Egg Cocoons Research Articles

Deterioration of bio-based polylactic acid plastic teabags under environmental conditions and their associated effects on earthworms

In response to the plastic waste crisis, teabag producers have substituted the petrochemical-plastic content of their products with bio-based, biodegradable polymers such as polylactic acid (PLA). Despite widespread use, the degradation rate of PLA/PLA-blended materials in natural soil and their effects on soil biota are poorly understood. This study examined the percentage mass deterioration of teabags with differing cellulose:PLA compositions following burial (−10 cm depth) in an arable field margin for 7-months, using a suite of analytical techniques, such as size exclusion chromatography, 1H nuclear magnetic resonance, dynamic scanning calorimetry, and scanning electron microscopy. The effect of 28-d exposure to teabag discs at environmentally relevant concentrations (0.02 %, 0.04 % and 0.07 % w/w) on the survival, growth and reproduction (OECD TG 222 protocol) of the key soil detritivore Eisenia fetida was assessed in laboratory trials. After 7-month burial, Tbag-A (2.4:1 blend) and Tbag-B (3.5:1 cellulose:PLA blend) lost 66 ± 5 % and 78 ± 4 % of their total mass, primarily attributed to degradation of cellulose as identified by FTIR spectroscopy and a reduction in the cellulose:PLA mass ratio, while Tbag-C (PLA) remained unchanged. There were clear treatment and dose-specific effects on the growth and reproductive output of E. fetida. At 0.07 % w/w of Tbag-A adult mortality marginally increased (15 %) and both the quantity of egg cocoons and the average mass of juveniles also increased, while at concentrations ≥0.04 % w/w of Tbag-C, the quantity of cocoons was suppressed. Adverse effects are comparable to those reported for non-biodegradable petrochemical-based plastic, demonstrating that bio-based PLA does not offer a more ‘environmentally friendly’ alternative. Our study emphasises the necessity to better understand the environmental fate and ecotoxicity of PLA/PLA-blends to ensure interventions developed through the UN Plastic Pollution Treaty to use alternatives and substitutes to conventional plastics do not result in unintended negative consequences.

Eggs in faeces: defensive mechanisms and effects of faecal coating by a water scavenger beetle, Coelostoma stultum (Coleopterea: Hydrophilidae).

The egg stage in insect development is vulnerable to fluctuations in environmental conditions and attacks by natural enemies. Protective devices are effective means of avoiding both abiotic and biotic damage to eggs. Although some insects use their faeces as a protective device, few studies have focused on using faeces for egg protection, and studies that examined the mechanism are lacking. Females of a water scavenger beetle, Coelostoma stultum, typically lay eggs and coat them with cocoons and their faeces. The efficacy of a double defensive device, however, remains uncertain. Here, we conducted field observations and laboratory experiments to assess the protective effects of cocoons with faecal coating on eggs against predation and determine the duration and mechanisms of this defence. Our findings reveal that the faeces on the egg cocoon protected eggs from predation by the pill bugs, Armadillidium vulgare, and marsh slugs, Deroceras laeve. Laboratory experiments showed that the defensive effect of faecal coating was maintained for three days and decreased daily. The double protective traits with faecal coating on the egg cocoons protected the eggs from instense predation pressure in C. stultum. The behavioural patterns of the pill bugs and egg predation rates indicate that the faecal coating behaviour in C. stultum protects eggs with chemical compounds and textural camouflage in mud when the antennae of the pill bugs touch faeces. It is important to note that for this defence to be effective, the chemistry and texture of the faeces should be similar to that of the oviposition sites.

Long-term dynamics of the abundance of earthworms and enchytraeids (Annelida, Clitellata: Lumbricidae, Enchytraeidae) in forests of the Central Urals, Russia.

BackgroundSince the late 1980s, long-term monitoring of terrestrial ecosystems in metal-contaminated areas has been carried out in the Central Urals. As a part of these monitoring programmes, the data on soil macroinvertebrates in undisturbed areas as reference sites continues to be gathered. These data help study the local biodiversity and long-term dynamics of soil macroinvertebrate abundance in non-polluted areas.New informationThe dataset (available from the GBIF network at https://www.gbif.org/dataset/bf5bc7f6-71a3-4abd-8abc-861ee3cbf84a) includes information from a long-term monitoring programme for two taxa of Annelids, Lumbricidae and Enchytraeidae, which dwell in the topsoil of spruce-fir, birch, pine and floodplain forests in the Central Urals. The dataset includes information on the earthworm community structure (list of species, species abundance, number of egg cocoons, cocoon exuvia, juveniles and adults) and enchytraeid abundance. The dataset consists of 553 sampling events (= samples, corresponding to upper and lower layers of the soil monoliths) and 12739 occurrences (earthworms, mainly identified to species and earthworm cocoons and enchytraeids, identified to family) collected during 1990–1991, 2004, 2014–2016 and 2018–2020. In total, 3305 individuals of earthworms were collected, representing ten (out of twelve) species and all eight genera recorded for the fauna of the Central Urals. In addition, 7292 earthworm egg cocoons and cocoon exuvia and 6926 individuals of enchytraeids were accumulated. The presence-absence data on each of the ten earthworm species, egg cocoons, cocoon exuvia and enchytraeids are provided for each sampling event. All data were collected in undisturbed non-polluted areas and are used as a local reference for ecotoxicological monitoring. The dataset provides valuable information for estimating the composition and abundance of earthworm communities in different habitats over a long time and contributes to the study of soil fauna biodiversity in the Urals.

Predation on the egg of Coelostoma stultum (Coleoptera: Hydrophilidae) by the alien species Deroceras laeve (Mollusca: Gastropoda: Agriolimacidae)

ABSTRACT Slugs are polyphagous herbivores that damage various crops. The genus Deroceras is primarily herbivorous; however, certain species are known to feed on various types of organic matter. In this study, we documented field observations of predation by Deroceras on eggs of the water scavenger beetle Coelostoma stultum at the waterside of paddy fields in central Japan and identified the predator species by DNA barcoding. Molecular phylogenetic analyses revealed that the slugs found sympatrically with C. stultum are Deroceras laeve, whose two haplotypes are widely distributed throughout the Palearctic and eastern margin of Asia. In two of three observed predation events, D. laeve thrust its head into the egg cocoon and preyed on eggs while C. stultum females were spinning. In the other event, no females spinning egg cocoons were observed. Due to the relatively large body size of the slug, it may push the female beetle away and prey on eggs. Considering the native distribution range of these two species, invasion of D. laeve has resulted in a new combination of predator–prey relationships in Japan between D. laeve and native C. stultum. It is a matter of concern that slugs may establish predatory pressures that threaten C. stultum.

Pinna nobilis in the south Marmara Islands (Sea of Marmara); it still remains uninfected by the epidemic and acts as egg laying substratum for an alien invader

A total of 12 Pinna nobilis beds were found and studied at depths varying between 2 and 6 m in the south Marmara Islands (Sea of Marmara). Fan mussel individuals in the beds were healthy with a few old dead specimens, indicating that the epidemic, which has devastated P. nobilis populations in the Mediterranean Sea, has not reached the Sea of Marmara, making the region a refuge area for the species. The average density of P. nobilis in the area varied between 0.6 ind.10 m-2 and 24 ind.10 m-2. The P. nobilis shells overall provided substrata or refuge for 14 species (10 sessile and 4 motile organisms), from macroalgae to fish. Shells of juvenile and adult specimens had different species assemblages. Four distinct assemblages were detected on shells, primarily formed by the red alga Gracilaria bursa-postaris, egg cocoons of the invasive alien Rapana venosa, the gastropod Bittium reticulatum and the serpulid polychaete Spirobranchus polytrema.

Redescription of enigmatic spider genus Stoliczka O. Pickard-Cambridge, 1885 (Araneae: Lycosoidea) based on the type species.

The type species of Stoliczka O. Pickard-Cambridge, 1885-S. insignis O. Pickard-Cambridge, 1885-is redescribed for the first time, based on a lectotype here designated. The genus has an uncertain taxonomic position. Originally, it was placed in Lycosidae, while it is currently considered a Pisauridae (Pisaurinae). It includes only two species known from the Western Himalayas, of which the type species remains known only from the females and S. affinis Caporiacco, 1935, which is known from a juvenile only. An uncommon behavioral feature of these spiders is the attachment of egg cocoons to the spinnerets like in the Lycosidae. The absence of the male does not allow us to clarify the taxonomic assignment of this enigmatic genus.

Harnessing the potential of the multi‐indicator palaeoecological approach: an assessment of the nature and causes of ecological change in a eutrophic shallow lake

Summary Multi‐indicator palaeoecological studies have become increasingly popular over the last decade as the need for a more complete understanding of lake ecological histories has increased. However, the true potential of the full biological record for assessing the potential drivers of observed ecological shifts in lake sediment records has rarely been demonstrated. Here, we examine the remains of a range of food‐web components including algae (diatoms), macrophytes (plant macrofossils), zooplankton (chitinous and ephippial Cladocera remains), invertebrates (including chironomids, bryozoans, Mollusca) and fish (fish scales and fish leech egg cocoons) in multiple sediment cores from Groby Pool, an enriched English shallow lake, to assess whole‐ecosystem response to eutrophication over the last two centuries. We focus on three striking changes in the palaeorecord, namely the post‐1900 increase in Daphnia spp., the post‐1840 decline in Cristatella mucedo and the post‐1940 increase in Cocconeis placentula, and utilise the multi‐indicator palaeoecological data to evaluate possible explanations for these patterns. Principal curves analysis revealed marked and broadly simultaneous changes in the plant macrofossils, cladocerans, diatoms and chironomids (as well as in other animal remains such as bryozoans and Mollusca), indicating an early period of enrichment most likely associated with land‐use change in the late 18th century, followed by a more recent eutrophication phase coincident with the discharge of sewage effluent to the lake from 1935. Ecological change, resulting from eutrophication, was shown to have progressed slowly and steadily and to have occurred at all trophic levels with a shift from a relatively diverse ‘mesotrophic’ macrophyte assemblage, dominance by benthic diatoms and plant‐associated Chydoridae and chironomids towards a relatively species‐poor, ‘eutrophic’ macrophyte community with dominance by planktonic algae (e.g. Cyclostephanoid diatom taxa), planktonic Cladocera (Bosmina, Daphnia) and a chironomid fauna dominated by mud‐associated taxa. The inferred shift in the macrophyte community from charophyte to fine‐leaved pondweed and Callitriche truncata suggests a reduction in the seasonal duration of plant dominance. The multi‐indicator analysis indicates that a combination of increased phytoplankton biomass and low zooplanktivorous fish predation is likely to explain the recent increases in Daphnia spp., while loss of plant habitat and increased competition for food appear to be the most likely causes of the observed decline in C. mucedo, and resistance to increased grazing pressure from invertebrates is the most probable driver of the C. placentula increase. Our study illustrates the potential of using the full array of fossil groups preserved in lake sediment cores to infer ecosystem dynamics over centennial timescales and to contribute to our understanding of the mechanisms that may link biological assemblages to a range of forcing factors. Further, this paper provides methodological guidance by demonstrating the ability of amalgamated records from three cores to reveal a strong sequence of events and coherent patterns.

X-ray microtomography for imaging of developing spiders inside egg cocoons

Embryogenesis is especially sensitive to external factors. The changes in its course are often used as biomarkers of environmental impact. Since spider embryogenesis takes place inside cocoons, it is crucial to find a reliable tool to analyze this developmental phase with no intrusion into the cocoons. The aim of this study was to verify the efficacy of X-ray microtomography for non-invasive analysis of embryonic morphology and egg quantity in the cocoons of Xerolycosa nemoralis and Agelena labyrinthica from polluted and reference sites. X-ray microtomography slice images as well as 3D images and animations obtained from digital visualization of those slides were used to study the morphology of embryos and egg arrangement in the cocoons. Any disorders in embryogenesis or malformation of embryos in relation to site of origin have not been found, but inside an egg cocoon of X. nemoralis from the polluted site embryos differing form each other by one developmental stage were identified. Egg calculation revealed a K- reproductive strategy of X. nemoralis from polluted sites. Finally, future prospects and benefits, and weaknessess of this method for the study of spider cocoons have presented.

Multiple paternity and mate competition in non-selfing, monogamous, egg-trading hermaphrodites

In animals in which the two sexes invest relatively similar amounts of resources in their young, the number of mates is expected to affect male and female reproductive success similarly and gender conflicts on the number of mates may not arise. Correspondingly, in non-selfing, simultaneous hermaphrodites with long-term monogamy, the two partners are expected to alternate repeatedly their sexual roles and invest similarly in their offspring. Therefore, the gender conflict on the number of mating partners should not arise. However, when >2 conspecifics are present, hermaphrodites are known to plastically adjust their behavior and sex allocation and compete for mating repeatedly in the male role. We tested whether this leads to multiple paternities of single egg clutches in experimental replicates of small and large groups of non-selfing, egg-trading, behaviorally monogamous polychaete worms (Ophryotrocha diadema) by using neutral genetic markers to estimate paternity. Multiply fertilized egg cocoons were common in these worms; two or more individuals succeeded in fertilizing the same egg cocoon and mate competition increased with group size. Multiply fertilized egg cocoons had a higher proportion of eggs developing into mature worms than singly fertilized egg cocoons. Possibly singly fertilized cocoons had a lower fertilization rate owing to low sperm counts and aflagellate sperm.

The role of ecological divergence in speciation between intertidal and subtidal Scoloplos armiger (Polychaeta, Orbiniidae)

The concept of ecological speciation implies that habitat differences may split a species by strong selection and rapid adaptation even under sympatric conditions. Studies on the polychaete Scoloplos armiger in the Wadden Sea (North Sea) indicate sibling species existing in sympatry: the intertidal ‘Type I’ with holobenthic development out of egg cocoons and the subtidal ‘Type S’ producing pelagic larvae. In the current study, Types I and S are compared in habitat-related traits of reproductive timing and physiological response to hypoxia and sulphide. Spawnings of Type I and Type S recorded over six years overlap in spring and both appear to be triggered by a rise in seawater temperature above 5 °C. Type S exhibits an additional autumn spawning (at seawater temperatures around 10 °C) which was previously unknown and is absent in Type I. The overall abundance of pelagic larvae in the Wadden Sea is higher in spring than in autumn. Tolerance of both sulphide and hypoxia was lower in Type S than in Type I. This correlates with a 5 to 10-fold lower sulphide concentration in the subtidal compared to the intertidal habitat. Physiological tolerance and divergence in developmental mode appear as traits which may have led to reproductive isolation between Type I and Type S. Their role in allopatric and sympatric speciation scenarios in S. armiger is discussed. Since the pelagic dispersal mode has been neglected so far, a reassessment of population dynamics models for S. armiger is suggested.

Reproductive isolation between intertidal and subtidal Scoloplos armiger (Polychaeta, Orbiniidae) indicates sibling species in the North Sea

Two distinct modes of development in the common polychaete Scoloplos armiger (O. F. Muller, 1776) occur in the North Sea region: holobenthic development in egg cocoons and pelagic larvae hatching from suspended eggs. In the northern Wadden Sea near the island of Sylt, we observed that egg cocoons are produced intertidally while pelagic larvae originate from the adjacent subtidal zone. A previous genetic comparison between these subtidal and intertidal populations revealed distinct gene pools, suggesting that reproductive differences are not phenotypic but heritable. In this study, crossbreeding experiments show that intertidal and subtidal populations are reproductively isolated. Couples with males and females from different habitats had no offspring. Production of egg cocoons is determined by female origin from the intertidal zone. Pelagic larvae occurred only in couples with subtidal females and subtidal males. Intertidal males have spermatozoa with heads twice as long as those from subtidal males and a significantly shorter flagellum. We suspect that deviating sperm morphology may cause the reproductive breakdown at the fertilization stage. Juveniles hatching from cocoons have shorter anal cirri compared to juveniles that metamorphosed from pelagic larvae. We conclude there to be two sympatric sibling species in S. armiger: 'type I' in intertidal areas, which have egg cocoons, no pelagic larvae, elongated sperm heads, shortened sperm flagella and anal cirri; and a subtidal 'type S', lacking egg cocoons but with pelagic larvae, short sperm heads, long sperm flagella and anal cirri.

Sibling species or poecilogony in the polychaete Scoloplos armiger?

In marine invertebrates multiple modes of development, or poecilogony, may occur in a single species. However, after close examination, many of such putative cases turned out to be sibling species. A case in point may be the cosmopolitan orbiniid polychaete Scoloplos armiger, which inhabits marine shallow sediments. In addition to the well-known direct, holobenthic development from egg cocoons, pelagic larvae have also been described. Our culture experiments revealed a spatially segregated source of the two developmental modes. All females of an intertidal population produced egg cocoons and no pelagic larvae. All but 2 out of 15 females of an adjacent subtidal population produced pelagic larvae and no egg cocoons. Based on these results we performed a molecular genetic analysis (RAPD-PCR) on three intertidal and four subtidal populations in the North Sea. Selected samples from all sites were analysed also by the AFLP method. We found significantly higher genetic diversity within subtidal than within intertidal populations. This is consistent with a wider dispersal by pelagic larvae and a smaller effective population size when development is holobenthic. Total genetic divergence is not related to distance but to the intertidal/subtidal division. We suggest that S. armiger actually represents two sibling species.

Observations on the immature stages of Georissidae (Coleoptera : Hydrophiloidea), with remarks on the evolution of the hydrophiloid egg cocoon

Specimens of Georissus crenulatus have been reared in the laboratory, and aspects of the life history are described. Egg cocoons and pupa (previously unknown in Georissus) are described and compared with those of other hydrophiloids. First instar larvae of Georissus lack cephalic egg bursters and, contrary to current assumption, these seem to be generally absent in Hydrophiloidea. The variation of egg cocoons in Hydrophiloidea is outlined and the evolution of the different types discussed.

Resource quality and the colonisation and succession of coprophagous dung beetles

In order to examine the degree of resource selectivity in a north temperate dung beetle assemblage und to identify major parameters that influence such selectivity, the occurrence of adult dung beetles (Aphodius. GeotrupesandSphaeridium) in up to five different types of dung over a period of up to 25 d was examined in a series of field experiments using standardised dung pats. There were significant physical and chemical differences in dung quality between dung types and over time during succession. Dung beetle species showed distinct preferences for particular types of dung which were generally similar in data sets from both pitfall traps and dung pat samples. Species also showed distinct patterns of successional occurrence. Ordinations produced by Canonical Correspondence Analysis, based on species occurrences in dung types and over time, usually selected dung pat age as the most important environmental variable influencing dung beetle assemblages. Dung quality parameters contributed a significant element of structure to the species ordinations but ordinations using dung types or dung quality parameter values as the environmental variables were very similar in terms of sample and species placement within the ordination for each data set. Most importantly the CCA ordinations clearly grouped species according to their breeding behaviour. Early‐successional species laid eggs in the soil, or in silken egg cocoons, which allowed them to exploit wet dung. Mid and late‐successional species laid eggs in the dung pat: late‐successional species could exploit normally wetter dung types than mid‐successional species, probably due to increased crust formation and drying as the dung pat ages. Thus, species appear to be differentially adapted to exploit varying types of dung microhabitats. Therefore, where two or more species of large herbivores are present, dung quality preferences probably constitute an important niche dimension.

Spider Adaptation to Artificial Biotopes: The Fauna of Percolating Filter Beds in a Sewage Treatment Works

The spider faunas of two filter beds at the Minworth Sewage Treatment Works in Birmingham, UK, were studied from June 1980 to June 1981 inclusive, to investigate their role in this specialized community. The spider fauna was dominated by only two species, Leptorhoptrum robustum and Erigone longipalpis (Linyphiidae), although two others were able to live permanently in the stone medium, in very low numbers. The zonation of spiders throughout the 1.8 m depth was studied by using vertical shafts containing 10-12 canisters of stones which could be removed and sampled. The filter bed environment has a constant humidity, small variation in temperature, abundant food, and is relatively free from spider predators and parasites apart from entomophagous fungi. The lowest numbers of spiders were recorded in the winter and spring, and very high values were recorded in mid-summer when each individual spider had only 3.2 x 3.2 cm of stone surface and 2.5 cm 3 of air space. Immature specimens were always more numerous than adults except in winter and spring. The highest numbers of egg cocoons of both dominant species were recorded in October, but there was a long delay before the majority of the eggs hatched in May/June. The very high populations in June of over 67 000 m -3 coincided with massive aerial dispersal movements. The influence of toxic metals in the crude sewage on the spider fauna is discussed but no evidence was found that the populations were affected. An estimate is made of the potential ability of the spider fauna to control nuisance flies which breed in the filter beds. Control could be achieved by reducing the interruptions to sewage flow and confining shutdowns for maintenance work to early spring when populations are low. This would also reduce the incidence of spider bites among maintenance staff.

Hatching of Enchytraeidae (Oligochaeta) from egg cocoons in agricultural soil exposed to different drought regimes - a laboratory study

Hatching of Enchytraeidae (Oligochaeta) from egg cocoons in agricultural soil exposed to different drought regimes - a laboratory study

Complex carbohydrates in shell precursor globules of the vitellarium and at the eggshell of Hymenolepis microstoma (Cestoda).

The vitellocytes of Hymenolepis microstoma contain protein globules as building material for the shell of egg cocoons. Complex carbohydrates were detected as an additive component, dispersed in the matrix of the shell globules. Similar glycans were found at newly formed shells, suggesting that these molecules are provided by the vitellocytes. The glycans remained associated with the surface of mature eggs. Carbohydrate residues, characterized using gold-labeled lectins, were N-acetylglucosamine, galactose, or the N-acetyllactosamine sequence of these residues and N-acetylgalactosamine, whereas glucose, mannose, and fucose were not demonstrable. The glycans scarcely stained with periodic acid-Schiff and, thus, seem to have few diols, and they did not bind cationic dye, indicating that they are not glycosaminoglycans. Since they occur in significant amounts, the glycans may have fundamental, as yet undetermined function(s) in the formation of the shells and/or interactions of the cocoons with the host.

Morphology, egg cocoons, and transmission paths of the Antarctic leech Glyptonotobdella antarctica Sawyer and White, 1969 (Hirudinea: Rhynchobdelliformes: Piscicolidae)

The biology of piscicolids which move between different host species is poorly understood. Very little is known about leeches of Antarctic waters, though they are not uncommon in that region. This paper adds to the fundamental knowledge of the Antarctic piscicolid leech Glyptonotobdella antarctica Sawyer and White, 1969. According to the new findings the distribution of the species has to be extended to the geographical latitude of 76°08.1′S and to a depth of 665 m. Besides Glyptonotus antarcticus Eights 1853, sea urchins of the genus Sterechinus (Meissner 1900), and the benthic octopus Pareledone (charcoti?) (Joubin 1905) serve as hosts. Hitherto there were only two records on piscicolids from Octopus dofleini and none from sea urchins. Egg cocoons on the ventral side of the isopod Glyptonotus antarcticus were attributed to the leech. Most likely Glyptonotobdella antarctica moves between different hosts, i.e. Antarctic octopuses and their potential prey. Surface structures of the leech are studied by light and scanning electron microscope. The observations complement the basic knowledge on Antarctic leeches and provide arguments for phylogenetic discussions.

The biology and conservation of the giant gippsland earthworm MEGASCOLIDES AUSTRALIS mccoy, 1878

Megascolides australis McCoy, 1878 is one of the world's largest earthworms and is restricted to a small area in South Gippsland, Victoria, Australia. It is listed by the IUCN as “vulnerable”. Adult worms average ca 750 x 20 mm and weigh upto 381 g. Three developmental (presumably age) classes have been found in the field based on the structure of the clitellum; young worms (mean 33 g), subadults (mean 69 g) and adults (mean 210 g). Adults form the dominant age class of the population at all times of the year, having densities up to four times those of immatures. Reproductively active adults were recorded mainly from September to December. Egg cocoons occur singly at an average depth of 220 mm and a density of 1.6 m -3. Incubation period is at least 12 months. Egg cocoons are 40–70 mm x 10–15 mm in size with an average weight of 9g. Worm distribution is patchy. Systematic sampling in a 2 × (1 × 1) km grid revealed worms in only 6% of the quadrats sampled. Over 80% of the occupied quadrats were within 40 m of the banks of streams or among soaks on south facing slopes. Prospects for conservation of the worm are discussed within the known framework of the species biology.

An alternative mode of larval development inScoloplos armiger (O. F. Müller, 1776) (Polychaeta, Orbiniidae)

During a three-year plankton monitoring at the island of Helgoland (German Bight, North Sea), pelagic larvae ofScoloplos armiger (O. F. Muller, 1776) were observed to occur regularly from February to April. Up to the present day, only benthic development within egg cocoons has been described (Anderson, 1959). Planktonic larvae comprise early, ovoid trochophores up to advanced stages with 11 setigers. The main morphological difference between the two larval types is the more numerous differentiation of lateral cilia by the pelagic larvae. Annual alterations in appearance and abundance suggest that reproduction is correlated with water temperature.