The Ultrastructure of the Spermatozoon of Dromidiopsis-Edwardsi Rathbun, 1919 (Crustacea, Brachyura, Dromiidae) - Confirmation of a Dromiid Sperm Type

Abstract

The dromiid spermatozoon, as exemplified by Dromidiopsis edwardsi, Stimdromia (=Petalomera) lateralis and Dromidia antillensis, accords with that of the Homolidae and differs markedly from spermatozoa of other crabs (the raninid-heterotreme-thoracotreme assemblage) in the discoidal form of the acrosome and the capitate form of the perforatorium. Dromiids differ from homolids in the greater depression of the acrosome and the form of the head of the perforatorium, thus exhibiting a distinctive dromiid sperm type. The head is bilaterally prolonged in D. edwardsi and also shows bilateral symmetry, though this is less pronounced in S. lateralis. In homolids the head of the perforatorium has the form of a horizontally disposed spiked wheel. Centrioles are unknown in dromiid sperm but are present in homolids. Nuclear arms in D. edwardsi, as in homolids, have the form of three small radial vertices. Dromiids, homolids, raninids, higher heterotremes and thoracotremes differ (homoplasically?) from lower heterotremes in lacking microtubules in the nuclear arms. Dromiid sperm lack the posterior median process of the nucleus seen in homolids, anomurans and lower heterotremes. The sperm of D. edwardsi differs from other investigated dromiid sperm in the asymmetrical location of the opercular perforation relative to the longitudinal axis of the sperm, and in more complex zonation of the acrosome vesicle. The acrosome is deeply embedded in the nucleus in D. edwardsi whereas in S. lateralis it is superficial on the nucleus. Both have an apical protuberance of subopercular material through the opercular perforation, known elsewhere only in dynomenid crabs. Sperm structure in the Dromiidae thus differs significantly from that in the Eubrachyura.

Relationships of the Cyclodorippoidea Ortmann: evidence from spermatozoal ultrastructure in the generaXeinostoma, TymolusandCymonomus(Crustacea, Decapoda)

“…The mean ratios of length to width of the acrosome of 0.54-0.63 overlap with mean ratios in raninoids which range from 0.53 in Lyreidus brevipons Sakai, 1937, to 0.76 in Ranina ranina (Lime, 1758) (see Jamieson, 1989) and 0.68-0.72 in Raninoides sp. and is greater than the 0.26 and 0.34 in the dromiids Petalomera lateralis Gray, 183 1, now Stirndromia lateralis (see McLay , 1993;Jamieson, 1990) and Dromidiopsis edwarhi Rathbun, 1919 (Jamieson et al, 1993) or 0.35 in the dynomenid Paradynomene tuberculata Sakai, 1963(Jamieson et al, 1993a. Other species with mean lengthwidth ratios lying within the lower limit for raninoids are the homolids Homola sp.…”

Multivariate Analysis: A Useful Tool in Separating Spermatophores Produced by the Diogenids, Clibanarius Erythropus, Diogenes Pugilator, and Calcinus Tubularis (Decapoda, Anomura, Diogenidae)

“…In the most recent investigations dealing with the spermatophore morphometry of hermit crabs (Jamieson & Tudge, 1990;Tudge & Jamieson, 1991Jamieson et al, 1993Jamieson et al, , 1997Tudge, 1996Tudge, , 1997aTudge, , b, 1999Tudge et al, 1998aTudge et al, , 1999Tudge et al, , 2001, usually one or two crabs for each species were used and 4-12 spermatophores were measured (sampling defined as representative by Tudge et al, 1998a), but Scelzo et al (2004) measured larger samples. Such small numbers do not permit the use of multivariate analysis.…”

The ultrastructure of the spermatozoon ofParadynomene tuberculata Sakai, 1963 (Crustacea, Brachyura, Dynomenidae): Synapomorphies with dromiid sperm

“…It is unknown in other crabs, being distinct from the apical button of thoracotreme sperm. Homology with the subopercular zone of other brachyurans is uncertain (Jamieson et al, 1993). Apical perforation of the operculum occurs also in dromiids and homolids and also in raninoids, cyclodorippoids and * Now Stimdromia lateralis (Gray, 1831) lower (e.g.…”

“…The operculum is interrupted, centrally, by a hiatus; (2) moderately dense material protrudes from below the operculum through the perforation as an apically rounded cone. The layer of which the protuberance is an extension is here termed the subopercular zone, though homology with a zone of the same name in other brachyurans is uncertain (Jamieson et al, 1993). The subopercular zone directly overhes the capitate expansion of the perforatorium.…”

“…Studies of spermatozoal ultrastructure have revealed a distinctive sperm type for each of the families Dromiidae (Brown, 1966;Jamieson, 1990Jamieson, , 1991Jamieson et al, 1993) and Homohdae (Guinot et al, 1993). Homohds differ in the "spiked wheel" form of the head of the perforatorium, contrasting with the smooth outline and bilateral symmetry of that of dromiids.…”