Galaxias fossils from Miocene lake deposits, Otago, New Zealand: The earliest records of the Southern Hemisphere family Galaxiidae (Teleostei)

The distinctive caudal-fin skeleton of gadiforms has puzzled scientists for a long time, because of its many differences in comparison to other teleosts. Contradicting hypotheses interpreted this structure as (i) a highly derived teleostean caudal fin, (ii) a new formation with parts from the caudal, dorsal and anal fins, a so called pseudocaudal, or (iii) a complete evolutionary novelty, a so called neocaudal. To shed light on to this issue, the caudal-fin ontogeny of Lota lota was studied in detail. It differs from the development in non-gadiform teleostean taxa, e.g. by absence of a distinct and early notochord flexion. However, there are also many similarities with other teleosts, e.g. the caudal fin develops before the dorsal and anal fins. Furthermore, the morphology of adult caudal fins of all major gadiform families were studied and reviewed. Our results, in combination with the latest molecular phylogenies, allowed us to discuss the evolution of the gadiform caudal fin and resolve the origin of this highly debated character complex. Although their caudal-fin skeleton shows several derived apomorphies, the gadiform caudal fin is homologous to the caudal fins of other teleosts, without principal inclusion of dorsal- or anal-fin elements.

Recent studies have shown that by utilizing the interactions among median fins (the dorsal, anal, and caudal fins), fishes can achieve higher propulsion performance at the caudal fin. This work aims at a systematic study of the effects of dorsal/anal fin shape and flapping phase on the hydrodynamic performance due to median-fin interactions (MFI) in underwater propulsion using a three-dimensional bluegill sunfish model. Flow simulations were conducted on stationary Cartesian grids using an immersed-boundary-method-based incompressible Navier-Stokes flow solver. The results showed that, due to the collision between the posterior body vortices (PBVs) and caudal fin leading edge vortices (LEVs), the latter is strengthened. As a result, the thrust and efficiency of the caudal fin are improved simultaneously, by 25.6% and 29.2%, respectively. Increases in the dorsal/anal fin area result in stronger caudal fin LEVs, and thus further caudal fin performance enhancement. On the other hand, changing the dorsal/anal fin flapping phase affects the collision time between the PBVs and the LEVs, and results in caudal fin performance changes. Phase-leading dorsal and anal fins are found to improve caudal fin efficiency, whereas phase-lag dorsal and anal fins maintain caudal fin thrust at a higher level. Compared to trunk-synchronized dorsal and anal fins, 60° phase-leading dorsal and anal fins increase the propulsive efficiency of the caudal fin from 77.9% to 90.1%. In addition, it is found that the presence of the dorsal and anal fins greatly reduces drag on the fish body by preventing the PBVs from crossing the body midline and debilitating interactions between the left- and right-stroke PBVs. Results of this work improve our understanding of MFI in fishlike swimming and demonstrate the benefits of optimal MFI for the design of high-performance bioinspired underwater vehicles.

Summary The present study was undertaken to establish the normal, healthy features of morphological structures at various developmental stages as achieved under well-defined environmental culture conditions (temperature between 16 and 21°C, salinity 36 ppt, pH around 7.6, and oxygen saturation over 95%) common in aquaculture of the species. The pectoral fin supports began to develop at 2.90 mm total length (TL), followed by those of dorsal fins at 5.5 mm TL, caudal fins at 5.6 mm TL, pelvic fins at 5.9 mm TL and anal fins at 6.0 mm TL. The pelvic fins appeared fully at 7.4 mm TL. Development of dorsal lepidotrichia was first observed at 6.9 mm TL, attaining their final number at 7.6 mm TL. The dorsal spines first appeared at 6.5 mm TL and were complete at 7.4 mm TL. The anal lepidotrichia appeared during the development phase from 6.8 to 8.6 mm TL. At 5.6 mm TL, the upward flexion of the urostyle was initiated. The caudal lepidotrichia formed within the primordial fin at 5.6 mm TL and reached the final count at 7.4 mm TL. The caudal dermatotrichia first appeared at 7.3 mm TL and all forms were observed by 15.5 mm TL. The development pattern of fin supports found in Pagrus pagrus is quite similar to that described for other Sparid species.

Multi-fin kinematics and hydrodynamics in pufferfish steady swimming

Color performance of false clownfish, Amphiprion ocellaris Cuvier, was examined under three levels of light intensity (20–50 , 600–850 , and 2700–3500 lx) for 5 wk. The experiment was conducted in nine rectangular glass aquaria (25 × 25 × 20 cm) with three replicates. Each aquarium was stocked with 36 fish, and 3 fish were randomly sampled from each aquarium every other week. Digital images were taken weekly on each individual fish after it was anesthetized in MS‐222. The color performance in hue, saturation, and brightness was quantified using image analysis. In addition to the whole‐body analysis, each fish image was divided into ventral and dorsal parts to assess the body position‐dependent effect. Furthermore, color differences between dorsal fin, anal fin, ventral fin, and caudal fin were also quantified. The whole body was brighter at low light than at medium or at high light intensity. Irrespective of light intensity, the dorsal side was more orange but less bright than the ventral side. Brighter light strengthened overall orange color on fish fins. The dorsal fin and ventral fins appeared more orange than the anal and caudal fins regardless of light intensity and exposure duration. Similar to body color, low light also led to brighter fins, especially for caudal and dorsal fins. Our results indicate that ambient light could regulate fish color performance but could not change the pigment dominance by β‐carotene. Light intensity is unlikely to change the contrast between dorsal and ventral sides, but dim light tends to make fish body brighter, and bright light strengthens orange color on fins.

The osteological development of the vertebral column and fins in shi drum Umbrina cirrosa was studied in order to improve knowledge for its introduction in Mediterranean aquaculture. The osteological development was studied in 171 individuals, of total length (LT ) from 2·7 to 30·2 mm that were reared under the mesocosm technique. Vertebral ontogeny starts at 3·4 and 4·0 mm LT , with the formation of the first cartilaginous neural and haemal arches, and spines, respectively, and is completed with the full attainment of epicentrals (12·5 mm LT ). The formation of vertebral centra occurs between 4·1 and 7·4 mm LT . Pectoral supports are the first fin elements to develop (3·0 mm LT ), followed by those of the caudal fin (3·8 mm LT ), pelvic fin (3·9 mm LT ) and finally by those of the dorsal and anal fins (4·5 mm LT ). The caudal fin is the first to develop fin rays and attain the full count of principal fin rays (4·5-6·8 mm LT ), but the last to be fully completed with the formation of procurrent fin rays (6·9-17·5 mm LT ). The next fins starting to present rays are the dorsal (5·3 mm LT ) and the pectoral fins (5·6 mm LT ), while the anal and pelvic fins are the last (5·7 mm LT ). Following the caudal principal fin rays (6·8 mm LT ), the dorsal, anal (6·9 mm LT ), pelvic (7·4 mm LT ) and pectoral fins (9·8 mm LT ) are the next with fully completed ray counts. Aggregation of qualitative changes, such as the appearance of cartilages, the beginning and the complement of the ossification process and the full complement of elements in U. cirrosa were measured as cumulative frequency counts. These measurements reveal three ontogenetic intervals: one very developmentally active period during early life stages (from 3 to 5·9 mm LT ), a second slower developmental period (from 6·0 to 8·9 mm LT ) and finally a period of ontogeny more focused on structure refinement up to metamorphosis and settlement (>9·0 mm LT ).

Larvae of common wolYsh (Anarhichas lupus L.) obtained from eggs incubated at a constant temperature of 7.0)C had mean numbers of rays in the dorsal, anal, and caudal fins of 74.5, 46.4, and 23.8 respectively; those incubated at 11.0)C had 53.8, 25.7, and 25.2 rays, respectively. Several skeletal abnormalities, including fusion of parts and abnormal structure of neural arches in the pre-urostyle area, accompanied the reduction in numbers of dorsal and anal fin rays at 11)C. To test which period of embryonic development was critical for determining the final numbers of unpaired fin rays and skeletal abnormalities, the eggs were transferred from 7) Ct o 11 )C and back at diVerent stages. Determination of the final numbers of rays in the dorsal and anal fins and most of skeletal abnormalities occurred mainly between 50% vascularization of the yolk sac and the beginning of formation of rays in the caudal and pectoral fins. The final number of caudal fin rays was determined between the latter stage and formation of rays in the dorsal and anal fins. To reduce the egg incubation period and still obtain larvae without skeletal abnormalities, a temperature regime during embryonic development is suggested. ? 1996 International Council for the Exploration of the Sea

Functional morphology and hydrodynamics of backward swimming in bluegill sunfish, Lepomis macrochirus

Aphanius marassantensis, new species, is described from the Kızılırmak River drainage in northern Anatolia based on colouration, meristic and morphometric characters, and the mtDNA COI barcode region. It is distinguished from other Anatolian Aphanius by one or several of the following characters: a stout body shape (BD/SL 28.2-39.6%), complete scale cover, and 25-28 scales along the lateral line. Males have 8-13 dark-brown lateral bars, of which the antepenultimate bar anterior to the caudal-fin base is 0.9-1.8 times wider than the anterior white interspace, 2-3 vertical rows of spots on the caudal fin, a black dorsal fin, sometimes with a narrow whitish-grey base, a white anal fin with 1-3 rows of black spots, in some individuals with a black margin, and hyaline pelvic fins. Females do not have vertical rows of dark-brown spots on caudal or anal fins, but numerous dark-brown spots on the flanks, arranged in 1-3 lateral rows behind a vertical from the dorsal-fin base. Their dorsal fin is hyaline with tiny dark-brown spots on rays and membranes; pectoral fins, caudal and anal fins are hyaline, and one prominent large dark-brown blotch is situated in mid-lateral position on the hypural plate. The new species is also distinguished by 11 fixed, diagnostic nucleotide substitutions in the mtDNA COI barcode region. The description of this new species, which brings the number of Anatolian Aphanius species to 12, underlines the character of Anatolia as a region of extraordinarily high biodiversity.

Fin development in stream- and hatchery-reared Atlantic salmon

Austrofundulus dolichopterus is described as a new species of annual cyprinodont and was recently discovered in temporary ponds in the states of Guarico, Cojedes, and Apure, Venezuela. It is placed in Austrofundulus on the basis of caudal fin shape and color pattern. It differs from other species of this genus by lacking caudal fin scales, in having elongate streamers on the caudal fin, elongate dorsal and anal fins, and a dorsal fin slightly in advance of the anal fin. In an attempt to determine its closest relatives, characters defining the South American cyprinodont genus Cynolebias and its allies were reevaluated. It was found that Cynolebias, Pterolebias, Cynopoecilus, Rachovia, Austrofundulus, Leptolebias, and Simpsonichthys cannot be separated on the basis of characters currently in use such as the relative positions of the dorsal and anal fins, caudal peduncle and fin shape, distribution of scales on the caudal fin, sexual dimorphism in the number of dorsal and anal fin rays, and variations in the presence or the juxtaposition of the two pelvic fins. Despite these findings, we do not believe it wise to synonymize any of these genera until reevaluation of all neotropical cyprinodont genera can be accomplished. When sufficient material becomes available for a more complete study, some of the genera here tentatively recognized may prove to be valid on the basis of other characters. For example, northern South American annual fishes tend to have pointed upper and lower caudal fin lobes and have scales distributed over the caudal fin. Southern species have a rounded or simple pointed caudal fin and lack scales on the caudal fin. Further study may show these differences to be of generic significance.

Fishes have an enormous diversity of body shapes and fin morphologies. From a hydrodynamic standpoint, the functional significance of this diversity is poorly understood, largely because the three-dimensional flow around swimming fish is almost completely unknown. Fully three-dimensional volumetric flow measurements are not currently feasible, but measurements in multiple transverse planes along the body can illuminate many of the important flow features. In this study, I analyze flow in the transverse plane at a range of positions around bluegill sunfish Lepomis macrochirus, from the trailing edges of the dorsal and anal fins to the near wake. Simultaneous particle image velocimetry and kinematic measurements were performed during swimming at 1.2 body lengths s(-1) to describe the streamwise vortex structure, to quantify the contributions of each fin to the vortex wake, and to assess the importance of three-dimensional flow effects in swimming. Sunfish produce streamwise vortices from at least eight distinct places, including both the dorsal and ventral margins of the soft dorsal and anal fins, and the tips and central notched region of the caudal fin. I propose a three-dimensional structure of the vortex wake in which these vortices from the caudal notch are elongated by the dorso-ventral cupping motion of the tail, producing a structure like a hairpin vortex in the caudal fin vortex ring. Vortices from the dorsal and anal fin persist into the wake, probably linking up with the caudal fin vortices. These dorsal and anal fin vortices do not differ significantly in circulation from the two caudal fin tip vortices. Because the circulations are equal and the length of the trailing edge of the caudal fin is approximately equal to the combined trailing edge length of the dorsal and anal fins, I argue that the two anterior median fins produce a total force that is comparable to that of the caudal fin. To provide additional detail on how different positions contribute to total force along the posterior body, the change in vortex circulation as flow passes down the body is also analyzed. The posterior half of the caudal fin and the dorsal and anal fins add vortex circulation to the flow, but circulation appears to decrease around the peduncle and anterior caudal fin. Kinematic measurements indicate that the tail is angled correctly to enhance thrust through this interaction. Finally, the degree to which the caudal fin acts like a idealized two-dimensional plate is examined: approximately 25% of the flow near the tail is accelerated up and down, rather than laterally, producing wasted momentum, a loss not present in ideal two-dimensional theories.

Undichna, the swimming trace of fish, was recovered from the middle member of the Mauch Chunk Formation in eastern Pennsylvania in strata of Late Mississippian (Visean) age. These traces represent the only evidence of fish known from the Mauch Chunk Formation and the Carboniferous of Eastern Pennsylvania. The Mauch Chunk Formation in the study area is characterized by an ephemeral fluvial depositional environment that yields a diverse invertebrate ichnoassemblage of the Scoyenia ichnofacies and a tetrapod footprint assemblage dominated by the tracks of temnospondyl amphibians. The Undichna specimens are preserved on fine-grained, mudstone-draped, rippled sandstone. Two specimens, assigned to U. Britannica, consist of pairs of well-defined, narrowly incised, sinusoidal wave traces that are out-of-phase. Two specimens, assigned to U. quina, consist of two pairs of in-phase sinusoidal waves intersected by an additional single wave with a greater amplitude. Two specimens, each composed of a single wave, are assigned to U. unisulca. The slabs of rock with the Undichna traces also preserve tetrapod undertracks assigned to Batrachichnus, Matthewichnus, and Hylopus. This trace fossil association indicates the presence of small fish, some with caudal and/or anal fins and some with pectoral, pelvic, and anal and/or caudal fins, that touched the sediment during periods of intermittent flooding of subaerial surfaces walked upon by early tetrapods. Examples of Undichna from Mississippian or older deposits, especially from a fluvial paleoenvironment, are rare; few have been reported from the Devonian and the Lower Carboniferous.

The Medaka zic1/zic4 Mutant Provides Molecular Insights into Teleost Caudal Fin Evolution

Sedimentological and palynostratigraphical modeling of sediments penetrated by KW field wells, onshore western Niger Delta Basin, Nigeria