New data concerning postembryonic development in Antarctic Ammothea species (Pycnogonida: Ammotheidae)

Abstract

In this paper, new data on larval and postlarval stages after newly collected and museum-deposited material of six Ammothea species is provided and compared with previously known information. Different developmental stages attached to the ovigerous legs of adult males for each species were found: four stages [protonymphon (Ptn), postlarval instar 1 (PL-1), postlarval instar 2 (PL-2), and postlarval instar 3 (PL-3)] for A. carolinensis; just one (Ptn) for A. clausi and A. minor; three stages (Ptn, PL-1, PL-2) for A. bicorniculata and A. spinosa; and other three (Ptn, PL-2, PL-3) for A. longispina. In the present contribution, the external morphology of each larval and postlarval instar is described, illustrated, and discussed. The larval and postlarval development of Ammothea bicorniculata, A. carolinensis, A. longispina, and A. spinosa is characterized by (1) the eggs hatch as a protonymphon larva; (2) the larvae and subsequent postlarval stages have yolk reserves and a relatively large size (0.5–0.85 mm in length for the protonymphon); (3) the postlarvae remain on the ovigerous legs of males during several moults; (4) the spinning spine is absent; and (5) the development of walking legs is sequential. The protonymphon larva of A. clausi and A. minor is the only stage on the ovigerous legs of males, and this stage is characterized by: (1) there is no yolk reserve and it has a relatively small size (0.22–0.3 mm in length); (2) the spinning spine is present; and (3) all larval appendages have a relatively large size.