black dot

Mate selection & copulation

  Mate selection & copulation are dealt with in this section, while topics of EGG-LAYING, EMBRYONIC DEVELOPMENT, HATCHING & LARVAL LIFE, SETTLEMENT & METAMORPHOSIS, and ONTOGENETIC DEVELOPMENT OF BEHAVIOUR are considered elsewhere.
  black dot


  This section on mate-selection & copulation is arranged alphabetically by genus. The genus Alderia is considered here, while AEOLIDIA , HERMISSENDA, NAVANAX & OTHER CEPHALASPIDS, and APLYSIA & OTHER ANASPIDS are considered in their own sections.
  black dot
Research study 1

drawings of two ascoglossans Alderia modesta about to stab one another with their stylets in a coplulatory actA study at Scripps Institution of Oceanography, La Jolla, California assesses the effects of body size on mating patterns and egg production in Alderia modesta, an hermaphroditic ascoglossan with hypodermic insemination. Rather than employing a soft, extensible penis for transfer of sperm into the gonopore of a reciprocal partner as in other opisthobranchs, Alderia uses a penis tipped with a sharp stylet to stab into the body wall of its partner.  The author’s research hypothesis stems from the idea that in sperm-storing simultaneous hermaphrodites, the smaller of a copulating pair will invest proportionately more of its resources in functioning as a male than will a larger one. However, does this hold true for a species that lacks a definitive sperm-storage organ?  Results show, firstly, that all parts of the body are capable of receiving sperm leading to egg fertilisation.  As predicted, smaller individuals inseminate larger mates for a significantly longer time than vice versa (on average, by 55sec).  Sperm production, moreover, begins at a smaller size and age than egg production.  At the time of this paper’s publication, the mechanism of how the sperm travel to the eggs is unknown. The author comments that this is the first study on allocation of sexual roles in an hermaphrodite with hypodermic insemination.  Angeloni 2003 Anim Behav 66: 417.

NOTE  based on the information given in Research Study 2 below, it is likely that this species from southern California is A. willowi.  In fact, the author describes the condition of poecilogony, which is a characteristic of A. willowi

  black dot

The author reviews ideas regarding possible advantages of hypodermic insemination in hermaphrodites, and these are presented below.  Think about them and try to identify the single disadvantage to the sperm donor.  Then CLICK HERE for explanations.

It reduces or eliminates courtship time. 

The sperm recipient may receive sperm without its consent. 

It leads to an escalation in sperm competition. 

A controlled reciprocal exchange of sperm is lacking. 

  black dot
Research study 2

photograph of ascoglossan Alderia willowi showing sperm deposit.  Photo courtesy Patrick Krug, CSU Los Angeles, CaliforniaWest coast species of plant-sucking ascoglossans such as Alderia willowi, an indigenous species occurring south of Bodega Harbor, California, and A. modesta, a cosmopolitan species occurring from San Francisco Bay northwards, have the same method of hypodermic insemination. Note in the photograph on the Right the subcutaneous sperm deposit in a recently inseminated A. willowi.  Sperm can be stored for several weeks and site of injection has no effect on fertilisation success.  Krug 2007 Amer Malac Bull 23: 99. Photographs courtesy Patrick Krug, California State University, Los Angeles KrugLab.
NOTE  in earlier papers the author and co-workers believed this new species to be Alderia modesta. Alderia willowi is poecilogonous, that is, has different developmental modes within the same brood.  One of these involves small planktotrophic larvae that spend 30d or so in the photograph of ascoglossan Alderia modesta attempting to mate with Alderia willowi.  Photo courtesy Patrick Krug, CSU Los Angeles, Californiaplankton before becoming competent to metamorphose; the other, comprising about 15-30% of the brood, involves larger lecithotrophic larvae that metamorphose within 2d of hatching.  The mode of copulation in A. modesta is not known

NOTE  ever useful, Wikipedia notes that the species name willowi derives from the author's grandmother's name and from the fictional character Willow Rosenberg in Buffy the Vampire Slayer

An interspecific and unsuccessful copulatory event involves penis-probing
by Alderia modesta on A. willowi. Note the more typical green coloration
of A. willowi here as compared with the other photograph above 10X

  black dot
Research study 3

histogram comparing egg production in ascoglossans Alderia willowi under conditions of cross-fertilisation, self-fertilisation, and non-fertilisationA follow-up study by the above research group reveals that, if kept in isolation, individuals of Alderia willowi will at first lay unfertile eggs but, within a few days, will begin to self-fertilise.  Hypodermic insemination, whether between individuals or self-inflicted, is potentially traumatic, and the question arises as to its costs as measured in reduced fecundity.  Laboratory studies in which egg production is measured in normal cross-fertilising pairs, self-fertilising individuals, and non-fertilising individuals show, indeed, that costs are not trivial.  Note in the histogram that egg production per individual per day is significantly less for pairs and self-fertilising individuals than for individuals producing unfertile eggs.  However, numbers of egg clutches produced per week do not differ significantly among the 3 groups, nor does the allocation to lecithotrophic or planktotrophic (poecilogony) mode differ.  The authors hypothesise that the costs of hypodermic insemination owe to energy that must be reallocated from egg production to repair of tissue damage inflicted by the penis.  The study offers the first estimate of mating costs in an hermaphrodite with hypdodermic insemination.  Smolensky et al. 2009 Biol Bull 216: 188.

NOTE  stock animals are collected at Newport, California and experiments done at California State University, Los Angeles.  The stock animals are cultured in the laboratory to reproductively mature individuals of the next generation, and these “virgins” used in subsequent experiments.  Laboratory animals are raised on Vaucheria longicaulis

  black dot