Haemal Arches Research Articles

Myxobolus buckei sp. n. (Myxozoa), a new pathogenic parasite from the spinal column of three cyprinid fishes from the United Kingdom.

Myxobolus buckei sp. n. is described from the spinal column of Leuciscus cephalus (L.), Rutilus rutilus (L.) and Abramis brama (L.) from freshwater rivers in the North of England. The plasmodia develop within the remnants of the embryonic notochord in the intervertebral spaces. The spores are large, measuring (in microm) 14.0 +/- 0.7 x 11.5 +/- 0.6 (mean +/- SD), smooth, round to ellipsoid in valvular view with several sutural edge markings. The polar capsules are pyriform and of equal size, measuring 7.5 +/- 0.5 x 4.2 +/- 0.2 (mean +/- SD), with 11-12 turns of the polar filament arranged perpendicularly to the longitudinal axis of the polar capsule. The parasite has a large intercapsular appendix and large iodinophorous vacuole. The parasite can be differentiated from all known species of Myxobolus Bütschli, 1882 by a combination of the morphological characters defined. Infected fish show marked longitudinal compression of the body compared to uninfected individuals of the same year class, a feature which is pathognomonic for the disease. Histologically, host responses ranged from mild hypertrophy of the zygapophyseal process and expansion of the intervertebral membrane to complete hypertrophy and fusion of the vertebrae. Prominent notochord is present in the intervertebral spaces of infected fish and sporogony of the parasite leads to a vigorous focal inflammatory response involving proliferating fibroblast and osteogenic cells. The parasite causes a radial expansion of the centra and extensive dorsal and ventral outgrowths of the vertebrae leading to compression of the spinal cord and blood vessels running through the neural and haemal spines respectively. The parasite is considered highly pathogenic to juvenile cyprinids.

Notochord segmentation may lay down the pathway for the development of the vertebral bodies in the Atlantic salmon.

This study indicates that the development of the vertebrae in the Atlantic salmon requires the orchestration of two sources of metameric patterning, derived from the notochord and the somite rows, respectively. Before segmentation of the salmon notochord, chordoblasts exhibit a well-defined cell axis that is uniformly aligned with the cranio-caudal axis. The morphology of these cells is characterised by a foot-like basal projection that rests on the notochordal sheath. Notochordal segments are initially formed within the chordoblast layer by metameric change in the axial orientation of groups of chordoblasts. This process results in the formation of circular bands of chordoblasts, with feet perpendicular to the cranio-caudal axis, the original chordoblast orientation. Each vertebra is defined by two such chordoblast bands, at the cranial and caudal borders, respectively. Formation of the chordoblast segments closely precedes formation of the chordacentra, which form as calcified rings within the adjacent notochordal sheath. Sclerotomal osteoblasts then differentiate on the surface of the chordacentra, using them as foundations for further vertebral growth. Thus, the morphogenesis of the rudiments of the vertebral bodies is initiated by a generation of segments within the chordoblast layer. This dual segmentation model for salmon, in which the segmental patterns of the neural and haemal arches are somite-derived, while the vertebral segments seem to be notochord-derived, contrasts with current models for avians and mammals.

Vertebral deformities in cultured red sea bream, Pagrus major , Temminck and Schlegel

Vertebral deformities were investigated in cultured red sea bream, Pagrus major. In the field, deformities in seedlings were categorized and their incidence was calculated. In the laboratory, the symptoms of major vertebral deformities were examined morphologically using radiographs and by making transparent skeletal specimens. The internal structure of deformed vertebrae was examined histologically. The shortened body condition had the highest incidence (0.9–8.3%) of all deformities in the seedlings. In individuals with the shortened body condition, the ratio of trunk and caudal part length to body height was smaller. These fish had skeletal anomalies in the vertebrae, mainly centrum defects (64.3%) or undersized centrums (25.2%). The specimens with centrum defects had a characteristic anomaly in the vertebrae, with plural pairs of neural and haemal spines on a single centrum. This anomaly was frequently observed in the posterior abdominal vertebrae. The internal skeletal structure of such abnormal centrums was basically the same as that of normal centrums. In all the specimens with undersized centrums, both the centrum length and diameter were shorter than normal except for the first and second centrum, and urostyle.

A revision of the Indo-Pacific fish genus Caragobius (Gobiidae: Amblyopinae)

The Indo-West Pacific gobiid genus Caragobius Smith and Seale is revised and defined. Caragobius has been frequently considered a synonym of Brachyamblyopus; however, Caragobius is unique within the Amblyopinae in having: 3–7 (typically 4–6) anal-fin pterygiophores anterior to first hemal spine; fifth hypural absent; and ribs lacking on 3rd precaudal vertebra. Caragobius comprises two species: C. rubristriatus, known from northern Australia, and C. urolepis, known from India, Thailand, Indonesia, the Philippines, Taiwan, Japan, and Fiji. Images of both species are provided. Caragobius is compared to Brachyamblyopus and Trypauchen-Group members.

Gymnoamblyopus novaeguineae, a new genus and species of worm goby from Papua New Guinea (Gobiidae: Amblyopinae)

A new genus and species of worm goby, Gymnoamblyopus novaeguineae, is described on the basis of a single specimen from the Fly River, Papua New Guinea. It differs from all other amblyopine gobies by the following combination of characters: only one anal-fin pterygiophore anterior to first hemal spine; no Y-shaped second anal-fin pterygiophore; no chin barbels; no scales; no raised dermal folds or ridges; pleural ribs short and posteriorly directed; and mouth vertical. This new taxon is figured and a key to the “Taenioides” group of the Amblyopinae is provided.

Matrix Gla protein gene expression and protein accumulation colocalize with cartilage distribution during development of the teleost fish Sparus aurata

Matrix Gla protein (MGP) is a member of the family of extracellular mineral-binding Gla proteins, expressed in several tissues with high accumulation in bone and cartilage. Although the precise molecular mechanism of action of this protein remains unknown, all available evidence indicates that MGP plays a role as an inhibitor of mineralization. We investigated the sites of gene expression and protein accumulation of MGP throughout development of the bony fish Sparus aurata, by in situ hybridization, Northern and RT-PCR Southern hybridization, and immunohistochemistry. The results obtained were compared with the patterns of developmental appearance of cartilaginous and mineralized structures in this species, identified by histological techniques and by detection of mRNA presence and protein accumulation of osteocalcin (Bone Gla protein), a marker for osteoblasts known to accumulate in bone mineralized extracellular matrix. The expression of MGP mRNA was first detected at 2 days posthatching (dph) by Northern analysis, RT-PCR amplification, and in situ hybridization, and thereafter continuously detected at various levels of intensity, until 130 dph. In situ hybridization analysis performed in parallel with immunohistochemistry indicated that until ca. 45 dph, the MGP gene was highly expressed in a number of different tissues including skull, jaw, neural and hemal arches, and heart and the protein accumulated in cartilaginous tissues. At 85 dph, a stage when most skeletal structures are mineralized, MGP gene expression and protein accumulation were restricted to the remaining cartilaginous structures, whereas osteocalcin gene expression and protein accumulation were localized in most mineralized structures. MGP gene expression was also detected in heart and kidney, although in situ hybridization only detected MGP mRNA in heart, located in the arterial bulbus and not in the cardiac muscle. Our results are in agreement with those recently described for MGP localization in adult tissues of another teleost fish, as well as available data from higher vertebrates, strengthening the hypothesis of a conserved function for MGP from teleost fish to human, a period of more than 200 million years of evolution. In addition, Sparus aurata, a marine teleost fish routinely grown in captivity, appears to be a good model to further analyze MGP gene expression and regulation.

A Late Triassic pterosaur from the Northern Calcareous Alps (Tyrol, Austria)

Abstract Disarticulated skeletal remains of an eudimorphodontid pterosaur from the Late Triassic of the Karwendel Mountains in Tyrol, Austria, are described and figured. It is the second record of Triassic pterosaurs from the Northern Calcareous Alps, after previous discoveries in the Southern Calcareous Alps of northern Italy. The fossil material — isolated jaws, bones and fragmentary skeletal parts of one individual — was collected from the Norian Seefeld Beds (also called ‘Bitumenmergel’ or ‘Seefelder Fischschiefer’) near Seefeld in Tyrol. The fossiliferous formation of largely bituminous and calcareous layers originated on top of an extended marine carbonate platform, an equivalent to the nearly contemporaneous limestones and dolomites in the Southern Calcareous Alps, as exposed in Lombardy and Friuli in Italy, that has produced pterosaur fossils since 1973. Based on the biostratigraphic significance of conodont index fossils, the Seefeld Beds can be dated as Late Norian, most likely Sevatian. Sufficiently well-preserved skeletal elements include a jugal, isolated teeth, both mandibular rami with a dentition of uni-, tri- and pentacuspid teeth, cervical, dorsal and caudal vertebrae, ribs, sternum, scapulocoracoids, humerus, first wing phalanx, pelvis and tibia/fibula. There are morphological characters that support a subadult stage of the individual with an estimated wing span of 70–80 cm. The dentition is comparable to Eudimorphodon ranzii Zambelli from the Norian Calcare di Zorzino of Cene near Bergamo, northern Italy. However, some skeletal proportions and osteological features are distinctive from this taxon, as well as from a second species, Eudimorphodon rosenfeldi Dalla Vecchia from the Norian Dolomia di Forni of Friuli, northern Italy. The meaning of these differences in the Seefeld specimen, in particular the relatively long tibia and short wing phalanx 1, is discussed. The caudal zygapophyses and haemal arches are not elongated into the rod-like bony extensions significant for other known rhamphorhynchoid pterosaurs. It appears, however, that all speciments of Eudimorphodon lack elongated caudal zygapophyses. This might be evaluated as a primitive trait for these basal pterosaurs. The typical dentition permits the assignment of the Seefeld pterosaur to the genus Eudimorphodon . The fragmentary state of the skeleton and somewhat different skeletal proportions allow the author only to refer the specimen to Eudimorphodon cf. ranzii Zambelli 1973.

New Corydoradine Catfish (Siluriformes: Callichthyidae) from the Upper Paraná and São Francisco: The Sister Group of Brochis and Most of Corydoras Species

Corydoras difluviatilis, new species, is described from the upper rio Paraná and the upper rio São Francisco, Brazil. The new taxon differs from its congeners by three exclusive features: the posterior pectoral-spine serrations restricted to its proximal half, and the parapophyses of the fourth free vertebra reduced and separated from each other, not fused into a haemal arch. The new species has several plesiomorphic character states relative to the assemblage composed of Brochis and most Corydoras species, such as absence of contact between the supraoccipital and nuchal plate, reduction of the ossified portion of hypobranchial 2, and well-developed mesial expansions of the first and second infraorbitals, indicating its basalmost position within the genus.

Étude de Pseudanogmius maiseyi gen. et sp. nov., poisson marin (Teleostei, Tselfatiiformes) du Crétacé supérieur du Kansas (États-Unis)

The osteology of Pseudanogmius maiseyi gen. and sp. nov., a marine teleost of the Upper Cretaceous of Kansas, is studied. This fish belongs to the order Tselfatiiformes and more particularly to the group with a more or less flat skull roof and with large, quadrangular and joined parietals. Pseudanogmius maiseyi, formerly named Anogmius sp. by Hay (1903), differs from Bananogmius and the other genera known in the order by three autapomorphies: an elongated and very narrow vomer, a peculiar relief of the toothed part of the parasphenoid, and transverse processes on the caudal vertebrae. Within the order, it shows a few evolved characters, such as the loss of the preural 1 hemal arch and of the sixth autogenous hypural and by the shortening of the preural 1 neural spine.

Description and familial allocation of the African fluvial genus Teleogramma to the Cichlidae

The external morphology, osteology, and myology of the African fluvial genus Teleogramma are described, and its familial allocation is discussed. Teleogramma is included in the family Cichlidae by loss of a major structural association between adductor mandibulae sections 2 and w, and by having an insertion of a large ventral division of adductor mandibulae section 2 onto the anguloarticular, expanded head of the fourth epibranchial, transversus dorsalis subdivided into four parts, functionally decoupled premaxillae and maxillae, the stomach's extendible blind pouch, the left-hand exit to the anterior intestine, the first intestinal loop at the left side, two epurals, seven branched rays on each upper and lower caudal fin lobe, free first uroneural from a united element of first preural and ural vertebra, and third preural vertebra fused with its haemal spine. Seven synapomorphies supporting the monophyly of Teleogramma are indicated, including the absence of or very low supraoccipital crest, the presence of a nostril tube, nonextended supraoccipital anteriorly, absence of extensive cartilaginous cap on the anterior border of the second epibranchial, presence of a beaklike projection on the cleithrum, caudal branched slip of epaxialis that inserts onto the upper two or three branched rays on the upper lobe of the caudal fin, and flexor dorsalis superior, which inserts onto the lower four unbranched rays on the upper lobe of the caudal fin.

Taxonomy of the South American genus Pachypops Gill 1861 (Teleostei: Perciformes: Sciaenidae), with the description of a new species

Pachypops is a South American freshwater sciaenid genus characterized by having two anal-fin spines, three mental barbels, an inferior mouth, a swimbladder with a pair of short appendages anteriorly and a pair of longer appendages projected posteriorly, and the haemal spine of the first caudal distinctly expanded. Three valid Pachypops species are recognized herein. Of the six nominal species previously assigned to Pachypops, two are herein recognized as valid (Perca fourcroi and Micropogon trifilis), two are assigned to other sciaenid genera (Pachypops adspersus and Pachypops cevegei) and two are considered junior synonyms (Corvina biloba and Pachypops camposi). A seventh nominal species, Pachyurus nattereri, formerly considered a valid species of Pachyurus, is determined to be a junior synonym of Pachypops fourcroi, and lectotype and paralectotypes are designated for it. Pachypops fourcroi occurs in the Orinoco, Amazonas, Essequibo, Corantijn, and Approuague River basins, and Pachypops trifilis in rivers of Guyana and middle and lower reaches of the Rio Amazonas basin. A third valid species, Pachypops pigmaeus n. sp., is herein described from tributaries of the Rio Amazonas, Brazil.

Vertebral development in the Devonian Sarcopterygian fish Eusthenopteron foordi and the polarity of vertebral evolution in non-amniote tetrapods

ABSTRACT Study of a growth series of twenty-seven specimens from the Upper Devonian of Escuminac Bay, Québec documents a complex pattern of vertebral development in the osteolepiform fish Eusthenopteron foordi. Ossification begins with elements associated with the caudal, anal, and second dorsal fins. Development of the haemal arches, caudal radials, and caudal neural arches continues anteriorly and posteriorly from near the level of the anterior margin of the caudal fin. Trunk neural arches ossify later than the caudal neural arches and as a separate sequence. Trunk intercentra most likely begin ossification posteriorly and continue forward after the ossification of haemal arches is complete. Comparisons of many different patterns of vertebral development within the modern actinopterygians demonstrates that the sequence of development in Eusthenopteron foordi is unique. The diverse patterns of vertebral development observed in fossil and modern fish presumably result from an interplay between the inherent anterior to posterior sequence of development controlled by the Hox genes, and varying selective forces imposed by the physical and biological environment in which the fish develop. Initiation of vertebral development in the caudal region of Eusthenopteron foordi can be attributed to selection for early function of the tail in propulsion. In contrast, vertebral development in Carboniferous amphibians typically proceeds from anterior to posterior. This may reflect development in the still water of ponds and lakes in contrast with the coastal environment inhabited by the hatchlings of Eusthenopteron foordi. The sequences of vertebral development seen in Carboniferous labyrinthodonts and lepospondyls are divergently derived from that observed in Eusthenopteron foordi.

Osteological development of the vertebral column and of the fins in Diplodus sargus (Teleostei: Perciformes: Sparidae)

The osteological development of vertebral column and fins in white sea bream, Diplodus sargus (Linnaeus, 1758) was studied. Vertebral ontogeny started at 5.7 mm total length (TL, post-fixation), with the formation of the first cartilaginous neural and haemal arches, and was completed by the full attainment of dorsal ribs (20.8 mm TL). The formation of vertebral centra occurred between 7.3 and 9.4 mm TL, but was fully completed only after the development of post- and pre-zygapophyses (26.0 mm TL). Pectoral supports were the first fin elements that started to develop (3.8 mm TL), followed by those of the caudal fin (5.2 mm TL), dorsal and anal fins (6.7 mm TL), and then by those of the pelvic fin (9.5 mm TL). The caudal fin of D. sargus was the first to develop fin rays and attain the full count of lepidotrichia (5.6–7.8 mm TL), but the last to attain the full count of dermatotrichia (7.9–16.0 mm TL). The next fins starting to present rays were the pectoral (6.5 mm TL) and the dorsal and anal fins (7.5 mm TL), while the pelvic fins were the last (11.5 mm TL). Following the caudal lepidotrichia (7.8 mm TL), the anal (10.5 mm TL), dorsal (12.0 mm TL), pectoral (11.4 mm TL) and pelvic fins (12.5 mm TL) were the next with fully completed ray counts. Finally, fin meristics were fully developed with the caudal dermatotrichia. The results are discussed in comparison with the fin and vertebral ontogeny of other teleosts.

Walleye pollock Theragra chalcogramma during transformation from the larval to juvenile stage: otolith and osteological development

Walleye pollock [Theragra chalcogramma (Pallas, 1814)] were collected from the Gulf of Alaska from 1991 to 1998 to examine the relationship between otolith and osteological development during transformation from the larval to juvenile life stage. Five stages of otolith development were determined for walleye pollock in conjunction with landmarks in osteological development during juvenile transformation. The first stage of otolith development (12–19 mm SL) is identified by the first accessory growth center (AGC) forming on sagittal otoliths. At this stage, the notochord is undergoing flexion as the teeth, jaws, branchiostegal rays, neural spines, and abdominal vertebral centra are ossifying. The second and third stages of otolith development (19–21 and 21–24 mm SL) are defined by the formation of the anterior, posterior, and dorsal AGCs on the otolith. This occurs during postflexion in conjunction with ossification of the principal caudal-fin rays, haemal spines, and caudal vertebral centra. The fourth stage of otolith development (24–37 mm SL) is defined by the AGCs on the ventral edge of the otolith. By this stage of development, the pelvic-, pectoral-, dorsal-, and anal-fin ray elements have started ossification and the fish has entered the transformation stage. The fifth stage of otolith development (36–48 mm SL) is identified by a completely formed sagittal otolith, which has AGCs that have grown together so that the otolith shape resembles an adult otolith, the ossification of all vertebrae and fin rays is complete, and the fish is a juvenile. By estimating what length a fish was, based solely on otolith development, would prove helpful for those who wish to reconstruct length frequencies of walleye pollock from otoliths of fish that have been damaged due to gear and/or poor handling during the preservation process.

Vertebral column and associated elements in dipnoans and comparison with other fishes: development and homology.

A vertebral column consisting of a persistent notochord and ossified arcocentra is the primitive condition for Gnathostomata; it still persists in primitive actinopterygians and sarcopterygians. Advanced actinopterygians and sarcopterygians develop numerous types of centra that include, among others, the presence of holocentrum, chordacentrum, and autocentrum. The chordacentrum, a mineralization or calcification of the fibrous sheath of the notochord, is only found in actinopterygians, whereas an autocentrum is a synapomorphy of teleosts above Leptolepis coryphaenoides. The chordacentrum, formed by migration of cartilaginous cells from the arches into the fibrous sheath of the notochord and usually covered by a thin calcification, is a unique feature of chondrichthyans. The actinopterygian chordacentrum and the chondrichthyan chordacentrum are not homologous. The postcaudal cartilaginous centrum is only known in postcaudal vertebrae of living dipnoans. The holocentrum is present in certain fossil dipnoans and actinopterygians, where it has been independently acquired. It is formed by proliferation of cartilage cells around the elastica externa of the notochord. These cells later ossify, forming a compact centrum. A vertebral column formed by a persistent notochord without vertebral centra is the primitive pattern for all vertebrates. The formation of centra, which is not homologous among vertebrate groups, is acquired independently in some lineages of placoderms, most advanced actinopterygians, and some dipnoans and rhipidistians. Several series of structures are associated with the vertebral column such as the supraneurals, interhaemals, radials, and ribs. In living dipnoans median neural spine, "supraneural," and dorsal radial result from growth and distal differentiation of one median cartilage into two or three median bones during ontogeny. The median neural spine articulates with the neural arch and fuses with it in the caudal vertebrae early in ontogeny. Two bones differentiate in the anterior abdominal vertebrae, i.e., the proximal neural spine and the distal "supraneural." Three bones differentiate in front of the dorsal fin, i.e., the proximal neural spine, the middle "supraneural", and the distal radial; the same pattern is observed in front of the anal fin (the proximal haemal spine, the middle interhaemal, and the distal radial). Considering that the three dorsal (and also the three ventral) bones originate from growth of only one cartilage, they cannot be serial homologs of the neural spines, or "supraneural." They are linear homologs of the median neural cartilage in living dipnoans. The development of these elements differs within osteichthyans from sarcopterygians to actinopterygians, in which the neural spine originates as a continuation of the basidorsal arcualia and in which the supraneural and radial originate from independent cartilages that appear at different times during early ontogeny. The ribs of living dipnoans are unique in that they are not articulated with parapophyses, like in primitive fossil dipnoans, but a remnant of the ventral arcuale surrounded by a small arcocentrum remains at its base. A true caudal fin is absent in living dipnoans. The postcaudal cartilages extend to the caudal tip of the body separating dorsal and ventral rays (or the camptotrichia). Actinotrichia are present in young dipnoans. They are also known in extant actinistians and actinopterygians. They probably represent the primitive state for teleostomes. In contrast, the camptotrichia are unique for extant dipnoans (and probably Carboniferous and younger dipnoans). Lepidotrichia apparently developed many times among osteichthyans.

A new specimen of the thyreophoran dinosaur cf. Scelidosaurus with soft tissue preservation

A new specimen, comprising eight articulated caudal vertebrae in a cut slab of blue/grey carbonate mudstone, is comparable to the early thyreophoran dinosaur Scelidosaurus harrisonii Owen from the English Lower Jurassic. Palynological analysis indicates that the specimen is probably late Hettangian–Sinemurian (Early Jurassic), but the exact horizon and locality remain uncertain. The slab has been cut longitudinally in a parasagittal plane along the vertebral series and exposes several articulated centra, haemal arches, neural arches and osteoderms. An envelope of preserved soft tissue wraps around the vertebrae and includes osteoderms with organic material on both the upper and lower surfaces. Basal thyreophoran dinosaur osteoderms were covered by a horny sheath during life.

The evolution of thunniform locomotion and heat conservation in scombrid fishes: New insights based on the morphology ofAllothunnus fallai

Two significant functional differences—a more anterior and internally positioned red myoÍtomal muscle mass and modification of the red-muscle vascular supply to form counter-current heat exchangers—distinguish the tunas (tribe Thunnini) from other species in the teleost family Scombridae. Neither of these characteristics is found in the bonitos (tribe Sardini), the sister group to the Thunnini. The most recent scombrid classification places the slender tuna, Allothunnus fallai, in the tribe Sardini, but some earlier studies suggested that this species should be a member of the Thunnini. Allothunnus fallai does not possess the lateral subcutaneous arteries and veins or the lateral heat-exchanging retia typical of tunas. However, we have found that this species has a highly modified central circulation (dorsal aorta, post cardinal vein, and associated branch vessels) similar to the central heat-exchanging retia of certain tunas, an enlarged haemal arch to accommodate this structure, and the anterior, internal placement of red muscle characteristic of tunas. With these new characters, phylogenetic reconstructions based on parsimony place A. fallai as the sister taxon to the tunas, establish that it is the most basal tuna species, and support the hypothesis that the derivation of tunas from a bonito-like ancestor occurred through selection for an integrated set of characteristics affecting locomotion and endothermy. The major features of this hypothesis are as follows. (1) Selection for continuous, steady, and efficient swimming resulted in changes in body shape (the result of enlargement of the anterior myotomes, the anterior and internal shift of red muscle, and a narrowing of the caudal peduncle) which increased streamlining and led to the adoption of the thunniform swimming mode unique to the tunas. (2) Alterations in blood supply necessitated by the anterior shift in red muscle led to the interdigitation of numerous arterial and venous branches which set the stage for heat conservation. (3) The evolution of endothermy, together with thunniform swimming, contributed significantly to the ecological radiation and diversification of tunas during the Early Tertiary Period. Our studies of A. fallai thus suggest that the shift in red muscle position and changes in central circulation preceded the evolution of red-muscle endothermy. Co-evolutionary changes in red muscle quantity and distribution and in vascular specializations for heat conservation have led to different macroevolutionary trajectories among the now five genera and 14 tuna species of tunas and appear to reflect the influence of changing paleocological and paleoceanographic conditions, including cooling, that occurred in the Tertiary.

The evolution of thunniform locomotion and heat conservation in scombrid fishes: New insights based on the morphology of Allothunnus fallai

Two significant functional differences—a more anterior and internally positioned red myoItomal muscle mass and modification of the red-muscle vascular supply to form counter-current heat exchangers—distinguish the tunas (tribe Thunnini) from other species in the teleost family Scombridae. Neither of these characteristics is found in the bonitos (tribe Sardini), the sister group to the Thunnini. The most recent scombrid classification places the slender tuna, Allothunnus fallai, in the tribe Sardini, but some earlier studies suggested that this species should be a member of the Thunnini. Allothunnus fallai does not possess the lateral subcutaneous arteries and veins or the lateral heat-exchanging retia typical of tunas. However, we have found that this species has a highly modified central circulation (dorsal aorta, post cardinal vein, and associated branch vessels) similar to the central heat-exchanging retia of certain tunas, an enlarged haemal arch to accommodate this structure, and the anterior, internal placement of red muscle characteristic of tunas. With these new characters, phylogenetic reconstructions based on parsimony place A. fallai as the sister taxon to the tunas, establish that it is the most basal tuna species, and support the hypothesis that the derivation of tunas from a bonito-like ancestor occurred through selection for an integrated set of characteristics affecting locomotion and endothermy. The major features of this hypothesis are as follows. (1) Selection for continuous, steady, and efficient swimming resulted in changes in body shape (the result of enlargement of the anterior myotomes, the anterior and internal shift of red muscle, and a narrowing of the caudal peduncle) which increased streamlining and led to the adoption of the thunniform swimming mode unique to the tunas. (2) Alterations in blood supply necessitated by the anterior shift in red muscle led to the interdigitation of numerous arterial and venous branches which set the stage for heat conservation. (3) The evolution of endothermy, together with thunniform swimming, contributed significantly to the ecological radiation and diversification of tunas during the Early Tertiary Period. Our studies of A. fallai thus suggest that the shift in red muscle position and changes in central circulation preceded the evolution of red-muscle endothermy. Co-evolutionary changes in red muscle quantity and distribution and in vascular specializations for heat conservation have led to different macroevolutionary trajectories among the now five genera and 14 tuna species of tunas and appear to reflect the influence of changing paleocological and paleoceanographic conditions, including cooling, that occurred in the Tertiary.

Desenvolvimento osteológico de Hippocampus reidi Ginsburg (Pisces, Syngnathiformes, Syngnathidae), em laboratório: I. Período embrionário

The cartilaginous Structures of the cmbryos of Hippocampus reidi Ginsburg, 1933, were described as well as the beginning of the ossification process in the dentary, angular, retroarticular, operculum, frontal, supraoccipital bones and neural end hemal arches. The viteline sac is well developed. The results show that cartilaginous structures are predominam in specimens with an average of 4.85 mm in total length.

A new species,Gazza rhombea, from the Indo-West Pacific, with a redescription ofG. achlamys Jordan & Starks, 1917 (Perciformes: Leiognathidae)

Gazza rhombea sp.nov. is described from 61 type and 81 non-type specimens, 19–176 mm in standard length, collected from the Indo-West Pacific. The species is similar to other congeners in general body appearance, differing from them in having the dorsolateral surface of the body scaled anterior to the dorsal fin origin, but not reaching to a vertical through the tip of the posterior branch of the supratemporal canal (vs. dorsolateral surface of body naked anterior to base of sixth or seventh dorsal fin spine base inG. achlamys; dorsolateral surface of body with scales extending anteriorly beyond tip of posterior branch of supratemporal canal inG. minuta), and having a long narrow anterodorsal extension from the subocular silvery region, in contact with the orbit only proximally (vs. broad anterodorsal extension, with proximal and distal contact with orbit inG. dentex).Gazza rhombea is also distinguishable fromG. achlamys andG. minuta by the morphology of the first dorsal fin pterygiophore, and the neural and hemal spines of the fifth preural centrum. The new species has usually been misidentified asG. achlamys, which is redescribed here, owing to its similarly deep-bodied appearance.