The setae of Austropotamobius pallipes (Crustacea: Astacidae)

The author presents here the results of an introductory study into the setal armature of the British species of crayfish, Austropotamobius pallipes (Lereboullet, 1858). Using an ordinary optical microscope, it is demonstrated that a considerable variety of setae exist on the body and appendages of A. pallipes. These setae are described, and their distribution indicated. The setae fall into two main groups:
(1) Setae with relatively thick walls and inconspicuous ampulla, and having no basal septum.
(2) Those setae with relatively thin walls, a well-developed ampulla and basal septum. Further subdivisions of these two groups are made on the bases of outgrowths and outlines of the setal wall. Finally, the significance of the distribution and the variation, is discussed in relation to crayfish behaviour and function, linking the observed morphological facts with the results of some current electro-physiological experiments performed on related decapods.     

Growth in the crayfish Austropotamobius pallipes (Crustacea: Astacidae)

SUMMARY. The growth of Austropotamobius pallipes was studied in the River Ouse during 1976–78. Growth of mature crayfish (>2.5 cm carapace length) was followed by determining the relationship between the growth increment at moult and premoult carapace length, together with the frequency of moulting of different categories of crayfish. These data are supplemented by the recapture of marked individuals and the measurement of crayfish held in corves in the river. Growth was limited to the period May–October when water temperatures exceeded 10°C. Growth rates of male and female crayfish are similar until maturity is reached, thereafter males moult twice per year and the majority of females moult once. No crayfish in excess of 3.7 cm carapace length has been observed to moult more than once per year. Growth of juveniles (<2.5 cm carapace length) was estimated from size frequency distributions constructed from regularly taken samples. Growth rates of juveniles showed great variation both between and within year classes. In the hot dry summer of 1976, juveniles exhibited faster growth rates (instantaneous growth rates (G) for 0+ and 1 + crayfish were 0.029 and 0.013 mg mg⁻¹ day⁻¹. respectively) than in other years. Laboratory experiments on the effect of temperature on the growth rate of 0 + crayfish were undertaken; for crayfish at 15°C. G = 0.0138 (0–53 days) and at 10°C, G = 0.0003 (0–90 days). Crayfish held at 10°C failed to undergo a single successful moult. At 20°C crayfish exhibited exponential growth over the first 40 days, with G = 0.0189. declining thereafter to G = 0.012 (40–90 days).     

Mating and spawning of the crayfish Austropotamobius pallipes (Crustacea: Astacidae)

Mating and spawning of the crayfish Austropotamobius pallipes (Lereboullet) is described and compared with the accounts of this behaviour in Orconectes limnosus, Pacifastacus trowbridgii and Homarus amerieanus.     

Die rezente Verbreitung der Flusskrebse in Hessen (Decapoda: Astacidae)

1. This investigation demonstrates the presence of three different species in Hessen (West Germany). By means of three maps the recent distribution is demonstrated.
2. Astacus astacus is still present in Hessen in small populations.
3. Austropotamobius torrentium is the rarest species and was recorded only in the Taunus-, Spessart- und Odenwald mountains.
4. Oronectes limosus, in the rivers Rhein and Main numerous before 1950, has become scarce. In the river Fulda there have been only two recordings in 1958.

     

Studie der Astacidae (Crustacea,Decapoda) II. Teil

Ohne Zusammenfassung     

Role of the Dinaric Karst (western Balkans) in shaping the phylogeographic structure of the threatened crayfish Austropotamobius torrentium

1. This study examines phylogeography and phylogeny of the threatened stone crayfish, Austropotamobius torrentium, in order to elucidate the role of the Dinaric Karst geology in shaping the evolutionary history and genetic diversity of aquatic fauna in the western Balkans. Mitochondrial 16S rRNA and COI genes were partially sequenced from 188 and 159 crayfish, respectively, sampled from 70 localities. Phylogenetic relationships were reconstructed using four methods of phylogenetic inference. Divergence times between phylogroups were estimated in a Bayesian framework, and their demographic history was examined using neutrality tests and mismatch distribution analysis. 2. Seven geographically localised phylogroups separated by pronounced genetic gaps were found. Five of them have a distribution range within the northern‐central Dinaric (NCD) region, while the remaining two include populations from the southern Balkans (SB) and central and south‐eastern Europe (CSE). The oldest divergence event separated two NCD lineages from the rest of populations in the Late Miocene or Early Pliocene. Divergences amongst the five NCD phylogroups and SB + CSE occurred in the Pliocene. The most recent split separated SB and CSE phylogroups during the Late Pliocene. For both genes, uncorrected pairwise divergences between most of the phylogroups (4.1–8.7% for COI and 1.6–4.8% for 16S rRNA) were of the same range as, or higher than, some of the interspecific distances previously reported for the genus Austropotamobius. 3. Geographically isolated and deeply divergent cryptic monophyletic phylogroups within A. torrentium in the NCD region arose in the course of intensification of Neotectonic movements during the Pliocene and the beginning of the Pleistocene and the development of karstification that has heavily fragmented the palaeohydrography of the area. The results confirm a gradual north–south expansion of stone crayfish during the pre‐Pleistocene that preceded the rapid northward post‐glacial re/colonisation of central Europe (CSE phylogroup) through the Danube drainage. 4. Austropotamobius torrentium comprises morphologically cryptic but molecularly distinct taxa. Considering the relatively small geographical areas they inhabit, the NCD phylogroups of stone crayfish should be given the highest conservation priority.     

The role of water chemistry in the distribution of Austropotamobius pallipes (Crustacea Decapoda Astacidae) in Piedmont (Italy)

Over the last decades, the populations of Austropotamobius pallipes have decreased markedly all over Europe. If we evaluate the ecological factors that determine its presence, we will have information that could guide conservation decisions. This study aims to investigate the chemical-physical demands of A. pallipes in NW Italy. To this end, we investigated 98 sites. We performed Principal Component Analysis using chemical-physical parameters, collected in both presence and absence sites. We then used principal components with eigenvalue > 1 to run Discriminant Function Analysis and Logistic Regression. The statistics on the concentration of Ca²⁺, water hardness, pH and BOD₅ were significantly different in the presence and in the absence sites. pH and BOD₅ played the most important role in separating the presence from the absence locations. These findings are further evidence that we should reduce dissolved organic matter and fine particles in order to contribute to species management and conservation.     

Reproduction in an Irish lake population of the crayfish Austropotamobius pallipes (Lerehoullet)

SUMMARY. 1. Mature crayfish were collected in 1984 from an alkaline Irish lake before and after the mating season.
2. There was some correlation between frequency of mating and decrease in vasa deferentia weight in captive males, but in the field vasa deferentia weight losses were highly variable. The data indicate that one third of adult males may not have mated in the wild.
3. All females appear to have spawned, whether or not mated, with an average 85% reduction in ovary weights over the season.
4. Pleopodal egg counts directly after laboratory spawning were on average 81% of ovarian counts; in the field, an estimated 50 days after spawning, they were only 61% of estimated ovarian egg numbers.
5. Average ovarian egg size was positively correlated with female size. Also, larger crayfish had a wider range of egg sizes than smaller crayfish.
6. It is suggested that aggression and competition for shelter among brooding females may result in a progressive loss of eggs.     

Invasive American crayfish <Emphasis Type="Italic">Pacifastacus leniusculus</Emphasis> (Decapoda: Astacidae) in the Morava River (Slovakia)

The signal crayfish, Pacifastacus leniusculus (Dana, 1852), was recorded in the Slovak-Austrian stretch of the Morava (March) River in the Záhorie region in August 2006. This is the first confirmed record of a non-indigenous crayfish species of American origin in Slovakia. Most likely, signal crayfish were intentionally released to the river by Austrian fishermen, or invaded from adjacent water bodies in Austria. As this species has a substantial invasive capability and is a potential vector of the crayfish plague pathogen, it represents a threat to the native crayfish species and its spread should be monitored. Its invasion upstream to the territory of the Czech Republic is not unlikely in near future.     

Tertiary sex ratios in wild Galago population (Mammalia: Primates)

Previous studies have proposed that species within the genus Galago exhibit a secondary sex ratio that is strongly skewed (approximately 70%) in favour of males. It has further been suggested that this sex ratio is maintained into adulthood. We present data obtained from 669 adult galagos, representing eight wild populations and five species, to indicate that the sex ratio among sexually mature individuals is close to parity. If the observations regarding sex ratios at birth are correct, this implies that juvenile/sub-adult males suffer significantly higher mortalities than do their female counterparts.     

Genetic population structure of the swimming crab Callinectes danae (Crustacea: Decapoda) in southern Brazil

The population genetic structure of the swimming crab Callinectes danae (Crustacea, Portunidae) was studied by allozyme electrophoresis along the southern coast of Brazil (Santa Catarina and Rio Grande do Sul States). The biology of C. danae is poorly known, but some studies suggest that this species depends on estuaries for reproduction and for completing its life cycle, using them as recruitment sites and nursery grounds. If estuarine retention is an important process acting in favour of the recruitment of local populations, we should expect restriction of gene flow among populations inhabiting different estuaries. Therefore, our aim was to establish whether gene flow between populations of C. danaefrom different estuaries was restricted. Samples were collected in four estuaries: São Francisco do Sul, Laguna (Santa Catarina), Patos Lagoon and Chuí Stream (Rio Grande do Sul). Eleven loci were resolved. Contingency table tests (² and G) showed significant differences (P0.05) between pair-wise subpopulation comparisons. The estimated F _ST was =0.065±0.019, suggesting a moderate structuring of C. danae populations. No relationship was found for the number of migrants between pairs of subpopulations and the geographic distance separating them (P= 0.292; r ²= 0.269). Nevertheless, UPGMA analysis clustered together those estuaries separated by less than 250 km. Low adult migration, the requirement of estuaries as reproductive areas, recruitment sites and nursery grounds for juveniles, together with larval and post-larval retention processes, are discussed in the context of their importance in preventing panmixia among subpopulations inhabiting different estuaries.     

A new morph of Telmatochromis temporalis (Cichlidae; Cichliformes) from Lake Tanganyika

Telmatochromis temporalis is a cichlid fish endemic to Lake Tanganyika. Two morphs of this species, normal and dwarf, form a good model for the study of ecological speciation through divergent natural selection on body size. This study reports a third morph of this species, slender morph, which was collected from deep waters off Kasenga, Zambia, whereas the normal morph inhabits shallow waters of the same locality. This study examined morphological characters and mitochondrial DNA sequences in 18 populations of the three T. temporalis morphs and two closely related species. The slender morph was morphologically similar to the normal and dwarf morphs of the same species, but clearly differed from closely related species. Genetic analyses showed that the slender morph was closest to but significantly different from the parapatric normal morph, suggesting reproductive isolation between them. Due to the lack of colour differences between morphs and of obvious geographical barriers between habitats, reproductive isolation between these morphs may be attributed to ecological factors, rather than sexual or geographical segregation. Further studies examining the evolution of the slender morph may deepen our knowledge of initial stages of speciation, like in the dwarf morph.

     

Male morph determination in Rhizoglyphus echinopus (Acaridae)

In Rhizoglyphus echinopus (Fumouze and Robin) two male morphs occur: heteromorphs, with a thickened and sharply terminated third pair of legs that serve as a weapon in intrasexual conflicts, and homeomorphs, with unmodified legs. This study investigated the system of male morph determination. No significant heritability of male morph was found, but cues emanating from a dense colony were found to suppress the production of heteromorphs. Developmental plasticity was retained throughout the protonymphal stage. Diet did not influence morph expression, but lowered temperature decreased the proportion of heteromorphs emerging.     

Reproduction in Nephrops norvegicus (Decapoda: Nephropidae)

During the period October 1969 to April 1972 a comprehensive study of the reproductive biology of the Norway lobster, Nephrops norvegicus (L. 1758), was made in the Irish Sea. Where possible comparison has been made with data from other areas. The results of the present investigation show that most females are berried annually, egg-laying taking place in August and September, and hatching in April to June of the following year. Moulting and copulation occur in mature females during May to August. In contrast males do not show a marked reproductive cycle, spermatogenesis occurring throughout the year. The method of fertilization is discussed, and it is suggested that this may be internal. Copulatory and egg-hatching behaviour is described, together with details of egg-laying and incubation in the laboratory. A pre-zoeal larval stage is described for the first time, bringing the total number of larval instars to four. The terminology of the larval stages is revised.     

Severe inbreeding depression in a wild wolf (Canis lupus) population

The difficulty of obtaining pedigrees for wild populations has hampered the possibility of demonstrating inbreeding depression in nature. In a small, naturally restored, wild population of grey wolves in Scandinavia, founded in 1983, we constructed a pedigree for 24 of the 28 breeding pairs established in the period 1983-2002. Ancestry for the breeding animals was determined through a combination of field data (snow tracking and radio telemetry) and DNA microsatellite analysis. The population was founded by only three individuals. The inbreeding coefficient F varied between 0.00 and 0.41 for wolves born during the study period. The number of surviving pups per litter during their first winter after birth was strongly correlated with inbreeding coefficients of pups (R2=0.39, p<0.001). This inbreeding depression was recalculated to match standard estimates of lethal equivalents (2B), corresponding to 6.04 (2.58-9.48, 95% CI) litter-size-reducing equivalents in this wolf population.