First Zoeal Stage of 15 Species of Fiddler Crabs (Crustacea: Brachyura: Ocypodidae) from Taiwan

© 2022 Academia Sinica, Taiwan Open Access Special issue: Systematics and Biogeography of Fiddler Crabs First Zoeal Stage of 15 Species of Fiddler Crabs (Crustacea: Brachyura: Ocypodidae) from Taiwan Ying-Chen Zhang1 and Hsi-Te Shih1,2,* 1Department of Life Science, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 402, Taiwan. E-mail: [email protected] (Zhang) 2Research Center for Global Change Biology, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 402, Taiwan. *Correspondence: E-mail: [email protected] (Shih) Received 1 January 2022 / Accepted 13 June 2022 / Published 16 November 2022 Communicated by Benny K.K. Chan Special issue: Systematics and Biogeography of Fiddler Crabs (articles 64–71). Editors: Hsi-Te Shih and Benny K. K. Chan Fiddler crabs (Brachyura: Ocypodidae: Gelasiminae) in Taiwan consist of 5 genera and 15 species, but knowledge of their larval development is limited to just 3 species, namely Austruca lactea, Tubuca arcuata, and Xeruca formosensis. In our study, the morphology of the first zoeal stage (zoea I) of the 15 species is described and compared to previous studies. The results show that the characters of zoea I can be used to distinguish the five studied genera and most species (except three groups, “Gelasimus borealis, G. jocelynae and G. vocans”, “Paraleptuca crassipes and P. splendida” and “Tubuca arcuata, T. coarctata and T. paradussumieri”). The lateral spines on the carapace in zoea I are suggested to be a unique character in the Ocypodinae because they are absent in the Gelasiminae and Ucidinae, which supports the current systematics of the Ocypodidae. Key words: Larva, Morphology, Systematics, Austruca, Gelasimus, Paraleptuca, Tubuca, Xeruca. BACKGROUND The larval morphology of brachyuran crabs plays an important role in brachyuran systematics because it is less influenced by convergence and environmental adaptation than adult morphology (Rice 1980). Some characters of larval morphology have already been used in the diagnosis of the superfamily Majoidea Samouelle, 1819 (Hultgren and Stachowicz 2008), family Xenograpsidae N.K. Ng, Davie, Schubart & Ng, 2007 (NK Ng et al. 2007), genera Eriocheir De Haan, 1835 sensu lato (NK Ng et al. 1999) and Scandarma Schubart, Liu & Cuesta, 2003 (Schubart et al. 2003), and even species, such as Hemigrapsus penicillatus (De Haan, 1835) and H. takanoi Asakura & Watanabe, 2005 (Landeira et al. 2019). Fiddler crabs (family Ocypodidae Rafinesque, 1815) are brachyuran crabs that inhabit intertidal areas. There are 107 described species encompassing 11 genera, including all members in the subfamily Gelasiminae Miers, 1886, as well as the genera Afruca Crane, 1975 and Uca Leach, 1814 in the subfamily Ocypodinae Rafinesque, 1815 (Shih et al. 2016a 2018 2019; Shih and Poupin 2020). Many studies have focused on the adult morphology of fiddler crabs (e.g., Crane 1975; Shih et al. 2016a), whereas the comparatively fewer reports on the larval morphology cover only 23 species within 9 genera (Table 1). Among these species, 19 are in the Gelasiminae (five in Austruca Bott, 1973, Cranuca inversa (Hoffmann, 1874), and Gelasimus hesperiae (Crane, 1975); four in Leptuca Bott, 1973; six in Minuca Bott, 1954; three in Tubuca Bott, 1973 and Xeruca formosensis (Rathbun, 1921) and two in the Ocypodinae (Afruca tangeri (Eydoux, 1835) and Uca maracoani (Latreille, 1803)), but none in the genera Paraleptuca Bott, 1973 and Petruca Shih, Ng Citation: Zhang YC, Shih HT. 2022. First zoeal stage of 15 species of fiddler crabs (Crustacea: Brachyura: Ocypodidae) from Taiwan. Zool Stud 61:71. doi:10.6620/ZS.2022.61-71. Zoological Studies 61:71 (2022) doi:10.6620/ZS.2022.61-71 1 © 2022 Academia Sinica, Taiwan & Christy, 2015 (Table 1). In addition, the characters of the first zoeal stage (zoea I) of Austruca occientalis (Naderloo, Schubart & Shih, 2016) (as Au. annulipes), G. hesperiae, Paraleptuca chlorophthalmus (H. Milne Edwards, 1837), and T. urvillei (H. Milne Edwards, 1852) were included in the key in Bento and Paula Table 1. Studies of the larval morphology of fiddler crabs. ZI–VI, larval stages of zoea; M, megalopa; *, species identified by Apel (2001) Species Original species names Stages described References Subfamily Gelasiminae Austruca albimana ZI–IV, M Kumar and Al-Aidaroos 2022 Austruca annulipes Uca annulipes ZI–V, M Feest 1969 Uca annulipes ZI Ghory and Siddiqui 2006 Austruca iranica Gelasimus annulipes* ZI–II Hashmi 1968 Austruca lactea Uca lactea M Muraoka 1976 Uca lactea ZI–V Terada 1979 ZI this study Austruca perplexa ZI this study Austruca triangularis ZI this study Austruca variegata (Heller, 1862) Uca triangularis ZI–V, M Feest 1969 Cranuca inversa Uca (Cranuca) inversa ZI Al-Aidaroos 2013 Gelasimus borealis ZI this study Gelasimus hesperiae Gelasimus marionis ZI Hashmi 1968 Gelasimus jocelynae ZI this study Gelasimus tetragonon ZI this study Gelasimus vocans ZI this study Leptuca cumulanta ZI Rosário et al. 2021 Leptuca pugilator (Bosc, 1802) Gelasimus pugilator ZI–IV, M Hyman 1920 Leptuca subcylindrica (Stimpson, 1859) Uca subcylindrica ZI–II, M Rabalais and Cameron 1983 Leptuca thayeri Uca thayeri ZI–V, M Anger et al. 1990 Uca thayeri ZI De Souza et al. 2013 Leptuca uruguayensis Uca (Celuca) uruguayensis; Uca uruguayensis ZI–VI, M Rieger 1996; Armendariz 2005 Minuca burgersi Uca (Minuca) burgersi ZI–VI, M Rieger 1998 Minuca minax (LeConte, 1855) Gelasimus minax ZI Hyman 1920 Minuca mordax (Smith, 1870) Uca (Minuca) mordax ZI–VI, M Rieger 1997 Minuca pugnax (Smith, 1870) Gelasimus pugnax ZI–II Hyman 1920 Minuca rapax Uca rapax ZI Serbino 2008a Uca rapax ZI De Souza et al. 2013 Minuca vocator Uca (Minuca) vocator Uca vocator ZI–VI, M ZI Rieger 1999 Serbino 2008c Paraleptuca crassipes ZI this study Paraleptuca splendida ZI this study Tubuca alcocki Uca urvillei ZI Ghory and Siddiqui 2006 Tubuca arcuata Uca arcuata ZI–V, M Ko and Kim 1989 ZI this study Tubuca acuta ZI this study Tubuca coarctata ZI this study Tubuca dussumieri ZI this study Tubuca paradussumieri ZI this study Tubuca urvillei Uca urvillei ZI Serbino 2008b Xeruca formosensis Uca formosensis ZI–V Hsieh and Chen 2008 ZI this study Subfamily Ocypodinae Afruca tangeri Uca tangeri ZI–V, M Rodriguez and Jones 1993 Uca tangeri ZI–V Spivak and Cuesta 2009 Uca maracoani Uca (Uca) maracoani ZI, M Negreiros-Fransozo et al. 2009 ZI De Souza et al. 2013 page 2 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan (2018), but there was no drawing and description. In Taiwan, 15 species of fiddler crabs have been reported, including the endemic X. formosensis (Shih et al. 2015 2016b; Ng et al. 2017). However, the larval morphology of only three species, namely Austruca lactea (De Haan, 1835), T. arcuata (De Haan, 1835), and X. formosensis have been described (Terada 1979; Ko and Kim 1989; Hsieh and Chen 2008). Our study describes the morphology of zoea I of the 15 species from Taiwan, with a key based on more reliable characters. The important characters among species and genera are also discussed, according to the current systematics and phylogeny of fiddler crabs (Shih et al. 2016a). MATERIALS AND METHODS Ovigerous females of the 15 fiddler crab species from Taiwan were collected from Hsinchu City (Yangang R.), Taichung (Dajia R.), Changhua (Siansi), Tainan (Bajhang R.), and Pingtung (Baoli R. and Wanlitong) in Taiwan main island, as well as its adjacent islands, Penghu, Kinmen, and Dongsha (Table 2). The specimens of ovigerous females and released larvae were deposited into the Zoological Collections of the Department of Life Science, National Chung Hsing University, Taichung, Taiwan (NCHUZOOL). Ovigerous females were measured for carapace width (cw) (Table 2) and identified by Shih et al. (2015) and, if necessary, by analysis of the cytochrome oxidase subunit I (COI; unpublished). However, because the COI marker cannot distinguish G. borealis (Crane, 1975) and G. vocans (Linnaeus, 1758) (Shih et al. 2010), these species were identified by their ITS-1 sequences (Chu et al. 2015; HT Shih unpublished). Each ovigerous female was kept in an opaque container (bottom dimensions of 20 × 12 or 50 × 31 cm) with 30‰ seawater (ratio of natural to artificial seawater = 1:1) changed once every 2 days. The water was 2 cm high, and the bottom of the container was covered with sediment from the specimens' habitat, with a portion of the sediment above the water surface. After the larval release, the zoeae were attracted by a flashlight and collected by a plastic dropper. Some zoeae were preserved in 70% ethanol directly. The remaining zoeae were first preserved in 4% buffered formalin, which was changed once every 1 h for 3 h, then preserved in 70% Table 2. The ovigerous females used in this study Species Catalogue no. (NCHUZOOL) Locality in Taiwan cw (mm) Date of collection Austruca lactea 16768 Changhua: Siansi 11.9 12 Jul. 2018 16769 Changhua: Siansi 11.8 12 Jul. 2018 Austruca perplexa 16770 Pingtung: Wanlitong, Kenting 9.9 13 Mar. 2021 Austruca triangularis 16771 Pingtung: Baoli River estuary 13.8 16 Oct. 2020 16772 Pingtung: Baoli River estuary 11.4 16 Oct. 2020 Gelasimus borealis 16773 Taichung: Dajia River estuary 23.1 9 Sep. 2018 16774 Taichung: Dajia River estuary 22.0 9 Sep. 2018 Gelasimus jocelynae 16775 Penghu: Chihsi, Siyu 16.4 31 Jul. 2020 16776 Penghu: Chihsi, Siyu 18.1 31 Jul. 2020 16777 Penghu: Chihsi, Siyu 17.2 31 Jul. 2020 Gelasimus tetragonon 16778 Dongsha Island 32.6 17 Jun. 2019 Gelasimus vocans 16779 Penghu: Chihsi, Siyu 23.9 31 Jul. 2020 16780 Penghu: Chihsi, Siyu 21.3 31 Jul. 2020 16781 Penghu: Chihsi, Siyu 23.9 31 Jul. 2020 Paraleptuca crassipes 16782 Dongsha Island 18.2 17 Jun. 2019 Paraleptuca splendida 16783 Penghu: Cingluo 13.5 3 Aug. 2020 Tubuca acuta 16784 Kinmen: Cihti 15.9 18 Aug. 2020 Tubuca arcuata 16785 Tainan: Bajhang River estuary 24.9 17 Apr. 2020 Tubuca coarctata 16786 Pingtung: Baoli River estuary 19.2 8 Nov. 2018 Tubuca dussumieri 16787 Pingtung: Baoli River estuary 21.9 8 Nov. 2018 Tubuca paradussumieri 16788 Kinmen: Cihti 18.8 20 Aug. 2020 Xeruca formosensis 16789 Changhua: Siansi 15.0 12 Aug. 2018 16790 Hsinchu County: Yangang River estuary 26.4 18 Sep. 2020 page 3 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan ethanol for final fixation. For each species, 1–3 ovigerous females were used (Table 2), and 20 zoeae were selected from each female. Each zoea was put in glycerin and dissected under a stereoscope using tiny needles. To enhance observation, the sample was either dyed with eosin or immersed in lactic acid (Rice 1981; Schoeman and Cockcroft 1996) for imaging under a phase-contrast microscope. Multiple images were stacked using Helicon Focus 5.0 stacking software into a focus-stacking image for illustration, and the morphological character states were described. The characters were measured for 20 zoeae using AxioVision Rel. 4.8 software. We found that the characters examined were stable within a species. The terminology of larval description followed Bookhout and Costlow (1974), Pohle and Telford (1981), Clark et al. (1988), Anger et al. (2015), Clark and Cuesta (2015), Landeira et al. (2019) and Colavite et al. (2021) and included the carapace, antennule, antenna, maxillule, maxilla, first maxilliped, second maxilliped, pleon, and telson. Based on Pohle (1991), the measurements provided (in millimeters) are of the carapace length (cl), rostro-dorsal length (rdl), dorsal spine length (dsl), and rostral spine length (rsl) (Fig. 1). RESULTS Description of the first zoeal stage Austruca Bott, 1973 Austruca lactea (De Haan, 1835) (Fig. 2, Table 3) Material examined: zoea I (from ♀ 11.9 mm, NCHUZOOL 16768, Siansi, Changhua, coll. Y.-C. Zhang et al., 14 Aug. 2018); zoea I (from ♀ 11.8 mm, NCHUZOOL 16769, Siansi, Changhua, coll. Y.-C. Zhang et al., 14 Aug. 2018). Size: cl. 0.35 ± 0.008 mm, rdl. 0.58 ± 0.016 mm, dsl. 0.11 ± 0.008 mm, rsl. 0.14 ± 0.008 mm. Carapace (Fig. 2A): Lateral spines lacking, dorsal spine curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Antennule (Fig. 2B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 2C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod and endopod absent. Maxillule (Fig. 2D): Epipod seta absent; coxal Fig. 1. The measurements of the first zoeal stage used in this study. page 4 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 2E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 2F): Basis with 2+2+3+2 Fig. 2. Austruca lactea, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 5 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 2G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 2H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 2H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Austruca perplexa (H. Milne Edwards, 1852) (Fig. 3, Table 3) Material examined: zoea I (from ♀ 9.9 mm, NCHUZOOL 16770, Wanlitong, Pingtung, coll. Y.-C. Zhang et al., 13 Mar. 2021). Size: cl. 0.46 ± 0.014 mm, rdl. 0.88 ± 0.024 mm, dsl. 0.20 ± 0.008 mm, rsl. 0.23 ± 0.008 mm. Carapace (Fig. 3A): Lateral spines lacking, dorsal spine slightly curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Antennule (Fig. 3B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 3C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 1 terminal simple seta, seta not reaching tip of protopod. Endopod absent. Maxillule (Fig. 3D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 3E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 3F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 3G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 3H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 3H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Austruca triangularis (A. Milne-Edwards, 1873) (Fig. 4, Table 3) Material examined: zoea I (from ♀ 13.8 mm, NCHUZOOL 16771, Baoli River estuary, Pingtung, coll. Y.-C. Zhang et al., 18 Oct. 2020); zoea I (from ♀ 11.4 mm, NCHUZOOL 16772, Baoli River estuary, Pingtung, coll. Y.-C. Zhang et al., 20 Oct. 2020). Size: cl. 0.42 ± 0.011 mm, rdl. 0.67 ± 0.029 mm, dsl. 0.13 ± 0.007 mm, rsl. 0.16 ± 0.013 mm. Carapace (Fig. 4A): Lateral spines lacking, dorsal spine curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Antennule (Fig. 4B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 4C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 2 terminal simple setae, setae not reaching tip of protopod. Endopod absent. Maxillule (Fig. 4D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 4E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 4F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 4G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 4H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a page 6 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 4H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Gelasimus Latreille, 1817 Gelasimus borealis (Crane, 1975) (Fig. 5, Table 3) Material examined: zoea I (from ♀ 23.1 mm, NCHUZOOL 16773, Dajia River estuary, Taichung, Fig. 3. Austruca perplexa, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 7 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan coll. Y.-C. Zhang et al., 11 Sep. 2018); zoea I (from ♀ 22.0 mm, NCHUZOOL 16774, Dajia River estuary, Taichung, coll. Y.-C. Zhang et al., 13 Sep. 2018). Size: cl. 0.32 ± 0.011 mm, rdl. 0.41 ± 0.015 mm, dsl. 0.04 ± 0.006 mm, rsl. 0.06 ± 0.008 mm. Carapace (Fig. 5A): Lateral spines lacking, dorsal spine curved and very reduced, rostral spine straight and very reduced, dorsal spine as long as rostral spine and pointed termination. Eyes round and sessile. Antennule (Fig. 5B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 5C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 1 terminal simple seta, seta not reaching tip of protopod. Endopod absent. Maxillule (Fig. 5D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 5E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 5F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 5G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 5H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral Table 3. The setation of different appendages in zoea stage I of 15 species of fiddler crabs from Taiwan. See figures 2–16 Structure Au. lactea Au. perplexa Au. triangularis G. borealis G. jocelynae G. tetragonon G. vocans antennule exopod 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss antenna exopod – 1 ss 2 ss 1 ss 1 ss 2 ss 1 ss maxillule coxal endite 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps basial endite 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps endopod 4 ps 4 ps 4 ps 4 ps 4 ps 4 ps 4 ps maxilla coxal endite 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps basial endite 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps endopod 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps scaphognathite 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps first maxilliped basial endite 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) endopod 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) exopod 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps second maxilliped basial endite 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) endopod 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps exopod 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps Structure P. crassipes P. splendida T. acuta T. arcuata T. coarctata T. dussumieri T. paradussumieri X. formosensis antennule exopod 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss 2 aes+2 ss antenna exopod – – 2 ss 1 ss 1 ss 2 ss 1 ss 2 ss maxillule coxal endite 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps basial endite 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps 4 pds+1 ps endopod 4 ps 4 ps 4 ps 4 ps 4 ps 4 ps 4 ps 4 ps maxilla coxal endite 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps 3 ps+3 ps basial endite 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps 5 ps+4 ps endopod 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps 1 ps+2 ps scaphognathite 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps first maxilliped basial endite 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) 2, 2, 3, 2 (ps) endopod 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) 2, 2, 1, 2, 5 (ps) exopod 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps second maxilliped basial endite 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) 1, 1, 1, 1 (ps) endopod 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps 0, 0, 5 ps exopod 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps 4 dps (aes) aesthetasc, (dps) densely plumose seta, (pds) plumodenticulate seta, (ps) plumose seta, (ss) simple seta, (–) absent. page 8 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 5H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Gelasimus jocelynae (Shih, Naruse & Ng, 2010) (Fig. 6, Table 3) Material examined: zoea I (from ♀ 16.4 mm, NCHUZOOL 16775, Chihsi, Siyu, Penghu, coll. Y.-C. Zhang et al., 1 Aug. 2020); zoea I (from ♀ 18.1 mm, Fig. 4. Austruca triangularis, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 9 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan exopod seta absent. Maxilla (Fig. 9E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 9F): Basis with 2+2+3, 2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 9G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 9H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 9H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Paraleptuca splendida (Stimpson, 1858) (Fig. 10, Table 3) Material examined: zoea I (from ♀ 13.5 mm, NCHUZOOL 16783, Cingluo, Penghu, coll. Y.-C. Zhang et al., 4 Aug. 2020). Size: cl. 0.30 ± 0.011 mm, rdl. 0.37 ± 0.015 mm, dsl. 0.04 ± 0.000 mm, rsl. 0.04 ± 0.004 mm. Carapace (Fig. 10A): Lateral spines lacking, dorsal spine curved and very reduced, rostral spine straight, dorsal spine as long as rostral spine and pointed termination. Eyes round and sessile. Antennule (Fig. 10B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 10C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod and endopod absent. Maxillule (Fig. 10D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 10E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 10F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 10G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 10H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 10H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Tubuca Bott, 1973 Tubuca acuta (Stimpson, 1858) (Fig. 11, Table 3) Material examined: zoea I (from ♀ 15.9 mm, NCHUZOOL 16784, Cihti, Kinmen, coll. Y.-C. Zhang et al., 21 Aug. 2020). Size: cl. 0.31 ± 0.010 mm, rdl. 0.49 ± 0.009 mm, dsl. 0.08 ± 0.002 mm, rsl. 0.11 ± 0.006 mm. Carapace (Fig. 11A): Lateral spines lacking, dorsal spine curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Antennule (Fig. 11B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 11C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 2 terminal simple setae, setae not reaching tip of protopod. Endopod absent. Maxillule (Fig. 11D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 11E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 11F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 11G): Basis with 1+1+1+1 page 16 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 11H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 11H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Fig. 10. Paraleptuca splendida, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 17 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan Tubuca arcuata (De Haan, 1835) (Fig. 12, Table 3) Material examined: zoea I (from ♀ 24.9 mm, NCHUZOOL 16785, Bajhang River estuary, Tainan, coll. Y.-C. Zhang et al., 9 May. 2020). Size: cl. 0.34 ± 0.010 mm, rdl. 0.53 ± 0.019 mm, dsl. 0.08 ± 0.004 mm, rsl. 0.11 ± 0.006 mm. Carapace (Fig. 12A): Lateral spines lacking, dorsal spine curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Fig. 11. Tubuca acuta, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 18 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan Antennule (Fig. 12B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 12C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 1 terminal simple seta, setae not reaching tip of protopod. Endopod absent. Maxillule (Fig. 12D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; Fig. 12. Tubuca arcuata, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 19 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan exopod seta absent. Maxilla (Fig. 12E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 12F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 12G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 12H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 12H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Tubuca coarctata (H. Milne Edwards, 1852) (Fig. 13, Table 3) Material examined: zoea I (from ♀ 19.2 mm, NCHUZOOL 16786, Baoli River estuary, Pingtung, coll. Y.-C. Zhang et al., 25 Nov. 2018). Size: cl. 0.36 ± 0.017 mm, rdl. 0.54 ± 0.022 mm, dsl. 0.07 ± 0.007 mm, rsl. 0.11 ± 0.008 mm. Carapace (Fig. 13A): Lateral spines lacking, dorsal spine curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Antennule (Fig. 13B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 13C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 1 terminal simple seta, seta not reaching tip of protopod. Endopod absent. Maxillule (Fig. 13D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 13E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 13F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 13G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 13H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 13H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Tubuca dussumieri (H. Milne Edwards, 1852) (Fig. 14, Table 3) Material examined: zoea I (from ♀ 21.9 mm, NCHUZOOL 16787, Baoli River estuary, Pingtung, coll. Y.-C. Zhang et al., 25 Nov. 2018). Size: 0.41 ± 0.012 mm, rdl. 0.61 ± 0.014 mm, dsl. 0.08 ± 0.004 mm, rsl. 0.12 ± 0.007 mm. Carapace (Fig. 14A): Lateral spines lacking, dorsal spine curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Antennule (Fig. 14B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 14C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 2 terminal simple setae, setae not reaching tip of protopod. Endopod absent. Maxillule (Fig. 14D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 14E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 14F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 14G): Basis with page 20 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 14H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 14H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Fig. 13. Tubuca coarctata, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 21 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan Tubuca paradussumieri (Bott, 1973) (Fig. 15, Table 3) Material examined: zoea I (from ♀ 18.8 mm, NCHUZOOL 16788, Cihhu, Kinmen, coll. Y.-C. Zhang et al., 29 Aug. 2020). Size: cl. 0.34 ± 0.011 mm, rdl. 0.54 ± 0.011 mm, dsl. 0.08 ± 0.003 mm, rsl. 0.12 ± 0.006 mm. Carapace (Fig. 15A): Lateral spines lacking, dorsal spine curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Fig. 14. Tubuca dussumieri, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 22 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan Antennule (Fig. 15B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 15C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 1 terminal simple seta, seta not reaching tip of protopod. Endopod absent. Maxillule (Fig. 15D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; Fig. 15. Tubuca paradussumieri, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 23 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan exopod seta absent. Maxilla (Fig. 15E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 15F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 15G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 15H): With 5 somites, second article with a pair of relatively acute dorsolateral spines pointing anterodorsally; third article with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 15H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. Xeruca Shih, 2015 Xeruca formosensis (Rathbun, 1921) (Fig. 16, Table 3) Material examined: zoea I (from ♀ 15.0 mm, NCHUZOOL 16789, Siansi, Changhua, coll. Y.-C. Zhang et al., 12 Aug. 2018); zoea I (from ♀ 26.4 mm, NCHUZOOL 16790, Yangang River estuary, Hsinchu, coll. Y.-C. Zhang et al., 18 Sep. 2020). Size: 0.35 ± 0.011 mm, rdl. 0.52 ± 0.016 mm, dsl. 0.08 ± 0.004 mm, rsl. 0.10 ± 0.004 mm. Carapace (Fig. 16A): Lateral spines lacking, dorsal spine curved, relatively short, rostral spine straight, dorsal spine and rostral spine with pointed termination. Eyes round and sessile. Antennule (Fig. 16B): Uniramous, endopod absent. Exopod smooth, unarticled, with 2 aesthetascs and 2 simple setae terminally. Antenna (Fig. 16C): Protopod basal region smooth, distal end acuminate, bearing 2 rows of spines. Exopod short, with 2 terminal simple setae, setae exceeding tip of protopod. Endopod absent. Maxillule (Fig. 16D): Epipod seta absent; coxal endite with 4 plumodenticulate setae and 1 plumose seta; basial endite with 4 plumodenticulate setae and 1 plumose seta; endopod 2-articled, proximal article without setae, 4 sparsely plumose in distal article; exopod seta absent. Maxilla (Fig. 16E): Coxal endite bilobed with 3+3 plumose setae; basial endite bilobed with 5+4 plumose setae; endopod bilobed with 1+2 terminal sparsely plumose; scaphognathite with 4 densely plumose setae and a long acuminate posterior process with microtrichias. First maxilliped (Fig. 16F): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-articled with 2, 2, 1, 2, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Second maxilliped (Fig. 16G): Basis with 1+1+1+1 sparsely plumose setae; endopod 3-articled with 0, 0, 5 plumose setae; exopod 2-articled with 4 terminal long plumose setae. Pleon (Fig. 16H): With 5 pleonites, second pleonite with a pair of relatively acute dorsolateral spines pointing anterodorsally; third pleonite with a pair of relatively obtuse dorsolateral spines pointing posterodorsally; fourth pleonite wider than other pleonites. Pleopods absent. Telson (Fig. 16H): Telson bifurcated, inner margin with 6 (3+3) serrate spines. A key to zoeal stage I of the 15 species of fiddler crabs from Taiwan (* The cw of parental females are shown in Table 2) 1. Carapace with dorsal and rostral spines very reduced .................. ................................................................................. 2 (Gelasimus) - Carapace with dorsal and rostral spines well-developed ........... 3 2. Antennal exopod with 1 terminal simple seta ............................... ............................................. G. borealis, G. jocelynae, G. vocans - Antennal exopod with 2 terminal simple setae ...... G. tetragonon 3. Antennal only with protopod, without exopod ........................... 4 - Antenna with protopod and exopod ........................................... 5 4. Carapace with dorsal spine longer (dsl/rdl > 0.18) ....................... .............................................................................. Austruca lactea - Carapace with dorsal spine shorter (dsl/rdl < 0.17) ...................... ....................................... Paraleptuca (P. crassipes, P. splendida) 5. Antennal exopod with 1 terminal simple seta ............................ 6 - Antennal exopod with 2 terminal simple setae .......................... 7 6. Carapace with dorsal spine longer (dsl/rdl > 0.18), size larger (cl. > 0.4 mm)* ...................................................... Austruca perplexa - Carapace with dorsal spine shorter (dsl/rdl < 0.17), size smaller (cl. < 0.4 mm)* .............................................................................. .......................... Tubuca arcuata, T. coarctata, T. paradussumieri 7. Antenna with terminal simple setae longer than protopod ............ ........................................................................ Xeruca formosensis - Antenna with terminal simple setae shorter than protopod ........ 8 8. Carapace with dorsal spine longer (dsl/rdl > 0.18) ....................... ..................................................................... Austruca triangularis - Carapace with dorsal spine shorter (dsl/rdl < 0.17) ................... 9 9. Size larger (cl. > 0.4 mm)* ............................. Tubuca dussumieri - Size smaller (cl. < 0.4 mm)* ................................... Tubuca acuta DISCUSSION In our study the zoeal stage I of 15 species belonging to five genera of fiddler crabs from Taiwan page 24 of 29Zoological Studies 61:71 (2022) © 2022 Academia Sinica, Taiwan territory was described. The main characters of dorsal and rostral spines of the carapace, exopod of antenna, setal length of antenna and size ratios could be used to distinguish the five genera and most species from Taiwan. Species of Gelasimus have very reduced dorsal and rostral spines of carapace which can be distinguished from others genera. The lengths of dorsal and rostral spines in Austruca are longer than those in Paraleptuca, and the antennal exopod is absent in two species of Paraleptuca (see “Key”). The larval morphology is similar in Tubuca and Xeruca, but the length of terminal simple setae on antenna is exclusively Fig. 16. Xeruca formosensis, zoea I. A, carapace; B, antennule; C, antenna; D, maxillule; E, maxilla; F, first maxilliped; G, second maxilliped; H, pleon and telson. page 25 of 29Zoological Studies 61:71 (2022)