Trophic morphology and diet of the endangered fish Tlaloc hildebrandi (Cyprinodontiformes: Profundulidae) / Morfología trófica y dieta de Tlaloc hildebrandi (Cyprinodontiformes: Profundulidae), especie amenazada de extinción

Abstract Introduction: Tlaloc hildebrandi is a freshwater killifish, endemic to Southern Mexico and under threat of extinction; the knowledge of the trophic morphology and diet is needed by conservation managers. Objective: To analyse and describe the anatomy of the visceral skeleton, visceral musculature, digestive tract and its adjoining glands of T. hildebrandi; as well as its diet. Methods: We performed the trophic anatomy on 20 adult specimens of both sexes, through manual dissection; as well as gut content analysis in 60 individuals to describe the diet. Results: As notable characters of the visceral skeleton of T. hildebrandi we found the posterior notch of the premaxillary, the presence of the "coronoid cartilage", the tricuspid shape of the gill rakers of the first branchial arch, and the presence of the coronomeckelian bone; some outstanding characters of the visceral musculature are the origin of the retractor dorsalis muscle from the first four vertebral centra, and the division of the pharyngoclavicularis externus muscle into two sections. The notable characters of the digestive tube are the absence of stomach and pyloric caeca, and the presence of the "intestinal valve". Insects (IVI = 66.6 %) and ostracods (13 % IVI) were the dominant prey items of the Tlaloc hildebrandi diet; larvae and adults of the family Chironomidae were the most dominant insects in the diet (53 % IVI). Conclusions: The organization of the digestive system of T. hildebrandi corresponds to the general morphologic pattern of the Cyprinodontiformes; however, we register as new information for these fish, the presence of the "coronoid cartilage" and the "intestinal valve". The structures of the trophic morphology and the components of the diet, confirms us that T. hildebrandi is a carnivorous-insectivorous fish.

Resumen Introducción: Tlaloc hildebrandi es un killi de agua dulce, endémico del sur de México y bajo amenaza de extinción; el conocimiento de la morfología trófica y la dieta son necesarios para los administradores de la conservación. Objetivo: Analizar y describir la anatomía del esqueleto visceral, la musculatura visceral, el tracto digestivo y las glándulas adyacentes de T. hildebrandi; así como los componentes de su dieta. Métodos: Mediante la técnica del descarnado manual, realizamos la descripción de la anatomía trófica en 20 especímenes adultos de ambos sexos, y el análisis del contenido estomacal en 60 individuos para describir la dieta. Resultados: Como caracteres sobresalientes del esqueleto visceral de T. hildebrandi está la escotadura posterior del premaxilar, la presencia del "cartílago coronoides", la forma tricúspide de las branquiespinas del primer arco branquial y la presencia del hueso coronomeckeliano; como caracteres de la musculatura visceral sobresalen el origen del músculo retractor dorsalis de los cuatro primeros centros vertebrales, y la división del músculo pharyngoclavicularis externus en dos secciones. Los caracteres notables del tubo digestivo son la ausencia de estómago y de ciegos pilóricos y la presencia de la "válvula intestinal". Los insectos (IVI = 66.6 %) y ostrácodos (13 % IVI) fueron los componentes dominantes de la dieta de T. hildebrandi; particularmente las larvas y adultos de la familia Chironomidae fueron los insectos más abundantes en la dieta (53 % IVI). Conclusiones: La organización del sistema digestivo de T. hildebrandi corresponde al patrón morfológico general de los Cyprinodontiformes, sin embargo, se registra como nueva información para estos peces, la presencia del cartílago coronoides y la válvula intestinal. Las estructuras de la morfología trófica y los componentes de la dieta nos confirman que T. hildebrandi es un pez carnívoro-insectívoro.

Color Discrimination Provides Insight into the Relationship between Personality Cognition and Brain Morphology in the Western Mosquitofish (Gambusia affinis).

Recent studies on the differences in cognitive ability between individuals focused on two aspects: one is whether the individual differences in cognitive ability are related to brain size, the other is whether they pertain to certain personality traits. To explore these two hypotheses, we tested the personality traits, cognitive abilities, and brain volumes of western mosquitofish (Gambusia affinis). First, a color preference test was conducted to select two unbiased colors for G. affinis for subsequent cognitive tests. The results showed that G. affinis had a great preference for red and green to yellow and blue; therefore, the red-green combination was selected for the study of cognitive abilities. Then, we explored the relationship among cognition, personality, and brain morphology through cognitive abilities tests, personality traits, and brain volume measurements. We found that there was a trade-off among cognition, personality, and brain morphology. For example, more active individuals found food faster, but had also poor memory; Those individuals with larger corpus cerebelli were bolder while they were less likely to find food; The individuals that found food faster were more active and had a smaller inferior lobe. The color preference test provides a reliable way for selecting unbiased colors for behavioral studies in G. affinis. Meanwhile, our study indicates that there exists a balance mechanism among cognition, personality, and brain morphology.

Effects of crowding stress on the hypothalamo-pituitary-interrenal axis of the self-fertilizing fish, Kryptolebias marmoratus.

We tested whether crowding stress affects the hypothalamo-pituitary-interrenal (HPI) axis of the self-fertilizing fish, Kryptolebias marmoratus, which is known to be aggressive in the laboratory conditions but sometimes found as a group from a single land crab burrow in the wild. The projection of corticotropin-releasing hormone (CRH) neurons to the adrenocorticotropic hormone (ACTH) cells in the pituitary was confirmed by dual-label immunohistochemistry; CRH-immunoreactive (ir) fibers originating from cell bodies located in the lateral tuberal nucleus (NLT) of the hypothalamus were observed to project to ACTH-ir cells in the rostral pars distalis of the pituitary. Then, fish were reared solitary or in pairs for 14 days, and the number of CRH-ir cell bodies in the NLT of the hypothalamus and cortisol levels in the body without head region were compared. The number of CRH-ir cell bodies and cortisol levels were significantly higher in paired fish. These results indicate that crowding stress affects the HPI axis in K. marmoratus which thrive in small burrows with limited water volume.

Sex differences in behavioural and anatomical estimates of visual acuity in the green swordtail, Xiphophorus helleri.

Among fishes in the family Poeciliidae, signals such as colour patterns, ornaments and courtship displays play important roles in mate choice and male-male competition. Despite this, visual capabilities in poeciliids are understudied, in particular, visual acuity, the ability to resolve detail. We used three methods to quantify visual acuity in male and female green swordtails (Xiphophorus helleri), a species in which body size and the length of the male's extended caudal fin ('sword') serve as assessment signals during mate choice and agonistic encounters. Topographic distribution of retinal ganglion cells (RGCs) was similar in all individuals and was characterized by areas of high cell densities located centro-temporally and nasally, as well as a weak horizontal streak. Based on the peak density of RGCs in the centro-temporal area, anatomical acuity was estimated to be approximately 3 cycles per degree (cpd) in both sexes. However, a behavioural optomotor assay found significantly lower mean acuity in males (0.8 cpd) than females (3.0 cpd), which was not explained by differences in eye size between males and females. An additional behavioural assay, in which we trained individuals to discriminate striped gratings from grey stimuli of the same mean luminance, also showed lower acuity in males (1-2 cpd) than females (2-3 cpd). Thus, although retinal anatomy predicts identical acuity in males and females, two behavioural assays found higher acuity in females than males, a sexual dimorphism that is rare outside of invertebrates. Overall, our results have implications for understanding how poeciliids perceive visual signals during mate choice and agonistic encounters.

Sharply Angled Lateral Curvature Modification in Anal Fin of a Viviparous Fish, Xenotoca variata (Cyprinodontiformes: Goodeidae).

Almost all viviparous species possess male external genitalia; for example, the mammalian penis is an intromittent organ. Some live-bearing bony fish use their anal fins to assist in mating and internal fertilization. We previously reported a male-specific asymmetric curvature at the posterior end of the anal fin in Xenotoca eiseni, a viviparous fish of the family Goodeidae. However, three other goodeid species, Xenotoca melanosoma, Zoogoneticus quitzeoensis, and Chapalichthys pardalis, examined in that study possessed lesser anal fin curvature modifications as compared to those in the anal fin of X. eiseni. Here, we report the second case of acute-angled curvature modification of the male anal fin in the family Goodeidae. We obtained a dead specimen of the goodeid species Xenotoca variata from a city zoo in Japan, and the morphological and histological analyses indicated an acute-angled asymmetric curvature of the posterior end of the anal fin in X. variata, similar to that observed in X. eiseni in the previous study. However, in our previous report, obtuse-angled modification was only observed in one other Xenotoca species, X. melanosoma, and two species belonging to other genera, Z. quitzeoensis and C. pardalis. Therefore, our findings suggest that the acute-angled curvature in the male anal fin has been developed in the genus Xenotoca.

The Genetic Architecture of Variation in the Sexually Selected Sword Ornament and Its Evolution in Hybrid Populations.

Biologists since Darwin have been fascinated by the evolution of sexually selected ornaments, particularly those that reduce viability. Uncovering the genetic architecture of these traits is key to understanding how they evolve and are maintained. Here, we investigate the genetic architecture and evolutionary loss of a sexually selected ornament, the "sword" fin extension that characterizes many species of swordtail fish (Xiphophorus). Using sworded and swordless sister species of Xiphophorus, we generated a mapping population and show that the sword ornament is polygenic-with ancestry across the genome explaining substantial variation in the trait. After accounting for the impacts of genome-wide ancestry, we identify one major-effect quantitative trait locus (QTL) that explains ~5% of the overall variation in the trait. Using a series of approaches, we narrow this large QTL interval to several likely candidate genes, including genes involved in fin regeneration and growth. Furthermore, we find evidence of selection on ancestry at one of these candidates in four natural hybrid populations, consistent with selection against the sword in these populations.

Structure of the gonoduct of the viviparous teleost Cnesterodon decemmaculatus (Jenyns, 1842) (Poeciliidae).

During embryogenesis, teleost females do not develop Müllerian ducts, which form the oviducts in all other vertebrates. Thus, when they reach sexual maturity they do not have oviducts. In viviparous teleosts, the lack of oviducts means that the development of the embryos occurs as an intraovarian gestation, unique among vertebrates. The ovary is an unpaired hollow organ whose cavity is continuous with the caudal portion, the gonoduct, characterized by the absence of germinal cells, which opens to the exterior at the gonopore. The gonoduct attains essential function as a barrier between the germinal region of the ovary and the exterior during all reproductive stages. This study describes the functional morphology of the gonoduct in the viviparous teleost Cnesterodon decemmaculatus during non-gestation (previtellogenesis and vitellogenesis) and gestation. The ovaries were processed using histological techniques and stained with hematoxylin-eosin, and periodic acid Schiff. The gonoduct has two regions: cephalic and caudal, and is formed by three histological layers, which are, from inside to the periphery: (a) tunica mucosa; (b) tunica muscularis; and (c) tunica serosa. In the cephalic region there are mucosal folds extending into the lumen and forming a structure similar to a cervix. The histology of the gonoduct indicates essential functions, that is, (a) the control of the luminal diameter in the limit to the germinal region of the ovary by the presence of a cervix; (b) during insemination the gonoduct receives the spermatozoa, may store and transport them to the germinal region; (c) the presence of melano-macrophage centers indicates support of immunological processes, especially during gestation when these centers increase in size; (d) production of exocrine secretions; and (e) it is the birth canal, internally lined by an ciliated epithelium and surrounded by smooth musclesboth tissues supposedly supporting the birth process.

Histological observation of the reproductive system in a viviparous teleost Xenotoca eiseni Rutter 1896 (Cyprinodontiformes: Goodeidae).

Xenotoca eiseni is a viviparous teleost belonging to the family Goodeidae. Here, we report histological observations of the reproductive organs in an adult male, an adult female, a pregnant female with intraovarian embryo and an extracted embryo of X. eiseni. High-resolution images of haematoxylin-eosin-stained sagittal sections revealed the detailed structure of gonads, gametes and reproductive components of the mother-embryo relationship. In the male, mature spermatozoa in the epididymis formed sperm packages. In the female, oogenesis proceeded asynchronously in the ovarian wall, and various stages of oocytes were observed in single ovary. In both sexes, genital openings were located between the anus and anal fin. Developing embryos were observed in an ovary of the pregnant female. Fine structures of components of the mother-to-embryo nutrient supply, ovarian septum and trophotaenia were observed in the pregnant ovary. An immature gonad prior to gamete formation was identified in the extracted embryo. With the aim of supporting the development and extension of studies on this viviparous teleost, we have shared our histological images as raw data in an open online archive, the 'NAGOYA repository (http://hdl.handle.net/2237/00032456)'. Our goal is a comprehensive understanding of the viviparous system in fish using both histological observation and molecular biology methods including genomics and proteomics.

The Developmental and Genetic Architecture of the Sexually Selected Male Ornament of Swordtails.

Sexual selection results in sex-specific characters like the conspicuously pigmented extension of the ventral tip of the caudal fin-the "sword"-in males of several species of Xiphophorus fishes. To uncover the genetic architecture underlying sword formation and to identify genes that are associated with its development, we characterized the sword transcriptional profile and combined it with genetic mapping approaches. Results showed that the male ornament of swordtails develops from a sexually non-dimorphic prepattern of transcription factors in the caudal fin. Among genes that constitute the exclusive sword transcriptome and are located in the genomic region associated with this trait we identify the potassium channel, Kcnh8, as a sword development gene. In addition to its neural function kcnh8 performs a known role in fin growth. These findings indicate that during evolution of swordtails a brain gene has been co-opted for an additional novel function in establishing a male ornament.

Description of two new miniature species of Hylopanchax Poll & Lambert, 1965 (Cyprinodontiformes: Procatopodidae), from northeastern Gabon, with an updated diagnosis of the genus based on morphology, colouration and osteology.

Two new species of the lampeye genus Hylopanchax are described from the Ivindo River basin in the Ogowe River drainage. Hylopanchax multisquamatus, new species, and Hylopanchax thysi, new species, differ from congeners by the presence of a hyaline urogenital male papilla with small black spots and a dark-brown reticulate pattern on the flanks of both males and females in preserved specimens. Hylopanchax multisquamatus is distinguished from congeners by the number of scales on the mid-longitudinal series (27-30 vs. 19-26, respectively) and by the relative anterior/posterior flank scale depth ratio (140%-150% vs. 170%-220%). Hylopanchax thysi is distinguished from all other congeners, except Hylopanchax paucisquamatus, by the presence of vertebrae (30 vs. 31-33) and is further distinguished from H. multisquamatus by the presence of a deeper caudal peduncle and much larger anterior flank scales. It is distinguished from H. paucisquamatus by the presence of a hyaline urogenital male papilla with small black spots and a dark-brown reticulate pattern on the flanks of both males and females in preserved specimens. Osteological data of Hylopanchax are presented for the first time, and an updated diagnosis based on external morphology, colouration pattern and osteology is provided. An osteological comparison with closely related species belonging to the genera Procatopus, Hypsopanchax and "Hypsopanchax" is presented. (a) A truncate and slightly downward-directed anterior process of the angulo-articular and (b) a guitar-shaped lachrymal with both its anterior and posterior margins sharply curved are here considered as diagnostic features of Hylopanchax.

Microanalysis of scale morphology in killifish, Aphaniops hormuzensis inhabiting ecologically diverse environments (Cyprinodontiformes; Aphaniidae).

Ecologically, Aphaniops hormuzensis populations occupying diverse environments in southern Iran and showed substantial morphological variation across its range. In this study, three different habitats were chosen and identified as group A (sulfur rich spring), group B (salty River), and group C (urban canal), and scale microstructures and scale shape was inspected among three groups. The SEM imaging indicated that lepidonts were more developed on the scale of larger (group C, SL > 30 mm) than younger fish (group A, SL < 30 mm). We tentatively concluded that lepidonts are formed during scale development so that in the earlier stages of fish development, scales probably do not have lepidont. Also, the size and shape of lepidonts vary between the populations, and their shape and orientation within a given species affected by the fish size rather than the local ecological conditions of habitats. The number of radii was relatively higher in group C (12.58 ± 0.66 in males and 13.00 ± 1.89 in females). Similar to what is mentioned before in the case of lepidont, the inter-population variation in the number of radii seems to be influenced by fish size. Group A (SL < 30 mm) had a relatively large focus diameter (0.14 ± 0.02 in males and 0.36 ± 0.44 in females). It is assumed that the focus size is large at the earlier stage of fish development, but later during the fish growth, and by increasing the scale size, the focus diameter is reduced. In conclusion and agreement with previous studies, scale surface morphology and microstructure could be employed to discriminate certain populations, while scale size and J-indices could not help in distinguishing the populations. It is also proposed that the characteristics of scale morphology in the population-level are influenced by the combination of genetic, and environmental factors, as well as fish development.

Sex Differences in the Swordtail Xiphophorus hellerii Revealed by a New Method to Investigate Volumetric Data.

Comparing the relative volumes of body parts is a useful tool in morphology, but it is not trivial to do this in animals that differ in overall size. To account for scaling differences, a "reference size" has to be determined and the original absolute volumes have to be "corrected for" by this scaling reference. However, the outcome of a statistical analysis is greatly affected by this "reference size," and it is practically impossible to determine the "overall size" of a structure independent of the changes in the relative size of the parts of it. Here, a new method is introduced to compare the relative volumes of parts that does not need a scaling reference. The method transforms the absolute part volumes into a ratio matrix (volume ratio transformation, VRT). The VRT is free of any scaling factors and can be used to compare groups of animals. This paper also reviews various other errors made frequently when comparing brain morphology between animals. Finally, the VRT is applied to investigate sex differences in the swordtail fish (Xiphophorus hellerii), which show profound differences in the size of the valvula cerebelli.

A Pleistocene freshwater ichthyofaunal assemblage from central Argentina: What kind of fishes lived in the Pampean lagoons before the extinction of the megafauna?

This study contributes to the knowledge of continental fishes recovered from sedimentary successions corresponding to the Bonaerean Stage/Age (late mid-Pleistocene) in the locality of Centinela del Mar, General Alvarado County, Buenos Aires province, Argentina. At this site we describe fossil fishes from a palaeolagoon, including Corydoras sp., Pimelodella sp., Rhamdia sp., Oligosarcus sp., small undetermined characids, Jenynsia sp. and Odontesthes sp. The recovered ichthyofaunal assemblage comprises at least seven taxa of Paranaean lineage. The taxonomic composition of the palaeoichthyofauna is quite comparable to that presently found in Bonaerean Watercourses of the Atlantic Drainage ecoregion. This suggests that local ichthyofaunal communities have remained relatively stable since the late mid-Pleistocene.

Descripción morfológica e histológica del tejido hepático de Gambusia holbrooki (Pisce: Poeciliidae) que habita en la Provincia de Arica - Chile / Morphological and histological description of the liver tissue of Gambusia holbrooki (Pisce: Poeciliidae) inhabiting the Province of Arica - Chile

Gambusia holbrooki es el pez de agua dulce con mayor distribución en Chile y el mundo, pero los estudios que abordan la morfología e histología hepática del pez son escasos. El hígado es utilizado para evidenciar efectos subletales de contaminantes ambientales y es preciso contar con una descripción histomorfológica del hígado para futuros estudios comparativos. El presente estudio tiene como objetivo describir patrones histomorfológicos del hígado de Gambusia holbrooki, para ello se colectaron 97 individuos adultos de los sistemas límnicos de los valles de Lluta y Azapa (Extremo norte de Chile), para observar patrones morfológicos comunes en ambas poblaciones, se utilizó técnicas histológicas de rutina e histoquímica. Las evidencias demostraron que el hígado contiene tejido pancreático y su arquitectura tisular es trabecular con mayor presencia de capilares sinusoides.

Gambusia holbrooki is the freshwater fish with the greatest distribution in Chile and the world. However, studies dealing with morphology and liver histology of fish are scarce. The liver commonly shows the sublethal effects of environmental pollutants and there should be a histomorphological description of the liver for further comparative studies. The present study aims to describe histomorphological patterns of the liver of Gambusia holbrooki. A total of 97 adult individual specimens were collected from the ecosystems in the valleys of Lluta and Azapa (Region of Arica and Parinacota), to observe patterns morphologically common in both populations. Routine histological and histochemical techniques were used for analysis. The evidence showed that the liver contains pancreatic tissue, and that tissue architecture is trabecular with greater presence of capillary sinusoids.

Molecular Signatures of Placentation and Secretion Uncovered in Poeciliopsis Maternal Follicles.

Placentation evolved many times independently in vertebrates. Although the core functions of all placentas are similar, we know less about how this similarity extends to the molecular level. Here, we study Poeciliopsis, a unique genus of live-bearing fish that have independently evolved complex placental structures at least three times. The maternal follicle is a key component of these structures. It envelops yolk-rich eggs and is morphologically simple in lecithotrophic species but has elaborate villous structures in matrotrophic species. Through sequencing, the follicle transcriptome of a matrotrophic, Poeciliopsis retropinna, and lecithotrophic, P. turrubarensis, species we found genes known to be critical for placenta function expressed in both species despite their difference in complexity. Additionally, when we compare the transcriptome of different river populations of P. retropinna, known to vary in maternal provisioning, we find differential expression of secretory genes expressed specifically in the top layer of villi cells in the maternal follicle. This provides some of the first evidence that the placental structures of Poeciliopsis function using a secretory mechanism rather than direct contact with maternal circulation. Finally, when we look at the expression of placenta proteins at the maternal-fetal interface of a larger sampling of Poeciliopsis species, we find expression of key maternal and fetal placenta proteins in their cognate tissue types of all species, but follicle expression of prolactin is restricted to only matrotrophic species. Taken together, we suggest that all Poeciliopsis follicles are poised for placenta function but require expression of key genes to form secretory villi.

Beyond Pairwise Interactions: Multispecies Character Displacement in Mexican Freshwater Fish Communities.

Competition has long been recognized as a central force in shaping evolution, particularly through character displacement. Yet research on character displacement is biased, as it has focused almost exclusively on pairs of interacting species while ignoring multispecies interactions. Communities are seldom so simple that only pairs of species interact, and it is not clear whether inferences from pairwise interactions are sufficient to explain patterns of phenotypes in nature. Here, we test for character displacement in a natural system of freshwater fishes in western Mexico that contains up to four congeneric species of the genus Poeciliopsis. We analyzed body shape differences between populations with different numbers of competitors while accounting for confounding environmental variables. Surprisingly, we found evidence for convergent character displacement in populations of P. prolifica, P. viriosa, and P. latidens. We also found that the convergence in body shape was not consistently in the same direction, meaning that when three or more competitors co-occurred, we did not find more extreme body shapes compared with when there were only two competitors. Instead, when three or more competitors co-occurred, body shape was intermediate between the shape found with a pair of species and the shape found with no competitor present. This intermediate shape suggests that evolution in multispecies communities likely occurs in response to several competitors rather than to simple pairwise interactions. Overall, our results suggest that competition among multiple species is more complex than simple pairwise competitive interactions.

DNA barcoding and species delimitation of the Old World tooth-carps, family Aphaniidae Hoedeman, 1949 (Teleostei: Cyprinodontiformes).

The fishes, which have currently named Aphanius Nardo, 1827 are the relict of the ancient ichthyofauna of the Tethys Sea. For a long time since 1827, the genus name has been subjected to revision by several researchers using mainly morphological features. Until recently, no comprehensive single- or multi-locus DNA barcoding study has been conducted on whole members of the family Aphaniidae. In the present study, by applying four conceptually different molecular species delimitation methods, including one distance-based method, one network-based and two topology-based methods, we examined a single-locus DNA barcode library (COI) diversity for the 268 sequences within the family Aphaniidae from the Old World (57 sequences are new in the present study and 211 sequences were retrieved from NCBI database). The molecular analyses revealed a clearer picture of intra-family relationships and allowed us to clarify the generic names, and also describe a new genus for the family Aphaniidae. Results supported distinction of three major clades related to three genera within this family: i) the first clade includes the A. mento group which are placed in a new genus, Paraphanius gen. nov., found in the Orontes (= Asi) and Tigris-Euphrates River drainage, the Levant in coastal waters and the Dead Sea basin, western Jordan, and in southern Turkey in the Mediterranean basins as well as in central Turkey. This clade positioned at the base of the phylogenetic tree, (ii) the second clade contains the A. dispar-like brackish water tooth-carps which are transferred to the genus Aphaniops Hoedeman, 1951 (type species, Lebias dispar), distributed in the coastal waters around the Red Sea and the Persian Gulf basins; and (iii) the third clade, the genus Aphanius Nardo, 1827 (type species Aphanius nanus = A. fasciatus) contains all the inland and inland-related tooth-carps, which are mainly distributed in the inland waters in Turkey and Iran and also in the inland-related drainages around the Mediterranean basin.

A new livebearing fish of the genus Limia (Cyprinodontiformes: Poeciliidae) from Lake Miragoane, Haiti.

Limia islai, a new species of livebearing fish, is described from Lake Miragoane in south-western Haiti on Hispaniola. The new species has a conspicuous barred pattern consisting of several (4-12) black bars along the body, ray 4p serrae of the gonopodium in males with 10 segments and origin of dorsal fin in females slightly behind the origin of the anal fin. Although the new species colour pattern is similar to that of the humpbacked limia Limia nigrofasciata Regan 1913, L. islai sp. nov. has exclusive morphological features, such as slender body, lack of hump anterior to dorsal fin in males and presence of specific features in the gonopodial suspensory, which allow an unambiguous diagnosis from L. nigrofasciata. L. islai further differs from L. nigrofasciata in reproductive behaviour since L. islai males rely on sneak copulations and gonopodial thrusting, whereas L. nigrofasciata display an elaborate courtship behaviour. The new species is also genetically distinct in both nuclear (Rh, Myh6) and mitochondrial (12S, ND2, D-loop, Cytb) genes from other species in the genus showing reciprocal monophyly. The description of this new Limia species from Lake Miragoane confirms this lake as an important centre of endemism for the genus, with a total of eight endemic species described so far.

Are Extreme Anatomical Modifications Required for Fish to Move Effectively on Land? Comparative Anatomy of the Posterior Axial Skeleton in the Cyprinodontiformes.

Many teleost fishes with no apparent modifications for life on land are able to produce effective terrestrial locomotor behaviors, including a ballistic behavior called the "tail-flip" jump. Cyprinodontiformes (killifishes, Teleostei: Atherinomorpha) that live at the water's edge vary in morphology and inclination to emerge onto land. Do fish with an amphibious predisposition have extensive modification of the propulsive region of the body when compared to fully aquatic relatives? We quantified body shape and anatomy of the caudal peduncle and tail (the propulsive organ on land and in water) in 11 cyprinodontiform species and two outgroup taxa (Atherinomorpha). We hypothesized that amphibious species would have longer, "shallower" bodies (larger body fineness ratios), deeper (proportionally larger) caudal peduncles, and more robust bones in the tail fin (larger ossified area of the hypural/epural bones) to facilitate locomotor movements on land. We found no evidence of convergence in body shape or skeletal anatomy among species known to make voluntary sojourns onto land. In fact, deep-bodied species, shallow-bodied species, and species with intermediate morphologies all are able to emerge from the water and move on land. It is possible that there are as-yet-undocumented subtle soft-tissue (muscle, tendon, and ligament) modifications that enhance terrestrial locomotor performance in species known to spend large periods of time on land. However, it is also possible that extreme anatomical changes are not required for aquatic cyprinodontiform species to produce effective locomotor movements when they emerge out of the water and move across the land. Anat Rec, 2019. © 2019 American Association for Anatomy.

The effects of commonly used anaesthetics on colour measurements across body regions in the poeciliid fish, Girardinus metallicus.

The effects of common anaesthetics on the hue, saturation and brightness measurements of the poeciliid fish Girardinus metallicus were investigated in two experiments. For both experiments the coloration of four body regions was measured from digital images of the same males obtained under three conditions: (1) control (in a water-filled chamber); (2) anaesthetised with MS-222; and (3) anaesthetised with eugenol (clove oil). In experiment 1 anaesthetised fish were photographed out of water. In experiment 2 all photographs were taken in a water-filled chamber. Anaesthetics altered coloration in both experiments. In the more methodologically consistent experiment 2 we found significantly different hue, increased saturation and decreased brightness in anaesthetic v. control conditions, consistent with darkening caused by the anaesthetics. The body regions differed in coloration consistent with countershading but did not differentially change in response to anaesthesia. These findings suggest that photographing fish in a water-filled chamber without anaesthetic is preferable for obtaining digital images for colour analysis and that multiple body regions of fish should be measured when assessing coloration patterns meaningful in behavioural contexts, to account for the gradients caused by countershading. We are encouraged that some researchers employ such methods already and caution against using anaesthetics except when absolutely necessary for immobilisation.