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The shape of the urogenital papilla is used to visually determine the sexual dimorphism of Dormitator maculatus. However, it is occasionally not possible to determine this in practice. The objective of the present study was to propose and statistically validate other morphometric measures to fulfill this same purpose. The analysis was designed on the basis of a group of previously identified adults with urogenital papilla. It was found that the most useful morphometric measures are related to the size and weight of the species. The dorsal fins and the geometric structure of the head were also recommended as morphometric measures. The males are larger in size, they are robust with the fin 1DFL longer compared to the 2DFL fin and have a broad, elongated head. Females are smaller in size, slightly robust, with longer 2DFL fins compared to 1DFL fins, and have slender, not elongated heads. In the Alvarado lagoon, sexual differentiation in D. maculatus is important due to the selective exploitation of its gonads (mainly on females). For this reason, and to avoid errors in the identification of females for protection purposes, the results obtained are a viable alternative. [ABSTRACT FROM AUTHOR]

ABSTRACT Sexual dimorfism refers to morphological differences between males and females of a species. It may be a result of different selection pressures acting on either or both sexes and may occur in any sexually-reproducing dioecious species, including fishes. We analyzed 63 females and 63 adult males of Gymnorhamphichthys rondoni (Gymnotiformes) collected by us or deposited in museum collections. Sex was identified through abdominal dissection. We measured length from snout to posterior end of anal-fin, anal-fin length, distance from anus to anal-fin origin, distance from genital papilla to anal-fin origin, body width at beginning of anal-fin, and head length. Morphometric data submitted to a Principal Component Analysis (PCA) grouped males and females according to variables related to body size (along the first component) and to head length and body height along the second and third components. Females were larger than males, whereas males had proportionally larger heads and higher bodies than females. The urogenital papilla of males and females showed differences in shape, size and relative position on the body. The female papilla was elongated horizontally, larger than that of males, and was located on a vertical line below the eye, while the papilla of the males was vertically elongated and located on a vertical line below the operculum. To our knowledge, this is the first recorded case of sexual dimorphism in a species of Rhamphichthyidae, a condition that is now known in all the currently recognized families of Gymnotiformes.

In this paper, we describe a new non-damaging internal tissue sampling method for preserved collection of teleostean specimens. It was tested on freshwater pipefish, as external tissue sampling is made difficult by the lack of scales, the lack of pelvic fins, the atrophy of pectoral and anal fins. The internal tissue is detached by scratching the inside of the urogenital papilla with a fine metallic probe. 95% ethanol is injected using a fine syringe, and then sucked back into the syringe with the detached tissue. This protocol has been tested on 6 specimens from 5 species of pipefish. For each specimen DNA was extracted from the internal tissue, a caudal fin clip, and when possible, eggs sampled from the male brooding pouch. Partial Cytochrome c oxydase I (COI) was amplified and sequenced. For each specimen, the 582 bp long sequences obtained from the internal tissue, the fin clip and the eggs were identical. These results validate this non-damaging internal tissue sampling method, which leaves absolutely no trace on the specimen. Although this method was developed on pipefish, it could be applied to other teleostean, even precious museum collection specimens such as type specimens. The aim of this paper, using the example of freshwater pipefish, is to present this method, which aims at preserving precious collection specimens while still valorising them. [ABSTRACT FROM AUTHOR]

A uniquely colored dwarfgoby, Eviota erdmanni n. sp., with a cup-like urogenital papilla in males, a cephalic sensory-canal pore system lacking only the IT pore (pattern 2), some branched pectoral-fin rays, and a dorsal/anal fin-ray formula of 9/8 is described from south Flores, Indonesia. We use molecular data from both mitochondrial and nuclear genes to infer the phylogenetic relationship of the new species with respect to its congeners, with specific emphasis on species with uniquely shaped urogenital papillae. [ABSTRACT FROM AUTHOR]

Fishes exhibit a dynamic array of reproductive diversity. Among the various forms of reproduction, internal fertilization has evolved at least 13 times and has been observed in 2-3% of teleost species, half of which are marine. Internal fertilization has led to the evolution of male intromittent organs to aid in sperm transfer during copulation. The intromittent organs of poeciliids have been widely investigated, but little research has focused on the intromittent organs of marine fishes. The surfperches are internally fertilizing, viviparous fishes with a ventrally located papilla. In this article, the external morphology of 19 Embiotocidae species was examined. Additionally, paraffin histology was used to investigate the walleye surfperch (Hyperprosopon argenteum), black perch (Embiotoca jacksoni), and dwarf perch (Micrometrus minimus) papilla to aid in the identification of tissue composition to determine its function. External morphology was documented via macro photography and males were dissected to observe the relationship between the testes, spermatic duct, and papilla. We provide histological evidence that the urogenital papilla is directly connected to the spermatic duct and testis and likely involved in spermatozeugmata transfer. Our research also determined that the papillae were composed of both urinary and reproductive tissues, thus we propose the papilla be referred to as a urogenital papilla. Our study contributes to an overall understanding of intromittent organs of marine fishes, particularly in the surfperches, which has not been previously documented., (© 2021 American Association for Anatomy.)

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., (© 2021 The Authors. Journal of Morphology published by Wiley Periodicals LLC.)