Gobioid Fishes Research Articles

Revision and phylogenetic placement of one of the earliest freshwater gobies from the Lower Oligocene of Central Europe

ABSTRACT Gobioid fishes (Teleostei) are renowned for their remarkable species diversity in marine and freshwater environments, making their evolutionary history a fascinating study subject. Among their oldest known fossils is the small-sized freshwater goby ‘Gobius’ gracilis from the Lower Oligocene of Central Europe, which has not undergone a detailed investigation since its first description. Here, we present a comprehensive re-analysis of ‘G.’ gracilis using type specimens and new material from museum collections. We show that this species possesses a unique combination of traits, leading to the establishment of a new genus, †Laubeichthys gen. nov. Phylogenetic analyses using Bayesian Inference (BI) recover †Laubeichthys gen. nov. as a stem member of the extinct family †Pirskeniidae and suggest a sister relationship between the family Thalasseleotrididae (ocean sleepers) and †Laubeichthys gen. nov. + †Pirskeniidae. Maximum parsimony analyses do not contradict such a relationship, but the trees are less resolved. Today, the Thalasseleotrididae includes four marine species that are restricted to the Southwest Pacific. In contrast, †Pirskeniidae and †Laubeichthys gen. nov. inhabited freshwater environments in Central Europe. Our findings provide new insights into the evolutionary history and historical biogeography of gobioid fishes and highlight the dynamic nature of their past diversity and distribution.

First report of Mugilogobius rambaiae (Smith, 1945) (Family: Gobiidae) from India along with geographical expansion of two goby fishes from Kerala

The discovery of three previously undocumented gobioid fish species in Kerala's mangrove ecosystems, namely Eugnathogobius mindora, Mugilogobius mertoni, and Mugilogobius rambaiae, marks a significant advancement in our understanding of the region's aquatic biodiversity. These findings highlight the importance of targeted sampling initiatives and underscore the need for continued exploration and conservation efforts to protect Kerala's fragile mangrove habitats. The adaptability of gobioid fish species from the genera Eugnathogobius and Mugilogobius to fluctuating salinity levels makes them particularly well-suited to thrive in the dynamic environments of shallow intertidal and subtidal estuaries, as well as mangrove ecosystems. Their presence is crucial in maintaining the ecological balance of coastal habitats in the Indo-Pacific region, including Kerala. The discovery of these gobioid fish species not only enhances the ecological richness of Kerala but also offers a significant understanding of the intricate relationships between these fish and their habitats. By enhancing the understanding of the range of gobioid fish species found in the mangroves of Kerala, more effective conservation and management approaches to safeguard these vital coastal ecosystems can be developed. Continuing study and conservation efforts are crucial for the preservation of Kerala’s mangrove ecosystems and the species diversity. By comprehending the enigmas of gobioid fish diversity and other fundamental facets of mangrove ecosystems, substantial advancements can be made in guaranteeing enduring sustainability for future generations.

Records of three gobioid fishes (Actinopterygii: Gobiiformes: Gobiidae) from the Gujarat coast, India

We report for the first time three gobioid fishes: Amblygobius semicinctus (Bennett, 1833), Istigobius diadema (Steindachner, 1876), and Yongeichthys nebulosus (Forskål, 1775) from the Gujarat coast of India. We present short descriptions with species diagnostic characters, habitat and present distributions.

Site-specific attachment of Anodonta anatina (Bivalvia: Unionidae) glochidia on two new fish hosts translocated in Lake Trasimeno (Italy)

To complete their life cycle, freshwater mussels of the order Unionida depend on fishes as hosts for their obligatory parasitic larval phase, the glochidium. Here we report the first documentation of gobioid fishes as hosts of glochidia of unionid mussels in the wild in Italy and in southern Europe (outside of the Danube drainage area). We also examined the pattern of the attached glochidia. A recent review reported 326 fish species as suitable hosts for unionids, but only eight (2.5%) of these were Gobioidei. Host identification and the documentation of their benefits or threats for the interaction of the mussels with their hosts is important for conservation of freshwater mussels. But the co-existence of mussels with non-native fish species is only poorly understood, including the compatibility of these two groups. Knipowitschia panizzae and Pomatoschistus canestrinii, two translocated sand gobies, were sampled in 2022 at the east shore of Lake Trasimeno (Italy). Two species of anodontine mussels were present at this locality, the native Anodonta anatina and the translocated Sinanodonta woodiana. Genetic data revealed that both sand gobies hosted glochidia only of A. anatina but not of S. woodiana, possibly because of seasonal bias. About 50% of the specimens of both fish species were infested. The paired fins were the most prominent targets. The examined individuals of both sand gobies carried only few glochidia (max. 5). Nevertheless, the two species showed a divergent pattern of glochidia attachment.

Gonad morphology of Rhyacichthys aspro (Valenciennes, 1837), and the diagnostic reproductive morphology of gobioid fishes.

Rhyacichthys aspro is a “basal” taxon in the Suborder Gobioidei of the teleost order Gobiiformes. We provide detailed descriptions of the reproductive morphology of adult males and females to assess the diagnostic reproductive morphological characters of this speciose clade of bony fishes. Female R. aspro are asynchronous spawners: they are able to spawn more than once in a breeding season. Oocytes are inferred to have short attachment filaments. A conspicuous feature of the external anatomy of the reproductive system (RSy) of female R. aspro is an ornate fimbriate pad upon which the urogenital papilla rests. The male reproductive system is characterized by an intralobar collection system in both the testicular and secretory lobes, termed the “sperm‐collecting canal” and “milt‐collecting canal,” respectively. These may provide additional storage for sperm and milt. The spermatogenic lobe, or testis, is that portion of the male gobioid RSy comprising seminiferous lobules and separate from other RSy components. The secretory lobe is that portion of the male gobioid reproductive system that consists of secretory lobules and is separated from other components of the male RSy. The secretory lobe has also been called, in English, the sperm‐duct gland, accessory gonadal structure, or seminal vesicle, and is endorsed as a synapomorphy of gobioid fishes.

Diversity of gobioid fishes in the late middle Miocene of northern Moldova, Eastern Paratethys \u2013 part I: an extinct clade of Lesueurigobius look-alikes

Studies of otoliths suggest that Gobioidei, which are among the most species-rich groups of modern-day vertebrates, were prominent elements of late middle Miocene (early Sarmatian sensu lato) fish faunas in Europe and Western Asia. However, few complete skeletons have come to light. Here, we report an assemblage of six marine gobiid species, based on skeletons preserved with otoliths in situ, from the lower Volhynian (lower Sarmatian s.l.) of Karpov Yar, Naslavcea, northern Moldova (Eastern Paratethys). Previously only one of these species had been reported from the Central Paratethys, based on its otoliths alone. Five new species representing four new genera are described: †Katyagobius prikryli gen. et sp. nov., Pseudolesueurigobius manfredi gen. et sp. nov., †Sarmatigobius compactus gen. et sp. nov., †Yarigobius decoratus gen. et sp. nov., and †Y. naslavcensis gen. et sp. nov. All six species share the following set of characters, suggesting that they represent a monophyletic clade: 27–29 vertebrae (of which 10 are abdominal); spines of first dorsal fin distally filamentous; second dorsal fin with spine and 14–16 soft rays; anal fin with spine and 13–15 soft rays; caudal fin longish-to-lanceolate; otoliths (sagittae) with rounded, trapezoid-to-squarish shape. Their skeletal features suggest that they are closely related to Lesueurigobius Whitley, 1950, but the otoliths preserved in situ do not support such a classification. The new fossils most likely represent a stem lineage of the European Aphia lineage, and indicate that the diversity of gobiid lineages 12 million years ago differed clearly from that observed today.

Designation of a lectotype for the Canestrini’s Goby, Gobius canestrinii Ninni, 1883 (Teleostei, Gobiiformes, Gobiidae, Gobionellinae)

A recent study based on molecular biological data revealed that Gobius canestrinii (Ninni, 1883), a gobioid fish endemic to the Adriatic basin, has to be split in three lineages. The original description was based on populations from two distant localities in Italy and in Croatia respectively, the first representing one of these lineages, the second most likely belonging to another lineage. To fix the name of the species, we hereby designated a lectotype for Canestrini’s Goby.

Bendy to the bone: Links between vertebral morphology and waterfall climbing in amphidromous gobioid fishes.

Locomotor force production imposes strong demands on organismal form. Thus, the evolution of novel locomotor modes is often associated with morphological adaptations that help to meet those demands. In the goby lineage of fishes, most species are marine and use their fused pelvic fins to facilitate station holding in wave-swept environments. However, several groups of gobies have evolved an amphidromous lifecycle, in which larvae develop in the ocean but juveniles migrate to freshwater for their adult phase. In many of these species, the pelvic fins have been co-opted to aid in climbing waterfalls during upstream migrations to adult habitats. During horizontal swimming, forces are produced by axial musculature pulling on the vertebral column. However, during vertical climbing, gravity also exerts forces along the length of the vertebral column. In this study, we searched for novel aspects of vertebral column form that might be associated with the distinctive locomotor strategies of climbing gobies. We predicted that stiffness would vary along the length of the vertebral column due to competing demands for stability of the suction disk anteriorly and flexibility for axial thrust production posteriorly. We also predicted that derived, climbing goby species would require stiffer backbones to aid in vertical thrust production compared to non-climbing species. To test these predictions, we used microcomputed tomography scans to compare vertebral anatomy (centrum length, centrum width, and intervertebral space) along the vertebral column for five gobioid species that differ in climbing ability. Our results support our second prediction, that gobies are more flexible in the posterior portion of the body. However, the main variation in vertebral column form associated with climbing ability was the presence of larger intervertebral spaces in Sicyopterus stimpsoni, a species that uses a distinctive inching behavior to climb. These results build on past kinematic studies of goby climbing performance and lend insights into how the underlying vertebral structure of these fishes may enable their novel locomotion.

Morphological and Histological Characteristics of Testis of the Goby Glossogobius sparsipapillus Living from Coastal Estuaries from Bac Lieu to Ca Mau

This study was conducted in the coastal estuaries in Bac Lieu and Ca Mau provinces in order to provide data on morphological and histological characteristics of as well as the spermatocyte development at every stage of the development of testis of goby Glossogobius sparsipapillus. The analysis results of 226 fish individuals, collected monthly from April 2019 to September 2019 by using the bottom nets, showed that the testis of this fish was double strands. In stage I, testis was small, thin and transparent; and the weight and size of testis increased from that stage onward. The colour of the testis became ivory white with the smooth and puffed surface. Spermatogonia were found through the cross-section of the testis in stage I, and then they were divided into primary spermatocytes and secondary spermatocytes, which were interlaced in stage II. In stage III, spermatids appeared in testicular lobes and developed into sperm in stage IV. This fish species is a multiple spawner during the breeding season, because there are several developmental stages of spermatocytes in their histology. This result is the basis for further research on artificial reproduction of this fish.
 Keywords: Bac Lieu, Ca Mau, Glossogobius sparsipapillus, reproductive form, testis.Keywords: Essential oil plats, life form, plants, Sop Cop nature reserve.
 References
 [1] P. Akihito, K. Meguro, Glossogobius sparsipapillus, a new species of goby from Viet Nam. Japanese Journal of Ichthyology 23 (1976) 9-11. [2] D.D. Tran, K. Shibukawa, T.P. Nguyen, P.H. Ha, X.L. Tran, V.H. Mai & K. Utsugi, Fishes of Mekong Delta, Vietnam. Can Tho University Publisher, Can Tho, 2013 (In Vietnamese).[3] H.V. Nguyen, Freshwater fish of Viet Nam, Vol III, Agriculture Publishing House, Ha Noi, 2005 (In Vietnamese).[4] T.N. Nguyen, Fauna of Vietnam – Gobioidei, Science and Technics House Publishing, Ha Noi, 2000 (in Vietnamese).[5] H.M.T. To, T.M.X. Pham, V.H. Mai, D.D. Tran. Species composition of goby (Eleotridae and Gobiidae) and some characteristics of tank goby (G. giuris) distributed in Can Tho. Proceeding of Aqua Youth, Ho Chi Minh City (2013) 575-582 (in Vietnamese).[6] X.M.T. Pham, D.D. Tran, Some characteristics on reproductive biology of Tank goby (Glossogobus giuris) distributed in Can Tho city, Can Tho University Journal of Science 27 (2013) 161-168 (in Vietnamese).[7] Q.M. Dinh, T.V. Ly. Preliminary study result of length – weight of tank goby, Glossogobius giuris, distributing in Soc Trang, Can Tho University Journal of Science 2 (2014) 220-225. (in Vietnamese).[8] G.V. Nikolsky, Ecology of fishes, Academic Press, London, United Kingdom, 1963.[9] H.M. Carleton, R.A.B. Drury, E. Wallington, Carleton's Histological Technique, Oxford University Press, London, United Kingdom, 1980.[10] Q.M. Dinh, J.G. Qin, S. Dittmann, D.D. Tran, Reproductive biology of the burrow dwelling goby Parapocryptes serperaster. Ichthyological Research 63 (2016) 324–32. https://doi.org/ 10.1007/s10228-015-0502-7 [11] L. Bui, M.H. Nguyen, Q.K. Nguyen, Q.L. Le, D.Y. Mai, Basis of physiology of fish. Agriculture Publishing House, Ha Noi, 1985 (in Vietnamese).[12] P.J. Miller, The topology of gobioid fishes, G.W. Potts, R.J. Wootton (eds), The topology of gobioid fishes, Academic Press, Orlando, London, United Kingdom, 1984, 119-53[13] Q.M. Dinh, T.T.G. Nguyen, T.K.T. Nguyen, Reproductive biology of the mudskipper Boleophthalmus boddarti in Soc Trang. Tap chi Sinh hoc 37 (2015) 362-9. https://doi.org/10. 15625/0866-7160/v37n3.6720 [14] Q.M. Dinh, T.T.M. Le, Reproductive traits of the duckbill sleeper Butis butis (Hamilton, 1822). Zoological Science 34 (2017) 452-8. https://doi. org/10.2108/zs170013.[15] N.H.T. Le, Q.M. Dinh, Reproductive pattern, morphological and histological characteristics of gonads of the goby Eleotris melanosoma from the Coastline in Soc Trang, VNU Journal of Science: Natural Sciences and Technology, 33 (2017) 9-86. http://doi.org/10.25073/2588-1140/ vnunst.4490 (in Vietnamese).[16] Q.M. Dinh, T.T.N. Tran, Reproductive biological traits of the goby Stigmatogobius pleurostigma (Bleeker, 1849) from the Mekong Delta, Vietnam. Indian Journal of Fisheries 65 (2018) 20-5. http://doi.org/10.21077/ijf.2018.65.1.681 88-04. [17] Q.M. Dinh, L.T. Tran, N.C. Ngo, T.B. Pham, T.T.K. Nguyen, Reproductive biology of the unique mudskipper Periophthalmodon septemradiatus living from estuary to upstream of the Hau River. Acta Zoologica(2018) 1-12. http://doi.org/10.1111/azo.12286.

Luciogobius yubai, a new species of gobioid fish (Teleostei: Gobiidae) from Japan.

A new gobioid fish Luciogobius yubai sp. nov. is described based on specimens collected from Wakayama and Shizuoka Prefectures, Japan. This species is distinguished from congeners by the following combination of characters; second dorsal-fin I, 9, anal-fin I, 10, pectoral-fin 17 or 18, vertebrate number 16+19=35, the first space between anterior two pterygiophores of second dorsal-fin placed the neural spines of vertebrae 17-18 or 17, four to seven developed dermal flaps under the eye longitudinally, posterior part of eye ridge protruded posteriorly, pectoral-fin with a long uppermost free ray, eye diameter 7.3-10.6 % of head length, pectoral-fin length 14.4-16.9 % of standard length (SL) , second dorsal-fin length 9.7-11.8 % SL, anal-fin ray length 9.1-11.1 % SL, pelvic-fin length 7.3-10.8 % SL, head and body with brownish orange coloration when alive or fresh.

Evolution of acoustic communication in European gobies (Gobius lineage) based on molecular markers

Evolution of acoustic communication in European gobies (Gobius lineage) based on molecular markers

Molecular Approach to Identify Gobioid Fishes, “Nike” and “Hundala” (Local Name), from Gorontalo Waters, Indonesia

Data of the species scientific name is required to study biodiversity and conservation of local fish species. Nike and hundala are the local names for fish found in Gorontalo whose scientific names are unknown and recognized by local people as two different species of fish. This study aims to identify the genetic and species of nike and hundala fish. Nike and hundala specimens were collected using a fish net from the estuary of Gorontalo Bay and Bone River, Gorontalo, Indonesia in April 2018. Molecular analysis of fish over sequencing methods shows that nike and hundala at Gorontalo waters are alleged as Sicyopterus longifilis.

Reproductive biology ofApocryptes bato(Gobiidae) in the Payra River, southern Bangladesh

The gobioid fish Apocryptes bato (Hamilton, 1822) is a species of mudskipper found in Bangladesh, India, and Myanmar. The reproductive biology of A. bato including sex ratio, size at sexual maturity, breeding season, fecundity, and condition factor was studied in the Payra River, southern Bangladesh during May 2016 to April 2017. A total of 1,028 specimens (303 males and 725 females) were collected. The overall sex ratio was significantly different from the expected value of 1:1 (male: female = 1:2.39, χ2 = 173.23, p < 0.05). Size at sexual maturity was estimated as 4.9 cm standard length. Monthly variations in gonadosomatic index indicate that the main breeding season is from May to December. There was a significant positive correlation of body length and body weight with fecundity. Fulton's condition factor varied in both sexes and was attributed to variations in GSI with maturity. Breeding season was significantly associated with rainfall, but not air temperature. Our findings should improve management and conservation of this fish in the Payra River and surrounding ecosystems.

Phylogenomic analysis on the exceptionally diverse fish clade Gobioidei (Actinopterygii: Gobiiformes) and data-filtering based on molecular clocklikeness

The use of genome-scale data to infer phylogenetic relationships has gained in popularity in recent years due to the progress made in target-gene capture and sequencing techniques. Data filtering, the approach of excluding data inconsistent with the model from analyses, presumably could alleviate problems caused by systematic errors in phylogenetic inference. Different data filtering criteria, such as those based on evolutionary rate and molecular clocklikeness as well as others have been proposed for selecting useful phylogenetic markers, yet few studies have tested these criteria using phylogenomic data. We developed a novel set of single-copy nuclear coding markers to capture thousands of target genes in gobioid fishes, a species-rich lineages of vertebrates, and tested the effects of data-filtering methods based on substitution rate and molecular clocklikeness while attempting to control for the compounding effects of missing data and variation in locus length. We found that molecular clocklikeness was a better predictor than overall substitution rate for phylogenetic usefulness of molecular markers in our study. In addition, when the 100 best ranked loci for our predictors were concatenated and analyzed using maximum likelihood, or combined in a coalescent-based species-tree analysis, the resulting trees showed a well-resolved topology of Gobioidei that mostly agrees with previous studies. However, trees generated from the 100 least clocklike frequently recovered conflicting, and in some cases clearly erroneous topologies with strong support, thus indicating strong systematic biases in those datasets. Collectively these results suggest that data filtering has the potential improve the performance of phylogenetic inference when using both a concatenation approach as well as methods that rely on input from individual gene trees (i.e. coalescent species-tree approaches), which may be preferred in scenarios where incomplete lineage sorting is likely to be an issue.

First report of the parasitic copepod Lernaea cyprinacea (Copepoda: Lernaeidae) on gobioid fishes (Teleostei: Gobonellidae) in southern Europe

Lernaea cyprinacea is a non host-specific parasitic copepod known to infest many freshwater fish species. Outbreaks of infestations by this ectoparasite may cause mass mortality of parasitized fishes. L. cyprinacea has been found mostly on pelagic species. Records on small benthic fish species are less common. Especially rare are infestations of Gobioidei adapted to a benthic life style, with reports restricted to Asia and, in Europe, to the Ponto-Caspian region. Although it is cosmopolitan, L. cyprinacea has rarely been found in Italy. One of the few Italian localities with documented infestations is Lake Trasimeno, a lake with an economically important fishery. Although endoparasites of commercially interesting fish species in this lake are well documented, information about ectoparasites is rare. In May 2015, specimens of two gobioids − Knipowitschia panizzae and Pomatoschistus canestrinii − infested with L. cyprinacea were sampled at the south shore of Lake Trasimeno. Both gobies are not native to the lake. This is the first documentation of gobioid fishes as hosts of L. cyprinacea in Italy and in Europe (outside of the Ponto-Caspian region). Although both gobies are not optimal hosts (small size, short life expectancy) they have the potential to carry and to transmit the parasite in freshwater habitats, e.g. by unintentional introduction with fry of other fish species.

Schindleria nigropunctata, a new species of paedomorphic gobioid fish from the Red Sea (Teleostei: Schindleriidae)

A new species of paedomorphic gobioid fish, Schindleria nigropunctata from the Red Sea, is described on the basis of two specimens. The new species is characterised by its relatively high body bearing pigment spots, largest specimen 15.6 mm standard length (SL), the body depth at pectoral-fin origin 5–6% of SL and at anal-fin origin 9% of SL, the predorsal length 53–67% of SL, preanal length 54–67% of SL, dorsal-fin rays 13, anal-fin rays 11 or 12, first dorsal-fin ray at myomere 24; first anal-fin ray below second dorsal-fin ray, myomeres 20 + 21 or 22 = 41 or 42 total; premaxillae and dentaries with small teeth; gas bladder located posteriorly at 47–49% of SL; males with a rod-like, flexible urogenital papilla lacking lobes, projections or accessory papillae, with narrow, pointed and usually posteriorly directed. A key to the species of Schindleriidae is presented.

The complete mitochondrial genome characterization of Tridentiger obscurus (Gobiiformes: Gobiidae) and phylogenetic analyses of Gobionellinae

The dusky tripletooth goby, Tridentiger obscurus, is a good model organism for the small in size and reaching maturity within a single year. Previous studies mainly focused on the annual reproductive cycle, social behavior and life history, but little information is available of the mitochondrial genome and phylogenetic evolution of this gobioid fish. In this article, we described the complete mitogenome of T. obscurus and reconstructed the phylogenetic relationship of the relative species of Gobionellinae. The genome is 16,501 bp in length including 13 protein-coding, two ribosomal RNA, 22 transfer RNA genes, as well as a putative control region and an L-strand replication origin. The overall base composition is 28.1%, 27.0%, 28.0% and 16.9% for A, T, C and G, respectively. This result is expected for better understanding the systematic evolution of the genus Tridentiger and further phylogenetic study of Gobiiformes.

Gobies (Gobioidei) of soft bottoms from Nha Trang and Van Phong bays (South China Sea, Vietnam)

Gobioid fishes collected in Nha Trang and Van Phong bays (Vietnam) represented by 44 species, including 30 species continuously associated with soft bottoms in the open parts of the bays with normal marine conditions are reviewed. A new species, Navigobius khanhoa sp. n., is described. This species differs from other species of the genus in much higher number of rays in the second dorsal fin (26), smaller size of the mouth, teeth on the jaws arranged in a single row, and other characters. Four species from the genera Acentrogobius, Eviota, Favonigobius, and Gnatholepis have not been identified to the species, and, most likely, some of them are new for science. Nine species are recorded in the fauna of Vietnam for the first time: Aulopareia unicolor, Bathygobius hongkongensis, Egglestonichthys bombylios, Glossogobius circumspectus, Oplopomops diacanthus, Oxyurichthys auchenolepis, Tomiyamichthys ex gr. russus, Tryssogobius porosus, and Valenciennea immaculata. An occurrence of Glossogobius olivaceus in the fauna of Vietnam is confirmed. Three species, G. olivaceus, Oligolepis acutipennis, and Periophthalmus kalolo, are recorded in the Cai River delta for the first time. A new synonymy is established: Eviota gurjanovae (Prokofiev, 2007) = E. prasina (Klunzinger, 1871). The current state of knowledge of Gobiidae fauna of Vietnam is discussed, and the updating of the species composition of Gobiodontini of Nha Trang Bay is presented in addition to the species list published earlier (Prokofiev, 2007).

Specific gravity and migratory patterns of amphidromous gobioid fish from Okinawa Island, Japan

Amphidromy is a diadromous life history pattern where fish spawn in freshwater, and their larvae drift downstream to the sea; the larvae develop in marine environments then migrate back in rivers to grow and reproduce. Two amphidromous types with different life history characteristics, such as egg and larval sizes, exist. To understand the ecology and early life history of amphidromous gobioid fish, six species from Okinawa Island were selected—two large egg-type species (Rhinogobius similis and Tridentiger kuroiwae) and four small egg-type species (Stiphodon percnopterygionus, Stenogobius sp., Sicyopterus lagocephalus, and Eleotris acanthopoma). The migratory pattern of four of these species was confirmed using otolith Sr:Ca and Ba:Ca ratios combined with water chemistry analysis. Although these species showed amphidromous migratory patterns, the timing of migration from estuarine to freshwater habitats was species-specific. The large egg-type, R. similis, showed three different migratory patterns: a long marine larval phase with a relatively fast migration from estuarine to freshwater habitats, a short marine larval phase with a relatively fast migration, and a gradual migration. Similar patterns of a long and fast migration or a gradual migration were seen in T. kuroiwae; however, the two small egg-type species, Sti. percnopterygionus and Stenogobius sp., showed rapid migration to freshwater after entering the river. To estimate larval ecology in the sea, ontogenetic changes in specific gravity (SG) were examined in all species. The SG was measured day and night for 1–5days until settlement in R. similis and T. kuroiwae, and until 10days after hatching in the other species. The SG of all species ranged from 1.0138 to 1.0488, and varied among ontogenetic stages and between day and night and species. Larval SG was relatively similar between R. similis and T. kuroiwae, with low SG in the early stages and high SG after yolk absorption. During the late larval stages and until settlement, T. kuroiwae showed diel changes in SG, with higher SG during the day, whereas R. similis had a relatively constant pattern. The diel changes of T. kuroiwae larvae suggest different activity during the day and at night (e.g. diel vertical migration). In the four small egg-type species, SG was high at hatching and decreased thereafter, not showing large diel changes. The results suggest that sympatric amphidromous gobioid species have various early life histories that may be influenced by several larval traits, including SG.

Systematics of the mudskipper genusOxudercesEydoux &amp; Souleyet 1848 (Teleostei: Gobiidae: Oxudercinae) with resurrection from synonymy ofO. nexipinnis(Cantor 1849)

The mudskipper (Gobiidae: Oxudercinae) genus Oxuderces Eydoux & Souleyet is re-diagnosed with five putative synapomorphies: (1) a fleshy, dorsal, interorbital trough or slit supported internally by expanded, curved medial margins of the frontal bones and lined with a thick epidermis and thin dermis (vs. no fleshy, interorbital trough, medial margins of the frontal bones expanded but not curved, and epidermis extremely thin and dermis thick); (2) highly thickened epidermis over the eye (vs. thickened dermis); (3) neural spine of the fourth vertebra broad and spatulate (vs. narrow and pointed); (4) anterior ceratohyal posterior to fourth branchiostegal ray insertion elongate and notched (vs. not elongate, or elongate and not notched); and (5) angle between the metapterygoid–symplectic–quadrate strut and the anguloarticular acute (vs. angle obtuse). The fleshy, dorsal, interorbital trough is a unique character for Oxuderces that is not observed in other oxudercine gobies or gobioid fishes. The extremely thick epidermis may help the skin remain moist when exposed to the air and facilitate cutaneous respiration. Two allopatric species are included in the genus Oxuderces: Oxuderces dentatus Eydoux & Souleyet, 1848, from the south-east coast of China, is the type species; Oxuderces nexipinnis (Cantor, 1849), from the Indo-West Pacific, is resurrected from synonymy of O. dentatus sensu Murdy (1989). Apocryptodon wirzi Koumans, 1937, a species classified in Oxuderces by Murdy (1989) is reassigned to Apocryptodon based on a posteriorly directed laminar process on the parapophyses of the fourth vertebra. Oxuderces nexipinnis uniquely has a dermal invagination of unknown function just posterior to the point of attachment of the pelvic-fin base.