Genetic evidence for historical continuity between populations of the Australian freshwater fish Craterocephalus stercusmuscarum (Atherinidae) east and west of the Great Dividing Range

The freshwater Craterocephalus stercusmuscarum (Atherinidae) has a broad northern and south-eastern Australian distribution, and has been divided into two sub-species. Craterocephalus stercusmuscarum fulvus occurs in eastern and western flowing drainages of the southeast, while C. s. stercusmuscarum occurs in north eastern and northern flowing drainages. Four populations of each sub-species were sampled from different river systems to examine if genetic diversity was consistent with this nomenclature or a previously proposed vicariance hypothesis. Allozyme data did not support the notion that the subspecies were genetically distinct, but the mtDNA data showed that haplotypes from one sub-species, regardless of geography, were reciprocally monophyletic to haplotypes of the other subspecies. Thus, mtDNA genetic diversity was partitioned by prevailing taxonomy and the data suggest that C. s. fulvus populations in eastern and western flowing drainages may have had a relatively recent connection subsequently interrupted by geological events.     

Feeding strategies in drosophilid parasitoids: the impact of natural food resources on energy reserves in females

1. Adult feeding strongly increases longevity and fecundity in parasitic wasps. Searching for food resources involves costs; therefore, it is advantageous to be able to feed on the breeding substrate.
2. Cohorts of females of four drosophilid parasitoid species were assigned to different food treatments including starvation. Fat contents were measured and compared after 5 days. In this way the nutritional value of breeding substrates to females could be expressed in terms of energy reserves.
3. Three of the four species tested fed on natural breeding substrates. A fourth species did not produce evidence of such feeding. However, this species fed on honey when fat reserves were low.
4. Feeding is related to: (i) the species' natural breeding substrate, (ii) the energy allocation and lifetime expectancy of the female, and (iii) time of the season.
5. Because feeding strongly influences longevity and fecundity, it is argued that the different feeding strategies found may affect competitive relationships between these drosophilid parasitoid species.     

Warm Springs,Early Lay Dates,and Double Brooding in a North American Migratory Songbird,the Black-Throated Blue Warbler

Numerous studies have correlated the advancement of lay date in birds with warming climate trends, yet the fitness effects associated with this phenological response have been examined in only a small number of species. Most of these species–primarily insectivorous cavity nesters in Europe–exhibit fitness declines associated with increasing asynchrony with prey. Here, we use 25 years of demographic data, collected from 1986 to 2010, to examine the effects of spring temperature on breeding initiation date, double brooding, and annual fecundity in a Nearctic - Neotropical migratory songbird, the black-throated blue warbler (Setophaga caerulescens). Data were collected from birds breeding at the Hubbard Brook Experimental Forest, New Hampshire, USA, where long-term trends toward warmer springs have been recorded. We found that black-throated blue warblers initiated breeding earlier in warmer springs, that early breeders were more likely to attempt a second brood than those starting later in the season, and that double brooding and lay date were linked to higher annual fecundity. Accordingly, we found selection favored earlier breeding in most years. However, in contrast to studies of several other long-distance migratory species in Europe, this selection pressure was not stronger in warmer springs, indicating that these warblers were able to adjust mean lay date appropriately to substantial inter-annual variation in spring temperature. Our results suggest that this North American migratory songbird might not experience the same fecundity declines as songbirds that are unable to adjust their timing of breeding in pace with spring temperatures.     

Reproductive biology of Gambusia affinis holbrooki Baird and Girard, Xiphophorus helleri (Gunther) and X. maculatus (Heckel) (Pisces; Poeciliidae) in Queensland, Australia

The reproductive biology of three introduced Poeciliidae, Gambusia affinis holbrooki Baird and Girard, Xiphophorus helleri (Günther) and X. maculatus (Heckel) was studied over a 14-month period in Brisbane, Queensland. Photoperiod and water temperature determined the length of the breeding season in G. affinis , which produced up to nine broods between August and March, with the peak of reproductive activity in October. Fecundity was linearly related to body weight in G. affinis (mean fecundity = 22.78 ± 1.02, range = 3–108 offspring per brood).
Xiphophorus helleri bred from August to May, producing eight to nine broods, with peak reproductive activity from October to December. Fecundity was curvilinearly related to body weight (mean fecundity = 60.15 ± 3.8, range = 7–183 offspring per brood. Xiphophorus maculatus bred between September and March, producing five to six broods during the study period. Fecundity was linearly related to standard length (s.l.) (mean fecundity = 27.27 ± 2.4, range = 3–92 offspring per brood). Although the reproductive strategy of the three species differs, all have the capacity to build up large populations in south-eastern Queensland. Their present distributions and relative abundance are discussed.     

Age, growth and natural mortality rates of some cichlid fishes of Lake Malawi

The growth rates, lengths at maturity, fecundity and natural mortality of several cichlids of importance in trawl catches in Lake Malawi are described. Growth rates were determined by analysis of length frequency data from trawl catches. The breeding season for each species was determined by monthly examination of the gonads, and fecundity determined by egg counts from ripe ovaries. Lengths at maturity were calculated from the proportion of mature fish during breeding seasons. Natural mortality rates were determined from length frequency data from an unfished area of the lake. Values of the growth constant K ranged from 0.487 to 0.671. The ratio of length at maturity to asymptotic length varied from 0.56 to 0.82. Growth parameters are compared with those of other cichlids. Most species mature in their third year. Fecundity was proportional to the square of the length in four of the five species. The species studied appeared to produce only one batch of eggs per breeding season. Instantaneous natural mortality rates ranged from 0.92 to 1.69.     

Seasonal and individual variation in gregarine parasite levels in the field crickets Gryllus veletis and G.pennsylvanicus

ABSTRACT. 1. Gregarines, debilitating protozoan gut parasites, were monitored in two species of field cricket, Gryllus veletis (Alexander and Bigelow) and G.pennsylvanicus Burmeister, in northern Michigan in 1983 and 1984.
2. Gregarines were found in 31–51% of G.veletis individuals and 50–70% of G.pennsylvanicus.
3. Males were more heavily infected than females in G. veleris , but G.pennsylvanicus males and females had nearly equal infection levels; this disparity resulted in an overall lower infection rate for G. veletis.
4. Both species had fewer gregarines in 1983 than in 1984, possibly due to the adverse effect of drier conditions in 1983 on development of parasite cysts in the soil.
5. Levels of infection were not constant throughout the breeding season for either cricket species.
6. Body size was not correlated with parasite load in either G. veletis or G.pennsylvanicus.
7. Adult age was unrelated to gregarine level in G. veferis , whereas G.pennsylvanicus showed a positive correlation between adult age and parasite load during two non-consecutive weeks of the breeding season.     

Seasonal patterns in species richness of herbivores: Macrolepidopteran larvae on Finnish deciduous trees

Abstract. 1. The seasonal distribution of macrolepidopteran species richness on Finnish deciduous trees vaned from positively skewed (peak in spring) to negatively skewed (peak in autumn).
2. The skewness values of species richness had a significant negative correlation ( r = - 0.98) with the duration of the seasonal shoot-growth period of the tree species.
3. Trees which complete their shoot growth early in the season ( Quercus type) produce new leaves only during spring, while trees whose shoot growth continues to autumn ( Populus type) do so throughout the summer.
4. Consequently, there is a difference in the number of available resources in the late summer foliage of different tree species, Trees ceasing leaf production early such as oak ( Quercus robur ) and bird cherry ( Prunus padus ) have one major resource type (mature leaves) in late-season foliage while trees like birches and alders have two Ooung and mature leaves).
5. Because young leaves formed late in the season are preferred to mature ones by some species of herbivores and because other species prefer mature leaves at the same time, the species richness of Populus-type trees is higher later in the season than the species richness of Quercus-type of trees, which have just one type of resource available.     

Effects of temperature and food quality on life-history parameters in Parameletus chelifer and P. minor (Ephemeroptera): a laboratory study

SUMMARY. 1. Growth rate of Parameletus minor was greatest between 10.8 and 19.8°C, survival rate peaked at 5.9°C, developmental time was shortest at 14.6°C, and adult size and fecundity reached maximum values between 5.9 and 10.8°C. Growth rate of P. chelifer was greatest between 14.6 and 19.8°C, survival rate peaked at 5.9°C, and developmental time was shortest at 14.6°C. A large adult size was found at 10.8°C, and highest fecundity between 10.8 and 14.6°C.
2. Food quality significantly affected growth rate, developmental time, adult size and fecundity of both species. Both P. chelifer and P minor attained highest growth rate, largest adult size and highest fecundity when the C/N ratio of food was 5.95. Developmental time was shortest at a C/N ratio between 5.95 and 12.8.
3. Nymphs of P. chelifer had a higher temperature 'optimum' for growth than nymphs of P. minor . Growth rate of nymphs of P. chelifer reared on detritus from a seasonal stream (C/N ratio 12.8) was about 3 times that of nymphs reared on detritus from a river margin (C/N ratio 20.9). The corresponding growth rate difference for nymphs of P. minor was only about 1.5.
4. When all life-history parameters are taken into consideration, P. chelifer had a higher temperature 'optimum' than P. minor .     

On the biology of the catfish Chrysichthys auratus (Geoffory) in the man-made Tiga Lake in Northern Nigeria

SUMMARY. (1) A study was made of the biology of Chrysichthys auratus , a bottom-feeding omnivore, in Tiga Lake, a man-made lake in Northern Nigeria.
(2) Ripe females were present from April to September, coinciding with the hot season and rise in water level. First spawning took place at age II in females. No ripe males were found, and this was attributed to their spatial separation. Absolute fecundity was related to length and ranged from 327 to 1466 in forty-six females.
(3) Hyaline rings on the centra of lumbar vertebrae were counted to age 235 fish. The first ring is laid down at the end of the second year, after which the rings were formed annually, probably during the breeding season. The fish live for up to 6 years. There is a good fit of the growth curve to the von Bertalanffy equation. Growth is slow and a smaller maximum size is attained than in rivers.     

Plasticity responses of an invasive macrophyte species to inorganic carbon availability and to the interaction with a native species

The acorn barnacle Perforatus perforatus has a defined breeding temperature range and reproductive season that varies geographically. This study aims to investigate the influence of reproductive parameters of P. perforatus in species distribution ranges in the NE Atlantic. The hypothesis tested is that the breeding season of P. perforatus off NW Portugal begins earlier and is longer than at the northern distribution limit of this species, and that fecundity is higher in terms of number of broods per individual per breeding season. The span of the breeding season and fecundity indices were assessed based on the presence and maturation of ovigerous lamellae and correlated with temperature. Results showed that the breeding season in the NW Portuguese coast lasts over 10 months (February–November) and the number of broods was determined to be 9.2 ind/year. Temperature seems to be a primary factor determining the breeding season, but other factors, such as food availably, light and photoperiod, are also of great importance. However, the higher quantity of embryos produced in NW Portugal is not reflected in a higher abundance of settled adults in rocky shores. Contrarily, the species is particularly abundant in artificial substrata offshore.     

Spawning periodicity and annual breeding seasons of Tilapia nilotica (L.) in the White Nile

Two annual breeding seasons are indicated for populations of T. nilotica in the White Nile: a major autumnal season (mid-July–September) coinciding with the annual rainfall and a smaller back-up season in February–March. During these seasons reproducing females constituted 80% and 40% of the total population of mature females compared to 10–12% in the intervening summer period. Enhanced gonadal development, fecundity and GSI values characterized the breeding seasons. Gonadal maturation proceeded uninterruptedly even during the summer and repeated fractional spawning is suggested for this species within and beyond the breeding seasons. Most of the spring breeders were either very young or relatively old fish and most medium-sized females bred in the main autumnal season. Older fish were less fecund (by 70–75%) compared to younger fish. In the latter, fecundity increased progressively with body growth (r² = 0.732; p<0.001); the proportionality was lost in medium-sized fish and in older females (0.9–1.5 kg) fecundity correlated negatively with increased body size.     

A hierarchical response to differences in ration size in the reproductive performance of female three-spined sticklebacks

The response of female three-spined sticklebacks ( Gasterosteus aculeatus ) to differences in food ration during the breeding season was quantified for several variables related to reproductive performance. The measured protein and lipid contents (mg g⁻¹) of eggs were unaffected by ration. Egg size increased with an increase in both ration and female size, but the proportional increase in egg size was much smaller than the proportional increase in ration. The best predictor of mean batch (clutch) fecundity and weight was female size. There was a small but significant increase in batch fecundity with ration, but the increase was not directly proportional to the increase in ration. The rate of spawning, total breeding season fecundity and total weight of eggs spawned over the breeding season were sensitive to ration with breeding season fecundity and weight increasing in direct proportion to ration. Thus, in female sticklebacks, there is a hierarchy of sensitivity to ration in the response of variables related to reproduction.     

THE BREEDING SEASONS OF AFRICAN BIRDS—2. SEA BIRDS.

1. All the available data, largely unpublished, are assembled for sea-birds breeding in African waters, about 36° N.-36° S.
2. An ill-defined breeding season by any species at any station is exceptional.
3. North of the Equator practically all sea-birds breed in spring or summer.
4. South of the Equator there is much more variation. Round the Cape there is a good deal of mid-winter breeding, mainly in stations affected by the warm Agulhas current.
5. On the east coast most of the breeding takes place in the period June–August from the Gulf of Suez (27° N.) to the mouth of the Zambesi (19° S.) and beyond, i.e. in the hottest months north of the Equator and the coolest months south of it.     

Daily age determination and growth rates of freshwater fish throughout a regulated lotic system of the Murray‐Darling Basin Australia

To facilitate future research in freshwater fish recruitment response to environmental flow delivery, size‐at‐age and growth models are presented for eight fish species occurring in south‐eastern Australia; three small‐bodied species and the juvenile 0+ age classes of five large‐bodied species. Otolith increments were used to estimate the daily age of golden perch Macquaria ambigua, bony bream Nematalosa erebi, common carp Cyprinus carpio; Murray cod Maccullochella peelii, freshwater eel‐tailed catfish Tandanus tandanus, Australian smelt Retropinna semoni, un‐specked hardyhead Craterocephalus stercusmuscarum fulvus and Murray–Darling rainbowfish Melanotaenia fluviatilis. Linear growth models provided the best fit for length‐at‐age data of juvenile 0+ age large‐bodied species; whereas von Bertalanffy growth functions provided the best fit to length‐at‐age data of small‐bodied species. The results provide novel baseline data for future research in this area.     

Delayed maturation in female bank voles: optimal decision or social constraint?

1. Density, maturation and survival of female bank vole ( Clethrionomys glareolus ) in the northern taiga of Finnish Lapland were studied using long-term capture–mark–recapture data from two large grids, one food-addition grid and one control grid, in 1982–94.
2. The density on the food grid was consistently higher than the density on the control grid.
3. Females born early in the breeding season usually matured, except at very high densities. Those born later in the summer season commonly delayed maturation to the following spring.
4. Winter survival of sub-adult (having delayed maturation) females was significantly higher than survival of adult (breeding) females. However, empirical values of sub-adult and adult survival, as well as difference between them, were not consistent with survival values assumed in theoretical models on optimal deferred breeding.
5. There was a density-dependent relationship between the maturation rate of young voles and the density of already established breeding females (both bank voles and all Clethrionomys together; C. rutilus and C. rufocanus occasionally occurred on the study grids). This density dependence was different for the two grids (weaker on the food-addition grid).
6. These findings are discussed within an evolutionary context: we have, on the basis of these findings, no evidence suggesting that the observed delayed maturation represents an evolutionary optimal strategy. Rather, there is evidence suggesting that the delay is due to social constraints.     

The development of photorefractoriness in termination of the breeding season in the tropical brahminy myna: role of photoperiod

Gonads of brahminy myna (Sturnus pagodarum) spontaneously regress in July/August when the daylength is still stimulatory. Experiments were conducted to investigate if photoperiod was involved in the timing of gonadal regression and if photorefractoriness terminated the breeding season in this species. The observations obtained in the present study clearly show that: i) increasing photoperiods of spring/summer programmed for eventual gonadal regression in the late summer; ii) the birds developed photorefractoriness to all stimulatory daylengths and consequently the breeding season could not be extended by providing more stimulatory photoperiods; and iii) exposure to short daylength treatment failed to overcome the onset of refractoriness in birds after they had attained full gonadal growth and development. These results suggest that refractoriness is a process used by the brahminy myna to terminate the breeding season, and that this species becomes totally photorefractory.     

Comparative study of sexual cycles, oogenesis and spawning of two Soleidae, Solea lascaris (Risso, 1810) and Solea impar (Bennet, 1831), on the western coast of Brittany

Two sand sole species, Solea lascaris and Solea impar , are common on the western coast of Brittany, France. Their reproduction (oogenesis and spawning) has been studied by following the gonadosomatic index, histological changes in ovary development, and oocyte diameter distribution. Both species have a prolonged spawning season, from spring to late summer. Each mature female breeds twice during the spawning season: in May and July for 5. lascaris , and in early June and July for 5. impar. Throughout the spawning season, several oocyte batches undergo vitellogenesis and there is a continuous recruitment of immature or primary oocytes into vitellogenesis. The two species are thus serial synchronous spawners. This, together with oocyte atresia late in the season (especially noticeable in S. impar ) makes fecundity estimation difficult.     

The effects of rainfall on different components of seasonal fecundity in a tropical forest passerine

Seasonal fecundity is a composite metric that is determined by component parameters such as clutch size, nest survival and re‐nesting probability. Many of these component parameters are known to vary with environmental conditions, in particular rainfall prior to or during the breeding season. In some species, seasonal fecundity is positively related to rainfall, but little is known about which component parameters of seasonal fecundity respond most strongly to rainfall. We used intensive nest monitoring of a multi‐brooded tropical forest passerine, the Montserrat Oriole Icterus oberi, to examine the effects of rainfall during the pre‐breeding season on component parameters of annual fecundity. We monitored all nests of a total of 42 pairs over 5 years in which rainfall varied substantially. We then related clutch size, nest survival, onset and length of the breeding season, re‐nesting probability and re‐nesting interval to pre‐breeding season rainfall using generalized linear mixed models that accounted for random variation across sites and individual pairs, and incorporated other variables known to affect the response. Higher pre‐breeding season rainfall led to an increase in clutch size and a decrease in re‐nesting interval, but nest survival, re‐nesting probability and length of the breeding season were not affected by variation in rainfall. The onset of the breeding season was delayed in very dry years. We conclude that higher rainfall is likely to increase food availability and thus body condition of female Montserrat Orioles, leading to an increase in fecundity due to larger clutch sizes.     

Growth rate of the aquatic moss Rhynchostegium riparioidesin Northern England

SUMMARY 1. The rale of shoot growth in Rhynchostegium riparioides was measured at monthly intervals over a 12-month period at four upland sites in the Northern Pennines. Changes were recorded by observations attached pieces of cotton. Detectable growth was found in each month, with the maximum in spring (up to 2.31 mm week⁻¹) and minimum in winter (1.12 mm week⁻¹); there was a second smaller peak in the autumn.
2. Growth rate was related strongly to several environmental variables, including spot measurements of water temperature (positive) and mean monthly precipitation (negative). A regression equation based on these two variables accounted for 5% of the variation recorded.
3. Total shoot growth over the 12-month period ranged from 33.4 to 73.3 mm, corresponding to an increase in mass of 22.9 and 120.8 mg, respectively.