External Morphology of Spermatozoa and Spermatozeugmata of the Freshwater Mussel Truncilla truncata (Mollusca: Bivalvia: Unionidae)

Waller, Diane L.; Lasee, Becky A.

doi:10.2307/2426669

Cited by 23 publications

(7 citation statements)

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“…The high fertilisation success observed in gravid females even at low male density supports the idea that relatively few spermatozeugmata are required to fertilise an entire brood. An average brood of L. straminea (about 150 000 ova) could be fertilised completely by about 25 spermatozeugmata (assuming 6000 sperm/ spermatozeugmata; see Barnhart & Roberts, 1997;Waller & Lasee, 1997). Despite the high fertilisation success we observed in most treatments, our results support the possibility of sperm limitation and resulting Allee effects in some situations.…”

Section: Discussionsupporting

confidence: 57%

Section: Discussionmentioning

confidence: 97%

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Egg fertilisation in a freshwater mussel: effects of distance, flow and male density

Mosley

Haag²,

Stoeckel

2014

Freshwater Biology

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Summary Small or sparse populations can experience Allee effects if egg fertilisation is reduced because of a shortage of sperm. Freshwater mussels are spermcasters that often occur as sparse, patchy populations. Previous studies suggested that sperm shortage limits these populations unless facultative hermaphroditism and self‐fertilisation occur at low density. We conducted experiments in ponds to examine fertilisation in the mussel, Lampsilis straminea, in response to flow, presence of and distance from males, male density, and the presence of upstream females that could compete for sperm with downstream females. Self‐fertilisation in the absence of males did not occur in either experiment. Female fertilisation success was uniformly high in most treatments and was not related to flow or distance from males (1–25 m). Fertilisation success was significantly lower at low male density (0.02 m−2, compared with 0.16 m−2) but remained relatively high even in most low male density treatments. The proportion of females that became gravid was higher in the presence of upstream females, but fecundity was significantly lower when upstream females were present; these conflicting results made it difficult to assess the role of competition among females for sperm. Overall, high fertilisation success occurred at densities three orders of magnitude lower than previously proposed thresholds for mussels. Sperm dispersal and acquisition and egg fertilisation appear to be complex processes associated with adaptations for spermcasting. These adaptations are likely to facilitate persistence at low population density and buffer mussels from reproductive Allee effects.

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Section: Discussionsupporting

confidence: 57%

Section: Discussionmentioning

confidence: 97%

Egg fertilisation in a freshwater mussel: effects of distance, flow and male density

Mosley

Haag²,

Stoeckel

2014

Freshwater Biology

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“…For example, in oyster, the eggs usually remain close to motionless females at a significant distance from males [40]. Males of freshwater bivalve unionids release the spermatozeugmata into the water as spherical aggregations of 8000 -9000 spermatozoa with their heads turned to the center of the sphere [41]. In the bryozoan Membranipora membranacea, the colonies eject into seawater individual eggs and spermatozeugmata containing 32 -64 spermatozoa [4].…”

Section: Discussionmentioning

confidence: 99%

Morphology of Gametes and Insemination in the Vestimentiferan Riftia pachyptila

Дроздов¹,

Galkin²

2012

OJMS

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Ultrastructure of gametes (sperm and eggs) of vestimentiferan tubeworms and external-internal insemination by means of spermatozeugmata in Riftia pachyptila were described. The spermatozoa of Riftia are threadlike, about 130 μm long, and have a diameter of about 0.7 μm, narrowing to 0.2 μm in the apical portion of the macrodome, and pointed at the end of the tail. Oocytes are produced by the ovaries at the first meiotic prophase stage. The early oocytes are small, hardly exceeding 10 μm in diameter, spherical cells with a poorly differentiated cytoplasm and large nuclei with a nucleolus. Completely formed oocytes reaching up to 130 μm in diameter leave the ovary, their germinal vesicle is unresorbed and has a nucleolus. They are coated by a yolk membrane of 1.2 μm. The eggs enter the oviduct, move along, and accumulate in its expanded anterior portion, the ovisack. The sperm is released in seawater as sperm packages, each having the shape of a torch. Then sperm moves to females and sperm packages at the posterior end of the oviduct surrounding of eggs. Inside the female tube, spermatozoa and, possibly, yet unsplit sperm packages, invade the oviducts through genital openings, where the unfertilized eggs are already present in the terminal portion of the eggsack

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“…), similarly might provide additional energy reserves to prolong dispersal/swimming time. Finally, if intact or partially intact spermatozeugmata successfully reach an egg‐brooding chamber, many more ova are likely to be fertilized (Waller & Lasee ).…”

Section: Discussionmentioning

confidence: 99%

Spermcasting of spermatozeugmata by the bivalvesNutricola confusaandN. tantilla

2011

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The dynamics and consequences of the varied reproductive modes of marine invertebrates is a rich and vibrant field of inquiry for ecological and evolutionary studies. One mode of reproduction that is not as well-studied as others is "spermcasting" or "spermcast mating," when males broadcast sperm and females retain eggs and brood developing embryonic stages. This type of reproduction occurs in two small (maximum adult shell length~5-6 mm) venerid bivalves, Nutricola confusa and N. tantilla, that live in protected bays of the temperate eastern Pacific. Females of these species brood developing embryos in chambers formed by the inner demibranchs, and release fully formed juveniles. We discovered that upon exposing clams to fluvoxamine, a selective serotonin reuptake inhibitor, males release spermatozeugmata, clusters of sperm cells attached by their heads to a central core. Spermatozoa of Nutricola have unusually long, needle-shaped heads that are approximately one quarter of the total length of the cell. These heads are curled and "packaged" into the hemispherical-shaped cores of spermatozeugmata. The cores are about one-third as long as the heads, and the tails protrude out of the opposite side of the cap of the core. The spermatozeugmata display two different swimming patterns, one where the tails beat in synchrony, and the other where they do not. The size of the cores is not significantly different in the two species, but spermatozeugmata of N. tantilla have significantly longer and wider tails than those of N. confusa. Advantages to spermcasting spermatozeugmata instead of individual spermatozoa may include enhanced dispersal and increased probabilities of fertilization. One consequence of spermatozeugmata (rather than individual spermatozoa) entering female brood chambers might be lowering of the effective population size. For species like these, which lack pelagic larvae, spermatozeugmata could increase dispersal and gene flow.

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External Morphology of Spermatozoa and Spermatozeugmata of the Freshwater Mussel Truncilla truncata (Mollusca: Bivalvia: Unionidae)

Cited by 23 publications

References 4 publications

Egg fertilisation in a freshwater mussel: effects of distance, flow and male density

Egg fertilisation in a freshwater mussel: effects of distance, flow and male density

Morphology of Gametes and Insemination in the Vestimentiferan <i>Riftia pachyptila</i>

Spermcasting of spermatozeugmata by the bivalvesNutricola confusaandN. tantilla

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External Morphology of Spermatozoa and Spermatozeugmata of the Freshwater Mussel Truncilla truncata (Mollusca: Bivalvia: Unionidae)

Cited by 23 publications

References 4 publications

Egg fertilisation in a freshwater mussel: effects of distance, flow and male density

Egg fertilisation in a freshwater mussel: effects of distance, flow and male density

Morphology of Gametes and Insemination in the Vestimentiferan &lt;i&gt;Riftia pachyptila&lt;/i&gt;

Spermcasting of spermatozeugmata by the bivalvesNutricola confusaandN. tantilla

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Morphology of Gametes and Insemination in the Vestimentiferan <i>Riftia pachyptila</i>