A new species of Parasesarma (Brachyura, Sesarmidae) from Western Australia, with a key to the species from Australia

275 A new species of Parasesarma (Brachyura, Sesarmidae) from Western Australia, with a key to the species from Australia Adnan Shahdadi1, Andrew M. Hosie2, Ana Hara2, Benny K. K. Chan1 1 Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan 2 Collections and Research, Western Australian Museum, Welshpool, Western Australia 6106, Australia Corresponding author: Andrew M. Hosie (andrew[email protected].au) Copyright: © Adnan Shahdadi et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0). Research Article Abstract Nine species of Parasesarma are currently recorded from continental Australian mangroves. The present study describes a new species, P. otiense sp. nov., from Western Australia. Parasesarma otiense sp. nov. occurs sympatrically with P. hartogi and P. holthuisi in the mangroves of Exmouth Gulf. In both COX1 and 16S BI trees, the new species is well nested within Parasesarma, but divergent from other species. Morphologically, the new species is distinct from other Parasesarma in having eight asymmetric tubercles with the distal slope longer than the proximal slope on the upper surface of the cheliped dactylus. Parasesarma otiense is the tenth species of Parasesarma recorded from continental Australia, taking the number of species assigned to the genus Parasesarma to 59. A key to the species of Parasesarma known from Australian waters is provided to aid in their identification. Key words: Crustacea, COX1, mangrove crab, molecular taxonomy, morphology, Parasesarma otiense Introduction Brachyuran crabs of the genus Parasesarma De Man, 1895 are among the most common components of mangroves and estuaries (Lee 1998, 2015) and this genus has been the subject of significant recent taxonomic research. Based on molecular and morphological analyses, Shahdadi and Schubart (2018) transferred most species of Perisesarma De Man, 1895 to Parasesarma, and Shahdadi et al. (2020) transferred most of the long-legged species of Parasesarma to a new genus Leptarma Shahdadi, Fratini & Schubart, 2020. Currently, Parasesarma includes 58 species distributed across the Indo-West Pacific, with highest species diversity in Southeast Asia (Shahdadi et al. 2018, 2020, 2023). Nine species of Parasesarma have been recorded from continental Australian mangrove habitats, with approximately half of the species endemic to either the eastern or western coasts, with some potential overlap zones along the northern coast between the Kimberley region of Western Australia to the Gulf of Carpentaria and eastern Cape York Peninsula in Queensland (Davie 1985). Parasesarma lividum (A. Milne-Edwards, 1869), P. brevicristatum (Campbell, 1967), and P. erythodactyla (Hess, 1865) have been recorded from the east coast (Campbell 1967; Davie 1993; Shahdadi et al. 2019). Parasesarma longicristatum Academic editor: Ingo S. Wehrtmann Received: 6 July 2025 Accepted: 17 September 2025 Published: 13 October 2025 ZooBank: https://zoobank.org/ C4B844F6-3D4D-46A1-A04C05F21CEF0396 Citation: Shahdadi A, Hosie AM, Hara A, Chan BKK (2025) A new species of Parasesarma (Brachyura, Sesarmidae) from Western Australia, with a key to the species from Australia. ZooKeys 1255: 275–290. https://doi. org/10.3897/zookeys.1255.162897 ZooKeys 1255: 275–290 (2025) DOI: 10.3897/zookeys.1255.162897 276 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia (Campbell, 1967) and P. messa (Campbell, 1967) have a wider distribution from the east to the north coasts (Campbell 1967; Shahdadi et al. 2018). Parasesarma darwinense (Campbell, 1967), P. austrawati Shahdadi, Davie & Schubart, 2019, P. holthuisi (Davie, 2010), and P. hartogi Davie & Pabriks, 2010 have been recorded from northern to western coasts (Campbell 1967; Davie 2010; Davie and Pabriks 2010; Shahdadi et al. 2019). In addition to these species, P. sigillatum (Tweedie, 1950) is endemic to the Australian Indian Ocean Territory of the Cocos (Keeling) Islands (Ng et al. 2016). The integrated molecular and morphological analyses of recent studies (e.g. Shahdadi et al. 2018, 2020; Shih et al. 2023) have provided a framework for new taxonomic research by clarifying the placement and the morphological delimitation of many species that were described during the 19th and early 20th centuries. The present study uses sequence data from specimens across a range of species and integrates this with morphology to describe a previously unknown species. Material and methods Specimens were collected during different expeditions conducted by the Western Australian Museum: NCB Exmouth Muirons in 2016, Bush Blitz Cape Range in 2019, Environs Kimberley Broome in 2023, and Kimberley Reef Connect in 2023. Specimens were collected by hand from different localities (see material examined and Suppl. material 1) along the intertidal fringing mangroves and associated mud flats during low tides. The specimens were fixed in 96% ethanol and preserved in 75% ethanol. They were transferred to the Western Australian Museum (WAM), Perth, for further morphological examination and tissue subsampling for DNA extraction. All specimens are housed in the WAM or the Biodiversity Research Museum, Biodiversity Research Center, Academia Sinica, Taiwan (ASIZ). Abbreviations used are as follows: bp: base-pairs; coll.: collected; cl: carapace length along the midline; cw: maximum carapace width; P2–P5: pereiopods 2–5, respectively (first to fourth ambulatory legs, respectively); G1: male first gonopod. Measurements are in millimetres (mm). The description is based on the holotype male with ranges and variations given in parentheses for paratypes, followed by female specific characters observed in the female paratype. Genomic DNA was isolated from muscle tissue using the Qiagen DNeasy extraction kit (Qiagen, Hilden, Germany) following the manufacturer’s protocol. A partial segment of the mitochondrial protein-coding gene cytochrome c oxidase subunit 1 (COX1), corresponding to the barcode region (Hebert et al. 2003), and a partial segment of 16S ribosomal DNA (16S) were selected as the most commonly used genetic markers in species delimitation in Parasesarma (e.g. Shahdadi et al. 2018). The polymerase chain reactions (PCRs) were performed using dgLCO1490 5′-GGTCAACAAATCATAAAGAYATYGG-3′ as forward primer and dgHCO2198 5′-TAAACTTCAGGGTGACCAAARAAYCA-3′ as reverse primer (Meyer 2003) for COX1; and 16L29 5′-YGCCTGTTTATCAAAAACAT-3′ as forward primer and 6H11 5′-6H11 AGATAGAAACCRACCTGG-3′ as reverse primer (Schubart 2009) for 16S. The PCR reactions were performed using 12.5 μl ThermoScientific DreamTaq Green PCR Master Mix (2×), 0.75 μl of each primer (10 μM), 1 μl of template DNA, and 10 μl of distilled water. The PCRs were conducted in a DNA Thermal Cycler T100 (Bio-Rad, Richmond, CA, USA) with the following profiles: an initial 7 cycles of 25 s at 95 °C, 25 s at 52 °C and 40 s at 277 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia 72 °C; followed by 35 cycles of 25 s at 95 °C and annealing for 25 s at 46 °C for COI and 48 °C for 16S, 40 s at 70 °C for extension; and a final extension step of 7 min at 72 °C. New sequences were submitted to GenBank (https://www.ncbi. nlm.nih.gov/) and are available under accession numbers (Table 1). Sequences were assembled, proofread, and the primer regions were removed using Geneious Prime (https://www.geneious.com). Further quality control was undertaken through checking for stop codons in the translated sequence and checking for matches with non-target taxa on Blast (https://blast.ncbi.nlm.nih.gov/ Blast.cgi). Sequences of other Parasesarma were downloaded from GenBank (https://www.ncbi.nlm.nih.gov/genbank/) and used for phylogenetic analyses. Sesarmoides longipes (Krauss, 1843), Fasciarma fasciatum (Lanchester, 1900), and Perisesarma dussumieri (H. Milne Edwards, 1853) were used as outgroups (see phylogenetic trees in Shahdadi et al. 2018, 2020) (for the accession numbers see Figs 1, 2, the phylogenetic trees). The sequences were aligned with ClustalW (Thompson et al. 1994) implemented in BioEdit 7.0.5 (Hall 1999). Available sequences of COX1 cover more species of Parasesarma, compared to the available sequences of 16S. We, therefore, conducted phylogenetic analysis for each gene separately. To address the phylogenetic positions of the new material, a Bayesian Inference (BI) was conducted in BEAST 2.7.7 (Drummond and Rambaut 2007) for each gene. We used the Yule Model (as prior for tree model) and a strict clock model. Markov Chains were run for 10 million generations, sampling every 1,000 iterations and discarding the first 10% as burn-in. The remaining 9,000 trees were used to calculate the maximum clade credibility Table 1. GenBank accession numbers for the sequences generated for this study. Specimen COI 16S Parasesarma austrawati WAM C83749 PV871721 WAM C84089 PV871717 PV882444 WAM C84101 PV871718 PV882443 Parasesarma hartogi WAMC74531 PV871707 WAMC74563 PV871709 WAMC74687 PV871711 WAMC74688 PV871712 WAMC74815 PV871714 Parasesarma holthuisi WAMC74519 PV871704 WAMC74524 PV871706 WAMC74554 PV871708 WAMC74817 PV871715 WAMC84088 PV871716 PV882442 Parasesarma longicristatum WAMC74814 PV871713 PV882441 Parasesarma otiense sp. nov. WAMC74411 PV871703 PV882436 WAMC74523 PV871705 PV882440 WAMC74686 PV871710 PV882437 WAMC86047 PV871719 PV882438 ASIZCR000470 PV871720 PV882439 278 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia tree in Tree Annotator (part of the BEAST package). The best evolutionary models were TIM2+F+I+G4 for COX1, and TIM+F+I+G4 for 16S as determined by using ModelFinder (Kalyaanamoorthy et al. 2017) through the IQ-TREE web server (http://iqtree.cibiv.univie.ac.at/?user=guest&jobid=241119083607) (Trifinopoulos et al. 2016) based on BIC scores. To calculate genetic distances (p-distance) we used MEGA X (Kumar et al. 2018). 0.03 P. prashadi MT020720 P. kuekenthali MT020713 P. asperum MT020712 WAMC84088 P. holthuisi P. guttatum KX400903 P. austrawati MH552903 P. batavianum MT020718 Perisesarma dussumieri KX400916 P. gemmatum LC510467 P. hartogi KX400928 P. peninsulare KX400890 P. turkayi KY198241 P. bengalense KX400902 P. austrawati MH552907 P. persicum MT020721 P. continentale OQ940732 ASIZCR000470 P. otiense sp. nov . P. austrawati MH552902 P. pictum MT020719 P. holthuisi KX400907 Fasciarma fasciatum KX400921 P. luomi MT023416 WAMC74686 P. otiense sp. nov. WAMC74531 P. hartogi P. rahayuae OR026028 WAMC74563 P. hartogi P. capensis MT020728 P. tripectinis MT020716 P. austrawati MH552906 WAMC74688 P. hartogi WAMC74411 P. otiense sp. nov. P. austrawati MH552905 P. semperi KX400910 P. cricotum KX400897 P. lanchesteri KX761168 P. eumolpe KX400891 WAMC86047 P. otiense sp. nov. P. ungulatum KX400930 P. maipoense KX400931 WAMC74524 P. holthuisi P. corallicum MT020722 P. daviei MW429845 WAMC74523 P. otiense sp. nov. P. messa KX431205 P. insulare OQ940775 P. ellenae MT023410 P. anambas LC510452 P. lepidum MW429839 P. samawati KX400895 Sesarmoides longipes KX400923 P. charis MT020715 P. melissa MF564015 P. catenatum MT020709 WAMC84101 P. austrawati P. affine MT020717 P. chiahsiang LC510462 WAMC74817 P. holthuisi P. raouli MT020714 WAMC74814 P. longicristatum P. dumacense KX400929 WAMC74519 P. holthuisi P. plicatum KX400912 WAMC74554 P. holthuisi WAMC74815 P. hartogi P. calypso MT020733 P. lividum KX400893 P. darwinense KX400904 WAMC84089 P. austrawati WAMC74687 P. hartogi P. austrawati MH552904 P. austrawati MH552908 P. sanguimanus LC510481 P. bidens KX761166 P. longicristatum KY198240 P. indiarum KX761164 WAMC83749 P. austrawati P. brevicristatum KX400906 P. onychophorum KX400913 1 1 0.98 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0.98 0.98 1 1 1 0.95 0.9 1 1 0.98 1 1 0.99 Figure 1. Bayesian Inference phylogram constructed in BEAST 2.7.7 for COX1 sequences of Parasesarma. The numbers behind the nodes refer to the support values (posterior probability) (posterior probabilities under 0.90 are not shown). Sequences belonging to Sesarmoides longipes, Fasciarma fasciatum, and Perisesarma dussumieri were used as outgroups. The numbers in front of species names are GenBank accession numbers. Sequences obtained in the present study are shown in red and the newly described species are in bold font (the numbers left to species names are Western Australian Museum numbers). 279 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia Results Phylogeny In the present study we obtained 19 sequences of COX1 (three for P. austrawati, one for P. longicristatum, five for P. hartogi, five for P. holthuisi, and five for the new species) and nine sequences of 16S (two for P. austrawati, one for 0.02 Sesarmoides longipes KX423829 P. melissa MZUF2597 P. insulare OQ942096 P. capensis MT021424 P. corallicum MT021417 P. guttatum KX423816 Perisesarma dussumieri KX423814 P. pictum MT021414 P. lividum KX423802 P. catenatum MT021399 WAMC74411 P. otiense sp. nov. P. semperi MF173039 WAMC84101 P. austrawati P. tripectinis MT021411 ASIZCR000470 P. otiense sp. nov. P. samawati KX423821 WAMC74814 P. longicristatum P. cricotum KX423796 P. dumacense KX423837 P. austrawati MH552897 P. affine MT021412 P. kuekenthali MT021407 P. sanguimanus KX423820 P. bidens KX761172 P. peninsulare MT021421 P. bengalense KX423810 P. brevicristatum KX423800 P. anambas MT021410 P. persicum MT021416 P. gemmatum MT021426 P. batavianum MT021413 P. messa KX423795 P hartogi KX423836 P. luomi MT021418 WAMC74523 P. otiense sp. nov. P. onychophorum KX423812 P. ungulatum KX423838 P. charis MT021409 WAMC86047 P. otiense sp. nov. P. darwinense KX423798 P raouli MT021408 P tuerkayi KY198247 WAMC84089 P. austrawati P. indiarum KX761171 P. eumolpe KX423811 P. chiahsiang OQ942146 Fasciarma fasciatum KX423824 P. sigilatum MT021425 P. plicatum KX423823 P. lanchesteri KX761174 P. asperum MT021406 P. longicristatum KY198245 WAMC84088 P. holthuisi P. continentale OQ942078 P prashadi MT021415 P. holthuisi KX394813 WAMC74686 P. otiense sp. nov. 0.91 1 1 1 1 0.98 0.99 0.91 1 0.99 1 0.99 1 1 1 0.95 0.92 1 0.91 1 1 1 1 Figure 2. Bayesian Inference phylogram constructed in BEAST 2.7.7 for 16S sequences of Parasesarma. The numbers behind the nodes refer to the support values (posterior probability) (posterior probabilities under 0.90 are not shown). Sequences belonging to Sesarmoides longipes, Fasciarma fasciatum, and Perisesarma dussumieri were used as outgroups. The numbers in front of species names are GenBank accession numbers. Sequences obtained in the present study are shown in red and the newly described species are in bold font (the numbers left to species names are Western Australian Museum numbers). 280 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia P. holthuisi, one for P. longicristatum, and five for the new species). Phylogenetic analyses confirmed the morphological identifications of P. austrawati, P. hartogi, P. holthuisi, and P. longicristatum as the new sequences of these species grouped stably with the sequences of their types (Figs 1, 2). In both COX1 and 16S trees, however, some sequences formed a well-supported sub-clade that is genetically divergent from other species of Parasesarma. This sub-clade is therefore identified as a new species. Although well nested within the clade of Parasesarma with a well-supported basal node, the COX1 and 16S phylogenies were not able to find any close phylogenetic allies of this new species. Parasesarma prashadi (Chopra & Das, 1937) was sister to P. otiense sp. nov. in the COX1 tree, with a p-distance of 8.4%. In the 16S tree, P. onychophorum (De Man, 1895) and P. melissa (De Man, 1887) formed a clade as sister to the new species. Parasesarma otiense sp. nov. was 7% divergent from the P. onychophorum + P. melissa clade, while P. onychophorum and P. melissa were 4.2% divergent from each other. Systematic account Family Sesarmidae Dana, 1851 Genus Parasesarma De Man, 1895 Parasesarma otiense sp. nov. https://zoobank.org/515F271B-6A51-4A70-A087-382922061A5D Figs 2–4 Material examined. Holotype. Australia • WAM C74523, male (14.0 × 11.0); Western Australia, Exmouth Gulf, Bay of Rest mangroves (22°18'54"S, 114°7'33"E); 21 June 2019; Bush Blitz Cape Range; coll. Hosie, A. M. & Hara, A. Paratypes. • WAM C74411, male (12.1 × 9.8); Western Australia, Exmouth Gulf, Bay of Rest mangroves (22°18'44"S, 114°7'38"E); 4 June 2016; NCB Exmouth Muirons; coll. Hosie, A. M. & Hara, A. • WAM C74686 male (6.5 × 5.4); Western Australia, Exmouth Gulf, Bay of Rest mangroves (22°18'54"S, 114°7'33"E); • WAM C86047, Female (9.4 × 7.6); Western Australia, Exmouth Gulf, Bay of Rest mangroves (22°18'44"S, 114°7'38"E); 4 June 2016; NCB Exmouth Muirons; coll. Hosie, A. M. & Hara, A. • ASIZCR000470 male (8.6 × 6.8), Western Australia, Exmouth Gulf, Bay of Rest mangroves (22°18'44"S, 114°7'38"E); 4 June 2016; NCB Exmouth Muirons; coll. Hosie, A. M. & Hara, A. Diagnosis. Ambulatory legs relatively long, P4 longest, ~1.7 × cw. Carapace rectangular, broader than long, dorsal surface smooth, front moderately deflexed, shallowly sinuous in dorsal view, median postfrontal lobes as wide as lateral ones. Eyestalk longer than wide, cornea wider than eyestalk. Chelipeds without subdistal spine on dorsal border of merus; male chela with 2 transverse pectinated crests on the upper surface of palm, dactylus with 8 asymmetric tubercles with proximal slope shorter than distal slope, tubercles with transverse keel and wrinkles. Male pleon triangular, somite 2 medially longer than lateral edges. G1 stout, straight, apical corneous process relatively long, bent at an angle of ~45° to vertical axis, aperture subterminal. Description (morphometrics based on the holotype but with variation and ranges in parentheses). Carapace (Figs 3A, C, 4A, 5A) rectangular, broader than long, greatest width between exorbital angles, cw/cl = 1.27 (1.20–1.27); dorsal 281 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia surface smooth and shiny (Fig. 3A, C); front in holotype ~0.55 × cw (0.55–0.58), moderately deflexed, shallowly sinuous in dorsal view; postfrontal lobes distinct, median lobes as broad as lateral lobes, separated by well-pronounced furrow (Fig. 3A, C); dorsal regions well indicated, gastric region demarcated, cardiac region not well separated from intestinal region; lateral branchial ridges prominent; anterolateral margin with sharp exorbital angle directed anteriorly; lateral margins straight with no indication of epibranchial tooth, edged with row of short setae. Eyestalk longer than wide, cornea wider than eyestalk (Fig. 3C). Chelipeds similar (Figs 3A, B, 4A); chelae (Figs 3E, F, G, 4B, C) large, palm length 0.76 × cw, robust, palm length 1.77 × palm width. Merus with finely granulate dorsal border, but no subdistal spine; ventral border granulate; anterior border granulate, with large subdistal spine; inner face smooth with a longitudinal row of setae. Upper surface of palm with 2 transverse pectinated crests and 2 or 3 crests consisting of granules (Figs 3F, 4C), distal (primary) crest composed of 14 or 15 tall teeth (varying on opposite claws of holotype), secondary crest well developed, with 13 teeth; both crests ending on inner side in short swollen, tubercular ridge and several small granules at outer side; upper margin of palm distal to pectinated crests Figure 3. Parasesarma otiense sp. nov., holotype, WAM C74523, male (14.0 × 11.0), Western Australia, Exmouth Gulf, Bay of Rest mangrove. A. Dorsal habitus; B. Frontal view; C. Carapace, dorsal view; D. Pleon and mouth; E. Right chela, outer view; F. Left chela, dorsal view; G. Dactylus of right chela, dorsal view. 282 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia with some setae (Fig. 3F); outer surface of palm with fine granules, with granules forming a line on fixed finger (Figs 3E, 4B); inner surface of palm with granules but no vertical ridge; ventral border of chela sinuous with granules; length of cutting margin of fixed finger of holotype ~0.4 × length of entire propodus. Dactylus (Figs 3E, F, G, 4B, C) straight in outer view but slightly curved inward, ~0.6 × propodus length in holotype; dorsal surface bearing 8 rounded asymmetric tubercles with proximal slope shorter than distal slope, distinct to tip, tubercles with transverse keel and wrinkles, creating step-like shape for each tubercle, proximal tubercles positioned at inner part of upper dactylar face, row of small rounded tubercles on proximal half of inner edge of dorsal surface; fingers with chitinous tips, cutting edge of both fingers with a series of variably sized teeth. Ambulatory legs (Figs 3A, 4A, 5A) relatively long; P4 longest, length (ischium–dactylus) 1.66 × cw (1.62–1.78), merus with anterior margin crenulated, ~2.3 × as long as wide, propodus ~3.2 × as long as wide, dactylus length ~0.8 × length of propodus. Male pleon (Fig. 3D) triangular; telson slightly shorter than basal width, slightly longer than somite 6; somite 6 longer than others; somite 5 and 4 trapezoidal, somite 3 widest, laterally convex, somite 2 medially longer than lateral edges. G1 (Fig. 3D–G) stout, straight, stem triangular with blunt angles in cross-section; apical corneous process relatively long, bent at an angle of ~45° to vertical axis, tip rounded, aperture subterminal. Figure 4. Parasesarma otiense sp. nov., paratype, WAM C74411, male (12.1 × 9.8), Western Australia, Exmouth Gulf, Bay of Rest mangrove. A. Dorsal habitus; B. Left chela, outer view; C. Left chela, dorsal view; D–G. Left G1; D. Full dorsal view; E. Distal tip, dorsal view; F. Distal tip, ventral view; G. Distal tip, dorsal view, denuded. 283 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia Females (Fig. 5) with proportionally smaller chelipeds than males, palm length 0.50 × cw; pectinated crest absent on palm, replaced by rows of granules; dactylus with 8 small but distinct, round tubercles. Pleon (Fig. 5B) broad, rounded, broadest at somites 3 and 4, fringed with long setae, touching coxae of ambulatory legs. Vulva (Fig. 5C) in depression on anterior edge of sternite 6, operculum oval, parallel and touching line of sternite 5, oval operculum in anterior part of vulva. Etymology. The species name is derived from the Latin noun otium, meaning rest, and the gender-neutral suffix, -ense, in reference to the type locality, the Bay of Rest in Exmouth Gulf, Western Australia. Habitat. Intertidal fringing mangrove and associated mud flat. Discussion Parasesarma otiense sp. nov. co-occurs with P. hartogi and P. holthuisi (see comparative material listed in Suppl. material 1) within the Bay of Rest but differs in carapace morphology, with no sign of epibranchial teeth (Fig. 3C). In contrast, P. hartogi (see Davie and Pabriks 2010: fig. 1B) has a distinct epibranchial projection and P. holthuisi (see Davie 2010: fig. 1B) has a small but clearly incised epibranchial tooth. The cheliped dactylus in P. otiense sp. nov. is straight with eight distinct rounded, asymmetric tubercles (Fig. 3E–G), rather than downcurved Figure 5. Parasesarma otiense sp. nov., paratype, WAM C86047, Female (9.4 × 7.6), Western Australia, Exmouth Gulf, Bay of Rest mangrove. A. Dorsal habitus; B. Ventral habitus; C. Vulvae (Op = operculum). 290 ZooKeys 1255: 275–290 (2025), DOI: 10.3897/zookeys.1255.162897 Adnan Shahdadi et al.: New species of Parasesarma from Western Australia Supplementary material 3 COX1 BI tree in nexus format Authors: Adnan Shahdadi Data type: nexus format file Explanation note: Bayesian Inference tree of COX1 data. Copyright notice: This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Link: https://doi.org/10.3897/zookeys.1255.162897.suppl3 Supplementary material 4 16S BI tree in nexus format Authors: Adnan Shahdadi Data type: nexus format file Explanation note: Bayesian Inference tree of 16S sequence data. Copyright notice: This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Link: https://doi.org/10.3897/zookeys.1255.162897.suppl4