Ecological relations between mangrove leaf litter and the spatial distribution of the gastropod Melampus coffeus in a fringe mangrove forest

Abstract

ABSTRACT. Leaf litter represents a food source to many organisms that may directly contribute to organic matter decomposition. In addition, the physical presence of these vegetal detritus contributes for the modification of some environmental areas and produce microhabitats that may act as a refuge against predators and desiccation for many animals. The pulmonate gastropod Melampus coffeus (Linnaeus, 1758) (Ellobiidae) is a very common specie in Atlantic Coast mangrove forests and feeds on fallen mangrove leaves. It was hypothesized that the spatial distribution of Melampus coffeus is directly affected by mangrove leaf litter biomass deposition. Thus, this research aimed at evaluating the spatial distribution of these gastropods in relation to the biomass of mangrove leaf litter through a twelve-month period. The study area was established in the middle estuary of Pacoti River, state of Ceará, Brazil where two adjacent zones with different topographic profiles were determined. Samples of Melampus coffeus and leaf litter were collected monthly, throughout a year, from the mangrove ground surface. The results indicated that the presence of twigs in mangrove litter favor the occupation by smaller individuals of M. coffeus, probably because smaller individuals are more susceptible to predator attacks and desiccation than larger ones, and twigs and branches may provide a safe microhabitat.KEYWORDS. Ellobiidae, macrodetritivore, microhabitat, Pacoti river, Rhizophora mangle. RESUMO. Relações ecológicas entre a serrapilheira de manguezal e a distribuição espacial do gastrópodo Melampus coffeus em uma borda de floresta de mangue.A serapilheira representa fonte de alimentos para diversos organismos que podem contribuir diretamente para a decomposição de matéria orgânica. A presença física desses detritos vegetais pode modificar áreas do ambiente e promover a formação de microhabitats, servindo de refúgio para diversos animais contra predadores e dessecação. O gastrópode Melampus coffeus (Linnaeus, 1758) (Ellobiidae) é comum em florestas de mangue na costa do Atlântico e se alimenta de folhas de mangue caídas. Nesse trabalho foi assumida a hipótese de que a distribuição espacial do Melampus coffeus é diretamente afetada pela deposição de serapilheira no manguezal. Objetivou-se avaliar a distribuição espacial desses gastrópodes em relação à serapilheira de mangue durante doze meses de coletas. A área de estudo foi estabelecida no médio estuário do rio Pacoti, Estado do Ceará, Brasil onde foram determinadas duas zonas de diferentes perfis topográficos. Amostras de Melampus coffeus e de serapilheira foram coletadas mensalmente. Os resultados indicaram que a presença de galhos na superfície do solo do manguezal favorece a ocupação do ambiente por indivíduos dessa espécie de molusco de menor tamanho, provavelmente porque indivíduos menores são mais suscetíveis ao ataque de predadores e à dessecação e a presença de galhos pode formar microhabitats mais seguros.

Gastropod Density and Diversity in the Mangrove Forest of Pagatan Besar Village, Tanah Laut Regency, Indonesia

“…Organic material which is basically a source of food for Gastropods comes from parts of plants that fall in the forest or are carried by ocean / river currents and then accumulate in the mangrove forest. Leaves are an organic material favored by gastropods Melampus coffeus because they contain little lignocellulose (Tavares et al, 2015). Gastropod abundance is positively affected by the content of organic matter in sediments.…”

“…In aquatic and terrestrial ecosystems, Gastropods are known as food for ecinoderms, fish, birds and mammals (Pawar and Al-Tawaha, 2017). On the other hand, they play a role of mechanically breaking down (decomposition) organic matter, such as leaves through their feeding activities (Kabir et al, 2014;Tavares et al, 2015). Some gastropod are even of economic value to the community.…”

Gastropod Diversity in Mangrove Forests of Mojo Village, Ulujami District, Pemalang Regency, Indonesia

“…Some gastropod species are also identified as mangrove litter feeder (Tavares et al, 2015), while some others are filter feeders (Khade and Mane, 2012). Thus, the gastropod community has significant role in the nutrient cycle.…”

ผลผลิตขั้นปฐมภูมิสุทธิและการบริโภคซากใบไม้โดยกลุ่มหอยฝาเดียวในแปลงปลูกป่าชายเลนที่มีอายุแตกต่างกัน

“…การกิ นซากใบไม้ โดยหอยฝาเดี ยวทำให้ เกิ ดส่ งผ่ านคาร์ บอนจากผู ้ ผลิ ตไปสู ่ ผู ้ บริ โภคลำดั บถั ดไป โดยตรงประมาณ 46.2% (Wu et al, 2020) โดยแหล่ งอาหารของหอยฝาเดี ยวที ่ กิ นซากใบไม้ ได้ แก่ ซากใบไม้ ที ่ สะสมบนพื ้ นป่ า โดยผลการศึ กษาครั ้ งนี ้ พบว่ าการสะสมซากใบไม้ บนพื ้ นป่ ามี ความแตกต่ าง ระหว่ างแปลงอย่ างมี นั ยสำคั ญทั ้ งฤดู แล้ งและฤดู ฝน โดยแปลง (Proffitt & Devlin, 2005;Tavares et al, 2015) และการศึ กษาในป่ าชายเลน Rhizophora ที ่ รายงานว่ าหอยฝาเดี ยว Terebralia palustris ที ่ มี ขนาดมากกว่ า 13 มม. สามารถกิ นซากใบไม้ ได้ ประมาณ 0.65 กรั ม/ตั ว และยั งสามารถหาซากใบไม้ กิ นได้ ขณะที ่ น้ ำทะเลท่ วมถึ ง (Fratini et al, 2004) (Kristensen et al, 2008;Pradisty et al, 2021) แปลง Y1 ที ่ มี อายุ มากที ่ สุ ดมี อั ตราการย่ อยสลายซากใบไม้ (leaf decomposition rate, k) 0.00 0.00 0.00 0.00 0.00 0.00 3 0.00 0.00 0.00 0.00 0.00 0.00 4 8.55 20.01 1.63 0.00 0.00 6.03 5 0.29 0.00 11.79 0.00 0.00 0.00 Y5 1 0.00 0.00 0.00 0.00 0.00 0.00 2 0.00 0.00 0.00 0.00 0.00 0.00 3 7.02 0.91 0.00 -0.38 0.00 4 2.83 ---10.50 0.00 5 0.00 0.00 0.00 2.41 0.00 0.00 Y7 1 17.15 18.05 0.00 0.00 0.00 0.65 2 0.00 0.00 0.00 20.77 2.94 0.00 3 0.00 --0.00 0.00 0.00 4 0.00 0.00 0.00 0.00 0.00 0.00 5 13.61 1.63 0.00 0.00 0.00 0.00 Y9 1 0.00 0.00 -0.45 0.00 0.00 2 22.27 12.09 0.00 0.00 0.00 0.54 3 0.00 8.13 2.82 0.00 0.00 4.11 4 0.00 0.34 -2.17 0.00 0.00 5 0.85 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.77 -22.27 0.94 2 0.00 0.00 0.00 6.04 14.17 2.06 3 -0.00 -27.17 9.98 7.99 4 0.00 0.00 -21.08 15.39 15.24 5 7.33 0.00 0.25 -10.12 14.79 Y5 1 0.00 0.00 0.00 0.00 21.43 0.85 2 0.00 0.00 0.00 54.57 7.47 1.91 3 0.79 0.00 0.00 -26.99 35.89 4 12.11 0.00 0.00 12.07 0.00 0.00 5 0.00 0.00 0.00 10.10 12.93 8.78 Y7 1 0.00 0.00 0.00 0.00 0.00 23.97 2 -0.00 0.00 0.00 0.00 7.65 3 0.00 0.00 0.00 31.70 34.93 0.00 4 0.00 0.00 0.00 11.08 0.00 1.47 5 0.00 0.00 0.00 0.00 5.36 7.27 Y9 1 0.00 0.00 0.00 0.00 2.28 0.00 2 -0.00 0.00 3.87 0.00 0.00 3 -0.00 0.00 0.00 21.40 0.00 4 0.00 0.00 0.00 -0.00 3.02 5 0.00 0.00 0.00 56.06 0.00 0.00 0.00 0.00 0.00 -0.00 0.00 2 2.78 0.00 1.26 0.46 0.00 0.00 3 0.00 0.00 0.00 0.00 0.00 0.00 4 -0.00 1.71 13.78 0.00 0.00 5 0.00 0.00 0.00 0.00 4.50 0.00 Y5 1 0.00 0.00 0.00 2.41 0.00 0.00 2 0.00 --0.00 0.00 0.00 3 0.73 0.00 0.00 0.04 0.00 0.00 4 0.00 0.00 0.00 3.16 0.00 0.35 5 -0.00 0.00 7.87 0.00 0.00 Y7 1 0.00 0.00 0.56 0.00 0.00 0.00 2 1.03 -0.00 0.00 0.00 0.00 3 -0.00 0.00 9.30 0.00 0.00 4 -0.00 4.73 4.00 0.00 0.99 5 -0.00 5.96 8.07 0.00 0.00 Y9 1 0.00 0.00 0.00 0.00 0.00 0.00 2 0.00 0.00 1.12 10.52 1.61 0.00 3 0.00 0.00 0.00 0.00 0.00 0.00 4 0.00 0.00 0.00 9.21 2.04 0.00 5 1.90 0.00 0.00 0.00 7.93 0.00…”