Deep-bodied Species Research Articles

A new deep-bodied species of Antigonia (Teleostei, Antigoniidae) from the Andaman Sea (northeastern Indian Ocean).

A new species of boarfish, Antigonia emanuela, is described from two specimens collected in the Andaman Sea off the coast of Myanmar during bottom trawl surveys conducted by the R/V Dr Fridtjof Nansen in 2015 and 2018. It is unique within the genus in the combination of the deeply rhomboid body (1.1-1.2 times deeper than long), nine dorsal-fin spines, premaxilla strongly bent in middle, scales with deep apical crest armed with numerous spinules, soft dorsal, anal and caudal fins bright-yellow in life. Two other Antigonia species captured during these surveys are A. indica and A. ovalis, the latter species being a first report for the Andaman Sea.

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.

Habitat Alterations and Fish Assemblage Structure in the Missouri River System, USA: is Ecomorphology an Explanation?

Sampling was conducted over a two-year period to determine if fish body morphology (as indicated by the Fineness Ratio (FR), an index of fish streamlining) and habitat alterations can interact to influence fish assemblage structure in three human-altered segments of the Missouri River. It was hypothesized that segments with more variability in depths, velocities, and substrates would have a fish assemblage characterized by more diversity in streamlining. Conversely, it was hypothesized that fish assemblages in more altered river segments would exhibit less diversity in streamlining, i.e., less variability from optimal values because of more uniform habitat conditions. In faster more uniform habitats, fewer variations from optimal streamlining would be adaptive. The three flowing segments studied encompassed the mouth of the Yellowstone River (YSS; moderately altered), the area below Garrison Dam, North Dakota (GOS; below dam-highly altered) and the segment from St. Joseph to Kansas City, Missouri (SKS; channelized-highly altered). The three segments exhibited greatly different fish assemblages. Small native minnows (Cyprinidae), particularly flathead chub (Platygobio gracilis), and deep-bodied suckers, such as bigmouth buffalo (Ictiobus cyprinellus), were common in the YSS. The GOS was dominated by the dorsally compressed fathead minnow (Pimephales promelas). Emerald shiner (Notropis atherinoides) and gizzard shad (Dorosoma cepedianum) dominated the fish assemblage in the SKS. When FR and physical conditions were analyzed across all habitat types, the least altered, more natural YSS was characterized by higher diversity of FR and higher variability in velocity and depth than the most altered SKS. Results for the GOS were more difficult to interpret. The fish assemblage in the highly channelized SKS exhibited the weighted mean FR that was closest to the optimal 4.5 value (FR = 4.42) with the smallest deviation from optimal (0.08). The highest mean and highest maximum current velocity use in the three segments was found for species such as sicklefin chub (Macrhybopsis meeki), sturgeon chub (Macrhybopsis gelida), and blue sucker (Cycleptus elongatus), that were nearly optimally streamlined. Deep-bodied species with FRs typically below 3.5, such as Ictiobus spp., river carpsucker (Carpiodes carpio), and centrarchids, tended to exhibit the lowest mean and lowest maximum current velocity use in the three segments . Results of this study can be useful in helping to understand fish assemblage composition in relation to river alterations in various geographical areas. Because the fineness ratio is only a simple index of streamlining and does not account for other anatomical (e.g., fins) and behavioral aspects of fishes, more studies on different species are needed to develop a stronger understanding of how fish cope with the current. Because of the complexity of interacting natural and human-caused factors affecting these highly altered large river systems, fish streamlining is only one of several factors that may influence the observed fish community structure of a large river system. Streamlining deserves consideration, however, for inclusion in more complex models explaining and predicting fish community structure in large rivers.

Passive mechanical models of fish caudal fins: effects of shape and stiffness on self-propulsion

Fishes are found in a great variety of body forms with tail shapes that vary from forked tuna-like tails to the square-shaped tails found in some deep-bodied species. Hydrodynamic theory suggests that a fish’s body and tail shape affects undulatory swimming performance. For example, a narrow caudal peduncle is believed to reduce drag, and a tuna-like tail to increase thrust. Despite the prevalence of these assertions, there is no experimental verification of the hydrodynamic mechanisms that may confer advantages on specific forms. Here, we use a mechanically-actuated flapping foil model to study how two aspects of shape, caudal peduncle depth and presence or absence of a forked caudal fin, may affect different aspects of swimming performance. Four different foil shapes were each made of plastics of three different flexural stiffnesses, permitting us to study how shape might interact with stiffness to produce swimming performance. For each foil, we measured the self-propelling swimming speed. In addition, we measured the forces, torques, cost of transport and power coefficient of each foil swimming at its self-propelling speed. There was no single ‘optimal’ foil exhibiting the highest performance in all metrics, and for almost all measures of swimming performance, foil shape and flexural stiffness interacted in complicated ways. Particle image velocimetry of several foils suggested that stiffness might affect the relative phasing of the body trailing edge and the caudal fin leading edge, changing the flow incident to the tail, and affecting hydrodynamics of the entire foil. The results of this study of a simplified model of fish body and tail morphology suggest that considerable caution should be used when inferring a swimming performance advantage from body and tail shape alone.

A morphospace for reef fishes: elongation is the dominant axis of body shape evolution.

Tropical reef fishes are widely regarded as being perhaps the most morphologically diverse vertebrate assemblage on earth, yet much remains to be discovered about the scope and patterns of this diversity. We created a morphospace of 2,939 species spanning 56 families of tropical Indo-Pacific reef fishes and established the primary axes of body shape variation, the phylogenetic consistency of these patterns, and whether dominant patterns of shape change can be accomplished by diverse underlying changes. Principal component analysis showed a major axis of shape variation that contrasts deep-bodied species with slender, elongate forms. Furthermore, using custom methods to compare the elongation vector (axis that maximizes elongation deformation) and the main vector of shape variation (first principal component) for each family in the morphospace, we showed that two thirds of the families diversify along an axis of body elongation. Finally, a comparative analysis using a principal coordinate analysis based on the angles among first principal component vectors of each family shape showed that families accomplish changes in elongation with a wide range of underlying modifications. Some groups such as Pomacentridae and Lethrinidae undergo decreases in body depth with proportional increases in all body regions, while other families show disproportionate changes in the length of the head (e.g., Labridae), the trunk or caudal region in all combinations (e.g., Pempheridae and Pinguipedidae). In conclusion, we found that evolutionary changes in body shape along an axis of elongation dominates diversification in reef fishes. Changes in shape on this axis are thought to have immediate implications for swimming performance, defense from gape limited predators, suction feeding performance and access to some highly specialized habitats. The morphological modifications that underlie changes in elongation are highly diverse, suggesting a role for a range of developmental processes and functional consequences.

Description of Hylopanchax paucisquamatus (Cyprinodontiformes: Poeciliidae), a new lampeye species from the Odzala-Kokoua National Park, Republic of Congo

A new deep-bodied Hylopanchax species is described from the northwestern Congo basin. Hylopanchax paucisquamatus, new species, was collected in the Odzala-Kokoua National Park in the Likouala River drainage of the Republic of Congo. It differs from its congeners, including the deep-bodied H. leki and H. ndeko, by a unique combination of morphological characters, including low number of mid-longitudinal and transverse scales, number of dorsal-fin rays, and position of dorsal-fin origin in relation to anal-fin. It is the only deep-bodied species currently known outside the Kasaï River drainage.

Body shape evolution of Chromis and Azurina species (Percifomes, Pomacentridae) of the eastern Pacific

Chromis is a circumglobal tropical and temperate genus with over 84 species of damselfishes. Studies based in osteological and molecular data have cited the relationship between Azurina and Chromis in the eastern Pacific. The main objectives of the study are: (1) to characterize size and shape in all Chromis and Azurina species of the eastern Pacific, (2) explore the phylogenetic signal of external morphology, and (3) present a hypothesis of the diversification process of this group. According to the results, there is no significant relationship between size and shape. The variation in body shape among all species is related to the height of the trunk, position of the snout and eye, and length of the caudal peduncle. The main morphologic variation between Azurina and Chromis is the degree of elongation of the body. Both Azurina species are closely related to C. punctipinnis and C. atrilobata. The morphological pattern of Azurina integrated it into Chromis. The phylogenetic pattern found by geometric morphometric analyses presented a high similarity with previous results based on molecular data. Phylogeny recovered two main clades, slender-bodied and deep-bodied species. This pattern of morphometric variation is closely related to exploitation of two different reef environments.

A new species of Nanochromis (Teleostei: Cichlidae) from Lake Mai Ndombe, central Congo Basin, Democratic Republic of Congo

Nanochromis wickleri, a new cichlid species from Lake Mai Ndombe in the central Congo basin, is described. The large, deep-bodied species differs from all congeners in the possession of an elevated soft dorsal fin ray count (10–11 vs. 5–8) and by the presence, in adults, of strongly produced membranous fin lappets on the second and third dorsal fin spines. Pending comprehensive phylogenetic analysis Nanochromis wickleri is tentatively placed within a morphologically diagnosable subclade of Nanochromis, herein named the “nudiceps group”.

Three new Parananochromis species (Teleostei, Cichlidae) from Gabon and Cameroon, Central Africa

Parananochromis axelrodi, P. brevirostris and P. ornatus, three new cichlid species, are described from Gabon and southern Cameroon. Parananochromis axelrodi is a deep-bodied species differing from congeners in a combination of morphometric and meristic characters. Parananochromis brevirostris and P. ornatus are distinguished by the presence of four elements in the infraorbital series versus five elements in congeners. Parananochromis brevirostris differs from P. ornatus in lacking chest squamation and in the presence of a weakly-developed pharyngeal pad (versus well-developed pad and scaled chest in P. ornatus).

Impact of piscivorous fish introductions on fish species richness of small lakes in Gatineau Park, Québec

:Fish communities of small lakes (< 61 ha) of Gatineau Park (Québec, Canada) which, originally lacked piscivores, were studied to assess the impact of piscivorous fish introductions over the past 85 years. Total species richness was not significantly different between lakes with (n = 15) or without (n = 22) introduced piscivores. However, small-bodied species richness (mainly cyprinid) was significantly lower (nearly half) in lakes with piscivores. Lakes with piscivores showed communities dominated by large or deep-bodied species (mainly Catostomidae, Percidae and Centrarchidae) whereas lakes without piscivores contained mostly small-bodied species (mainly Cyprinidae, Umbridae and Gasterosteidae). Few relationships were found between morphometric variables and fish richness variables. Total fish species richness was found to be a positive function of area and a negative function of elevation when all lakes (n = 45) of the park are considered. For the small lakes of the park, small-bodied species (and cyprinid species) richness in lakes without introduced piscivores was inversely related to the elevation of the lake. Such a relationship was not observed for small lakes with introduced piscivores, possibly because of the disruptive effect of piscivores on small-bodied species number. These results suggest that piscivory by the introduced species is probably responsible for the local extinction of many small-bodied species. Long-lived large-bodied and deep-bodied species (often with spines) are better able to withstand intense predation pressure due to their large size and the dissuasive effects of spines on fins. Because five native small-bodied species were found only in lakes lacking piscivores, it is predicted that their local extinction would occur if introduced piscivores establish populations in these lakes. Thus, small piscivore-free lakes with high small-bodied fish species diversity should rank high on the conservation priority lists of north temperate parks in order to maintain native fish biodiversity.

Genetic distances among fishes of the genus Siganus (Siganidae) from the Western Pacific Ocean

Frequencies of electromorphs encoded by 14 polymorphic loci were used to estimate genetic distances among samples of the rabbitfishes Siganus argenteus, S. doliatus, S. fuscescens, S. guttatus, S. javus, S. punctatus, S. randalli, S. spinus, S. vermiculatus, and S. (Lo) vulpinus. Samples of the surgeonfish Naso lituratus (Acanthuridae) were included in the electrophoretic survey for the purpose of outgroup comparison. A matrix of genetic-distance estimates was used for construction of dendrograms by neighbor-joining, complete-linkage and single-linkage procedures, and the unweighted pair-group method of arithmetic averages (UPGMA). Cluster analysis revealed interspecific relationships that are concordant with several predictions intimated in the most recent taxonomic revision of this assemblage of fishes. S. randalli and S. vermiculatus, the pair postulated to be sibling species on the basis of strikingly similar external morphology, were found to exhibit the lowest levels of genetic divergence relative to all other pairs of study species. S. randalli, S. guttatus, and S. vermiculatus comprised one of three clusters discerned in all resultant topologies (i.e., “ball clusters”). S. argenteus, S. fuscescens, and S. spinus, three fusiform-bodied species, formed a second ball cluster that was clearly separable from the remainder of the siganids studied (which are all relatively deep-bodied). A third ball cluster contained S. punctatus and S. vulpinus: S. doliatus was depicted as being allied with S. punctatus and S. vulpinus in the neighbor-joining and complete-linkage topologies but not in topologies generated by UPGMA and single linkage. It is noteworthy that S. punctatus, S. vulpinus, and S. doliatus are the only three species included in the present study which purportedly school when young but form pair-bonds as adults. In all topologies, S. javus occupied branches stemming from furcation points between fusiform-bodied and deep-bodied species. Of all the siganids studied, S. argenteus was found to be least divergent genetically from N. lituratus. S. argenteus is the only siganid known to spawn pelagic eggs and undergo a specialized pelagic stage (features typical within the Acanthuridae). Hence, genetic relationships within the Siganidae and among the Siganidae and a representative acanthurid coincide with a host of predictions stemming from morphologic and life-history studies of the Acanthuroidei.

Review of the Deep-Bodied Species of Chromis (Pisces: Pomacentridae) from the Eastern Pacific, with Descriptions of Three New Species

Review of the Deep-Bodied Species of Chromis (Pisces: Pomacentridae) from the Eastern Pacific, with Descriptions of Three New Species

I.—On two deep-bodied species of the Clupeoid genus Diplomystus

I.—<i>On two deep-bodied species of the Clupeoid genus</i> Diplomystus