Research Article |
Corresponding author: Koen Martens ( darwinula@gmail.com ) Academic editor: Ivana Karanovic
© 2023 Koen Martens, Vitor Góis Ferreira, Nadiny Martins de Almeida, Janet Higuti.
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:
Martens K, Ferreira VG, de Almeida NM, Higuti J (2023) On Caledromus robinsmithi, a new genus and species of Psychrodromini Martens, 2001 (Crustacea, Ostracoda, Herpetocypridinae) from New Caledonia (Pacific Ocean). ZooKeys 1165: 155-182. https://doi.org/10.3897/zookeys.1165.104045
|
The New Caledonian Archipelago is a hot spot for biodiversity and endemism. Whereas popular groups such as birds and plants are well-studied, invertebrate groups such as ostracods remain ill-known. Here, Caledromus robinsmithi gen. et sp. nov. is described from a single locality on ‘Grande Terre’, the main island of the archipelago. The new genus belongs to the Psychrodromini, one of the four tribes in the subfamily Herpetocypridinae (family Cyprididae). Caledromus gen. nov. can be distinguished from all other herpetocypridinids by a combination of the following factors: the absence of marginal septa in both valves, the mildly developed marginal valve structures, the small Rome organ on the A1, the total reduction of the five natatory setae on the A2, the rectangular second palp segment of the Mx1, the broad and asymmetrical palp on the female T1, the absence of additional postlabyrinthal coils in the Hp and the seta Sp of the CR which is a fixed spine. Because of the close similarity to the genus Psychrodromus, the new genus is thought to have Palaearctic affinities, contrary to other ostracod species in New Caledonia, which are either circumtropical or with Australian zoogeographical connections.
Chaetotaxy, Cyprididae, hemipenis internal anatomy, morphology, taxonomy
The New Caledonian archipelago, situated in the Pacific Ocean, north-east of Australia, has high levels of endemic biodiversity, which has attracted the attention of botanists, zoologists and biogeographers alike (
Tribe Herpetocypridini Kaufmann, 1900 |
Candonocypris Sars, 1896 |
Herpetocypris Brady & Norman, 1889 |
Ilyodromus Sars, 1894 |
Paranacypris Higuti, Meisch & Martens, 2009 (change of position) |
Thaicypris Savatenalinton, 2021 |
Additional useful (recent) references: |
|
Tribe Isocypridini Rome, 1965 |
Amphibolocypris Rome, 1965 |
Isocypris G.W. Müller, 1908 |
Platycypris Herbst, 1957 |
Additional useful (recent) references: |
Tribe Psychrodromini Martens, 2001 |
Caledromus gen. nov. |
Humphcypris Martens, 1997 |
Psychrodromus Danielopol & McKenzie, 1977 |
Somalicypris Martens, 1997 |
Additional useful (recent) references: |
Tribe Stenocypridini Ferguson, 1964 |
Acocypris Vávra, 1895 |
Ampullacypris De Deckker, 1981 |
Chrissia Hartmann, 1957 |
Stenocypria G.W. Müller, 1901 |
Stenocypris Sars, 1889 |
Additional useful (recent) references: |
|
For three years (2016–2018), the Muséum national d’Histoire naturelle (Paris, France) organised the New Caledonia Hydrobiological expeditions under the “Our Planet Reviewed/ La Planète revisitée” programme. Two of the authors (JH and KM) participated in these expeditions and collected more than 350 samples from a variety of water bodies and have found close to 50 species of living non-marine Ostracoda of which about half are expected to be new to science. Thus far, Cyprinotus drubea
The subfamily Herpetocypridinae Kaufmann, 1900 is one of the most speciose of the 25 subfamilies in the family Cyprididae Baird, 1845 (
Here, we describe a new genus and species, Caledromus robinsmithi gen. et. sp. nov. of the subfamily Herpetocypridinae Kaufmann, 1900 from New Caledonia.
New Caledonia is an archipelago in the south-west Pacific. It is located 1500 km to the north of New Zealand and 1500 km to the east of Australia (Fig.
The present material was collected by JH and KM during the 2018 expedition to New Caledonia.
Ostracods were collected by moving a rectangular hand net (28 × 14 cm, mesh size ~ 160 μm) either over sediment (to whirl up the top layers with living biota) or amidst aquatic vegetation. We measured pH (VWR/pH/1100H) and electrical conductivity (EC) / water temperature (VWR/CO/3100H) in situ. The position of the type locality on the Grand Terre is illustrated in Fig.
Soft parts were separated from the valves using dissection needles and were then put in a drop of glycerine for the dissection of the appendages. The dissection was covered with a coverslip and sealed with transparent nail polish. Valves were stored dry in micropaleontological slides. Drawings of soft parts were made using a camera lucida (Olympus U-DA) attached to the microscope (Olympus CX-41). Carapace and valves were illustrated and measured using Scanning Electron Microscopy (SEM, Fei Qanta 200 ESEM, in the Royal Belgian Institute of Natural Sciences, Brussels, Belgium) in different views and details.
Type material is lodged in the
Muséum national d’Histoire naturelle (
Chaetotaxy of the limbs follows the model proposed by
Valves and carapaces:
Cp carapace;
CpD carapace in dorsal view;
CpRL carapace in right lateral view;
CpV carapace in ventral view;
H height of valves;
L length of valves;
LVi left valve in internal view;
RVi right valve in internal view;
W width of valves.
Limbs:
a, b, d setae on T1;
A1 antennula;
A2 antenna;
alfa, beta, and gamma setae on Md-palp;
Att attachment of the CR;
CR caudal ramus;
d1, d2, dp, e, f, g, h1, h2, h3 setae on T2 and T3;
db, vb distal branches of Att;
ds1, ds2 lobes of distal shield of Hp;
g, t1-4, z1-3 setae on female A2;
G1-3, Gm, GM claws on female A2;
Ga, Gp, Sa, Sp claws and setae on the CR;
Hp hemipenis;
Lpp Left Prehensile palp;
Md mandibula;
Md-palp mandibular palp;
M/F Male/Female;
ms medial shield on Hp;
Mx1 maxillula;
T1 first thoracopod;
T2 second thoracopod;
T3 third thoracopod;
R Rome Organ;
Rpp Right Prehensile Palp;
Y, Ya, y3 aesthetascs.
Class Ostracoda Latreille, 1802
Subclass Podocopa G.O. Sars, 1866
Order Podocopida G.O. Sars, 1866
Suborder Cypridocopina Baird, 1845
Superfamily Cypridoidea Baird, 1845
(adapted from
Al in some genera with large, multi-segmented Rome organs. A2 in males with larger claw Gm developed into a comb-like structure, with one row of strong teeth. C well-developed, symmetrical or asymmetrical; Att of the CR with a triangular basal reinforcement (in some genera only weakly developed). Hp with large and sclerotised bladder-like part ‘c’ of the labyrinth, postlabyrinthal internal spermiduct with up to 6 additional coils.
see Table
(adapted from
Caledromus gen. nov. (here allocated); Humphcypris Martens, 1997; Psychrodromus Danielopol & McKenzie, 1977; Somalicypris Martens, 1977.
The character “additional postlabyrinthal coils of the inner spermiduct in the Hp” refers to coils that cover most of the internal parts of the Hp, including the labyrinth, before the normal ventral coils which lead to the bursa copulatrix; see
Caledromus robinsmithi gen. et sp. nov.
Cale from the New Caledonian archipelago and dromus to indicate the close relationship to the genus Psychrodromus.
A genus typical of the Psychrodromini and closely related to Psychrodromus. Cp in dorsal view compact and rather wide, LV overlapping RV on all sides. A1 with small Rome-organ consisting of one segment only. A2 with natatory setae reduced to setulae or fully absent. Mx1-palp with second segment cylindrical (rectangular in slide), with L longer than basal W. T1 in female with broad palp, distally skewed and set with three very short setae. T2 with seta d1 ~ 2× the length of seta d2. CR symmetrical, proximal seta Sp an unmoveable spine. Hp without extra coils of the inner postlabyrinthal spermiduct.
The genus is presently monospecific and endemic to New Caledonia.
New Caledonia • North Province, Village of Poindimié in the area of the valley of the Necaapwé (sample HYNC2569). Coordinates: 20°57.165'S, 165°21.71'E. Altitude: 35 m. Collected on 28.05.2018. Road-side pool. Leg.: JH and KM. Holotype, allotype and paratypes all from the type locality (Fig.
Holotype
• 1 ♂ (adult); dissected and stored on a permanent microscopic slide and valves stored dry in a micropalaeontological slide (
Allotype
• 1 ♀ (adult); dissected and stored as the holotype (
Paratypes
• 3 adult ♂♂ Cp (RBIN-INV-197990,
Muséum national d’Histoire naturelle, Paris, France (
the species is named after Dr Robin Smith (Kusatsu, Shiga, Japan), in recognition of his significant contribution to research on non-marine ostracods, especially on those of the ancient Lake Biwa, and with much appreciation of years of friendship with KM.
Cp robust and rather wide in dorsal view. LV overlapping RV on all sides, but especially along posterio-dorsal and entire anterior side. Valve surface not striated, but set with random grooves, small pits, and rimmed pores around stiff setae. RV with inner list, LV with posterior marginal selvage. A1 with Rome-organ small, consisting of one segment. A2 with five natatory setae fully absent, only accompanying seta present; male with claw GM with hyper-developed row of spines. Md-palp with alpha and beta setae both short and elongated. Mx1-palp with second segment cylindrical (rectangular in the dissection), with L ~ 1.5× basal width. T1 in female with large, inflated, and asymmetrical palp, distally with three short setae; setae b, d and a present, seta d longer in the male than in the female. Prehensile palps in male both with sickle-shaped second segment, in Rpp longer than in Lpp. T2 with seta d1 ~ 2× as long as d2. T3 with a distal pincer-shaped organ. CR without sexual dimorphism, with robust ramus, seta Sp an unmoveable claw, seta Sa longer than claw Ga, the latter almost straight, claw Gp distally curved. Attachment of CR with proximal triangular re-enforcement, branch vb almost straight, branch db curved backwards. Hp with asymmetrically rounded ms without hook-like expansion; ds consisting of two parts, ds1 rectangular and distally situated, ds2 rounded and situated mid-dorsally; internal anatomy without additional coils of the postlabyrinthal spermiduct. Zenker organ elongated, with ~ 20 coils.
Male. Cp in lateral view (Fig.
Caledromus robinsmithi gen. et sp. nov., male A LVi (
Caledromus robinsmithi gen. et sp. nov., female A LVi (
LVi (Fig.
Caledromus robinsmithi gen. et sp. nov. A–F female G–I male A LVi, photographed at tilted angle, showing inner anatomy of anterior side (
RV (Fig.
A1 (Fig.
A2 (Fig.
Md with coxal plate (Fig.
Caledromus robinsmithi gen. et sp. nov. ♂ A Md-palp (respiratory plate not illustrated) (
Rake-like organ (Fig.
Caledromus robinsmithi gen. et sp. nov. ♂ A T1, without prehensile palps (see Fig.
Mx1 (Fig.
T1 (Figs
T2 (Fig.
T3 (Fig.
Caledromus robinsmithi gen. et sp. nov. A–F ♂ G ♀ A T3 (
CR (Fig.
Att (Fig.
Hp (Fig.
Zenker organ (Fig.
Female (only sexual dimorphism with males given). Cp (Fig.
A2 (Fig.
T1 (Fig.
Female copulatory organs (not illustrated) as typical of the subfamily, i.e., rounded, slightly elongated structures with few visible internal or external features.
See Table
Caledromus robinsmithi gen. et sp. nov., measurements of illustrated specimens.
Slide/specimen nr | Valve/Cp | M/F | L (μm) | H (μm) | W (μm) |
---|---|---|---|---|---|
|
LV | M | 925 | 456 | |
|
RV | M | 897 | 448 | |
|
LV | M | 908 | 451 | |
|
RV | M | 882 | 447 | |
|
LV | M | 985 | 491 | |
|
RV | M | 968 | 485 | |
|
CpRL | M | 931 | 466 | |
|
CpD | M | 921 | 497 | |
|
CpV | M | 907 | 456 | |
|
LV | F | 997 | 485 | |
|
RV | F | 975 | 482 | |
|
LV | F | 971 | 490 | |
|
RV | F | 955 | 482 | |
|
LV | F | 1023 | 510 | |
|
RV | F | 989 | 502 | |
|
CpRL | F | 992 | 485 | |
|
CpD | F | 1035 | 535 | |
|
CpV | F | 976 | 503 |
The species is presently known from its type locality only: a shallow roadside pool, with water coming from a small stream; with terrestrial plants, grasses and “Songe” on sediment consisting of gravel and mud (Suppl. material
Every taxonomic hierarchy is a working hypothesis, to be tested by using new characters or new methods, or by the discovery of new taxa. Especially in cases where different characters show different distribution patterns in taxa, it can be difficult to determine which characters show the correct phylogeny and which are homeomorphic (see for example, discussion in
The most important synapomorphy to unite all Herpetocypridinae is the presence of a supporting triangular chitinous structure at the base of the CR Att (
The marginal valve anatomy, including the width of the fused zone, the morphology of the marginal pore canals (single or branched), the presence of false pore canals (as in Herpetocypris), and generally the presence or absence and the morphology of selvages and inner lists are important characters which define genera and tribes. The fact that valves in this group are bearing such clear identifiable characteristics also allows fossils to be readily identified (
Within the Herpetocypridinae, the Rome Organ on the A1 has a plastic morphology. For example, within the Herpetocypridini, the genera Candonocypris and Herpetocypris have invariably small Rome organs. Amongst species of Ilyodromus, however, this organ can be longer than the actual segment on which it is situated and can be two- and even three-segmented. Most other genera in the Herpetocypridinae have small Rome Organs, but in Ampullacypris (Stenocypridini) even this small organ can be two-segmented (
The length of the natatory setae on the A2 can vary greatly, even between species of the same genus (see for example Humphcypris). However, except for Caledromus robinsmithi where the five natatory setae have completely disappeared, in the other genera and species of the subfamily some small remnants always remain. Even in the presently described species without any trace of the natatory setae, the accompanying seta is still present and not reduced, which clearly shows that this seta has a developmental program which is unrelated to those of the actual natatory setae. The inverse situation occurs in Brasilocypria
In males of several species and genera of Herpetocypridinae (e.g., Herpetocypris, Humphcypris, Somalicypris, Caledromus, and others, but not in Thaicypris), the male A2 has a the larger claw Gm set with a row of long spines, which are absent in females. Some Cypridopsinae, e.g., the African Zonocypris G.W. Müller, 1898 and the Brazilian Cabelodopsis Higuti & Martens, 2012, have a similar morphology, but the hyperdeveloped claw occurs in females only.
The shape of the second segment of the Mx1 palp is important in the taxonomy of the Herpetocypridinae, as species in the tribes Herpetocypridini and Isocypridini have spatulate segments, while species in the tribes Stenocypridini and Psychrodromini have cylindrical palp segment, which show up as rectangular structure in the dissections (see discussion on the position of the genus Paranacypris below).
The useful characters of the T1 are mostly those related to the morphology of the male prehensile palps, but also the presence/absence, shape and length of the setae d, b, and a can be useful in the taxonomy of several groups. In the present species, both males and females have asymmetrical setae b and d, with lengths varying between left and right sides. It is the first time that this is being reported in this group, but it is a feature which is rarely observed and described for both limbs of the same individual. The new genus Caledromus is characterised by the presence of a wide and broad female T1-palp with very small apical setae, an autapomorphic feature, and therefore useful to identify this taxon, but not helpful regarding taxonomic placement of the genus. Also, several other characters are autoapomorphic for one genus and not informative for phylogenetic studies. One example is the monospecific genus Stenocypria, where the sinuous posterior inner margin of the female valves of S. fischeri (Lilljeborg, 1883) results from a lobe-shaped expansion of the calcified inner lamella. This calcified lobe is absent in the males (
The morphology of the female T1-palp in C. robinsmithi is interesting from an evolutionary point of view, as the morphology of this palp resembles that of the shape of prehensile palps in A-1 males. This could thus be a case of heterochronic development, of which several examples exist in non-marine ostracods, for example in the African and Australian terrestrial representatives of the subfamily Scottiinae Bronshtein, 1947 (see
The potential relevance of the presence/absence and length ratios of the d1 and d2 setae on the T2 for the identification at the genus level has already been stressed several times (see
The differences in the morphology of the seta Sa on the CR (with character states: simple seta, moveable claw-like seta, immobile spine, fully absent) were amongst the first reasons that drove
The Hp, in species and genera in which males are known, comprises useful taxonomic information. Mostly, external Hp morphology can be used to identify species within genera. Here, however, the morphology of the inner spermiduct, with between 0 (in Caledromus) and 6 (in Somalicypris) additional postlabyrinthal coils (see definition above) allows divisions even at the level of tribes (see diagnoses in Martens, 2001). The illustrated Hp of Thaicypris (in
Based on the set of characters described above and on the diagnoses of the four tribes in the Herpetocypridinae (see
Although several ostracod species from the New Caledonian expeditions still await description, the ones that were reported from this archipelago (see table in
The New Caledonia Hydrobiological expeditions 2016–2018 (PI: Philippe Bouchet, who is thanked profusely) are part of a cluster of expeditions under the ‘Our Planet Reviewed / La Planète revisitée’ programme, implemented by the Muséum national d’Histoire naturelle (
VGF and NMA would like to thank CAPES for granting their scholarship, VGF also for his doctoral sandwich scholarship Financial code 001, which included a 6-month stay in Brussels.
JH acknowledges CNPq for the research productivity grant. The State University of Maringá (UEM, Maringá) and the Royal Belgian Institute of Natural Sciences (
We thank Claude Meisch (Luxembourg) and Dan Danielopol (Austria) for useful comments which improved the manuscript.
No conflict of interest was declared.
No ethical statement was reported.
No funding was reported.
KM and JH conceptualised the project and collected the material. VGF and NMA provided the illustrations and the descriptions. All authors contributed to writing of the manuscript.
Koen Martens https://orcid.org/0000-0001-8680-973X
Vitor Góis Ferreira https://orcid.org/0000-0002-5244-7707
Nadiny Martins de Almeida https://orcid.org/0000-0002-4380-125X
Janet Higuti https://orcid.org/0000-0002-3721-9562
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Type locality of Caledromus robinsmithi gen. et sp. nov.
Data type: (measurement/occurrence/multimedia/etc.)