Urogenital Pore Research Articles

The morphological characteristics of banded needlefish Strongylura leiura(Bleeker, 1850) dwelling in the coastal water of Can Gio district, Ho Chi Minh city

The banded needlefish (Strongylura leiura) dwells in the coastal waters of Can Gio district, Ho Chi Minh city, with the local name “blue-bone fish”. Study results on the morphological characteristics of 70 individuals showed that the total length and weight of fish varied from 410 to 1,060 mm (average 741.71 mm), 90-2,600 gr (average 618.73 gr), respectively. There were 17-24 dorsal fin rays, 22-29 anal fin rays, 12-19 pectoral fin rays, and small and low pelvic fins with 9-13 rays. The lateral scales with 192-427 small scales indicated the growth of this fish in the coastal waters of Can Gio, with the growth value b ranging from 3.431-3.501 and R2values ranging from 0.875-0.926. The research on the external structure of the banded needlefish can help distinguish male and female individuals of this species based on the external morphology of the sex organs. There was a pink urogenital papilla on male. In female, there was a single round pink urogenital pore without a genital papilla. When the gonad of matured female came to the stage III to stage IV, this genital pore was widened and pink.

Spatial and Temporal Changes in Testis Morphology and Sperm Ultrastructure of the Sportfish Sauger (Sander canadensis)

AbstractThe objective of this study was to assess testicular morphology and spermatozoal structure spatially within the reproductive tract and temporally among seasons in the sauger (Sander canadensis). The testis exists as two separate lobes joined at the urogenital pore and were characterised as unrestricted lobular with seminiferous tubules terminating at the ventral periphery and coalescing dorsally on the main sperm duct. Differences were observed between the pre‐breeding season (November) and breeding season (March), with every stage of spermatogenesis occurring in spermatocysts in pre‐breeding season in contrast to only spermatozoa being present in the tubules and main duct during the breeding season. Longitudinal folds in the main duct epithelium increased in number with increasing proximity to the urogenital pore, greatly increasing epithelial height regardless of season. Sauger spermatozoa consisted of an ovoid head, a midpiece containing 2 – 4 mitochondria incorporated into the head and a single flagellum containing an asymmetrical lateral ribbon. Motile spermatozoa were found throughout the testis during the breeding season. A decrease in sperm concentration was quantified moving proximally, suggesting a hydration effect by the main duct epithelium during the breeding season. These observations fill an important knowledge gap regarding reproductive biology of this impactful recreational fish species.

A New Species ofSpatuloricariaSchultz, 1944 (Siluriformes: Loricariidae), from the Orinoco River Basin, Colombia

A new species of Spatuloricaria is described from the Orinoco River basin, Colombia. The new species can be distinguished from its congeners by the following characters: a broad, dark brown stripe on the first pre-dorsal plate, which occupies the entire plate, reaching the preopercle, and sometimes reaching the second pre-dorsal plate; the possession of a small group of plates posterior to the urogenital pore; the abdominal surface with scattered, very small plates leaving naked areas; the possession of five transverse dark brown bands on the dorsal region; and four to five premaxillary teeth. The new species is the first valid species of Spatuloricaria distributed in the Orinoco River basin. Ecological notes of the species and comments regarding the taxonomy and phylogenetic relationships of the genus are offered.

Understanding morphological variability in a taxonomic context in Chilean diplomystids (Teleostei: Siluriformes), including the description of a new species

Following study of the external morphology and its unmatched variability throughout ontogeny and a re-examination of selected morphological characters based on many specimens of diplomystids from Central and South Chile, we revised and emended previous specific diagnoses and consider Diplomystes chilensis, D. nahuelbutaensis, D. camposensis, and Olivaichthys viedmensis (Baker River) to be valid species. Another group, previously identified as Diplomystes sp., D. spec., D. aff. chilensis, and D. cf. chilensis inhabiting rivers between Rapel and Itata Basins is given a new specific name (Diplomystes incognitus) and is diagnosed. An identification key to the Chilean species, including the new species, is presented. All specific diagnoses are based on external morphological characters, such as aspects of the skin, neuromast lines, and main lateral line, and position of the anus and urogenital pore, as well as certain osteological characters to facilitate the identification of these species that previously was based on many internal characters. Diplomystids below 150 mm standard length (SL) share a similar external morphology and body proportions that make identification difficult; however, specimens over 150 mm SL can be diagnosed by the position of the urogenital pore and anus, and a combination of external and internal morphological characters. According to current knowledge, diplomystid species have an allopatric distribution with each species apparently endemic to particular basins in continental Chile and one species (O. viedmensis) known only from one river in the Chilean Patagonia, but distributed extensively in southern Argentina.

A new catfish species of the Trichomycterus hasemani group (Siluriformes: Trichomycteridae), from the Branco river basin, northern Brazil

Trichomycterus wapixana is described from the Branco river basin, Roraima State, northern Brazil. It belongs to the T. hasemani group, composed of T. hasemani, T. johnsoni and T. anhanga and defined by the presence of a single wide cranial fontanel delimited by the frontal and supraoccipital, absence of the pores i1 and i3, absence of branchiostegal rays on the posterior ceratohyal and the by the presence of a large and distally expanded process on the palatine. It differs from the other species of that assemblage by having a unique combination of character states, including number of vertebrae, relative position of anal fin, relative position of pelvic and dorsal fin, presence of pelvic fin and pelvic girdle, number of dorsal and ventral procurrent rays in the caudal fin, anal-fin rays, pectoral-fin rays, branchiostegal rays, pleural ribs, morphology of palatine, presence of parasphenoid and relative position of urogenital pore.

Collection of spawning-condition eels of Ariosoma meeki in the Kuroshio Current in the East China Sea

When and where marine eels spawn is poorly known even though species such as those of the family Congridae, Muraenidae and Ophichthidae can be caught in continental shelf habitats. The congrid genus Ariosoma includes small continental shelf eel species whose life histories are not yet known. Mature male and female eels of Ariosoma meeki were observed and captured on 17 August 2009 at the surface at night in the western side of the Kuroshio Current in the East China Sea close to new moon, while they were swimming slowly at the surface and exhibiting apparent reproduction-related behaviour. One male and one sex-unidentified eel (seemingly a male based on body shape) were observed to be chasing one larger female with their heads located near her urogenital pore area. The gonads of the female (540 mm) and the male (410 mm) that were caught by a long-handled dip net were in reproductive condition, because some eggs or seminal fluid were released during handling of the two specimens and high gonad-somatic index (GSI) values of 53 in the female and 20 in the male were recorded. This is one of the few cases in which fully ripe reproductive-condition marine eels have been observed or collected and it provides rare information about the spawning location and timing of this eel species.

Evaluation of Stocking All Female Largemouth Bass (<i>Micropterus salmoides</i>) in Alabama (USA) Ponds

Excessive largemouth bass ( Micropterus salmoides ) recruitment in small impoundments leads to density-dependent growth depression, causing populations to have length distributions skewed towards smaller fish. To address this issue, we conducted three trials that evaluated stocking all female largemouth bass (F-LMB) in two small Alabama ponds (0.5 and 2.0 ha) where the drainage basin was isolated. Age-1 fish were individually identified for sex using a micro pipette inserted in the urogenital pore, tagged, and stocked at 38-40 F-LMB/ha into ponds that contained pre-established sunfish ( Lepomis spp.) populations. Female largemouth bass were collected with electrofishing, angling, and rotenone over a 2.5- to 5-year period among the three trials. Sex was correctly identified for 179 of the 180 F-LMB stocked. One male was detected in the first trial which resulted in successful largemouth bass reproduction and this trial was terminated after two years. Growth was rapid the first 2 years after stocking as 3-year-old fish reached an average of 429 to 459 mm and 1.37 to 1.66 kg in all 3 trials. However, 2 years after stocking, growth was nil in the second trial even though relative weights of F-LMB were generally greater than 100. In this second trial, removal of about 30% of the F-LMB inhabiting the pond and stocking small Nile tilapia Oreochromis niloticus (25 - 75 mm) resulted in average weights increasing from 1.30 to 2.34 kg in 1 year. Growth of F-LMB continued in the third trail, and average size approached 500 mm and 2.2 kg three years after stocking. Annual survival rates of F-LMB were high and ranged from 0.78 to 0.93 among the 3 trials. Stocking F-LMB offers an attractive alternative in ponds to create a low density largemouth bass population that displays fast growth and high survival when catch-and-release fishing is primarily practiced.

Retrograde positive contrast urethrocystography of the fish urogenital system.

The radiological differences between the urinary tract of Dicentrarchus labrax, Sparus aurata, Tinca tinca, and Cyprinus carpio are shown. In fresh water teleosts the urinary bladder is sigmoid and a short urethra leads to the urinary pore. Genital and anal pores are present. In Sparus aurata the urinary bladder has a globoid shape. In Dicentrarchus labrax the urinary bladder is smaller and elongate. In both marine teleosts a single urogenital pore is visible. Positive contrast was used to survey the urogenital system and evaluate shape and size of the bladder, urethra, ureter, and gonadal ducts. Results demonstrate the morphological variability of the urinary bladder and the craniodorsal entry of the ureters into the bladder. It is envisaged that this work will provide baseline information for further imaging studies for investigating the urogenital morphology and can be applied to identify disorders in fishes. Furthermore, the main interest of this study is that it demonstrates the morphological variability of the lower urinary system that exists between different species of fishes.

A portable electro‐immobilization and laparoscopy system for sex determination and gonadal biopsy in largemouth bass Micropterus salmoides

A portable electro-immobilization and laparoscopy system is described that is suitable for sex determination, gonadal biopsy and immediate release of largemouth bass Micropterus salmoides. Continuous direct current at a power density of 52·2 µW cm⁻¹ for 2 min was sufficient to immobilize fish for surgery, but induced a mild, transient hypokalaemia and hyperglycaemia. Insertion of a 4·8 mm laparoscopic instrument set through the urogenital pore provided access to the gonads for examination and biopsy with mild tissue trauma.

Pelvic-fin brooding in a new species of riverine ricefish (Atherinomorpha: Beloniformes: Adrianichthyidae) from Tana Toraja, Central Sulawesi, Indonesia

A new species of ricefi sh is described from a hill stream in Tana Toraja, Sulawesi. Oryzias eversi, new species, is distinguished from all other adrianichthyids in Sulawesi by having a low number of fi n rays in anal (17-18 (19)) and dorsal (10-12) fi ns, only 33-36 scales in lateral midline, ½14 transverse scale rows at dorsal fi n origin, 30-32 (33) vertebrae, small eyes (28.2-35.5% of head length), a conspicuous blackish male courtship colouration, and brooding behaviour similar to lacustrine ricefi shes. Female Oryzias eversi carry the eggs until the embryos hatch, and show a conspicuous abdominal concavity and extended fi ns, accommodating and holding the clutch of eggs. The eggs are connected to the female for the whole time of development by attaching fi laments that protrude from the female's urogenital pore. A mitochondrial haplotype phylogeny suggests that the new species is closely related to another pelvic the lake-dwelling O. sarasinorum from Lake Lindu in Central Sulawesi. However, the haplotype group of O. eversi and O. sarasinorum is nested within a clade of egg-depositing Oryzias from central, southwest, and southeast Sulawesi, whereas another brooder, Adrianichthys oophorus from Lake Poso, forms a distinct, second lineage of Sulawesi's ricefi shes. Accordingly, the brooding strategy has probably evolved more than once and may be realised in river habitats, which represents a new evolutionary trajectory in the radiation of ricefi shes in Sulawesi. The present discovery adds another new ricefi sh species to Sulawesi's still only partially known ichthyofauna, and highlights the island's role as hotspot of adrianichthyid diversity.

Sex Determination of Yellow Perch by External Morphology

AbstractWe developed a method of using external morphological characteristics to determine the sex of yellow perch Perca flavescens. The characteristics used were (1) the shape of the urogenital opening, (2) the shape of the anterior edge of the urogenital opening when thumb pressure was applied to the abdomen just anterior to the anus, and (3) the presence or absence of swelling around the anus. In females, the urogenital opening was crescent or half‐moon shaped, its anterior edge remained linear when pressure was applied to the abdomen, and a ring‐shaped area of swelling was present around the anus. In males, the urogenital pore was circular, its anterior end distended to a V or U shape (pointed anteriorly) when the abdomen was pressed, and the area around the anus was not generally swollen. The accuracy of using this method was 97.4% for fish 190–280 mm total length, 93.1% for fish 111–150 mm, and 82.7% for fish 80–110 mm.

Reproductive role of attaching filaments on the egg envelope in Xenopoecilus sarasinorum (Adrianichthidae, teleostei)

Eggs of Xenopoecilus sarasinorum possess two distinct types of filaments on the surface of the egg envelope (chorion), long, attaching filaments restricted to the vegetal pole and weak, nonattaching filaments around the animal pole (micropyle). Both types are formed during oogenesis. After mature eggs were spawned through the urogenital pore, they were fertilized and hung in an abdominal concavity of the female. Oviposition never took place in the presence of embryos in the concavity because of the retardation of oogenesis. The loosely tangled tips of the attaching filaments that are retained within the ovarian cavity plug the urogenital pore by forming a hard complex with the epithelial cells. Into this plug structure that fuses with the inner wall of the urogenital pore, capillaries are provided. Within 5 days after the initiation of hatching, this plug degenerates and is released from the urogenital pore. Thus, in female X. sarasinorum, the reproductive cycle seems to be regulated by the physiological function ofthe plug structure formed by the attaching filaments in response to the presence of developing embryos.

Oviposition Cycle in the Oviparous Fish Xenopoecilus sarasinorum

To clarify the reproduction of the oviparous teleost Xenopoecilus sarasinorum, changes in oocyte composition and oviposition cycle were investigated. After release, a batch of spawned eggs hung from the urogenital pore by attaching filaments (36.3+/-0.8 in number, n=31; about 4.3-7.8 mm in length, 5-8 microm in diameter) on the chorion (egg envelope) in the vegetal pole region. Females accommodated a cluster of fertilized eggs in a belly concavity until the embryos hatched. Hatching of embryos took place from 18-19 days after oviposition (25 degrees C). Between 0-2 days following hatching, the attaching filaments disappeared from the urogenital pore. Between 3 and 4 days following hatching, most of the females spawned again. The growth of oocytes proceeded slowly throughout the period when the egg cluster was carried in the belly, and no ovulation occurred during this period. If the current brood was accidentally lost, the day of the next oviposition was sooner. This might imply that carrying embryos in the belly affects endocrine activity, as in viviparous reproduction.

Spawning Behavior and Genetic Parentage in the Pirate Perch (Aphredoderus sayanus), a Fish with an Enigmatic Reproductive Morphology

We describe for the first time reproductive behaviors in the Pirate Perch (Aphredoderus sayanus), a secretive nocturnal fish whose urogenital opening is positioned far anteriorally, under its throat. Some naturalists had speculated that this peculiar morphological condition might serve to promote egg transfer to the fish's branchial chamber for gill-brooding; others hypothesized that Pirate Perch spawn in the substrate of streams but offered no adaptive rationale for the odd placement of the fish's urogenital pore. Here we solve the conundrum through a combination of intensive field investigations, underwater filming, and molecular parentage analyses. We show that Pirate Perch spawn in underwater root masses, the first documentation of such nesting behavior in any species of North American fish. Female Pirate Perch thrust their heads and release their eggs into sheltered canals of these masses. Males congregate at these sites and likewise enter the narrow canals headfirst, to release sperm. Thus, the forward-shifted urogenital pore may facilitate spawning under this special nesting circumstance. We found no evidence of extended parental care. Fish formed their own canals or used burrows made by aquatic macro-invertebrates and salamanders. Genetic analyses based on three polymorphic microsatellite loci demonstrate that a total of at least five to 11 sires and dams were the parents of embryos within each of three assayed root-mass nests (of a total of 23 nests found). Males defended the oviposition sites by body-plugging canal entrances after spawning. This and more direct aggressive behaviors by males probably relate to selection pressures imposed by intense competition for fertilization success under these group-spawning conditions.

Structure and cytology of the testes of Labeo victorianus (Pisces: Cyprinidae)

Testes macromorphology and histomorphology together with sperm cytology are described for a potamodrometic cyprinid fish, Labeo victorianus, from Lake Victoria. Testes were found to be paired and elongate, suspended by a mesorchium on either side of the swim bladder. A sperm duct ran along the medial surface of each testis before fusing caudally to form the common sperm duct that terminated at the urogenital pore. Main sperm ducts were lined by simple columnar epithelium supported by a wall with elastic connective tissue and a few smooth muscle cells. The tunica albuginea divided the testes into lobules, which contained spermatogenetic cell types. The lobules, released spermatozoa into an anastomosing tubule network that emptied directly into the main sperm duct. Valve like structures were present along the length of the sperm duct and are proposed to regulate milt flow. Three types of somatic cells were observed at the onset of gonadal recrudescence; plasma and intralobular somatic cells were within the lobules, while Leydig cells were close to the blood vessels in the interstitium. Maturing testes were characterized by the dominance of spermatocytes and spermatids, both contained in cysts. Spermatozoa, arising from the spermatids, filled the lobular lumen in mature testes after spermatocyst rupture. In post spawned testes, Type A spermatogonia dominated. Testicular regression was not characterized by spermatozoa phagocytosis, rather via apoptosis.

Ionic factors affecting motility, respiration and fertilization rate of the sperm of the bivalvePecten maximus (L.)

Fertilization of the scallopPecten maximus occurs after gametes were naturally released in sea water by the bivalve which has undergone stimulation. The motility of the spermatozoa requires their dilution in sea water (1/40). Dilution triggers an immediate increase of oxygen consumption by sperm, reflecting an activation of a cyanide-sensitive respiration of a cellular origin. When scallops were stimulated by thermal shocks or by serotonin injection, sperm sampled at the urogenital pore output duct shows a respiration-motility activation after sea water dilution which is not seen in sperm scarified from the gonad. Dilution of kidney-sampled sperm into acidic (pH 5) or Na+-free artificial sea water reversibly inhibits both respiration and motility. In all cases fertilization rate of sperm is correlated to the increase of respiratory rate and motility measured after dilution in different media. Whether the scallop was stimulated or not, the pH of haemolymph and pericardic fluids were one pH unit below the value of sea water, the pH of the gonad and of the kidney tissues being more acidic (6.5 in average). Our results suggest that the acidic pH of the genital tract maintains the spermatozoa in a quiescent state and that capacitation occurs when male gametes move from the gonad to the kidney from where it is naturally released.

Reproduction, spawning behaviour and captive breeding of the common wolffish Anarhichas lupus L.

The reproductive biology and spawning behaviour of the common wolffish ( Anarhichas lupus) was studied in the laboratory, and various facilities were tested in order to make common wolffish spawn in captivity. Fish caught on the south and west coast of Norway spawned between the middle of October and the middle of February, with a peak around the turn of the year. There is no sexual dimorphism in common wolffish prior to maturation. Towards spawning the ripening female adopts a pronounced pot-bellied shape. The testis is small, on average only 0.11% of the total body weight of males, and there is little difference in the size of running-ripe and non-running testes. At most 1.5 ml of milt was stripped from a running male, and males were found to be running during most of the spawning season. Running males have a papilla on their urogenital pore which may serve as a copulatory organ. Morphological as well as behavioural evidence strongly suggests that the eggs of the common wolffish are fertilized internally, and that copulation takes place 8–15 h before spawning. No successful, natural spawning took place in the various facilities tested, ranging from small tanks (4 m 2) with single pairs to big basins (up to 1500 m 2) with many wolffish present. The common wolffish seems to have a complex reproductive behaviour which probably makes it difficult to obtain natural spawning on a regular basis in captivity. Procedures are suggested for artificial fertilization of common wolffish eggs.

Evidence for Direct Development in Meiopriapulus fijiensis (Priapulida)

Evidence for Direct Development in Meiopriapulus fijiensis (Priapulida)

Comparative urogenital morphology and external sex determination in muskellunge, Esox masquinongy Mitchill

Primary and secondary sexual characteristics in northern pike, Esox lucius Linneaus, and muskellunge, Esox masquinongy Mitchill, differ markedly. Differences in the internal urogenital anatomy include the structure of the genital ducts and the angle they form with the ventral surface. Externally, the genital and urinary ducts open directly to the environment in northern pike, whereas in muskellunge they open into a muscular papilla and then through a urogenital pore. Differences in sexual dimorphism between the two closely related esocids constitute a structural basis to explain the known differences in spawning behaviour and reproductive success. Differences in secondary sexual characteristics explain why the methods developed by Demchenko or Casselman to externally sex pike are inapplicable to muskellunge. To develop and test two external sexing techniques for muskellunge, specimens were collected from two regions in Canada from 1980 to 1987. Examination of reproductive products obtained from stripping provided an accurate indicator of sex and sexual maturity, but demonstrated serious limitations. A simple method to sex muskellunge by examination of the external urogenital morphology is described for juveniles and adults. Dissection of fish revealed that with the urogenital examination technique we sexed juveniles with a success rate of 92–98%, and adults with 100% accuracy.

A Technique for Sexing Channel Catfish

Abstract A simple, accurate technique has been devised to sex externally channel catfish, Ictalurus punctatus, regardless of body size or state of gonadal maturation. Male catfish have a single urogenital opening; females have two openings partitioned by a septum—an anterior genital pore, and a posterior urinary pore. In male fish, a single probe can be inserted into the urinary bladder through the urogenital pore. Female fish are differentiated from males by the insertion of two probes, one into the urinary bladder through the urinary pore and the second into the oviduct through the genital pore.