In vitro steroid production by isolated ovarian follicles of the striped trumpeter

Ovarian follicles from striped trumpeter Latris lineata were incubated in L15 medium alone, or medium supplemented with gonadotropin (GtH) preparations (human chorionic GtH, carp maturational GtH or partially purified salmon GtH), testosterone (T) or 17-hydroxyprogesterone (17P). Levels of oestrone (E₁), 17 β -oestradiol (E₂), T, and 17,20 β -dihydroxy-4-pregnen-3-one (17,20 β P) in the medium after incubation were measured by radioimmunoassay. Basal production of E₂ was high from previtellogenic follicles, whereas little T was produced. Both T and E₂ production increased in response to treatment with GtH or steroid precursors. Vitellogenic follicles showed basal production of both T and E₂, and T but not E₂ levels generally increased in response to hormone treatment. Preparations containing follicles nearing final maturation showed low basal production of E₂ but high production of T. Treatment with steroids resulted in little change in E₂ but often very large increases in T production, whereas GtH stimulated lesser increases. 17,20 β P production was detectable from incubations of maturing follicles from two out of five fish, and in those two incubations, increased in response to treatment with 17P. E₁ was not detectable in any incubations. The results indicate that there is a shift in steroidogenesis from E₂ to T production during oocyte development, and provide further evidence that steroid biosynthesis in non-salmonids is principally regulated by substrate availability.     

Sound production in two carapids (Carapus acus and C. mourlani) and through the sea cucumber tegument

Parmentier, E., Fine, M., Vandewalle, P., Ducamp, J.‐J. and Lagardère, J.‐P. 2006. Sound production in two carapids (Carapus acus and C. mourlani) and throught the sea cucumber teguments. —Acta Zoologica (Stockholm) 87 : 113–119 Carapus acus and Carapus mourlani are able to live inside sea cucumbers and sea stars respectively. Unlike other carapids whose sounds have been recorded (C. boraborensis, C. homei and Encheliophis gracilis), these two species have a central constriction in their swimbladder and are unlikely to encounter heterospecific carapids within their hosts. We evoked sound production in Carapus acus and Carapus mourlani by adding several individuals to a tank with a single host and found that their sounds differ substantially from the sounds emitted by other carapids in pulse length, peak frequency and sharpness of tuning (Q_3 dB). Unlike the other carapids, C. mourlani and C. acus produce shorter and less repetitive sounds and do not produce sounds when they enter their host. Since sounds produced within a sea cucumber have the potential to be heard by distant carapids and are typically recorded outside the sea cucumber, we examined the effect of the sea cucumber tegument on acoustic transmission. Attenuation by the tegument was negligible at the frequencies within carapid sounds. Therefore, carapids have the potential to call from the relative safety of a sea cucumber without sacrificing the distance over which their transmissions are heard.     

Development of the respiratory swimbladder of Pangasius sutchi

The swimbladder of Pangusius sutchi first appears on the dorsal surface of the oesophagus at about 5 days after hatching. The swimbladder has double chambers when it is separated by a medial septum at 8–10 days. Alveoli start to develop and function in air-breathing at 12–14 days. Their number is increased by subdivision, and the respiratory portion grows towards the centre. Morphometric analysis shows that the swimbladder increases in respiratory surface, volume and surface area: volume ratio during development. On a histological basis, the development of the swimbladder is divided into three distinct periods: a blind tube, a double chamber and an alveolus period. It is characteristic that the flat epithelial cell arises from a primordial cuboidal cell and that a double capillary system is arranged in the interalveolar septa. Multilamellar bodies appear and a blood-air barrier is established when the swimbladder becomes functional.     

Structure and volume of the hoki, Macruronus novaezelandiae (Merlucciidae), swimbladder

The structure of the hoki, Macruronus novaezelandiae , swimbladder is similar to well-developed swimbladders in other deep water fish that undergo extensive diel vertical migrations. The preponderance of a globular mass of submucosal tissue in the posterio-ventral floor of the swimbladder in large individuals is an unusual feature of unknown function, but has characteristics similar to regressed swimbladders that occur in some species of the Myctophidae. Two out of three different estimates of swimbladder volume were significantly lower than 'neutral buoyancy volume' estimates, probably because the swimbladders were inflated artificially without accounting for their natural compliancy and internal pressure. Volume estimates from such swimbladders may reduce substantially the accuracy of target strength estimates from morphometry-based models of the swimbladder. However, this may be a trivial consideration in acoustic surveys compared to the probable occurrence of diel and seasonal variation in swimbladder shape and volume.     

Swimbladder form in clupeoid fishes

The general form of the swimbladder is described and illustrated for representatives of 50 out of the 82 genera of clupeoid fishes (families Chirocentridae, Clupeidae, Pristigasteridae and Engraulididae of the suborder Clupeoidei), based mainly on preserved specimens. There is a remarkable diversity of shape, volume and silvering, as well as many curious specializations. The point of origin of the pneumatic duct from the gut, the presence or absence of an anal duct, and the length and diameter of the pre-coelomic ducts are noted, with attempts to explain their functional significance in terms of feeding and vertical migration. Specializations such as dorsal or lateral pockets, post-coelomic diverticula and internal muscular processes may be connected with sound production. The taxonomic implications of this diversity of swimbladder form are explored but, while some intra-and intergeneric relationships arc either confirmed or challenged, the swimbladder gives little help at suprageneric levels.     

Swimbladder form in clupeoid fishes

The general form of the swimbladder is described and illustrated for representatives of 50 out of the 82 genera of clupeoid fishes (families Chirocentridae, Clupeidae, Pristigasteridae and Engraulididae of the suborder Clupeoidei), based mainly on preserved specimens. There is a remarkable diversity of shape, volume and silvering, as well as many curious specializations. The point of origin of the pneumatic duct from the gut, the presence or absence of an anal duct, and the length and diameter of the pre-coelomic ducts are noted, with attempts to explain their functional significance in terms of feeding and vertical migration. Specializations such as dorsal or lateral pockets, post-coelomic diverticula and internal muscular processes may be connected with sound production. The taxonomic implications of this diversity of swimbladder form are explored but, while some intra-and intergeneric relationships arc either confirmed or challenged, the swimbladder gives little help at suprageneric levels.     

Isolation and characterization of microsatellite markers in the striped hamster (Cricetulus barabensis)

A total of 14 polymorphic microsatellite markers were isolated and characterized from the striped hamster, Cricetulus barabensis, a widespread rodent pest in northern China. Two to six alleles per locus were detected in 90 individuals from three locations in Shandong Province, China. The observed and expected heterozygosities ranged from 0.21 to 0.78 and from 0.30 to 0.80, respectively. These microsatellite markers provide new tools for investigating the population structure of this species.     

宝石鱼(Hemichromis bimaculatus)气鳔的听觉机能

在宝石鱼内耳分別记录了切除气鳔前后的微音器电位。以20μV 微音器电位反应为阈值的听力图表明宝石鱼的内耳能接受50—500Hz 的声音信号,最高敏感度在50—200Hz 之间。气鳔完整的宝石鱼,微音器电位幅度与刺激声压强度成比例。气鳔切除后,在50Hz,200—300Hz 之间,声压敏感度下降5—6dB,表明宝石鱼的气鳔有辅助的听觉作用。     

The ears of butterflyfishes (Chaetodontidae): ‘hearing generalists' on noisy coral reefs?

Analysis of the morphology of all three otolithic organs (sacculus, lagena and utriculus), including macula shape, hair cell morphology, density, orientation pattern, otolith morphology and the spatial relationships of the swimbladder and ear, reveals that butterflyfishes in the genera Chaetodon (which has anterior swimbladder horns) and Forcipiger (which lacks anterior swimbladder horns) both demonstrate the ear morphology typical of teleosts that lack otophysic connections, fishes that have traditionally been considered to be 'hearing generalists'.