hey, ive just been surfing youtube and came across a 3-part video on Lake Tanganyika, and about 6min40sec into part2 it shows some shellies that look like these what you are describing with the male being much larger than the female ect.. it shows how they spawn and why he is bigger (which i found quite funny).. it also shows the rival males which are 'transvestite dwarfs' lol.. you have to watch it.. very interesting.
Part1,
Part2 and
Part3
Also, for anyone else interested.. part3 finishes of the story of the 'sly catfish' that was mentioned in another video posted quite abit ago, where the catfish deliberately mixed its own eggs with the cichlids eggs for the cichlids to brood, oblivious to the whole mix-up she does her job and when they hatch the catfish eat the baby cichlids while in the mothers mouth ect, and the narrator also said that the catfish had "won this evolutionary fight'.. but part3 says otherwise and shows how some cichlids have developed ways to 'counter it'.. which i didnt know.
EDIT: ive just noticed there's a
Part4.