Sexual dimorphism in Tripedaliidae (Conant 1897) (Cnidaria, Cubozoa, Carybdeida)

Abstract

The family Tripedaliidae was re-defined and expanded based on a molecular phylogenetic hypothesis by Bentlage et al. (2010, Proceedings of the Royal Society Biological Science, 277: 497). Additionally, Bentlage et al. (2010) proposed that all members of the family Tripedaliidae present dimorphism in gonads and have structures that function as seminal vesicles (at least in males). Until now, no information on Tripedalia binata concerning gonad morphology, sexual dimorphism, spermatophore formation or structures that serve as seminal vesicles or spermathecae were published. We studied mature medusae of both sexes of Tripedalia cystophora, Tripedalia binata and Copula sivickisi in order to compare these structures in their stomach regions. We found sexual dimorphism and spermatophore formation in seminal vesicle-like structures in all three species. In particular, we show that along with the females of Copula sivickisi, the females of Tripedalia cystophora and Tripedalia binata also possess structures that store spermatophores and serve as spermathecae.The results are in agreement with the morphological synapomorphies for Tripedaliidae outlined in Bentlage et al. (2010), but suggest an adjustment of the diagnosis of Tripedaliidae (underlined): All carybdeids that display sexual dimorphism of the gonads, produce spermatophores and in which males and females possess subgastral sacs, pockets or purses which function as seminal vesicles or spermathecae.

Gonadal cnidocytes in the cubozoan Tripedalia cystophora Conant, 1897 (Cnidaria: Cubozoa)

“…Our results show that the male gonads of T. cystophora and C. sivickisi are similar corroborating previous results (Straehler‐Pohl, Garm, & Morandini, ). In both cases, the sperm matures in chamber‐like structures of the gonads and at any given time less than half the sperm cells are mature.…”

“…It has also been suggested that the isorhizas are used to anchor the spermatozeugmata to the female tentacles during mating (Garcia‐Rodriguez et al, ), but these hypotheses are not mutually exclusive. Only ripe sperm cells are included in the spermatozeugmata leaving the immature sperm behind in the hemi‐gonad and each hemi‐gonads can thus form several spermatozeugmata over time (present work, Straehler‐Pohl et al, ; Garcia‐Rodriguez et al, ). This strongly suggests that even though the female of T. cystophora only mates once (Werner, ), the male can have multiple matings like seen for C. sivickisi (Lewis & Long, ).…”

Sex, polyps, and medusae: Determination and maintenance of sex in cnidarians

“…Findings thus far suggest that the vast majority of staurozoans, cubozoans, and scyphozoans are gonochoristic (i.e., polyps give rise to medusae of a single sex) (Fig. B) (Berrill, ; Arai, ; Morandini and Da Silveira, ; Straehler‐Pohl et al, ), although sequential hermaphroditism has been reported in the scyphozoan Chrysaora hyoscella (Berrill, ).…”

<i>Carybdea morandinii</i>—New investigations on its life cycle reveal its true genus: <i>Carybdea morandinii</i> Straehler-Pohl & Jarms, 2011 becomes <i>Alatina morandinii</i> (Straehler-Pohl & Jarms, 2011)

“…Campbell (1974: 142) stated that gonads in most cnidarians are not separate organs, as found in higher animals, because germ cells are generally found in the interstitial portions of the body tissue which, prior to the formation of germ cells, exhibit no reproductive specialization. However, we follow Campbell (1974), Marques & Collins (2004), Bentlage et al (2010), Morandini & Marques (2010) and Straehler-Pohl et al (2014) in using the term gonad to refer to areas where gametes are formed.…”