mm. (Not figured); Moreton Bay, Queensland, Australia, 27.28°S, 153.08°E, (Study 2), (CSIRO MB74), 1-2 m, coll. CSIRO, 19 Dec 2011.
QM G335901, Female, flattened specimen, eigth tentacles, BD ca. 2 mm (Figure
QM G335905, QM G335906, microscope slide nematocyst preparations, Moreton Bay, Queensland, Australia, 27°S, 153°E, coll. CSIRO, 19/3/2011-20/5/2013 (Figure
Melicertissa with pairs of small oval hemi-gonads near the base of each radial canal; with eight tentacles and approximately two cordyli and one statocyst between successive tentacles; with an extremely small body size at maturity (ca. 2 mm).
Umbrella isosceles trapezoid-shaped in lateral view, aborally flattened, with the margin curving inwards at the edges, possibly due to preservation (Figure
Tentacles eight, six fully developed and two incompletely developed; hollow; coiled; more or less evenly located around the bell margin (Figure
Cordyli club-shaped with a swollen end and slender stalk, almost half as long as the tentacle bulbs (Figure
Between adjacent cordyli typically lies another structure different in form, here interpreted as a statocyst. Compared to the tapered stalk of the cordylus, this structure is more evenly columnar or thimble-shaped with straight sides and a rounded distal end (Figure
Stomach amorphously round-ish, broad, nearly 1/2 BD in width (Figure
Radial canals eight, relatively broad, straight-sided throughout length, clearly visible from the stomach to the ring canal (best illustrated in Figure
Gonads in eight pairs of oval hemi-gonads straddling each radial canal adjacent to the stomach, occupying the proximal third of each radial canal (Figure
Colour not noted in living specimen, but preserved specimen has a transparent bell with brown gonads, tentacle bulbs and stomach.
Melicertissa antrichardsoni sp. n. A Non-type specimen lost during study, inverted, note dark pigmenting of tentacle bulbs and ocelli (arrow) B Holotype QM G335899, cordylus, note cap-like position of nematocysts C Holotype QM G335899, cordylus, detail of nematocysts D Paratype QM G335902, note conspicuous radial canals (e.g., arrow) E tentacular nematocysts F nematocyst from whole body squash (QM G335905 and QM G335906 collectively). Scale bars: 1 mm (A, D); 50 µm (B, C); 20 µm (E, F).
Moreton Bay, Queensland, Australia.
One specimen (QM G335901) has lumpy gonads with obvious ova (Figure
Three of the specimens (two in lot QM G335904, and one in QM G335902) are each missing one tentacle bulb; these are not variants in merosity, but rather, they are octamerous with one bulb simply absent (Figure
Paratypes have a transparent and colourless bell and cordyli, pale yellowish gonads, and darkly pigmented tentacle bulbs. A black ocellus is found at the base of each tentacle and cordylus (Figure
Melicertissa antrichardsoni sp. n. has a cnidome of two size classes of oval cnidae on the tentacles (Figure
On the tentacles, the larger size class is nearly 19 μm long by 10 μm wide, and bears a conspicuous barb on the free (= aboral) end of the undischarged shaft; we interpret this type as a stenotele. The smaller size class is approximately half the size of the larger, and bears a conspicuous v-shaped notch on the free (= aboral) end; we interpret this type as a microbasic p-mastigophore.
On the cordyli, nematocysts are scattered throughout the tip in a distal cap. The cordyli nematocysts are similar in shape but smaller in size (8 μm) than the small size class on the tentacles. However, we were unable to observe internal structures and were unable study them directly (Figure
The specific epithet, antrichardsoni, is given to honour Professor Anthony J. Richardson of CSIRO and the University of Queensland. Anthony has encouraged and supported the research of plankton from Moreton Bay and around Australia through the Australian Plankton Survey.
Melicertissa antrichardsoni has been found throughout the warmer months of the year from December to May, in salinities from 26–34 PSU and water temperatures from 18.84–26.5°C.
Melicertissa antrichardsoni is the eighth species in the genus (Table
Summary of main features from each one of the known species of Melicertissa. Data from original species descriptions along with
Species | BD | Bell shape | Stomach | Mouth | Gonads | Tentacles | Cordyli | Ocelli | Cirri | Locality |
---|---|---|---|---|---|---|---|---|---|---|
M. adriatica Neppi, 1915 | 46 mm | Flatter than hemisphere, with thick jelly | Short | 8 short crenulated lips | Linear along length of RC | 24 | 3–5 between adjacent tentacles | On each cordylus | More # than cordyli | Adriatic sea |
M. clavigera Haeckel, 1879 | 10 mm | Flat to hemispherical; jelly thin | Flat, or in a long narrow manubrium | Quadratic, drawn into 4 or 8 short lips | Foliaceous along most of RC, thicker in middle half | 8, with thick conical base | 3 between adjacent tentacles | On tentacles and cordyli | (Not indicated) | Canary Islands |
M. malayica (Maas, 1905) | 32 mm | Flat | Very flat | 8-lobed | Linear on proximal 1/3 of RC, slender, tapering | >160, with slight bulbous swelling | At irregular intervals between tentacles | ~ 5–6 per octant at base of some tentacles | Sparser than cordyli | Malay Archipelago |
M. mayeri Kramp, 1959 | 7 mm | Flatter than hemisphere; with moderately thin walls | Flat | 8 short, simple lips | Somewhat sinuous, upon the middle half of RC | 16, with long, hollow, tapered bulbs | 16 | 32 | (Not indicated) | Tortugas, Florida |
M. orientalis Kramp, 1961b | 11 mm | Flatter than hemisphere; fairly thick jelly | Flat and broad | 8 faintly indicated lips with a smooth margin | Wavy, lateral bands with about 5 extensions, on distal 2/5 of RC | 17, with heart-shaped bulb | 1–3, mostly 2, between adjacent tentacles | Black, on base of tentacles and cordyli | (Not indicated) | Green Island, Great Barrier Reef |
M. platygastra Nair, 1951 | 7 mm | Watch-glass shaped, very thick in centre | Flat, half as wide as BD | 8 lanceolate lips with thick wavy margins | Linear on outer half of RC in 3 continuous lumps | 8, short stumpy, with large conical bulbs | 4–6 in each octant | 12–14 dark ocelli per octant | (Not indicated) | Trivandrum coast, India |
M. rosea Bouillon, 1984 | 10 mm | (Not indicated) | 1/3 BD | Formed into 8 folds | Foliaceous, almost as long as RC | 40 | 40 | At base of tentacles and cordyli | (Not indicated) | Papua New Guinea |
M. antrichardsoni sp. n. Uribe-Palomino & Gershwin | 2 mm | Isosceles trapezoid | Flat and broad, about half BD | 8-lobed, with smoothly-rounded lips | 8 pairs of oval hemi-gonads close to stomach | 8, with heart-shaped bulbs | ~ 2 between tentacles, plus a statocyst between | Black, at base of tentacles and cordyli | Not observed | Moreton Bay, Queensland |
Compared to the other species with eight tentacles, namely M. clavigera
Finally, Melicertissa antrichardsoni would be unlikely to be confused with M. malayica
One may wonder about the relationship between M. orientalis
With the specimens of M. antrichardsoni at only two millimetres in diameter, it is logical to ask whether they might be juveniles. However, this is unlikely as the female specimen (QM G335901) appears to have mature ova and is near the same size as the other specimens. Specimens have been found on numerous occasions throughout the summertime over a period of five years.
Curiously,
We recognise Melicertissa adriatica
Holotype: QM G335907. Female, BD ca. 1.47 mm, tentacular bulbs two and two non-tentacular clusters of cirri (Figures
Paralovenia with a relatively short, bell-shaped body with a truncated apex; with well-developed spindle-shaped gonads in the distal half of radial canals, not reaching the margin; with two opposite perradial triangular bulbs bearing tentacles, and two similar opposite perradial bulbs each bearing approximately 10–12 cirri; with open statocysts on a broad conical base; nematocysts arranged in flat roundish clusters on the subumbrellar surface.
Paralovenia yongalensis sp. n., Holotype QM G335907. A habitus; note conical statocyst-like structure (indicated by red arrow) B Aboral view of stomach (cruciform structure closest to the viewer) and mouth (quadratic structure away from the viewer) C Oral view of margin (note that the gonads are the darkest brown structures, and the mouth is the quadratic structure near the upper left). Black arrows in A and C: tentacular bulbs indicated by solid arrows and bulbs bearing cirri indicated by dashed arrows. Scale bars: 0.5 mm (A); 250 µm (B, C).
Umbrella bell- to barrel-shaped, broadest about 2/3 of the way down, truncate to slightly indented aborally (Figure
Tentacles two, opposite, on voluminous, triangular perradial basal bulbs, approximately 250 μm across the base (Figures
Other marginal structures: opposite the radial canal associated with one of the tentacle bulbs bearing cirri, there exists a small gelatinous “thorn” projecting outward (Figures
Stomach small, cruciform at base (Figure
Radial canals four, straight sided throughout length clearly visible from the stomach to the ring canal, approximately 30 μm in diameter and expanded proximally to create mesentery-like connections with the stomach (Figure
Gonads four, spindle-shaped, starting approximately half way from the stomach toward the margin, covering 2/5 of the entire length of the radial canal, absent on the distal fifth of the radial canal (Figure
Paralovenia yongalensis sp. n., Holotype QM G335907. A Gonad with egg follicles (upper left; 2nd right gonad in habitus photo in Figure
Near the shipwreck SS Yongala, south-east of Townsville, Queensland, Australia.
No nematocyst preparation was made because the only available specimen is the holotype and it is too small to take sections from without destroying it. Therefore, the following description of nematocysts is based on in situ observation only. Bell nematocysts are mostly in roughly circular clusters up to 30 μm in diameter on the subumbrellar surface. Each cluster consists of 4–20 nematocysts. The nematocysts are oval in shape and approximately 12 μm long and half as wide (Figure
Paralovenia yongalensis sp. n., Holotype QM G335907. A Magnified view of cirri cluster; note statocyst-like structure (red circle) and two sizes of nematocysts on coiled cirrus (arrows) B Detail of nematocysts in bulb (upper left arrow) and cirrus (lower right arrow). Scale bars: 100 µm (A); 50 µm (B).
The specific name yongalensis is given honouring the area where people lost their lives on board the SS Yongala that sank not far away from Cape Bowling Green, Queensland, in 1911. This area is a popular scuba diving site and it is also the location of one of the IMOS National Reference Stations. This is not to be confused with the town from South Australia of the same name.
The specimen was collected in a vertical drop net from the surface to 28 m in an area of maximum 30 m depth; we therefore do not know its exact location in the water column. The sea surface temperature at the time was 27.5 °C.
Like its congeners, Paralovenia yongalensis has two opposite tentacles and two opposite clusters of short cirri. However, the gonad shape and position immediately distinguish it from the others (Table
Whereas P. bitentaculata
Summary of main features from each of the known species of Paralovenia. Data from original species descriptions. Abbreviations: bell height (BH), radial canals (RC).
Species | BH | Body shape | Stomach | Mouth | Gonads | Tentacles | Cirri | Sense organs | Locality |
---|---|---|---|---|---|---|---|---|---|
P.
bitentaculata
|
1.4 mm | Deep bell, piriform | Short | 4 lips, with a quadrangular manubrium | Voluminous, cylindrical, occupying central ¾ of RC | 2 opposing, on large, conical, bulbous bases | 2 opposing clusters of 6, on bulbs smaller than those bearing tentacles | Statocysts and ocelli absent | Papua New Guinea |
P. latigaster Xu & Huang (2004) | ~ 2 mm | Deep bell, piriform | Large, broad | Not described | Voluminous, cylindrical, extending along each RC from the stomach nearly to the margin | 2 opposing, on large, conical, bulbous bases | 2 opposing clusters of up to 12 | Statocysts absent; ocelli not specified | Taiwan Strait, China |
P. yongalensis sp. n. Gershwin & Uribe-Palomino | 1.4 mm | Short bell, truncated apex; with subumbrellar nematocyst clusters | Short, cruciform | Mouth perfectly quadrangular, with a short quadrangular manubrium | Voluminous, spindle-shaped, in distal half of RC, well separated from the margin | 2 opposing, with large broad bulbs | 2 opposing clusters of 10–12 solid straight cirri | Ocelli absent; statocysts open, on broad conical base | Great Barrier Reef, Australia |
The cirri of P. yongalensis are more similar in number to P. latigaster, while the stomach is small, like that of P. bitentaculata; P. yongalensis differs from both in having a relatively shorter, rounder body, and shorter, more spindle-shaped gonads, tapered at both ends. Moreover, P. yongalensis is approximately the same size as P. bitentaculata.
The cirri are worthy of discussion.
Interestingly, P. yongalensis has a few flat round clusters of nematocysts on the subumbrellar surface. Neither
Similarly, the conical statocyst-like structure in P. yongalensis is very interesting to us.
We recognise the value of providing DNA sequences as molecular evidence to support the description of new species when it is practical. In the present case, all the specimens were preserved in formalin, making successful extraction of DNA unlikely. Moreover, with so few specimens of Melicertissa and only one specimen of Paralovenia, we consider the morphological approach to be the less-destructive method to characterise these two new species.
Finally, while we believe that the fully-developed gonads for both species suggest that they are mature specimens, this hypothesis may be tested using DNA sequencing in future research.
We are grateful to the following people for helping in sample collection: Study 1: We thank DSITI Aquatic Ecosystem Health for assistance with sample collection. Water quality data was provided by the Ecosystem Health Monitoring Program and Healthy Waterways Ltd. This study was funded by the Australian Research Council Linkage Grant LPO883663.
Study2: (in alphabetical order) Geoff Carlin, Nagur Cherukuru, Phillip Ford, Jim Franklin, Gary Fry, Andrew Lowe, Sean Maberly, Kadija Oubelkheir, Peter Ralph and Andy Steven.
Study 3: (in alphabetical order) Frank Coman, Claire Davies, Felipe Gusmao and Mark Tonks.
Thank you Frank Coman and Claire Davies for checking the manuscript and we are also grateful to the two reviewers for their constructive comments, Merrick Ekins and James Reimer.