The Oregon Coastal Subprovince, a new biogeographic subprovince for primary freshwater fishes in Oregon

The Pacific Northwest has a relatively low diversity of primary freshwater fishes with most of the endemism and diversity in the Columbia River and Klamath River. However, the Oregon Coastal Subprovince defined as the coastal rivers from Miami River in the north to Sixes River in the south, has a relatively diverse primary freshwater fish fauna, and, potentially unrecognized endemism. The species diversity and endemism of these systems is not clear because their taxa are allopatric members of more wide ranging taxa with some recognized as distinct species while others are not. The presence of primary freshwater fishes in the Oregon Coastal Subprovince has been explained as either due to their origin in the coastal river systems or dispersal to coastal rivers from the Willamette River. The goals of this study were: 1) to describe fishes in the genera Catostomus and Ptychocheilus in the Oregon Coastal Subprovince using morphological data and mitochondrial cytochrome b sequences; 2) to investigate the relationships of fishes in the Oregon Coastal Subprovince to nearby provinces; and 3) to address competing distribution theories. In this study, I re-described C. tsiltcoosensis, C. macrocheilus, C. rimiculus, P. umpquae and P. oregonensis and recognized C. sp A (Coquille River) and C. sp. B (Rogue River). Catostomus tsiltcoosensis and C. sp. A tend to have higher counts of infraorbital pores and fewer dorsal fin rays than C. macrocheilus. Catostomus tsiltcoosensis had six fixed base pair differences from C. macrocheilus. Catostomus sp. A had 14 fixed base pair differences in cytochrome b from C. macrocheilus and C. tsiltcoosensis and had a narrower body width at base of the pectoral fin than C. tsiltcoosensis. In the cytochrome b phylogeny, C. macrocheilus (Columbia) was sister to C. tsiltcoosensis (Siuslaw River, Umpqua River and Coos River) and C. sp. A (Coquille River) was sister to C. macrocheilus and C. tsiltcoosensis plus C. columbianus and C. tahoensis. The Rogue River C. sp B was recognized as a separate species from C. rimiculus because it had higher counts of vertebrae anterior to the dorsal fin and had nine fixed base pair differences from C. rimiculus. Although Catostomus sp. B was previously placed in C. rimiculus, phylogenetic analysis showed C. rimiculus was more closely related to other catostomids in the Klamath Basin than to C. sp. B. This was likely caused by hybridization among four different species of suckers in the Klamath system. Ptychocheilus oregonensis tended to have fewer scales around the caudal peduncle, fewer scales above the lateral line, fewer transverse scales, deeper body depth at the origin of the dorsal fin, and shallower caudal peduncle than P. umpquae. Ptychocheilus umpquae had 15 fixed base pair differences from P. oregonensis. Based on phylogenetic analysis, P. oregonensis (Columbia - Willamette River) was sister to the P. umpquae (Siuslaw and Umpqua) and P. grandis (Sacramento) was sister to both. If C. tsiltcoosensis and C sp. A are considered separate species, the Oregon Coastal Sub-Province has 62.5% endemism. This suggests that it is another important area of endemism in the Pacific Northwest. Based on the suckers and pikeminnow phylogenies, two common nodes (Siuslaw- Umpqua vs. Willamette-Columbia and Sacramento vs. Willamette-Columbia-Siuslaw- Umpqua) were found in sucker and pikeminnow phylogenies. If pikeminnow and suckers shared a common history, two vicariant events (Sacramento from Willamette – Columbia – Umpqua - Siuslaw and Willamette - Columbia from Siuslaw - Umpqua) were responsible for such pattern. On the other hand, if the two groups had separate histories, the phylogeny of the suckers also suggested two additional vicariant events (Coquille from Willamette – Columbia – Umpqua - Siuslaw and Willamette - Columbia from Siuslaw - Umpqua). Similar to the sucker phylogeny, the phylogeny of the pike minnow suggested a vicariance pattern. The estimated divergence times among taxa were supported by geological evidence

Genetic diversity of blue-spotted mudskipper (Boleophthalmus boddarti) populations in Gulf of Thailand

Environmental changes and the reduction of habitat can threaten populations of mudskippers, which have a distinct life cycle compared with other fish species. Genetic diversity and structure are crucial information for the conservation plan of this species. The genetic diversity was investigated on the blue-spotted mudskipper, Boleophtalmus boddarti, in the Gulf of Thailand. In total, 178 fish were collected from six locations in the Gulf. Based on the 320 bp sequences of the mitochondrial control region of the 55 haplotypes observed, the most common was in 88 fish from all locations. Total haplotype diversity and nucleotide diversity values (mean ± SD) were h = 0.751 ± 0.036 and π = 0.0069 ± 0.0001, respectively. There was a significant (p = 0.011) difference in π between inner and outer Gulf samples. Although the analysis of molecular variance suggested the absence of genetic structuring within the Gulf, two clear groups of haplotypes were evident in the medianjoining network of haplotypes. Group I included haplotypes from all locations and group II was identified by haplotypes with an additional adenine at the 16078th position based on the mitochondrial genome sequence of B. boddarti (Accession no. KF87427). The results of the nonmetric multidimensional scaling and Bayesian assignment test were indicative of genetic divergence between the inner and outer Gulf, suggesting that despite the high potential for dispersal of planktonic larvae, water currents may act as a physical barrier to gene flow in the study area. The observed signals of population divergence between B. boddarti from the inner and outer Gulf of Thailand may account for the presence of this oceanographical barrier. Mismatch distributions, based on the observed number of differences among haplotype pairs, produced a unimodal distribution with a peak close to the y-axis, suggesting recent demographic expansion. The results could augment future study with baseline information on the maternal genetic variation and structure of the bluespotted mudskipper, B. boddarti, populations in the Gulf of Thailand

Monitoring of reproductive health in the striped catfish Pangasianodon hypophthalmus (Sauvage, 1878) from the Saen Saep Canal, Thailand

Khlong Saen Saep is one of the most important and large canal systems in Bangkok, Thailand. However, the emergence of heavily polluted water has occasionally been reported due to the domestic sewage and industrial effluents discharged into the system. This situation may affect the reproductive status of aquatic lives residing in this canal. To evaluate the reproductive status of the canal inhabitant, the striped catfish Pangasianodon hypophthalmus (Sauvage, 1878)—a common dweller of the Saen Saep Canal—was collected from two selected stations, the Bumpen Nua Temple and the Kamalun Islam Mosque. The fish gonads were then anatomically and histologically examined. The results indicated that neither parasites nor ovary with external abnormality were found. Nevertheless, several histological alterations were detected, including vacuolar degeneration of previtellogenic oocytes, accumulation of melanomacrophage centers (MMCs), and atretic oocytes. Moreover, severe histopathological changes, such as the eosinophilic cytoplasm of spermatogonia, MMCs, blood congestion, and syncytium of spermatozoa, were observed in the fish testis. Our study suggested that the environmental stress and pollutions previously reported from the Saen Saep Canal possibly underpin the gonadal impairments of P. hypophthalmus examined and may have adverse impact on the reproductive health of others living in this canal syste

Food partitioning of two co-occurring Terapontid fishes, Terapon jarbua and Pelates quadrilineatus, in coastal areas of Trang Province, Southern Thailand

This study clearly demonstrates that Terapon jarbua and Pelates quadrilineatus showed obvious food partitioning by their dietary ontogenetic changes. The larvae of both species fed mainly on the calanoid copepods. Juveniles of T. jarbua shifted to feed mainly on harpacticoid copepods, crabs and fish scales. Juveniles of P. quadrilineatus shifted to fed mainly on harpacticoid copepods and Lucifer spp. Adult fish shifted to fed on larger prey size. AdultT. jarbua fed mainly on fish and fish scales while adult of P. quadrilineatus fed mainly on large benthic animals, amphipods, bivalves, hermit crabs and polychaetes. The study on morphology and feeding structure development indicated that, the development of mouth, jaw, teeth, gill raker and intestinal length were important ontogeneticchange in the diet of fish. The ontogenetic change in the diet was the important strategies to reduce competition between these two coexisting species in coastal area of Trang Province

The microanatomy of the central nervous system and brain of the Indo-Pacific seahorse, Hippocampus barbouri, during development

The central nervous system (CNS) of Teleostei is a complex system of self-governance and its morphology is reflected in the physiological and reproductive behaviors. The Indo-Pacific seahorse, Hippocampus barbouri Jordan & Richardson, 1908, is a new candidate species for aquaculture in Thailand. In this study, we investigated the brain morphology of H. barbouri across various developmental windows. Light microscopic observations of adult brains revealed a large optic tectum in the mesencephalon, whereas the cerebral hemispheres and the cerebellum are of medium size. The detailed brain structures were generally similar to those of other teleosts; however, only five distinct layers were present in the optic tectum, including the stratum marginale, stratum opticum, stratum album central, stratum griseum central, and stratum periventriculae, versus six layers observed in other fish. One day after birth (1 DAB) the brain was a packed structure without any clear sub-structures. The number of capillaries in the optic tectum began to increase at 6 DAB, and at 14 DAB several features, including small blood vessels in the optic tectum and Purkinje cells, became noticeable. By 35 DAB, the optic tectum became highly vascularized and included five layers. Additionally, large Purkinje cells were developed in the cerebellum. Based on the brain development pattern, we speculate that the predatory ability of this fish starts to develop from 6 to 14 days after birth

Structure and health status of the sand crab, Emerita taiwanesis Hsueh, 2015 from Sangchan Beach, Thailand: The histopathological approach

Although the impacts of environmental problems on aquatic organisms have been broadly reported in Thailand, the literature has not covered the sand crab, Emerita taiwanesis Hsueh, 2015. In this study, we focused on the structure and health status of E. taiwanesis, an economically important crab species, living close to human activity areas in Sangchan Beach, Rayong Province, Thailand. A total of 60 individuals were collected from the conservation and restoration of coastal resource project in Ban Rue Leg Kao Yod-based participatory during December 2016 – January 2017. We identified histopathological changes in the gill structure, but not in other vital organs, including ganglion, stomach, intestine, hepatopancreas and muscular bundles. The histological alterations in the gill include hematocyte infiltration, pyknotic nuclei and degeneration of pillar cells in the gill (50% prevalence), suggesting that the gill is a sensitive organ to environmental changes. Our observation provided a better understanding of E. taiwanesis morphology and its overall healthy state on Sangchan Beach. Additionally, we suggest that the sand crab would be a suitable sentinel species for monitoring the environment of coastal areas in Thailand.

Observation of gut content and morpho-histology of the digestive system in Pisodonophis boro (Hamilton, 1822) from Pranburi River Estuary, Thailand

The snake eel, Pisodonophis boro, is an important ecological and subsistence component of the Pranburi River estuary. Here, we used gut content analysis and morpho-histology to examine optimum foraging theory in P. boro in the Pranburi River estuary. Gut content analysis revealed that four species of crabs, including Metaplax elegans, Perisesarma bidens, Sarmatium germaini, and Uca perplexa, but S. germaini were consistently present at high levels in the gut throughout a year-long study. The index of relative importance showed that the most important prey was S. germaini. The overall anatomical morphology of the digestive system of P. boro was elongated, and the stomach appeared as Y-shaped. The histology of the P. boro esophagus, stomach, and intestine were examined followed the standard histological techniques. Goblet cells through the digestive tract of P. boro were also seen among the epitheliums and reacted positively to periodic acid schiff and alcian blue staining methods. Overall, we suggest that P. boro is a specialist feeder on crabs rather than an opportunistic feeder

Effects of salinity level on the activity of chloride cell and mucus secreting cell in the gill of the female Shortfin molly, Poecilia mexicana Steindachner, 1863

Ovoviviparous poeciliid fishes have been relatively well studied in the unique reproductive strategy, but their osmoregulatory system largely remains unknown. In this study, we conducted a short-term (7 days) lab experiment to investigate the effect of different salinity levels from 0 (freshwater) to 50 ppt (mesosaline) on the number of chloride cells and mucus secreting cells of female Poecilia mexicana. Chloride cells were found at high density along the epithelial lamellae, whereas mucus secreting cells were also concentrated in the gill raker epithelium. More interestingly, the average density of chloride cells and the mucus secreting cell were significantly increased at high salinity levels (P < 0.05). While further validation by immunohistochemistry is warranted, integrative data from our study suggested that the potential function of the osmoregulatory mechanism/strategy was supported by chloride and mucus secreting cells of female P. mexicana gill

Distribución y cambios del sistema sbGnRH en machos de Rastrelliger brachysoma durante el período reproductivo

Rastrelliger brachysoma&nbsp;is a mariculture candidate species, but reproduction in captive fish has been problematic. This report examines the difference in the HPG axis, the neuroendocrine system and the development of reproductive tissues between captive vs. wild male&nbsp;R. brachysoma. The gonadosomatic index (GSI) of sexually mature male wild&nbsp;R. brachysoma&nbsp;was 1.12±0.34 and 1.94±0.26 during the non-breeding and breeding seasons, respectively. Captive&nbsp;R. brachysoma&nbsp;had a GSI of 1.88±0.17. All wild&nbsp;R. brachysoma&nbsp;were in the late spermatogenic stage irrespective of seasons. Immunostaining results showed that sbGnRH-immunoreactive neurons were distributed in three areas of the brain, namely the nucleus periventricularis, nucleus preopticus and nucleus lateralis tuberis. Follicle stimulating hormone and luteinizing hormone immunoreactivities were also observed in the pituitary gland. The levels of brain sbGnRH and GtH mRNA were not significantly different between the non-breeding and breeding seasons, but captive fish displayed (times or percent difference) lower mRNA levels than wild fish. These results suggest that these hormones control the testicular development in&nbsp;R. brachysoma&nbsp;and that the impaired reproduction in captivity may be due to their relative lower expression levels of follicle stimulating hormone and luteinizing hormone genes.Rastrelliger brachysoma&nbsp;es una especie candidata para la piscicultura marina, pero la reproducción de individuos cautivos de esta especie ha sido problemática. Este estudio examina las diferencias en el eje hipotálamo-hipófisis-gónada (eje HPG), junto con el desarrollo de tejidos reproductivos, entre machos cautivos y salvajes de&nbsp;R. brachysoma. El índice gonadosomático (IGS) de machos salvajes de&nbsp;R. brachysoma&nbsp;sexualmente maduros fue de 1.12±0.34 y 1.94±0.26 durante la estación no-reproductiva y reproductiva, respectivamente. Los&nbsp;R. brachysoma&nbsp;cautivos mostraron un IGS de 1.88±0.17. Todos los&nbsp;R. brachysoma&nbsp;salvajes se encontraban en un estado de espermatogénesis tardío, independientemente de la estación. Los resultados de inmunotinción mostraron que las neuronas sbGnRH-inmunoreactivas se distribuían en tres áreas del cerebro, nucleus periventricularis, nucleus preopticus y nucleus lateralis tuberis. Se detectó inmunoreactividad para Fsh y Lh también en la hipófisis. Los niveles de mRNA de sbgnrh y gths en cerebro no fueron significativamente diferentes entre las estaciones de reproducción y no-reproducción, aunque se observaron niveles de mRNA menores (diferencia en nivel o porcentaje) en individuos cautivos que en salvajes. Estos resultados sugieren que las hormonas analizadas controlan el desarrollo testicular en&nbsp;R. brachysoma&nbsp;y que la inhibición de la reproducción en cautividad podría ser debida a unos menores niveles de expresión relativa de los genes de Fsh y Lh

Spermatozoon of the wild scalloped perchlet, Ambassis nalua (Hamilton, 1822): Ultrastructure and morphometric analysis

The description of sperm morphology is fundamental in the reproductive biology of fishes, but this information is limited in the family Ambassidae. Our report hence focused on the ultrastructure and morphometric analysis of spermatozoa in a pelagic fish Ambassis nalua. All fish (n = 75) were obtained during January and March 2017 from the Estuarine Pranburi River, Thailand. The standard length of fish used in this study was 3.4 ± 0.12 cm (mean ± standard deviation). All specimens were considered mature based on the abundance of spermatozoa in the testis. The testicular organs were collected and observed using standard histology and transmission electron microscopy (TEM). Ultrastructural observation associated with morphometric analysis showed that spermatozoa are structurally long cells of approximately 51.17 ± 4.54 µm total length, composed of a head, a midpiece and a tail. The head had no acrosome, and the granular structure of condensed chromatin was observed within the ovoid nucleus. The midpiece consisted of a short cylindrical region with the length of 1.29 ± 0.87 µm in diameter, having the centriolar complex organization and eight mitochondria (approx. 0.32 ± 0.02 µm each). The uniflagellar tail was clearly identified with a classical 9+2 arrangements of microtubules. Based on these characteristics, the spermatozoon of wild scalloped perchlet are considered as uniflagellate anacrosomal aquqsperm. The morphological features, including the number of mitochondria, may be used for further cryopreservation and in the evolutionary biology of this species