Geosesarma notophorum
Geosesarma notophorum:
Geosesarma notophorum Ng & Tan, 1995 is a terrestrial brachyuran crab described from Palu Lingga island east of Sumatra in Indonesia (Ng & Tan, 1995). G. notophorum is named for its novel brooding behavior where the female carries freshly hatched young crabs on the dorsal surface of her carapace for two to three days after hatching. This was the first time this behavior was reported for any brachyuran crab, more will be written on this phenomenon below. G. notophorum also has completed abbreviated development where the eggs hatch directly into first instar crabs without any larval development.
Geosesarma notophorum’s color is visually described with the carapace being pale-brown to publish-brown additionally with sometimes bright blue flecks of color; the posterior ½ of the carapace is noticeably more vibrant than the anterior half. The C-shaped gastric groove is pronounced and is usually maroon in color and the eyes contrast all other parts of the body being iridescent bright green. There is some variation in eye color from bright yellow-green to bright yellow. Contrastingly, the chelae are a bright red.
When first hatching Geosesarma notophorum are initially red but within a few molts turn mottled brown and do not obtain the characteristic eye color till reaching a carapace size of 1cm or more but color is less vibrant than adults, and then juveniles remain beige-brown until reaching closet to adult size and lack the bright red chelae as well.
Size of Geosesarma notophorum
The holotype male was 9.0 x 8.6mm found between 1000-1300 m above sea level and the largest paratype female from the same location was 8.8 x 8.0mm. Another holotype male from a slightly different location was 9.4 x 8.8mm and a female at 10.8 x 10.3mm. From measurements it can be noted that the carapace is diagnosed squarish being only slightly wider than long in both sexes.
Habitat of Geosesarma notophorum
No detailed habitat information was given other than “G. notophorum is completely terrestrial like other members of the genus, although the substrate is usually moist or swampy” (Ng & Tan, 1995, p. 394).
Novel Brooding Behavior of Geosesarma notophorum
As described by Ng & Tan (1998) Geosesarma notophorum females carry between eight to twelve eggs on her abdomen and those eggs hatch out as a fully developed crab. Ovigerous females, meaning egg bearing, were observed without exception carrying the freshly hatched crabs on the dorsal surface of their carapaces. The hatched crabs crawled from the abdomen to the branchiostegite region via the base of the legs and then situated themselves in that region for a time before crawling onto the dorsal surface of the female carapace. During this time off direct crab-bearing the female congregates under moist surfaces and refrains from eating for the duration of the crab-bearing phenomenon. Fresh crabs are fairly inactive but become more active over the course of the few days until at which the female may place them on the substrate with her chelae.
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References:
Padilla, P. (2022). Geosesarma notophorum. Species Banner. Permission granted soley to TGD.
WoRMS (2022). Geosesarma notophorum Ng & Tan, 1995. Accessed at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=444547 on 2022-11-20
Ng, P, K, L., & Tan, C, G, S. (1995). Geosesarma notophorum sp. Nov. (Decapoda, Brachyura, Grapsidae, Sesarminae), a Terrestrail Crab from Sumatra, with Novel Brooding Behavior. Crustaceana, 68(3), 390-395. https://www.jstor.org/stable/20105055