Male Anal Fin Research Articles

Centromochlus meridionalis, a new catfish species from the southern Amazonian limits, Mato Grosso State, Brazil (Siluriformes: Auchenipteridae)

Centromochlus actually comprises eleven species, being the most problematic genus among the Centromochlinae, including morphologically heterogeneous taxa. The Centromochlus species have a wide distributional area on northern South America. Centromochlus meridionalis, new species, is described from headwaters of rio Teles Pires, contributor of rio Tapajós, Mato Grosso State, Brazil, and represents one of the southernmost records of a centromochlin catfish for Meridional Amazon rivers. Centromochlus meridionalis is promptly distinguished from its congeners by the small orbital diameter (relative to head length), and also by the combination of absence of first nuchal plate, anterior margin of dorsal-fin spine smooth, six branched rays in anal fin, seven pairs of ribs and 34 vertebrae. They are small sized catfishes with adults between 33 to 61 mm in standard length. The modified male anal fin is conspicuous, with the third unbranched ray enlarged, about twice the width of first unbranched ray. The new species inhabits a region strongly endangered by environmental changes due to expansion of agropecuary activities on Brazilian Amazon, which include this species in an uncertain situation regarding the conservation status of its natural population.

The Function of Anal Fin Egg-Spots in the Cichlid Fish Astatotilapia burtoni

Color and pigmentation patterns of animals are often targets of sexual selection because of their role in communication. Although conspicuous male traits are typically implicated with intersexual selection, there are examples where sex-specific displays play a role in an intrasexual context, e.g. when they serve as signals for aggression level and/or status. Here, we focus on the function of a conspicuous male ornament in the most species-rich tribe of cichlid fishes, the haplochromines. A characteristic feature of these ca. 1500 species are so-called egg-spots in form of ovoid markings on the anal fins of males, which are made up of carotenoid based pigment cells. It has long been assumed that these yellow, orange or reddish egg-spots play an important role in the courtship and spawning behavior of these maternal mouth-brooding fishes by mimicking the eggs of a conspecific female. The exact function of egg-spots remains unknown, however, and there are several hypotheses about their mode of action. To uncover the function of this cichlid-specific male ornament, we used female mate choice experiments and a male aggression test in the haplochromine species Astatotilapia burtoni. We manipulated the number and arrangement of egg-spots on the anal fins of males, or removed them entirely, and tested (1) female preference with visual contact only using egg-traps, (2) female preference with free contact using paternity testing with microsatellites and (3) male aggression. We found that females did not prefer males with many egg-spots over males with fewer egg-spots and that females tended to prefer males without egg-spots over males with egg-spots. Importantly, males without egg-spots sired clutches with the same fertilization rate as males with egg-spots. In male aggression trials, however, males with fewer egg-spots received significantly more attacks, suggesting that egg-spots are an important signal in intrasexual communication.

Altered development and reproduction in western mosquitofish (Gambusia affinis) found in the Hanxi River, southern China

The current study investigated the development and reproductive health of western mosquitofish (Gambusia affinis) in the Hanxi River, which has been heavily contaminated by municipal wastewaters from towns in Dongguan of southern China. Western mosquitofish collected from four study sites, Songmu (SM), Yangwu (YW), Hengli (HL), and Zhangcun (ZC) of the Hanxi River, as well as a reference site (LX) of the Liuxi River, were dissected and analyzed for development parameters (total length, wet body mass, liver mass, gonad index, and population composition), reproductive parameters (oocyte count and weight of females, and sperm count and viability of males), and morphology (anal fin in males and females, and hemal spines in males). With the exception of the origin site (SM), mosquitofish from the Hanxi River exhibited significantly decreasing development and reproduction levels. Significant correlations were found for the collected mosquitofish between the morphological and reproductive indexes (ratio of perpendicular distance to tip to vertical distance from the tip on the 16th hemal spine) versus the sperm count of males; ratio 16P:16D versus sperm viability of males; segments of anal fin ray 3 versus oocyte count of females; and segments of anal fin ray 3 versus average oocyte mass of females. The results demonstrated that both male and female mosquitofish in the Hanxi River were affected by the discharged wastewaters, as reflected in their morphological changes in comparison with those of mosquitofish from the reference site.

Two new Australian species of the Paraulopus nigripinnis complex (Aulopiformes: Paraulopidae)

Two new species, Paraulopus longianalis n.sp. and Paraulopus melanostomus n.sp., are described from western and southern Australian waters. Both are referable to the Paraulopus nigripinnis group of Sato and Nakabo (2002b, 2003) in having 4.5–5.5 scales above the lateral line, supraocular ridges and large adult body size, but differ from other species of the group in having two rows of cheek scales. Paraulopus longianalis is characterized by a deep anal fin in males, tiny adipose dorsal fin and supraocular ridges extending nearly to the predorsal scales, and P. melanostomus is most easily distinguished by its black buccal cavity and relatively broad, depressed head. A key to the six described species in the P. nigripinnis group is provided.

Threatened fishes of the world: Austrolebias univentripinnis Costa and Cheffe 2005 (Cyprinodontiformes: Rivulidae)

Common names: Annual fish, killifish. Conservation status: None. Identification: Urogenital papilla completely attached to anal fin in males, pelvic fins 75 to 90% fused. Largest male registered 35.6 mm SL and largest female 32.2 mm SL (Illustration by Felipe Ribas). Coloration: Lateral body of males with 11–18 vertical rows of brilliant blue-green pigmentation on a dark greenish gray background. Lateral body of females with elongated bars on a faint yellow-brown background (Costa and Cheffe 2005). Distribution: Endemic to Jaguarao River basin, Patos-Mirim Lagoon system, Rio Grande do Sul, Brazil. Abundance: Population estimates not available. Habitat and ecology: Inhabit shallow temporary pools that are formed generally between June to September, in the winter months, during the rainy season. Pools generally are small in surface area (<1,000 m) with maximum depth of 50 cm and high density of aquatic macrophytes. The pH was 6.6–6.8 and the water was whitish. Reproduction: Unknown; likely similar to congenera, which mature within two months after hatching and reproduce throughout his life (Errea and Danulat 2001). Threats: Greatest threat is caused by drainage and changes in physical structure and the hydrological cycle of wetlands due to rice cultivation in floodplains of the Jaguarao River and its small tributaries. The loss of habitat caused by urban progress in the city of Jaguarao and the cattle presence in all sampling sites of the species are also threats to populations of A. univentripinnis (Lanes and Cheffe 2006). Conservation action: None taken. Conservation recommendations: Establish some form of legal protection, as small conservation units, in areas of occurrence of the species; realization of studies regarding the biology and ecology; inhibit the illegal draining and use of wetlands for rice cultivation and urban construction; include it in lists of species of fauna threatened with extinction and recovery and monitoring of its habitat. Environ Biol Fish (2010) 87:319–320 DOI 10.1007/s10641-010-9605-1

Identification of novel genes involved in the development of the sword and gonopodium in swordtail fish

Male swordtail fish of the genus Xiphophorus develop a sword, a colourful extension of the caudal fin, that evolved by sexual selection through female choice. Swords and gonopodia, an intromittent organ developing from the male anal fin, can be prematurely induced by exogenous testosterone, offering the opportunity to examine the identity and expression profiles of genes required during various stages of fin metamorphosis. Here, we employed suppression subtractive hybridisation to identify genes specifically up-regulated during two early stages of sword and gonopodium development. We identified 128 different sequences with significant similarity to known genes and characterized the rack1, dusp1, klf2, and tmsbeta-like genes as specifically up-regulated in developing as well as regenerating fin rays of the sword and gonopodium. We show that some of these genes follow distinct expression profiles in swords and gonopodia, suggesting differences in the genetic networks underlying the development of anal and caudal fin modifications.

A systematic revision of Tatia (Siluriformes: Auchenipteridae: Centromochlinae)

The auchenipterid catfish genus Tatia is revised. Twelve species are recognized including three described as new. Tatia is diagnosed by the hyomandibula elongated anterodorsally, the anal-fin base of adult males reduced in length, and the caudal peduncle laterally compressed and deep with a middorsal keel. Tatia aulopygia occurs in the Madeira river drainage and is distinguished by the reduced cranial fontanel in adults and male modified anal fin with middle rays reduced in length. Tatia boemia, known from the upper Uruguay river drainage, is distinguished by its unique color pattern with dark chromatophores on the sides of body. Tatia brunnea from river basins in Suriname and French Guiana and the Negro river drainage, Amazon basin, is recognized by its wide head and mouth and by the male modified anal fin with sharply pointed tip. Tatia dunni, from the upper Amazon basin, is recognized by its narrow head, long postcleithral process in some specimens, and body coloration with irregular blotches or stripes. Tatia galaxias, endemic to the Orinoco river basin, is distinguished by its large eye and short snout. Tatia gyrina, distributed in the upper and central Amazon basin and in northern Suriname, has a uniquely reduced mesethmoid, slightly protruding lower jaw, second nuchal plate with slightly concave lateral borders, third nuchal plate reduced, small prevomer, low number of ribs, low number of vertebrae and sexual dimorphism regarding intumescent male genital papilla. Tatia intermedia, recorded from central and lower Amazon basin, Tocantins river, and coastal drainages in Guyana, Suriname, French Guiana, and eastern Pará State, Brazil, is distinguished by the short postcleithral process, small eye and long snout. Tatia neivai, from the upper Paraná river , Paraguay river and upper Paraíba do Sul river basin, is distinguished by its unique vertebral count and caudal-fin coloration consisting of transverse dark bars. Tatia strigata, from central Amazon basin and Negro river, is distinguished by its horizontally striped color pattern and the modified male anal fin with middle rays reduced in length. Tatia caxiuanensis, a new species described from the Curuá river, lower Amazon basin, is recognized by its wide cranial fontanel and distinctive anal fin in mature males. Tatia meesi, a new species described from the Essequibo river basin, Guyana, is distinguished from congeners by the cranial fontanel with two separate openings and thin nasal bone. Tatia nigra, a new species described from the central Amazon basin, is distinguished by its short postcleithral process, low number of vertebrae, and dark color pattern. All twelve species of Tatia are described or redescribed and a key to species is provided.

Three new species of seasonal killifishes of the Simpsonichthys antenori species group (Teleostei: Cyprinodontiformes: Rivulidae) from the rio São Francisco basin, Brazil

Three new species of the Simpsonichthys antenori group from the upper sections of eastern drainages of the middle rio São Francisco, serra do Espinhaço, are described. Simpsonichthys janaubensis, new species, from the rio Gorutuba floodplains, upper rio Verde Grande drainage, shares a derived color pattern of anal fin in males with S. flavicaudatus and S. flagellatus, but differs from them in having a more slender body, a shorter anal-fin base, and a distinctive color pattern of the dorsal fin in males. Simpsonichthys mediopapillatus, new species, from the rio São Domingos drainage, a part of the upper rio Verde Grande drainage, is similar to S. ghisolfii in having a long urogenital papilla and a light orangish-yellow subdistal stripe on the anal fin in males, and it is distinguished from all congeners in having a median neuromast on the posterior rostral series. Simpsonichthys macaubensis, new species, from the upper rio Paramirim drainage, differs from other species of the S. antenori group by a combination of features, including presence of contact organs on the flank in males, dorsal and anal-fin filaments reaching central portion of caudal fin in males, urogenital papilla short in males, and anal fin yellow, with a distal black stripe and iridescent dots over the entire fin in males. A key for identification of species of the S. antenori group is provided.

Taxonomy and phylogenetic relationships among species of the seasonal, internally inseminating, South American killifish genus Campellolebias (Teleostei: Cyprinodontiformes: Rivulidae), with the description of a new species

Campellolebias, a genus of South American annual killifishes, is diagnosed by a unique specialized structure, the pseudogonopodium, on the anterior part of the anal fin in males, which is used for internal insemination; a derived caudal skeleton morphology; an apomorphic color pattern on the ventral portion of the head in males; and a unique courtship behavior pattern in males. Four species are included, all endemic to Brazil’s southern coastal plains: C. dorsimaculatus and C. intermedius n. sp., from the rio Ribeira de Iguape basin, São Paulo; C. chrysolineatus, from northern Santa Catarina; and C. brucei, from southern Santa Catarina. A clade comprising C. intermedius, C. chrysolineatus and C. brucei is defined by the pelvic-fin bases medially separated by a short interspace, seven longitudinal rows of iridescent marks on the flank in males, and dark horizontal lines between flank scales on females. A clade comprising C. chrysolineatus and C. brucei is diagnosed by long dorsal, anal and pelvic fins in males.

Age and growth of Indo-Pacific sailfish, Istiophorus platypterus, from the Arabian Gulf

Dorsal and anal fin spines were collected from 85 sailfish from the Gulf and used to estimate age from putative annular growth bands observed in thin transverse sections. A total of 84 (98.8%) of these were successfully read with an average percent error in precision of 4.8%. Nine year classes (0+ to 8) were estimated from spines examined. Spines lacking a pair of translucent and opaque rings were placed in the 0+ year class; however the somatic size of these individuals suggested they were between 6 and 10 months in age. Estimated age classes for females ( n = 50) ranged from 0+ to 8 years, while males ( n = 34) ranged from 0+ to 6 years. Age class 1, followed by 0+ and 3 were the most abundant for both sexes, comprising 75% of all samples. Females exhibited the maximum sizes for lower jaw-fork length (LJFL) and weight within 101 sampled sailfish. The LJFL for females ( n = 65) ranged in size from 129 to 199 cm and weight ranged from 11.5 to 47.0 kg. For males ( n = 36), LJFL ranged from 125 to 177 cm and weight ranged from 12.5 to 38.0 kg. The von Bertalanffy growth function fitted to the observed LJFL, weight and age data indicated a rapid growth rate during the first 2 years, after which length stabilized for males and females continued growing to a greater maximum mean length and weight. The relationships of measured morphological traits to LJFL derived from the non-linear equation Y = a LJFL b and their regression coefficients showed a negative allometric growth for weight, head, and pelvic fin length. Most other measurements were effectively isometric, with the exception of the anal fin in males, which showed positive allometric growth. A comparison of allometric growth between females and males using a modified t-test against linear regressions indicated no significant differences between LJFL and other morphometric characters ( P ranged 0.135–0.980).

A new rainbowfish (Teleostei: Melanotaenioidei: Bedotiidae) from the southeastern highlands of Madagascar, with comments on the biogeography of Bedotia

Bedotia albomarginata, a new species of Malagasy rainbowfish, is described from forested habitats in the southeastern highlands of Madagascar. The new species is distinguished from congeners by the presence of broad white margins on the second dorsal fin and anal fin in males, a markedly lanceolate caudal fin in adult males, and in life, by a bright yellow to orangish-red anal fin in both sexes. Bedotia albomarginata is known only from small streams and swamps within the upper to middle reaches of the Mananara and Rienana river drainage basins.

Austrolebias univentripinnis sp. nov. (Teleostei: Cyprinodontiformes: Rivulidae): a new annual killifish from the Mirim Lagoon basin, southern Brazil

Austrolebias univentripinnis n. sp. is described from the Jaguarão River floodplains, Mirim Lagoon basin, southern Brazil. It is a member of a clade that also includes A. viarius, A. arachan, A. adloffi, A. charrua, A. minuano, A. nigrofasciatus, A. vandenbergi, A. bellottii, and A. melanoorus, which is diagnosed by the possession of a long and triangular anal fin in females. The new species is similar to A. bellottii and A. melanoorus in having the urogenital papilla completely attached to the anal fin in males; it differs from A. bellottii in having the dorsal fin more anteriorly placed in males, a shorter anal-fin base, lesser body depth, and wider basihyal; it is distinguished from A. melanoorus by the number of rostral neuromasts, degree of pelvic-fin fusion, morphology of dorsum in females, color pattern of unpaired fins in males, and color pattern of flank in both sexes.

The role of the anal fin in fertilization success in male medaka, Oryzias latipes

SUMMARY: The anal fin of the medaka Oryzias latipes is sexually dimorphic, with mature males developing a larger anal fin than females. To determine the functions of the male anal fin during mating, an anal fin-removal experiment was conducted. Males were mated with females in successive treatments in which different portions of the anal fin were removed. Male medaka with half of their anal fin removed fertilized a significantly lower proportion of eggs than did males with a normal anal fin. The results show that the anal fin in male medaka is important for efficient fertilization, suggesting selection for a larger anal fin.

Age Composition, Growth and Reproductive Biology of the Salamanderfish Lepidogalaxias salamandroides: A Re-examination

This study has determined the age and size compositions, growth rate and reproductive biology of Lepidogalaxias salamandroides using data for fish of known sex and age and the monthly trends exhibited by various gonadal variables, including the sizes and stages of the oocytes. The results resolve conflicting conclusions drawn by other workers concerning certain aspects of the biology of this freshwater species and expands our knowledge of this teleost. Our results are based on data derived from samples collected from small, ephemeral acidic pools in south-western Australia in 22 consecutive months. Although ca. 78% of the fish caught belonged to the 0+ age class, substantial numbers of the 1+ and 2+ age classes and some 3+ and 4+ fish were caught. Spawning occurs between late May and late August, with peak activity in late July and early August. During the first year of life, growth is initially rapid, but then ceases in the weeks immediately prior to and during the period when the habitat becomes dry and fish aestivate, before recommencing in autumn as the pools again become filled with water. The growth coefficient (K) in the von Bertalanffy growth equation was lower for females (0.63) than males (1.28), reflecting the greater growth undergone by females after the first year of life. Maturity was attained by ca. 28% of the females and ca. 26% of the males that reached the end of their first year of life and by all fish that reached the end of subsequent years of life. The L50s for females and males at first maturity were 43.2 and 38.6 mm TL, respectively. The mean fecundity was only 82.4, reflecting a combination of a small body size and a relatively large egg (diameter=1.8 mm). Lepidogalaxias salamandroides is a multiple spawner, which increases the chances of some eggs and newly-hatched embryos encountering a period of favourable environmental conditions during the spawning period, which is characterised by bouts of heavy rainfall. The ratio of females to males was essentially parity in the 0+ and 1+ age classes and in all age classes collectively. When testes commence maturing for the first time, the anal fin of males starts to become modified to form a structure that facilitates the transfer of sperm to the female, and it remains modified throughout the rest of life.

Effects of 4-Nonylphenol on Sex Differentiation and Puberty in Mosquitofish (Gambusia holbrooki)

Three days post-parturition mosquitofish were exposed to different concentrations of 4-NP following a semi-static protocol. Exposure lasted up to the development of male anal fin in male individuals of the control group. Exposure to 50 μg/L 4-NP resulted in 100% females considering secondary sexual characters, while external sex-ratio did not statistically differed from unity in control group. In group exposed to 0.5 and 5.0 μg/L sex-ratio did not differ from unity but incompletely developed gonopodium was observed in several individuals. Individuals exposed to 50 μg/L 4-NP exhibited female or undeveloped gonads, while gonadal sex-ratio did not statistically differ from unity in control group. Percentage of undeveloped gonads increased with 4-NP concentration. Additional observations demonstrated hepatic histopathology in fish exposed to the highest concentration and growth reduction dependent on 4-NP concentration. In a complementary experiment, extensive metabolism of [3H]4-n-NP was characterized following in vivo exposure of juvenile mosquitofish suggesting that metabolism could modulate 4-NP toxicity. This study suggests susceptibility of early life stages of mosquitofish to endocrine modulators with regard to development of reproductive capabilities.

Mating Behavior of Zenarchopterus gilli and Zenarchopterus buffonis and Function of the Modified Dorsal and Anal Fin Rays in Some Species of Zenarchopterus (Teleostei: Hemiramphidae)

Anecdotal field observations are reported for the first time for the genus Zenatr chopterus. In Z. buffonis, a species with only slightly modified male dorsal and anal fin rays, male and female swim in parallel, the male flicking the posterior body part against the female. In Z. gilli, a species with highly modified male dorsal and anal fin rays, the male swims alongside the female, folding the dorsal and anal fins in her direction, to cling to her. The function of the modified fins of male Zenarchopterus had not yet been explained, and we hypothesize that in some species with dramatic modifications, the dorsal and anal fin function as a clasping mechanism.

Testis and Andropodial Development in a Viviparous Halfbeak, Dermogenys sp. (Teleostei: Hemiramphidae)

Andropodial and testicular development in a viviparous halfbeak, Dermogenys sp., is described from birth to sexual maturity. Gradual transformation of the anterior seven rays in the male anal fin takes place through the 9.0 mm-18.0 mm SL stages. Changes include an increase in number of segments in all rays, a thickening of rays 1-5, and marked curvature of rays 1-7. The 20.5 mm-26.0 mm stages are characterized by development of the tridens flexibilis, a pair of spines, and a hook, the spiculus, on the distal portion of the second anal-fin ray. Serrations also develop on the second and fourth fin rays. A mature andropodium possesses a pair of welldeveloped spines and a single, segmented, sickle-shaped spiculus on the second ray. Testicular maturation coincides with andropodial maturation. Throughout fin transformation, testes continue to develop. Male and female gonads are differentiated at birth. Within the testes, isolated spermatogonia proliferate through the 15.0-mm stage. By 18.0 mm, late-stage spermatogonia within spermatocysts are evident. By 20.5 mm, spermatocysts containing late spermatids are present. Sexual maturation, defined as presence of mature spermatozoa within testicular ducts, occurs at a length of 22.5 mm or greater. The testes of Dermogenys, which are typical atherinomorph testes, contain large, complete spermatozeugmata within the testicular ducts. These findings provide a morphological basis for identifying ontogenetic stages of the anal fin and for recognizing and comparing mature andropodia among species of Dermogenys for use in future phylogenetic analyses. T HE family Hemiramphidae, containing the

Organizational–Activational Concept Revisited: Sexual Differentiation in an Atherinomorph Teleost

Because of its numerous sexually dimorphic characters, the Western mosquitofishGambusia affinis affinisis an excellent vertebrate system for addressing questions concerning sexual differentiation. In this review, the actions and limits of gonadal sex steroids, specifically testosterone, on the development of the sexually dimorphic anal fin and its axial and appendicular support are described. Data from our laboratory show that the critical period in this species for the anterior transposition of the male anal fin and its appendicular support occurs during the late embryonic period and that this differentiation of the male phenotypic genital areaduring the critical period is regulated by androgen.

Oral Fertilization in a Mouthbrooding Cichlid Fish

AbstractIt has been hypothesized that in maternal mouthbrooding cichlids the conspicuous markings on the male's anal fin function as “egg‐dummies” by fooling the female into snapping at them, thereby inhaling sperm and assuring fertilization of the eggs in the mouth. I show experimentally in Pseudocrenilabrus multicolor, an East African maternal mouthbrooder, that indeed oral fertilization takes place. Nevertheless, external fertilization plays a significant role, too.

The reproductive cycle of the viviparous seaperch, Cymatogaster aggregata Gibbons

The natural reproductive cycle of male and female Cymatogaster aggregata is described with reference to gametogenesis, development of secondary sex structures, reproductive behavior, and gestation. Spermatocytogenesis starts in early spring and by June or July clusters of spermatozoa fill the seminiferous tubules. Concurrently the Sertoli cells and interstitial cells of Leydig increase in size and secondary sex structures develop on the male anal fin. When the sexes mingle in summer, the males perform very elaborate reproductive behavior. Fertilization occurs about mid-December—5 months after mating—and the ovary is then modified to maintain the young embryos until parturition in mid-summer. Oocyte formation is highest in July and August, just after parturition, while vitellogenesis and oocyte maturation occur mainiy from October to December. These seasonal changes are discussed in relation to changes in environmental temperature and photoperiod.