External Fertilization

For species with external fertilization (many fishes and amphibians) a simple answer is that when spermatozoa are delivered into the watery environs near to the egg most will be lost and only a minority will notice their fashion towards the egg.

From: Encyclopedia of Reproduction (Second Edition) , 2018

Sperm Limitation, Gamete Competition, and Sexual Selection in External Fertilizers

D.R. Levitan , in Sperm Competition and Sexual Selection, 1998

I INTRODUCTION

External fertilization is a common and widespread reproductive strategy in aquatic environments ( Giese and Kanatani 1987) and is generally thought to be ancestral to internal modes of reproduction (Jägersten 1972; Parker 1984; Wray 1995; but see Rouse and Fitzhugh 1994). Therefore, estimates of male person and female fertilization success in external fertilizers may provide non but information on sperm competition for the majority of beast phyla but also insight into the evolution of sexual dimorphism and internal fertilization.

Despite the demand to understand the patterns and consequences of variation in both male and female fertilization success, petty is known well-nigh the fate of gametes released in aquatic environments. Historically, discussions near reproductive success in external fertilizers were based on speculation or laboratory studies (reviewed by Levitan 1995a). It has only been in the terminal decade that some of the practical obstacles associated with 'chasing' gametes in an aquatic medium have been overcome. Estimates of gamete concentration and fertilization take been made, but there is still no direct data on sperm competition and multiple paternity.

In dissimilarity to well-nigh other organisms, the available prove on external fertilizers suggests that sperm is limiting. Bear witness from field experiments (Table 6.1) and natural observations of spawning (Table 6.two) demonstrate that the proportion of a female'south eggs that are fertilized is often much less than 100%, and a majority of the variation in female fertilization success can exist explained past male abundance, proximity, or synchrony. This somewhat unlike view of sexual pick has implications for the generality of Bateman's principle (Bateman 1948) and the evolution of sexual dimorphism in this presumptive bequeathed reproductive strategy.

Table six.1. Experimental evidence of variation in female person fertilization success in complimentary- spawning invertebrates. Hateful and range of the pct of eggs fertilized and a summary of the major factors influencing variation in fertilization.

% Fertilization
Taxa Hateful Range Effect Reference
Cnidarians Hydrozoans
Hydractinia echinata 41 0–91 Female fertilization decreased with male distance Yund (1990)
Bryozoans
Celloporella hyalina 100 100 a Selfing inversely related to number of conspecific male zooids Yund and McCartney (1994)
Echinoderms Asteroids
Acanthaster planci 32 0–90 Female person fertilization decreased with male person distance Babcock et al. (1992)
Asterias forbesi 52 ii–99 Female fertilization decreased with depth Present study
Echinoids
Clypeaster rosaceus xxx 2–72 Female fertilization decreased with male person distance Levitan and Young (1995)
Diadema antillarum 23 0–99 Female person fertilization increased with male density and decreased with male person distance, male size not meaning Levitan (1991)
Strongylocentrotus droebachiensis thirty ane–95 Female fertilization increased with male abundance, decreased with male distance and flow Pennington (1985)
Strongylocentrotus franciscanus xviii 0–82 Female fertilization increased with abundance and aggregation, decreased with flow Levitan et al. (1992)
Chordates Ascidians
Botrylius schiosseri 41 25–lx b Female fertilization increased with male person density, male success decreased with male competition Yund and McCartney (1994)
a
Selfing hermaphrodite.
b
Range of ways across treatments.

Table 6.2. Natural observations of variation in female fertilization success in free-spawning invertebrates.

% Fertilization
Taxa Hateful Range Comments Reference
Cnidaria Gorgonians
Briareum asbestinum 4 <0.01–6.5 Variation related to density Brazeau and Lasker (1992)
Plexaura kuna c. twenty 0–100 Few male clones Lasker et al. (1996)
Pseudoplexaura porosa 51 0–80 a Common Lasker et al. (1996)
Scleractinians
Montipora digitata c. 30 0–75 Variation related to spawning synchrony Oliver and Babcock (1992)
Arthropoda Merostomata
Limulus polyphemus 74 0.6–100 No effect of satellite males Loveland and Botton, in review
Echinodermata Asteroids
Acanthaster planci 44 23–83 Variation related to spawning synchrony Babcock and Mundy (1992)
Holothuroids
Cucumaria frondosa c. 70 45–82 b High density and synchrony Hamel and Mercier (1966)
Cucumaria miniata 92 1–100 High density and synchrony Sewell and Levitan (1992)
Actinopyga lecanora 73 67–78 Several individuals spawning Babcock et al. (1992)
Bohadshia argus 57 0–96 Variation related to altitude from males Babcock et al. (1992)
Holothuria coluber 33 9–83 Variation related to synchrony Babcock et al. (1992)
a
Range of means across days.
b
Range of ways across multiple samples

In this chapter, I offer the possibility that in externally fertilizing organisms sexual choice is intense but approximately symmetrical across sexes. This is a result of (1) sperm limitation, which results in (2), increased variation in the proportion of a female person's eggs that are fertilized, and hence increased variation in female person reproductive success relative to taxa with internal fertilization, and in plow results in (3), choice for enhanced fertilization success not just for males but also for females. As a consequence, sexual dimorphism in both primary and secondary sexual characteristics is reduced or absent-minded. This hypothesis leads to the notion that anisogamy and copulation evolved because of sperm limitation rather than sperm contest, an adaptation that in this scenario benefits both males and females. In lodge to build these arguments, I must kickoff define the relevant terms, review what is known virtually fertilization in externally fertilizing organisms and patterns of sexual dimorphism, and then endeavour to identify this evidence in a theoretical framework. This is not a completed project, and my goal is to stimulate interest in sexual option on external fertilizers.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780121005436500313

Patterns and Drivers of Egg Pigment Intensity and Colour Diversity in the Bounding main

E.M. Montgomery , ... A. Mercier , in Advances in Marine Biology, 2017

iv.one Evolution Site Explains Pigment Intensity But Not Colour Multifariousness

Species with external fertilization and pelagic development take to overcome different challenges than those faced by incubating species, including exposure of eggs to sunlight and other ecology pressures ( Burgess et al., 2013; Gillespie and McClintock, 2007). Whether free-spawned or brooded, lecithotrophic eggs/embryos obtain lipid reserves from maternal sources and thus do not require external nutrition during development (Falkner et al., 2013; Prowse et al., 2008). These storage lipids (i.e. wax esters in echinoderm larvae) are susceptible to oxidative stress from oxygen free radicals, metabolites, and UV radiation (Blount, 2004; Falkner et al., 2006; Villinski et al., 2002). Pelagic lecithotrophic embryos and larvae are commonly buoyant (in ~   75% of species analysed hither) and spend a portion of their development at or close to the sea surface. Hence, floating propagules near the body of water surface presumably require more antioxidants, which could explain why near all pelagic, nonfeeding propagules in the dataset possess intense pigments, potentially a class of carotenoid, a pigment form found to have antioxidant function in other animals (Blount, 2004; Vershinin, 1999). Externally brooded propagules as well possessed intense pigmentation (~   65% of species), probably because they are still exposed to some level of UV radiation and environmental fluctuation in shallow benthic environments. Apart from antioxidant activity, the brighter pigmentation of externally brooded propagules may also afford cryptic colouration (matching the adult body colour) to minimize predation during their development. This pattern is well illustrated in the sea star Trophodiscus sp. and among brooding cidaroid urchins (Mah, 2009). In contrast, internally brooded propagules had stake chocolate-brown or cream egg colours (~   90% of species in dataset). This is non surprising given that internally brooded propagules are commonly non released until the feeding juvenile stage is reached, then their exposure to UV rays and free radicals is minimal during early development. Taken together, the lack of intense egg pigments among internal brooders strongly suggests that bright pigments provide an adaptive value for pelagic or external development.

This dichotomy between benthic/brooded and pelagic evolution can exist exemplified within echinoderm species that possess multiple types of eggs and larvae. The deep-bounding main asteroid H. lisa broods a few eggs under its body and complimentary-spawns the remainder. The eggs and larvae produced for brooding are pale in colour relative to the propagules produced for pelagic development in H. lisa (Mercier and Hamel, 2008a; see inset in Table 2). This colour difference suggests that maternal provisioning of pigments tin can vary across propagules of the same clutch. Bear witness of deliberate alteration of larval energy reserves depending on reproductive strategy is relatively rare in echinoderms, but is common among annelids (Knott and McHugh, 2012) and opisthobranchs (Krug, 2009) with mixed modes of evolution (poecilogony). By increasing the concentration or type of pigments present in their gratuitous-spawned progeny, Henricia females may be enhancing offspring survival if such pigments are critical for lipid protection in the pelagic environment. The power to deposit certain pigments may also exist genetically controlled equally seen in polychaete worms, where colour intensity variation is the consequence of selective pigment uptake from food (Sella and Marzoná, 1983).

Tabular array 2. Within-Species Colour Variation Is a Part of Life History and Buoyancy in Ii Species of Body of water Star (Henricia lisa, Echinaster echinophorus)

Species Development Site Egg Color
Henricia lisa; (Mercier and Hamel, 2008a) Brooded (−) Stake grey (a)
Pelagic Brilliant xanthous (b)
Echinaster echinophorus; (Atwood, 1973) Pelagic (−) Orange
Pelagic (+) Black

The inset photo illustrates the brachiolaria larvae of the sea star H. lisa. These larvae were spawned during the aforementioned event; the pale grey one (a) was brooded and the bright yellow one (b) broadcasted in the h2o column. Scale bar represents 1   mm. +, positive, −, negative.

In addition to pigment intensity differences, pelagic and brooded/benthic propagules also varied in buoyancy in the nowadays study. Eggs that developed pelagically could exist positively, neutrally, or negatively buoyant, whereas brooded eggs were ever negatively buoyant. This is not surprising, every bit information technology would be difficult, especially for the external brooders, to proceed floating eggs on or under the parent's body. In species with mixed types of development (similar Henricia spp.), differing egg buoyancies could allow females to sort propagules at spawning. Positive egg buoyancy in echinoderms has historically been associated with lipid deposition past the female person (Emlet, 1994). Simply the very large eggs seen in external brooders are not positively buoyant, despite major maternal yolk deposition (Emlet, 1994). Such variation in buoyancy may be facilitated though manipulation of lipid to protein ratios. Some bounding main stars (e.g. Meridiastra spp.) with similar egg volumes produce eggs with different buoyancies by altering the total corporeality of lipid present while leaving the protein levels unchanged (Prowse et al., 2008). Thus at that place may exist an increased cost associated with production of positively buoyant eggs that explains egg size differences in species with pelagic vs brooded eggs. Overall, inter- and intraspecific variation in the intensity of egg pigmentation and egg buoyancy is clearly linked to development site in lecithotrophic echinoderms. Nonetheless, these factors do non explain the wide variation in colouration seen among echinoderm eggs, suggesting that additional variables drove the evolution of egg pigment diverseness in the ocean.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/S0065288116300347

Hormones and Sexual Behavior of Teleost Fishes

David 1000. Gonçalves , Rui F. Oliveira , in Hormones and Reproduction of Vertebrates: Fishes, 2011

2.3 Internal and External Fertilization

In teleost fishes, external fertilization is predominant over internal fertilization and is considered to be the bequeathed condition. In species with external fertilization, sperm and egg release may exist synchronous or asynchronous. Synchronous spawning seems to be predominant in pelagic spawners. When external fertilization takes place in the water-column betwixt paired fish, the male and the female may assume positions that bring their genital pores shut and synchronize the release of eggs and sperm ( Breder & Rosen, 1966). A common strategy in group spawning species is for several males to follow a gravid female and compete for a privileged position shut to her. When the female assumes a spawning posture, males closer to the female person try to release sperm synchronously with egg release (Domeier & Colin, 1997; Kiflawi, Mazeroll, & Goulet, 1998). In asynchronous spawning species, males may release sperm prior to or after egg laying. For instance, males of some gobies perform upside-down movements inside the nest, during which they attach sperm trails to the nest walls prior to oviposition by the female (e.1000., Marconato, Rasotto, & Mazzoldi, 1996; Ota, Marchesan, & Ferrero, 1996). Sperm release afterward oviposition occurs, for instance, in haplochromine cichlids. Females deposit the eggs in the male's nesting pit and immediately subsequently collect them with the mouth. Attracted by the anal fin egg-spots characteristic of haplochromine male cichlids, females arroyo the male's genital region and try to pick up these egg mimics. Males and then release sperm and fertilization takes place within the female's mouth (Fryer & Iles, 1972; run into also Salzburger, Braasch, & Meyer, 2007).

In species with internal fertilization, females may cooperate with males or not. In the offset case, females betrayal the genital pore to males and facilitate intromission of the male person's copulatory organ. In the second example, a male chases a female person while trying to insert the copulatory organ into the female's genital pore. Detailed descriptions of these behaviors for the guppy Poecilia reticulata tin can exist found in Liley (1966) and Houde (1997).

Boggling exceptions to the general pattern of egg fertilization in animals are seahorses and pipefishes (Syngnathidae). In some genera, males take breed pouches and females transfer the eggs past inserting their ovipositor into the male's breed pouch. Egg fertilization takes place inside the male's pouch, and the male incubates the eggs until hatching (Fiedler, 1954).

Motor patterns associated with gamete release are less variable than behaviors preceding this step. Sperm ejaculation is ordinarily accompanied by stereotyped motor patterns consisting of high-frequency body quivering and are often similar between species with internal and external fertilization (Breder & Rosen, 1966). Egg laying may also be accompanied by quivering, whereas in live bearers parturition consists of lower-frequency contractions of the intestinal cavity, or of the pouch walls in the case of male syngnathids (Breder & Rosen, 1966).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780123750099100074

Mating Systems

Michael D. Breed , Janice Moore , in Animal Behavior (Second Edition), 2016

11.ix Sperm Competition

Sperm competition is a form of male–male competition that warrants its ain section in a textbook because information technology is indeed so basic and of import. 78 Many 79 marine animals release their gametes into the ocean (this is called spawning), but this does non mean in that location is an absence of competition in mating, nor does information technology mean that the resulting zygotes are the results of random meetings of eggs and sperm. Every bit with many topics in science, the absenteeism of much evidence for a miracle–in this case, for competition among small objects in the vast sea–does non mean contest does not occur. Spawning is most common in aquatic or semiaquatic environments, where sperm tin easily swim to eggs. In this organisation, animals that release the largest amounts of sperm with strong swimming abilities are most likely to sire young. Sperm competition was probably the first type of sexual contest to evolve, and as anisogamy evolved, sperm contest was central to the evolution of mating systems.

Sperm competition, coupled with external fertilization, is the simplest and, past far, the most common blazon of fertilization across the broad spectrum of the animate being world. In many species, male and female never demand meet; the female deposits her eggs, and later a male finds and fertilizes them. Even under these unproblematic conditions, ii processes brand mating nonrandom. Starting time, there is variation in the ability of males and females to find appropriate locations to deposit their gametes. 2d, variations in sperm pond speed and energy resource affect which sperm reaches the egg beginning.

Key Term

Sperm competition occurs amongst sperm later they are released from the male. The sperm from a single male may compete to attain an egg get-go; if the female has mated with more than than i male, then sperm competition occurs among the males.

Sperm competition has been studied in many species of fish with external fertilization. Selection strongly favors all males that produce sperm with maximum speed and energy resources (ATP), but in many species at that place are still large enough differences among sperm from different males to affect fertilization probabilities. The corporeality of sperm, or sperm volume; the distance of sperm release from the eggs; and the timing of sperm release are as well critical factors in sperm contest. The more sperm a male is able to produce, the higher the probability that i of his sperm will win the competition. Males that are able to get closer to eggs are by and large more probable to be successful, and a few seconds' deviation in sperm release can make all the departure in whether a male'due south sperm reaches the eggs kickoff.

Mostly, sperm book is correlated with testicular size (Figure 11.30); larger testicles are necessary for production of larger amounts of sperm. A basic prediction in the biology of mating systems is that males of species with more intense sperm competition volition have larger testes. The evolutionary responsiveness of testicular size to sperm competition is an important example of the effects of sexual selection on morphology and anatomy. Sometimes sperm limitation, which occurs when one male's ejaculate doesn't contain enough sperm to fertilize all a female'southward eggs, results in selection for polyandry, in which the female mates with more than than one male.

Figure eleven.30. Big testicular size relative to body size may be an indication of an evolutionary history that includes sperm competition. Why might this male exist displaying/exposing his scrotum?

 Photograph: Michael Breed.

Sperm may also cooperate. This seems odd in a situation that allows merely i sperm to fertilize an egg, just isolated sperm are not efficient swimmers. An aggregate of a few sperm (5–10) swims together—working cooperatively, the sperm swim faster and more directly to the egg. When the egg is reached, contest takes over. fourscore

In many cases external fertilization is combined with courtship; even though the eggs and sperm are released into the surround, the male and female outset have the opportunity to appraise the quality of their potential mate before committing their gametes. Bluegill sunfish (Lepomis macrochirus), a common fish of lakes in North America, exemplify how sperm competition can play a function in a more circuitous mating arrangement that involves sophisticated behavioral interactions. Bluegill males can prefer a diverseness of mating strategies (Figure 11.31). Some, termed "parental" males, build nests in the bottom of the lake and court females, who spawn in the nest. Parental males then guard the eggs. "Sneakers" dash in and release sperm near the nests of parental males. And male person "satellites" are able to come close to eggs considering they mimic females. Sperm of all three types of males accept like speed and swimming ability, but even though sneaker males release their sperm farther from the eggs and later than parental males, they take an reward over parental males. 81 This suggests that sneaker males produce higher-quality sperm. Satellites also have an advantage over parentals, simply this could be explained by the fact that they tin go closer to the eggs when they release their sperm.

Figure 11.31. A male bluegill sunfish and nest. This parental male person is advertising the resource it has to support eggs. Sneaker males effort to spawn with females that are budgeted parental males.

 Photo: Eric Engbretson, US Fish and Wildlife Service.

Internal fertilization facilitates mating in terrestrial environments and, compared to external fertilization, allows for more than control over gametes past both males and females; most terrestrial animals accept evolved some class of internal fertilization. With internal fertilization, males practice not need to respond then much to the furnishings of dilution and distance from the eggs on their gametes, and both sexes can exert a greater degree of choosiness over their mates. Withal, sperm contest remains an important mechanism in animals with internal fertilization. Sperm from a male will compete amongst themselves for fertilization opportunities, merely any time a female mates more than once inside a short time period, sperm contest amidst the sperm from the different males is likely. 82 In some cases, males fifty-fifty remove the sperm deposited by previous males. 83

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9780128015322000118

Introduction to the anatomy and physiology of the major aquatic creature species in aquaculture

Frederick S.B. Kibenge , Richard J. Foreign , in Aquaculture Pharmacology, 2021

one.4.8 Reproductive system

The molluscan reproductive organization relies on external fertilization, but with variations ( Cummings and Graf, 2009). Two gonads sit next to the coelom into which they shed ova or sperm. The nephridia extract the gametes from the coelom and emit them into the drapery cavity. Mollusks that use such a system remain of one sex all their lives and rely on external fertilization. Development is indirect, with larva initially as trochopore succeeded past veliger, which somewhen metamorphoses into the developed class. Several species use internal fertilization or are hermaphrodites (e.1000., several snails) functioning as both sexes. Octopuses (Cephalopoda) exhibit direct development, the hatchling is a miniature-similar adult (Villanueva et al., 2016).

Read full chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780128213391000015

Other Marine Fishes

John C. Avise , in Sketches of Nature, 2016

Anecdote or Backdrop

In many freshwater fish species with external fertilization, custodial males build and tend nests into which i or more females deposit eggs, a situation that raises many questions about biological motherhood and paternity in the large cohorts of embryos inside each breed (see Chapters 2 and 4 Chapter 2 Chapter 4 ). Similar questions ascend for the many marine fish species that likewise construct and monitor their nests. Ethologists have long suspected that several sorts of reproductive shenanigans (alternative reproductive tactics by males or females) might muddied the waters about who truly parented whom. Our microsatellite-based parentage analyses have confirmed the merit of such suspicions by documenting, for example, a relatively frequent occurrence of foster parentage in several nest-disposed fish species. This paper provides an example involving marine sticklebacks, for which the genetic data helped to document both fertilization thievery and egg larceny.

Read total chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780128019450000061

Comparative aspects of vertebrate reproduction

David O. Norris PhD , James A. Carr PhD , in Vertebrate Endocrinology (Sixth Edition), 2021

A Oviparity in amphibians

Most anuran amphibians studied are oviparous with external fertilization, although internal fertilization occurs in several species. Breeding in oviparous species is tied closely to a seasonal bicycle involving photoperiod, temperature, availability of moisture, or a combination of these, although a few species are continuous breeders (due east.thou., the Indian frogs Hoplobatrachus (Rana) tigerinus and Hylarana (Rana) erytraea and the Due south American toads Rhinella (Bufo) arenarum and Rhinella (Bufo paracmenis) diptycha). One predominant reproductive design is found in temperate oviparous anurans. Spermatogenesis and ovarian follicular evolution are completed in the autumn, and the animals just "hide" until suitable convenance atmospheric condition occur in the spring. Many oviparous species lay their eggs in temporary or permanent ponds with the eggs developing into free-swimming larvae. Polliwog larvae are the characteristic limbless, fishlike larval forms of anurans and differ markedly from the larvae of urodeles that possess external gills and four limbs at hatching. Anurans have internal gills like fishes and obtain their limbs afterward during metamorphosis. One anuran (Ascaphus spp.) is known to lay its eggs in streams, and the tadpole larvae that result take special modifications to keep from being swept downstream. Some anuran and urodele species lay their eggs on country, usually in moist places such as under logs, in the axils of tree branches, or in temporary miniponds held within the leaves of sure tropical plants. Terrestrial eggs crave considerable parental intendance (meet p 411). Terrestrial eggs that are heavily yolked often develop straight into miniature adults, and no aquatic larval phase exists except as a transitional country within the egg.

Oviparous urodeles showroom several reproductive patterns. In some species (e.g., T. cristatus, Notophthalmus viridescens), the pattern is similar to that of oviparous anurans. In the hellbender Cryptobranchus alleganiensis, spermatogenesis occurs in July shortly before convenance in August and September. Other species such as the mudpuppy (Necturus spp.) transfer sperm to the females in the autumn, and oviposition and fertilization occur the adjacent spring when males are not present. A number of oviparous gymnophionids have been described, all of which lay terrestrial eggs. In Ichthyophis, the eggs are laid in a couch near a stream, and each newly hatched larva must emerge from the burrow and find its fashion to the stream. Gymnophionids mostly produce larger eggs than do the other amphibian groups, and clutch sizes are proportionally smaller.

Read total chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128200933000113

DECAPODA

H.H. HobbsIii, in Ecology and Classification of Northward American Freshwater Invertebrates (Second Edition), 2001

1. Shrimps

Like all astacideans, freshwater shrimps take external fertilization, with the ova being fertilized as they are extruded and then attached to the pleopods of females. The two common epigean, freshwater shrimps, Palaemonetes kadiakensis (Fig. nine) and P. paludosus, have similar life histories, both species living approximately one yr (Fig. xv). Although many individuals reproduce only once (semelparous), Nielsen and Reynolds (1977) observed ovigerous females of P. kadiakensis from Missouri also bearing mature eggs, indicating at least two broods of immature per female (iteroparous); Beck and Cowell (1976) besides noted that P. paludosus spawned twice. The length of the breeding season varies with latitude and is generally longer in southern localities. For instance, ovigerous females occur in populations of P. kadiakensis in Illinois and Michigan from April until August, simply are present in Louisiana populations from February to Oct; ovigerous females of P. paludosus occur throughout the twelvemonth in the Florida Everglades. As a full general rule, breeding does non begin until late spring or early summer in more northern areas. Only big females breed early in the season, and they are replaced by smaller females as the reproductive flavour progresses. Females are larger and unremarkably more abundant than males. Mature (eggbearing) females range from xx–49 mm in full length and produce one or two broods (2 is particularly representative of populations of P. paludosus in Florida where the growing season is longer). The number of eggs produced per female is highly variable, ranging from 8 to 160, with fecundity generally a linear function of full length. The incubation flow depends on water temperature and varies from 12 to 24 days; zoeae larval lengths are approximately four mm at hatching and these free-swimming larvae pass through six stages (varies from 3 to 8) in nigh iii weeks. Accounts of larval development and postembryonic growth in these two species are summarized by Hubschman and Rose (1969), Beck and Cowell (1976), Beck (1980), Kushlan and Kushlan (1980), Page (1985), and Hobbs Three and Jass (1988). Shrimp unremarkably mature when they attain a total length of 20 mm although this is not necessarily the case. Most shrimp die later reproducing, simply some females molt within iii days (generally within 24 h) after young are released and can later produce another brood. Generally, adults disappear from the population in late summertime or early fall, having a life bridge of approximately one year. Marine and brackish water Palaemonetes (e.k., P. intermedius Holthuis, P. pugio Holthuis) ordinarily accept smaller and more numerous eggs per female than practise freshwater species. The product of fewer but larger eggs may enable the freshwater larvae to hatch at an advanced stage with a corresponding reduction in the number of free-swimming larval stages.

FIGURE xv. Generalized life history of Palaemonetes (see text for caption).

Dobkin (1971) described three larval stages in the stygobite, P. cummingi, and studies of atyids consist of observations made on Palaemonias ganteri in Mammoth Cave, Kentucky (Hobbs et al., 1977; Leitheuser et al., 1985); the Alabama cave shrimp, P. alabamae, conducted by Cooper (1975) and McGregor et al. (1997); and Syncaris pacifica (Eng, 1981). The study of the life history of Macrobrachium ohione has not received as much attention every bit have the two taxa of Palaemonetes previously discussed. This species is larger (total length of ovigerous females ranging from 27 to 93 mm) and it lives a maximum of ii years (Fig. xvi). [Huner (1977) determined that G. ohione at Port Allen, Louisiana lived up to two years.] Fecundity is relatively enormous, the number of eggs varying from 6273–24,000 per female (Truesdale and Mermilliod, 1979). Ovigerous females are known only during May in Illinois, from March through September in Louisiana, and during March in Texas. Generally, females are larger than males and merely the largest individuals in the population bear eggs. Additional ecological data can be obtained from Truesdale and Mermilliod (1979), Page (1985), and references therein.

Figure 16. Generalized life history of Macrobrachium ohione (run across text for explanation).

Read full chapter

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/B9780126906479500247

Extracellular Matrix and Egg Coats

Emily E. Killingbeck , Willie J. Swanson , in Current Topics in Developmental Biology, 2018

5.3 Amphibians

Amphibians include anurans (frogs), which reproduce by external fertilization in water, and urodeles (salamanders), which reproduce by internal fertilization in the female cloaca ( Monne et al., 2006; Watanabe & Onitake, 2002). The ~1   μm thick egg glaze of Xenopus laevis is the best studied of the anurans and consists of 5 major ZP glycoproteins that are synthesized past the oocyte: ZP2 (gp69/64), ZP3 (gp43/41), ZP4 (gp37), ZPAX (gp120/112), and ZPD (gp80) (Goudet et al., 2008; Hedrick, 2008; Kubo et al., 1997, 2000, 1999; Lindsay, Wallace, & Hedrick, 2001; Lindsay, Yang, & Hedrick, 2002; Monne et al., 2006; Tian, Gong, & Lennarz, 1999).

Xenopus ZPAX contains a ~600 amino acrid N-terminal region and a short CTP lacking a predicted TM domain and is related to ZP2 with its Type Ii ZP module and absence of a trefoil domain (Monne et al., 2006). In understanding with homology to ZP2, X. tropicalis ZPAX has five boosted ZP-N repeats in its Northward-terminus (Callebaut et al., 2007).

Xenopus ZPD has a simple architecture, consisting of an SP, a ZP module, a CFCS, and a TM domain, and appears to correspond a subfamily of its ain: although its ZP module sequence is most similar to a Type II ZP module, information technology lacks 2 of the 10 conserved cysteines (Lindsay et al., 2002; Monne et al., 2006).

Fertilization in urodels has not been as well studied, with the exception of the newt Cynops pyrrhogaster. C. pyrrhogaster eggs can undergo polyspermy, as no fertilization envelope forms after fertilization (Watanabe & Onitake, 2002). A transcriptome associates from ovary, testis, and oviduct establish homologs to all half dozen ZP subfamilies—ZP1, ZP2, ZP3, ZP4, ZPAX, and ZPD—expressed in the ovaries of C. pyrrhogaster (Watanabe & Takayama-Watanabe, 2014). Notably, the authors found six distinct paralogs of ZP3 (Watanabe & Takayama-Watanabe, 2014).

Read total chapter

URL:

https://www.sciencedirect.com/science/article/pii/S0070215318300486

Sperm Contest in Molluscs

Bruno Baur , in Sperm Competition and Sexual Choice, 1998

A Mating systems

The majority of bivalves are gonochoric, with circulate spawning and external fertilization. Of the approximately ten 000 recent species, virtually 400 are hermaphroditic ( Moore 1969). However, the blazon of sexuality may vary among species belonging to the aforementioned genus and also within populations of the same species (Heller 1993). Occasionally, hermaphroditic individuals accept been found in species that are considered strictly gonochoric (e.g, Mya arenaria; Coe and Turner 1938). For case, hermaphroditic individuals in otherwise predominantly gonochoristic species take been encountered in 30 out of 101 species of the family Unionidae examined (Kat 1983). This suggests that the intensity of sperm contest may vary between populations of the same species.

In virtually gonochoric bivalves, the sex ratio is close to 1:1 (Mackie 1984). In a few species information technology is slightly female biased (reviewed by Mackie 1984). In some species with parasitic dwarf males, the sex ratio is male biased (meet below).

The majority of hermaphroditic bivalves are functional hermaphrodites, producing simultaneously ova and spermatozoa. In these species, self-fertilization may occur under appropriate circumstances (east.thousand. Lasaea subviridis; Ó Foighil 1987). Some species are protandric hermaphrodites (east.thou. Teredo diegensis), other species, although less common, are protogynous hermaphrodites (e.1000. Kellia suborbicularis and Montacuta ferruginosa; Oldfield 1961). In oysters of the genus Ostrea, individuals unremarkably function either as males or females for 1 reproductive flavour (Mackie 1984). The change of sexual activity is repeated, either annually or at closer intervals, leading to a rhythmical alteration between sexes. Alternative sexuality occurs in species with separate sexes, only the gender may or may not exist reversed in the next reproductive season (due east.g. Crassostrea sp.; Andrews 1979). In some protandrous hermaphrodites, a small number of young males never change sex. Factors that influence sex alter in bivalves have been reviewed by Fretter and Graham (1964), Sastry (1979) and Mackie (1984). Patterns of sexual activity change might influence the intensity of sexual pick and sperm competition.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780121005436500337