Aspects of the Feeding and Reproductive Biology of the Lake Tanganyikan Cichlid, Lamprologus ornatipinnis (Pisces, Cichlidae)

This project investigated the reproductive and feeding biology of Lamprologus ornatipinnis. Specimens were collected monthly from North Bay, Mbita Island, Zambia for a year. Dentition was examined under a scanning electron microscope, stomach contents were analysed using the Index of Relative Importance (IRI) and mean Gonado-somatic Indices (GSI) were calculated for each month to reveal spawning peaks. Both males and females possess an outer row of six (premaxilla) and eight (dentary) enlarged canines. The remaining inner rows consist of small, recurved canine-like teeth. The lower pharyngeal bone possesses enlarged centrally placed molars with an increasing number of smaller bevelled teeth laterally. This dentition is very similar to a typical benthic arthropod and mollusc eater. Stomach content analysis revealed that L. ornatipinnis feeds predominantly on Chironomidae, Copepoda and Ostracoda. The importance of these prey items in the diet differed significantly between the months sampled. Percentage volume of Copepoda and Cyclopoida was greater in female stomachs than males and the % number of Chironomidae greater in males than females. Gonadosomatic Index (GSI) values indicated males and females breed throughout the year. Females, however have a significant peak (p<0.05) in breeding activity from July to October that coincides with the increased abundance of plankton at this time.     

Contrbtion to the biology of Zagros tooth-carp, <Emphasis Type="Italic">Aphanius vladykovi</Emphasis> (Cyprinodontidae) in central Iran

We studied some aspects of the biology of the Zagros tooth-carp, Aphanius vladykovi, an endemic and poorly known species from Chahar-Mahall-va-Bakhtiari province in central Iran, by regular monthly collections and direct observation in aquaria over a full year. We collected individuals from Modar-Dokhtar spring of Gandoman region; we preserved some in formalin and transferred some alive to aquaria. The stomach contents consisted mostly of freshwater crustaceans, suggesting a carnivorous habit. The eggs had an average diameter of 1mm and the average absolute and relative fecundity was 415 and 110, respectively. The gonadosomatic ratio and ovary condition suggested that the reproductive season of the species was between late March and June with a peak in early April. The species is euryhaline and eurythermal and prefers neutral to basic waters. It is usually found in well-oxygenated waters, but is tolerant of hypoxia as well.     

Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species

Across species, there is usually a positive relationship between sperm competition level and male reproductive effort on ejaculates, typically measured using relative testes size (RTS). Within populations, demographic and ecological processes may drastically alter the level of sperm competition and thus, potentially affect the evolution of testes size. Here, we use longitudinal records (across 38 years) from wild sympatric Fennoscandian populations of five species of voles to investigate whether RTS responds to natural fluctuations in population density, i.e. variation in sperm competition risk. We show that for some species RTS increases with density. However, our results also show that this relationship can be reversed in populations with large-scale between-year differences in density. Multiple mechanisms are suggested to explain the negative RTS–density relationship, including testes size response to density-dependent species interactions, an evolutionary response to sperm competition levels that is lagged when density fluctuations are over a certain threshold, or differing investment in pre- and post-copulatory competition at different densities. The results emphasize that our understanding of sperm competition in fluctuating environments is still very limited.     

Reproductive Biology and Ecology of Shortspine Thornyhead Rockfish, Sebastolobus alascanus, and longspine thornyhead rockfish, S. altivelis, from the northeastern Pacific Ocean

We examined the reproductive biology and estimated life history parameters for female shortspine thornyhead, Sebastolobus alascanus, and longspine thornyhead, S. altivelis, from histological samples prepared from specimens collected from both Alaska and the West Coast of the United States. Both species spawn pelagic gelatinous egg masses, although timing differs between taxa and locations. Shortspines spawn between April and July in Alaska and between December and May along the West Coast. Longspines spawn between January and April along the West Coast. Length at 50% maturity differed between species and areas, with shortspines at 21.48cm in Alaska and 18.19cm on the West Coast, and longspines at 17.83cm on the West Coast. We used the gonadosomatic index to estimate instantaneous rates of natural mortality (M). Values of M differed little between species and areas despite substantial differences in temperature and dissolved oxygen concentrations. Estimates for shortspines from both Alaska and the West Coast ranged between 0.013 and 0.017, while longspines from the West Coast showed an M value of 0.015. Such low estimates of M suggest Sebastolobus are extremely long-lived.     

Complex spermatozoon of the live-bearing half-beak,Hemirhamphodon pogonognathus (Bleeker): Ultrastructural description (Euteleostei,Atherinomorpha, Beloniformes)

The spermatozoon of Hemirhamphodon pogonognalhus shows modifications that are frequent though not obligate in internally fertilizing sperm, notably elongation of the nucleus and extension of the mitochondria of the midpiece as an elongate sheath around the proximal region of the axoneme. These similarities to poecilid and jenynsid sperm are considered homoplasic. As in the mature sperm of all but one investigated teleost, an acrosome is absent. The elongate, blade-shaped, electron-dense nucleus has a mean length of 3.2 μm; its basal implantation fossa, less than one-tenth of the length of the nucleus, houses the anterior half of the distal and only centriole (of triplet construction with satellite rays), a centriolar plug, and a mass connecting the centriole to the wall of the fossa. A unilateral putative centriole adjunct is present. The anterior region of the axoneme is surrounded by a mitochondrial sleeve, and internal to this, separated by a cisterna, by a submitochondrial sleeve. The mitochondrial sleeve unites posteriorly with the submitochondrial sleeve. Between the submitochondrial sleeve and the axoneme is a space, the cytoplasmic canal, that is open to the exterior posteriorly. The discrete, cristate mitochondria, in their sleeve, are unique in investigated atherinomorph sperm in being bilateral, grouped on only two opposing sides of the axoneme, with an arc-shaped ‘intermitochondrial link’ between. The 9 + 2 flagellum is unique for the Animalia in having 23 radial subplasmalemmal rods, repeated longitudinally (periodicity 0.025 pm) in a quasicrystalline array. Internal fertilization is deduced to have arisen in the Exocoetoidei independently of that in the Cyprinidcntiformes.     

c-Abl proto-oncoprotein is expressed and tyrosine phosphorylated in human sperm cell

The presence and possible role of c-Abl proto-oncoprotein was investigated in human sperm cell. The c-Abl monoclonal antibody (mAb), against the protein tyrosine kinase domain of v-Abl protein, reacted specifically with the acrosomal region of methanol-fixed capacitated and non-capacitated human sperm cell in the indirect immunofluorescence technique. The c-Abl mAb predominantly recognized two protein bands of 145 kD and 95 kD in detergent-solubilized (Triton X-100 and NP-40) sperm and testes preparations in the Western blot procedure. The 95 kD protein band reacted stronger than the 145 kD band and was the only band detected in the lithium diiodosalicylate (LIS)–solubilized sperm preparation, and even in the Triton X-100/NP-40 extracts of sperm of some men. In the in vitro kinase assay using the Triton X-100–solubilized capacitated sperm preparation, the 95 kD protein was autophosphorylated at the tyrosine residues, which was inhibited in the presence of c-Abl mAb. The tyrosine phosphorylation of sperm proteins, especially of the 95 kD protein, has been shown to have a vital role in human sperm function, namely, the sperm capacitation/acrosomal exocytosis and binding to zona pellucida of oocyte. These findings suggest that the c-Abl or c-Abl-like proteins are present in mature sperm cells that are tyrosine autophosphorylated and may have a role in human sperm cell function. Mol. Reprod. Dev. 51:210–217, 1998. © 1998 Wiley-Liss, Inc.     

Annual cycles of growth and reproduction in hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus, raised on forage or pelleted diets

Annual cycles of growth and reproduction of hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus , were investigated. Animals were raised on either forage (goldfish, Carassius auratus ) or a pelleted salmon feed. Male and female year–class 1 largemouth bass were sampled throughout one complete yearly cycle (January–December). A biphasic growth cycle was observed in both forage–fed and pellet–fed fish. No increase in body length or weight was observed until approximately midway through the spawning period (May), after which fish grew at a consistent rate for the remainder of the study. The reproductive cycle of forage–fed fish was characterized by a rapid increase in gonadosomatic index (GS1) between January and April, followed by a prolonged spawning period (April–July) during which GSI progressively declined. Fully regressed gonads were observed in September and October, and a resumption of gonadal recrudescence was observed between October and December. Visceral adipose deposits (expressed as mesenteric fat index; MFI) were resorbed during gonadal growth and the initial stages of the spawning period, and restored during the post–spawning phase. Fish raised on pelleted feed had growth and reproductive cycles that parallelled those of forage–fed fish, but several significant differences were observed between the two diet groups. During the growth phase of the cycle, pellet–fed largemouth bass grew significantly faster than forage–fed largemouth bass, and had significantly larger MFIs than forage–fed largemouth bass at all times of the year. Pellet–fed fish also had significantly larger GSIs than forage–fed fish. These data indicate that diet composition may be an important determinant of growth and reproductive function in this species.     

A new method to determine sex and gonad size in live fishes by using ultrasonography

A method to determine, non-invasively, sex and gonad size employing ultrasonography and using Atlantic salmon, Salmo salar Linnaeus, as an example, is described. Although gonads of immature males may be difficult to discern, gonads of females are always visible and hence sexing is possible by deduction. Gonad diameter can be estimated by ultrasonography; the correlation coefficients between ultrasonographic and ruler-derived measurements were 0.926 for females and 0.754 for males. The appearance of ultrasonographic images of the gonads during sexual maturation are described. The results are discussed and suggestions made to improve the quality of images and reliability of measurements.     

Effect of Season and Age on the Gonadosomatic Index of Milne-Edwards' Sifakas (Propithecus diadema edwardsi) in Ranomafana National Park,Madagascar

Aiming to explain individual variation in gonadosomatic index (testicular volume per body weight), we examined the relationship between gonadosomatic index (GI), age, and season in a wild, seasonally breeding lemur—the Milne-Edwards' sifaka (Propithecus diadema edwardsi). Between 1987 and 2000, we captured and measured male lemurs from Ranomafana National Park in Madagascar 69 times. We used linear and polynomial regressions and residuals to examine the effect of season on GI and the effect of age on GI, after accounting for the effect caused by season among males of breeding age. As the breeding season approached, GI increased significantly, and all individuals measured in both the breeding and nonbreeding season had larger GI values in the breeding season. Among males of breeding age, we found no relationship between age and GI, after accounting for seasonal effects. Age, season and body weight fail to explain the variation remaining in GI. We discuss sperm competition, breeding-group composition, and the presence of parents as additional sources of variation in GI.     

Allozyme comparison of two populations of Rineloricaria (Siluriformes, Loricariidae) from the Ivaí River, upper Paraná River basin, Brazil

Two allopatric morphotypes of the genus Rinelocaria were compared through the allozyme electrophoresis technique: one morphotype, R. pentamaculata, from the Keller River in the middle stretch of the Ivaí River basin and the other, R. aff. pentamaculata, from the São João River in the upper portion of the Ivaí River basin. The morphotype from the São João River was collected upstream from the São João waterfall, which is about 80 m deep. Twelve enzymatic systems (AAT, ADH, EST, GCDH, G3PDH, GPI, IDH, LDH, MDH, ME, PGM and SOD) were analyzed, which allowed to score 22 loci. Only lociAat-2, Est-3 and Mdh-C showed polymorphism. The two samples differed in allele frequencies at the three polymorphic loci. The average expected heterozygosity for all loci was 0.0806 ± 0.0447 in the Keller River sample. For the São João River morphotype, this value was 0.0489 ± 0.0350. Nei'' s genetic identity and distance between the two populations were respectively 0.9789 and 0.0213. Wright''s F_IS , F_IT and F_ST over all loci were estimated as 0.3121, 0.4021 and 0.1309, respectively. We consider that the two morphotypes represent species in statunascendi.     

南盘江马别河三齿拟缨鱼繁殖生物学特性

三齿拟缨鱼（Pseudocrossocheilus tridentris）是中国特有的一种野鲮亚科鱼类。本研究于2019年春、夏、秋三个季度在南盘江一级支流马别河采集了206尾三齿拟缨鱼;研究了其雌雄比例、性腺发育、性成熟系数、性成熟大小、卵径特征以及繁殖力。结果表明:三齿拟缨鱼雌雄比例接近1∶1（P>0.05）;雌性性成熟个体在整个调查期间均有发现;其中4—6月雌性性成熟个体占比均在80%以上;性成熟系数显著高于其他采样月份（P<0.05）;采用Logistic回归方程获得雌、雄初次性成熟体长（SL₅₀）分别为136.5和134.3 mm;三齿拟缨鱼绝对繁殖力和相对繁殖力的平均值分别为1039粒·尾^-1和18粒·g^-1;绝对繁殖力与体长和空壳重呈正相关;Ⅲ、Ⅳ、Ⅴ期的卵径频率分布均呈单峰型;推测三齿拟缨鱼为单批次产卵型鱼类。三齿拟缨鱼是一种性成熟个体小、绝对繁殖力较低、单批次产卵型鱼类;属于典型的机会主义。研究结果可以为三齿拟缨鱼资源保护和人工繁殖提供基础资料。