Functional morphology of the female reproductive system of a crab with highly extensible seminal receptacles and extreme sperm storage capacity

Abstract

We studied the functional morphology of the female reproductive system of the purple stone crab Danielethus crenulatus. The most remarkable feature is the relative storage capacity and extensibility of the seminal receptacles. These receptacles are a pair of simple sacs that lack internal structures dividing the internal lumen. Differences in seminal receptacle size and contents are accompanied by conspicuous changes in receptacle lining at a tissue level. Full seminal receptacles contain discrete sperm masses formed by hardened fluid and densely packed spermatophores. Different sperm masses are likely from different mates and their stratified disposition within the seminal receptacles is compatible with rival sperm displacement and last sperm precedence. Additionally, the anatomical structure of the vulva and vagina suggest active female control over copula. We discuss our results in the general context of sperm storage in brachyurans and the implications for the mating system of this species.

Integrative depiction of the male reproductive system of the commercial purple crab Homalaspis plana (Platyxanthidae): Structure and function

“…In the paraffin sections of H. plana , these granules were difficult to preserve in the MVD due to a gritty texture and only by using historesin was it possible to preserve this granular secretion. In the closely related platyxanthid D. crenulatus the presence of these granules was also observed, but described as “ovoid gel structure or capsules” (Farias et al, ). These capsules are present in both MVD and PVD of D. crenulatus and spermatophores arrested inside them were described.…”

“…This is the case for the anomuran king crab Lithodes santolla (VSI = 0.05%, Pretterebner, Pardo, & Paschke, ), and the brown crab, Metacarcinus edwardsii (VSI = 0.14%; recalculated from Pardo, Rosas, Fuentes, Riveros, & Chaparro, ). In Danielethus crenulatus (Platyxanthidae), the VSI recorded is only 0.7% (Farias et al, ), however, this estimation for D. crenulatus , is not fully comparable with H. plana because the VSI was estimated including thoracic appendices and was wet weight based.…”

“…This is because the SR reduces its volume gradually after copulation and the oviduct finally opens closer to the vagina connection (ventral position). Farias et al () described in detail the seminal receptacle of another platyxanthid crab, D. crenulatus , from the southern Atlantic. They recorded an extraordinarily large capacity of the SR to store abundant seminal fluid from several ejaculates and classified this as an intermediary‐ventral type.…”

“…However, in the current literature there is a certain bias toward portunid and majoid crabs, especially for the male reproductive system (Beninger, Elner, Foyle, & Odense, ; Diesel, ; Hinsch & Walker, ; Johnson, ; Shinozaki‐Mendes & Lessa, ; Simeó et al, ; Zara et al, ). Despite some recent advances in basal crabs (Garcia Bento et al, ), the Eubrachyura are poorly represented (as Pinnotheridae studied by Becker, Türkay, & Brandis, ; Geryonidae by Melville‐Smith, ; Eriphiidae by Erkan, Tunali, Balkis, & Oliveira, ; Ocypodidae Castilho, Ostrensky, Pie, & Boeger, ) or only briefly described (e.g., Platyxanthidae by Farias, Spivak, & Luppi, ).…”

Ejaculate allocation in Brachyura: What do males of Metacarcinus edwardsii respond to?

“…The explanation could be associated with the multiple functions of the seminal fluids beyond their nutritional or antimicrobial contributions to increase the survival of gametes (Subramoniam 1993). Seminal receptacles are extensible organs, where individual ejaculates are stored in discrete packages that are progressively displaced towards the blind end, forming an ejaculate stratification pattern (Sainte-Marie et al 2000, Jensen & Bentzen 2012, Pardo et al 2013, Antunes et al 2016, Farias et al 2017. The ejaculates are separated by seminal fluid layers (also called seminal gel) deposited by the last male to avoid sperm mixing and to improve the probability of fertilization.…”