Showing papers in "Japanese Journal of Ichthyology in 1989"
TL;DR: Early formation of otolith was studied on artificially hatched larvae of the Japanese eel, Anguilla japonica, finding a distinct dark ring with the diameter of 6–12 μm which seems to be a “hatch check” deposited at hatching, since its diameter roughly agreed with that of the sagitta in the newly-hatched larvae.
Abstract: Early formation of otolith was studied on artificially hatched larvae of the Japanese eel,Anguilla japonica. Newly hatched larvae had a pair of sagittae which were flat and subelliptical with 8.3 μm in mean diameter. The diameter of the sagitta increased linearly with age. No growth increments were observed in the sagitta at hatching, while larvae which were 2, 4 and 6 days old had on average 2.1, 3.6 and 6.0 increments, respectively. The number of the increments (Y) and the age in days after hatching (X) showed a close linear relationship (Y=0.96X+ 0.06, r = 0.913, n = 40), suggesting daily deposition of sagittal increments. In 95 % of the field-caught elvers of this species, a distinct dark ring (check) with the diameter of 6–12 μm was found around the nucleus of the sagitta. This seems to be a “hatch check” deposited at hatching, since its diameter roughly agreed with that of the sagitta in the newly-hatched larvae. Possibly, the number of the increments outside the hatch check represents the age of the fish in days.
66 citations
TL;DR: Examination of the vascular system by a corrosion casting method showed that no place other than the venous circulation exists for the erythrocytes released from the contracted spleen, implying that the fish spleen supplies stored hemoglobin into the circulating blood in response to an increased demand of oxygen during exercise.
Abstract: Erythrocyte-supplying function of the spleen was examined in the rainbow troutSalmo gairdneri under exercise. The spleen showed remarkable reduction, about 70% in weight and about 85% in hemoglobin content, after forced exercise of 15 min. The amount of erythrocytes released from the spleen was 2.33 ml/kg body, and this amount corresponds to about 20% of the total volume of circulating erythrocytes in resting condition. No damage was observed at the spleen, splenic artery and splenic vein after the exercise. Examination of the vascular system by a corrosion casting method showed that no place other than the venous circulation exists for the erythrocytes released from the contracted spleen. The spleen was strongly constricted by infusion of adrenaline into the organ. These facts imply that the fish spleen supplies stored hemoglobin into the circulating blood in response to an increased demand of oxygen during exercise, under the control of the sympathetic nervous system.
50 citations
TL;DR: On the basis of external morphology and anatomy, 17 scpeies of the genusSilurus Linnaeus including a new species, S. torrentis from Thailand and Burma, are recognized as valid and an anatomical study of 12 species reveals the diagnostic feature ofthe genusParasilurus Bleeker to be invalid, and the genus is synonymized withSilurus.
Abstract: On the basis of external morphology and anatomy, 17 scpeies of the genusSilurus Linnaeus including a new species,S. torrentis from Thailand and Burma, are recognized as valid.S. bedfordi Regan is synonymized withS. asotus, andS. goae Haig is transferred to the genusOmpok. From an anatomical study of 12 species, the diagnostic feature of the genusParasilurus Bleeker is revealed to be invalid, and the genus is synonymized withSilurus. From the phylogenetic analysis, the genusSilurus is divided into two major species groups, thecochinchinensis group which is disributed mainly in Southeast Asia, and theglanis group which is further separated into three subgroups occurring separately in East Asia and Europe. The pattern of distribution and relationships between ontogeny and phytogeny in the genusSilurus are briefly discussed.
45 citations
TL;DR: The results suggest that the former four types of the freshwater goby are clearly discrete species and the latter four types may be considered as intraspecific variations of a fifth species.
Abstract: Genetic differentiation among eight color types of the freshwater goby,Rhinogobius brunneus, from the western part of Japan was investigated by using electrophoretic methods. Four sympatric types (Cross-band, Dark, Cobalt and Large-Dark (A) types) did not share alleles at between one and six loci out of 12 loci tested. No hybrid specimens were found among these types. The average genetic distances among these four types ranged from 0.13 to 0.72, which fall within the range of values among congeneric species of fishes. The average genetic distances among the other four types, Large-Dark (B), Orange, Shinji-Lake and Boso types, were only 0.01 to 0.03, and fall within the range of values among conspecific populations. These results suggest that the former four types are clearly discrete species and the latter four types may be considered as intraspecific variations of a fifth species.
42 citations
TL;DR: Gastro-respiratory tract of the loach,Lepidocephalichthys guntea has been studied with special reference to the nature of its mucus secreting epithelia to show a predominance of acidic mucosubstances over the neutral ones throughout the digestive tube.
Abstract: Gastro-respiratory tract of the loach,Lepidocephalichthys guntea has been studied with special reference to the nature of its mucus secreting epithelia. The mucous cells are strongly PAS-positive and their number per unit area (mm2) in the mucosal layers of oesophagus, intestinal bulb, intestine and rectum are 733, 531, 223 and 540, respectively. The air-breathing segment of the gut is completely devoid of neutral mucosubstances, and there is a predominance of acidic mucosubstances over the neutral ones throughout the digestive tube. The air-blood pathway of the accessory respiratory organ is about 2.6 μm which is higher than the values of air-breathing organs of other fishes.
25 citations
TL;DR: Of the 70 specimens of the lantern shark,Etmopterus unicolor, collected in Suruga Bay and adjacent waters, 22.9% were abnormal hermaphrodites, 30.0% normal males, and 47.1% normal females, and fifteen had female reproductive organs composed of normal ovaries, oviducts, nidamentai glands and uteri as well as claspers.
Abstract: Of the 70 specimens of the lantern shark,Etmopterus unicolor, collected in Suruga Bay and adjacent waters 22.9% were abnormal hermaphrodites, 30.0% normal males, and 47.1% normal females. Fifteen hermaphrodites had female reproductive organs composed of normal ovaries, oviducts, nidamentai glands and uteri as well as claspers. The clasper lengths of these hermaphrodites increased rapidly after the sharks reached 510 mm TL, the length about equal to the size at maturity for normal females. The ovary and uterus of abnormal females became mature at a total length greater than 500 mm, whereas the size at maturity was about 500 mm TL for normal females compared to 460 mm TL for normal males. In one specimen, the left gonad contained both ovarian and testicular tissues, the bulk of which was testicular.
25 citations
TL;DR: Nomenclature and abbreviations are proposed for the cartilaginous elements of the caudal skeleton of teleostean fishes on the basis of examination of 510 species within 198 families of 31 orders and the determination of the positional relationship between these structures and the bony elements.
Abstract: Nomenclature and abbreviations are proposed for the cartilaginous elements of the caudal skeleton of teleostean fishes. These were developed on the basis of examination of 510 species within 198 families of 31 orders and the determination of the positional relationship between these structures and the bony elements. A review of the most important relative literature is also provided.
21 citations
TL;DR: The Shiraho reef is one of the few healthy coral reefs remaining in Japanese waters and is considered to be a center of biological diversity in the Western Pacific region (Wells, 1987).
Abstract: The study site. The Shiraho reef is one of the few healthy coral reefs remaining in Japanese waters (Muzik, 1985; Yasumoto, 1986). The reef contains at least 41 genera and more than 100 species of scleractinian corals, which serve as the habitat for more than 300 species of reef fishes (McAllister, 1988). Both coral and fish diversity is comparable to that of the Philippines, which is considered to be a center of biological diversity in the Western Pacific region (Wells, 1987). Four channels to the open sea are found along the 4 km length of the Shiraho reef. These are known by the following names : Nawabari, Bu-guchi, Moriyama-guchi, and Sumuji-guchi (also known as Ika-guchi) (Fig. 1). Moriyama-guchi, with a depth of 5 m and widths of 20-30 m, is the largest of Shiraho's reef channels. Another large reef channel, Touro-guchi, lies 3.1 km to the north. It was hypothesized, following the work of Johannes (1978), that these reef channels would prove to be important spawning sites. Observations utilizing both snorkel and SCUBA were made on 4 and 5 October, 1987 (see Moyer, 1988), and daily from 26 April to 6 May, 1988. During surveys using SCUBA, I remained motionless at specific sites within the channel under study for varying periods of time and recorded species of fishes making spawning migrations, courting, and/or spawning. Modes of spawnings (see Warner et al., 1975) and spawning times to the nearest minute were recorded, according to species. Such a method required constant scanning of the surroundings at all sites and resulted in very conservative counts for any one species; i.e., observations of one particular species came at the expense of all others. Observations were made to coincide with the ebbing tide, however this turned out to be difficult due to the fact that wind direction and large ocean swells often produced drainage from the reef moat prior to high tide, i.e. during incoming tides, as water piled up inside the reef. Surveys in April of all four channels in the Shiraho reef system disclosed that all were used by spawning fishes. The spawning site at Moriyama-guchi was by far the most impressive, and detailed spawning observations were made at that site.
20 citations
TL;DR: Morphological comparisons are made from the study of 64 specimens belonging to the following species and the results suggest conspecificity between S. megalops and S. acutirostris.
Abstract: Morphological comparisons are made from the study of 64 specimens belonging to the following species:Squalus acanihias, S. blainvillei, S. megalops andS. acutirostris. The results suggest conspecificity betweenS. acutipinnis andS. megalops. The differences betweenS. blainvillei andS. megalops in the E-Atlantic are stressed. The Indo-Pacific species calledS. blainvillei by Chen et al. (1979) is regarded in this paper as probably an undescribed species. Some consideration on the status of several nominal species and the species grouping withinSqualus are also made.
20 citations
20 citations
TL;DR: In the present two wrasses, it seemed that the above-mentioned difference of noctural behavior was closely related to the intensity of the endogenous factor in the activity rhythm.
Abstract: The locomotor activity rhythms were examined by using an actograph with infra-red photo-electric switches for two species of wrasses, (Halichoeres tenuispinnis andPteragogus flagellifera) under various light conditions. InH. tenuispinnis, the locomotor activity of almost all fish under light-dark cycle regimen (LD12:12; 06:00–18:00 light, 18:00–06:00 dark) commenced somewhat earlier than the beginning of light period and continued till somewhat earlier than the beginning of the dark period. This species clearly showed free-running activity rhythms under both constant illumination (LL) and constant darkness (DD). Therefore,H. tenuispinnis appeared to have a circadian rhythm. The length of the circadian period ranged from 23 hr. 30 min. to 23 hr. 44 min. under LL, and was from 23 hr. 39 min. to 24 hr. 18 min. under DD. On the other hand, the locomotor activity ofP. flagellifera occurred mostly in the light period under LD 12:12. The activity of this species continued through LL, but was greatly suppressed in DD, so that none of the fish had any activity rhythm in both constant conditions. It was known from field observations thatH. tenuispinnis burrowed and lay in sandy bottoms, whileP. flagellifera hid and rested in bases of seagrasses and shallow crevices of rocks during the night. In the present two wrasses, it seemed that the above-mentioned difference of noctural behavior was closely related to the intensity of the endogenous factor in the activity rhythm.
TL;DR: The development of pharyngeal dentition was observed in the big head, Aristichthys nobilis, which is one of the hypophthalmichthyines of the cyprinids, which gives a hint on their phylogeny.
Abstract: The development of pharyngeal dentition was observed in the big head,Aristichthys nobilis, which is one of the hypophthalmichthyines of the cyprinids. This fish has the C-type larval dentition, in which no teeth ever occur at the position An3, and in which the first tooth at the position An2 is on the third replacement wave. So the positions Pol, Ce0, Ani and An2 in the larval dentition correspond to the positions A4, A3, A2 and A1 in the adult dentition, respectively. The initial tooth at each position is a conical one. The conical teeth are then changed to ones bearing a narrow grinding surface with a hook at the tip and some denticles on the margins. These teeth are of theLeuciscus stage. Tn the following teeth, the grinding surface is expanded, and the denticles are increased in number and distributed on not only the margins but also the whole grinding surface. These teeth bearing a very broad grinding surface characterize the hypophthalmichthyines. At the positions A2 to A4, the teeth become the hypophthalmichthyine type in the larval period. But the tooth at the position A1 becomes the hypophthalmichthyine type in the juvenile period. The morphological change of teeth in this species is simple although their teeth are highly specialized. We think that this phenomenon gives a hint on their phylogeny.
TL;DR: It is shown that the form of the body has an effect on the degree of encephalization, and elongate fishes have low values, probably because of the excessive mass of their body skeleton which raises the body weight relative to the brain size.
Abstract: We have measured the brain and body weight and determined the encephalization index for 180 species of fishes belonging to six families of the suborder Gobioidei. Within the Teleostei, these fishes exhibit a remarkably broad range in the values of their encephalization indices, but most values are in the low to middle range. Within the Gobioidei there is relatively little difference in the degree of encephalization among the different families and subfamilies except the Kraemeriidae and Amblyopinae which have low encephalization indices and the Oxudercinae (including Periophthalmus) and Rhyacichthyidae which are highly encephalized. We have shown that the form of the body has an effect on the degree of encephalization. Elongate fishes have low values, probably because of the excessive mass of their body skeleton which raises the body weight relative to the brain size. The environment in which the fishes live is correlated, in general, with their relative brain size. The values of the encephalization index arranged from low to high by habitat are as follows: muddwelling fishes, freshwater fishes, brackishwater fishes, burrowing marine fishes, freeliving marine fishes, torrent fishes and amphibious fishes. The low values of the Amblyopinae and Kraemeriidae can be explained in terms of their being both mud-dwelling and elongate.
TL;DR: The results suggest that female life history varies along the course of the Daitobetsu River and thus allow us to consider the following alternative reproductive tactics: when females stay in the lower reaches, they attain sexual maturity at a smaller body size and younger age, and have a small clutch size, but when females migrate into the upper reaches, their maturity is delayed until they reach a larger body Size and older age.
Abstract: Growth patterns of the 1982 year-class, individual growth patterns, age and size at sexual maturity and longevity in females of the river-sculpin,Cottus hangiongensis (Cottidae), were examined along the course of the Daitobetsu River of southern Hokkaido, Japan. Growth of females slightly varied both along the river course and among individual fishes: slow growth occurs in females from the lower reaches, while more rapid growth occurs in females from upstream areas. Body size and age at the first sexual maturity of females slightly increased towards the upstream, from 52 mm SL and 2 years in the most downstream area to 72 mm SL and 2–3 years in the uppermost site. Longevity was estimated to be 7 years in the downstream areas and 8–9 years in the upstream sites. These results suggest that female life history varies along the course of the river and thus allow us to consider the following alternative reproductive tactics: when females stay in the lower reaches, they attain sexual maturity at a smaller body size and younger age, and have a small clutch size, but when females migrate into the upper reaches, their maturity is delayed until they reach a larger body size and older age, and have a greater clutch size.
TL;DR: Limited sampling of fish larvae near Lizard Island in the Great Barrier Reef Lagoon indicates that conventional midwater plankton sampling is adequate for most fish larvae found in the Lizard Island area, but for the larvae of the above ten families, this could produce large underestimates of abundance.
Abstract: Epibenthic fish larvae near Lizard Island in the Great Barrier Reef Lagoon were sampled with a plankton sled during daylight in November 1981 and January–February 1982. Abundance in the epibenthos was highly variable, and although many types of larvae were present, few were concentrated there relative to the water column. Among those taxa concentrated in the epibenthos, abundances were low and variances were high. Larvae of bregmacerotids, callionymids, clupeids, monacanthids, pinguipedids, platycephalids, pseudochromids, and especially schindleriids, leiognathids and terapontids were concentrated in the epibenthos. Few reef fish larvae were epibenthic. There was some evidence of diel and ontogenetic movements into and out of the epibenthos. Our limited sampling indicates that conventional midwater plankton sampling is adequate for most fish larvae found in the Lizard Island area, but for the larvae of the above ten families, this could produce large underestimates of abundance.
TL;DR: The striped goby was characterized by having more than 50 scales in a longitudinal row and 2 black longitudinal bands from the head to the tail and can be classified into 2 separate species, T. trigonocephalus and T. bifasciatus.
Abstract: The striped goby was characterized by having more than 50 scales in a longitudinal row and 2 black longitudinal bands from the head to the tail. It has been regarded as 1 species since Tomiyama (1936) grouped several nominal species into one,Tridentiger trigonocephalus (Gill, 1858). But detailed study has revealed that it can be classified into 2 separate species,T. trigonocephalus andTridentiger bifasciatus Steindachner, 1881, on the basis of the difference mainly in the forms of the sensory canals and pectoral fins and in the coloration.T. trigonocephalus has been collected from Hokkaido to Kyushu in Japan, and in Korea, China, and Hong Kong abroad. It has immigrated into both California, U.S.A., and New South Wales and Victoria, Australia.T. bifasciatus has been collected in the same area asT. trigonocephalus in Japan, and in the Soviet Union, Korea, China, and Taiwan abroad. Both species inhabit brackish and sea water with stony bottoms, and are often found in the same place. However,T. trigonocephalus has seldom been found in very dilute brackish water, andT. bifasciatus has not been found in undiluted sea water. The type specimen ofT. trigonocephalus has not been found, but the identification toT. trigonocephalus was decided on the basis of the closeness of the numbers of the 2nd dorsal and anal fin rays to those of the original description, which were 14 and 13, respectively. In addition, the type specimen was collected in the port of Hong Kong, where the water is not diluted and is unlikely to be suitable as habitat forT. bifasciatus.
TL;DR: The structure of the air-breathing organs of Monopterus (=Amphipnous)cuchia has been studied by using light, scanning and transmission electron microscopy and the morphological basis for buccopharyngeal respiration, aerial as well as aquatic has been established.
Abstract: The structure of the air-breathing organs ofMonopterus (=Amphipnous)cuchia has been studied by using light, scanning and transmission electron microscopy and the morphological basis for buccopharyngeal respiration, aerial as well as aquatic has been established. Respiratory islets are well distributed over the surface of the buccopharynx, hypopharynx and branchial arches extending deep into the gill clefts but occupy only the anterior two-thirds of the air sacs, the remaining posterior one-third part seems to be non-respiratory in function and may serve as a reservoir for residual air. Arterioles penetrate deep into the epithelial region of air sacs and buccopharynx in spiral-like fashion to form the characteristic vascular papillae of the respiratory islets. In juvenile fish new respiratory islets develop in the non-vascular part of the air sac in between large older islets as sprout-like structures. The respiratory area, capillary loading, thickness of air-blood tissue barrier, and the diffusing capacity of the respiratory membrane of a 200 g fish were found to be 20 cm2, 2.72 cm3/m2, 0.72 × 10−4 cm, and 0.00165 ml O2/min/mmHg/kg, respectively.
TL;DR: Coho and chum developed squamation and formed circuli on scales considerably earlier than masu and pink salmons, and developed faster than the other species when raised at constant water tempertaure.
Abstract: Morphological divergence including scale formation in alevin and juvenile stages of masu (Oncorhynchus mason), coho (O. kisutch), chum (O. keta) and pink (O. gorbuscha) salmons reared in freshwater was investigated. Chum and coho salmons developed faster than the other species when raised at constant water tempertaure. Growth decreased suddenly at emergence from the gravel bed in all the four species. Morphology changed significantly from hatch through emergence to squamation. Two distinct morphological types were identified: the rotund type (masu and coho), and the streamlined type (chum and pink salmons). The former had well-developed parr marks, a deeper body and caudal peduncle, and higher relative growth coefficients, while the latter had parr marks which appeared only temporarily or never appeared, a slimmer body and caudal peduncle, and a more gradual and continuous change in morphology. Coho and chum developed squamation and formed circuli on scales considerably earlier than masu and pink salmons.
TL;DR: Factors indicate that the two types of S. undosquamis should be recognized as distinct species, based on allelic frequencies at 23 genetic loci surveyed electrophoretically and some morphological characters.
Abstract: Genetic divergence in four taxa of three species ofSaurida, S. undosquamis south (S) and north (N) types,S. wanieso andS. elongata caught from the East China Sea, Sea of Hyuga and Tosa Bay, was studied based on allelic frequencies at 23 genetic loci surveyed electrophoretically. Fixed allele substitution was observed at eight loci between the S and N types ofS. undosquamis and their genetic distance was 0.5582, within a range of differentiation at the species level. The S type ofS. undosquamis was found to inhabit the Sea of Hyuga and off Cape Ashizuri along the Kuroshio Current, in addition to the East China Sea. The low level of genetic variation found for this type was discussed in relation to its restricted habitat at the edge of the continental shelf. These factors, along with some morphological characters, indicate that the two types ofS. undosquamis should be recognized as distinct species.
TL;DR: The retinal features of mormyrid fishes were compared with those of other fish species belonging to the Notopteroidei such as the Hiodontidae, Notopteridae and Gymnarchidae, and related to the chemical nature of notopterid and gymnarchid tapetum.
Abstract: The eye of mormyrid fishes (Marcusenius andGnathonenius) contains a retinal tapetum composed of guanine crystals. InMarcusenius, the quantity of guanine is about 2 mg cm−2 of the retinal surface area. The retina is duplex, and the cones and rods are grouped in bundles. Each bundle is surrounded by pigment epithelial cell processes which contain numerous guanine reflectors. Two kinds of reflector are present: brick-shaped and rodlet. Mormyrids may use their high sensitivity for nocturnal activities. The retinal features of mormyrid fishes were compared with those of other fish species belonging to the Notopteroidei such as the Hiodontidae, Notopteridae and Gymnarchidae, and related to the chemical nature of notopterid and gymnarchid tapetum.
TL;DR: Embryonic development and morphology of the eggs, egg masses and larvae of the scorpaenid fish, Scorpaena miostoma are described on the basis of the laboratory-reared specimens.
Abstract: Embryonic development and morphology of the eggs, egg masses and larvae of the scorpaenid fish,Scorpaena miostoma are described on the basis of the laboratory-reared specimens The gelatinous egg mass is not bilobed but simple, oval and balloon-like in shape It usually floats at or near the surface The individual egg is colorless and ovoid in shape, measuring 086 × 075 mm Hatching occurs between ca 34 and 40 hours after spawning at the water temperature of 22–24°C A newly hatched larva measures 155 mm in notochord length and has ca 25 myomeres The finfold is balloon-like in shape and almost completely covers the larval body Minute “cell-like” granules scatter on the findfold
TL;DR: The dorsal duct and its lamellar projections are remnants of the ovarian cavityoviduct system and ovigerous lamellae ofThe ovarian portion of the gonad, and that these two nemipterid species are rudimentary hermaphrodites in which males have bisexual gonads of the delimited type in their juvenile stages.
Abstract: Gonads of young and adultNemipterus bathybius andN. virgatus were examined histologically. In youngN. bathybius males, the testis is composed of a dorsal and a ventral zone separated by thin connective tissue. A duct runs through the center of the dorsal zone, and has an opening on the ventromedian surface of the body, separate from the male genital pore. Along with the start of spermatogenesis in the ventral zone, germ cells distributed in the dorsal zone also begin spermatogenesis and eventually develop into spermatozoa. Consequently, in mature testes the sperm sinuses are formed to enclose the dorsal duct, leaving a small number of germ cells, including oviform cells, retained in the lamellar projections of the duct. Testes ofNvirgatus also have essentially the same histological characteristics. No trace of testicular tissue is present in the ovaries, except in four cases of intersexual gonads found in both nemipterid species. It is concluded that the dorsal duct and its lamellar projections are remnants of the ovarian cavityoviduct system and ovigerous lamellae of the ovarian portion of the gonad, and that these two nemipterid species are rudimentary hermaphrodites in which males have bisexual gonads of the delimited type in their juvenile stages.
TL;DR: A new deep-sea ophidiid fish, Bassozetus levistomatus, is described on the basis of a single specimen trawled from the Izu-Bonin Trench, Japan, at a depth of 5,160 m.
Abstract: A new deep-sea ophidiid fish,Bassozetus levistomatus, is described on the basis of a single specimen trawled from the Izu-Bonin Trench, Japan, at a depth of 5,160 m. This species differs from its congeners by having the toothless head of its prevomer covered with the oral epithelium. It is further distinguished by the following combination of characters: no median basibranchial tooth patches, 29 pectoral fin rays, and 11 developed rakers on the first gill arch.
TL;DR: The morphology of the kidney, adrenocortical homolog, and the corpuscles of Stannius was examined in the cockscomb prickleback, Anoplarchus purpurescens, a marine teleost which inhabits the intertidal zone.
Abstract: The morphology of the kidney, adrenocortical homolog, and the corpuscles of Stannius was examined in the cockscomb prickleback,Anoplarchus purpurescens, a marine teleost which inhabits the intertidal zone. The paired kidneys of this fish are fused throughout most of their length, there is essentially a single posterior cardinal vein on the right side, they possess renal corpuscles, and there is no distal segment of the tubule. The tubule is specialized, in descending order, into ciliated neck and two proximal segments before entering the system of collecting tubules and ducts. The cells of the latter system are specialized for mucous secretion, as are cells of the main excretory ducts, the paired archinephric ducts. Tubulogenesis occurs in the kidneys in close apposition to the archinephric ducts. The presumptive adrenocortical homolog is located around the posterior cardinal veins in the head kidney while paired corpuscles of Stannius are confined to the posterior end of the kidney. All of the above features are consistent with those found in the kidneys of many other marine teleosts.
TL;DR: The gills of the air-breathing estuarine goby,Pseudapocryptes lanceolatus, are reduced owing to the development of a specialized organ of O2 uptake from air.
Abstract: The gills of the air-breathing estuarine goby,Pseudapocryptes lanceolatus, are reduced owing to the development of a specialized organ of O2 uptake from air. In the first gill arch, the filaments of the outer hemibranch are reduced to nearly one-half in comparison to those of its inner hemibranch. A smaller number of secondary lamellae per mm (27.6) occurring on one side of the gill filament reduces the gill surface area. A bilogarithmic plot of the gill area and the body weight indicates a curve with two significantly different components, one (b = 0.924) related to the fish weighing up to 6 g and the other (b = 0.405) to the fish weighing 8 g and above.
TL;DR: The segmental vessels are completely double-tracked,i.e., every unit consists of an artery and a vein closely coupling up to the distal end, instead of an arteries or a vein alternating in a series.
Abstract: A description is presented about the arrangement of the whole vascular system and the lateral musculature of the yellowtail. The sino-atrial valves are bilaterally continuous with the longitudinal bundles of atrial trabeculae, which keep the valves closed during atrial systole. The afferent filament arteries leave the afferent arch artery rather oppositely, far from the filament rows to interlock with the basal portions of the efferent filament arteries, then run down towards the filaments. The departure of the coeliaco-mesenteric artery is preceded by baffles equipped within the median dorsal aorta, so that the straight aortic flow is partially turned towards the coeliacomesenteric artery. The segmental vessels are completely double-tracked,i.e., every unit consists of an artery and a vein closely coupling up to the distal end, instead of an artery or a vein alternating in a series. Such double tracking of the segmental vessels may represent a pre-adaptive modification that allowed tunas’ ancestors to evolve the vascular heat exchangers. Each myomere is subsegmented into four “submyomeres” and as a result, the lateral musculature looks as if it were made up of a larger number of narrower myomeres.