Early development of fin-supports ani fin-rays in the milkfishChanos chanos

Development of fin-supports and fin-rays was observed in larval and juvenileChanos chanos, Chondrification of the caudal complex started at 4.70 mm SL. Ossification of the caudal elements started at 7.80 mm SL and was nearly completed at about 30 mm SL. Cartilaginous fusion of caudal elements, which occurs in hypurals of higher teleostean fishes but is not seen in lower teleosts, was observed between the neural arch of the preural centrum 1 and that of the ural centrum 1 via a small cartilage bridging the distal tips of the two arches. Caudal finrays began to develop at 6.60 mm SL, and an adult complement of principal rays was attained at 7.35 mm SL. Dorsal and anal pterygiophore elements were first evident at 6.70 mm and 6.65 mm SL, respectively. All proximal radiais were formed at 8.15 mm SL in both fins. Formation of dorsal and anal fin-rays started simultaneously at 8.60 mm SL, and adult fin-ray complements were attained at 10,00 mm and 10.70 mm SL, respectively. In the pectoral fin, the cleithrum, coraco-scapular cartilage and blade-like cartilage (fin plate) had already been formed at 4.65 mm SL. The mesocoracoid was observed to originate from the coraco-scapular cartilage and become detached from it in the course of ossification. Pectoral fin-ray formation started at 13.80 mm SL and was completed in number of rays at 20.00 mm SL. In the pelvic fin, the basipterygium was first evident at 13.00 mm SL. Pelvic fin-rays appeared at 13.80 mm SL and attained their adult count at 17.15 mm SL.     

Osteological development in the Japanese sardine,Sardinops melanostictus

The development of all osteological elements, except scales, of the Japanese sardine,Sardinops melanostictus, is described from newly-hatched larvae to adult fishes. Newly-hatched larvae lacked osteological elements. Part of the head skeleton began to develop in 53 hour old larvae (4.2 mm in notochord length [NL]). Larvae at the first-feeding stage (77 hours, 5.5 mm NL) possessed several elements of the head skeleton and pectoral fin supports. In a 10.5 mm NL specimen, part of the caudal and dorsal fin supports were apparent. The centra appeared in specimens 18–22.7 mm in standard length (SL). Gill rakers were first observed in the lower branchial arches at 13 mm NL and spine-like processes with spiny nodules from about 25 mm SL. The distance between the predorsal and first dorsal proximal radial relative to SL rapidly decreased with forward translocation of the dorsal fin and became constant beyond approximately 34 mm SL. At this stage, most basic osteological elements were established. Completion of the osteological structure was characterized by the disappearance of the dentary teeth at 60–70 mm SL. Based on the osteological development, ontogenetic intervals consisting of four periods and eight phases were recognized.     

Morphogenesis in hatchery-reared larvae of the black rockfish,Sebastes schlegeli,and its relationship to the development of swimming and feeding functions

The developmental sequence of morphological characteristics related to swimming and feeding functions was investigated in hatchery-reared larvae and juveniles ofSebastes schlegeli, a viviparous scorpaenid. The fish were extruded at an early larval stage, when the mean body size was 6.23 mm TL. Fin-ray rudiments became visible at 9.0 mm TL in the dorsal and anal fins, at 8.0 mm TL in the pectoral and pelvic fins and 6.0 mm TL (size at extrusion) in the caudal fin. Completion of segmentation of soft rays in the dorsal and anal fins was attained by 14 mm TL and in all fins by 17 mm TL. Branching of soft rays in the respective fins started and was completed considerably later than the completion of segmentation, as well as ossification of the fin-supports. Morphological transformation from larva to juvenile was apparently completed by about 17 mm TL. Although the completion of basic juvenile structures was attained by transformation at that body size, succeeding morphological changes occurred between 17 mm and 32 mm TL. Newly-extruded larvae possessed one or two teeth on the lower pharyngeal and pharyngobranchials 3 and 4, but lacked premaxillary, dentary, palatine and prevomer teeth. The fish attained full development of gill rakers and gill teeth by 15 mm TL, the upper and lower pharyngeal teeth subsequently developing into a toothplate. Development of the premaxillary, dentary and palatine teeth was completed at about 30 mm TL, by which time loop formation of the digestive canal and the number of pyloric caeca had attained the adult condition. The developmental sequence of swimming and feeding functions during larval and early juvenile periods appeared to proceed from primitive functions to advanced or complex ones, from the ability to produce propulsive force to that of swimming with high maneuverability and from development of the irreducible minimum function of passing food into the stomach to the ability to actively capture prey via passive food acquisition with the gill rakers and gill teeth. The relationship of morphological development to the behavior and feeding activity of artificially-produced hatchlings is also discussed.     

Osteological development of the lophiid anglerfish,lophius gastrophysus

The osteological development of the head skeleton and dorsal, pectoral, and anal fin supports, are described from cleared and stained specimens ofLophius gastrophysus larvae, ranging from 4.6 to 21.8 mm NL; the results are compared with those of juvenile (79.8 mm SL) and adult (398 mm SL) specimens. Tiny conical teeth are present on the premaxillary, dentary, palatine and vomer since early stage. The first three dorsal fin spines are initially positioned on the midline of body posterior to the supraoccipital, but they migrate forward with growth and become cephalic in juveniles. The forward movement of the dorsal spines is produced by the forward extension of the cartilaginous basal inside the subepidermal space. During the planktonic larval stage the pectoral fins are on the sides of body as in ordinary fishes, but they move ventrad and become leg-like in bottom living juveniles and adults. Ossification of the caudal complex ofL. gastrophysus larvae proceeds very slowly and only the 21.8 mm NL larva has an almost completely ossified caudal complex. Eight principal caudal rays are loosely attached on the posterior edge of the hypurals and no procurrent rays are present. Larvae have well developed parhypurapophysis at the mid-portion of the urostyle which transforms into keel-like structure in juveniles and adults.     

Larval morphology and occurrence of the louvar,Luvarus imperialis (Luvaridae)

A total of nineteenLuvarus imperialis larvae, 3.5 to 10.7 mm in standard length were collected during the cruises of R/V Shoyo Maru in the northwestern Pacific and eastern Indian Ocean. This paper describes meristic and morphological features of these specimens throughout development. The features particularly noted in postlarvae and early juveniles ofL. imperialis are: 1) large head with a wide snout, 2) oval and well-compressed body, 3) large pectoral fins, 4) developed and finely serrated dorsal and pelvic spines, 5) well-developed head spination, 6) minute spines on the soft rays of all fins in larvae larger than about 5.6 mm SL, and 7) very rough body surface associated with the development of spiny-edged scales. Larvae ofL. imperialis occur mostly in the coastal waters between lat. 40°N and 40°S of the world oceans, suggested the spawning in temperate waters.     

Larval development of Hypsophrys nicaraguensis (Pisces: Cichlidae) under laboratory conditions

The cichlid Hypsophrys nicaraguensis is a popular fish known as butterfly, and despite its widespread use as pets, little is known about its reproductive biology. In order to contribute to this knowledge, the study describes the relevant larval development characteristics, from adult and larval cultures in captivity. Every 12h, samples of larvae were collected and observed under the microscope for larval stage development, and every 24h morphometric measurements were taken. Observations showed that at 120h, some larvae had swimming activity and the pectoral fins development was visible; at 144h, the dorsal fin appear and all larvae started food intake; at 168h, the formation of anal fins begins, small rudiments of pelvic fins emerge, the separation of caudal fin from anal and dorsal fins starts, and the yolk sac is reabsorbed almost completely; at 288h, the pelvic fins starts to form; at 432h, the rays and spines of dorsal and anal fins can be distinguished, both the anal and the dorsal fins have the same number of spines and rays as in adults. After 480h larvae have the first scales, ending the larval stages and starting the transformation to fingerlings. Larvae were successfully fed with commercial diet.     

Description of transformation larvae and a juvenile of the dextral flounder,poecilopsetta praelonga (pleuronectidae, poecilopsettinae) from the northwestern waters of australia

Three late metamorphic transformation larvae ofPoecilopsetta praelonga (68.0–82.3 mm SL) and a juvenile (92.7 mm SL) captured from the waters off northwestern Australia (400–460 m deep) are described. The transformation larvae ofP. praelonga are distinguishable from the congeners of the same stage in having relatively low body depth (2.20–2.44 in SL), relatively large maxilla extending to anterior one-third of lower eye, and seven and six distinct spots along the dorsal and ventral margins of ocular side body, respectively. In the smallest specimen, the intestine was expanded posteriorly beyond the posterior wall of visceral cavity, but not in the larger specimens. The pectoral fin rays and the spines of scales were supposed to begin to be formed by about 80 mm SL. Ontogenetic changes which include decreasing ratios of upper jaw length to head length. and increasing ratios of depth of body muscle to body depth, were observed, based on a comparison of transformation larvae, a juvenile and adults.     

A new pearleye (Teleostei,Aulopiformes) species from the Oligocene of Romania

A new pearleye species of the alepisauroid family Scopelarchidae, Scopelarchoides neamticus sp. nov., is described herein based on two specimens from the Oligocene Lower Dysodilic Shales Formation, cropping out in the Pietricica Mountain, Romanian Eastern Carpathians. The new species described herein exhibits a unique combination of features (including head length about 25% of SL; coracoid remarkably expanded; both preorbital and postorbital lengths larger than orbit diameter; 50 or 51 vertebrae; dorsal fin with nine or ten rays; anal-fin with 28 rays; length of anal fin base about 30% of SL; preanal distance almost 60% of SL; pelvic fin insertion located just under the second dorsal fin ray; pectoral fins only slightly longer than pelvic fins; caudal fin with 19 principal rays plus 14 upper and 13 lower procurrent rays) that justifies its recognition as a new species of the genus Scopelarchoides. Both morphological and meristic features suggest a certain degree of similarity between S. neamticus sp. nov. and the extant species Scopelarchoides signifer. The fossils of the new Oligocene species described herein represent the oldest known skeletal record of Scopelarchidae.     

Reproduction and early development of a freshwater pipefish <Emphasis Type="Italic">Microphis leiaspis</Emphasis> in Okinawa-jima Island,Japan

We investigated the size at maturation, breeding season, and morphological development of larvae and juveniles of a freshwater pipefish Microphis leiaspis, which belongs to Gastrophori, collected from three rivers on the northern part of Okinawa-jima Island, Japan. The minimum size of brooding males was 105–123 mm in standard length (SL). The smallest mature female was estimated to be ca. 130 mm SL from the analysis of gonadosomatic index (GSI) and histological observations of gonads. The breeding season was estimated to be from June to December according to monthly changes in female GSI, histological observations of gonads, and monthly changes in the occurrence of brooding males. The number of eggs in the male brood pouch ranged from 75 to 241 (mean ± SD: 152 ± 52, n = 22). The male releases newly hatched larvae in freshwater areas. After newborns grow in the sea, they return to freshwater areas of the rivers and attain maturity. Microphis leiaspis was conformed to have an amphidromous life history. Notochord length of the released larvae was 6.1 mm, with a well-developed finfold. Larvae attained 11.1 mm SL, formation of the caudal and dorsal fin rays was complete, and the caudal fin became lozenge shaped at 30 days after the release, and juveniles reached 36.0 mm SL at 63 days after release. In the period between 30 and 63 days after the release, formation of all fins except the pectoral fins was completed, and caudal fin rays were extended and sector shaped with deep slits between each fin ray. The morphology of the released larvae of M. leiaspis is similar to that of Gastrophori species, and the morphology of juveniles similar to other species of Microphis.     

Morphological aspects of feeding and improvement in feeding ability in early stage larvae of the milkfish,Chanos chanos

The osteological development of elements comprising the oral cavity and fins was examined in early stage larvae of laboratory-reared milkfish,Chanos chanos, from hatching to 200 hours after hatching. Fundamental elements of the oral cavity had developed by the time of initial mouth opening, 54 hours after hatching. The oral cavity was long and cylindrical, with a short, robust Meckel's cartilage, and robust quadrate and symplectic-hyomandibular cartilages. The initial ossification of existing elements and addition of new elements occurred between 120–146 hours after initial mouth opening (HAMO), whereas the cartilaginous basihyal and caudal fin-supports appeared at 37.5 and 61.5 HAMO, respectively. Based on the morphology and developmental patterns of characters examined in this study, the feeding mode of early stage larval milkfish was considered to be “straining,” with an improvement in feeding ability occurring between 120–146 HAMO.     

A new deepwater assfish, <Emphasis Type="Italic">Bassozetus nielseni</Emphasis> sp. nov. (Ophidiiformes: Ophidiidae), from the North Atlantic and West Indian oceans

A new deepwater assfish, Bassozetus nielseni sp. nov., is described from 29 specimens [147–615 mm in standard length (SL)] collected from the North Atlantic and West Indian oceans. It is distinguished from 13 congeners by the following combination of characters: dorsal-fin rays 122–129, long rakers on first gill arch 11–14, oblique scales 20–25, abdominal vertebrae 13–14, head length 18.1–21.3 % SL, body depth at anal-fin origin 8.2–14.6 % SL, predorsal length 16.4–20.1 % SL, tail length 62.7–68.0 % SL, posterior tip of pelvic-fin rays anterior to anus, a single median basibranchial tooth patch, dorsal margin of sagittal otolith smooth, and fins pale yellowish brown (preserved condition).     

A new species of anchovy,Encrasicholina auster (Clupeiformes: Engraulidae) from Fiji,southwestern Pacific Ocean

ABSTRACT

Encrasicholina auster sp. nov. (Clupeiformes: Engraulidae) is described on the basis of six specimens collected from Fiji, southwestern Pacific Ocean. The new species is distinguished from congeners by the following combination of characters: long upper jaw (posterior tip extending beyond posterior margin of preopercle) 20.8%–22.5% standard length (SL); long lower jaw 19.0%–20.7% SL; long head 29.1%–29.2% SL; three unbranched rays in the dorsal and anal fins; transverse scales 11; branched pectoral-fin rays 12–13; pseudobranchial filaments 19–21; gill rakers 45–49, 40–43, 26–31 and 22–25 on the first, second, third and fourth gill arches, respectively.     

Induction of ovarian maturation and development of eggs,larvae and juveniles of the tonguefish,Cynoglossus abbreviates,reared in the laboratory

Cynoglossus abbreviatus spawns from mid-March to mid-April in the Sea of Shimabara in Kyushu. During the spawning season ovarian maturation was successfully induced by injection of the pituitary homogenate ofHypophthalmichthys molitrix. The dose of the aceton-dried pituitary homogenate was 6.5 mg/kg body weight ofC. abbreviatus. It took about 2 days for ovulation after injection at a water temperature of 14 to 16°C. Artificial fertilizations were accomplished on March 29, 1974 and again on April 7, 1984, using the females matured by hormone injection in the latter case only. The larvae were reared on the rotifers,Artemia nauplii,Tigriopus japonicus and copepods collected from the sea over a period of 113 days in 1974 and 58 days in 1984. The eggs were pelagic, spherical, 1.19–1.23 mm in diameter and had 30–50 oilglobules of 0.068–0.095 mm in diameter, and the perivitelline space was narrow. The incubation period was 90–98 hours at a water temperature of 14 to 16°C. The newly hatched larvae were 3.18–3.45 mm TL and had 61–64 myomeres. The larvae had many melanophores and xanthophores on the body, forming three bands on the caudal region, but were lacking chromatophores on the finfolds. The yolk was completely absorbed when the larvae attained a size of 4.7–5.6 mm TL 8 days after hatching. A single elongated dosai fin ray developed on the head in the 8-day old larvae. The ray was reduced in size as long as the other rays 1 or 2 days after metamorphosis. The rudiment of pectoral fins were found on the both sides of the body in the 2-day old larvae, but two of them disappeared after metamorphosis. A pelvic fin first appeared as a ventral bud just anterior to the gut in the larva of 8.39 mm TL. The full count of 4 rays was observed on the larva of 10.83 mm TL. Metamorphosis began 22 days after hatching when the larvae were 11.20 mm TL. The right eye began to shift the left side of the head at night and reached to the final place after 8.5 hours. It took about 36 hours to complete the metamorphosis, including the eye movement and fusion of the hole in the rostral beak. At the last stage of metamorphosis, the dosal, caudal, anal and ventral fins became confluent. The larvae reached the juvenile stage at a size of 13.5–14.0 mm TL, approximately 28 days after hatchling. The growth of larvae reared in 1974 is expressed by the following equations: Y₁ = 3.448 · 1.0507^x (8≦X≦28) Y₂ = 6.3322 · 1.0275^x (28≦X≦75) where Y is the total length (mm) and X is the number of days after hatching. Growth rate changed after metamorphosis.     

Systematics,distribution, genetics and life history of milkfish,Chanos chanos

Synopsis Chanos chanos belongs to a monotypic gonorynchiform family and is most closely related to the freshwater Ostariophysi. The earliest gonorynchiforms occurred in the Cretaceous of Brazil and west Africa. Chanos occurred in the freshwater Eocene deposits of Europe and North America, and probably invaded the circumtropical Tethys Sea during transgression episodes. At present, milkfish occurs near continental shelves and around oceanic islands throughout the tropical Indo-Pacific. Milkfish populations throughout the range show high genetic variation but low genetic divergence, similar to many other commercially important teleosts. The natural life history of milkfish is one of continual migration. Adults are relatively large (to 1.5 m or 15 kg), long-lived (to 15 years), pelagic and schooling. They spawn offshore near coral reefs or small islands. The eggs, embryos and larvae are pelagic and relatively larger than those of most marine species. Larvae ≥ 10 mm long and 2–3 weeks old move inshore via a combination of passive advection and active migration. Passing shore waters and surf zones, they settle in shallow-water depositional habitats such as mangrove swamps and coral lagoons, where they metamorphose and spend a few months as juveniles. Some juveniles may enter freshwater lakes where they grow into sub-adults but do not mature. Both small juveniles and large sub-adults go back to sea when they reach the size limit supportable by the habitat. Little else is known of the dynamics of wild populations of milkfish. A fishery on inshore larvae supports the centuries-old aquaculture of milkfish in southeast Asia. During the past ten years, milkfish have matured and spawned under various conditions of captivity, and hatcheries have produced larvae to supply the culture ponds. Much remains to be learned concerning the milkfish, particularly its ecology and physiology.     

First report on the spawning migration and early life development of a cyprinid species of the genus Telestes

Reproductive migration of a Telestes species is reported for the first time for the Balkan endemic Telestes pleurobipunctatus (Stephanidis, 1939) from Louros River (Northwestern Greece), while the embryonic and larval development is also described for the first time for this species and genus. Adult fish migrate in late winter upstream and spawn in a peak of 2–3 nights in the outflow of springs. Embryos at hatching measure approx. 6.0 mm notochord length (NL), flexion starts at 8.1 mm NL and food particles are noted in the digestive tract of larvae at 8.2 mm NL. The larval period is characterized by the sequential formation of fins and the development of scalation. Fin differentiation ends with the completion of pelvic fin rays and the disappearance of the pre-anal finfold at 20.0 mm. First scales appear at 17.0 mm standard length (SL) and scalation completes at 27.8 mm SL. We propose that the size at a specific ontogenetic event, the pigmentation pattern and the pre-anal myomeres' number comprise diagnostic characters that permit distinguishing T. pleurobipunctatus larvae from other sympatric cyprinids. We note the rare pattern of scale scalation and pigmentation pattern of the target species. Parapatric speciation in T. pleurobipunctatus possibly related to its spawning migration pattern, as well as the use of larval identification in monitoring and conservation programmes targeting threatened cyprinids exhibiting this type of reproductive behaviour are also discussed.     

Feeding habit of larval and juvenile ayu,Plecoglossus altiyelis in the surf zone of Tosa Bay,Japan

A total of 7,000 larval and juvenilePlecoglossus altivelis was collected at semimonthly intervals with a small seine in a surf zone of Tei beach facing Tosa Bay during the period of June 1982 to May 1983. They occurred in the surf zone from middle October to middle May. About 500 larvae and juveniles (10.9–59.9 mm TL) were used to examine their feeding habit. The feeding incidences by collection dates fluctuated from 0 to 100%, with 90.6% in total incidence. They fed mainly on copepods (e.g.Paracalanus parvus andOithona spp.) throughout postlarval and juvenile stages, while they first took small benthic animals at 53.0 mm TL. Their food compositions were influenced fundamentally by the planktonic fauna of the surf zone, but larvae under 20 mm TL tended to take relatively larger copepods.     

The breeding behavior and the behavior of larvae and juveniles of the sharksucker,Echeneis naucrates

Eleven sharksuckers,Echeneis naucrates, in the Oita Ecological Aquarium spawned from 2 June to 3 December 1974. The spawning behavior began as soon as the lights were turned off. Just before a female spawned, it was driven toward the surface of the water by a group of males. The spawned eggs were pelagic and 2.6 mm in diameter. Approximately 500 eggs were spawned each day. Seventy larvae were hatched on 15 July, and 26 of them were reared until 1 September. We observed the behavior of their larvae and juvenile stages, from the hatching to the attaching phases. The caudal fins of the larvae expanded as they grew. They swam near the bottom with their caudal fins folded. When the sucking disk began to form on the back of a larva’s pectoral fin, it stood still with its caudal fin bent on bottom. After the formation of the sucking disk, a larva would lie on its stomach or back. Some quickly-growing specimens began to stick to the walls, pipes, or plates when they attained 55 mm SL, 35 days after hatching.     

The maturity and breeding season of the bellybarred pipefish, <Emphasis Type="Italic">Hippichthys spicifer</Emphasis>, in Okinawa-jima Island rivers

We investigated the breeding season and size at maturation and described the morphology of newly released Hippichthys spicifer larvae collected from the estuaries of four rivers on northern Okinawa-jima Island, southern Japan. The minimum size of brooding males was 108 mm standard length (SL). The smallest mature female, as estimated from gonadosomatic index (GSI) analysis and histological observations of gonads, was about 100 mm SL. Histological observations showed the gonad of H. spicifer to be a cylindrical tube with a sequential pattern of follicle development and a single germinal ridge. We surmised that the breeding season is year-round, as shown by monthly changes in female GSI, gonad histology, and monthly changes in the occurrence of brooding males. The monthly changes in female GSI and proportions of brooding males were small in winter. The number of eggs in the male brood pouch ranged from 114 to 1,764 (604.4 ± 322.8, mean ± standard deviation; n = 25). The SL of the released larvae was 9.9 mm. All fins except the pectoral fins were formed, the body was elongated, and the developmental stage was similar to that of other Urophori species. The smallest individual present in the mangrove areas of estuaries was 78.0 mm SL.     

Larvae and juveniles of blue drum,Nibea mitsukurii,occurring in the surf zone of Tosa Bay,Japan

A total of 211 larval and juvenileNibea mitsukurii (4.0–19.0 mm SL) was collected with a small seine in surf zones of Tosa Bay during the period of May 1981 to June 1984. They had morphological characteristics common to the larvae and juveniles of Sciaenidae, but were distinguished from the others by the distribution pattern of melanophores on body and spines at the anterior tip of maxillary. They occurred only in surf zone of Tei out of three locations facing Tosa Bay from middle May to middle August. Temperatures and salinities at the place when they were collected ranged from 21.7 to 29.5°C and from 24.5 to 31.3‰, respectively. Good catches were observed when minute dusts floated abundantly in the surf zone. In past studies using traditional larval nets or minnow-nets in coastal or shallow waters of Tosa Bay, larval and juvenileN. mitsukurii were not reported. It seems that they occur in association with minute dusts in extremely shallow waters such as surf zones.     

Expression of cohesin and condensin genes during zebrafish development supports a non-proliferative role for cohesin

Cohesin and condensin are similar, but distinct multi-subunit protein complexes that have well-described roles in sister chromatid cohesion and chromosome condensation, respectively. Recently it has emerged that cohesin, and proteins that regulate cohesin function have additional developmental roles. To further understand the role of cohesin in development, we analyzed the expression of genes encoding cohesin and condensin subunits in developing zebrafish embryos and juvenile brain. We found that cohesin subunits are expressed in a pattern that is similar (but not quite identical) to the expression of condensin subunits. Cohesin genes smc1a, rad21, pds5b and smc3 were expressed in the forebrain ventricular zone, the tectum, the mid-hindbrain boundary, the fourth ventricle, branchial arches, the otic vesicle, the eye and faintly in the developing pectoral fins. Condensin genes smc2 and smc4 were expressed in the forebrain ventricular zone, the tectum, the mid-hindbrain boundary, the fourth ventricle, branchial arches, eye and pectoral fins. Condensin genes were additionally expressed in the hindbrain proliferative zone, an area in which cohesin genes were not detected. A comparison with pcna expression and BrdU incorporation revealed that the expression of cohesins and condensins closely overlap with zones of proliferation. Interestingly, cohesin genes were expressed in non-proliferating cells flanking rhombomere boundaries in the developing brain. In mature brain and eye, cohesin was expressed in both proliferating cells and in broad zones of post-mitotic cells. The distribution of cohesin and condensin mRNAs supports existing evidence for a non-cell cycle role for cohesin in the developing brain.